Conformational analysis of 6-cis- and 6-trans-leukotriene B4-calcium complexes.

We present a computational description of the conformation of a pair of two isomeric molecules (6-cis-and 6-trans-leukotriene B4) forming a complex with one calcium ion. Our theoretical prediction of the membrane-water interface conformation and of the bulk lipid phase conformation of the two different isomeric complexes are in excellent agreement with experimental data on the leukotriene-mediated calcium ionophoresis in liposomes. The two isomers lead to vastly different conformations in the presence of Ca2+, and the most probable conformation of the permeant species shows a globular conformation able to cross a lipid membrane.