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The Leu 5 gramicidin a analog: Molecular mechanics calculations and analysis of single channel steps related to multiplicity of conducting states
Author(s) -
Venkatachalam C. M.,
AlonsoRomanowski S.,
Prasad K. U.,
Urry D. W.
Publication year - 1984
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560260733
Subject(s) - multiplicity (mathematics) , molecular mechanics , gramicidin s , gramicidin , statistical mechanics , physics , chemistry , molecular dynamics , statistical physics , computational chemistry , mathematics , membrane , mathematical analysis , biochemistry
Single‐channel studies have shown that there exist a multiplicity of conducting states in Gramicidin A (GA). In an earlier work presented at this symposium, it was proposed that such a multiplicity may be expected from different long‐lived side‐chain distributions available for the channel molecule. In order to test this hypothesis, Leu 5 –Gramicidin A was synthesized and the effect of replacing the L · Ala 5 residue by L · Leu 5 was analyzed. First, molecular mechanics calculations on Leu 5 –Gramicidin A are presented. Then the single‐channel conductance sweeps obtained for Leu 5 ‐GA are automatically analyzed in the computer using specifically developed algorithms. The results show a dramatic decrease in the multiplicity of states due to the Leu 5 substitution. This experimental result is discussed in the light of structural concepts emerging from molecular mechanics calculations.