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  • 1985-1989  (3,485)
  • 1980-1984  (2,251)
  • 1975-1979  (1,448)
  • Biochemistry and Biotechnology  (5,692)
  • Ultrastructure  (1,492)
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Keywords
  • 101
    Electronic Resource
    Electronic Resource
    The structure of aconitase (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 289-312 
    Details
    ISSN: 0887-3585
    Keywords: aconitase ; iron-sulfur enzyme ; crystal structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The crystal structure of the 80,000 Da Fe—S enzyme aconitase has been solved and refined at 2.1 Å resolution. The protein contains four domains; the first three from the N-terminus are closely associated around the [3Fe-4S] cluster with all three cysteine ligands to the cluster being provided by the third domain. Associationof the larger C-terminal domain with the first three domains createsan extensive cleft leading to the Fe—S cluster. Residues from all four domains contribute to the active site region, which is defined by the Fe—S cluster and a bound SO42-ion. This region of the structure contains 4 Arg, 3 His, 3 Ser, 2 Asp, 1 Glu, 3 Asn, and 1 Gln residues, as well asseveral bound water molecules. Three of these side chains reside on a threeturn 310 helix in the first domain. The SO42-ion is bound 9.3 Å from the center of the [3Fe-4S] cluster by the side chains of 2 Arg and 1 Gln rsidues. Each of 3 His side chains in the putative active site is paired with Asp or Glu side chains.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340050406
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  • 102
    Electronic Resource
    Electronic Resource
    Masthead (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989) 
    Details
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060101
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  • 103
    Electronic Resource
    Electronic Resource
    Masthead (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989) 
    Details
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060201
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  • 104
    Electronic Resource
    Electronic Resource
    An NMR-based molecular dynamics simulation of the interaction of the lac repressor headpiece and its operator in aqueous solution (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 104-127 
    Details
    ISSN: 0887-3585
    Keywords: lac repressor; lac operator ; lac headpiece-operator complex ; protein-DNA specificity ; molecular dynamics ; computer simulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The results of a 125 psec molecular dynamics simulation of a lac headpiece-operator complex in aqueous solution are reported. The complexsatisfies essentially all experimental distance information derived from two-dimensional nuclear magnetic resonance (2-D-NMR) studies. The interaction between lac repressor headpiece and its operator based on many direct- and water-mediated hydrogenbonds and nonpolar contacts which allow the formation of a tight complex. Nostable hydrogen bonds between side chains and bases and found, while specific contacts occur between both nonpolar groups and, to a lesserextent, through water-mediated hydrogen bonds. The simulated complex structure in water is intrinsically stable without application of nuclear Overhauser effect (NOE) distance restraints, while being compatible with most of the available biochemical, genetic, andchemically induced dynamic nuclear polarization (CIDNP) data.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060203
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  • 105
    Electronic Resource
    Electronic Resource
    Engineering subtilisin BPN′ for site-specific proteolysis (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 240-248 
    Details
    ISSN: 0887-3585
    Keywords: substrate-assisted catalysis ; serine protease ; fusion proteins ; site-directed mutagenesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A combination of protein engineering and substrate optimization was used to create variants of the serine protease, subtilisin BPN′, which efficiently and specifically cleave a designed target sequence in a fusion protein. The broad substrate specificity of wildtype subtilisin BPN′ is greatly restricted by substitution of the catalytic histidine 64 with alanine (H64A) so that certain histidine-containing substrates are preferentially hydrolysed (Carter, P., Wells, J. A. Science 237:394-399, 1987). The catalytic efficiency, (kcat/Km), of this H64A variant was increased almost 20-fold by judicious choice of substrate and by installing three additional mutations which increase the activity of wild-type subtilisin. The most favorable substrate sequence identified was introduced as a linker in a fusion protein between a synthetic IgG binding domain of Staphylococcus aureus protein A and Escherichia coli alkaline phosphatase. The fusion protein (affinity purified on an IgG column) was cleaved by the prototype H64A enzyme and its improved variant, efficiently and exclusively at the target site, to liberate an alkaline phosphatase product of the expected size and N-terminal sequence. Several features of H64A variants of subtilisin make them attractive for site-specific proteolysis of fusion proteins: they have exquisite substrate specificity on the N-terminal side of the cleavage site and yet are broadly specific on the C-terminal side; they can be produced in large quantities and remain highly active even in the presence of detergents, reductants (modest concentrations), protease inhibitors, at high temperatures, or when specifically immobilized on a solid support.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060306
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  • 106
    Electronic Resource
    Electronic Resource
    The interaction of calmodulin with fluorescent and photoreactive model peptides: Evidence for a short interdomain separation (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 284-293 
    Details
    ISSN: 0887-3585
    Keywords: calmodulin ; peptides ; fluorescence spectroscopy ; photoaffinity labeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Calmodulin is known to bind target enzymes and basic, amphiphilic peptides in a Ca2+-dependent manner. Recently, we introduced a photoaffinity label, p-benzoylphenylalanine (Bpa), into the sequence of a model, α-helical, calmodulin-binding peptide. When the Bpa residue was introduced at the third position of the peptide, Met-144 on the C-terminal domain of calmodulin was labeled, whereas when the photolabel was placed at the thirteenth position, Met-71 on the N-terminal do main was labeled. Assuming that both peptides bind in similar orientations, these results are not consistent with the crystal structure of calmodulin, in which the domains are held at a significant distance from one another by a long α-helical segment. To test the assumption that both peptides bind in similar orientations, we have synthesized a calmodulin-binding peptide with the photolabel in both the third and the thirteenth positions. Upon photolysis, this peptide forms a cross-link between Met-71 and Met 124 on the N- and C-terminal domains, respectively. Furthermore, a peptide with a Bpa in the thirteenth position and a Trp residue in the third position was also synthsized. After photocross-linking the Bpa redidue of this peptide to Met-71 of calmodulin, it could be shown that the fluorescence properties of the Trp residue were consistent with its side chain being buried in a hydrophobic pocket on the C-terminal domain of calmodulin. These data indicate that, when complexed with basic, amphiphi peptides, calmodulin can adopt a conformation in which its two domains are significantly closer than in the crystal sturcture of the uncommplexed protein.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060311
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  • 107
    Electronic Resource
    Electronic Resource
    Ras interaction with the GTPase-activating protein (GAP) (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 306-315 
    Details
    ISSN: 0887-3585
    Keywords: oncogene ; GTP-binding protein ; cancer ; S. cerevisiae adenylyl cyclase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Biologically active forms of Ras complexed to GTP can bind to the GTP ase-activating protein (GAP), which has been implicated as a possible target of Ras in mammalian cells. In order to study the structural features of Ras required for this interaction, we have evaluated a series of mutant ras proteins for the ability to bind GAP and a series of Ras peptides for the ability to interfere with this interaction. Point mutations in the putative effector region of Ras (residues 32-40) that inhibit biological activity also impair Ras binding to GAP. An apparent exception is the Thr to Ser substitution at residue 35; [Ser-35]Ras binds to GAP as effectively as wild-type Ras even though this mutant is biologically weak in both mammalian and S. cerevisiae cells. In vitro, [Ser-35]Ras can also efficiently stimulate the S. cerevisiae target of Ras adenylyl cyclase, indicating that other factors may influence Ras/protein interactions in vivo. Peptides having Ras residues 17-44 and 17-32 competed with the binding of RAS to E. coli-expressed GAP with IC50 values of 2.4 and 0.9 μM, respectively, whereas Ras peptide 17-26 was without effect up to 400 μM. A related peptide from the yeast GTP-binding protein YPT1 analogous to Ras peptide 17-32 competed with an IC50 value of 19 μM even though the YPT1 protein itself is unable to bind to GAP. These results suggest that determinants within Ras peptide 17-32 may be important for Ras binding to GAP.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060313
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  • 108
    Electronic Resource
    Electronic Resource
    Three-dimensional structure of the neurotoxin ATX Ia from Anemonia sulcata in aqueous solution determined by nuclear magnetic resonance spectroscopy (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 357-371 
    Details
    ISSN: 0887-3585
    Keywords: sea anemone toxin ; NMR ; distance geometry ; restrained energy minimization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: With the aid of 1H nuclear magnetic resonance (NMR) spectroscopy, the three-dimensional structure in aqueous solution was determined for ATX Ia, which is a 46 residue polypeptide neurotoxin of the sea anemone Anemonia sulcata. The input for the structure calculations consisted of 263 distance constraints from nuclear Overhauser effects (NOE) and 76 vicinal coupling constants. For the structure calculation several new or ammended programs were used in a revised strategy consisting of five successive computational steps. First, the program HABAS was used for a complete search of all backbone and χ1 conformations that are compatible with the intraresidual and sequential NMR constraints. Second, using the program DISMAN, we extended this approach to pentapeptides by extensive sapling of al conformations that are consistent with the local and medium-range NMR constraints. Both steps resulted in the definition of additional dihedral angle constraints and in stereospecific assignments for a number of β-methylene groups. In the next two steps DISMAN was used to obtain a group of eight conformers that contain no significant residual violations of the NMR constraints or van der Waals contacts. Finally, these structures were subjected to restrained energy refinement with a modified version of the molecular mechanics module of AMBER, which in addition to the energy force field includes potentials for the NOCE distance constraints and the dihedral angle constraints. The average of the pairwise minimal RMS distances between the resulting refined conformers calculated for the well defined molecular core, which contains the backbone atoms of 35 residues and 20 interior side chains, is 1.5 ± 0.3 Å. This core is formed by a four-stranded β-sheet connected by two well-defined loops, and there is an additional flexible loop consisting of the eleven residues 8-18. The core of the protein is stabilized by three disulfide bridges, which are surrounded by hydrophobic residues and shielded on one side by hydrophilic residues.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060403
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  • 109
    Electronic Resource
    Electronic Resource
    Acid-induced dimerization of skeletal troponin C (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 424-430 
    Details
    ISSN: 0887-3585
    Keywords: ultracentrifugation ; calcium-binding proteins ; fluorescence resonance energy transfer ; pH effect ; hydrophobic interactions ; troponin C dimer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have investigated pH-dependent changes of the properties of troponin C from rabbit skeletal muscle. At pH 7.5 this protein is a monomer and at pH 5.2 it is a dimer. In contrast, bovine cardiac troponin C remains essentially monomeric at pH 5.2. Bovine brain calmodulin is not a dimer, but significantly aggregated at the same acidic pH. The dimerization of skeletal troponin C was demonstrated by low-speed (16,000 rpm) sedimentation equilibrium measurements carried out at 20°C and by polyacrylamide gel electrophoresis under nondenaturing conditions. Dimer formation was significantly inhibited in the ultracentrifuge at rotor speeds of 30,000 and 40,000 rpm at 20°C, and was completely prevented at a rotor speed of 40,000 rpm and 4°C. This temperature and pressure dependence of dimerization strongly suggests that hydrophobic bonding is a major factor in promoting skeletal troponin C association at pH 5.2. The intramolecular distance between Met-25 and Cys-98 of rabbit skeletal troponin C deduced from fluorescence resonance energy transfer measurements increased by a factor of two upon lowering the pH from 7.5 to 5.2, indicating a pH-dependent transition in which the protein changed from a relatively compact conformation to an elongated conformation. The protein-induced increase in the energy transfer distance is related to the acid-induced dimerization of the protein. The extended conformation observed at pH 5.2 is compatible with the dumbbell-shaped structure of skeletal troponin C crystals obtained from turkey at pH 5.0 [Herzberg, O., James, M. N. G. Nature (London) 313:653-659, 1985] and chicken at pH 5.1 (Sundaralingam, M., Bergstrome, R., Strasburg, G., Rao, S. T., Roychowdhury, P., Greaser, M., Wang, B. C. Science 227:945-948, 1985). However, the conformation in neural solution deviates form that predicted by crystallography. Intermolecular interactions leading to dimer formation likely play an important role in promoting the extended conformation that exists at acidic pH.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060409
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  • 110
    Electronic Resource
    Electronic Resource
    Masthead (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989) 
    Details
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340050101
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  • 111
    Electronic Resource
    Electronic Resource
    Treatment of electrostatic effects in macromolecular modeling (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 78-92 
    Details
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340050109
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  • 112
    Electronic Resource
    Electronic Resource
    Prediction of the conformation of ice-nucleation protein by conformational energy calculation (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 47-65 
    Details
    ISSN: 0887-3585
    Keywords: crystal growth ; helical conformation ; repetitive octapeptide ; icelike molecular surface ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The active conformation of an icenucleation protein, whose major portion consists of a long polypeptide segment of nearly repetitive octapeptides, is predicted by the analyses of conformational energy and the mechanism of crystal growth. The protein ideally has an exact octapeptide repetition and is assumed to have a helical conformation. The present study searched for low-energy helical conformations and each of the obtained low-energy conformations examined as to whether it has a surface structure that can promote crystal formation. Two conformations obtained were good candidates for an ice nucleus. Both were found to have on their surfaces an arrangement of hydrogen-bonding sites, which fits well with those of hydrogen bonds in hexagonal ice crystal. Further, one of the two conformations had a hexagonal conformational symmetry consistent with the hexagonal ice crystal structure. The other conformation had apentagonal conformational symmetry that could enable the growth of an ice crystal-dendritic polycrystalline snow crystal-which grows on metastable cubic ice.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340050107
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  • 113
    Electronic Resource
    Electronic Resource
    Electrostatic interactions in the assembly of Escherichia coli aspartate transcarbamylase (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 66-77 
    Details
    ISSN: 0887-3585
    Keywords: subunit interactions ; allosteric regulation ; solvent accessibility ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Although ionizable groups are known to play important roles in the assembly, catalytic, and regulatory mechanisms of Escherichia coli aspartate transcarbamylase, these groups have not been characterized in detail. We report the application of static accessibility modified Tanford-Kirkwood theory to model electrostatic effects associated with the assembly of pair of chains, subunits, and the holoenzyme. All of the interchain interfaces except R1-R6 are stabilized by electrostatic interactions by -2 to -4 kcal-m-1 at pH 8. The pH dependence of the electrostatic component of the free energy of stabilization of intrasubunit contacts (C1-C2 and R1-R6) is qualitatively different from that of intersubunit contacts (C1-C4, C1-R1, and C1-R4). This difference may allow the transmission of information across subunit interfaces to be selectively regulated. Groups whose calculated pK or charge changes as a result of protein-protein interactions have been identified and the results correlated with available information about their function. Both the 240s loop of the c chain and the region near the Zn(II) ion of the r chain contain clusters of ionizable groups whose calculated pK values change by relatively large amounts upon assembly. These pK changes in turn extend to regions of the protein remote from the interface. The possibility that networks of ionizable groups are involved in transmitting information between binding sites is suggested.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340050108
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  • 114
    Electronic Resource
    Electronic Resource
    Secondary structural analysis of retrovirus integrase: Characterization by circular dichroism and empirical prediction methods (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 156-165 
    Details
    ISSN: 0887-3585
    Keywords: retrovirus integrase ; circular dichroism ; homologous proteins ; secondary structural predictions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The retrovirus integrase (IN) protein is essentialfor integration of viral DNA into host DNA. The secondary structure of thepurified IN protein from avian myeloblastosis virus was investigated by bothcircular dichroism (CD) spectroscopy and five empirical prediction methods. The secondary structures determined from the resolving of CD spectra through a least-squares curve fitting procedure were compared with those predicted from four statistical methods, e.g., the Chou-Fasman, arnier-Osguthorpe-Robson, Nishikawa-Ooi, and a JOINT scheme which combined all three of these methods, plus a pure a priori one, the Ptitsyn-Finkelstein method. Among all of the methods used, the Nishikawa-Ooiprediction gave the closest match in the composition of secondary structureto the CD result, although the other methods each correctly predictedoneor more secondary structural group. Most of the α-helix and β-sheet states predicted by the Ptitsyn-Finkelstein methodwere in accord with the Nishikawa-Ooi method. Secondary structural predictions by the Nishikawa-Ooi method were extended further toinclude IN proteins from four phylogenetic distinct retroviruses. The structuralrelationships between the four most conserved amino acid blocks of these IN proteins were compared using sequence homology and secondary structure predictions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340050210
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  • 115
    Electronic Resource
    Electronic Resource
    Structural basis of hierarchical multiple substates of a protein. IV: Rearrangements in atom packing and local deformations (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 125-131 
    Details
    ISSN: 0887-3585
    Keywords: protein conformation ; dynamics ; Monte Carlo simulation ; conformational energy ; minimization ; plastic deformation ; conformational heterogeneity ; hierarchy in dynamics ; trypsin inhibitor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Differences in atom packing are studied in the minimum energy conformations derived from the record of the Monte Carlo simulation of conformational fluctuation in the native state of a globular protein, bovine pancreatic trypsin inhibitor. It is found that local deformations observed among the minima which are found in the previous paper are accompanied by rearrangement of atom packing. Spatial locations of the local deformations in the three-dimensional folded structure are also studied. It is foundthat the local deformations are distributed in space in several clusters inthe folded structure. The size and location of the clusters characterize the respective fluctuations of the first and the second levels observed in the simulation. In the fluctuations of the first level local deformations, each of which usually involves a few side chains and one main chain local segment, are thermally exited independently of each other near thesurface of the molecule. The observed fluctuation of the second level involves a cooperative deformation involving many side chains and local main chain segments all in one cluster, which goes though the core of the molecule. The collective local deformations observed both in the first and second levels are plastic in the sense that they are accompanied with rearrangement of atom packing.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340050206
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  • 116
    Electronic Resource
    Electronic Resource
    Structural basis of hierarchical multiple substates of a protein. V: Nonlocal deformations (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 132-138 
    Details
    ISSN: 0887-3585
    Keywords: protein conformation ; dynamics ; Monte Carlo simulation ; conformational energy ; minimization ; hierarchy in dynamics ; conformational heterogeneity ; flexibility ; trypsin inhibitor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Distances between centers of gravity of individual residues are compared among the minimum energy conformations derived from the recordof the Monte Carlo simulation of conformational fluctuations in the native state of a globular protein, bovine pancreatic trypsin inhibitor. It is found that local deformations originating from the multiplicity of localconformations cause deformations of the whole structure of the molecule in various ways, which can be classified into two types. Type 1:When a local deformation occurs in a region consisting of a few residues near the surfaceof the molecule, the whole shape of the molecule responds by deforming elastically. The magnitude of this deformation is in the range of thermalfluctuations calculated by the harmonic approximation around a singleminimum. Type 2: We have observed one case belonging to the second type in which local deformations occur cooperatively in an extended region. This regiongoes across the whole molecule and divide the remaining parts into two. Atom packing changes in and around the extended region of local deformations. For this reason deformation in this region is plastic. Relative locationand orientation between the divided two parts change very much. Deformationof the whole shape in this case, associated with the plastic deformationin an extended region, demonstrates that protein molecules have a flexibility beyond the harmonic limit.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340050207
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  • 117
    Electronic Resource
    Electronic Resource
    Second virial coefficient of α-crystallin (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 166-169 
    Details
    ISSN: 0887-3585
    Keywords: α-crystallin ; enthalpy ; entropy of solution ; light scattering ; second virial coefficient ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Light scattering studies were performed on bovine α-crystallin measuring the scattering intensities as a function of scattering angle, concentration, and temperature. The data yielded the molecular weight, radius of gyration, and second virial coefficient of α-crystallin at different temperatures. The second virial coefficient increased with increasing temperature. Both the enthalpy and entropy of solution of α-crystallin are positive. The Flory thetatemperature was found to be 271 K.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340050211
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  • 118
    Electronic Resource
    Electronic Resource
    Three-dimensional structure of a fluorescein-Fab complex crystallized in 2-methyl-2,4-pentanediol (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 271-280 
    Details
    ISSN: 0887-3585
    Keywords: antifluorescyl monoclonal antibody ; high-affinity binding site ; effects of MPD on hapten binding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The crystal structure of a fluorescein-Fab (4-4-20) complex was determined at 2.7 Å resolution by molecularreplacement methods. The starting model was the refined 2.7 Å structure of unliganded Fab from an autoantibody (BV04-01) with specificity for single-stranded DNA. In the 4-4-20 complex fluorescein fits tightly into a relatively deep slot formed by a network of tryptophan and tyrosine side chains. The planar xanthonyl ring of the hapten is accommodated at the bottom of the slot while the phenylcarboxyl group interfaces with solvent. Tyrosine 37 (light chain) and tryptophan 33 (heavy chain) flank the xanthonyl group and tryptophan 101 (light chain) provides the floor of the combining site. Tyrosine 103 (heavy chain) is situated near the phenyl ring of the hapten and tyrosine 102 (heavy chain) forms part of the boundary of the slot. Histidine 31 and arginine 39 of the light chain are located in positions adjacent to the two enolic groups at opposite ends of the xanthonyl ring, and thus account for neutralization of one of two negative charges in the haptenic dianion. Formation of an enol-arginine ion pair in a region of low dielectric constant may account for an incremental increase in affinity of 2-3 orders of magnitude in the 4-4-20 molecules relative to other members of an idiotypic family of monoclonalantifluorescyl antibodies. The phenyl carboxyl group of fluorescein appearsto be hydrogen bonded to the phenolic hydroxyl group of tyrosine 37 of the light chain. A molecule of 2-methyl-2,4-pentanediol (MPD), trapped in the interface of the variable domainsjust below the fluorescein binding site, may be partly responsible for the decrease in affinity for the hapten in MPD.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340050404
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  • 119
    Electronic Resource
    Electronic Resource
    A 3D building blocks approach to analyzing and predicting structure of proteins (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 355-373 
    Details
    ISSN: 0887-3585
    Keywords: protein ; structure ; prediction ; primary ; secondary ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A new approach is introduced for analyzing and ultimately predicting protein structures, defined at the level of Cα coordinates. We analyze hexamers (oligopeptides of six amino acid residues) and show that their structure tends to concentrate in specific clusters rather than vary continuously. Thus, we can use a limited set ofstandard structural building blocks taken from these clusters as representatives of the repertoire of observed hexamers. We demonstrate that protein structures can be approximated by concatenating such building blocks. We have identified about 100 building blocks by applying clustering algorithms, and have shown that they can “replace” about 76% ofall hexamers in well-refined known proteins with an error of less than 1 Å, and can be joined together to cover 99% of the residues. After replacing each hexamer by a standard building block with similar conformation, we can approximately reconstruct the actual structure by smoothly joining the overlapping building blocks into a full protein. The reconstructed structures show, in most cases, high resemblance to the original structure, although using a limited number of building blocks and local criteria of concatenating them is not likely to produce a very precise global match. Since these building blocks reflect, in many cases, some sequence dependency, it may be possible to use the results of this study as a basis for a protein structure prediction procedure.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340050410
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    Molecular dynamics simulations of ribonuclease T1: Comparison of the free enzyme and 2′ GMP-enzyme complex (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 20-31 
    Details
    ISSN: 0887-3585
    Keywords: ribonuclease ; active site ; conformational change ; protein-nucleic ; acid interactions ; fluorescence depolarization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Molecular dynamics simulations were performed on free RNase T1 and the 2′GMP-RNase T1 complex in vacuum and with water in the active site along with crystallographically identified waters, allowing analysis of both active site and overall structural and dynamics changes due to the presence of 2′GMP. Difference in the active site include a closing in the presence of 2′GMP, which is accompanied by a decrease in mobility of active site residues. The functional relevance of the active site fluctuations is discussed. 2′GMP alters the motion of Tyr-45, suggesting a role for that residue in providing a hydrophobic environment for the protein-nucleic acid interactions responsible for the specificity of RNase T1. The presence of 2′GMP causes a structural change of the C-terminus of the α-helix, indicating the transmission of structural changes from the active site through the protein matrix. Overall fluctuations of both the free and 2′GMP enzyme forms are in good agreement with X-ray temperature factors. The motion of Trp-59 is influenced by 2′GMP, indicating difference in enzyme dynamics away from the active site, with the calculated changes following those previously seen in time-resolved fluorescence experiments.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340060103
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    The molten globule state as a clue for understanding the folding and cooperativity of globular-protein structure (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 87-103 
    Details
    ISSN: 0887-3585
    Keywords: molten globule state ; protein folding ; protein denaturation ; structural intermediate ; activated state of folding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340060202
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    Alternate succession of steps can lead to the folding of a multidomain oligomeric protein (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 395-404 
    Details
    ISSN: 0887-3585
    Keywords: folding pathway ; tryptophan synthase ; acid denaturation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The β2 subunit of Escherichia coli tryptophan synthase can be either unfolded in 6 M guanidine, or extensively denatured at acidic pH. These two denatured form of β2 have different circular dichroism spectra and thus correspond to distinct physical states. Here we compare the folding pathways of these two different denatured forms of β chains. We describe the kinetics of regain of a variety of physical, functional, ad immunochemical signals characteristic of six successive steps previously identified on the folding pathway of guanidine unfolded β2. It is shown that whereas identical molecular events over with the same kinetics, the two folding pathways are different, and involve different structural intermediates.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340060406
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    Use of restrained molecular dynamics in water to determine three-dimensional protein structure: Prediction of the three-dimensional structure of Ecballium elaterium trypsin inhibitor II (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 405-417 
    Details
    ISSN: 0887-3585
    Keywords: protein tertiary structure ; incorrect and correct folding ; molecular surfaces ; solvation free energy ; solution and crystal structure ; disulfide connectivity determination ; squash inhibitor family ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Refinement of distance geometry (DG) structures of EETI-II (Heitz et al.:Biochemistry 28:2392-2398, 1989), a member of the squash family trypsin inhibitor, have been carried out by restrained molecular dynamics (RMD) in water. The resulting models show better side chain apolar/polar surface ratio and estimated solvation free energy than structures refined “in cacuo.” The consistent lower values of residual NMR constraint violations, apolar/polar surface ration and solvation free energy of one of these refined structures allowed prediction of the 3D folding and disulfide connectivity of EETI-II. Except for the few first residues for which no NMR constraints were available, this computer model fully agree with X-ray structures of CMTI-I (Boe et al.: FEBS Lett. 242:285-292, 1989) and EETI-II complexed with trypsin that appeared after the RMD simulation was completed. Restrained molecular dynamics n water is thus proved to highly valuable for refinement of DG structures Also, the successful use of apolar/polar surface ratio and solvation free energy reinforce the analysis of Novotny et al. (Proteins 4: 19-30, 1988) and shows that these criteria are useful indicators of correct versus misfolded models.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340060407
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    Structure and thermal stability of monomeric bacteriorhodopsin in mixed pospholipid/detergent micelles (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 38-46 
    Details
    ISSN: 0887-3585
    Keywords: reconstitution ; membrane protein folding/unfolding ; pH effects ; differential scanning calorimetry ; circular dichroism ; electron microscopy ; HPLC ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Thermal unfolding experiments on bacteriorhodopsin in mixed Phospholipid/detergent micelles were performed. Bacteriorhodopsin was extracted from the purple membrane in a denatured state and then renatured in the micellar system. The purpose of this study was to compare the changes, if any, in the structure and stability of a membrane protein that has folded in a nonnative environment with results obtained on the native system, i.e., the purple membrane. The purple membrane crystalline lattice is an added factor that may influence the structural stability of bacteriorhodopsin. Micelles containing bacteriorhodopsin are uniformly sized disks 105 ± 13 Å in diameter (by electron microscopy) and have an estimated molecular mass of 210 kDa (by gel filtration HPLC). The near-UV CD spectra (which is indicative of tertiary structure) for micellar bacteriorhodopsin and the purple membrane are very similar. In the visible CD region of retinal absorption, the double band seen in the spectrum of the purple membrane is replaced with a broad positive band for micellar bacteriorhodopsin, indicating that in micelles, bacteriorhodopsin is monomeric. The plot of denaturational temperature vs. pH for micellar bacteriorhodopsin is displaced downward on the temperature axis, illustrating the lower thermal stability of micellar bacteriorhodopsin when compared to the purple membrane at the same pH. Even though micellar bacteriorhodopsin is less stable, similar changes in response to pH and temperature are seen in the visible absorption spectra of micellar bacteriorhodopsin and the purple membrane. This demonstrates that changes in the protonation state or temperature have a similar affect on the local environment of the chromophore and the protein conformation. We conclude that the tertiary structure of the bacteriorhodopsin monomer is essentially the same in micelles and the purple membrane. On the other hand, in the synthetic mixed micelle system, the packing between the nonnative amphiphiles and bacteriorhodopsin is probably not optimal, protein-protein interactions have been lost, and thehelical packing may be looser because the crystalline lattice is absent. Itis likely that a combination of these effects leads to the decreased stability of micellar bacteriorhodopsin.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340050106
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    Thermitase, a thermostable subtilisin: Comparison of predicted and experimental structures and the molecular cause of thermostability (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 22-37 
    Details
    ISSN: 0887-3585
    Keywords: sequence homology ; tertiary structure prediction ; molecular dynamics ; energy minimization ; hydrophobic interactions ; aromatic ring-ring interactions ; salt bridges ; calcium binding ; thermoactinomyces vulgaris ; extracellular protease ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The Subtilisin family of proteases has four members of known sequence and structure: subtilisin Carlsberg, Subtilisin novo, proteinase K, and thermitase. Using thermitase as a test case, we ask two questions. How good are methods for model building a three-dimensional structure of a protein based on sequence homology to a known structure? And what are the molecular causes of thermostability? First, we compare predicted models of thermitase, refined by energy minimization and varied by molecular dynamics, with the preliminary crystal structure. The predictions work best in the conserve structural core and less well in seven loop regions involving insertions and deletions relative to Subtilisin. Here, variation of loop regions by molecular dynamics simulation in vacuo followed by energy minimization does not improve the prediction since we find no correlation between in vacuo energy and correctness of structure when comparing local energy minima. Second, in order to identify the molecular case of thermostability we confront hypotheses erived by calculation of the details of interatomic interactions with inactivation experiments. As a result, we can exclude salt bridges and hydrophobic interactions as main cause of thermostability. Based on a combination of theoretical and experimental evidence, the unusually tight binding of calcium by thermitase emerges as the most likely single influence responsible for its increased thermostability.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340050105
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    The crystal structure of the ternary complex of staphylococcal nuclease, Ca2+ and the inhibitor pdTp, refined at 1.65 Å (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 183-201 
    Details
    ISSN: 0887-3585
    Keywords: crystallographic refinement ; restrained least-squares refinement ; Konnert-Hendrickson refinement ; phosphodiesterase ; protein structure ; enzyme mechanism ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The structure of a complex of staphylococcal nuclease with Ca2+ and deoxythymidine 3′,5′-biophosphate (pdTp) has been refined by stereochemically restrained leastsquares minimization to a crystallographic R value of 0.161 at Å resolution. The estimated root-mean-square (rms) error in the coordinates in 0.16 Å. The final model comprises 1082 protein atoms, onecalcium ion, the pdTp molecule, and 82 protein atoms, onecalcium ion, the pdTp molecule, and 82 solvent water molecules;it displays an rms deviation from ideality of 0.017 Å for bond distances and 1.8° for bond angles.The mean distance between corresponding α carbons in the refined and unrefined structures is 0.6 Å we observe small but significant differences between the refined and unrefined models in the turn between residues 27 and 30, the loop between residues 44 and 50, the first helix, and the extended strand between residues 112 and 117 which forms part of the active site binding pocket.The details of the calcium liganding and solvent structure in the activesite are clearly shown in the final electron density map. The structure ofthe catalytic site is consistent with mechanism that has been proposed for this enzyme. However, we note that two lysines from a symmetry-related molecule in the crystal lattice may play an important role in determining the geometry of inhibitor binding, and that only one of the two required calcium ions is observed in the crystal structure; thus, caution is advised in extrapolating from the structure of the complex of enzyme and inhibitor to that enzyme and substrate.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340050302
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    Masthead (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989) 
    Details
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340050301
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    Size determination of multienzyme complexes using two-dimensional agarose gel electrophoresis (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 224-232 
    Details
    ISSN: 0887-3585
    Keywords: effective pore's radius ; α-ketoglutarate dehydrogenase complex ; branched chain α-keto acid dehydrogenase complex ; electron microscopy ; multienzyme complex ; two-dimensional ; electrophoresis ; multienzyme complex ; aggregation of Pyruvate dehydrogenase complex ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In the studies of the size and structure of multienzyme complexes, a procedure complementary to electron microscopy for determining the molecular dimensions of hydrated multisubunit complexes is needed. For some applications this procedure must be capable of detecting aggregation of complexes and must be applicable to impure preparations. In the present study, a procedure of two-dimensional agarose gel electrophoresis (2d-AGE) (Serwer, P. et al. Anal. Biochem. 152: 339-345, 1986) was modified and employed to provide accurate sizemeasurements of several classical multienzyme complexes. To improve band clarity and to achieve required gel pore sizes, a hydroxyethylated agarose was used. The effective pore's radius (PE) as a function of gel concentration was determined for this agarose inthe range of PE value needed for multienzyme complexes (effective radius, R = 10-30 nm). Appropriate conditions wereestablished to measure R value ± 1% of the pyruvate (PDC), α-ketoglutarate (α-KGDC), and the branched chain α-keto acid (BCDC) dehydrogenase multienzyme complexes; the accuracy of R was limited by the accuracy of the determinations of the R value for the sizestandards. The PDC from bovine heart was found to have an R = 22.4 ± 0.2 nm following cross-linking with glutaraldehyde that was necessary for stabilization of the complex. Dimers and trimers of PDC, present in the preparations used, were separated from monomeric PDCduring 2d-AGE. All R values for the enzyme complexes studied were agreement with, though more accurate than, R valuesobtained by use of electron microscopy. In contrast to this statement, the internal dihydrolipoyl transacetylase core of PDC (E2) had an R of 18.8 ± 0.2 nm using 2d-AGE, but 10.5 nm by electron microscopy. This observation confirms the proposal that the core of the PDC has externally projecting fibrous domains invisibleto electron microscopy.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340050306
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    The pro-peptide is not necessary for active renin secretion from transfected mammalian cells (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 259-265 
    Details
    ISSN: 0887-3585
    Keywords: cDNA expression ; deletion mutagenesis ; zymogen activation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Cultured mouse myeloma cells were transfected with expression vectors encoding the aspartyl proteinase, human renin. The full construct, encoding the renin precursor prorenin, allows transfected cellsto secrete the enzymically inactive pro-protein. Activity is detectable only following trypsin treatment which mimics the physiological activation step. Accordingly, it appears that myeloma cells do not contain detectable levels of an appropriate activating proteinase. However, when these cells are transfected with a construct from which the pro-peptide coding sequence has been deleted, they secrete an apparently fully active enzyme which is indistinguishable from mature renin. We conclude that expression of the pro-peptide is not necessary to allow correct folding of the molecule and its passage through the secretory pathway.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340050402
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    A protein structural motif that bends DNA (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 281-288 
    Details
    ISSN: 0887-3585
    Keywords: Hu protein ; integration host factor ; transcription factor 1 ; DNA bending protein ; protein structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The prokaryotic protein HU, integration host factor (IHF) from Escherichia coli and transcription factor 1 (TF1) from bacteriophage SPO1 are closely related molecules. Biochemical results suggest that the role of these proteins is to bind and bend DNA. From the high-resolution structure of HU, we propose a model for thisinteraction with DNA. Crucial amino acid differences between the proteins can be rationalized in terms of their different specific functions.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340050405
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    Evolution of CuZn superoxide dismutase and the Greek Key β-barrel structural motif (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 322-336 
    Details
    ISSN: 0887-3585
    Keywords: sequence conservation ; exon ; gene duplication ; protein folding ; structure-function ; X-ray structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Detailed analysis of the CuZn superoxide dismutase (SOD) structure provides new results concerning the significance and molecular basis for sequence conservation, intron-exon boundary locations, gene duplication, and Greek key β-barrel evolution. Using 15 aligned sequences, including a new mouse sequence, specific roles have been assigned to all 23 invariant residues and additional residues exhibiting functional equivalence. Sequence invariance is dominated by 15 residues that form the active site stereochemistry, supporting a primary biological function of uperoxide dismutation. The β-strands have no sequence insertions and deletions, whereas insertions occur within the loops connecting the β-strands and at both termini. Thus, the β-barrel with only four invariant residues is apparently over determined, but dependent on multiple cooperative side chain interactions. The regions encoded by exon I, a proposed nucleation site for protein folding, and exon III, the Zn loop involved in stability and catalysis, are the major structural subdomains not included in the internal twofold axis of symmetry passing near the catalytic Cu ion. This provides strong confirmatory evidence for gene evolution by duplication and fusion followed by the addition of these two exons. The proposed evolutionary pathway explains the structural versatility ofthe Greek key β-barrel through functional specialization and subdomain insertions in new loop connections, and provides a rationale for the size of the present day enzyme.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340050408
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    Structural analysis of antiviral agents that interact with the capsid of human rhinoviruses (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 1-19 
    Details
    ISSN: 0887-3585
    Keywords: virus crystallography ; molecular dynamics ; hydrophobic pockets ; antiviral agents ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: X-Ray diffraction data have been obtained for nine related antiviral agents (“WIN compounds”) while bound to human rhinovirus 14 (HRV14).These compounds can inhibit both viral attachment to host cells and uncoating. To calculate interpretable electron density maps it was necessary to account for (1) the low (∼60percnt;) occupancies of these compounds in the crystal, (2) the large (up to 7.9 Å) conformational changes induced at the attachment site, and (3) the incomplete diffraction data. Application of a density difference map technique, which exploits the 20-fold noncrystallographic redundancy in HRV14, resulted in clear images of the HRV14:WIN complexes. A real-space refinement procedure was used to fit atomic models to these maps.The binding site of WIN compounds in HRV14 is a hydrophobic pocket composed mainly from residues that form the β-barrel of VP1. Among rhinoviruses, the residues associated with the binding pocket are far more conserved than external residues and are mostly contained within regular secondary structural elements. Molecular dynamics simulations of three HRV14:WIN complexes suggest that portions of the WIN compounds and viral protein near the entrance of the binding pocket are more flexible than portions deeper within the β-barrel.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340060102
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    Describing protein structure: A general algorithm yielding complete helicoidal parameters and a unique overall axis (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 46-60 
    Details
    ISSN: 0887-3585
    Keywords: macromolecular conformation ; protein folding ; helical axis ; secondary structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We present a general and mathematically rigorous algorithm which allows the helicoidal structure of a protein to be calculated starting from the atomic coordinated of its peptide backbone. This algorithm yields a unique curved axis which quantifies the folding of the backbone and a full set of helicoidal parameters describing the location of each peptide unit. The parameters obtained form a complete and independent set and can therefore be used for analyzing, comparing, or reconstructing protein backbone geometry. This algorithm has been implemented in a computer program named P-Curve. Several examples of its possible applications are discussed.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340060105
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    Identification of peptide hormones of the amphipathic helix class using the helical hydrophobic moment algorithm (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 61-69 
    Details
    ISSN: 0887-3585
    Keywords: peptides ; hormones ; amphipathic helix ; hydrophobic moment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Eisenberg's helical hydrophobic moment (〈μH〉) algorithm was applied to the analysis of the primary structure of amphipathic α-helical peptide hormones and an optimal method for identifying other peptides of this class determined. We quantitate and compare known amphipathic helical peptide hormones with a second group of peptides with proven nonamphipathic properties and determine the best method of distinguishing between them. The respective means of the maximum 11 residue 〈μH〉 for the amphipathic helical and control peptides were 0.46 (±/-0.07) and 0.33 (0.07) (P+0.004). To better reflect the amphipathic potential of the entire peptide, the percent of 11 residue segments in each peptide above a particular 〈μH〉 was plotted vs 〈μH〉. The resulting curves are referred to as HM-C. The mean HM-C (of the two groups) was highly significantly different such that the HM-C method was superior to others in its ability to distinguish amphipathic from nonamphipathic peptides. Several potential new members of this structural class were identified using this approach. Molecular modeling of a portion of one of these, prolactin inhibitory factor, reveals a strongly amphipathic α helix at residues 4-21. This computer-based method may enable rapid identification of peptide of the amphipathic α-helix class.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340060106
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    Site-directed mutagenesis of the T4 endonuclease V Gene: Mutations which enhance enzyme specific activity at low salt concentrations (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 128-138 
    Details
    ISSN: 0887-3585
    Keywords: DNA repair ; ultravioletlight ; pyrimidine dimers ; glycosylase ; apurinic/apyrimidinic endonuclease ; DNA repair enzymology ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Previous structure/function analyses of the DNA repairenzyme, T4 endonuclease V, have suggested that the extreme carboxyl portion of the enzyme is associated with pyrimidine dimer-specific binding (Recinos and Lloyd, and Stump and Lloyd, Biochemistry 27:1832-1838 and 1839-1843, 1988, respectively). Within the final 11 amino acids there are 5 aromatic, 2 basic, and no acidic residues and it has been proposed that these residues stack with and electrostatically interact with the kinked DNA at the site of a pyrimidine dimer. The role of the tyrosine residue at position 129 has beeninvestigated by oligonucleotide site-directed mutagenesis in which the codon for Tyr-129 has been altered to reflect conservative changesof Trp and Phe and more dramatic changes of Ser- a stop, codon, deletion of the codon or introduction of a frameshift. Both changesto the aromatic amino acids resulted in proteins which accumulated will in E. coli and not only significantly enhanced the UV survival of repair, deficient cells but also complemented a defective denV gene within UV-irradiated T4 phage. Partially purified preparations of the Tyr-129 → Trp and Tyr-129 → Phe mutants were assayed for their ability to processively incise UV-irradiated plasmid DNA (a nicking reaction carried out at low 25 mM salt concentrations). The mutant enzymes Tyr-129 → Phe and Tyr-129 → Trp displayed a 1000% and 500% enhanced specific nicking activity, respectively. These reactions were also shown to be completely processive. Assays performed at higher (100 mM) salt concentrations reduced the specific activities of the mutant enzymes approximately to that of wild type for the Tyr-129 → Phe mutant and to 20% that of wild type for the Tyr1-29 → Trp mutant.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340060204
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    Salt or ion bridges in biological system: A study employing quantum and molecular mechanics (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 168-192 
    Details
    ISSN: 0887-3585
    Keywords: salt bridge ; ab initio ; calcium ; magnesium ; carboxylate ; phosphate ; ammonium ; guanidinium ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Equilibrium geometries and binding energies of model “salt” or “ion” bridge systems have been computed by ab initio quantum chemistry techniques (GAUSSIAN82) and by empirical techniques (AMBER2.0). Formate and dimethyl phosphate served as anions in the model compounds while interacting with several organic cations, including methyl ammonium, methyl guanidinium, and divalent metal ion (either Mg2+ or Ca2+) without and with an additional chloride; and a divalent metal ion (either Mg2+ or Ca2+), chloride, and four water molecules of hydration about the metal ion. The majority of the quantum chemical computations were performed using a split-valence basis set. For the model compounds studied we find that the ab initio geometries are in remarkably goodagreement with the molecular mechanics geometries.Several Calculations werealso performed using diffuse fractions. The formate anion binds these modelcations more strongly than does dimethyl phosphate, while the organiccation methyl ammonium binds model anions more strongly than does methyl guanidinium. Finally, in model compounds including organic anions, Mg2+ or Ca2+ and four molecules of water, and a chloride anion, we find that the equilibrium structure of the magnesium complex involves a solvent separated ion pair (the magnesium ion is six coordinate), whereas the calcium ion complex remains seven coordinate. Molecular mechanics overestimates binding energies, but the estimates may be close enough to actual binding energies togive useful insight into the details energies to give useful insight into the details of salt bridges in biological systems.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060207
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    Peptide sequencing and site-directed mutagenesis identify tyrosine-319 as the active site tyrosine of Escherichia coli DNA topoisomerase I (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 231-239 
    Details
    ISSN: 0887-3585
    Keywords: phosphotyrosine linkage ; protein-DNA transesterification ; enzyme mechanism ; DNA-protein covalent complex ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Tyrosine 319 of E. coli topoisomerase I is shown to be the activesite tyrosine that becomes covalently attached to a DNA 5′ phosphoryl group during the transient breakage of a DNA internucleotide bond by the enzyme. The tyrosine was mapped by trapping the covalent complex between the DNA and DNA topoisomerase I, digesting the complex exhaustively with trypsin, and sequencing the DNA-linked tryptic peptide. Site-directed mutagenesis converting Tyr-319 to a serine or phenylalanine completely inactivates the enzyme. The structure of the enzyme andits catalysis of DNA strand breakage, passage, and rejoining are discussed in terms of the available information.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060305
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  • 138
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    A hydrophobic cluster forms early in the folding of dihydrofolate reductase (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 259-266 
    Details
    ISSN: 0887-3585
    Keywords: protein folding ; folding intermediate ; hydrophobic effect ; tryptophan fluorescence ; site-directed mutagenesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The rapid kinetic phase that leads from unfolded species to transient folding intermediates in dihydrofolate reductase from Escherichia coli was examined by site-directed mutagenesis and by physicochemical means. The absence of this fluorescence-detected phase in the refolding of the Trp-74Phe mutant protein strongly implies that this early phase in refolding can be assigned to just one of the five Trp residues in the protein, Trp-74. In addition, water-soluble fluorescence quenching agents, iodide and cesium, have a much less significant effect on this early step in refolding than on the slower phases that lead to native and nativelike conformers. These and other data imply that an important early event in the folding of dihydrofolate reductase is the formation of a hydrophobic cluster which protects Trp-74 fromsolvent.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060308
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  • 139
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    Site-directed mutagenesis of colicin E1 provides specific attachment sites for spin labels whose spectra are sensitive to local conformation (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 294-305 
    Details
    ISSN: 0887-3585
    Keywords: α-helix ; EPR ; trypsinolysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Colicin E1 is an E. coli plasmid-lencoded water-soluble protein that spontaneously inserts into lipid membranes to form a voltage-gated ion channel. We have employed a novel approach is which site-directed mutagenesis is used to provide highly specific attachment points for nitroxide spin labels. A series of colicin mutants, differing only by the position of a single cysteine residue, were prepared and selectively labeled at that cysteine. A hydrophilic sequence (398-406) within the C-terminal domain of the water-soluble form of the protein was investigated and exhibited an electron paramagnetic resonancc (EPR) spectral periodicity strongly suggesting an amphiphilic α-helix. After removal of the N—terminus of the protein with trypsin, the spectra for this sequence indicate increased label mobility and a more flexible structure.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060312
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  • 140
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    Recombinant HIV1 protease secreted by Saccharomyces cerevisiae correctly processes myristylated gag polyprotein (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 324-337 
    Details
    ISSN: 0887-3585
    Keywords: aspartyl protease ; HIV/AIDS ; yeast expression ; polyprotein processing ; α-factor ; secretion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The protease of the human immunodeficiency virus type I (HIV1) was expressed both intracellularly and extracellularly in Saccharomyces cerevisiae. Intracellular expression of the protease was achieved by fusing a 179 amino acid precursor form of the protease to human superoxide dismutase (hSOD). Self-processing of the viral enzyme from the hybrid precursor was demonstrated to ocur within the yeast host. Secretion of the protease was achieved by fusing the leader sequence of yeast α-factor to the precursor form of the protrease or to the 99 amino acid mature form of the protease. Authentic and active forms of the retroviral enzyme were detected in yeast supernatants of cells expressing the precursor or the mature form of the protease. A D25E active site variant of the retroviral enzyme exhibited diminished autocatalytic activity when expressed intracellularly or secreted from yeast. The wild-type protease was active in an in vitro assay on the natural substrate, myristylated gag precursor, Pr53gag. Correct processing of Pr53gag at the Tyr 138-Pro 139 junction was confirmed by amino terminal sequence analysis of the resulting capsid protein (CA, p24). The secreted protease was purified to homogeneity from yeast media using preparative isoelectric focusing and reverse-phase HPLC. Amino terminal sequence analysis showed a sequence beginning at amino acid 1 of the mature enzyme (Pro) and another sequence beginning at amino acid 6 (Trp). This shorter sequence may represent a natural autolytic product of the proteaseaspartyl protease.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060315
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  • 141
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    Chemical modification of the RTEM-1 thiol β-lactamase by thiol-selective reagents: Evidence for activation of the primary nucleophile of the β-lactamase active site by adjacent functional groups (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 316-323 
    Details
    ISSN: 0887-3585
    Keywords: β-lactamase ; active site ; chemical modification ; thiol modification ; enzyme ammonium group ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The RTEM-1 thiol β-lactamase (Sigal, I. S., Harwood, B. G., Arentzen, R., Proc. Natl. Acad. Sci. USA. 79:7157-7160, 1982) is inactivated by thiol-selective reagents such as iodoacetamide, methyl methanethiosulfonate, and 4,4′-dipyridyldisulfide, which modify the active site thiol group. The pH-rate profiles of these inactivation reactions show that there are two nucleophilic forms of the enzyme, EH2 and EH, both of which, by analogy with the situation with cysteine proteinases, probably contain the active site nucleophile in the thiolate form. The pKa of the active site thiol is therefore shown by the data to be below 4.0. This low pKa is thought to reflect the presence of adjacent functionality which stabilizes the thiolate anion. The low nucleophilicity of the thiolate in both EH2 and EH, with respect to that of cysteine proteinases and model compounds, suggests that the thiolate of the thiol β-lactamase is stabilized by two hydrogen-bond donors. One of these, of pKa greater than 9.0, is suggested to be the conserved and essential Lys-73 ammonium group, of pKa around 6.7, is less clear, but may be the conserved Glu-166 carboxylic acid. β-Lactamase activity is associated with the EH2 form, and thus the β-lactamase active site is proposed to contain one basic or nucleophilic group (the thiolate in the thiol β-lactamase) and two acidic (hydrogen-bond donor) groups (one of which is likely to be the above-mentioned lysine ammonium group).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060314
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  • 142
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    The neuraminidase of influenza virus (1989)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 341-356 
    Details
    ISSN: 0887-3585
    Keywords: neuraminidase (sialidase) of influenza virus ; structure ; enzyme active site ; escape mutants ; structure of epitopes ; structures of neuraminidase ; Fab complexes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: It is the enzyme neuraminidase, projecting form the surface of influenza virus particles, which allows the virus to leave infected cells and spread in the body. Antibodies which inhibit the enzyme limit the infection, but antigenic variation of the neuraminidase renders it ineffective in a vaccine. This article describes the crystal structure of influenza virus neuraminidase, information about the active site which may lead to development of specific and effective inhibitors of the enzyme, and the structure of epitopes (antigenic determinants) on the neuraminidase. The 3-dimensional structure of the epitopes was obtained by X-ray diffraction methods using crystals of neuraminidase complexed with monoclonal antibody Fab fragments. Escape mutants, selected by growing virus in the presence of monoclonal antibodies to the neuraminidase, possess single amino acid sequence changes. The crystal structure of two mutants showed that the change in structure was restricted to that particular sidechain, but the change in the epitope was sufficient to abolish antibody binding even though it is known in one case that 21 other amino acids on the neuraminidase are in contact with the antibody.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340060402
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  • 143
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    Transient characteristics of oxygen probes with significant liquid film effects (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 39-48 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Various experimental procedures for the determination of transient characteristics with significant liquid film effects were tested. A comparison between transient characteristics obtained experimentally and those calculated from rational models indicates that all procedures but one give highly inconsistent results. Recalculation of transient characteristics with no liquid film (easily measured in the gas phase) to that with liquid film (occurring in viscous liquids) is recommended as well as the selected experimental procedure which yields consistent results in the situations where the steady-state probe reading is decreased up to one-half due to the liquid film.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330107
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  • 144
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    Experimental multivariable adaptive optimization of the steady-state cellular productivity of a continuous baker's yeast culture (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 16-25 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A multivariable adaptive optimization algorithm that uses transient data to improve the optimization speed was successfully implemented on-line to maximize the steady-state cellular productivity of a continuous culture of baker's yeast. The algorithm was shown to be stable even during periods of oscillatory growth and was able to reoptimize the culture when planned disturbances were introduced. Although adaptive tuning of the forgetting factor improved the performance, further refinements in the adaptive forgetting factor algorithm are necessary for completely satisfactory results.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330104
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  • 145
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    Anoxic-oxic activated-sludge of cyanides and phenols (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 32-38 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The anoxic-oxic activated-sludge process has been evaluated in a laboratory investigation as a means for effective treatment of cyanide-laden wastewaters, with phenols used as the organic carbon sources for denitrification reactions. The performance of the process was evaluated at different levels of feed cyanide concentration and mean cell residence time (MCRT). The results obtained indicate that the phenolic compounds used can be effectively used as the organic carbon sources to promote denitrification reactions. The effects of cyanide inhibition on overall TOC removal can be alleviated at longer MCRTs. Between 1.2 and 2.2 g TOC can be utilized per gram NO2 + NO3- -N removed in the anoxic chamber depending on the prevailing MCRT. Microbial oxidation of cyanide and thiocyanate which yields ammonia is the main mechanism responsible for the removal of cyanide and thiocyanate observed in the anoxic-oxic activated-sludge process. Excellent removal efficiencies have been observed with feed concentrations up to 60 mg CN-/L and 100 mg SCN-/L Frequent exposure of autotrophic and aerobic cyanideutilizing microbes does not impede their activities in the oxic environment. Good nitrification and denitrification efficiencies are attainable in the anoxic-oxic activated-sludge process in the presence of high feed cyanide and thiocyanate concentrations, provided that MCRT is maintained at a desirable level. As a result, the microbial degradation of cyanide and thiocyanate in conjunction with nitrification and denitrification to produce innocuous nitrogen gas is feasible in the anoxic-oxic activated-sludge process.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330106
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  • 146
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    Alginate as immobilization material. II: Determination of polyphenol contaminants by fluorescence spectroscopy, and evaluation of methods for their removal (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 90-94 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alginates, both commercial and laboratory made, are strongly fluorescent due to small amounts of polyphenolic materials. These contaminants can be detected by fluorescence spectroscopy in concentrations lower than 1 ppm. This technique has been used to measure polyphenols in a wide range of alginates and various procedures for preparation of biotechnological-grade alginates have been evaluated.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330112
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  • 147
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    An algorithm for operating a fed-batch fermentor at optimum specific-growth rate (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 115-125 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An algorithm for operating a fed-batch fermentor at an optimum specific fermentation rate is proposed. It does not require on-line measurement of nutrient concentration in the culture medium. An on-line estimate of the specific fermentation rate is sufficient for implementation of this scheme. The algorithm is model independent and works well even with poor estimates of the product yields and the specific fermentation rate. Results of a detailed simulation study are presented for a simple case of optimization of cell-mass production in a fed-batch fermentor. The results clearly demonstrate the efficacy of this algorithm under a wide range of fermentation situations.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330115
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  • 148
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    Bacterial deposition on and detachment from surfaces in turbulent flow (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 157-163 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A number of experimental studies on deposition and detachment of bacterial cells of Pseudomonas sp. was performed in an inclined plate apparatus 2.3 m long. In each run, ca. 108cells were introduced into a layer of flowing water at Reynolds numbers of ca. 1000 and 1300. After a preset time, the flow was stopped and the position of attached cells measured. Spatial pattern of attached cells was initially aggregative and remained so for lower flow rates. For higher flow rates the pattern tended towards randomness, perhaps as a result of cell detachment. Overall sticking efficiency of cells was very small (ca. 10-5).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330204
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  • 149
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    Protein purification by affinity binding to unilamellar vesicles (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 173-182 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel purification technique is proposed which employs affinity-ligand-modified liposomes to specifically purify bioactive macromolecules from solution. This process is demonstrated with avidin as the model biomolecule and biotin as the affinity ligand. Biotin is covalently bound to the surface of small unilamellar vesicles composed of dimyristoyl phosphatidylcholine (DMPC) and dimyristoyl phosphatidylethanolamine (DMPE). The number of accessible binding sites on the liposomes is determined by titration with avidin, and the kinetics of binding are evaluated by monitoring the concentration of free avidin in solution after the addition of biotinylated liposomes. The specificity of the process is determined by following the affinity binding of avidin to biotinylated liposomes in the presence of model impurities (i.e., lysozyme and cytochrome C). Liposome-bound avidin is separated from the impurities by ultrafiltration through a membrane which retains the liposomes.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330206
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  • 150
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    Energy requirements for the size reduction of poplar and aspen wood (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 207-210 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The energy requirements associated with conventional mechanical size reduction of poplar and aspen wood are compared to a new method of size reduction employing a wood planer. Although the planer requires about 2.3 times less energy to achieve the same size reduction as conventional methods, large-scale equipment to implement this approach does not currently exist. Explosive depressurization was also compared to conventional mechanical size reduction. The conventional mechanical methods require roughly 70% more energy to achieve the same size reduction as explosive depressurization. Thus, explosive depressurization appears to be the preferred method and has the added benefit of altering the chemical structure of the wood to enhance the enzymatic hydrolysis of the cellulose fraction.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330210
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  • 151
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    Treatment of wheat straw with alkaline hydrogen peroxide in a modified extruder (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 233-236 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330215
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  • 152
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    Masthead (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330301
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  • 153
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    Dynamics of foreign protein secretion from Saccharomyces cerevisiae (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 272-281 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model describing the dynamics of foreign protein secretion from yeast cells is developed. The secretion events, which are a series of complicated enzymatic reactions and carrier-involved transport, are lumped to a practically applicable model structure, based on the major interactions between the heterologous polypeptides and the host cell's secretory machinery through the pathway. The developed model structure predicts that the secretion rate constant is represented as a saturated form with respect to the host cell's specific growth rate. The validity of the proposed model structure is tested by generating dynamic response data to a step input of cycloheximide. The model system used in the experiment is SEY2102-s21, which has an integrated copy of a yeast secretion-mutant invertase that simulates well typical gene cassettes designed to secrete mature foreign proteins utilizing the yeast cell's secretion signals. Protein quantification is done by gel electrophoresis followed by immuno-blot on nitrocellulose filters and subsequent scanning with a reflectance densitometer. Experimental data confirm the proposed model structure.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330305
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  • 154
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    Biosynthesis of pullulan using immobilized Aureobasidium pullulans cells (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 306-312 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Immobilization of Aureobasidium pullulans by adsorption on solid supports and entrapment in open pore polyurethane foam were attempted. By adsorption, the highest cell loading of 0.012-0.018 g dry wt/cm2 support was obtained in pH 2.0 medium. Under this acidic condition, the net surface charges (zeta potentials) of both the cells and supports were close to zero and no pullulan was synthesized. Cationic coatings of Cytodex and polyethylenimine were not efficient in enhancing the binding strength between the cells and the supports. Surface immobilized cells and polyurethane foam entrapped cells exhibited a similar fermentation characteristics resulting in ca. 18 g/L pullulan and ca. 5 g/L leaked cells. However, cells entrapped in the polyurethane foam were more shear resistant. The immobilized cells thus could be repeatedly used for pullulan biosynthesis.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330309
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  • 155
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    A model for continuous fermentations with amylolytic yeasts (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 338-343 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A two-stage, associative fermentation process is more effective for continuous yeast biomass production from starch than a single-stage mixed culture fermentation process. By operating two stages, competition for the same growth limiting substrate is reduced leading to efficient starch utilization. In this article, a mathematical model has been proposed for continuous, two-stage fermentation with a pure culture, amylolytic yeast in the first stage and a mixed culture second stage with a faster growing, nonamylolytic yeast. The model parameters were determined for Saccharomycopsis fibuligera and Candida utilis in continuous, single-stage, pure cultures. In the two-stage model, the effects of changes in dilution rate on biomass, amylase, reducing sugar, and starch concentration, and ratio of stage volumes on microbial composition are discussed and compared with experimental data.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330313
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  • 156
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    An algorithmic approach to constructing the on-line estimation system for the specific growth rate (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 354-364 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The objective of this article is to propose an algorithm for the on-line estimation of the specific growth rate in a batch or a fed-batch fermentation process. The algorithm shows the practical procedure for the estimation method utilizing the macroscopic balance and the extended Kalman filter. A number of studies of the on line estimation have been presented. However, there are few studies discussing about the selection of the observed variables and for the tuning of some parameters of the extended Kalman filter, such as covariance matrix and initial values of the state.The beginning of this article is devoted to explain the selection of the observed variable. This information is very important in terms of the practical know-how for using technique. It is discovered that the condition number is a practically useful and valid criterion for number is a practically useful and valid criterion for choosing the variable to be observed.Next, when the extended Kalman filter in applied to the online estimation of the specific growth rate, which is directly unmeasurable, criteria for judging the validity of the estimated value from the observed data are proposed. Based on the proposed criterial, the system equation of the specific growth rate is selected and initial value of the state variable and covariance matrix of the system noises are adjusted. From many experiments, it is certified that the specific growth rate in the batch or fed -batch fermentation can be estimated accurately by means of the algorithm proposed here. In these experiments, that is, when the cell concentration is measured directly, the extended Kalman filter using the convariance matrix with a constant element can estimate more accurately values of the specific growth rate than the adaptive extended Kalman filter does.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330315
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  • 157
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    Sliding controller design for a nonlinear fermentation system (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 377-385 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The design of a sliding controller for a continuous fermentation process is presented. The results obtained by simulation have proved the control scheme to be very robust. Regulation of substrate concentration at its optimal value has been achieved even though process parameters change their nominal values. Chattering effects are decreased by introducing a minor modification of the control variable around the sliding surface.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330402
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  • 158
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    Masthead (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330401
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  • 159
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    Modelling Xanthomonas campestris batch fermentations in a bubble column (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 394-405 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Rate and yield expressions relating to biomass and xanthan formation and to nitrogen, glucose, and oxygen consumption were established for Xanthomonas campestris batch fermentations in a bubble column. Microbial growth was described by the logistic rate equation, characterized by a maximum specific growth rate μM = 0.5 h-1 and a maximum attainable cell concentration provided by nitrogenous compounds. With regard to carbon metabolism, the decrease with time in experimental yields and in the experimental specific rates of xanthan production and glucose assimilation demonstrated the inadequacy of the Luedeking-Piret model. These decreases were connected to the simultaneous drop in dissolved-oxygen tension observed during xanthan synthesis. The knowledge of metabolic pathways and energetic balance were used to establish the relationships between substrate utilization, ATP generation, and xanthan production. The model was structured by assuming the oxygen limitation of both the respiration rate and the efficiency of the oxidative phosphorylation mechanism (P/O ratio). Consequently, the specific rates and yield expressions became dependent on the dissolved-oxygen tension, i.e., of the volumetric oxygen transfer in the fermentor.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330404
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  • 160
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    Activity of Pseudomonas aeruginosa in biofilms: Effect of calcium (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 406-414 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aerobic glucose metabolism by Pseudomonas aeruginosa biofilms at various calcium loading rates was investigated. The influence of calcium on specific growth rate, extracellular polymeric substance (EPS) formation rate, biofilm detachment rate, and biofilm calcium concentrations was determined. Calcium accumulated in the biofilm in proportion to the liquid phase concentration. Increasing calcium concentration increased the cohesiveness of the biofilm as indicated by a lower relative detachment rate. Specific activity in the biofilm was the same as that measured in a chemostat and was not influenced by changing calcium concentration. EPS formation rate in the biofilm was unaffected by calcium concentration but was higher than that observed in a chemostat.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330405
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  • 161
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    Escherichia coli plasmid production in fermenter (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 386-393 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Escherichia coli harboring a recombinant plasmid was grown in a fermenter to study the effects of selected process parameters on the growth of the microbe and on plasmid amplification with chloramphenicol treatment. Eighteen fermentations were carried out according to a statistical experimental design in which the fermentation temperature, pH, and turbidity of culture at the onset of plasmid amplification were the selected independent process variables. Static regression models describing the process were derived from the experimental results. It turned out that recombinant plasmid copy numbers could be influenced by controlling fermentation temperature and pH. The maximal copy number during bacterial growth phase and the optimal plasmid production were found to require fermentation conditions different from those needed for optimal bacterial growth and cell division. The conditions also differed significantly from those routinely used in research laboratories for plasmid preparation. The chloramphenicol treatment increased the plasmid copy number compared with chromosome numbers up to fivefold. Some of the data suggest that under certain conditions the number of chromosome molecules in E. coli cells may rise during the plasmid amplification stage. Statistical experimental design, a nucleic acid sandwich hybridization technique for plasmid quantification, and regression models proved to be useful in this study.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330403
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  • 162
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    Hydrolysis of the polysaccharides of straw by enzymes produced by a mutant strain of the fungus Penicillium pinophilum (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 422-427 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The saccharification of the polysaccharides of barley, oat, and wheat straws and Solka Floc was studied using the extracellular enzyme system synthesized by mutant strain NTG III/6 of the fungus Penicillium pinophilum 87160iii. The enzymes obtained in cultures containing Solka Floc or barley straw as the carbon source were compared. Solka Floc at 10% (w/v) concentration was hydrolyzed to the extent of 70% in 72 h at 50°C using a reaction mixture containing 7 filter paper units/mL of cellulase induced on Solka Floc, but hydrolysis was increased to 90% when the enzyme induced on barley straw was used. Under the same conditions, the polysaccharides in barley, oat, and wheat straws were hydrolyzed, respectively, in 72 h, to the extent of 42-48%, 62%, and 52%, but hydrolysis was increased to 93%, 100%, and 92%, respectively, after treatment of the substrates with alkaline-H2O2 reagent at room temperature.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330407
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  • 163
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    An electrochemical method of measuring the oxidation rate of ferrous to ferric iron with oxygen in the presence of Thiobacillus ferrooxidans (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 428-439 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxidation of Fe2+ with oxygen in sulfate solutions was studied in the presence of T. ferrooxidans. To measure the chemical activity of bacteria, and the oxidation rate of iron, the redox potentials of solutions were continuously monitored during the experiments. The redox potentials were simultaneously monitored on the platinum and pyrite indicator electrodes. The redox potential versus time curves were further used to calculate the basic kinetic parameters, such as the reaction orders, the activation energy, and the frequency factor. It was found that under atmospheric conditions, and at Fe2+ 〈 0.001M, T 〈 25°C, and at pH above 2.2, the oxidation of iron is governed by the following rate expression: \documentclass{article}\pagestyle{empty}\begin{document}$$ - \frac{{d[{\rm Fe}^{2 + }]}}{{dt}} = 1.62 \times 10^{11} C_{{\rm bact}} [{\rm H}^ + ][{\rm Fe}^{2 + }]p{\rm O}_2 e^{ - (58.77/RT)} $$\end{document} Below pH = 2.2, the oxidation rate is independent of H+ Concentration.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330408
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  • 164
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    Transient method for proposing the mechanisms of reactions over immobilized enzymes (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 415-421 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The transient response method is introduced to elucidate the mechanism of reaction over immobilized enzyme. Glucose oxidation over the glucose oxidase that was immobilized on ion-exchange resin using glutaraldehyde as a linking agent is selected as an example here. The transient responses of a fixed-bed reactor to step increases and decreases in glucose, oxygen, and gluconolactone feed concentrations have been monitored and interpreted. From some responses, we have found that gluconolactone is formed in the reaction of glucose with adsorbed oxygen, while hydrogen peroxide is formed in the reaction of oxygen with adsorbed glucose. Combining all information from interpreting the responses with the literature, a mechanistic picture can be obtained as follows: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {E_{{\rm ox}} + G \to E_{{\rm red}} GL} \\ {E_{{\rm red}} GL \to E_{{\rm red}} + GL} \\ {E_{{\rm red}} + {\rm O}_2 \to E_{{\rm ox}} {\rm H}_2 {\rm O}_2 } \\ {E_{{\rm ox}} {\rm H}_2 {\rm O}_2 \to E_{{\rm ox}} + {\rm H}_2 {\rm O}_2 } \\ \end{array} $$\end{document}.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330406
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  • 165
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    Mathematical descriptions of hybridoma culture kinetics: II. The relationship between thiol chemistry and the degradation of serum activity (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 440-450 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The growth rate of the hybridoma cell line ATCC-CRL-1606 in low serum medium declines rapidly with time after inoculation. To characterize this phenomenon, the stability of the growth-promoting activity of serum was investigated. The activity of serum was found to de grade with time, and was stabilized by alterations in the medium formulation that acted to lower the oxidation/reduction potential. This included both the addition of thiols and the elimination of disulfides from the medium. Additionally, cysteine and other thiols were shown to stimulate growth in low serum, low cell density cultures, suggesting that thiols may be rate-limiting in low serum medium. Stimulation of growth by thiol addition was less significant at high cell levels, implying that the cells themselves may be acting to reduce their environment. A hypothesis is presented based on these results which suggests that the actual rate-limiting moieties in low serum cultures may be dithiols.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330409
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  • 166
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    Data analysis of plasmid maintenance in a CSTR (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 451-459 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple procedure is developed to process experimental data from plasmid maintenance studies of recombinant cells in a chemostat with nonselective medium. This procedure, based on the model proposed by Imanaka and Aiba, provides quantitative information on the rate of plasmid loss and the difference in the specific growth rate between the plasmid-carrying and plasmid-free cells. The performance of the proposed method is evaluated through simulation studies. In addition, the method is applied to a set of previously reported experimental data. The two-parameter model, together with the estimated parameter values, provides an excellent fit to the experimental data.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330410
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  • 167
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    Impossibility of coexistence of three pure and simple competitors in configurations of three interconnected chemostats (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 460-470 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It is well established that pure and simple microbial competitors cannot coexist at a steady state if their environment is homogeneous. For the case of two microbial populations competing purely and simply in two interconnected chemostats having time-invariant input(s), it is known from the literature that a stable steady state of coexistence arises in domains of the operating parameters space and is attributed to the spatial heterogeneities of the system, which allow a different species to have the competitive advantage in each one of the two sub-environments. This article investigates whether the aforementioned result can be extended to the case of three species competing in three interconnected vessels. By studying all possible alternate configurations of the three-chemostat system, it is shown that coexistence of the three species is impossible, except possibly for some discrete values of the operating parameters. Some potential explanations for the results are discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330411
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  • 168
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    Improvement of ethanol fermentation under hyperbaric conditions (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 471-476 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recently more and more interest is manifested in the utilization of high-pressure extraction using supercritical gases for the purification of products in biochemical processes. Some researchers have examined the possibility of circulating continuously a supercritical gas through the fermentor, under hyperbaric pressure, to recover the desired product while the fermentation is taking place. However, an earlier study has demonstrated that fermentation with baker's yeast was inhibited by a long exposure under hyperbaric pressure. This article is concerned with the improvement of ethanol production under hyperbaric pressure in view of the development of an integrated fermentation-extraction process where supercritical carbon dioxide would be used for the in situ recovery of ethanol. The selection of the best yeast strain and operation under cyclic pressures are considered.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330412
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  • 169
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    Use of culture fluorescence as a sensor for on-line discrimination of host and overproducing recombinant Escherichia coli (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 500-505 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The culture fluorescence of two recombinant Escherichia coli strains with high plasmid copy number were studied and compared to both the host and low copy number varieties of the corresponding strains. Culture fluorescence data are related to the concentration of reduced intracellular nicotinamide adenine dinucleotide within a cell, and can therefore be used as a means for detecting changes in metabolic states. Correlation curves relating culture fluorescence to biomass show that the recombinant system maintains a larger pool of intracellular NADH at high plasmid copy numbers than either the host or the recombinant system at low copy numbers. These results demonstrate the ability of a fluorescence probe to detect differences in the metabolic demands made on an over-producing recombinant organism.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330415
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  • 170
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    The transient responses of hybridoma cells to nutrient additions in continuous culture: II. Glutamine pulse and step changes (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 487-499 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The transient and steady-state responses of hybridoma growth and metabolism to glutamine pulse and step changes have been examined. Metabolic quotients are reported for oxygen, glucose, lactate, ammonia, glutamine, alanine, and other amino acids. The specific glutamine consumption rate increased rapidly after all glutamine additions, but the responses of the glucose and oxygen consumption rates and the cell concentration were found to depend on the intial feed glutamine concentration. The glucose consumption rate was 1.4-10.9 times that of glutamine, and serine and branched-chain amino acids were consumed in larger amounts at the higher glucose: glutamine uptake ratios. It was estimated that maintenance accounted for ca. 60% of the cellular ATP requirements at specific growth rates ranging from 0.57 to 0.68 day-1.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330414
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  • 171
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    Suitable contacting pattern for optimal product distribution in a recombinant cell system (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 508-511 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330417
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  • 172
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    Peroxidase-Catalyzed oxidation of p-anisidine with H2O2 in toluene (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 512-517 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330418
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  • 173
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    Yield coefficients for cell mass and product formation (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 506-507 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330416
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  • 174
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    Transient responses of hybridoma cells to nutrient additions in continuous culture: I. Glucose pulse and step changes (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 477-486 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Glucose and glutamine are the main nutrients used by mammalian cells in culture. Each provides unique biosynthetic precursors but are complementary for production of other metabolites and energy. The transient and steady-state responses of hybridoma growth and metabolism to glucose pulse and step changes have been examined. Metabolic quotients are reported for oxygen, glucose, lactate, ammonia, glutamine, alanine, and other amino acids. The glucose consumption rate increased by 100-200% immediately after glucose was added to the reactor, and the increased glycolytic ATP production appears to be responsible for the concurrent rapid decrease in the oxygen consumption rate. The effects on glutamine consumption were delayed, probably due to buffering by the TCA cycle and interrelated pathways. A period of increased biosynthetic activity, as evidenced by an increase in the estimated specific ATP production rate and lower by-product yields from glutamine, preceded the increase in cell concentration after the glucose step change. The biosynthetic yield of cells from ATP was calculated, and it was estimated that maintenance accounted for about 60% of the energy used by the cells at a specific growth rate of 0.66 day-1. The estimated 22% ATP production due to glycoysis was twice as great as that before the step change.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330413
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  • 175
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    Masthead (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330501
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  • 176
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    Effect of surface potential on consumption of charged substrates (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 521-523 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Due to the surface charge inherent on all microorganism cell surfaces, the consumption of charged molecules by these microorganisms will be affected by the electrostatic interactions between the substrate and the cell surface. This article derives an equation that shows that these electrostatic interactions result in a change in the Monod half-velocity constant. The resulting rate of consumption is affected and can be either higher or lower than the rate of consumption of an uncharged substrate molecule.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330502
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  • 177
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    Thermophilic semisolid anaerobic digestion of municipal refuses (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 536-541 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Comparison of both mesophilic (35°C) and thermophilic (55°C) anaerobic digestions of the organic fraction of municipal refuses in pilot digesters designed to process in a semisolid phase at total solids concentrations of ca. 25% shows that the average gas production is 20-25% higher in thermophilic conditions than in mesophilic conditions even for a retention time of 10 days. These results and the data recorded during long periods of experimentation indicate that the process allows to increase the net energy production and to improve the economical balance of an industrial plant.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330504
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  • 178
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    Drag reducing properties of microalgal exopolymers (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 550-557 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dilute aqueous solutions of polymers released by marine phytoplankton (microalgae) were shown to effectively reduce drag in capillary pipe flow. Tests were performed in a capillary turbulent flow viscometer which extruded small samples under high pressures. In all, 22 species were screened, and the products of one chlorophyte and four rhodophyte species proved especially effective. The viscoelastic polymers produced by these species delayed the transition from laminar to turbulent flow to significantly higher Re. In general, polymeric regime segments come off the maximum drag reduction asymptote at characteristic retro-onset points, and come to lie approximately parallel to, but displaced upwards from the Prandtl-von Karman line. The delay to transition was shown to be dependent on additive polymer concentration, capillary diameter, and temperature. Ionic concentration, ionic composition, or pH had little effect on drag reducing properties.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330506
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  • 179
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    Studies on growth and cardenolide production of Digitalis lanata tissue cultures (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 558-562 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Digitalis lanata cell cultures grown as small undifferentiated aggregates in suspension culture can be redifferentiated into green embryos that produce cardenolides. The possibility of using a statistical (Box-Wilson) experimental design to study the effects of four different variables on growth, differentiation, and cardenolide production of D. lanata tissue cultures are investigated. The results of the analyses were processed by linear regression analysis. Mathematical models explaining the effects of the variables were developed. The concentration of maltose and the NO3-—NH4+ ratio were found to be significant variables for both growth and cardenolide production. The size of the inoculum was also important.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330507
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  • 180
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    Mathematical modeling of growth and production of alcohol oxidase by Hansenula polymorpha grown on methanol-glucose mixtures (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 524-535 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The modeling of growth and production of methanol oxidase (MOX) by Hansenula polymorpha CBS 4732 has been studied to provide a mathematical description of such production processes. Two kinds of mathematical models were constructed for growth on methanol and on mixtures of methanol and glucose. The model for growth on methanol as the sole carbon source consists of kinetics expressions, a limited number of key steps incorporating substrate and production inhibition. This model was used to predict and simulate the culture dynamics at the start-up, the most critical step in continuous cultivation. The growth on mixtures of methanol and glucose was modeled assuming virtually independent metabolic pathways. The induction and production of MOX could be described by adaptation of various repression equations for various data from the literature. The models describe both experimental data and literature data on growth of H. polymorpha CBS 4732 on glucose-methanol mixtures satisfactorily. All parameters for the induction-repression model for growth of H. polymorpha CBS 4732 on glucose-methanol mixtures yielded evidence that a similar induction-repression pattern is involved in MOX production. Catalase, however, is repressed by a different mechanism.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330503
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  • 181
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    Recycle use of immobilized glucoamylase by tangential flow filtration unit (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 542-549 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Various properties of glucoamylase immobilized onto corn stover supporting material and separation of immobilized enzyme by tangential flow filtration unit were studied. Optimum pH and temperature of immobilized enzyme were 3.5 and 60°C, respectively. Enzyme stability was studied in a packed-bed column. The starch conversion rate was attained at 81% for 15 days; after that, the hydrolysis rate gradually decreased. Size of supporting material proved to be an important factor, with higher activity and good loading yield resulting from smaller supporting material. Glucoamylase immobilized onto supporting material less than 44 μm was used for hydrolysis of 10% soluble starch at pH 3.5 and 40°C for 3 h. Then immobilized glucoamylase was separated from the product by means of a tangential flow filtration unit using a 0.2-μm pore size Nylon 66 membrane filter. This operation was continued until 180 ml filtrate was obtained from a 260-mL starting volume. Then, the next batch was started by adding 180 mL starch substrate into the reactor. The batchwise experiments were repeated 20 times. The average filtration rate of each batch was determined and found to sharply decline during the first four batches. Thereafter, it gradually decreased from batch to batch. The cause of decreasing filtration rate appeared to be due to retrogradation of starch. The percentage of starch hydrolysis within 20 batches was in the range 89-96%. The filtration rate becomes higher if the hydrolyzation time is extended to 14 h. Resistance to filtration was also investigated. Almost all of the total resistance is related to insoluble materials, with the significant part of this from the resistance due to insoluble materials deposited on a surface of membrane and boundary layer resistance. Using a microscopic method, no microorganisms were found in the filtrate.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330505
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  • 182
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    Relation between stabilization and rigidification of the three-dimensional structure of an enzyme (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 563-569 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Purified cellobiase was coupled to periodate-oxidized dextran by reductive alkylation using sodium cyanoborohydride, sodium borohydride, and dimethylaminoborane for various reaction times. The thermal stability of the different conjugates obtained was studied and correlated to the number of links introduced between the enzyme and the soluble support. We observe that resistance to heat inactivation increases as a function of the number of modified lysines. Sodium cyanoborohydride was the most effective reducing agent. After 24 h reaction, the modification of 92% of the lysines gave a cellobiase-dextran conjugate that is a most stable enzyme. We conclude that the thermal stability observed for the chemically modified enzyme results from the rigidification of the three-dimensional structure of the protein. This rigidification increases with the number of links introduced between the enzyme and the polysaccharide. We also observe that chemical modification leads to a heterogeneous population of stabilized enzymes. Because of this heterogeneous population, it is necessary to develop a mathematical model of the kinetics of enzyme inactivation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330508
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  • 183
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    Improvement of cellulase activity by immobilization of sporotrichum cellulophilum (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 1343-1346 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260331017
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  • 184
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    Dynamic modeling of immobilized cell reactor: Application to ethanol fermentation (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 1317-1323 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model has been developed for the unsteady-state operation of an immobilized cell reactor. The substrate solution flows through a mixed-flow reactor in which cells immobilized in gel beads are retained. The substrate diffuses from the external surface of the gel beads to some internal location where reaction occurs. The product diffuses from the gel beads into liquid medium which flows out of the reactor. The model combines simultaneous diffusion and reaction, as well as cell growth, and it can predict how the rates of substrate consumption, product formation, and cell growth vary with time and with initial conditions. Ethanol fermentation was chosen as a representative reaction in the immobilized cell reactor, and numerical calculations were carried out. Excellent agreement was observed between model predictions and experimental data available in the literature.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260331014
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  • 185
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    Removal of thorium from simulated acid process streams by fungal biomass (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 592-597 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biomass from several fungal species removed thorium from solution in 1M HNO3, pH 0-1. Thorium uptake was saturable with increasing thorium concentration, although the equilibria did not correspond to a simple ad sorption isotherm. Thorium uptake was altered by the biomass concentration, the uptake per unit biomass being reduced at high biomass concentrations. The presence of Al3+ and Fe3+ only slightly inhibited uptake of thorium while Ca2+, Mg2+, and Na+ had no effect. Thus fungal biomass appears capable of removing thorium from solution under chemical conditions existing in acid waste liquors. Thorium uptake was increased by pretreatment using detergent and also, in the case of filamentous fungi, varied with the culture conditions, which implies that the thorium uptake characteristics of fungal biomass are able to be manipulated by these or similar means for optimum performance.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330512
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  • 186
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    Immobilization of glucose oxidase with Bombyx mori silk fibroin by only stretching treatment and its application to glucose sensor (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 598-603 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Glucose oxidase (GOD) was immobilized in Bombyx mori silk fibroin membrane by only physical treatment, i.e., stretching without any chemical reagents. This is due to the structural transition of the silk fibroin membrane from random coil to antiparallel β-sheet (Silk II) induced by the stretching treatment. Permeability coefficients of glucose and oxygen through the fibroin membrane were determined; the permeability of glucose decreased with increasing degree of stretching. The immobilized enzyme activity was characterized with apparent Michaelis constant Kmapp and maximal activity Vm. Optimum pH of the activity of the immobilized enzyme was shifted to the value around neutrality, and the activity was maintained to the higher values on both sides of the optimum pH compared with the case of free enzymes. Thermal stability was scarcely lost even at 50°C, although the free enzyme lost about 70% of the original activity. Thus, the stabilities of the enzyme vs. pH and heat were much improved by the immobilization with silk. Glucose sensor prepared with this GOD-immobilized fibroin membrane was developed; the capabilities such as the response time, calibration curve, and repeating usage were determined.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330513
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  • 187
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    Measurement of oxygen solubility in fermentation media: A colorimetric method (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 578-583 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Methods of measuring oxygen solubility in culture media are scarce, and those available are tedious to apply. A simple colorimetric assay was developed and applied to the analysis of oxygen solubility during alcoholic fermentation. The method was based on the consumption of oxygen by glucose oxidase activity and the production of the pink quinone of syringaldazine by coupled peroxidase activity. Color formation at 526 nm progressed through an optimum that was a linear function of the oxygen added to the assay. Sensitivity was maximized by operating at pH 7 and limiting the medium sample volume added. Each assay took 10-15 min to prepare and react. Reaction time was minimized by using abundant glucose and enzyme concentrations. Data obtained by the assay developed showed good agreement with published oxygen solubilities in water and selected media at various temperatures. Subsequent analyses of fermentation broths indicated falling sugar concentration to be primarily responsible for increases in oxygen solubility during fermentation. For example, during fermentations started with 230 g/L xylose or glucose, oxygen solubility could increase by 41% due to sugar consumption alone. This procedure can provide the solubility data needed to accurately calibrate in-line electronic probes for monitoring dissolved oxygen concentration during fermentation processes.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330510
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  • 188
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    Liquid residence time distributions in immobilized cell bioreactors (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 604-612 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Previous work has demonstrated that high ethanol productivities can be achieved using yeast or bacterial cells adsorbed onto the surface of ion exchange resin in vertical packed bed bioreactors. The present work quantitatively characterizes the overall degree of backmixing in such reactors at two scales of operation: 2.0 and 8.0 L. Stimulus-response experiments, using two solvents (2,3-butanediol and 2-ethoxyethanol) as tracers, were performed to measure the liquid phase residence time distribution (RTD) during continuous ethanol fermentations using the yeast Saccharomyces cerevisiae and the bacterium Zymomonas mobilis at the 2-L scale, and with S. cerevisiae at the 8-L scale. In order to separately determine the effects of liquid flow rate and gas evolution on the degree of mixing, stimulus-response experiments were also performed in the systems without microbial cells present. The evolution of CO2 was found to dramatically increase the extent of mixing; however, the tanks-in-series model for non-ideal flow represented the systems adequately. The packed beds were equivalent to over 70 tanks-in-series during abiotic operation while during fermentations, with similar liquid flow rates, they ranged in equivalence from 35 to 15 tanks-in-series. This increased knowledge of the overall degree of mixing in packed bed, immobilized cell bioreactors will allow for more accurate kinetic modelling and efficient scale up of the process.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330514
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  • 189
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    Kinetics of whey-lactose acidogenesis (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 623-630 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The mixed-culture anaerobic conversion of lactose to organic acids in a bench-scale continuous-flow stirredtank fermentor is considered. The major acidogenic end-product distribution with respect to the dilution rate are presented. A Monod chemostat model is employed to describe a microbial growth, and the influence on pH of the estimated model parameters is discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330516
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  • 190
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    Multiple forms of endo-1,4-β-D-glucanase in the extracellular cellulase of Penicillium pinophilum (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 1242-1248 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of the composition of the growth medium on the production of endo-1,4-β-D-glucanase (CM-cellulase) activity by P. pinophilum was studied in shake flask cultures using Avicel PH101 as the carbon source. It was observed that the culture conditions had a profound effect on the level of endoglucanase (CM-cellulase) produced by P. pinophilum. However, isoelectric focusing of the endoglucanase activity obtained from shake flask and fermenter cultures using the same growth medium revealed that the enzyme system found in both cultures was identical qualitatively, and contained seven or eight different endoglucanase components. All the endoglucanase components appeared simultaneously in the early stages of culture and prolonged incubation resulted only in an increase in the concentration of these enzymes. Protease levels were found to be low in both types of culture but were particularly so in the growth medium which contained corn steep liquor. The proteases were unable to release low molecular weight peptides when P. pinophilum cellulase protein was used as a substrate. The results were interpreted to indicate that the multiplicity of endoglucanase components found in cultures of P. pinophilum is most likely the result of expression of a number of specific genes rather than by post-secretional modification of one or more endoglucanase(s) synthesized by the fungus.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260331004
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  • 191
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    Hydrolysis of lactose in skim milk by immobilized β-galactosidase in a spiral flow reactor (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 1249-1257 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: β-galactosidase from Aspergillus Oryzae immobilized in a spiral flow reactor was used to effect the hydrolysis of the lactose component of skim milk. Residence time distribution measurements were used to assess the amount of longitudinal dispersion occurring as a consequence of the spiral flow pattern and the semiporous nature of the polymeric material used to construct the spiral. It was possible to model the flow conditions as tubular flow with a Peclet number that was a linear function of the reactor space time. Nonlinear regression methods were used to determine the kinetic parameters of three proposed enzymatic rate expressions. The best fit of the data was obtained using a rate expression containing separate terms for competitive inhibition of the reaction by both the a and β anomers of galactose. This kinetic model also incorporates the kinetics of the mutarotation between these forms. At 30°C and a space time of 7 minutes, 80% of the lactose present in skim milk can be converted to glucose and galactose.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260331005
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  • 192
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    Expression of β-lactamase by recombinant Escherichia coli strains containing plasmids of different sizes - effects of pH, phosphate, and dissolved oxygen (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 34 (1989), S. 309-319 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The characteristics of growth and synthesis of plasmid-encoded protein were studied for strains of recombinant E. coli JM103 which carried the β-lactamase gene on plasmids of different sizes. The plasmids used included the vector pUC8 and its recombinant derivatives containing varying-sized inserts of Drosophila DNA (not expressed in E. coli). Luria broth (LB) and a minimal medium (M9) supplemented in some cases with additional inorganic phosphate were used as growth media. There was no evidence of segregational instability in these experiments, where no antibiotic selection pressure was employed. Responses of the recombinant strains to variations in environmental parameters including pH, phosphate concentration in the medium, and aeration rate were examined. While the cell growth rate in LB decreased with pH in the range 7.0-8.0, the bulk β-lactamase activity was maximized at an intermediate pH. The recombinant cell growth rate decreases with increasing plasmid size in the minimal medium, while such decrease is not significant when a rich medium such as LB is used. There is an intermediate plasmid size in the range studied (2.7-8.7 kb), at which β-lactamase activity is maximum. While reduction in aeration rate (which determines the dissolved oxygen level) is detrimental for cell growth, it is beneficial for β-lactamase synthesis. The bulk β-lactamase activity therefore exhibits a maximum with respect to aeration rate. Cell growth and β-lactamase production are affected in a similar manner by phosphate concentration in the minimal medium and therefore both are maximized at the same phosphate concentration. This investigation demonstrates clearly how the production of a recombinant plasmid-encoded protein can be maximized by proper manipulation of culture conditions and how it is affected by plasmid size.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260340306
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  • 193
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    Fermentation of D-xylose, D-glucose, L-arabinose mixture by Pichia stipitis: Effect of the oxygen transfer rate on fermentation performance (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 34 (1989), S. 398-402 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260340314
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  • 194
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    Masthead (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 34 (1989) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260340401
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  • 195
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    Removal of hydrogen sulfide from biogas by chemoautotrophic fixed-film bioreactor (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 34 (1989), S. 410-414 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260340317
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  • 196
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    Combined rapid-steam hydrolysis and organosolv pretreatment of mixed southern hardwoods (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 681-686 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Various types of pretreatments are used for biomass conversion of woods. The major objective of most pre treatments is to increase the susceptibility of cellulose and lignocellulose material to acid and enzymatic hydrolysis. In this study, southern mixed hardwoods were pretreated by combined rapid steam hydrolysis (RASH) and organosolv methods. It was found that the major factor in the pretreatment was the RASH temperatures. The organosolv temperature had only a minor effect on the reactivity of the final product. The enzymatic rate studies indicated that the RASH process helps in increasing the accessibility of cellulose to enzymatic hydrolysis and increased the amount of soluble lignin While the organosolv process only removed solubilized lignin. Another effect of the combined treatment was the decreasing of the enzymatic rate relative to a single RASH pretreatment. All hemicellulose is lost during these pretreatments. Three alcohols (methanol, ethanol, and butanol) were studied using a combined RASH organosolv process. At lower temperatures there were small differences between the alcohols; however, at higher temperatures all alcohols were equally effective. At longer RASH times, the percentage of glucose in the final product, as well as the amount of solubilized lignin, increased. However, the longer RASH times led to a decrease in enzymatic rates, Organosolv residence time studies of 15, 30, and 45 minutes displayed little effect on the product. Various wood-to-solvent ratios and water-to-alcohol ratios had very little effect on the yield of products. The stability of RASH treated material be fore organosolv process was studied under various storage conditions. The storage conditions had no apparent effect on the product.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330604
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  • 197
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    Kinetic model for the regulation of redox reaction in steroid transformation by Arthrobacter globiformis cells (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 668-680 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A kinetic model of hydrocortisone transformation was developed in studies of the kinetics of biochemical systems. The regulatory bases of the model are the biosynthesis of steroid-transforming enzymes and their activity, the level of endogenous substrates, the respiratory chain activity, and the initial concentrations of reagents. When compared, the experimental data completely coincide with the results of the computer modeling, the coincidence being not only qualitative but also quantitative. It indicates that the model suggested can be used for further studies of other transformations of steroid compounds, as well as for transformation of steroid compounds under close-to-biotechnological conditions. The results obtained by means of this model permit one to trace in dynamics the behavior of a number of parameters characterizing the process which is very difficult or not feasible to do in a biochemical experiment. The following was shown: (1) the behavior of the respiratory chain (the reversible transition of its oxidized and reduced forms); (2) the change of the transmembrane potential of hydrogen ions within a far larger stretch of time than is feasible to register in a biochemical experiment; (3) the regulation of the activity of 20β-hydroxysteroid dehydrogenase and 1, 2-reductase not only by the change in the level of endogenous substrates, but also by means of their biosynthesis; and (4) the regulatory role of 3-ketosteroid-1-en-dehydrogenase.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330603
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  • 198
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    An investigation of the efficacy of biological additives for the suppression of pyritic sulphur during simulated froth flotation of coal (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 694-698 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The biological molecule responsible for the suppression of pyritic sulfur in fine coal simulated froth flotation treated with bacteria was identified. Protein was found to be the most effective agent in pyrite suppression of the three cell components (protein, lipid, and carbohydrate) assayed. Coal recovery and ash removal of the flotation process were only slightly reduced by this treatment. Other protein-containing materials were evaluated for their ability to suppress pyrite flotation. Whey was found to be the most cost-effective flotation additive of those assayed. The sulfur content of the whey-treated float was reduced by 84.0% in a synthetically prepared fractionated coal (10.7% sulfur), by a raw whey dosage of 20 μL/g coal. The inorganic sulfur component of a natural high sulfur coal fraction (10.9%) was completely depressed by this whey addition. The effect of particle size and pulp density upon the process were investigated.
    Additional Material: 11 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330606
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  • 199
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    Osmotic, biomass, and oxygen effects on the growth rate of Fusarium oxysporum using a dissolved-oxygen-controlled turbidostat (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 699-705 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The system described is a modified Hospodka's turbidostat. This device helps to measure the maximum growth rate of fungi in steady-state aerobic conditions with defined and independent concentration of dissolved oxygen, biomass, and substrate even unlimited. The principle consists of a turbidostat controlled by the dissolved oxygen concentration. The inlet medium pump operates when the dissolved oxygen concentration falls below the set point value. This method allows us to study independently effects of different physical and chemical variables on the maximum specific growth rate of microorganisms. A fungus, Fusarium oxysporum 47 isolated from soil, does not show a depressive effect on growth when dissolved oxygen concentration decreases to 5% and osmotic potential to -25 bars. Increasing biomass concentration in the range 0.1-1.0 g/L appears to depress markedly the maximum growth rate.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330607
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  • 200
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    Studies of Saccharomyces cerevisiae during fermentation - an in vivo electrokinetic investigation (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 706-715 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An extensive in vivo study of the electrokinetic properties of six strains of the brewing yeast S. cerevisiae has been carried out. The yeasts were cultured under laboratory conditions. They were electrokinetically characterized by the electro-osmotic dipped cell technique, and data are presented as zeta-potentials. The effects of pH, fermentation time, successive fermentation cycles, and initial wort density have been established. The electrokinetic properties of an ale yeast which did not function correctly during commercial fermentation have also been examined. The results are discussed in the context of two controversial topics concerning the mechanism of yeast flocculation, the relative importance of yeast cell wall carboxyl and phosphate groups and the influence of wort components.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330608
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