摘要:

Syntheses of two sequential polytctrapeptide models, H‐(Val‐Ala‐Pro‐Gly)n‐Val‐OMe and H‐(Val‐Pro‐Gly‐Gly)n‐Val‐OMe via the p‐nitrophenyl ester method are described. The p‐nitrophenyl ester method gave high yields (85%–100%) of large molecular weight polymers. H‐(Val‐Pro‐Gly‐Gly)n‐Val‐OMe exhibited the interesting property of coacervation on raising the temperature of aqueous solutions while H‐(Val‐Ala‐Pro‐Gly)n‐Val‐OMe precipitates irreversibly under similar conditions.Whereas non‐dialyzed lower molecular weight polymers of H‐(Val‐Pro‐Gly‐Gly)n‐Val‐OMe with n = 8 to 40 did not coacervate, but did show a transition to increased intramolecular order on raising the temperature of aqueous solutions above 50°C, the dialyzed higher molecular weight polymer, n>40, does coacervate beginning at about 50°C. This demonstrates the molecular weight dependence of coacervation and also suggests the importance to coacervation of side chain interactions in the Val‐Pro sequence. The increase in intramolecular order, seen as the formation of a 14‐atom hydrogen‐bonded ring

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02829.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The synthesis of two polyhexapeptides is reported. The polyhexapeptides are H‐(Val6‐Ala1‐Pro2‐Gly3‐θ4‐Gly5)n‐Val‐OMe where θ= Vol or Lys with a mole ratio of 3.5:1 and H‐(Val6‐Ala1‐Pro2‐Gly3‐Lys4‐Gly5)n‐Val‐OMe. The first polymer was utilized with a previously synthesized polyhexapeptide, H‐(Val6‐Ala1‐Pro2‐Gly3‐θ‐Gly5)n‐Val‐OMe where θ was either Val4or Glu4at a mole ratio of 3.5:1, to obtain an intermolecular cross‐linked matrix by means of primary amide bond formation between the γ‐carboxyls of the Glu residues of one copolymer and the α‐amino groups of the Lys residues of the other copolymer. The cross‐linking reaction was run during a temperature‐elicited phase separation with flow orientation of the polymers. An insoluble, non‐elastomeric, cross‐linked, polyhexapeptide matrix was obtained. The nature of the insoluble polyhexapeptide matrix was well‐demonstrated by the polymer, H‐(Val6‐Ala1‐Pro2‐Gly3‐θ4‐Gly5)n‐Val‐OMe where θ4is Vol or Lys, which could be formed into cellophane‐like, non‐elastomeric sheets which would tear and which could be shown by microscopy to have sharp edges. This very different property of the polyhexapeptide of tropoelastin as compared to the elastomeric polypentapeptide of tropoelastin is discussed in terms of a different structural role.The purity of key intermediate hexamers and of the polyhexapeptides

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02830.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Copolypeptides with alternating hydrophilic and hydrophobic residues were prepared, and their ability to form β‐structures in aqueous solutions was investigated by circular dichroism. Optically pure samples of poly (Lys‐Leu‐Lys‐Leu) and poly (Leu‐Glu‐Leu‐Glu), obtained via the 2‐hydroxyphenyl esters, undergo a coil‐to‐β transition in presence of salt. The β‐structures obtained under identical conditions with partially racemized samples of poly (Leu‐Lys)Npand poly (Leu‐Glu)Np, prepared by polycondensation of the corresponding dipeptide p‐nitrophenyl esters, appear to be less regular. Non‐alternating poly (Gly‐Lys‐Leu‐Lys‐Leu) does not form β‐structures in presence of NaCl as does alternating poly (Lys‐Leu‐Lys‐Leu) indicating that the amino acid sequence can dram

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02831.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Potassium cyanide catalyzed transesterification with methanol, ethanol or benzyl alcohol was found to be effective for the removal of a variety of protected amino acids and peptides from the Merrifield resin after solid phase peptide synthesis. A peptide was released from the solid support as the methyl, ethyl or benzyl ester by stirring the resin in the appropriate dry alcohol at room temperature for 24 h in the presence of 1% potassium cyanide. No racemization of the C‐terminal amino acid was observed in the transesterification of Z‐Ala‐Val‐resin to Z‐Ala‐Val‐OBzl. The possible occurrence of cyclization and αåβ shift of aspartyl residues was investigated for transesterification reactions in benzyl alcohol. Potassium cyanide catalyzed transesterification with benzyl alcohol has been used for the synthesis of arginine vasotocin. When carried out in 95% aqueous alcohol, the peptide‐resin bond was first transesterified and subsequently saponified; side chain ester protecting groups were transesterified but not saponified under these conditions. However, the saponification step was slow when either the peptide‐resin bond or the transesterifying alcohol was sterically hindered, and was accompanied by sign

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02832.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ab initioCalculations at the Gaussian‐70 STO‐3G and 4‐31G basis levels have been carried out for (HS)2and (CH3S)2. Cystine was investigated at the STO‐3G level. The STO‐3G energy minimized geometry agrees well with experiments for (HS)2and (CH3S)2. The barriers to internal rotation arepredictedto be (at the 4.31G level): (HS)2, cis8.5 kcal, trans3.03 kcal; (CH3S)2, cis 18.47 kcal, trans

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02833.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Three analogs of β‐endorphin have been synthesized by the solid‐phase method: βc‐endorphin‐(1–5)‐(28–31), βc‐endorphin‐(6–31) and βh‐endorphin‐(1–5)‐(16–31). The analgesic activities of these synthetic peptides relative to that of the parent molecule are reported. All three peptides at high doses exhibit either no or much weaker analgesic activity than β‐endorphin. These data suggest that the entire β‐endorphin molecule is nece

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02834.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Physicochemical parameters were determined on glycyl‐L‐leucine hydrolase (glycyl‐leucine dipeptidase, EC 3.4.13.2) and aminoacyl‐L‐proline hydrolase (proline dipeptidase, EC 3.4.13.9), purified from pig small intestine. The native molecular weights were found to be 115,000 and 113,000, respectively, as determined by a sedimentation equilibrium technique. Under denaturing conditions the molecular weights were found to be 51,000 and 63,200, respectivemy, using the same technique. It is concluded that each dipeptidase is composed of two subunits of equal molecular weight.The two dipeptidases have the same Stokes radius, 4.2 nm, analysed by gel chromatography. The sedimentation coefficients were found to be 5.8 S and 6.5 S and the intrinsic viscosities 5.4 ml/g and 5.8 ml/g, respectively. For both dipeptidases the measured physicochemical parameters are in accordance with the model of a prolate ellipsoid of revolution, having an axial ratio o

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02835.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

A comparative study of the conventional three‐fold torsional potential functions (referred to as “Old V”), the potential function having zero φ barrier and a twofold ψ‐barrier, proposed from this laboratory (“Int V”), and those developed recently in this laboratory from the study of dipeptide conformations in protein crystal structures (“New V”) has been carried out by comparing theoretically calculated and experimentally observed NH‐CαH coupling constants from n.m.r. studies and the relative occupancy of hydrogen‐bonded conformations from i.r. studies of dipeptide model systems. It is observed that no fully satisfactory agreement with both n.m.r. and i.r. data is possible in any one of the three functions. For the hydrogen bond‐disrupting solvent DMSO, (NH‐CαH) coupling constant values were predicted equally well in all three. However, only for New V are values of the constants A (= 8.62), B (= ‐2.33), C (= 1.51) as obtained by the least‐squares method in the expression J(θ) = A cos2θ+ B cos θ+ C sin2θ such that J‐values in excess of 10Hz, observed experimentally in some cases, are permissible. However, the same potential function yields unsatisfactory agreement in the case of hydrogen bond‐promoting solvent CCl4. This was interpreted to be because the potential function concerned was obtained from data in solid state where solvent interaction is absent.In view of the lack of satisfactory agreement with the solution data for all three potential functions, it was concluded that solvent effects other than the promotion of intramolecular hydrogen bonding, which were ignored in the present study, must be taken into account for better prediction of experimental da

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02836.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The 51‐residue peptide ovine β‐lipotropin‐(41–91) has been synthesized by the solid‐phase method in about 5% overall yield. The synthetic product was characterized by partition chromatography on agarose gel, thin‐layer chromatography in two solvent systems, paper electrophoresis at two pH values, polyacrylamide gel electrophoresis, amino acid analyses of acid and enzymic hydrolysates, and bioassay for lipolytic and melanotropic activities. The synthetic peptide is about 5.4 times as active on a weight basis as ovine β‐lipotropin in the lipolytic assay. In the melanotropic assay, it was about 2.4 times more active than the β‐lipotropin but only 5% as active as bovine β‐melanotropin. It had negligible opiate activity in the g

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02837.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

At neutral pH the far ultraviolet circular dichroism (CD) spectrum of alkaline mesentericopeptidase is dominated by two negative bands: at 208 and 220 nm. The near ultraviolet CD spectrum is characterized by a large negative band at 277nm, a shoulder near 286nm and a small positive band at 297nm. The introduction of phenylmethanesulfonyl (PMS) group on the serine residue at the active site does not alter the intensity and the wavelength position of the bands.In contrast to the other alkaline bacterial proteases, which are remarkably resistant to denaturation by urea, mesentericopeptidase was unfolded in the presence of this reagent at neutral pH. The denaturation reactions in the presence of 9.5 M urea of both native and PMS‐mesentericopeptidase followed first order kinetics. The introduction of PMS‐group on the active‐site serine lowered the conformational stability of the enzyme. In the first 3h PMS‐mesentericopeptidase was denaturated 2.5 times faster than native protease.In the presence of 9.5 M urea at natural pH alkaline mesentericopeptidase lost its catalytic activity. The loss of enzymatic activity correlated with the unfolding of the protein molecule and also followed first‐order

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02838.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY