摘要:

The various types of conformationally restricted peptides obtained by short‐range cyclizations, from residueito residuei+ 1, are presented. Relevant examples of N ⇆ Cx, C′⇆ Cx, N ⇆ C′, Cx⇆ Cx, C′⇆ C′ and N ⇆ N cyclizations are reported and the pertinent literature listed. In the discussion emphasis is place on the conformational consequences for peptides from the incorporation of

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00052.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

TheC‐terminal tetrapeptide, Trp‐Met‐Asp‐Phe‐NH2, is a full agonist of gastrin, but des‐Phe analogues, including Boc‐Trp‐Met‐Asp‐NH2, are antagonists. To ascertain the minimum structural requirement for an antagonist, we used conventional solution phase methodology to synthesize analogues with further modifications including removal of the α‐amino group of Trp, conversion of the indole to a phenyl ring, and methylation of amide bonds. These analogues were tested for their effect on pentagastrin‐stimulated acid release in dogs surgically prepared with a gastric fistula. When infused intravenously at a dose of 20pmolkg−1h−1, the peptides significantly inhibited acid secretion. The extent of inhibition ranged from 12% to 60%. Thus, tripeptide analogues based on theC‐terminal sequence of gastrin act as potent and specific antagonists of gas

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00053.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

We have previously demonstrated that the peptide Boc‐l‐Trp‐l‐Leu‐β‐Ala is a potent and specific antagonist of pentagastrin‐stimulated acid secretion in both the rat and the dog. Using conventional solution phase methodology, the analogue biotinyl‐l‐Trp‐l‐Leu‐β‐Ala was prepared in reasonable yield and purity and applied to cryostat sections of rat intestinal and other tissues. The sections were exposed to 5–10 μg of peptide and the bound analogue was visualised using streptavidin‐fluorescein. The binding of the analogue was demonstrated in sections from fundus, duodenum, ileum, colon, and lung. However, the analogue failed to bind to tissue from the pancreas, heart, kidney, or liver. The binding of the probe was greatly reduced or completely inhibited by preincubation with Boc‐l‐Trp‐l‐Leu‐β‐Ala, pentagastrin, or gastrin 1–17. The distribution of the cells recognised by the probe was consistent with the distribution of histamine‐containing enterochromaffin‐like cells. The results of this study may have some bearing on current theories

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00054.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The high molecular weight protein was isolated from rapeseed and characterised. Six subunits were isolated in SDS (0.01%) solution on polyacrylamide gel electrophoresis and by gel filtration on Sephadex G‐100. Reassociation by removing SDS by co‐dialysis, against 10mM sodium phosphate buffer (pH 7.9) was done and the yield was about 90%. The reconstituted protein was indistinguishable from the intact protein in all respects. The subunits isolated from the native protein and the reconstituted protein were found to have identical molecular weights andN‐terminal amino acids. No disulphide bonds were observed in the subunit association. Amino acid analysis of the proteins and the six subunits was performed and the number of each amino acid residue calcu

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00055.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A full theory of the conformations of biopolymers requires a method for treating the effects of solvent on the induced structures. This is especially critical in aqueous solvent where hydrogen‐bonding and dielectric shielding play major roles in determining the relative stability of conformers. Calculations of peptide conformations on a free energy surface are contrasted with the traditional sort of calculations which employs a simple potential energy function (in vacuo). The method employs a pairwise decomposable free energy surface determined by approximate analytical statistical mechanical theory. Applications are presented for tripeptides of alanine and glycine in water. This method, with precomputed free energy functions, takes the same amount of time and effort as traditional molecular mechanicsin vacu

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00056.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The interaction of methionine and leucine enkephalin with phosphatidylserine and phosphatidylcholine was studied by optical spectroscopy techniques. The data reported indicate that with both peptides the binding is controlled by ionic parameters. They also indicate that the differences in the binding behavior of the two peptides induced by changing these parameters are minor. Non‐ionic interactions are also important in the binding phenomena, but the above observations hold in this case as well. Finally, the tridimensional structure of both enkephalins appears to be modified in the presence of phospholipids. Moreover, the changes induced by these lipids appear to differ from one peptide to the othe

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00057.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The peptide corresponding to the (66–104) sequence of horse heart cytochrome c and its carboxyamide analog, selectively modified at the critical Met80residue, have been synthesized by stepwise solid‐phase methods on PAM and BHA resins respectively. The correctness of the growing peptide chain as well as the homogeneity of the final products have been monitored by several analytical methods including quantitative Edman degradation. After HF cleavage both peptides were purified by semipreparative HPLC. The overall yields were 24% for the native (66–104) and 10% for the carboxyamide analog. The homogeneity of the purified synthetic peptides have been determined by different criteria including HPLC, amino acid composition, Edman degradation, electrophoresis, and tryptic peptide mapping. The synthetic fragments have been utilized for preliminary semisynthesis experiments with the native [Hse〉65](1–65)H heme

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00058.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

An improved way to obtain Ψ[CH2O] pseudodipeptide units is proposed, involving an intramolecular Williamson's reaction, with displacement of bromine by an alkoxide, instead of the classical intermolecular one. Until now, Ψ[CH2O] pseudodipeptide synthesis done by this new method, has used a protected form of the amino alcohol hydroxyl group to prepare the acyclic precursor. In the present paper, the use of an active ester of the brominated carboxylic acid avoids this protection step. The pseudodipeptides Ac‐GlyΨ[CH2O]‐d,l‐Ala‐OH and Ac‐Ser(Bzl)Ψ[CH2O]‐d,l‐Ala‐OH were obtained in high yields, through a delta‐lactam intermediate, which furthermore allows the determination of the absolute configuration of compounds using HPLC and appropriate nuclear magnetic reson

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00059.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Peptide synthesis catalysed by papain was studied using thio‐α‐amino acids (S‐acids) as a carboxyl component. It was found, for example, that with Z‐AlaSH (pK 2.70) the maximal yield of the peptide Z‐AlaValNH2was obtained at pH 8–8.5. A two‐fold excess of Z‐AlaSH furnished peptides with yields close to 100%. Thio‐amino acids with bulky side groups, for example, Z‐IleSH, Z‐Asp(OBut)SH, gave peptides with a low yield. Papain interacts with Z‐AlaSH better th

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00060.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Crystals ofdl‐arginine hemisuccinate dihydrate (I)(monoclinic; P21/c; a = 5.292, b = 16.296, c = 15.203 Å; α= 92.89°; Z = 4) andl‐arginine hemisuccinate hemisuccinic acid monohydrate (II) (triclinic; P1; a = 5.099; b = 10.222, c = 14.626 Å; α= 77.31, β= 89.46, γ= 78.42°; Z = 2) were grown under identical conditions from aqueous solutions of the components in molar proportions. The structures were solved by direct methods and refined to R = 0.068 for 2585 observed reflections in the case of (I) and R = 0.036 for 2154 observed reflections in the case of (11). Two of the three crystallographically independent arginine molecules in the complexes have conformations different from those observed so far in the crystal structures containing arginine. The succinic acid molecules and the succinate ions in the structures are centrosymmetric and planar. The crystal structure of (II) is highly pseudosymmetric. Arginine‐succinate interactions in both the complexes involve specific guanidyl‐carboxylate interactions. The basic elements of aggregation in both the structures are ribbons made up of alternating arginine dimers and succinate ions. However, the ribbons pack in different ways in the two structures. (II) presents an interesting case in which two ionisation states of the same molecule coexist in a crystal. The two complexes provide a good example of the effect of change in chirality on stoichiometry, conformation, aggregation, and ionisation state in

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00061.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY