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Ion complexation in nonactin, monactin, and dinactin: A Raman spectroscopic study
Author(s) -
Asher Irvin M.,
Phillies George D. J.,
Kim B. J.,
Stanley H. E.
Publication year - 1977
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1977.360160112
Subject(s) - chemistry , raman spectroscopy , ion , ionic bonding , solid state , inorganic chemistry , stereochemistry , analytical chemistry (journal) , organic chemistry , physics , optics
The ability of the macrotetrolide nactins to complex selectivity with a wide variety of cations makes these ionophorous antibiotics important model systems for the study of biologic ionic transport. We report a Raman spectroscopic investigation of the Na + , K + , Rb + , Cs + , Tl + , NH 4 + , NH 3 OH + , C(NH 2 ) 3 + , and Ba ++ complexes of nonactin, monactin, and dinactin in 4:1 (v/v) CH 3 OH/CHCl 3 and in the solid state. The nactins display characteristic spectral changes upon complexation, some of which are specific for a given cation. In the K + , Rb + , Cs + , NH 3 OH + , and C(NH 2 ) 3 + complexes, which are apparently isosteric, the ester carbonyl stretch frequency is found to be linearly proportional to the cation–carbonyl electrostatic interaction energy, as calculated from a simplified model. Deviations for the Na + , NH 4 + , Tl + , and Ba ++ complexes are interpreted as arising from additional nonelectrostatic interactions. Additional information is obtained from other spectral regions and from measurements of depolarization ratios. Spectra of the nactin complexes differ from each other more in the solid state than in solution, reflecting the effects of crystalline contact forces.