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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 39 (1917), S. 1317-1319 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 39 (1917), S. 1322-1338 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 38 (1916), S. 2523-2527 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 143 (1996), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract In the light leaf spot fungus Pyrenopeziza brassicae, the kinetics of uptake of sucrose, glucose and fructose are all biphasic. At low and high concentrations, glucose and fructose share a high-affinity and a low-affinity hexose carrier respectively, with Kms of 3.5 and 4.6 μM for uptake of glucose and fructose respectively by the high-affinity system, and Kss of 690 and 750 uM for uptake of glucose and fructose by the low-affinity system. The data also suggest the existence of separate high-affinity and low-affinity uptake systems for sucrose. P. brassicae possesses both soluble and paniculate invertase activity, with pH optima of 5.0 and 4.0 respectively. Activity of the particulate invertase is considerably in excess of the highest rates of sucrose uptake.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 50 (1994), S. 385-395 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Quasi-elastic light scattering (QELS) was used to investigate quantitatively the mechanisms of nucleation, postnucleation growth, and dissolution in ensembles of both crystalline and amorphous aggregates of satellite tobacco mosaic virus (STMV), ferritin, apoferritin and pumpkin seed globulin. At low supersaturation conditions, as described previously for small molecule crystallization, the metastable region was obtained. Under these conditions aggregation took place, but crystallization did not proceed and critical nuclei did not form over a long period of time. The critical solution supersaturation necessary to obtain crystals, σ = ln(c/s) where c and s are concentration and solubility of protein, varied from ∼0.1 for pumpkin seed globulin to ∼0.9 for STMV. For higher supersaturation conditions when aggregation processes leading to formation of crystals are not established immediately but after a certain induction period, the supersaturation-dependent critical nuclear size, Rc, for different macromolecular systems was estimated from time-dependent size-distribution analyses to be in the range of ∼103 for proteins such as pumpkin globulin to approximately 10 for virus particles. From the same data, the molar interfacial free energy was deduced to be 3.3–9.2 kJ mol−1. These are believed to be among the first estimates for macromolecular crystals. Under conditions of moderate supersaturation where induction periods preceded the appearance of critical nuclei, the potential barriers for formation were estimated to be in the range 8.3–50 kJ mol−1. Growth and dissolution kinetics for pumpkin seed globulin were investigated. These experiments allowed determination of protein solubility versus solution temperature, protein and precipitant concentrations. Aggregation patterns which lead to crystal formation are distinctly different to those which produce an amorphous precipitate. The results provide additional evidence that QELS can be used to find general criteria that allow one to discriminate between conditions for a given protein system leading to crystalline or amorphous states at early stages of the aggregation process.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 52 (1996), S. 160-164 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The structure of a tetragonal crystal of bovine pancreatic RNase B complexed with d(pA)4 was determined by molecular replacement and difference Fourier methods. This crystal belongs to space group P41212 and has unit-cell dimensions a = b = 44.5, c = 156.5 Å. The model consists of the enzyme and a tetranucleotide with fractional occupancies, suggesting multiple modes of oligonucleotide binding. It does not include any polysaccharide residues or solvent molecules. After refinement at 2.7 Å, the R value was 0.163 with acceptable stereochemistry. The model illustrates a set of well defined interactions for substrate binding, particularly between the central dinucleotide and the enzyme.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 478-489 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Canavalin, the major reserve protein of the jack bean, was obtained in four different crystal forms. From the structure determined by multiple isomorphous replacement in a hexagonal unit cell, the structures of three other crystals were determined by molecular replacement. In two cases, the rhombohedral and cubic crystals, placement was facilitated by coincidence of threefold molecular symmetry with crystallographic operators. In the orthorhombic crystal the canavalin trimer was the asymmetric unit. The rhombohedral, orthorhombic and cubic crystal structures were subsequently refined using a combination of several approaches with resulting R factors of 0.194, 0.185 and 0.211 at resolutions of 2.6, 2.6 and 2.3 Å, respectively. Variation in the conformation of the molecule from crystal to crystal was small with an r.m.s. deviation in Cα positions of 0.89 Å. Packing is quite different among crystal forms but lattice interactions appear to play little role in the conformation of the molecule. Greatest variations in mean position are for those residues that also exhibit the greatest thermal motion. Crystal contacts in all crystals are mediated almost exclusively by hydrophilic side chains, and three to six intermolecular salt bridges per protein subunit are present in each case.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 50 (1994), S. 813-825 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Three crystal forms of the sweet-tasting protein thaumatin from the African berry Thaumatococcus daniellii have been grown. These include two naturally occurring isoforms, A and B, that differ by a single amino acid, and a recombinant form of isoform B expressed in yeast. The crystals are of space groups C2 with a = 117.7, b = 44.9, c = 38.0 Å, and β = 94.0°, P212121 with a = 44.3, b = 63.7 and c = 72.7 Å, and a tetragonal form P41212 with a = b = 58.6 and c = 151.8 Å. The structures of all three crystals have been solved by molecular replacement and subsequently refined to R factors of 0.184 for the monoclinic at 2.6 Å, 0.165 for the orthorhombic at 1.75 Å, and 0.181 for the tetragonal, also at 1.75 Å resolution. No solvent was included in the monoclinic crystal while 123 and 105 water molecules were included in the higher resolution orthorhombic and tetragonal structures, respectively. A bound tartrate molecule was also clearly visible in the tetragonal structure. The r.m.s. deviations between molecular structures in the three crystals range from 0.6 to 0.7 Å for Cα atoms, and 1.1 to 1.3 Å for all atoms. This is comparable to the r.m.s. deviation between the three structures and the starting model. Nevertheless, several peptide loops show particularly large variations from the initial model.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 50 (1994), S. 414-423 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Today the determination of successful crystallization conditions for a particular macromolecule remains a highly empirical process. Sparse-matrix and grid-screening procedures are rapid and economical means to determine preliminary crystallization conditions. During optimization the variable set (pH, precipitant type and precipitant concentration) utilized in these procedures is screened in an attempt to determine appropriate conditions for the nucleation and growth of single crystals suitable for X-ray diffraction analysis. Unfortunately, in many cases this strategy will not produce single crystals suitable for X-ray diffraction analysis. We have explored, in an empirical sense, other tools for use during optimization. First, a new screening protocol is evaluated which employs less classical precipitating agents. Second, a set of 24 electrostatic crosslinking agents are evaluated for their ability to promote crystallization. Third, a panel of more than 30 detergents are evaluated for their ability to prevent sample aggregation and influence crystal growth.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 50 (1994), S. 479-483 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Procedures are described for the crystallization of proteins, nucleic acids and viruses in a silica-gel matrix using otherwise standard reagents and conditions. Methods are given based on both vapor diffusion in a sitting drop and liquid–liquid diffusion. Using a variety of macromolecules our results suggest that the gel matrix suppresses nucleation, reduces the rate of growth, and generally leads to larger, higher-quality crystals of enhanced stability. Presumably these effects arise from the decreased mobility of the macromolecules and their flux at the crystal surface during growth.
    Type of Medium: Electronic Resource
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