巨分子在細胞內佔總體積大約百分之三十，造成一個非常擁擠的環境，使蛋白質摺疊並表現其功能，稱為擁擠效應。
泛素(ubiquitin)屬於小型蛋白質，是由76個胺基酸組成，野生種泛素結構表現為一個α螺旋和四個β摺疊，野生種的泛素結構在pH範圍從2到10之間皆呈現摺疊狀態，並且僅在高濃度變性劑時才會解構，結構穩定度很高。
本實驗室之前的研究發現，泛素突變株包括F4A、V26A、I30A結構的穩定度都比野生種差，其結構在酸性環境下會同時出現摺疊狀態和解構狀態兩者共存的現象，而且酸性越高，解構狀態比例越高，但通過擁擠環境可以使原本的結構由解構狀態轉向摺疊狀態。
在本篇論文中，我們使用圓二色光譜儀和核磁共振光譜儀來觀察泛素及泛素的突變種的結構，並觀察在葡聚醣(dextran)的擁擠環境下結構的變化及穩定度的變化。

第一章 文獻討論 1
第二章 實驗材料與方法 3
第三章 實驗結果 7
第四章 結論 10

1.Ellis, R. J. (2001) Macromolecular crowding: obvious but underappreciated. Trends in Biochemical Sciences 26, 597-604
2.Goto, Y., Takahashi, N., and Fink, A. L. (1990) Mechanism of acid-induced folding of proteins. Biochemistry 29, 3480-3488
3.van den Berg, B., Wain, R., Dobson, C. M., and Ellis, R. J. (2000) Macromolecular crowding perturbs protein refolding kinetics: implications for folding inside the cell. EMBO J 19, 3870-3875
4.Sasahara, K., McPhie, P., and Minton, A. P. (2003) Effect of Dextran on Protein Stability and Conformation Attributed to Macromolecular Crowding. Journal of Molecular Biology 326, 1227-1237
5.Tokuriki, N., Kinjo, M., Negi, S., Hoshino, M., Goto, Y., Urabe, I., and Yomo, T. (2004) Protein folding by the effects of macromolecular crowding. Protein Sci 13, 125-133
6.Spencer, D. S., Xu, K., Logan, T. M., and Zhou, H. X. (2005) Effects of pH, salt, and macromolecular crowding on the stability of FK506-binding protein: an integrated experimental and theoretical study. J Mol Biol 351, 219-232
7.Selenko, P., Serber, Z., Gadea, B., Ruderman, J., and Wagner, G. (2006) Quantitative NMR analysis of the protein G B1 domain in Xenopus laevis egg extracts and intact oocytes. Proc Natl Acad Sci U S A 103, 11904-11909
8.Ai, X., Zhou, Z., Bai, Y., and Choy, W. Y. (2006) 15N NMR spin relaxation dispersion study of the molecular crowding effects on protein folding under native conditions. Journal of the American Chemical Society 128, 3916-3917
9.Wang, Y., Sarkar, M., Smith, A. E., Krois, A. S., and Pielak, G. J. (2012) Macromolecular crowding and protein stability. Journal of the American Chemical Society 134, 16614-16618
10.鍾澤裕. (2007) 生物巨分子擁擠效應對蛋白質結構及穩定度之影響. 碩士, 國立東華大學
11.沈聖宗. (2010) 擁擠試劑以及鹽類對泛素突變株結構及穩定度之影響. 碩士, 國立東華大學
12.藍健銘. (2017) 鹽類和擁擠試劑對泛素突變株V26A/I30A的結構和穩定度的影響. 碩士, 國立東華大學
13.Guntert, P. (2004) Automated NMR structure calculation with CYANA. Methods in molecular biology (Clifton, N.J.) 278, 353-378
14.Vijay-Kumar, S., Bugg, C. E., and Cook, W. J. (1987) Structure of ubiquitin refined at 1.8 A resolution. J Mol Biol 194, 531-544
15.Shen, Y., Delaglio, F., Cornilescu, G., and Bax, A. (2009) TALOS+: a hybrid method for predicting protein backbone torsion angles from NMR chemical shifts. Journal of biomolecular NMR 44, 213-223
16.Sreerama, N., and Woody, R. W. (2004) On the analysis of membrane protein circular dichroism spectra. Protein Sci 13, 100-112
17.Bohm, G., Muhr, R., and Jaenicke, R. (1992) Quantitative analysis of protein far UV circular dichroism spectra by neural networks. Protein engineering 5, 191-195