I used DSC to measure the denaturation temperature of proteins, but the repeatability is very poor, sometimes there are peaks, sometimes not. Btw, I used protein solution for measurement (10% wt). Does anyone know why?
Thanks a lot
DSC measurement deals with the thermodynamic change of the system. If the sample goes across the thermodynamic phase transitions you can see the exothermic/endothermic peak. Sometimes peak presence means there is a phase change, the absence of the peak is the system does not go through any thermodynamic phase transition. In the case of solid-state materials (mostly inorganic systems) thermodynamic phase transitions are associated with the structural phase transitions. In your case, you are dealing with protein, that means solutions composition is changing its stability. I would recommend characterizing the same sample before and after DSC with UV/PL characterizations to get more insight. Additionally, protein stability is highly determined by the temperature you are dealing it. If you go beyond a certain temperature, it may decompose. So becareful.
Dear Xingfa Ma, you have too high concentration in your experiment. For reproducible results, the protein concentration should be 10 mg/ml. At 100 mg/ml, the protein aggregation occurs, which is a non-equilibrium process and may have a random influence on the protein denaturation parameters.
Dear Xingfa Ma, detalled analysis procedure is presented in the following document. My Regards
https://link.springer.com/protocol/10.1007%2F978-1-4939-9678-0_9
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