蛋白質的二級結構(α螺旋、β平板、隨機的圈)會因為酸鹼值、溶劑以及溫度的改變而破壞。例如α螺旋破壞變成了隨機的圈。變性過程的細節目前並沒有充分的被了解。目前有許多測量蛋白質構型的方法，諸如X-ray晶格繞射、差分掃描量熱法、圓的二色性光譜以及旋光色散法。但是因為蛋白質變性的過程通常很快速，因此造成量測的困難。所以需要一個好的即時性觀測系統。X-ray晶格繞射只能用來量測蛋白質晶體或是粉末，因此無法量測蛋白質溶液。而圓的二色性光譜通常用來計算蛋白質二級結構的比例，又因為光譜需要掃描，因此無法即時性的量測。
在本研究中，吾人結合鎖相放大器之技術，並使用相位可調式波片來放大旋光訊號。架設一個放大率為12.8之即時量測系統。本實驗之目的為證明此系統可以即時性量測蛋白質構型的變化。已知溫度會造成蛋白質的變性，並造成旋光角度的變化。在本實驗中，我們使用BSA做為參考試劑，在加溫的過程中同時量測旋光變化。而實驗結果顯示，1 % BSA由攝氏度45度加熱到攝氏度70度時，其旋光度趨勢是下降的；而相反的，2.5 % 及5 % BSA在相同的加熱條件下，其旋光度有上升的趨勢。

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.

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