[Effect of temperature and degree of hydration on the mobility of spin labels in surface layers of proteins].
The mobility of separate sites of the water-protein matrix depending on temperature and degree of hydration has been investigated by means of spin labels covalently attached to surface layers of proteins (alpha-chymotrypsin and human serum albumin) and also by a spin probe in a hydrophobic "pocket" of human serum albumin. The results obtained are compared with the data on the mobility of gamma-resonance labels (57Fe) firmly bound with the protein matrix in the same samples. At certain temperature and degree of hydration both spin and gamma-resonance label show an increase in mobility. With the degree of hydration increasing one may observe a simultaneous increase in energy and in entropy of activation: rotatory diffusion of spin labels, i. e., a compensation effect takes place which confirms the concept expressed earlier that cooperation of water-protein interactions is the main reason of CEF. It should be noted that at P/PS greater than 0.8 the values of delta E =7 divided by 10 kcal/mole, and delta S not equal to = 9 divided by 11 e. e. are specific to glycerol-like systems, i. e., under these conditions (P/Ps greater than 0.8) the water-protein layer has glycerol-like properties.
D002151:Calorimetry; D002918:Chymotrypsin; D006860:Hydrogen Bonding; D007700:Kinetics; D011485:Protein Binding; D012710:Serum Albumin, Bovine; D013113:Spin Labels; D013696:Temperature
D013113:Spin Labels; D012710:Serum Albumin, Bovine; D002918:Chymotrypsin
Vliianie temperatury i stepeni gidratatsii na podvizhnost' spinovykh metok v poverkhnostnykh sloiakh belkov.