title: Study of ethanol-lysozyme interactions using neutron diffraction.
abstract: Single-crystal neutron diffraction has been used to observe the interactions between deuterated ethanol (CD3CD2OH) and lysozyme in triclinic crystals of hen egg white lysozyme soaked in 25% (v/v) ethanol solutions. A total of 6047 observed reflections to a resolution of 2 A were used, and 13 possible ethanol sites were identified. The three highest occupied sites are close to locations for bromoethanol found in an earlier study by Yonath et al. [Yonath, A., Podjarny, A., Honig, B., Traub, W., Sielecki, A., Herzberg, O., & Moult, J. (1978) Biophys. Struct. Mech. 4, 27-36]. Structure refinements including a model for the flat solvent lead to a final crystallographic agreement factor of 0.097. Comparison with earlier neutron studies on triclinic lysozyme showed that neither the molecular structure nor the thermal motions were affected significantly by the ethanol. A detailed analysis of the ethanol-lysozyme contacts showed 61% of these to be with hydrophobic sites, in agreement with the dominant hydrophobic nature of ethanol. This, together with the fact that the molecular structure of lysozyme is not perturbed, suggests a model for denaturation of lysozyme by alcohol, which proceeds via a dehydration of the protein at high alcohol concentration.
mesh_terms: D000818:Animals; D002645:Chickens; D004529:Egg White; D000431:Ethanol / Q000378:metabolism*; D008958:Models, Molecular; D009113:Muramidase / Q000378:metabolism*; D009502:Neutrons; D011485:Protein Binding; D011487:Protein Conformation; D013057:Spectrum Analysis
chemical_list: D000431:Ethanol; D009113:Muramidase