[The concept of the "accessible surface" of the protein within the framework of tritium planigraphy. Experiment and calculation].

Tritium planigraphy allows one to determine the sterical accessibility of protein hydrocarbon fragments (CH, CH2, CH3 groups) for interaction with tritium atoms on condition of direct transit of the bombarding particles. Using lysozyme as a test system, it was shown to be possible to use these data for the description of protein accessible surface area in terms defined by Lee and Richards. The best agreement between experimental and theoretical results was achieved for an effective radius of the testing probe of 0.9 A. Coefficients were obtained that allowed calculation of the accessibility of amino acid residue as a whole using data about its hydrocarbon fragment accessibility.