Berlin 2018 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 24: Bioinspired Functional Materials, Biomaterials and Biopolymers (joint session CPP/BP)
BP 24.3: Vortrag
Mittwoch, 14. März 2018, 15:30–15:45, PC 203
Direct Determination of the Thermodynamic Properties of Melting for Amino Acids — •Y.Z. Chua1, A. Abdelaziz1,2, D. Zaitsau2, S. Verevkin2, C. Held3, and C. Schick1 — 1Uni Rostock, Institut für Physik and Competence Centre CALOR, Rostock — 2Uni Rostock, Institut für Chemie, Rostock — 3TU Dortmund, Department of Biochemical and Chemical Engineering, Dortmund
The properties of melting are used for the prediction of solubility of solid compounds. By using conventional DSC or adiabatic calorimetry, direct determination of the melting temperature, Tfus, and enthalpy of fusion, ΔfusH, is often not possible for biological compounds due to the decomposition during the measurement. The apparent activation energy of decomposition is at least one order of magnitude smaller than that of melting. This allows shifting of the decomposition process to higher temperature without seriously disturbing the melting by applying very high heating rates. High scanning rates up to 2·104 K·s−1 are utilized with fast-scanning calorimeter Mettler Toledo Flash DSC1. The melting parameters, e.g. Tfus and ΔfusH, for L-threonine and glycine were successfully determined. The ultra-fast cooling of the melted samples allows the studied compounds to retain in the liquid state and to determine for the first time its glass transition temperatures, Tg, which agree with the Beaman-Kauzmann rule (Tg ≈ 2/3· Tfus). The entropy of fusion shows significant deviation between the two amino acids. For L-threonine, it was close to the Walden’s rule, while for glycine, it was twice smaller. The results are in reasonable agreement with the simulated PC-SAFT values.