The thermodynamic parameters of the stabilization of the native structure C(H)2 domains of human myeloma immunoglobulin LOM and SIN second subclass and their firstly obtained hFc fragments were determined using the methods of scanning microcalorimenry. A decrease in the termal stability and energy stability of the native of these domains in the intact proteins correlated in the "phisiological" range of temperatures (20-37 degrees C), mainly, with entropy factor.