摘要:

The fluctuational amplitudes of the amino acid residues in 19 protein molecules are computed by the use of our differential equation model and are analysed statistically to get new information as to their stability, position dependent nature, distribution and group dynamical behaviour, etc. The symmetric/asymmetric distribution of amino acid residues in the protein molecules is described by introducing a parameter called the “flexibility index” for each of the residue types. Finally, the overall flexible nature of the amino acid residues with respect to their spatial positioning is explained and their relationships with the residue properties are deri

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb01258.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

pK values of Glu2, Glu9, and His12 in the lactone and carboxylate forms of C‐peptide at 4.5 and 21°, 0.1mNACl, have been determined from pH‐tritration shifts of n.m.r. signals of the glutamate γ and histidine ring protons. These have been used in an analysis of the well known pH‐induced helix‐coil transition in the C‐peptide lactone. It has been shown that Glu 12 deprotonation results in a twofold increase of the helix content, whereas deprotonation of Glu9 leads to a 28% drop. This latter effect is probably related to Glu−9‐His+12 salt bridge formation. The transition within the pH range 5.5‐7.5 follows exactly the deprotonation curve

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb01259.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

New and already reported thermodynamic data concerning the protonation of a series of diastereoisomeric pairs of dipeptides have been compared with the upfield chemical shifts observed in the PMR spectra of some systems as a consequence of alkyl‐aryl interactions. The enthalpy and entropy changes associated with the protonation of the dipeptides, obtained by potentiometric and calorimetric measurements, together with the PMR data, show the importance of the solvophobic and the electrostatic interactions in the stereoselectivity of these systems. The overall agreement and the differences are discusse

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb01260.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Fifteen physicochemical descriptors of side chains of the 20 natural and of 26 non‐coded amino acids are compiled and simple methods for their evaluation described. The relevance of these parameters to account for hydrophobic, steric, and electric properties of the side chains is assessed and their intercorrelation analyzed. It is shown that three principal components, one steric, one bulk, and one electric (electronic), account for 66% of the total variance in the available set. These parameters may prove to be useful for correlation studies in series of bioactive peptide analogue

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb01261.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Synthetic routes have been developed for the preparation of functionalized amino acid derivatives in which the α‐substituent at carbon 2 is either an aromatic or a heteroaromatic group. The α‐substituent was introduced using an amidoalkylation reaction using boron trifluoride etherate and proceeded in moderate yield with excellent regioselectivity. This protocol permitted the employment of the acid sensitive heterocycles: pyrrole, benzofuran, and indole. The scope and limitations of this procedure have been eval

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb01262.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Nα‐(Phenethylphosphono)‐l‐alanyl‐l‐proline 1, a potent inhibitor of angiotensin converting enzyme, exhibits two31P n.m.r. resonances (intensity ratio one to one), which exchange with a constant (k1) of about 1 s−1and a free energy of activation ΔG*=∼ 20kcal/mol at 23° in deuterated dimethylsulfoxide. Two resonances in exchange are also observed in deuterium oxide at pH 7.5. Thus the exchanging31P resonances report the s‐cis, s‐transconformational equilibrium about the alanyl‐proline peptide bond. Similar results were observed with Nα‐[(O‐phenyl)‐phenethylphosphono]‐l‐alanyl‐l‐proline 2.Nα ‐(O‐phenylphospho)‐l‐alanyl‐l‐proline, 3Nα‐(O, O′‐diphenylphospho)‐l‐alanyl‐l‐proline 4, andNα‐[2‐(2‐oxo‐1, 3, 2‐dioxaphosphiranyl)]‐l‐alanyl‐l‐proline 5 in deuterated dimethyl sulfoxide, deuterium oxide, and deuterochloroform. A13C n.m.r. spectrum of 5 confirmed the presence of s‐cisand s‐

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb01263.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Unsaturated gramicidin S analog, [ΔPhe4,4′]gramicidin S, was synthesized by conventional solution method in order to evaluate the role of the dehydrophenylalanine residues replacingd‐phenylalanine4,4′in stabilizing the bioactive β‐shect conformation. The dehydrophenylalanine (ΔPhe) moiety was introduced by dehydroazlactonization of the β‐phenylserine residue. The [ΔPhe4,4′]gramicidin S prepared by this method showed very strong antimicrobial activities against Gram‐positive bacteria, but not against Gram‐negative ones. Several lines of spectroscopic evidence indicated that [ΔPhe4,4′] gramicidin S has a reinforced β‐sheet backbone conformation necessary for a full biological activity of gramicidin S. These results suggested that :α,β‐dehydrogenation of the amino acid residue in a cyclic peptide ca

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb01264.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Allysine, which is synthesized enzymaticallyin vivostarting from lysine, is a very important crosslink precursor in proteins. We describe the chemical synthesis of allysine derivatives starting from 3,4‐dihydro‐2H‐pyran. Two independent synthetic routes to prepare allysine peptides and derivatives are presented. The synthesized compounds are characterized by spectroscopic methods including13C‐n.m.r. The reactivity of the aldehyde function is shown to be extremely high. An unexpected nucleophilic attack of the allysine amide nitrogen upon the aldehyde group is described. This ring‐closure reaction is not expected to take place in native collagen; however, denatured peptides containing allysine may react similarly as the model peptides presented in t

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb01265.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY