利用13C弛緩動力學來討論不同自結合狀態下的螺旋摺疊：以NPY為模型胜肽

Main chain dynamics of peptides with different self-association states in aqueous TFE Using Natural Abundance 13C NMR Relaxation experiments: NPY fragments as the model peptides

劉士豪(Shih-Hao Liu)

指導教授 ： 李長欣

淡江大學/理學院/化學學系碩士班/碩士(2010年)

https://doi.org/10.6846/TKU.2010.00645

摘要

除了在非常低的濃度下，NPY在不同自結合的狀態之間保持著一些平衡，這個結合狀態過程受到pH值，溫度和溶劑等等來自於分子間作用力的影響，它可能也暗示著當與細胞膜的結合時，單體NPY重要的活性結構摺疊的過程，因此，也表示著在那些不同低聚物之間的平衡和那些在分子之間主要的相互作用。為了更近一步了解在不同自結合狀態下的螺旋摺疊，我們利用hNPY片段[21-31]、[20-36]在285K與310K下的13C弛緩動力學來討論不同自結合狀態下螺旋折疊的變化。當溫度從310K下降到283K時，hNPY[21-31]的實驗分子量會明顯的從1.2增加到單體的4倍，而hNPY[20-36]則是維持著單體的2倍且無太大變化。這個聚合狀態變化可由弛緩實驗導出的整體關聯時間(21-31: 0.53 ns→1.97 ns、20-36: 1.39→3.17)明顯的觀察到。另外，從model-free導出的參數(S2、τe、Rex)更深入的了解內部殘基的運動情況。結構之間的差異，動力學應可清楚指出在結合狀態下構型的變化。藉由合成這兩段短胜肽，我們能成功了解NPY螺旋摺疊及各個殘基的動力學行為。

關鍵字

神經胜肽 ； 圓二色光譜 ； 核磁共振 ； 自結合 ； 弛緩 ； 動力學 ； 無模型法則

並列摘要

Except at very low concentrations, NPY is in equilibrium between different states of self-associate. The associate process has a complex dependence on pH, temperature and solvent etc. due to intermolecular forces. It may also imply the fundamental process of monomeric NPY induced folding to an active conformation as binding to cellular membrane. Accordingly, it’s important to elucidate the equilibrium between different oligomeric states and the essential interaction between molecules. For further probing helix folding with different self-association states, we performed natural abundance 13C relaxation dynamics with hNPY fragments (from residue 21 to 31 and 20 to 36) at 285K and 310K. As the temperature decrease from 310 to 285K, the apparent molecular weight of hNPY[21-31] is increased from 1.2 to 4 times of monomeric molecular mass and hNPY[20-36] keep 2 times of monomeric mass in theory. The changes in aggregation state is furthermore evident by overall correlation time (21-31: 0.53ns→1.97ns, 20-36: 1.39ns→3.17ns) derived from relaxation measurements. In addition, parameters (S2, τe, Rex) that exported by model-free could get more insight into internal motions of each residues. The differences between structures, dynamics should clearly point to the direction of the conformational changes during associate process. With this synthesized short peptides we could successfully probe the helix folding and dynamic behavior for each residues.

並列關鍵字

NPY ； CD, NMR ； self-association ； Relaxation ； dynamic ； Model-Free

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