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Janusz W. Krajewski Przemysław Gluziński Sławomir Jarosz Aleksander Zamojski Jānis Bleidelis Anatolii Mishnyov Andrejas Ķemme 《Carbohydrate research》1985,144(2):183-195
Condensation of 6-O-benzyl-7,8-dideoxy-1,2:3,4-di-O-isopropylidene-d-glycero-α-d-galacto-oct-7-ynopyranose with methyl 2,3,4-tri-O-benzyl-6-deoxy-β-d-galacto-heptodialdo-1,5-pyranoside afforded a 2:1 mixture of the 1S and 1R isomers (1a and 1b) of 3-[6(R)-O-benzyl-1,2:3,4-di-O-isopropylidene-α-d-galactopyranos-6-yl]-1-hydroxy-1-(methyl 2,3,4-tri-O-benzyl-6-deoxy-β-d-galactopyranosid-6-yl)propyne. A single crystal of the 1-O-acetyl derivative (1c) of 1a was investigated by X-ray diffraction methods in a four-circle diffractometer. Compound 1c crystallises in the monoclinic system, space group P21 (Z = 2) with cell dimensions a = 14.896(2), b = 8.295(1), c = 20.547(3) Å, and β = 102.66(1)°. The structure was solved by direct methods and refined by a full-matrix, least-squares procedure against 3839 unique reflections (F > 2σF), resulting in a final R = 0.045 (unit weights). The configuration at the new chiral center (C-1) was established as S(d). The galactopyranose rings have conformations 4C1 (tri-O-benzylated moiety) and °S5 + °T2 (di-O-isopropylidenated moiety). The 1,2- and 3,4-O-isopropylidene rings have 3T2 and 2E conformations, respectively. 相似文献
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Summary Isotherms for adsorption of chitinase on chitin and lysozyme on chitin have been determined at two temperatures and rates of hydrolysis of chitin catalysed by these enzymes have been measured at three temperatures and at several enzyme concentrations for each. Ribonuclease, not an enzyme for chitin, and heat-denatured lysozyme and chitinase show reduced or no adsorption to this substrate.Initial hydrolysis rates of chitin by both enzymes are proportional to total enzyme concentrations in the range of concentrations studied. These kinetics cannot, however, be related to the adsorption isotherms because of the non-equilibrium nature of the isotherms. 相似文献
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