中文摘要
阿茲海默症是神經退化性疾病的一種主要疾病，其主要的病理特徵是神經細胞內纖維化糾結以及腦細胞外老年斑塊，而貝它類澱粉蛋白的聚集則是造成老年斑塊的主要原因。儘管貝它類澱粉蛋白已經被廣泛的研究，但其沉積聚集的機制尚未清楚。本次實驗旨在探討膠原蛋白序列對貝它類澱粉蛋白的抑制效果，並分析貝它類澱粉片段序列蛋白對膠原蛋白三股螺旋結構穩定性、摺疊速率的影響。
本研究中，我們選擇貝它類澱粉蛋白中最重要的一段胺基酸序列 A(16-12) ( KLVFFAE) 來做研究，合成一系列接上膠原蛋白相關序列 (POG)n 之 A 相關胜肽鏈共八段: 未接上膠原蛋白序列 (WT-A (16-22))，在碳端的位置接上六個POG( A(POG)6 )、七個 POG ( A(POG)7 ) 、十個 POG ( A(POG)10 )，在氮端位置接上七個 POG ( (POG)7A ) 、十個 POG ( (POG)10A ) 及單純的膠原蛋白 (POG)7、(POG)10。利用螢光光譜儀、TEM、CD、DLS以及 FT-IR來探討這些胜肽鏈是否對 A 沉積具有抑制的效果。
經由 CD 測量發現 A(16-22) 位於胜肽鏈之 N 端時會妨礙膠原蛋白三股螺旋結構的摺疊，使熱穩定性降低；但 A(16-22) 位於胜肽鏈之 C 端時則會幫助三股螺旋結構的摺疊使熱穩定性上升。從觀察 A 聚集現象我們發現無論在 A (16-22) 的 C 端或 N 端接上七個 POG 都不會有聚集現象的產生，但接上十個 POG 後反而會加強聚集現象，因此我們知道 POG 的數目不宜過多才會有較好的抑制效果，最後將 POG 數目較少的三條胜肽: A(POG)6、 A(POG)7、(POG)7A 與 WT-A (16-22) 相混發現 (POG)7A 並無抑制的效果，而 A(POG)6、 A(POG)7 有抑制 A 聚集產生的效果，而這個效果並不完全來自於膠原蛋白的三股螺旋結構而可能與 PPⅡ 結構有關係。

Abstract
Alzheimer's disease ( AD ) is one of the most fatal neurodegenerative disease .The
major pathogenesis of Alzheimer's disease ( AD ) is neurofibrillary tangles and enile plaques , and the aggregation of the A 40 plays a crucial role in the pathogenesis of the senile plaques of Alzheimer's disease (AD) . Although the amyloid -protein has been studied extensively , the mechanisms of A aggregation in brain remain unclear . In this study , we investigate the influence of the collagen related peptides on A aggregation.
Here we chose the most important region of amyloid -protein responsible for aggregation , residues 16-22 (KLVFFAE) , as our study model . We incorporated the collagen sequence (POG)n into Aβ(16-22) and synthesized eight peptides:
WT-A(16-22) , A(16-22)-(POG)6 , A(16-22)-(POG)7, A(16-22)-(POG)10 , (POG)7-A(16-22) and (POG)10-A(16-22).Two collagen peptides (POG)7 and (POG)10 were synthesized as the control peptides for comparison.We used fluorescence spectroscopy, TEM , CD , FT-IR and DLS to study whether the collagen sequence can inhibit A aggregation .
CD measurements indicate that the Aβ(16-22) sequence at the N-terminus of (POG)n does not stabilize the triple-helical structure of collagen and such peptides have a weaker thermal stability than (POG)n .In contrast,when the Aβ(16-22) sequence is attached to the C-terminus of (POG)n, it can stablize the triple-helical structure of collagen.
From aggregation studies, we found that the amyloid aggregation did not occur when (POG)7 was incorporated into A(16-22) but the aggregation was enhanced when (POG)10 incorporated into A(16-22).The mixing experiments indicate that (POG)7A cannot inhibit the aggregation of WT-A(16-22) while A(POG)6 and A(POG)7 can.The inhibition effect may not be due to the triple-helical structure of collagen but the PPⅡ structure.

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