MODELING CHEMOADAPTIVE BEHAVIOR - X-RAY STRUCTURE OF THE TRIMETHYLAMINE OXIDE UREA (1-4) COMPLEX

The structure of a trimethylamine oxide (TMAO)-urea 1:4 complex was investigated by x-ray crystallographic methods. C3H9NO, 4CH4N2O, M(r) = 315.33, monoclinic P2(1)/n, a = 11.004(2), b = 9.8259, c = 15.419(2), beta = 106.88(4)-degrees, V = 1595.4(2) angstrom3, Z = 4, D(x) = 1.313(1) g cm-3, monochromatized Cu K(alpha) (lambda = 1.5418 angstrom), mu = 8.94 cm-1, F(000) = 680, temperature = 110-degrees-K, final R = 0.067, for 1786 unique observed reflections. Based on these studies and comparison with related compounds a model of the interaction of urea and TMAO with proteins, especially enzymes, is proposed. This is important in the physiology of many organisms, especially elasmobranchs. The counteracting effect of TMAO on urea perturbation of protein structure and function is interpreted in terms of water structure as a balance between the structure breaking effect of urea and the structure-stabilizing effect of TMAO.