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Conformational difference in cation complexes of tetranactin in solution
Author(s) -
Ueno Masaharu,
Kyogoku Yoshimasa
Publication year - 1979
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.1979.360181102
Subject(s) - chemistry , tetrahydrofuran , alkali metal , raman spectroscopy , cryptand , rubidium , methylene , ion , ammonium , inorganic chemistry , ring (chemistry) , crystallography , photochemistry , potassium , medicinal chemistry , organic chemistry , physics , solvent , optics
The conformational changes and binding behavior of tetranactin on complexation with sodium, potassium, rubidium, cesium, and ammonium ions were investigated by the measurements of proton magnetic resonance, ir, and Raman spectra. It has been clearly shown that alkali cations coordinate to the oxygen atoms of both the carbonyl group and the tetra‐hydrofuran ring, but the ammonium ion coordinates only to the oxygen atom of the tetrahydrofuran. Among the alkali cations the potassium ion most strongly coordinates to the tetrahydrofuran oxygen atoms. The complexation with larger cations induces an expansion of the cavity of the macrocyclic ring of tetranactin and smaller cations contract the cavity. The evidence is revealed by the coupling constants of the methylene protons and the frequency separation between the carbonyl stretching vibrations of the ir‐ and Raman‐active modes. The conformations of the cation complexes in the solid are maintained in solution but that of the cation free form is not.