[The surface layer of the protein globule. Hydration of the alpha-chymotrypsin molecule]

The surface of the alpha-chymotrypsin globule is investigated using a three-dimensional model of the molecule, constructed on the basis of X-ray data by sectioning the space of the protein globule in cubic elements with a step of 3 A. The surface layer contains about 55% of the overall globule volume. The atomic density of so defined surface was found to be approximately equal to that in the inner part of the globule. Topographical maps of the alpha-chymotrypsin surface were drawn and an analysis of the distribution of polar and unpolar atoms and groups on the surface and in the inner part of the globule was carried out. Some conclusions drawn from the atomic density, energetic and structural heterogeneity of the surface and concerning the conformational integrity and functional activity of alpha-chymotrypsin molecule are presented. Some aspects of the protein hydration problem are discussed and a structural model of the alpha-chymotrypsin hydratation shell is proposed, the main features of which are amorphism and the lack of long-range effect on the structure of water around the hydrated protein globule.