Studies on the Thermal Denaturation of BSA by Optical Rotation Measurement

• Main Authors: Chen, Hsin-yue, 陳欣樂
• Other Authors: Wu, Chien-Ming
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/89226804832793341536

碩士 === 國立清華大學 === 生醫工程與環境科學系 === 97 === The secondary structure (α-helix, β-sheet, random coil) of proteins may denature by the changes of pH, solvent or temperature. For example, an α-helix changes to a random coil. The transformation of denaturation is not well understood now. There are many methods to detect the structures of protein, such as X-ray diffraction crystallography, differential scanning calorimetry, circular dichroism spectroscopy, and optical rotation dispersion, however, it is not easy to monitor the denaturation process of proteins because it may be fast. So it is important to build a real-time detection system. X-ray diffraction crystallography can be used to observe only dry protein crystallization or powder, so it can’t observe the structure of protein dissolving in water. Circular dichroism spectroscopy is usually used to calculate the proportion of different secondary structure of proteins, however, it’s not a real-time system because the spectrum needs to be scaned. In our experiment, we utilize a variable-retarder to enhance the optical rotation and combine the lock-in detection technique. Therefore, we have constructed a real-time detection system with amplification value of 12.8. The purpose of this paper is to demonstrate our system which can be used to monitor the structure of proteins by optical rotation changes. High-temperture can cause denaturation of proteins, which then result in the changes of optical activity. In this experiment, we used BSA as our sample and measured the optical rotation signal while heating BSA. The result indicates that the optical rotation of 1 % BSA is decreased while heating from 45℃ to 70℃. In contrary, the optical rotation of 2.5 % and 5 % BSA are increased in the same condition.