Study on the Interaction of Nicotinic Acid with l-Phenylalanine in Buffer Solution by Heat Capacity Measurements at Various Temperatures

• Published in: Journal of solution chemistry 2017-02, Vol.46 (2), p.249-258
• Main Authors: Tyunina, E. Yu, Badelin, V. G., Mezhevoi, I. N.
• Format: Article
• Language: English
• Subjects: Amino acids; Buffer solutions; Chemistry; Chemistry and Materials Science; Complex formation; Condensed Matter Physics; Geochemistry; Industrial Chemistry/Chemical Engineering; Inorganic Chemistry; Nicotinic acid; Oceanography; Phenylalanine; Physical Chemistry; Specific heat
• ISSN: 0095-9782; 1572-8927
• DOI: 10.1007/s10953-017-0570-6

The interaction between nicotinic acid (NA) and l -phenylalanine (Phe) was studied in aqueous phosphate buffer solutions (pH = 7.35) by differential scanning calorimetry. Heat capacities of nicotinic acid–buffer, l -phenylalanine–buffer, and nicotinic acid– l -phenylalanine–buffer mixtures were determined at (283.15, 288.15, 293.15, 298.15, 303.15, 308.15, 313.15, 318.15 and 323.15) K using the microdifferential scanning calorimeter SCAL-1 (Pushchino, Russia). The apparent molar heat capacities, ϕ C p , of nicotinic acid in buffer solution and in buffer 0.0216 mol·kg −1 amino acid solutions were evaluated. The concentration of NA was varied from (0.0106–0.0701) mol·kg −1 . The interaction of NA with Phe is accompanied by complex formation. The partial molar heat capacities of transfer of nicotinic acid from buffer to buffer amino acid solutions are positive. The results are discussed in terms of various interactions operating in this system.