Aggregation, hydrogen bonding and thermodynamic studies on tetrapeptide micelles

Abstract

The temperature dependence of critical micelle concentration (c.m.c.), aggregation number, standard Gibbs energy change (A,G"), enthalpy change (A,/+") and entropy change ( A m s o ) of micelle formation, and proton chemical shifts of the TFA Tyr-Gly-Phe-Ala-OBz peptide (TFA is trifluoroacetic acid) have been presented in the light of NH. . .O=C< hydrogen-bond formation and forces implicated in micellization. It has been found that the c.m.c. of the tetrapeptide increases with increase in temperature from 20 to 40"C, whereas it decreases at temperatures above 40 "C. Moreover, the temperature dependence of the aggregation number, proton chemical shifts and thermodynamic results suggest that intramolecular H bonds are formed at temperatures in the range 2040°C (secondary level of structure) owing to hindrance of rnicelle formation, whereas above 40 "C the intramolecular H bonds of the peptide are broken as micellization increases which demonstrates a tertiary level of structure. It has also been found that the temperature of 40°C appears very significant in that it is close to the temperature at which both the enthalpy and entropy of micellization change sign, which presumably relates to the opposing temperature dependences of hydrophobic and electrostatic interactions, the inverse temperature dependence of hydrophobic interactions reflecting changes in water structure.

Micelle Formation by a Fragment of Human Islet Amyloid Polypeptide

“…3). The increasing acidity indicates that enhanced release of H 1 ions into solution occurs upon micellization, an effect that has been previously observed with other micelle-forming peptides (Kumar et al, 1996;Mandal and Jayakumar, 1994). Because the fragment hIAPP 20-30 does not contain any titratable side groups (see Fig.…”

Properties of a new renewable sesame protein adhesive modified by urea in the absence and presence of zinc oxide

“…B. by examining NMR experiments through the plots of changes in the chemical shis as a function of temperature. 30 The key absorption peaks of the USP/ZUSP adhesives were located at 1668 and 1624 cm À1 , which were Fig. 3 Bonding strength of the USP/ZUSP adhesives.…”

Thermodynamics studies on tyrosine-hydantoin drug–cetyltrimethylammonium bromide mixed micellar system

“…amitriptyline hydrochloride, imipramine hydrochloride, chlorpromazine hydrochloride and, promethazine hydrochloride in presence of additives have recently been evaluated [11][12][13][14][15]. Micellar characteristics of various peptides, collagens, polymers in aqueous and non-aqueous media and their interactions with various surfactant micelles have widely been studied [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] in light of aggregation, H-bonding, geometry, correlation times, conformation, hydrodynamic and thermodynamic studies.…”