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  • 1995-1999  (2,205)
  • 1995  (2,205)
  • Biochemistry and Biotechnology  (1,318)
  • Chemical Engineering  (730)
  • crystal structure  (158)
  • Nuclear reactions
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  • 1995-1999  (2,205)
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  • 1
    Electronic Resource
    Electronic Resource
    α-Iminohydroxylamine-α-aminonitrone tautomerism: a 1∶1 mixture of two tautomeric forms in crystals of N-(4,5-dihydro-1H-imidazol-2-yl)-N-phenyl-hydroxylamine (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 813-821 
    Details
    ISSN: 1572-8854
    Keywords: Tautomerism ; hydrogen bonding ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Crystals consisting of two distinct chemical entities, tautomers of each other, in exact 1∶1 ratio, have been obtained and their structure determined by X-ray analysis. The crystals of C9H11N3·C9H11N3 are monoclinic,P21/c,a=15.674(3),b=17.085(3),c=13.758(3)Å, β=90.78(2)°,Z=8. There are two hydroxylamine and two aminonitrone molecules in the asymmetric unit. Hydrogen bonds connect those molecules into chiral layers. Layers of opposite chirality alternate andthe crystal is centrosymmetric as a whole. Within those layers chains of tautomers joined by very strong O−H... O and strong N−H... N bonds can be recognized. Proton transfer along those chains with simultaneous rearrangement of π-bonds within the molecules would result in interconversion of tautomers and would affect chirality of the layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01671076
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  • 2
    Electronic Resource
    Electronic Resource
    Dialkylimidazolium-sodium chloroaluminate ternary salt system: phase diagram and crystal structure (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 57-62 
    Details
    ISSN: 1572-8854
    Keywords: phase diagram ; buffered chloroaluminate ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The phase diagram of the buffered neutral aluminum chloride + 1-ethyl-3-methyl-1H-imidazolium chloride + sodium chloride (AlCl3-EMIC-NaCl) ternary melt system can be represented by a binary phase diagram composed of (EMI)AlCl4 and NaAlCl4. In the binary phase diagram, the salts are liquid at, or near, room temperature for a wide range of compositions. At the 1∶1 composition, the congruently melting compound (EMI)(Na)(AlCl4)2 with m.p.=36.7°C is formed. Crystals of this mixed organic-inorganic salt were grown for single crystal x-ray diffraction analysis. The compound crystalizes in the space group $$P\bar 1$$ with lattice parametersa=10.321(1) Å,b=10.895(3) Å,c=9.284(4) Å, α=98.31(2)°, β=100.83(4)°, γ=101.95(3)°. Data collected at −120°C gave final residuals ofR=0.037 andR w=0.045 using 2713 observed reflections. The packing diagram reveals Na+ ion zig-zag chains running along thea-axis with each Na+ surrounded by four AlCl 4 − units, reminiscent of NaAlCl4. The AlCl 4 − ions form a distorted square planar coordination sphere around Na+ at an average Na−Al distance of 3.76(4) Å. Using a sodium ionic radius of 1.16 Å, a new AlCl 4 − ionic radius of 2.60 Å is calculated. This radius is 0.21 Å shorter than the reported thermodynamic radius.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01667037
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  • 3
    Electronic Resource
    Electronic Resource
    Antifungal copyrine alkaloids: crystal structure of 3-methylsampangine (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 223-226 
    Details
    ISSN: 1572-8854
    Keywords: Antifungal alkaloids ; 3-methylsampangine ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 3-Methylsampangine, C16H10N2O, crystallizes in the monoclinic space group P21/c witha=7.260(3),b=10.697(5),c=15.342(6) Å, and β=102.69(4). All nonhydrogen atoms of this potent antifungal agent are planar to within 0.082 Å. The title compound exhibits potentin vitro antifungal activity againstC. neoformans, C. albicans andA. fumigatus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665173
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  • 4
    Electronic Resource
    Electronic Resource
    Crystal structure of decacalcium tetrapotassium hexakis (pyrophosphate) nonahydrate (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 219-222 
    Details
    ISSN: 1572-8854
    Keywords: Calcium phosphate ; calcium pyrophosphate ; calcium potassium pyrophosphate ; crystal structure ; layer-type structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of Ca10K4(P2O7)6·9H2O has been determined by single crystal X-ray diffraction. Crystals are hexagonal, space group P63cm witha=11.761(1),c=9.770(1) Å, andZ=1. The structure was refined toR=0.028 andR w=0.037 for 468 reflections withI≥3σ(I). The structure consists of a compact assembly of Ca and P2O7 ions arranged in layers perpendicular to thec-axis in a hexagonal array with relatively large open channels along thec-axis. The K ions and the water molecules are located in these open channels and are disordered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665172
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  • 5
    Electronic Resource
    Electronic Resource
    Unusual occurrence of photooxidation of a cage diol (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 295-298 
    Details
    ISSN: 1572-8854
    Keywords: Cage-diol ; crystal structure ; photooxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An unusual photooxidation was noted upon photolytic cage closure of a substituted tricyclo[6.2.1.02.7]undecane-exo, exo-diol. The resultant compound, which may be regarded as a mono-reduced pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione, was characterizedvia X-ray crystallography. This species could be reduced to the tricyclo[6.2.1.02,7]undecane-endo, exo-diol under conditions previously shown to be inert for the parent dione.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01796053
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  • 6
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of 6,7-benzo-3,4 (1,4-dimethoxy-2,3-naphtho)-1,5-dioxosuberane (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 379-382 
    Details
    ISSN: 1572-8854
    Keywords: Benzonaphthodioxosuberane ; crystal structure ; radermachol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of the title compound (2) C21H16O4 has been determined by an X-ray analysis, by direct methods from diffractometer data and refined by full-matrix least squares. The compound (2) crystallizes in the space group P21/a, with cell parameters:a=36.432(5),b=5.512(3),c=8.269(5) Å, β=108.0(3)°,z=4,D c =1.397 g/cm−3,R=7.8 for 1136 observed reflections. The conformation of the tetracyclic ring system shows a folding of two planar parts of the carbon skeleton about an axis passing thorough C8 and C16 of the seven membered ring C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665273
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis and structural characterization of [Au2Pd14(μ3-CO)7(μ2-CO)2(PMe3)11](PF6)2—An icosahedrally-based high nuclearity mixed metal cluster (1995)
    Springer
    Journal of cluster science 6 (1995), S. 71-91 
    Details
    ISSN: 1572-8862
    Keywords: Palladium ; gold ; cluster ; phosphine ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract [Au2Pd14(μ3-CO)7(μ2-CO)2(PMe3)11](PF6)2 has been synthesized from [Pd8(CO)8(PMe3)7] and AuCl(PCy3) in the presence of TIPF6. It has been characterised on the basis of mass spectrometry, infrared and NMR spectroscopy, and a single crystal X-ray diffraction study. The structure is based on a palladium-centered Au2Pd11 icosahedron which shares an edge with a Pd5 trigonal bipyramid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01175837
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  • 8
    Electronic Resource
    Electronic Resource
    The synthesis and reactivity of the heptanuclear dianion [Os7(CO)20]2− including the synthesis and structural characterizations of the compounds [Os7(CO)20(AuPEt)3 2] and [Os8(CO)20(η6-C6H6] (1995)
    Springer
    Journal of cluster science 6 (1995), S. 163-173 
    Details
    ISSN: 1572-8862
    Keywords: Cluster carbonyl ; osmium ; gold ; arene ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Reduction of the heptaosmium cluster [Os7(CO)21] With [Et4N][NH4) gives the cluster dianion [Os7(CO)20]2−,1, in high yield. The reaction of the dianion with [AuPR 3Cl] (R=Et or Ph) in the presence of TlPF6 forms [Os7((CO)20(AuPR 3)2] [R=Et (2a);R = Ph(2b)] in 80% yield, while the corresponding reaction with (Os(C6H6)(CH3CN)3]2+ gives [Os8(CO)20 (η 6-C6H6)] (3) in reasonable yield (ca. 30%). The dianion,1, and the clusters2 and3 have been fully characterized by bout spectroscopic and crystallographic methods. The crystal structure of the [Ph4P]+ salt of1 shows that the metals in the anion adopt a capped octahedral geometry, with all twenty carbonyl ligands in terminal sites. The metal core geometry in2a is best described as a tricapped octahedron, and is based on the structure of the dianion1 with two adjacent octahedral faces capped by the Au atoms of the two AuPEt3 groups. In a similar fashion, the geometry of3 is related to that of1 with the addition of an Os(C6H6) unit capped to a triangular face, to give a bicapped octahedral framework.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01175843
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of the undecaosmium carbido carbonyl cluster: Crystal and molecular structures of [N(PPh3)2][Os11C(CO)27(μ-Cl)] (1995)
    Springer
    Journal of cluster science 6 (1995), S. 343-346 
    Details
    ISSN: 1572-8862
    Keywords: Undecaosmium carbido cluster ; µ-bridged chlorol preparation ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A chloro-derivative of undecaosmium carbido cluster [Os11C(CO)27(µ-Cl)]-1 anion has been prepared and fully characterized by spectroscopic and crystallographic methods. The structure1 is an important intermediate for the conversion of [Os11C(CO)27]2 2 dianion to [OS10C(CO)24]2-3 dianion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01169700
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis, chemical, and electrochemical characterization of the [Ag13{μ3-Fe(CO)4}] n− (n = 3, 4, 5) cluster anions: X-Ray structural determination of [N(PPh3)2]3 [Ag12(μ12-Ag){μ3Fe(CO)4}8]1 (1995)
    Springer
    Journal of cluster science 6 (1995), S. 107-123 
    Details
    ISSN: 1572-8862
    Keywords: Silver ; iron ; carbonyl ; cluster ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The oxidation of the [Fe(CO)4]2− dianion with Ag+ salts occurs through a particularinner-sphere mechanism, which involves an intermediate cascade of silver clusters stabilized by Fe(CO)4 ligands. The last detectable Ag-Fe cluster of the sequence is the [Ag13{μ-Fe(CO)4}8]3− trianion, which has been selectively obtained by using ca. 1.7 equivalents of Ag+ per mole of [Fe(CO)4]2−. The [Ag13{μ-Fe(CO)4}8]3−- trianion has been isolated in a crystalline state with several quaternary cations, and has been characterized by X-ray diffraction studies of its bis(triphenylphosphine)iminium salt. [N(PPh3)2]3 [Ag13{μ 3-Fe(CO)4}8]·2(CH3)2CO, monoclinic, space group P21 (No.4),a = 16.284(2) Å,b =18.767(5) Å,c = 25.905(4) Å,β = 90.46(1)°,V = 7916(3) Å3,Z = 2,R = 0.0324. The molecular structure of the anion consists of a centered cuboctahedron of silver atoms with the triangular faces capped by Fe(CO)4 units. Chemical reduction of ( Ag13{μ 3-Fe(CO)4}8]3− affords the corresponding [Ag13{μ 3-Fe(CO)4)8]4−, which in turn gives [Ag13{μ 3-Fe(CO)4)8]5− and [Ag6{μ 3-Fe(CO)4}4]– upon further reduction. Electrochemical investigations confirm the reversibility of the [Ag13{μ 3-Fe(CO)4}8]3−/4− redox change. Furthermore, in spite of some electrode poisoning effects, evidence of the existence of the [Ag13{μ 3-Fe(CO)4}8]5− pentaanion was obtained. The yet structurally uncharacterized [Ag6{μ 3-Fe(CO)4)4]2− dianion is quantitatively obtained by reaction of [Fe(CO)4]2− with ca. 1.5 equivalents of Ag+ or by addition of one equivalent of Ag+ to solutions of the [Ag5{Fe(CO)4}4]3− trianion. All attempts to isolate its quaternary salts as crystalline materials failed owing to formation of amorphous insoluble precipitates. The above series ofμ 3-Fe(CO)4 octa-capped cuboctahedral Ag13 clusters can be envisioned as the Ag+ . Ag and Ag− cryptates of the [Ag12{μ}3-Fe(CO)4}8]4− cryptand. respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01175839
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  • 11
    Electronic Resource
    Electronic Resource
    The synthesis and structural characterization of Os3(CO)8[Si(OMe)3][μ-PMe2(C6H4](μ-H)2: An unusual unsaturated triosmium cluster complex (1995)
    Springer
    Journal of cluster science 6 (1995), S. 437-447 
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    ISSN: 1572-8862
    Keywords: Osmium ; unsaturated cluster ; ortho-metallation ; siloxyl ligand ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The reaction of Os3(CO)10(NCMe)[Si(OMe)3](μ-H),1, with PMe2Ph yielded the new complex Os3(CO)10(PMe2Ph)[Si(OMe)3](μ-H),2 by substitution of the MeCn ligand with the phosphine ligand. When heated to 125°C compound2 was decarbonylated and transformed into the new unsaturated cluster complex Os3(CO)8[μ-PMe2(C6H4)][Si(OMe)3](μ-H)2,3 in 54% yield. Compound3 was characterized by a single crystal X-ray diffraction analysis, osmium bonds. The phenyl ring of the phosphine ligand has undergoneortho-metallation by a neighboring metal atom. A terminally coordinated Si(OMe)3 ligand is coordinated to the third osmium atom. The cluster is unsaturated by the amount of 2 electrons, and there is an open coordination site on the siloxyl substituted osmium atom that is partially filled by a weak interaction with one of the π-bonds of theortho-metalled phenyl ring. Complex3 reacts with CO at 1 atm to reform compound2 in 85% yield in 5 h at 40°C. Crystal Data: for3: space group = P21/n,a = 9.911(2) Å,b = 18.451(6) Å,c = 14.872(2) Å,β = 95.64(2)°,Z = 4, 1994 reflections,R = 0.028.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01165472
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  • 12
    Electronic Resource
    Electronic Resource
    Doubly-bridged binuclear complexes of oxomolybdenum(V) and oxotungsten(V) containing sexadentate ligands (1995)
    Springer
    Journal of cluster science 6 (1995), S. 549-566 
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    ISSN: 1572-8862
    Keywords: Molybdenum ; tungsten ; di-μ-oxo bridge ; sexadentate ligands ; asymmetric distortion ; stereoselectivity ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Binuclear oxomolybdenum(V) and oxotungsten(V) complexes of the type, [M 2(O)2(μ-X)(μ-X 1)]”, where M=Mo, W;X.X 1=O, S; L=edta, pdta (n=2-), tpen, tppn (n=2+) (edta4– =ethylenediaminetetraacetate(4–), pdta=R- orR,S-propylenediaminetetraacetate(4–), tpen=N,N,N 1,N1-tetrakis(2-pyridyhnethyl)-ethylenediamine, and tppn=R- orR,S-N,N,N 1,N1-tetrakis(2-pyridylmethyl)-propylenediami ne) are reviewed with respect to their preparation, structure, spectroscopic properties, reactivities, and in particular asymmetric distortion around the bicyclo [4.1.1 ] type core and stereoselectivity related to this distortion,
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01165773
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  • 13
    Electronic Resource
    Electronic Resource
    Comparison of the crystal structure and molecular models of N,N-diisobutyl-2-(octylphenylphosphinyl)acetamide (CMPO) (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 43-49 
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    ISSN: 1572-8854
    Keywords: Molecular mechanics ; molecular dynamics ; MNDO ; CMPO ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of N,N-diisobutyl-2-(octylphenylphosphinyl)acetamide, or CMPO was recently determined. The compound crystallizes in the space group P21/c witha=13.446(6),b=22.280(7),c=17.217(7) Å, β=92.07(4)°, andD calc=1.05 g/cm3 forZ=8 @20°C). Molecular mechanics, molecular dynamics, and MNDO calculations were also performed on CMPO utilizing the SYBYL1 suite of programs. The results from these calculations are compared to the crystal structure and to similar calculations performed on CMPO using ALCHEMY2,3. In general, the results from the calculations agree fairly well with the parameters from the crystal structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01666193
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  • 14
    Electronic Resource
    Electronic Resource
    Mercury(II) complex with terpyridine: structure of the 2∶1 solvate of [Hg(terpy)2](CF3SO3)2 with acetone (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 453-458 
    Details
    ISSN: 1572-8854
    Keywords: Mercury(II) terpyridine complex ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract [Hg(terpy)2](CF3SO3)2·0.5(CH3)2CO crystallizes in the triclinic $$P\bar 1$$ space group witha=14.631(6),b=15.258(4),c=18.785(7) Å, α=69.66(2), β=70.72(1), γ=88.55(1)°. The crystal structure consists of two independent [Hg(terpy)2]2+ cations, four trifluoromethanesulfonate anions and an acetone molecule in the asymmetric unit. Each mercury atom is coordinated by two tridentate terpyridine ligands forming an irregular six-coordination polyhedron. The Hg−N bond lengths range from 2.27(2) to 2.53(2) Å.
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    URL: http://dx.doi.org/10.1007/BF01665700
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  • 15
    Electronic Resource
    Electronic Resource
    Crystal structures of twoN-substituted 2-thioxo-1,3-dithiole-4-carboxamides (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 463-467 
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    ISSN: 1572-8854
    Keywords: 1,3-dithiole-4-carboxamides ; resonance effect ; short intramolecular S...O contact ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The two closely related compoundsN,N-dimethyl 5-(methylthio)-2-thioxo-1,3-dithiole-4-carboxamide1 andN-(p-methoxy-phenyl)-N-methyl 5-(methylthio)-2-thioxo-1,3-dithiole-4-carboxamide2 have been characterized by X-ray crystal structure determination. Crystal data for1: triclinic, $$P\bar 1$$ ,a=6.767(1),b=12.594(2),c=6.648(1) Å, α=101.38(1), β=93.37(2), γ=79.62(1)°,V=546.2 Å3,Z=2. Crystal data for2: monoclinic, Cc,a=19.836(4),b=6.057(1),c=15.860(3) Å, β=127.61(3)°,V=1509.5Å3,Z=4. The molecular structures of1 and2 show remarkable differences concerning the conformational behavior. These differences are related to the nature of the substituents at the nitrogen atom. The presence of an aromatic system in2 leads to an almost planar arrangement of the α-oxoketene dithioacetal moiety. This effect is accompanied by a short intramolecular S...O contact of 2.648(2) Å. In the absence of an aromatic system, as is the case for compound1, neither a resonance effect along the α-oxoketene dithioacetal fragment nor a short S...O distance is observed.
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    URL: http://dx.doi.org/10.1007/BF01665702
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  • 16
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    Electronic Resource
    The crystal structure of a heterobimetallic crown ether complex: [Na(dibenzo-18-crown-6)][FeCl4] (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 579-582 
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    ISSN: 1572-8854
    Keywords: Dibenzo-18-crown-6 ; hetero bimetallic ; crown ether ; crystal structure ; ferric chloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Slow evaporation of a solution of ferric chloride and dibenzo-18-crown-6 in 3∶1 CH3CN∶CH3OH produced single crystals of the title complex. This heterobimetallic crown ether complex, [Na(dibenzo-18-crown-6)][FeCl4], crystallizes in the monoclinic space group P2t/n with cell parameters (at 22°C)a=14.608(6),b=10.466(9),c=17.276(9)Å, β=91.47(6)°, andD calc=1.46 g cm−3 for Z=4. The structure consists of discrete ions with the shortest Na ... Cl distance a lengthy contact of 3.56(1)Å. The average Na...O separation is 2.69(3)Å. The [FeCl4]− anion exhibits a distorted tetrahedral geometry with an average Fe−Cl bond length of 2.16(2)Å.
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    URL: http://dx.doi.org/10.1007/BF01667027
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  • 17
    Electronic Resource
    Electronic Resource
    Nucleophilic additions of primary and secondary amines to pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 633-640 
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    ISSN: 1572-8854
    Keywords: Amines ; crystal structure ; pentacycloundecane-8,11-dione
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structures of three compounds formedvia nucleophilic attack of a heterocyclic secondary amine on PCU-8,11-dione, with the concomitant intramolecular attack of one keto oxygen on the carbon of the other ketone, are presented. In all three compounds, the bridging oxygen contains substantial p-character, and the bonds to the “attacking” nitrogen are significantly shorter than would be expected.
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    URL: http://dx.doi.org/10.1007/BF01665969
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  • 18
    Electronic Resource
    Electronic Resource
    X-ray structure of sesterterpene, 16β-acetoxy-24-methyl-12,24-dioxoscalaran-25-al (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 765-768 
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    ISSN: 1572-8854
    Keywords: Sesterterpene ; scalaran ; crystal structure ; marine compound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The molecular geometry of a tetracyclic sesterterpene has been determined by X-ray diffraction. The conformation of the aldehyde group as observed in the crystal structure supports the rationalization for the absence of aldehyde proton coupling in the nmr spectra of the compound. Crystal data: C28H42O5, M.W.=458.6; orthorhombic, P212121;a=10.797(2),b=29.270(9),c=8.033(1)Å,V=2538.7Å3,Dx=1.199 g cm−3;R=0.045 for 2287 observed reflections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01670333
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  • 19
    Electronic Resource
    Electronic Resource
    Synthesis of a chiral calixarene: 5,11,17,23-tetra (tert-butyl)-25,27-bis[((+)-camphor-10-sulfonyl)-oxy]-calix[4]arene-26,28-diol: crystal and molecular structure of its (1∶2) complex with toluene (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 401-406 
    Details
    ISSN: 1572-8854
    Keywords: Calixarene ; complex ; crystal structure ; chirality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound was obtained by treatment ofp-tert-butylcalix[4]arene with (+) camphorsulfonyl chloride in triethylamine and toluene. A (1∶2) complex with toluene has been found. Its structure has been determined by X-ray crystallography. Crystals are triclinic with space group P1,a=16.426(3),b=18.553(3),c=13.661(2) Å, α=94.78(2), β=110.76(2), γ=72.83(2)°,V=3720(2) Å3,d c =1.127 g/cm3 Z=2. Refinement based on 10495 observed reflections led to a finalR value of 0.100. The two independent molecules of calixarene in the asymmetric unit are in the cone conformation and the calixarene cavities are empty. The guest molecule occupies the interhost space. The norborane skelton of (+) camphorsulfonyl group is the same as ones found in literature. Only van der Waals interactions exist between the host and the guest molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665277
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  • 20
    Electronic Resource
    Electronic Resource
    Synthesis and structure of a seven electron triangular cluster complex [Mo3S4Cl3(dppe)2(PEt3] (1995)
    Springer
    Journal of cluster science 6 (1995), S. 523-532 
    Details
    ISSN: 1572-8862
    Keywords: Molybdenum ; reduction ; seven-electron triangular cluster ; bridging sulfide ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The triangular six-electron cluster complex [Mo3S4Cl4(PEt3) x (thf)5] produced by the excision reaction of Mo3S7Cl4 with triethypholsphine is reduced by magnesium at − 20°C. Subsequent addition of dppe (=1,2-his(diphenylphosphino)ethane) to the reduced species affords a seven-electron triangular cluster complex [Mo3S4Cl3(dppe)2(PEt3)]. The complex crystallizes in the space groupCm witha=17.170(6),b-19.878(6),c = 13.289(5)β = 121.73(2)°,V = 3858(2) A3, andZ = 2. The structure shows an almost equilateral triangle of three molybdenum atoms capped by a Sulfur atom and bridged by three sulfur atoms. The Mo Mo distances, ranging from 2.804(1) to 2.809(1) A are elongated ca. 0.04 A as compared with lose of a six-electron cluster complex with drape ligands. Two molybdenum atoms have a chlorine and a dppe ligands, and the other molybdenum atom bas a chlorine and a triethylphosphine ligands. The UV-Vis spectrum has a characteristic broad hand centered at 1410 n m, which is not observed for six-electron clusters. The ESR spectrum indicates the presence of an unpaired electron consistent with the formulation of the compound as a seven-electron cluster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01165771
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  • 21
    Electronic Resource
    Electronic Resource
    Linear and Nonlinear Optical Properties Of Racemic (±)2-(α-Methylbenzylamino)-5-Nitropyridine Single Crystals (1995)
    Springer
    Optical review 2 (1995), S. 128-131 
    Details
    ISSN: 1349-9432
    Keywords: organic crystal ; racemic form ; second-harmonic generation ; refractive index ; nonlinear optical coefficient ; crystal structure ; oriented-gas model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Linear and nonlinear optical properties of racemic (±)2-(α-methylbenzylamino)-5-nitropyridine ((±)MBANP) single crystals have been comprehensively investigated and compared with those of the enantiomorph (–)2-(α-methylbenzylamino)-5-nitropyridine ((–)MBANP) crystals. (±)MBANP crystal exhibits very high chemical and physical stability, but relatively small nonlinear optical coefficients (d31 = 6.8 pm/V, d32 = 4.7 pm/V, d33 = 0.84 pm/V). A comparison between the nonlinear optical coefficients of (±)MBANP and (–)MBANP demonstrates the validity of the oriented-gas model in molecular crystals that neglects all the contributions from intermolecular interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10043-995-0128-5
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  • 22
    Electronic Resource
    Electronic Resource
    The synthesis and X-Ray crystallographic analysis of a stable norbornadienone: 17-Oxo-7,16-methano-7,16-diphenylcyclopenta[d,e]tribenzo[a,h,j]anthracene (1995)
    Springer
    Structural chemistry 6 (1995), S. 167-173 
    Details
    ISSN: 1572-9001
    Keywords: MM3 ; PM3 ; MMX ; crystal structure ; norbonadienone ; distorted compound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The reaction of 4,5-didehydroacenaphthene with phencyclone yields the title compound, a stable dibenzo-fused norbornadienone (8). The X-ray structure of8 is presented and compared with the structure predicted from a MM3, PM3, and a MMX calculation. Thermal decomposition of 8 produces, 7,16-diphenylcyclopenta[d,e]tribenzo[a,h,j]anthracene (9), a hydrocarbon that is computed to have a significantly twisted polycyclic aromatic skeleton with 19 kcal/mole of strain energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02286444
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  • 23
    Electronic Resource
    Electronic Resource
    Molecular Structure of 5-Methylchrysene-7,8-dihydro-7,8-trans-(e, e)-diol (1995)
    Springer
    Structural chemistry 6 (1995), S. 57-63 
    Details
    ISSN: 1572-9001
    Keywords: Hydrogen bonding ; carcinogen ; polycyclic aromatic hydrocarbon derivative ; dihydrodiol ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystal structure of the weak carcinogen 5-methylchrysene-7,8-dihydro-7,8-trans-(e,e)-diol is reported. This molecule contains a distorted bay region as a result of the presence of the 5-methyl group as found in 5-methylchrysene and 5,6- and 5, 12-dimethylchrysene. One torsion angle in this bay region is 20
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263528
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  • 24
    Electronic Resource
    Electronic Resource
    Synthesis and structure of 13- and 26-membered crown ethers, derivatives of resorcinol (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 2353-2360 
    Details
    ISSN: 1573-9171
    Keywords: resorcinol-based crown ethers ; crystal structure ; intramolecular nonbonded C-H...O contacts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 13- and 26-Membered crown ethers have been synthesized based on resorcinol and 1,8-dichloro-3,6-dioxaoctane. The products with substituents in the benzene ring have been prepared by alkylation of 13-membered crown ether. Complexing properties of the macrocycles have been studied with the use of ion-selective membrane electrodes. The structures of 13- and 26-membered crown ethers have been established by X-ray structural analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00713607
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  • 25
    Electronic Resource
    Electronic Resource
    Oxidation of 1-hydrazino-3,3-dimethyl-3,4-dihydroisoquinoline. X-ray, spectroscopic, and quantum-chemical study of the structure of 3,3-dimethyl-3,4-dihydroisocarbostyryl azine (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 2364-2370 
    Details
    ISSN: 1573-9171
    Keywords: dihydroisoquinoline derivatives ; crystal structure ; electronic, IR, and1H NMR spectra ; quantum-chemical calculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 3,3-Dimethyl-3,4-dihydroisocarbostyryl azine (2) has been synthesized by oxidation of l-hydrazino-3,3-dimethyl-3,4-dihydroisoquinoline (1). The crystal and molecular structures of compound 2 were determined. It has been established that in the solid state, compound2 exists as an azine tautomer. The IR, electronic, and NMR spectral data indicate that in solution the tautomeric form of2 does not change. A possible mechanism of the oxidation of1 to2 is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00713609
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  • 26
    Electronic Resource
    Electronic Resource
    Crystal Structure of 2-Debenzoyl, 2-Acetoxy Paclitaxel (Taxol®): Conformation of the Paclitaxel Side-Chain (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 337-341 
    Details
    ISSN: 1573-904X
    Keywords: 2-debenzoyl, 2-acetoxy paclitaxel ; docetaxel ; paclitaxel side-chain ; crystal structure ; solid state conformation ; intramolecular hydrogen bonding ; intermolecular hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Crystals of the C2-acetate analog of paclitaxel, grown from a mixture of isopropyl alcohol and methanol, belong to the space group P2l with a = 9.058(3), b = 18.306(5), c = 15.043(1) Å, β = 97.09(1)°, Z = 2, V = 2475.1(9)Å3, D calc = 1.269 gcm−3 and µ = 0.75 cm−1. The structure was determined by direct methods and refined to R(F) = 0.054 and wR(F) = 0.057 for 605 variables and 3496 observed reflections. The paclitaxel side chain possesses a conformation similar to that observed in the crystal structure of docetaxel (Taxotere®). A three dimensional network of hydrogen bonds is formed through solvent molecules and stabilizes the crystal lattice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016236014766
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  • 27
    Electronic Resource
    Electronic Resource
    Structure ofp-tetrakis-(4-nitrophenylazo)calix[4]-arene-4-picoline (1∶4) complex (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 22 (1995), S. 33-40 
    Details
    ISSN: 1573-1111
    Keywords: Calixarene-dye ; crystal structure ; inclusion compound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The structure of thep-tetrakis-(4-nitrophenylazo)calix[4]arene-4-picoline (1∶4) complex has been determined by X-ray crystallography. Crystals are monoclinic, space groupC2/c,a=24.9097) Å,b=8.425(6) Å,c=33.81(1) Å, β=101.13(2)°,D c =1.330 g/cm3,Z=4, finalR value =0.067. The cone conformation adopted by this azocalixarene is disturbed by the positions of the picoline molecules. Two of them are inside the macorocycle cavity and the two others are outside.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00706496
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  • 28
    Electronic Resource
    Electronic Resource
    New synthesis and complexing properties ofp-tert-butyldihomooxacalix[4]arene. Structure of its 1∶2 complex with tetrahydrofuran (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 22 (1995), S. 119-130 
    Details
    ISSN: 1573-1111
    Keywords: Calixarene ; complexation ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new method is described for the synthesis of isolatedp-tert-butyldihomooxacalix[4]arene (CALO) with a 24% yield. The ability of CALO to form complexes in the solid state with small neutral molecules has been studied; the potential guests were common solvents bearing various chemical functions. The powder obtained after evaporation of the solvent has been characterized by the X-ray powder diffraction technique. Analysis of the patterns shows the non-complexation of linear alkanes and alcohols, but formation of complexes when the guest is cyclic or when it bears an amine or a ketone function. As illustration of the possible arrangement of molecules in complexes, the structure of the 1:2 complex with tetrahydrofuran (THF) is presented: the crystals are monoclinic, space groupP21/c,a=9.459(2) Å,b=17.286(2) Å,c=30.469(6) Å, β=92.52(2)o,V=4977(2) Å3,Z=4,D c=1.099 Mg m−3, λ=1.54178 Å, μ=5.6 cm−1,R=0.086 for 3590 reflections withF〉4σ (F); one of the THF molecules is inside the cavity of the macrocycle, while the other, in the interhost space, exhibits disorder. In the CALO molecule, three out of the fourtert-butyl groups are disordered which may induce the disorder of the THF molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00707687
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  • 29
    Electronic Resource
    Electronic Resource
    Inclusion compounds of (±) gossypol. Structure of the gossypol-n-valeric acid (1/2) coordinato-clathrate (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 22 (1995), S. 187-201 
    Details
    ISSN: 1573-1111
    Keywords: Inclusion compounds ; gossypol ; crystal structure ; hydrogen bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystal structure of the inclusion compound of gossypol withn-valeric acid as a guest molecule has been determined by X-ray structure analysis. The crystals of C30H30O8·(C5H10O2)2, are triclinic, space group $$P\bar 1$$ ,a=6.912(2),b=14.506(3),c=19.387(4) Å, α=78.85(2)°, β=83.92(3)°, γ=86.78(3)°V=1895(1) Å3,Z=2,D x=1.267 g cm−3, μ (CuK α)=0.768 mm−1,T=292 K. The structure has been solved by direct methods on intensity data collected for a twinned crystal and refined to the finalR value of 0.062 for 1606 observed reflections and 470 refined parameters. Gossypol-n-valeric acid (1/2) coordinato-clathrate is not isostructural with any of the previously investigated gossypol inclusion compounds but shows some structural similarities to gossypol-acetic acid (1/1). The host and one of the carboxylic acid molecules are connected via hydrogen bonds into molecular assemblies of a column type which are further bonded to centrosymmetric dimers of the secondn-valeric acid molecule. In effect, host and guest molecules are assembled into layer-type H-bonded aggregates. Structural features common to gossypol-n-valeric acid (1/2) and other earlier reported gossypol inclusion compounds are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00707082
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  • 30
    Electronic Resource
    Electronic Resource
    Lattice dynamics of (Ba/K)BiO3 (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 595-598 
    Details
    ISSN: 1572-9605
    Keywords: (Ba/K)BiO3 ; lattice dynamics ; electron phonon coupling ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The Lattice dynamics of Ba.6K.4BiO3 was investigated by inelastic neutron scattering on a superconducting single crystal (T c =26 K (midpoint)). At low frequencies the dispersion curves are very similar to those observed in BaPb.75Bi.25O3. Differences were found in the bond bending vibrations of the BiO6 octahedra which indicate that the binding in the K-doped compound is more ionic. Rather anomalous features were observed in the high frequency Bi-O bond stretching vibrations which resemble those observed in the high T c cuprates La1.85Sr.15CuO4 and YBa2Cu3O7. The observed frequency shifts are interpreted as the consequence from a strong electron phonon coupling. The data are compared to the results obtained on non superconducting Ba.98K.02BiO3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00727434
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  • 31
    Electronic Resource
    Electronic Resource
    Compatibility of poly(ethylene 2,6-naphthalate) and poly(butylene 2,6-naphthalate) blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1807-1810 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blends prepared from poly(ethylene 2,6-naphthalate) (PEN) and poly(butylene 2,6-naphthalate) (PBN) show only partial miscibility judged from their glass transition temperatures. Two distinct mechanical behaviors are observed: brittle for the blends 〈 20 wt% of PBN, while ductile 〉 20 wt% of PBN. The experimental modulus and strength values of the blends are within the predicted values according to Kleiner and Paul models, respectively. This means that PEN/PBN blends are somewhat compatible based on their tensile properties. Especially for 20 wt% of PBN blend, the high modulus and strength are observed. The viscosity of the blend is high, which may imply a somewhat entangled morphology in the amorphous state.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352210
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  • 32
    Electronic Resource
    Electronic Resource
    Masthead (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352301
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  • 33
    Electronic Resource
    Electronic Resource
    Effects of mixing porcedures on properties of compatibilized polypropylene/nylon 6 blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1821-1833 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The paper consides the effects of compatibilization with maleic anhydride grafted polypropylene (PP-g-MAH) on the propertie of immiscible blends of polypropylene (PP) and nylon 6 (N6). We prepared the blends by three different mixing processes; single-step blending, two-step blending with reactive premixing, and two-step blending with nonreactive premixing, to determine the effective mixiing process for fine morphological structure thermal stability, and mechanical properties. Dynamic melt reheological properties were measured to examine the modification of elastic properties by the compatibilizer. In addtion, thermal analysis was also carried out to detect the change in crystallization and thereby to probe the degree of compatibilizaton. The results show that compatibilized blends prepared by teh single-step process exhibit improved phase morphology, thermal stability, and mechanical properties for dried conditions, compared with other blend types. Finally, the water absorption test indicates that the added compatibilizer yields enhanced water resistance in spite of the strong intrinsic hydrophilicity of N6. In particular, two-step blending with reactive premixing is most effective in improving water resistance and reducing degradation of mechanical properties after moisture absorption.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352302
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  • 34
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    Electronic Resource
    A hybrid numerical technique to model 3-D flow fields in resin transfer molding processes (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1834-1851 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A hybrid two-/three-dimensional solution technique is presentedto model 3-D flow fields in resin transfer moeling using Darcy's low. The 3-D flow field is only solved for regions where all three velocity components are significant, thus largely reducing the number of unknowns. Elsewhere, the commonly used 2-D approximation for flow in thin gaps between plates is employe.d The method is applied to regions where the flow splits, such as T-joints. Because of the uncertainties associated with an accurate determination of the permeability in these regions, a simplified decompled procedure is procesed, which reduces the computational complexity. In this procedure, the flow front is advanced using the 2-D formulation. The 2-D formulation also provides the boundary conditions for the subsequent computation of the 3-D flow field without feedback of flow field information to the 2-d model. The governing equations are solved using boundary fitted coordinate systems (BFCS) together with the finite difference method (FDM). Numerical as well as algebraic grid generation and domain decomposition are employe dto generate grids that always concide with the continuously deforming and enlarging flow domain. Results that include the trackingof numerical tracer particles to visualize the three-dimensionality of the flow field are presented for isothermal flow of a Newtonian fluid through a T-joint. This detailed flow field description is expected to form the basis for a rather accurate simulation of quantitities that largely depend on the fluid particle pathlines, such as the degree of cure. The method is also extendable to shear-thinning fluids as well as to 3-D flow in the vicinity of the flow front.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352303
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  • 35
    Electronic Resource
    Electronic Resource
    Theory of competition between breakup and coalescence of droplets in flowing polymer blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1872-1877 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The Smoluchowski equation for the breakup and coalescence of dispersed droplets has been solved for flowing polymer blends. A scaling form for the distribution of droplet sized derived and published for a system of clusters with fragmentation and coagualation was used in our dervation. Equations are developed here for the average droplet size and for the characteristic time of transition to steady state flow of blends with a high content of the dispersed phase. Expressions reasonably describing the average size of droplets for all concentrations were obtained by a theory modification. Measured dependences of droplet size on the blend composition can be matched only if simultaneous collisions of three and more droplets are considered. The results of the theory indicate that the mechanism of droplet breakup (formation of pieces with the same or different volumes) has only a small effect on their average size in concentrated systems. The dependence of droplet size on the shear rate in flow is determined by properties of the blend components, and is generally nonmonotonic.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352306
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  • 36
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    Performance of reprocessed multilayer LDPE/nylon-6 film (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1878-1883 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Multilayer LDPE/nylon-6 films with an overall content of 71 wt% LDPE, 24 wt% nylon-6, and 5 wt% PE-based tie-layer adhesive were reprocessed under both minimal and extensive mixing conditions. Thermal and mechanical properties, oxygen and water vapor permeability, and morphology of the reprocessed samples were determined. The modulus and yield stress of the reprocessed films fell between those of the pure homopolymers, whereas percent elongation at break and energy-to-break for all reprocessed films were less than those of the homopolymers. In minimally reprocessed film, layering of LDPE (low-density polyethylene) and nylon-6 was retained, whereas in extensively mixed samples, nylon-6 domains were spherical and ranged from 0.2 to 7 μm. Minimally reprocessed film exhibited good O2 and H2O vapor barrier properties, whereas extensively-mixed samples had poor barrier properties. Properties of well-mixed blends prepared both with and without adhesive showed that 5 wt% adhesive did not compatibilize the LDPE and nylon-6 components.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352307
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  • 37
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    Electronic Resource
    Assessment of residual stresses during cure and cooling of epoxy resins (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1895-1898 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new stress monitoring technique, a stress-tracking device, is described here. It has been used to study some important properties of epoxy resin. Residual stresses, including a curing shrinkage stress and a cooling shrinkage stress, were measured automatically and continuously during curing and cooling. Simultaneously, information such as an apparent gelation time and glass transition temperature were obtained directly during the experiment. These epoxy resin properties were related to the extent of cure. Varying cure temperature produced changes of cure behavior, which resulted in different residual stresses.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352309
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  • 38
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    Electronic Resource
    Study of reaction injection molding of polyurethane microcellular foam (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1899-1906 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Processing of microcellular foam was investigated for the feasibility of production of tough and lightweight polyurethanes. To increase the nucleation rate in a gas-supersaturated resin, ultrasonic excitation was applied to the mixture of polyol(polyether-based polyol) and isocyanate(diphenyl methane diisocyanate). A microcellular structure was produced by two sequential steps, i.e., supersaturationof the polyol resin with nitrogen gas at elevated pressure and ultrasonic bubble nucleation right after the impingement mixing of two components of the polyurethane system. Theoretical analyses based on nucleation theories were employed to predict the rate of nucleation in the gas-supersaturated polyurethane. The rate of nucleatio in the resin was predicted by classical nucleation and cluster theories. In the experimental investigation, ultrasonic excitation was applied to increase the nucleation rate in the resin that had been saturated by nitrogen at a saturation pressure 〈 2.0 MPa.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352310
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    Electronic Resource
    Modeling the mechanical properties in polypropylene/polyamide-6 blends with core shell morphology (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1917-1922 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polypropylene/Polyamide-6 (PP.PA) blends containing maleic anhydride grafted elastomers were prepared by reactive blending. Three different types of core shell morphologies were obtained and characterized by transmission electron microscopy (TEM). The midulus of these elastomer midified PP/PA (70/30) blends with core shell type morphology is compared to predictions derived from the Kerner model. The multiphase morphology of these blends could be modeled by sequential application of the Kerner equation to two-phase subinclusions. Using morphological data ontained by TEM, good agreement between experimental and calculated values was ontained. The results are used to tailor PP/Pa-6 blends combining stiffness and toughness.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352402
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    Electronic Resource
    Creep analysis of thermiplastics using stress relaxation data (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1931-1937 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: One of the major factors limiting the use of thermoplastics in engineeing applications is the inadequacy of existing design data. Much of the data do not span appropriate ranges of stress, strain, time, or temperature. This study addresses the need to develop an accelerated method for generating long-time design data to support the innovative use of engineering thermoplastics. In particular, stress relaxation tests (SRT) were performed on polycarbonate (PC) and midified poly(phenylene oxide)(PPO), and used to generate time-dependent design data through the short-time measurement of the material's current state without dependence on elastic modulus. The test results and analyses reported here indicate the SRT method to be an efficeint means of generating accurate and repeatable creep and secant modulus data which may be directly used in design. Therefore, SRT shows great potential both as a design parameter development tool, and as a quality control instrumetn for assessing batch-to-batch variability.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760352404
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    Electronic Resource
    Adaptive on-line model for aerobic Saccharomyces cerevisiae fermentation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 631-638 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; fermentation ; on-line simulation ; state estimation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to study and control fermentation processes, indirect on-tine measurements and mathematical models can be used. In this article we present a mathematical on-line model for fermentation processes. The model is based on atom and partial mass balances as well as on equations describing the acid-base system. The model is brought into an adaptive form by including transport equations for mass transfer and unstructured expressions for the fermentation kinetics. The state of the process, i.e., the concentrations of biomass, substrate, and products, can be estimated on-line using the balance part of the model completed with measurement equations for the input and output flows of the process. Adaptivity is realized by means of on-line estimation of parameters in the transport and kinetic expressions using recursive regression analysis. These expressions can thus be used in the model as valid equations enabling prediction of the process. This makes model-based automation of the process and testing of the validity of the measurement variables possible. The model and the on-line principles are applied to a 3.5-L laboratory tormentor in which Saccharomyces cerevisiae is cultivated. The experimental results show that the model-based estimation of the state and the predictions of the process correlate closely with high-performance liquid chromatography (HPLC) analyses. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480611
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    Kinetics of chlorinated ethylene dehalogenation under methanogenic conditions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 659-666 
    Details
    ISSN: 0006-3592
    Keywords: methanogenic activity ; ethylene ; dechlorination ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Kinetics were determined for methanogenic activity and chlorinated ethylene dehalogenation by a methanol-enriched, anaerobic sediment consortium. The culture reductively dechlorinated perchloroethylene (PCE) to trichloroethylene (TCE), 1,1-dichloroethylene (1,1-DCE), vinylchloride (VC), and ethylene and ethane. The absence : of methanol or the addition of 2-bromoethanesulfonic. acid in the presence of methanol suppressed both methanogenic activity and dechlorination. In contrast, acetate production continued in the presence of 2-bromoethanesulfonic acid. These results suggest that dechlorination was strongly linked to methane formation and not to acetate production. A kinetic model, developed to describe both methanogenesis and dechlorination, successfully predicted experimentally measured concentrations of biomass, methane, substrate, and chlorinated ethylenes. The average maximum specific dehalogenation rates for PCE, TCE, 1,1-DCE, and VC were 0.9 ± 0.6, 0.4 ± 0.1, 12 ± 0.1, and 2.5 ± 1.7 μmol contaminant/ g. DW/day, respectively. This pattern for dechlorination rates is distinctly different than that reported for transition metal cofactors, where rates drop by approximately one order of magnitude as each successive chlorine is removed. The experimental results and kinetic analysis suggest that it will be impractical to targeting methanol consuming methanogenic organisms for in situ ground-water restoration. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260480614
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    Enhancement of antibody production by growth factor addition in perfusion and hollow-fiber culture systems (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 673-680 
    Details
    ISSN: 0006-3592
    Keywords: bovine serum albumin ; growth factor ; hollow-fiber culture ; perfusion culture ; antibody production rate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of the high-molecular-weight growth factors, transferrin and bovine serum albumin (BSA), on antibody production were analyzed quantitatively in continuous hollow-fiber cultivation over a period of 60 days. Transferrin enhanced cell growth but had no significant effect on the specific antibody production rate, whereas BSA significantly enhanced antibody production. The antibody production rate was increased 4- and 14-fold respectively by feeding BSA at 2 and 5 g L-1 into the EC side of the system (the side connected to the cell-containing outer part of the hollow-fiber unit) compared with the production achieved without BSA. Addition of 5 g L1 BSA into the IC side of the system (the side connected to the inner part of the hollow-fiber unit) resulted in a 2.5-fold increase in the antibody production rate. The effect of BSA was also analyzed using the perfusion culture system with a separation unit. When fresh medium containing either 2 or 5 g L-1 BSA was fed into the reactor, both the specific growth rate and specific death rate increased, while the specific antibody production rate was increased 2- and 25-fold, respectively, by feeding BSA at these two concentrations compared with no addition. Comparing the two systems, the increase in the antibody production rate achieved with the hollow-fiber system was threefold greater than that in the perfusion culture system with the same concentration of BSA feeding. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260480616
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    Electronic Resource
    Empirical evaluation of the influence of side chains on the conformational entropy of the polypeptide backbone (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 132-140 
    Details
    ISSN: 0887-3585
    Keywords: protein folding ; protein stability ; mutational effects ; φ, ψ distribution ; Ramachandran map ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Changes in amino acid side chains have long been recognized to alterthe range and distribution of φ, ψ angles found in the main chain of polypeptides. Altering the range and distribution of φ, ψ angles also alters the conformational entropy of the flexible denatured state and may thus stabilize or destabilize it relative to the comparatively conformationally rigid native state. A database of 12,320 residues from 61 nonhomologous, high resolution crystal structures was examined to determine the φ, ψ conformational preferences of each of the 20 amino acids. These observed distributions in the native state of proteins are assumed to also reflect the distributions found in the denatured state. The distributionswere used to approximate the energy surface for each residue, allowing the calculation of relative conformational entropies for each residue relative to glycine. In the most extreme case, replacement of glycine by proline, conformational entropy changes will stabilize the native state relative to the denatured state by -0.82 ± 0.08 kcal/mol at 20°C. Surprisingly, alanine is found to be the most ordered residue other than proline. This unexpected result is a result of the high percentage of alanines found in helical conformations. This either indicates that the observed distributions in the native state do not reflect the distributions in the denatured state, or that alanine is much more likely to adopt a helical conformation in the denatured state than residues with longer side chains. Among those residues with φ, ψ angles compatible with helix incorporation the percentage of alanines actually in helices is very similar to other residues. This and the consistent ordering of alanine relative to other residues regardless of secondary structure are evidence that φ, ψ distributions in native states reflect those in the denatured states. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220206
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    Molecular dynamics simulations of rubredoxin from Clostridium pasteurianum: Changes in structure and electrostatic potential duringredox reactions (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 154-167 
    Details
    ISSN: 0887-3585
    Keywords: iron-sulfur proteins ; electron transfer ; oxidation-reduction potentials ; solvent accessibility ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Molecular dynamics simulations of Clostridium pasteurianum rubredoxin in the oxidized and reduced forms have been performed. Good agreement between both forms and crystal data has been obtained (rms deviation of backbone atoms of 1.06 and 1.42 Å, respectively), which was due in part to the use of explicit solvent and counterions. The reduced form exhibits an unexpected structural change: the redox site becomes much more solvent-accessible, so that water enters a channel between the surface and the site, but with little actual structural rearrangement (the rms deviation of backbone atoms between the oxidized and reduced is 0.77 Å). The increase in solvent accessibility is also seen, although to a much lesser extent, between the oxidized and reduced crystal structures of Pyrococcus furiosus rubredoxin, but no high resolution crystal or nuclear magnetic resonance solution data exist for reduced C. pasteurianum rubredoxin. The electrostatic potential at the iron site and fluctuations in the potential, which contribute to both the redox and electron transfer properties, have also been evaluated for both the oxidized and the reduced simulations. These results show that the backbone plays a significant role (62-70 kcall/mol/e) and the polar sidechains contribute relatively little (0-4 kcal/mol/e) to the absolute electrostatic potential at the iron of rubredoxin for both forms. However, both groups contribute significantly to the change in redox state by becoming more polarized and more densely packed around the redox site upon reduction. Furthermore, these results show that the solvent becomes much more polarized in the reduced form than in the oxidized form, even excluding the penetrating water. Finally, the simulation indicates that the contribution of the charged side chains to the electrostatic potential is largely canceled by that of the counterions. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220208
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    Crystallization of UDP-N-acetylglucosamine O-acyltransferase from Escherichia coli (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 191-192 
    Details
    ISSN: 0887-3585
    Keywords: lipopolysaccharide ; lipid A ; endotoxin ; protein structure ; acyltransferase ; X-ray crystallography ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Crystals of UDP-N-acetylglucosamine O-acyltransferase (lpxA) fromEscherichia coli have been obtained from solutions of sodium/potassium phosphate and dimethylsulfoxide. These crystals belong to the cubic space group P213 (a = 99.0 Å), diffract X-raysto approximately 2.5 Å resolution and contain one subunit of the enzyme in the asymmetric unit. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220212
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  • 47
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    Comparison of the effects of hydrophobicity, amphiphilicity, and α-helicity on the activities of antimicrobial peptides (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 182-186 
    Details
    ISSN: 0887-3585
    Keywords: hydrophobic moment ; peptide-cell ; membrane interactions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Multiple linear regression was used to quantify the dependence of the antimicrobial activity of 13 peptides upon three calculated or experimentally determined parameters: mean hydrophobicity, mean hydrophobic moment, and α-helix content. Mean hydrophobic moment is a measure of the amphiphilicity of peptides in an α-helical conformation. Antimicrobial activity was quantified as the reciprocal of the measured minimal inhibitory concentration (MIC) against Escherichia coli. One of the peptides was magainin 2, and the remainder were novel peptides designed for this study. The multiple linear regression results revealed that the amphiphilicity of the peptides was the most important factor governing anti-microbial activity compared to mean hydrophobicity orα-helix content. A better regression cf the data was obtained using In(1/MIC + constant) as the dependent variable than with either 1/MIC or In(1/MIC). These results should be useful in designing peptides with higher antimicrobial activity. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220210
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  • 48
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    Exploring the binding preferences/specificity in the active site of human cathepsin E (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 168-181 
    Details
    ISSN: 0887-3585
    Keywords: aspartic proteinase ; enzyme kinetics ; rule-based model ; chromogenic assay ; synthetic substrate ; inhibitor ; molecular modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Aspartic proteinases are produced in the human body by a variety of cells. Some of these proteins, examples of which are pepsin, gastricsin, and renin, are secreted and exert their effects in the extracellular spaces. Cathepsin D and cathepsin E on the other hand are intracellular enzymes. The least characterized of the human aspartic proteinases is cathepsin E. Presented here are results of studies designed to characterize the binding specificities in the active site of human cathepsin E with comparison to othermechanistically similar enzymes. A peptide series based on Lys-Pro-Ala-Lys-Phe*Nph-Arg-Leu was generatedto elucidate the specificity in the individual binding pockets with systematic substitutions in the P5- P2 and P2′-P3′ based on charge, hydrophobicity, and hydrogen bonding. Also, to explore the S2 binding preferences, asecond series of peptides based on Lys-Pro-Ile-Glu-Phe*Nph-Arg-Leu was generated with systematic replacements in the P2 position. Kinetic parameters were determined forboth sets of peptides. The results were correlated to a rule-based structural model of human cathepsin E, constructed on the known three-dimensional structures of several highly homologous aspartic proteinases; porcine pepsin, bovine chymosin, yeast proteinase A, human cathepsin D, andmouse and human renin. Important specificity-determining interactions were found in the S3 (Glu13) and S2 (Thr-222, Gln-287, Leu-289, Ile-300)subsites. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220209
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    Masthead (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995) 
    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.340220301
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  • 50
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    Crystallization, characterization, and preliminary crystallographic studies of mitochondrial carbamoyl phosphate synthetase I of Rana catesbeiana (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 193-196 
    Details
    ISSN: 0887-3585
    Keywords: urea cycle ; frog ; liver ; carbamyl phosphate synthetase ; X-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Carbamoyl phosphate synthetase I (ammonia; E C 6.3.4.16) was purified from the liver of Rana catesbeiana (bullfrog). Crystals of the protein have been obtained at 22°C by the hanging drop vapor diffusion technique, with polyethylene glycol as precipitant. Tetragonal crystals of about 0.3 × 0.3 × 0.7 mm diffract at room temperature to at least 3.5 Å using a conventional source and are stable to X-radiation for about 12 h. Therefore, these crystals are suitablefor high resolution studies. The space group is P41212 (or its enantiomorph P43212), with unit cell dimensions a = b = 291.6 Å and c = 189.4 Å. Density packing considerations areconsistent with the presence of 4-6 monomers (Mr of the monomer, 160,000) in the asymmetric unit. Amino-terminal sequence of the enzyme and of a chymotryptic fragment of 73.7 kDa containing the COOH-terminus has been obtained. The extensive sequence identity with rat and human carbamoyl phosphate synthetase I indicates the relevance for mammals of structural data obtained with the frog enzyme. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220213
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    Prediction of the structure of GroES and its interaction with GroEL (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 199-209 
    Details
    ISSN: 0887-3585
    Keywords: chaperonins ; electron microscopy ; FTIR ; molecular modeling ; structure prediction ; contact prediction ; active site prediction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The three-dimensional structure of the GroES monomer and its interaction with GroEL has been predicted using a combination of prediction tools and experimental data obtained by biophysical [electron microscope (EM), Fourier transform infrared (FTIR), and nuclear magnetic resonance (NMR)] and biochemical techniques. The GroES monomer, according to the prediction, is composed of eight β-strands forming a β-barrel with loose ends. In the model, β-strands 5-8 run along the outer surface of GroES, forming an antiparallel β-sheet with β4 loosely bound to one of the edges. β-strands 1-3 would then be parallel and placed in the interior of the molecule. Loops 1-3 would face the internal cavity of the GroEL-GroES complex, and together with conserved residues in loops 5 and 7, would form the active surface interacting with GroEL. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220302
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    Structural model of the photosynthetic reaction center of Rhodobacter capsulatus (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 226-244 
    Details
    ISSN: 0887-3585
    Keywords: photosynthesis ; protein structure ; homology modeling ; molecular mechanics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The reaction center (RC) from the photosynthetic bacterium Rhodobacter (Rb.) capsulatus has been the subject of a considerable amount of molecular biological and spectroscopic work aimed at improving our understanding of the primary steps of photosynthesis. However, no three-dimensional structure is available for this protein. We present here a model obtained by combining information from the structure of the highly homologous RC from Rhodopseudomonas (Rps.) viridis with molecular mechanics and simulated annealing calculations. In the Rb. Capsulatus model the orientations of the bacteriochlorophyll monomer and the bacteriopheophytin on the branch inactive in electron transfer differ significantly from those in the RCs of Rps. Viridis and Rb. Sphaeroides. The bacteriopheophytin orientational difference is in good accord with previous linear dichroism measurements. A comparison is made of interactions between the pigments and the protein environment that may be of functional significance in Rps. viridis, Rb. sphaeroides, and Rb. capsulatus. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220304
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    Structural basis for serpin inhibitor activity (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 210-225 
    Details
    ISSN: 0887-3585
    Keywords: serpin-proteinase complex ; mutants ; deamidation ; α-helix-β-sheet conversion ; homology modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The mechanism of formation and the structures of serpin-inhibitor complexes are not completely understood, despite detailed knowledge of the structures of a number of cleaved and uncleaved inhibitor, noninhibitor, and latent serpins. It has been proposed from comparison of inhibitor and noninhibitor serpins in the cleaved and uncleaved forms that insertion of strand s4A into preexisting β-sheet A is a requirement for serpin inhibitor activity. We have investigated the role of this strand in formation of serpin-proteinase complexes and in serpin inhibitor activity through homology modeling of wild type inhibitor, mutant substrate, and latent serpins, and of putative serpin-proteinase complexes. These models explain the high stability of the complexes and provide an understanding of substrate behavior in serpins with point mutations in s4A and of latency in plasmingoen activator inhibitor I. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220303
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  • 54
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    The cytidylyltransferase superfamily: Identification of the nucleotide-binding site and fold prediction (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 259-266 
    Details
    ISSN: 0887-3585
    Keywords: homology search ; phosphodiesterases ; sequence analysis ; structure prediction ; threading ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The crystal structure of glycerol-3-phosphate cytidylyltransferase from B. subtilis (TagD) is about to be solved. Here, we report a testable structure prediction based on the identification by sequence analysis of a superfamily of functionally diverse but structurally similar nucleotide-binding enzymes. We predict that TagD is a member of this family. The most conserved region in this superfamily resembles the ATP-binding HiGH motif of class I aminoacyI-tRNA synthetases. The predicted secondary structure of cytidylyltransferase and its homologues is compatible with the α/β topography of the class I aminoacyl-tRNA synthetases. The hypothesis of similarity of fold is strengthened by sequence-structure alignment and 3D model building using the known structure of tyrosyl tRNA synthetase as template. The proposed 3D model of TagD is plausible both structurally, with a well packed hydrophobic core, and functionally, as the most conserved residues cluster around the putative nucleotide binding site. If correct, the model would imply a very ancient evolutionary link between class I tRNA synthetases and the novel cytidylyltransferase superfamily. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220306
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  • 55
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    Hard α-keratin IF: A structural model lacking a head-to-tail molecular overlap but having hybrid features characteristic of both epidermal keratin and vimentin IF (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 267-272 
    Details
    ISSN: 0887-3585
    Keywords: α-keratin ; intermediate filaments ; epidermal keratin ; vimentin ; keratinopathies ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In intermediate filaments (IF) both epidermal keratin and vimentin molecules have been shown to have an eight residue head to-tail overlap between the rod domains of similarly directed molecules. In the case of the epidermal keratins this region has also been shown to have particular structural/functional significance since it represents a hot-spot for mutations in the four keratinopathies characterized to date. While there is good evidence that this head-to-tail overlap is present in IF containing Type III, IV, and V chains, as well as in the epidermal keratin IF (Ib/IIb), there are no data currently available for the hard α-keratin IF (Ia/IIa). Using a variety of data derived from X-ray diffraction and crosslinking studies, as well as theoretical modeling, it is now possible to demonstrate that the overlap region is not a feature of hard α-keratin IF. Indeed, it is shown that there is a nine residue gap between consecutive parallel molecules in the IF. An explanation for this observation is presented in terms of compensating disulfide bonds that occur both within the IF, and between the IF and the matrix in which the IF are embedded. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220307
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    The catalytic domain of a bacterial lytic transglycosylase defines a novel class of lysozymes (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 245-258 
    Details
    ISSN: 0887-3585
    Keywords: bacterial muramidase ; peptidoglycan ; structure comparison ; sequence motifs ; structure/function relationships ; evolutionary relationships ; X-ray structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The 70-kDa soluble lytic transglycosylase (SLT70) from Escherichia coli is a bacterial exo-muramidase that cleaves the cell wall peptidoglycan, producing 1,6-anhydro-muropeptides. The X-ray structure of SLT70 showed that one of its domains is structurally related to lysozyme, although there is no obvious similarity in amino acid sequence. To relate discrete structural features to differences in reaction mechanism and substrate/product specificity, we compared the threedimensional structure of the catalytic domain of SLT70 with the structures of three typical representatives of the lysozyme superfamily: chicken-type hen egg-white lysozyme, goosetype swan egg-white lysozyme, and phage-type lysozyme from bacteriophage T4. We find a particularly close relationship between the catalytic domain of SLT70 and goose-type lysozyme, with not only a significant similarity in overall structure, but even a weak homology in amino acid sequence. This finding supports the notion that the goose-type lysozyme takes up a central position in the lysozyme superfamily and that it is structurally closest to the lysozyme ancestors. The saccharide-binding groove is the most conserved part in the four structures, but only two residues are absolutely preserved: the “catalytic” glutamic acid and a structurally required glycine. The “catalytic” aspartate is absent in SLT70, a difference that can be related to a different mechanism of cleavage of the β-1,4-glycosidic bond. The unique composition of amino acids at the catalytic site, and the observation of a number of differences in the arrangements of secondary structure elements, define the catalytic domain of SLT70 as a novel class of lysozymes. Its fold is expected to be exemplary for other bacterial and bacteriophage muramidases with lytic transglycosylase activity. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220305
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    Size-independent comparison of protein three-dimensional structures (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 273-283 
    Details
    ISSN: 0887-3585
    Keywords: globular proteins ; protein structure analysis ; optimal rigid body superposition ; three-dimensional structural motif ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Protein structures are routinely compared by their root-mean-square deviation (RMSD) in atomic coordinates after optimal rigid body superposition. What is not so clear is the significance of different RMSD values, particularly above the customary arbitrary cutoff for obvious similarity of 2-3 Å. Our earlier work argued for an intrinsic cutoff for protein similarity that varied with the number of residues in the polypeptide chains being compared. Here we introduce a new measure, ρ, of structural similarity based on RMSD that is independent of the sizes of the molecules involved, or of any other special properties of molecules. When ρ is less than 0.4-0.5, protein structures are visually recognized to be obviously similar, but the mathematically pleasing intrinsic cutoff of ρ〉1.0 corresponds to overall similarity in folding motif at a level not usually recognized until smoothing of the polypeptide chain path makes it striking. When the structures are scaled to unit radius of gyration and equal principle moments of inertia, the comparisons are even more universal, since they are no longer obscured by differences in overall size and ellipticity. With increasing chain length, the distribution of ρ for pairs of random structures is skewed to higher values, but the value for the best 1% of the comparisons rises only slowly with the number of residues. This level is close to an intrinsic cutoff between similar and dissimilar comparisons, namely the maximal scaled ρ possible for the two structures to be more similar to each other than one is to the other's mirror image. The intrinsic cutoff is independent of the number of residues or points being compared. For proteins having fewer than 100 residues, the 1% ρ falls below the intrinsic cutoff, so that for very small proteins, geometrically significant similarity can often occur by chance. We believe these ideas will be helpful in judging success in NMR structure determination and protein folding modeling. © 1995 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220308
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    Crystallization and preliminary crystallographic analysis of a 2,3-dihydroxybiphenyl dioxygenase from Pseudomonas sp. strain KKS102 having polychlorinated biphenyl (PCB)-degrading activity (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 284-286 
    Details
    ISSN: 0887-3585
    Keywords: PCB degrading enzyme ; dioxygenase ; crystallization ; polychlorinated biphenyl ; selenomethionine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Crystals have been obtained for a 2,3-dihydroxybiphenyl dioxygenase (conventionally called BphC) from a polychlorinated biphenyl (PCB)-degrader, Pseudomonas sp. strain KKS1O2. The crystals were grown using both ammonium sulfate and MPD as the precipitating agents. The crystals belonged to a tetragonal space group (I422) and diffracted to 2.5 Å. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220309
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    Cloning and expression of the uracil-DNA glycosylase inhibitor (UGI) from bacteriophage PBS-1 and crystallization of a uracil-DNA glycosylase-UGI complex (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 287-289 
    Details
    ISSN: 0887-3585
    Keywords: DNA repair ; PCR ; Bacillus subtilis ; herpes simplex virus ; protein-protein interaction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The uracil-DNA glycosylase inhibitory protein (UGI) from the bacterio-phage PBS-l has been cloned and overexpressed. The nucleotide sequence is identical to that for the previously described PBS-2 inhibitor. The recombinant PBS-l UGI inhibits the uracil-DNA glycosylase from herpes simplex virus type-l (HSV-l UDGase), and a complex between the HSV-l UDGase and PBS-l UGI has been crystallized. The crystals have unit cell dimensions a = 143.21 Å, c = 40.78 Å and are in a polar hexagonal space group. There is a single complex in the asymmetric unit with a solvent content of 62% by volume and the crystals diffract to 2.5Å on a synchrotron radiation source. © 1995 Wiley-Liss, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340220310
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    Crystallization and preliminary X-ray crystallographic studies of nonhistone region of macroH2A.1 (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 290-292 
    Details
    ISSN: 0887-3585
    Keywords: macroH2A ; specialized nucleosomes ; fusion protein ; crystallization ; X-ray diffraction ; noncrystal-lographic symmetry ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Histone macroH2A has a novel hybrid structure consisting of a large nonhistone region and a region that closely resembles a full-length histone H2A. One key to understanding macroH2A function is determining the structure and function of its nonhistone region. The nonhistone region of one of the two known macroH2A subtypes was expressed in Escherichia coli and purified using affinity and molecular sieve chromatography. Crystals of the protein suitable for structural studies were grown from polyethylene glycol solutions by vapor equilibration techniques. The crystals belong to the hexagonal space group P64 (or its enantiomorph P62) with unit cell parameters: a = b = 106.2 Å, c = 125.9 Å, α = β = 90°, and γ = 120°. There are four molecules in the asymmetric unit. Self-rotation function studies revealed three twofold noncrystallographic rotation axes related approximately by 222 symmetry. These crystals have 47% solvent content and diffract to 3.8 Å resolution. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220311
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    Crystallization and preliminary crystallographic data for class I deoxyribose-5-phosphate aldolase from Escherichia coli: An Application of Reverse Screening (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 67-72 
    Details
    ISSN: 0887-3585
    Keywords: aldolase ; protein complex crystallization ; crystallization screening ; X-ray crystallography ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: X-ray quality crystals of class I deoxyribose-5-phosphate aldolase from Escherichia coli have been obtained for the unliganded enzyme and in complex with its substrate, 2-deoxyribose-5-phosphate. The enzyme catalyzes the reversible cleavage of 2-deoxyribose-5-phosphate to acetaldehyde and D-glyceraldehyde-3-phosphate. The unliganded and complex crystals are prismatic long rods and belong to the orthorhombic space group P212121 with cell dimensions a = 183.1 Å, b = 61.4 Å, c = 49.3 Å and a = 179.2 Å, b = 60.5, Å, c = 49.1 Å, respectively. Two molecules in the asymmetric unit are related by a noncrystallo-graphic 2-fold axis. The crystals are stable in the X-ray beam and diffract to at least 2.6 Å. A new method, reverse screening, designed to minimize protein utilization during the screening process was used to determine supersaturation and crystallization conditions. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220110
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    Masthead (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995) 
    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.340220201
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    Crystallization and preliminary diffraction studies of thioesterase II from rat mammary gland (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 73-75 
    Details
    ISSN: 0887-3585
    Keywords: thioesterase ; crystallization ; X-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Thioesterase II from rat mammary gland has been crystallized in the presence of decanoic acid by the vapor diffusion method. The crystals belong to the orthorhombic space group P212121, and have cell dimensions, a = 52.7 Å, b = 78.0 Å, and c = 133.6 Å. The asymmetric unit likely consists of two protein monomers based on predictions from its calculated Matthews coefficient. Crystals typically diffract to at least 2.5 Å resolution and are suitable for X-ray crystallographic analysis. © 1995 Wiley-Liss, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340220111
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    Crystallization and preliminary X-ray diffraction studies of the cartilage link protein from bovine trachea (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 76-78 
    Details
    ISSN: 0887-3585
    Keywords: arthritis ; cartilage ; crystallization ; link protein ; proteoglycan aggregate ; X-ray crystallography ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Cartilage extracellular matrix link protein, having molecular mass of approximately 40 kDa, is a metalloprotein that binds divalent cations and is only soluble in low ionic strength solutions. The link protein was purified from bovine trachea and has been crystallized by a vapor diffusion method using PEG 3350 as precipitant. The crystal symmetry is P1, and the unit cell dimensions are a = 43.55, b = 53.11, c = 60.10 Å, α = 90.44, β = 106.21, γ = 101.51°. The VM of 1.8 Å3/Da is consistent with the presence of two molecules of the link protein in the asymmetric unit. The crystals diffract X-rays from a synchrotron source to 1.7 Å resolution. © 1995 Wiley-Liss, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340220112
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    Accurate general method for lattice approximation of three-dimensional structure of a chain molecule (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 100-109 
    Details
    ISSN: 0887-3585
    Keywords: protein structure ; RNA structure ; lattice model ; chain connectivity ; self-avoiding ; dynamic programming ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An algorithm based on dynamic programming gives the lattice models having the minimal RMS deviations from the actual folds of protein (RNA, etc.) chains for a given lattice and a given orientation of the macromolecule relative to the lattice. The algorithm is applicable for 3-D lattices of any kind. The accuracy of the lattice approximation increases when the distance between neighbor chain links is not rigidly fixed. Special repulsive potentials facilitate generation of self-avoiding lattice chains. The results of model building show the efficiency and precisionof this proposed general method when compared with others. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220203
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    Crystallization and preliminary crystallographic study of human CksHs1: A cell cycle regulatory protein (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 70-73 
    Details
    ISSN: 0887-3585
    Keywords: cell cycle protein ; crystallization ; X-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The cell cycle regulatory protein CksHs1 has been crystallized in a form suitable for X-ray studies. CksHsl crystals were grown in the presence of vanadate, a phos-phatase inhibitor, but were also obtained with phosphate or tungstate as a cofactor. They belong to the hexagonal space group P6122 with unit cell dimensions: a=b=94 Å, c=131.6 Å, and γ =120. The crystals grown in the presence of vanadate diffract X-rays to at least 2.8 Å. Molecular replacement results from the homologous human CksHs2 structure reveal that a dimer forms the crystal habit, giving the unusual Vm value of 4.4 Å3/Da or a solvent content of 72%. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340210109
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    Modulation of DNA-binding specificity within the nuclear receptor family by substitutions at a single amino acid position (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 57-67 
    Details
    ISSN: 0887-3585
    Keywords: glucocorticoid receptor ; DNA binding domain ; mutant ; yeast ; transcription factor ; transactivation ; modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Regulation of gene expression involves a large number of transcription factors with unique DNA-binding properties. Many transcription factors belong to families of related proteins that bind to similar but distinct sequences. In this study we have analyzed how amino acid substitutions at a single position in the DNA-binding domain modulate the DNA binding specificity within the nuclear receptor family of transcription factors. All possible amino acids were introduced at the first position in the DNA recognition helix, and the specificities of the mutants were analyzed using response elements containing all combinations of bases at two variable base pair positions. All mutant proteins were functional in DNA binding, and could be divided into classes of mutants with different response element specificities. By combining functional data with analysis of the structural effects of the mutations by molecular modeling, we could identify both prohibitive steric interactions as well as positive interactions, such as hydrogen bonds, that function as important determinants for specificity. Only the residues found naturally in the glucocorticoid and estrogen receptors, glycine and glutamate, produce unique binding specificities. The specificities of the other mutants overlap with each other somewhat but the substitutions clearly have potential to contribute to diversity within the nuclear receptor family. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340210107
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    An analysis of side chain interactions and pair correlations within antiparallel β-sheets: The differences between backbone hydrogen-bonded and non-hydrogen-bonded residue pairs (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 119-131 
    Details
    ISSN: 0887-3585
    Keywords: antiparallel β-sheet ; twist ; protein folding ; side chain interactions ; branched amino acids ; cystine-rich proteins ; side chain packing ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Cross-strand pair correlations are calculated for residue pairs in antiparallel β-sheet for two cases: pairs whose backbone atoms are hydrogen bonded together (H-bonded site) and pairs which are not (non-H-bonded site). The statistics show that this distinction is important. When glycine is located on the edge of a sheet, it shows a 3:1 preference for the H-bonded site. Thestrongest observed correlations are for pairs of disulfide-bonded cystines, many of which adopt a close-packed conformation with each cystine in a spiral conformation of opposite chirality to its partner. It is likely that these pairs are a signature for the family of small, cystine-rich proteins. Most other strong positive and negative correlations involve charged and polar residues. It appears that electrostatic compatibility is the strongest factor affecting pair correlation. Significant correlations are observed for β- and γ-branched residues inthe non-H-bonded site. An examination of the structures showsa directionality in side chain packing. There is a correlation between (1) the directionality in the packing interactions of non-H-bonded β- and γ-branched residue pairs, (2) the handedness of the observed enantiomers of chiral β-branched side chains, and (3) the handedness of the twist of β-sheet. These findings have implications for the formation of β-sheets during protein folding and the mechanism by which the sheet becomes twisted. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220205
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    An automated method for dynamic ligand design (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 472-490 
    Details
    ISSN: 0887-3585
    Keywords: drug design ; FKBP ; FK506 ; immunophilin ; MCSS ; DLD ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An automated method for the dynamic ligand design (DLD) for a binding site of known structure is described. The method can be used for the creation of de novo ligands and for the modification of existing ligands. The binding site is saturated with atoms (sp3 carbon atoms in the present implementation) that form molecules under the influence of a potential function that joins atoms to each other with the correct stereochemistry. The resulting molecules are linked to precomputed functional group minimum energy positions in the binding site. The generalized potential function allows atoms to sample a continuous parameter space that includes the Cartesian coordinates and their occupancy and type, e.g., the method allows change of an sp3 carbon into an sp2 carbon or oxygen. A parameter space formulated in this way can then be sampled and optimized by a variety of methods. In this work, molecules are generated by use of a Monte Carlo simulated annealing algorithm. The DLD method is illustrated by its application to the binding site of FK506 binding protein (FKBP), an immunophilin. De novo ligands are designed and modification of the immunosuppressant drug FK506 are suggested. The results demonstrate that the dynamic ligand design approach can automatically construct ligands which complement both the shape and charge distribution of the binding site. © 1995 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340230403
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    Docking of a human rhinovirus neutralizing antibody onto the viral capsid (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 491-501 
    Details
    ISSN: 0887-3585
    Keywords: antibody structure ; viral neutralization ; human rhinovirus ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The structure of the complex between the Fab fragment of a human rhinovirus serotype 2 (HRV2) neutralizing antibody (8F5) and a cross-reactive synthetic peptide derived from the viral capsid protein VP2 has been recently determined by crystallographic methods.1 The conformation adopted by the peptide was very similar to and could be superimposed onto the corresponding region of the viral protein VP2 of human rhinovirus 1A (HRV1A) whose three-dimensional structure is known.2 The structure of the Fab fragment determined in the complex was docked onto the viral capsid using the superimposition transformation found for the peptide. In the resulting model the Fab protrudes almost radially to about 60 Å from the surface of the virion without any major steric problem. The Fab fragment was then placed on each one of the 60 equivalent epitopes using the T = 1 icosahedral symmetry of the virus. The closest pairs of Fab fragments are related by viral 2-fold axes and run almost parallel to each other without clashing. These axes of symmetry from the viral particle could thus be coincident with the dyad axes of the antibodies. Furthermore, comparison of the three-dimensional structure of the Fab/peptide complex with the structure of the Fab fragment alone3 indicates that the flexibility of the antibody's elbow would facilitate bivalent attachment to the same viral particle. In accordance with the docking results, experimental determination of the stoichiometry of binding yielded a ratio of 30 IgG molecules per virion also suggesting bivalent attachment of antibody 8F5 onto the viral particle. The neutralization of viral infectivity, being neither aggregation (this paper) nor inhibition of receptor binding,4 might be mainly achieved by reducing viral spread from cell to cell and/or inhibition of uncoating. © 1995 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/prot.340230404
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    Toward understanding the structure and interactions of microtubules and motor proteins (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 502-509 
    Details
    ISSN: 0887-3585
    Keywords: microtubules ; molecular motors ; electron cryomicroscopy ; decorated microtubules ; microtubule organization ; structure of microtubule/motor domain complexes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: To obtain an overall three-dimensional picture of the interaction between microtubules and the motor proteins of the kinesin family it will be necessary to take account of both atomic resolution structures obtained by X-ray crystallography and medium resolution reconstructions obtained by electron cryomicroscopy. We examine the problems associated with obtaining the required structural information from electron micrographs of vitreous ice-embedded microtubules decorated with motor domains. We find that the minus-end directed motor, ncd, decorates microtubules with an 80 Å periodicity as for kinesin. Our theoretical analysis and experiments with ncd illustrate the difficulty in determining unambiguously the surface lattice organization by diffraction analysis of micrographs. 3D reconstructions of decorated microtubules are required to accurately locate the motor domains. Helical diffraction theory is not usually applicable because microtubules are cylindrical structures that rarely have complete helical symmetry. We propose using a back-projection method based on the long pitch helices formed by individual protofilaments. Model reconstructions show that this approach is feasible. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340230405
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    Binding geometry of α-helices that recognize DNA (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 525-535 
    Details
    ISSN: 0887-3585
    Keywords: DNA-protein interaction ; crystal structure ; transcription factor ; gene regulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Many transcription factors have an α-helix that binds to DNA bases in a specific fashion. The DNA-binding geometry of these recognition helices varies substantially. We define a set of parameters to describe the binding geometry of recognition helices and analyze specific stereochemical elements that determine particular geometries. Because the convex surface of the helix must fit into the concave surface of the DNA major groove, the number of degrees of freedom of the recognition helix is reduced from a possible six to a single angle, which we call α. The chemically interacting DNA bases and amino acid residues must lie along a common line and have the same spacing along it. This pairing of base positions with residue positions seems to restrict the binding geometry further to a set of discrete values for α. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340230407
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    Crystallographic structure of metal-free concanavalin A at 2.5 Å resolution (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 510-524 
    Details
    ISSN: 0887-3585
    Keywords: lectin ; demetallized ; peptide bond isomerization ; inter-dimer interactions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The three-dimensional structure of demetallized concanavalin A has been determined at 2.5 Å resolution and refined to a crystallographic R-factor of 18%. The lectin activity of concanavalin A requires the binding of both a transition metal ion, generally Mn2+, and a Ca2+ ion in two neighboring sites in close proximity to the carbohydrate binding site. Large structural differences between the native and the metal-free lectin are observed in the metal-binding region and consequently for the residues involved in the specific binding of saccharides. The demetallization invokes a series of conformational changes in the protein backbone, apparently initiated mainly by the loss of the calcium ion. Most of the Mn2+ ligands retain their position, but the Ca2+ binding site is destroyed. The Ala207-Asp208 peptide bond, in the β-strand neighboring the metal-binding sites, undergoes a cis to trans isomerization. The cis conformation for this bond is a highly conserved feature among the leguminous lectins and is critically maintained by the Ca2+ ion in metal-bound concanavalin A. A further and major change adjacent to the isomerized bond is an expansion of the loop containing the monosaccharide ligand residues Leu99 and Tyr100. The dispersion of the ligand residues for the monosaccharide binding site (Asn14, Agr228, Asp208, Leu99, and Tyr100) in metalfree concanavalin A abolishes the lectin's ability to bind saccharides. Since the quaternary structure of legume lectins is essential to their biological role, the tetramer formation was analyzed. In the crystal (pH 5), the metal-free concanavalin A dimers associate into a tetramer that is similar to the native one, but with a drastically reduced number of inter-dimer interactions. This explains the tetramer dissociation into dimers below pH values of 6.5. © 1995 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/prot.340230406
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    Atomic and residue hydrophilicity in the context of folded protein structures (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 536-547 
    Details
    ISSN: 0887-3585
    Keywords: water ; hydrophobicity ; hydration ; X-ray crystallography ; solvation ; ordered solvent ; molecular recognition ; water-protein interactions ; drug and inhibitor design ; protein surface analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Water-protein interactions drive protein folding, stabilize the folded structure, and influence molecular recognition and catalysis. We analyzed the closest protein contacts of 10,837 water molecules in crystallographic structures to define a specific hydrophilicity scale reflecting specific rather than bulk solvent interactions. The tendencies of different atom and residue types to be the nearest protein neighbors of bound water molecules correlated with other hydrophobicity scales, verified the relevance of crystallographically determined water positions, and provided a direct experimental measure of water affinity in the context of the folded protein. This specific hydrophilicity was highly correlated with hydrogen-bonding capacity, and correlated better with experimental than computationally derived measures of partitioning between aqueous and organic phases. Atoms with related chemistry clustered with respect to the number of bound water molecules. Neutral and negatively charged oxygen atoms were the most hydrophilic, followed by positively-charged then neutral nitrogen atoms, followed by carbon and sulfur atoms. Agreement between observed side-chain specific hydrophilicity values and values derived from the atomic hydrophilicity scale showed that hydrophilicity values can be synthesized for different functional groups, such as unusual side or main chains, discontinuous epitopes, and drug molecules. Two methods of atomic hydrophilicity analysis provided a measure of complementarity in the interfaces of trypsin:pancreatic trypsin inhibitor and HIV protease:U-75875 inhibitor complexes. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340230408
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    A model for the LexA repressor DNA complex (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 226-236 
    Details
    ISSN: 0887-3585
    Keywords: doeking ; Monte Carlo ; LexA repressor ; DNA binding domain ; protein-DNA interaction ; solution structure ; molecular recognition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A structural model for the interaction of the LexA repressor DNA binding domain (DBD) with operator DNA is derived by means of Monte Carlo docking. Protein-DNA complexes were generated by docking the LexA repressor DBD NMR solution structure onto both rigid and bent B-DNA structures while giving energy bonuses for contacts in agreement with experimental data. In the resulting complexes, helix III of the LexA repressor DBD is located in the major groove of the DNA and residues Asn-41, Glu-44, and Glu-45 form specific hydrogen bonds with bases of the CTGT DNA sequence. Ser-39, Ala-42, and Asn-41 are involved in a hydrophobic interaction with the methyl group of the first thymine base. Residues in the loop region connecting the two β-sheet strands are involved in nonspecific contacts near the dyad axis of the operator. The contacts observed in the docked complexes cover the entire consensus CTGT half-site DNA operator, thus explaining the specificity of the LexA repressor for such sequences. In addition, a large number of nonspecific interactions between protein and DNA is observed. The agreement between the derived model for the LexA repressor DBD/DNA complex and experimental biochemical results is discussed. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340210305
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    Packing constraints of hydrophobic side chains in (α/β)8 barrels (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 256-260 
    Details
    ISSN: 0887-3585
    Keywords: α/β - barrel ; α/β - hyperboloid - 8 ; three-dimensional structure ; local tight packing of hydrophobic groups ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An analysis of possible tight packing of hydrophobic groups simultaneously at the both surfaces of β-hyperboloid-8 was conducted. This analysis shows that the disposition of amino acid side chains at the real β-structure's surface is unique. If we sign the mean distance between adjacent β-strands as “a,” and the mean distance along β-strand between Cα atoms, whose side chains are directed to one side of the β-sheet, as “b,” the ratio b/a = √2 very precisely. This ratio ensures the most efficient packing of side hydrophobic groups at the outer surface of β-hyperboloid-8, forming, at the same time, the second by efficiency packing at its inner surface. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340210308
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    The first solvation shell of magnesium ion in a model protein environment with formate, water, and X-NH3, H2S, imidazole, formaldehyde, and chloride as ligands: An ab initio study (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 244-255 
    Details
    ISSN: 0887-3585
    Keywords: carboxylate ; magnesium ; hydration ; ligand ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The first coordination shell of an Mg(II) ion in a model protein environment is studied. Complexes containing a model carboxylate, an Mg(II) ion, various ligands (NH3, H2S, imidazole, and formaldehyde) and water of hydration about the divalent metal ion were geometry optimized. We find that for complexes with the same coordination number, the unidentate carboxylate-Mg(II) ion is greater than 10 kcal mol-1 more stable than the bidentate orientation. Imidazole was found to be the most stable ligand, followed in order by NH3 formaldehyde, H2O, and H2S. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    Protein conformational landscapes: Energy minimization and clustering of a long molecular dynamics trajectory (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 97-110 
    Details
    ISSN: 0887-3585
    Keywords: bovine pancreatic trypsin inhibitor ; cluster analysis ; conformational searching ; molecular dynamics ; protein tertiary structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Using energy minimization and cluster analysis, we have analyzed a 1020 ps molecular dynamics trajectory of solvated bovine pancreatic trypsin inhibitor. Elucidation of conformational sub states in this way both illustrates the degree of conformational convergence in the simulation and reduces the structural data to a tractable subset. The relative movement of structures upon energy minimization was used to estimate the sizes of features on the protein potential energy surface. The structures were analyzed using their pairwise root-mean-square Cα deviations, which gave a global measure of conformational changes that would not be apparent by monitoring single degrees of freedom. At time scales of 0.1 ps, energy minimization detected sharp transitions between energy minima separated by 0.1 Å rms deviation. Larger conformational clusters containing these smaller minima and separated by 0.25 Å were seen at 1 ps time scales. Both of these small features of the conformational landscape were characterized by movements in loop regions associated with small, correlated backbone dihedral angle shifts. On a nanosecond time scale, the main features of the protein energy landscape were clusters separated by over 0.7 Å rms deviation, with only seven of these sub states visited over the 1 ns trajectory. These substates, discernible both before and after energy minimization, differ mainly in a monotonic pivot of the loop residues 11-18 over the course of the simulation. This loop contains lysine 17, which specifically binds to trypsin in the active site. The trajectory did not return to previously visited clusters, indicating that this trajectory has not been shown to have completely sampled the conformational substates available to it. Because the apparent convergence to a single region of conformation space depends on both the time scale of observation and the size of the conformational features examined, convergence must be operationally defined within the context of the simulation. © 1995 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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    Crystallization and preliminary X-ray diffraction studies of complexes between an influenza hemagglutinin and fab fragments of two different monoclonal antibodies (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 115-117 
    Details
    ISSN: 0887-3585
    Keywords: antibody-protein complex ; influenza virus hemagglutinin ; protein recognition ; crystallization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Fab fragments from two different monoclonal antibodies (BH151 and HC45) which bind to the same antigenic region of the influenza hemagglutinin were crystallized as complexes with the hemagglutinin. The complexes crystallize in PEG 600, pH 6.0, and PEG 2000, pH 8.5, respectively. Both crystals belong to space group P321, with very similar unit cell dimensions. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    Crystallization and preliminary X-ray investigation of recombinant human interleukin 10 (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 187-190 
    Details
    ISSN: 0887-3585
    Keywords: cytokine ; BCRF1 ; protein structure ; crystal seeding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Crystals of recombinant human interleukin 10 have been grown from solutions of ammonium sulfate. The crystals are tetragonal, space group P41212 or P43212; the unit cell axes are a = 36.5 Å and c = 221.9 Å. There is the equivalent of one polypeptide chain in the asymmetric unit. The crystals are stable to X-rays and diffract to at least 2.5 Å resolution. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340220211
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    Purification, crystallization, and preliminary X-ray diffraction analyses of the bacterial chemotaxis receptor modifying enzymes (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 345-350 
    Details
    ISSN: 0887-3585
    Keywords: methyltransferase ; methylesterase ; protein modification ; S-adenosyl-L-methionine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Bacterial chemotaxis receptor modifying enzymes from Salmonella typhimurium have been crystallized using microseeding techniques. The crystals of the S-adenosyl-L-methionine-dependent methyl transferase, CheR, belong to the monoclinic space group P21 with cell constants a = 55.1 Å, b = 48.1 Å, c = 63.1 Å, β = 112.3°. The crystals of the catalytic domain of the methylesterase, CheB, belong to the trigonal space group P3221 or P3121 with unit cell dimensions of a = b = 63.4 Å, c = 86.8 Å. Both crystals contain one molecule per asymmetric unit and have calculated Matthews' volumes of 2.4 Å3/Da. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340210407
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    Masthead (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995) 
    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.340210101
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    Predicted secondary and supersecondary structure for the serine-threonine-specific protein phosphatase family (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 1-10 
    Details
    ISSN: 0887-3585
    Keywords: protein structure prediction ; protein phosphatase ; evolution ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A bona fide consensus prediction for the secondary and supersecondary structure of the serine-threonine specific protein phosphatases is presented. The prediction includes assignments of active site segments, an internal helix, and a region of possible 310 helical structure. An experimental structure for a member of this family of proteins should appear shortly, allowing this prediction to be evaluated. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    Thermodynamic genetics of the folding of the B1 immunoglobulin-binding domain from streptococcal protein G (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 11-21 
    Details
    ISSN: 0887-3585
    Keywords: phage display ; protein stability ; genetic selection ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A method has been developed to select proteins that are thermodynamically destabilized yet still folded and functional. The DNA encoding the B1 IgG-binding domain from Group G Streptococcus (Strp G) has been fused to gene III of bacteriophage M13. The resulting fusion protein is displayed on the surface of the phage thus enabling the phage to bind to IgG molecules. In addition, these phage exhibit a small plaque phenotype that is reversed by mutations that destabilize the Strp G domain. By selecting phage with large plaque morphology that retain their IgG-binding function, it is possible to identify mutants that are folded but destabilized compared with wild-type Strp G. Such mutants can be divided into three general categories: (1) those that disrupt packing of hydrophobic side chains in the protein interior; (2) those that destabilize secondary structure; and (3) those that alter specific hydrogen bonds involving amino acid side chains. A number of the mutants have been physically characterized by circular dichroism and nuclear magnetic resonance and have been shown to have structures similar to wild-type Strp G but stabilities that were decreased by 2-5 kcal/mol. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    Elusive affinities (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 30-39 
    Details
    ISSN: 0887-3585
    Keywords: protein-protein interaction ; protein-DNA interaction ; microcalorimetry ; heat capacity changes ; entropy ; accessible surface area ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The affinity of two molecules for each other and its temperature dependence are determined by the change in enthalpy, free enthalpy, entropy, and heat capacity upon dissociation. As we know the forces that stabilize-protein-protein or protein-DNA association and the three-dimensional structures of the complex, we can in principle derive values for each one of these parameters. The calculation is done first in gas phase by molecular mechanics, then in solution with the help of hydration parameters calibrated on small molecules. However, estimates of enthalpy and entropy changes in gas phase have excessively large error bars even under the approximation that the components of the complex associate as rigid bodies. No reliable result can be expected at the end. The fit to experimental values derived from binding and calorimetric measurements is poor, except for the dissociation heat capacity. This parameter can be attributed mostly to the hydration step and it correlates with the size of the interface. Many protein-protein complexes have interface areas in the range 1200-2000 Å2 and only small conformation changes, so the rigid body approximation applies. It is less generally valid in protein-DNA complexes, which have interfaces covering 2200-3100 Å2, large dissociation heat capacities, and affect both the conformation and the dynamics of their components. © 1995 Wiley-Liss, Inc.
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    Crystallization and preliminary structural studies of the ncd motor domain (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 68-69 
    Details
    ISSN: 0887-3585
    Keywords: microtubule motors ; X-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The motor domain of the kinesin homolog ncd has been crystallized in the presence of MgATP by the vapor diffusion method using polyethylene glycol as the precipitant. The crystals belong to the orthorhombic space group I222 with unit cell dimensions a = 127.1 Å, b = 122.3 Å, c = 68.0 Å, and there is one ncd molecule per asymmetric unit. The crystals diffract X-ray to at least 2.3 Å and are appropriate for high-resolution structure determination. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/prot.340210108
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    Molecular dynamics simulations of alcohol dehydrogenase with a four- or five-coordinate catalytic zinc ion (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 40-56 
    Details
    ISSN: 0887-3585
    Keywords: zinc parameterization ; effective force-field ; four-coordination ; five-coordination ; reaction mechanism ; ligand exchange ; bond length constraint ; ligand dynamics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A detailed parameterization is presented of a zinc ion with one histidine and two cysteinate ligands, together with one or two water, hydroxide, aldehyde, alcohol, or alkoxide ligands. The parameterization is tailored for the active site of alcohol dehydrogenase and is obtained entirely from quantum chemical computations. The force-field reproduces excellently the geometry of quantum chemically optimized zinc complexes as well as the crystallographic geometry of the active site of alcohol dehydrogenase and small organic structures. The parameterization is used in molecular dynamics simulations and molecular mechanical energy minimizations of alcohol dehydrogenase with a four- or five-coordinate catalytic zinc ion. The active-site zinc ion seems to prefer four-coordination over five-coordination by at least 36 kJ/mol. The only stable binding site of a fifth ligand at the active-site zinc ion is opposite to the normal substrate site, in a narrow cavity behind the zinc ion. Only molecules of the size of water or smaller may occupy this site. There are large fluctuations in the geometry of the zinc coordination sphere. A four-coordinate water molecule alternates frequently (every 7 ps) between the substrate site and the fifth binding site and even two five coordinate water molecules may interchange ligation sites without prior dissociation. Ligand exchange at the zinc ion probably proceeds by a dissociative mechanism. The results show that it is essential to allow for bond stretching degrees of freedom in molecular dynamics simulations to get a correct description of the dynamics of the metal coordination sphere; bond length constraints may restrict the accessible part of the phase space and therefore lead to qualitatively erroneous results. © 1995 Wiley-Liss, Inc.
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    LINUS: A hierarchic procedure to predict the fold of a protein (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 81-99 
    Details
    ISSN: 0887-3585
    Keywords: protein folding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We describe LINUS, a hierarchic procedure to predict the fold of a protein from its amino acid sequence alone. The algorithm, which has been implemented in a computer program, was applied to large, overlapping fragments from a diverse test set of 7 X-ray-elucidated proteins, with encouraging results. For all proteins but one, the overall fragment topology is well predicted, including both secondary and supersecondary structure. The algorithm was also applied to a molecule of unknown conformation, groES, inwhich X-ray structure determination is presently ongoing. LINUS is an acronym for Local Independently Nucleated Units of Structure. The procedure ascends the folding hierarchy in discrete stages, with concomitant accretion of structure at each step. The chain is represented by simplified geometry and folds under the influence of a primitive energy function. The only accurately described energetic quantity in this work is hard sphere repulsion-the principal forceinvolved in organizing protein conformation [Richards, F. M. Ann. Rev. Biophys. Bioeng. 6:151-176, 1977]. Among other applications, the method is a natural tool for use in the human genome initiative. © 1995 Wiley-Liss, Inc.
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    Investigation of the folding pathway of the TEM-1 β-lactamase (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 110-118 
    Details
    ISSN: 0887-3585
    Keywords: protein folding ; guanidine hydrochloride denaturation ; molten globule ; folding/unfolding kinetics ; proline isomerization ; slow-folding forms ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The TEM-1 β-lactamase is a globular protein containing 12 proline residues. The folding mechanism of this enzyme was investigated by kinetic and equilibrium experiments with the help of fluorescence spectroscopy and circular dichroism. The equilibrium denaturation of the protein induced by guanidine hydrochloride occurs in two discrete steps, indicating the existence of a thermodynamically stable intermediate state. Thisstate is 5.2 ± 0.4 kcal/mol less stable than the native conformation and 5.7 ± 0.2 kcal/mol more stable than the fully denaturedprotein. This intermediate state exhibits a high content of native secondary structure elements but is devoid of specific tertiary organization; its relation to the “molten globule” is discussed. Refolding kinetic experimentsrevealed the existence of a transient intermediate conformation between thethermodynamically stable intermediate and the native protein. This transient intermediate appears rapidly during the folding reaction. It exhibits a secondary structure content very similar to that of the native protein and has also recovered a significant amount of tertiary organisation. The final refolding step of the TEM-1 β-lactamase, leading to the native enzyme, is dominated by two major slow kinetic phases which probablyreflect a very complex process kinetically limited by proline cis/transisomerization. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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    Masthead (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995) 
    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.340210201
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    Crystals of an antibody FV fragment against an integral membrane protein diffracting to 1.28 Å resolution (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 74-77 
    Details
    ISSN: 0887-3585
    Keywords: crystallization ; membrane protein ; X-ray diffraction ; atomic resolution ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The Fv fragment of a monoclonal antibody, 7E2 (IgG1, κ, murine), which is directed against the integral membrane protein cytochrome c oxidase (EC 1.9.3.1) from Paracoccus denitrificans, was cloned and produced in Escherichia coli. Crystals suitable for highresolution X-ray analysis were obtained by microdialysis under low salt conditions. The crystals belong to the orthorhombic space group P212121 with unit cell dimensions of a = 51.51 Å, b = 56.15 Å, c = 99.86 Å (1 Å = 0.1 nm) and contain one F v fragment per asymmetric unit. Using synchrotron radiation diffraction data were collected up to 1.28 Å resolution. This high resolution is very unusual for a heterodimeric protein. The crystals should open the way for refining not only the atomic positions, but also for obtaining information about internal dynamics. © 1995 Wiley-Liss, Inc.
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    Preliminary X-ray diffraction analysis of crystals of turnip yellow mosaic virus (TYMV) (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 78-81 
    Details
    ISSN: 0887-3585
    Keywords: T = 3 plant virus ; tymovirus ; protein crystallization ; X-ray diffraction ; synchrotron radiation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Turnip yellow mosaic virus (TYMV) was purified from Chinese cabbage and crystallized in a form that permits high resolution structural analysis using X-ray diffraction. The crystals have a hexagonal bipyramidal morphology and often achieve dimensions of 1.0 × 1.0 × 0.5 mm. The crystals appear to be of hexagonal space group P6222 with a = b = 525 Å, c=315 Å, but we cannot strictly rule out the possibility that the space group is P622. They appear different than any crystals of TYMV previously reported. There are three T = 3 virus particles in the unit cell, which implies that one quarter of the particle, or 45 protein subunits, comprises the asymmetric unit of the crystal. Native data have been collected using synchrotron radiation to a resolution of 3.2 Å. © 1995 Wiley-Liss, Inc.
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    Configurational effects in antibody-antigen interactions studied by microcalorimetry (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 83-90 
    Details
    ISSN: 0887-3585
    Keywords: cytochrome c ; thermodynamics ; antibody binding ; microcalorimetry ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In this paper we study the binding of two monoclonal antibodies, E3 and E8, to cytochrome c using high-sensitivity isothermal titration calorimetry. We combine the calorimetric results with empirical calculations which relate changes in heat capacity to changes in entropy which arise from the hydrophobic effect. The change in heat capacity for binding E3 is -350 ± 60 cal K-1 mol-1 while for E8 it is -165 ± 40 cal K-1 mol-1. This result indicates that the hydrophobic effect makes a much larger contribution for E3 than for E8. Since the total entropy change at 25°C is very similar for both antibodies, it follows that the configurational entropy cost for binding E3 is much larger than for binding E8 (-77 ± 15 vs. -34 ± 11 cal K-1 mol-1). These results illustrate a case of entropy compensation in which the cost of restricting conformational degrees of freedom is to a large extent compensated by solvent release. We also show that the thermodynamic data can be used to make estimates of the surface area changes that occur upon binding. The results of the present study are consistent with previous hydrogen-deuterium exchange data, detected using 2D NMR, on the two antibody-antigen interactions. The NMR study indicated that protection from exchange is limited to the binding epitope for E8, but extends beyond the epitope for E3. These results were interpreted as suggesting that a larger surface area was buried on cytochrome c upon binding to E3 than to E8, and that larger changes in configurational entropy occur upon binding of E3 than E8. These findings are confirmed by the present study using isothermal titration calorimetry. © 1995 Wiley-Liss, Inc.
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    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340210202
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  • 94
    Electronic Resource
    Electronic Resource
    Three-dimensional structure prediction of the NAD binding site of proton-pumping transhydrogenase from Escherichia coli (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 91-104 
    Details
    ISSN: 0887-3585
    Keywords: transhydrogenase ; NAD binding ; prediction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A three-dimensional structure of the NAD site of Escerichia coli transhydrogenase has been predicted. The model is based on analysis of conserved residues among the transhydrogenases from five different sources, homologies with enzymes using NAD as cofactors or substrates, hydrophilicity profiles, and secondary structure predictions. The present model supports the hypothesis that there is one binding site, located relatively close to the N-terminus of the α-subunit. The proposed structure spans residues α145 to α287, and it includes five β-strands and five α-helices oriented in a typical open twisted α/β conformation. The amino acid sequence following the GXGXXG dinucleotide binding consensus sequence (residues α172 to α177) correlates exactly to a typical fingerprint region for ADP binding βαβ folds in dinucleotide binding enzymes. In the model, aspartic acid α195 forms hydrogen bonds to one or both hydroxyl groups on the adenosine ribose sugar moiety. Threonine α196 and alanine α256, located at the end of βB and βD, respectively, create a hydrophobic sandwich with the adenine part of NAD buried inside. The nicotinamide part is located in a hydrophobic cleft between αA and βE. Mutagenesis work has been carried out in order to test the predicted model and to determine whether residues within this domain are important for proton pumping directly. All data support the predicted structure, and no residue crucial for proton pumping Was detected. Since no three-dimensional structure of transhydrogenase has been solved, a well based tertiary structure prediction is of great value for further experimental design in trying to elucidate the mechanism of the energy-linked proton pump. © 1995 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340210203
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  • 95
    Electronic Resource
    Electronic Resource
    A vector projection method for predicting the specificity of GalNAc-transferase (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 118-126 
    Details
    ISSN: 0887-3585
    Keywords: O-glyeosylation ; Ser-conjugated substrate ; Thr-conjugated substrate ; nonapeptide ; reduced 8-D space ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The specificity of UDP-Gal-NAc:polypeptide N-acetylgalactosaminytransferase (GalNAc-transferase) is consistent with the existence of an extended site composed of nine subsites, denoted by P4, P3, P2, P1, P0, P1′, P2′, P3′, and P4′, where the acceptor at P0 is being either Ser or Thr. To predict whether a peptide will react with the enzyme to form a Ser- or Thr-conjugated glycopeptide, a vector projection method is proposed which uses a training set of amino acid sequences surrounding 90 Ser and 106 Thr O-glycosylation sites extracted from the National Biomedical Research Foundation Protein Database. The model postulates independent interactions of the 9 amino acid moieties with their respective binding sites. The high ratio of correct predictions vs. total predictions for the data in both the training and the testing sets indicates that the method is self-consistent and efficient. It provides a rapid means for predicting O-glycosylation and designing effective inhibitors of GalNAc-transferase. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340210205
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  • 96
    Electronic Resource
    Electronic Resource
    Crystallization, molecular replacement solution, and refinement of tetrameric β-amylase from sweet potato (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 105-117 
    Details
    ISSN: 0887-3585
    Keywords: crystals ; X-ray structure ; (α/β)8 barrel protein ; 222 molecular symmetry ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Sweet potato β-amylase is a tetramer of identical subunits, which are arranged to exhibit 222 molecular symmetry. Its subunit consists of 498 amino acid residues (Mr 55,880). It has been crystallized at room temperature using polyethylene glycol 1500 as precipitant. The crystals, growing to dimensions of 0.4 mm × 0.4 mm × 1.0 mm within 2 weeks, belong to the tetragonal space group P42212 with unit cell dimensions of a = b = 129.63 Å and c = 68.42 Å. The asymmetric unit contains 1 subunit of β-amylase, with a crystal volume per protein mass (VM) of 2.57 Å3/Da and a solvent content of 52% by volume. The three-dimensional structure of the tetrameric β-amylase from sweet potato has been determined by molecular replacement methods using the monomeric structure of soybean enzyme as the starting model. The refined subunit model contains 3,863 nonhydrogen protein atoms (488 amino acid residues) and 319 water oxygen atoms. The current R-value is 20.3% for data in the resolution range of 8-2.3 Å (with 2 σ cut-off) with good stereochemistry. The subunit structure of sweet potato β-amylase (crystallized in the absence of α-cyclodextrin) is very similar to that of soybean β-amylase (complexed with α-cyclodextrin). The root-mean-square (RMS) difference for 487 equivalent Cα atoms of the two β-amylases is 0.96 Å. Each subunit of sweet potato β-amylase is composed of a large (α/β)8 core domain, a small one made up of three long loops [L3 (residues 91-150), LA (residues 183-258), and L5 (residues 300-327)], and a long C-terminal loop formed by residues 445-493. Conserved Glu 187, believed to play an important role in catalysis, is located at the cleft between the (α/β)8 barrel core and a small domain made up of three long loops (L3, L4, and L5). Conserved Cys 96, important in the inactivation of enzyme activity by sulfhydryl reagents, is located at the entrance of the (α/β)8 barrel. © 1995 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340210204
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  • 97
    Electronic Resource
    Electronic Resource
    A new protein folding recognition potential function (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 127-129 
    Details
    ISSN: 0887-3585
    Keywords: inverse folding ; polar fraction ; potential of mean force ; Boltzmann device ; sequence-structure alignment ; conformation recognition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: On the study of protein inverse folding problem, one goal is to find simple and efficient potential to evaluate the compatibility between structure and a given sequence. We present here a novo empirical mean force potential to address the importance of electrostatic interactions in protein inverse folding study. It is based on protein main chain polar fraction and constructed in a way similar with Sippl's from a database of 64 known independent three-dimensional protein structures. This potential was applied to recognize the protein native conformations among a conformation pool. Calculated results show that this potential is powerful in picking out native conformations, in addition it can also find structure similarity between proteins with low sequence similarity. The success of this new potential clearly shows the importance of electrostatic factors in protein inverse folding studies. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340210206
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  • 98
    Electronic Resource
    Electronic Resource
    Local moves: An efficient algorithm for simulation of protein folding (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 73-82 
    Details
    ISSN: 0887-3585
    Keywords: protein folding ; protein structure ; genetic algorithms ; Monte Carlo simulations ; ring closure ; dihedral angles ; structure prediction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have enhanced genetic algorithms and Monte Carlo methods for simulation of protein folding by introducing “local moves” in dihedral space. A local move consists of changes in backbone dihedral angles in a sequential window while the positions of all atoms outside the window remain unchanged. We find three advantages of local moves: (1) For some energy functions, protein conformations of lower energy are found; (2) these low energy conformations are found in fewer steps; and (3) the simulations are less sensitive to the details of the annealing protocol. To distinguish the effectiveness of local move algorithm from the complexity of the energy function, we have used several different energy functions. These energy functions include the Profile score (Bowie et al., Science 253:164-170, 1991), the knowledge-based energy function used by Bowie and Eisenberg 1994 (Proc. Natl. Acad. Sci. U.S.A. 91:4434-4440, 1994), two energy terms developed as suggested by Sippl and coworkers (Hendlich et al., J. Mol. Biol. 216:167180, 1990), and AMBER (Weiner and Kollman, J. Comp. Chem. 2:287-303, 1981). Besides these energy functions we have used three energy functions that include knowledge of the native structures: the RMSD from the native structure, the distance matrix error, and an energy term based on the distance between different residue types called DBIN. In some of these simulations the main advantage of local moves is the reduced dependence on the details of the annealing schedule. In other simulations, local moves are superior to other algorithms as structures with lower energy are found. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340230109
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  • 99
    Electronic Resource
    Electronic Resource
    Effects of cavity-creating mutations on conformational stability and structure of the dimeric 4-α-helical protein ROP: Thermal unfolding studies (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 83-96 
    Details
    ISSN: 0887-3585
    Keywords: ROP protein ; 4-α-helix-bundle ; protein stability ; cavity mutations ; heat capacity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The structural and energetic perturbations caused by cavity-creating mutations (Leu-41 → Val and Leu-41 → Ala) in the dimeric 4-α-helical-bundle protein ROP have been characterized by CD spectroscopy and differential scanning calorimetry (DSC). Deconvolution of the CD spectra showed a decrease in α -helicity as a result of the amino acid exchanges that follows qualitatively the overall decrease in conformational stability. Transition enthalpies are sensitive probes of the energetic change associated with point mutations. ΔH0 values at the respective transition temperatures, T1/2 (71.0, 65.3, and 52.9°C at 0.5 mg/ml) decrease from 580 ± 20 to 461 ± 20 kJ/(mol of dimmer) and 335 ± 20 kJ/(mol of dimmer) for wildtype ROP (Steif, C., Weber, P., Hinz, H.-J., Flossdorf, J., Cesareni, G., Kokkinidis, M. Biochemistry 32:3867-3876, 1993), L41V, and L41A, respectively. The conformational stabilities at 25°C expressed by the standard Gibbs energies of denaturation, ΔGD0, are 71.7, 61.1, and 46.1 kJ/(mol of dimmer). The corresponding transition enthalpies have been obtained from extrapolation using the cpD(T)and cpN(T) functions. Their values at 25°C are 176.3, 101.9, and 141.7 kJ/(mol of dimmer) for wild-type ROP, L41V, and L41A, respectively. When the stability perturbation resulting from the cavity creating mutations is referred to the exchange of 1 mol of CH2 group, the average ΔΔGD0 value is -5.0 ± 1 kJ/(mol of CH2 group). This decrease in conformation stability suggests that dimeric ROP exhibits the same susceptibility to Leu → Yal and Leu → Ala exchanges as small monomeric proteins. Careful determinations of the partial specific heat capacities of wild-type and mutated protein solutions suggest that the mutational effects are predominantly manifested in the native rather than the unfolded state. © 1995 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340230110
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  • 100
    Electronic Resource
    Electronic Resource
    Characterization of crystals of the thermostable DNA polymerase I from thermus aquaticus (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 111-114 
    Details
    ISSN: 0887-3585
    Keywords: replication ; amplification ; PCR ; enzyme ; thermostability ; x-ray ; diffraction ; synchrotron ; three-dimensional ; structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Thermus aquaticus DNA polymerase I is an enzyme that is of both physiological and technological interest. It carries out template-directed polymerization of DNA at elevated temperatures and is widely used in polymerase chain reaction (PCR). We have obtained crystals of the enzyme that diffracts X-rays to at least 3.0 Å resolution in a cubic space group. Determination of the three-dimensional structure of the native enzyme along with those of relevant complexes will greatly enhance our knowledge of molecular events involved in DNA replication, will permit improvements in PCR, and will add to our knowledge of the structural bases of thermo stability in proteins. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340230112
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