Показано, что взаимодействие NA с Phe сопровождается комплексообразованием. <...> Молекулы NA в водном буферном растворе проявляют структуроразрушительные свойства, тогда как этот эффект уменьшается в буферном растворе с аминокислотой вследствие взаимодействия NA с молекулами Phe в процессе образования молекулярного комплекса между ними. <...> Ключевые слова: плотность, теплоемкость, кажущиеся мольные объемы и теплоемкости, L-фенилаланин, никотиновая кислота, образование комплекса Izv. <...> N 4 UDC: 547.466:544.032 INTERACTION OF NICOTINIC ACID WITH L-PHENYLALANINE IN BUFFER SOLUTIONS: HEAT CAPACITY AND VOLUME PROPERTIES STUDY E.Yu. <...> Tyunina *, Valentin G. Badelin Laboratory Thermodynamics of Non-Electrolyte Solutions and Active Substances, G.A. Krestov Institute of Solution Chemistry of RAS, Akademicheskaya st., 1, Ivanovo, 153045, Russia E-mail: tey@isc-ras.ru *, vgb@isc-ras.ru Valentina S. Egorkina Department of Fundamental and Applied Chemistry, Ivanovo State University of Chemistry and Technology, Ivanovo, Sheremetievskiy ave., 10, Ivanovo, 153000, Russia E-mail: valentina-egorkina@mail.ru Thermodynamic and physicochemical properties of multicomponent aqueous solutions containing biologically active solutes are important in various areas of applied chemistry and are essential for understanding the chemistry of biological systems. <...> Interactions between nicotinic acid (NA) and L-phenylalanine (Phe) were studied in aqueous phosphate buffer solutions (pH=7.35) by differential scanning calorimetry and volume methods. <...> Heat capacities and densities of nicotinic acid-buffer, L-phenylalanine-buffer, and nicotinic acid-L-phenylalanine-buffer mixtures were determined at T=(288.15, 298.15, 308.15 and 318.15) K using the microdifferential scanning calorimeter SCAL-1 (Pushchino, Russia) and the density meter DSA 5000 M (Anton Paar). <...> The apparent molar heat capacities ( Cp) and apparent molar volumes (Vφ,NA) of nicotinic acid in buffer solution and in buffer 0.0120 mol kg-1 amino acid solutions were evaluated. <...> The first and second differentials values were determined for NA in an aqueous buffer solution and for NA in an aqueous amino acid buffer solution. <...> The interaction of NA with Phe is accompanied by complex formation. <...> NA molecules in an aqueous buffer solution are water structure breakers, then the structure breaking effects of NA decrease as a result of interactions with Phe molecules <...>