Monolayers of amino acid-type amphiphiles

Adv Colloid Interface Sci. 2023 Sep 20;321:103001. doi: 10.1016/j.cis.2023.103001. Online ahead of print.ABSTRACTThe monolayer characteristics of selected N-alkanoyl substituted α-amino acid are studied with the objective to demonstrate the specific effect of the chemical structure of the polar head group which is highlighted with the D- and L-enantiomers of the following selected examples: R-alanine, R-serine, R-threonine, R-allo-threonine, and R-aspartic acid (R = C16, C18). The thermodynamic effect of the head group variation is studied. Experimental π-A isotherms of the N-tetradecyl-L-alanine monolayers show similar behavior as those of usual amphiphiles. The -CH3-group in R-alanine with the simplest head group structure is substituted by a -CH2-OH group in R-serine and serine methylester and by a -CH- CH3-OH group in R-threonine (or allo-threonine) and threonine methylester. The introduction of the methyl group in 3-position of serine (serine to 3-methyl-serine = threonine) shifts the characteristic temperatures by >20 K to lower values determined for N-C16-Dl-serine. The formation of the corresponding methylester decreases these temperatures by 15 K for serine with the shorter (C16) alkyl chain and only by ∼5 K for threonine with the longer chain (C18). The π-A curves of the enantiomeric and racemic allo-forms show similar features to those of N-stearoyl-threonine. The absolute T0-values (disappearance of the LE/LC-transition) are 4-5 K larger compared with the ...

Source: Advances in Colloid and Interface Science - October 20, 2023 Category: Chemistry Authors: D Vollhardt G Brezesinski R Rudert Source Type: research