Conformation of poly(L‐arginine). I. Effects of anions

Abstract

SynopsisThe conformational transition of poly(L-arginine) by binding with various mono-, di-, and polyvalent anions, especially with SO:-, was studied by CD measurements. The intramolecular random coil-to-a-helix conformational transition and the subsequent transition to the 0-turn-like structure was caused by binding with SO:-. The binding data obtained from equilibrium dialysis experiments showed that the a-helical conformation of poly(i-arginine)is stabilized a t a 1:3 stoichiometric ratio of bound SO: -to arginine residue; a t higher free SO:-concentrations, the a-helix converts to the 0-turn-like structure accompanied by a decrease in the amount of bound SO:-. The same conformational transition of poly(L-arginine) also occurred in the solutions of other divalent anions (SO:-, COZ-, and HPO:-) and polyvalent anions (P20$-, PsO:;). Among the monovalent anions examined, Cloy and dodecyl sulfate were effective in inducing a-helical conformation, while the other monovalent anions (OH-, C1-, F-, H2POI, HCO,, and C10,) failed to induce poly(L-arginine) to assume the a-helical conformation. Thus, we noticed that, except for dodecyl sulfate, the tetrahedral structure is common to the a-helix-forming anions. A well-defined model of the a-helical poly(Larginine)/anion complex was proposed, in which both the binding stoichiometry of anions to the arginine residue and the tetrahedral structure of anions were taken into consideration. Based on these results, it was concluded that the tetrahedral-type anions stabilize the a-helical conformation of poly(L-arginine) by crosslinking between two guanidinium groups of nearby side chains on the same a-helix through the ringed structures stabilized by hydrogen bonds as well as by electrostatic interaction. Throughout the study it was noticed that the structural behavior of poly(L-arginine) toward anions is distinct from that of poly(L-lysine).

Conformational studies of basic poly (α-amino acid)s in reversed micelles

“…It is suggested by these results that the a-helical conformation of poly(L-arginine) is formed as a resuk of the contributions of electrostatic and hydrophobic interactions, similar to the cases of poly(L-lysine) and poly(Lornithine). It should be noted here that the interaction between the cationic group of the side chain ofpoly(Larginine) and the anionic group of AOT may be effectively produced not only by the usual electrostatic interaction, but also by the hydrogen bond as shown in the following way, according to the suggestion of Zamma et al [9], in the case of the interaction between the guanidinium group and the sulfate anion. The guanidinium group is considered to be the water structure breaking property [17].…”

“…In the case of poly(L-arginine), an a-helical conformation is induced by the addition of SDS to aqueous solutions [9].…”

Pharmacological characterization of polycation‐induced rat hind‐paw oedema

“…This result indicates that other factors in addition to electrostatic forces, such as hydrophobic bonding and chain stiffness, modulate polycation-membrane interactions. POIY-Llysine has lower hydrophobic bonding (Ichimura & Zama, 1977) and non-specific electrostatic binding ability (Ichimura et al, 1978) than poly-L-arginine. There are also differences in the ability of these polycations to display helical conformation which increases chain stiffness, thus decreasing chain interaction with charged surfaces (Ichimura et al, 1978).…”

Purified Ribulose-P2 carboxylase from wheat with high specific activity and with fast activation

“…This phenomenon probably reflects the ability of SO~-ions (in common with Pi and PPi ions) to bind to a-helix structures in proteins [11]. Thus interconversion between E s and Er may involve changes in a-helix content and E r formation is possibly facilitated in the presence of these oxyanions.…”