Solvent and metal ion effects on the conformation of cyclosporin

R. A. Shaw; Henry H. Mantsch; Babur Z. Chowdhry

doi:10.1117/12.166699

31 January 1994 Solvent and metal ion effects on the conformation of cyclosporin

R. A. Shaw, Henry H. Mantsch, Babur Z. Chowdhry

Proceedings Volume 2089, 9th International Conference on Fourier Transform Spectroscopy; (1994) https://doi.org/10.1117/12.166699
Event: Fourier Transform Spectroscopy: Ninth International Conference, 1993, Calgary, Canada

Abstract

Infrared spectra of cyclosporin A (CsA) and three analogues CsC, CsD, and CsH have been measured (1) in a variety of organic solvents, and (2) in acetonitrile in the presence of lithium, sodium, magnesium, and calcium ions. The amide I (CequalsO stretching) absorption pattern shows a systematic trend with increasing solvent polarity. The spectral changes indicate that polar solvents disrupt two of the four intramolecular hydrogen bonds, leaving the first two hydrogen bonds of the (beta) -sheet structure intact. Interaction of CsA, CsC, or CsD with the monovalent cations Li⁺ and Na⁺ in acetonitrile yields spectra that are virtually identical to one another. The spectra suggest that several carbonyl groups bind simultaneously to the metal ion. In contrast the spectra suggest strong binding by Ca²⁺ and Mg²⁺ to one or two specific CequalsO groups, as evidenced by very low frequency CequalsO stretching bands observed at ca. 1600 cm^-1.

Citation Download Citation

R. A. Shaw, Henry H. Mantsch, and Babur Z. Chowdhry "Solvent and metal ion effects on the conformation of cyclosporin", Proc. SPIE 2089, 9th International Conference on Fourier Transform Spectroscopy, (31 January 1994); https://doi.org/10.1117/12.166699

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