A. I. Miroshnikov

The conformation of gramicidin S and its N,N′-diacetyl derivative in solutions

Conformational study of gramicidin S and N,N′-diacetyl gramicidin S has been carried out by a number of techniques. Optical rotatory dispersion measurements showed both cyclodecapeptides to possess similar conformations in different solvents. Quantitative infra red studies in dilute chloroform solutions lead to the inference that there are ca. six intramolecular hydrogen bonds in the N,N′-diacetyl derivative. Of these deuterium exchange rates by proton magnetic resonance measurements indicate four strong H-bonds due to the Val and Leu NH groups and two weaker bonds due to the Orn α-NH groups. The NH-CαH proton coupling constants show the protons of this fragment to be trans in Val, Orn and Leu residues and gauche in D-Phe residues. The data obtained provide unequivocal proof of the Hodchkin-Oughton-Schwyzer model of gramicidin S, for which φ and ψ coordinates are given.

Conformation of the Na+ complex of antamanide in solution

Abstract The conformational states of the cyclodecapeptide antamanide and of its Na+ complex have been studied by a number of spectroscopic methods. Two conformers were found for antamanide of which one, existing in non polar solvents has all six NH groups hydrogen bonded. A three dimensional structure of the antamanide·Na+ complex has been proposed containing four intramolecular hydrogen bonds formed by the amide CO and NH groups. The sodium ion is held in the inner cavity by ion-dipole interaction with six amide carbonyls. The proposed structure explains the efficiency and selectivity of the antamanide complexation reaction

Solution spatial structure of apamin as derived from NMR study.

Apamin, the minor active component of bee venom, is unique in being the smallest known peptide neurotoxin with an excitatory effect on the central nervous system and is also the only known polypeptide that passes the blood-brain barrier [ 11. It becomes a very useful instrument in the study of mechanism of nerve pulse transmission [2]. The chemical structure of apamin, an octadecapeptide with two disulphide bridges, has been determined [3-51: digital pH meter (Orion Research model 601). The experimental pH dependences of chemical shifts were analyzed by multiparametric non-linear least squares curve-fitting computer software [ 111.

The rational use of mass spectrometry for amino acid sequence determination in peptides and extension of the possibilities of the method

It has been shown earlier by us and by others that mass spectrometry can be used for the elucidation of the primary structure of peptides containing residues of all the ammo acids commonly found in proteins, N-acylpeptide esters being most suitable for this purpose (see [ 1,2] and references therein). Mass spectrometric determination of amino acid sequences is based on fragmentation of N-acylpeptide esters involving rupture of amide (ester) bonds and localization of the positive charge at the C-terminus of the amino acid fragments of type (I). These fragments decompose further., consecutively eliminating amino acid residues either in one (I + III) or in two steps (I+II+III), in the latter case via aldimine fragments (II). This pattern of fragmentation provides ammo acid and/or aldimine fragment ions arising from the partial cleavage of every amide bond, the difference in m/e of the fragments allowing the determination of the amino acid sequence in the peptide being investigated. The peaks due to

The effect of antamanide and perhydroantamanide on the permeability of model and biological membranes

Untersuchungen mit Antamanid und Perhydroantamanid deuten darauf hin, dass für letzteres die Beeinflussung des Transportes von Na+- und K+-Ionen durch Membranen von Bedeutung sein kann.

A new convenient method for the synthesis of tert.-butyloxycarbonylhydrazine

Es wird eine neue einfache Methode für die Darstellung von tert.-Butylcarbazate beschrieben.

Use of electron-spin-resonance spectroscopy for studying the conformational states of peptides gramicidin S

Summary1. A new method has been proposed for studying the conformational states of peptides in solutions which is based on a consideration of the ESR spectra of their spin-labeled derivatives.2. The synthesis of derivatives of gramicidin S containing one and two iminoxyl radicals in the2Orn and7Orn side chains has been effected.3. On the basis of an analysis of the ESR spectra of the compounds obtained at −196°C and 30–62°C, conformations of the side chains of modified ornithine residues in chloroform and ethanol have been proposed.

Synthesis and properties of symmetrical analogs of antamanide

Summary1. The synthesis of four symmetrical analogs of antamanide has been performed.2. The capacity of the analogs obtained for complex formation with Na+ and K+ ions in ethanolic solution has been studied.

Conformational states of antamanide and its analogs in solutions

Summary1. A preferred conformation of antamanide in nonpolar solvents has been proposed with the aid of a wide group of physicochemical methods and theoretical analyses.2. On the basis of spectroscopic results, the hypothesis has been put forward of the existence of two other forms of antamanide (B and C) which form on passing from nonpolar to polar media.

Synthesis and some physicochemical properties of antamanide, retroantamanide, and perhydroantamanide

SummaryThe synthesis of antamanide, retroantamanide, and perhydroantamanide has been effected. It has been shown that the inversion of the direction of acylation — the equilibrium interchange of the valine and alanine residues (retroantamanide) — lowers the stability of the complexes with sodium and potassium in ethanolic solutions, while the replacement of the phenyl groups by cyclohexyl groups has practically no effect on complex formation.