Measurement and analysis of results obtained on biological substances with d.s.c. |
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| Affiliation: | 1. Chongqing Key Laboratory of Extraordinary Coordination Bonding and Advanced Materials Technology (EBEAM), Yangtze Normal University, Chongqing 108100, China;2. Institute of Coordination Bond Metrology and Engineering (CBME), College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, China;3. Key Laboratory of Low-Dimensional Materials and Application Technologies (Ministry of Education) and School of Materials, Science and Engineering, Xiangtan University, Hunan 411105, China;4. Institute of Nanosurface Science and Engineering, Shenzhen University, Shenzhen 518060, China;5. NOVITAS, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore;1. Institute of Coordination Bond Metrology and Engineering, College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, China;2. Key Laboratory of Low-Dimensional Materials and Application Technology (Ministry of Education) and School of Materials Science and Engineering, Xiangtan University, Hunan 411105, China;3. Institute of Nanosurface Science and Engineering, Shenzhen University, Shenzhen 518060, China;4. NOVITAS, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore |
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| Abstract: | The differential scanning calorimeter (d.s.c.) has been widely used to determine the thermodynamics of phase transitions and conformational changes in biological systems including proteins, nucleic acid sequences, and lipid assemblies. The d.s.c monitors the temperature difference between two vessels, one containing the biological solution and the other containing a reference solution, as a function of temperature at a given scan rate. Recommendations for d.s.c. measurement procedures, calibration procedures, and procedures for testing the performance of the d.s.c. are described. Analysis of the measurements should include a correction for the time response of the instrument and conversion of the power versus time curve to a heat capacity versus temperature plot. Thermodynamic transition models should only be applied to the analysis of the heat capacity curves if the model-derived transition temperatures and enthalpies are independent of the d.s.c. scan rate. Otherwise, kinetic models should be applied to the analysis of the data. Application of thermodynamic transition models involving two states, two states and dissociation, and three states to the heat capacity versus temperature data are described. To check the operating performance with standard d.s.c.s, samples of (1 to 10) mg · cm3solutions of hen egg white lysozyme in 0.1 mol · dm − 3HCl–glycine buffer at pH = (2.4 ± 0.1) were sent to six different d.s.c. laboratories worldwide. The values obtained from proper measurements and application of a two-state transition model yielded an average unfolding transition temperature for lysozyme of 331.2 K with values ranging between T = 329.4 K and 331.9 K, and an average transition enthalpy of 405 kJ · mol − 1with values ranging from 377 kJ · mol − 1to 439 kJ · mol − 1. It is recommended that the reporting of d.s.c. results be specific with regard to the composition of the solution, the operating conditions and calibrations of the d.s.c. determination of base lines that may be model dependent, and the model used in the analysis of the data. |
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