DIFFERENTIAL ISOTHERMAL ROTATING MICROCALORIMETER - REALIZATION AND EVALUATION - APPLICATION TO THE STUDY OF THE INTERACTION BETWEEN HUMAN GROWTH-HORMONE AND COSOLVENTS

In order to study interactions in biological sytems, a differential is othermal rotating microcalorimeter has been developed. The small react ion volume (<1 ml) and the high sensitivity of the system (0.5 muW) al lows the study of dilute solutions (2-20 mg ml-1) of proteins that are difficult to obtain. A study of the interaction between biosynthetic growth hormone (hGH) and different molecules (alanine, glycerol, benzy lic alcohol and chlorocresol) was carried out. The interaction enthalp y rose to 10 kJ mol-1 for alanine and glycerol, to 26.5 kJ mol-1 for b enzylic alcohol and 51.5 kJ mol-1 for chlorocresol, with which protein denaturation is instantaneous. A comparison of these results with tho se obtained by differential scanning calorimetry (DSC) was made, showi ng the complementarity of both techniques.