體抑素中苯丙胺酸殘基對其螢光性質的影響

The role of phenylalanine residues in studying the fluorescence of somatostatin-14

范馥麟(Fu-Lin Fan)

指導教授 ： 錢偉鈞

朝陽科技大學/理工學院/應用化學系碩士在職專班/碩士(2011年)

摘要

體抑素(Somatostain)為14個胺基酸所組成的環狀胜?，具調節神經內分泌及新陳代謝之作用。原生體抑素從水溶液進入SDS微胞環境時，其螢光最高吸收波長(λmax)呈現藍位移現象且產生靜態消光。本實驗以丙胺酸取代體抑素序列中的苯丙胺酸，製備二段SRIF-14類似物 (SRIF-14 F6→A、F7→A)，並以圓二色光譜、核磁共振光譜及分子模擬探討體抑素類似物在不同環境下(水及SDS微胞溶液)螢光強度及胜?構型之間的關係。結果顯示體抑素類似物從水溶液進入SDS微胞環境時仍具螢光消光現象，但消光程度皆小於原生體抑素，其中以SRIF-14 F7→A最小。在胜?二級結構方面，構型皆以無序纏捲(random coil)為主並具有迴路(turn)之構型存在。相較取代第六位置苯丙胺酸，取代第七位置苯丙胺酸之類似物其構型特徵不明顯，尤其在活性部位之區域性結構較為鬆散，顯示第七位置苯丙胺酸的存在對構型區域性結構的穩定度極為重要，故區域性結構愈穩定者其螢光消光程度愈明顯。此外，取代不同位置苯丙胺酸之類似物並不影響與SDS微胞結合之物理性質。

關鍵字

苯丙胺酸 ； 活性片段 ； 區域性結構

並列摘要

Somatostatin (SRIF-14) is a cyclic tetradecapeptide that that is involved in the regulation of neuroendocrine and metabolic functions. When somatostatin moves into micellar environment from aqueous solution blue shift and quench of the fluorescence intensity can be observed in the fluorescence spectra. In this work two alanine substituted somatostatin analogues(SRIF-14 F6→A、F7→A)are prepared. Upon interacting with SDS micelle, all the analogues as well as native SRIF share similar behavior in the quench of fluorescence intensity, however, the SRIF-14 F7→A degree of quench of fluorescence intensity are less than the native SRIF and the SRIF-14 F6→A. The conformational change for peptides moving from aqueous solution into micellar environment was monitored by circular dichroism, nuclear magnetic resonance and molecular simulation spectroscopy and compared to the results of native peptide. Two somatostatin analogues are mainly in the equilibrium between random coil and a β-turn under aqueous and micellar environments. However, an Ala substituent at the position of the seventh residue in SRIF-14(SRIF-14 F7→A) do not have distinct regional structure, especially active site. For this reason, the more regional structure is distinctness, the stronger degree of quench of fluorescence intensity. Hence the 7th phenylalanine in the somatostatin plays an important role in stability regional structure. In addition, all somatostatin analogue are not change that the binding constants between the peptide and the micelles.

並列關鍵字

phenylalanine ； active site ； regional structure

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