Sie befinden Sich nicht im Netzwerk der Universität Paderborn. Der Zugriff auf elektronische Ressourcen ist gegebenenfalls nur via VPN oder Shibboleth (DFN-AAI) möglich. mehr Informationen...
Ionic Binding of Na+ versus K+ to the Carboxylic Acid Headgroup of Palmitic Acid Monolayers Studied by Vibrational Sum Frequency Generation Spectroscopy
Ist Teil von
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory, 2009-07, Vol.113 (26), p.7383-7393
Ort / Verlag
United States: American Chemical Society
Erscheinungsjahr
2009
Link zum Volltext
Quelle
MEDLINE
Beschreibungen/Notizen
Ionic binding of alkali ions Na+ and K+ to the carboxylic acid headgroups of fatty acid monolayers is studied as a proxy toward understanding the fundamental chemistry in cell biology. In this study, we used broad-bandwidth sum frequency generation (BBSFG) vibrational spectroscopy to investigate the ionic binding event that leads to deprotonation and complex formation of fatty acid headgroups. Palmitic acid (C15H31COOH) exists as a monolayer on aqueous surfaces. Surface vibrational stretch modes of palmitic acid from 1400 cm−1 to 3700 cm−1 were observed (νs-COO−, ν-CO, ν-CH, ν-OH of COOH, free OH). Palmitic acid is mostly protonated at the aqueous surface at neutral pH (∼6). However, various degrees of deprotonation are initiated by the introduction of Na+ and K+ that results in the complexation of K+:COO− and solvent separated Na+:COO−. Evidence in several spectral regions indicates that K+ exhibits stronger ionic binding affinity to the carboxylate anion relative to Na+.