8-烷基小檗碱同系物对蛋白荧光的淬灭作用与其抗菌活性的关系

Relationship of fluorescence quenching effect of 8-alkyl-berberine homologues on bovine serum albumins and their antimicrobial activities

目的:了解8-烷基小檗碱同系物(Ber-C8-n)对蛋白荧光的淬灭作用与其抗菌活性的关系,探讨Ber-C8-n抗菌活性变化的机制.方法:以牛血清白蛋白(BSA)为实验材料,等渗磷酸缓冲液(PBS)为溶剂,分别将每种Ber-C8-n用PBS溶液配制不同浓度的梯度溶液,测定BSA与不同浓度Ber-C8-n在PBS体系中反应后苯丙氨酸(Phe),色氨酸(Trp)和酪氨酸(Tyr)残基的荧光强度,观察Ber-C8-n对BSA残基荧光的淬灭情况.结果:Ber-C8-n对BSA中3种氨基酸残基的荧光均有不同程度的淬灭作用,并均有明显的剂量效应.比较后发现,Ber-C8-n对BSA中Phe,Trp和Tyr残基荧光的淬灭作用表现出相似规律,即Ber-C8-8同样表现了最强的荧光淬灭作用,其次为烷基链较长或较短的Ber-C8-n,基本上呈现以Ber-C8-8顶点的抛物线.3种残基之间比较,Ber-C8-8对Trp残基荧光的淬灭作用明显强于对Tyr和Phe残基的作用.结论:抗菌活性越强的Ber-C8-n对BSA荧光的淬灭作用也越强,Ber-C8-n抗菌活性的差异可能是不同Ber-C8-n与目标蛋白的富Trp残基区的结合能力差异导致的.

AIM：To investigate the relationship of antimicrobial activity and fluorescence quenching effect of 8-alkyl-berberine homologues（Ber-C8-n）including berberine,8-ethyl-berberine,8-butyl-berberine,8-hexyl-berberine,8-octyl-berberine,8-decyl-berberine,8-dodecyl-berberine and 8-cetyl-berberine on protein and the changing mechanism of antimicrobial activity. METHODS：With bovine serum albumins（BSA） as experimental material and phosphate buffered saline（PBS） as reacting solvent,the fluorescence intensity of Tryptophan （ Trp ） , Tyrosine （Tyr） and Phenylalanine（Phe） residues in BSA were determined after BSA reacted with Ber-C8-n of different concentration in PBS system. RESULTS： The fluorescence quenching effects of all Ber-C8-n on BSA were observed, which exhibited obvious dose- effect relationship. The parabolic law of fluorescence quenching effects of Ber-C8-n on Trp, Tyr and Phe residues in BSA was also find out, which was the same as the parabolic law of antimicrobial activity of Ber-C8-n. For example, the 8-octyl-berberine having highest antimicrohial activity among Ber-C8-n showed strongest fluorescence quenching ability on BSA, and too short or too long substituted alkyl chain at C8 position of berberine decreased their fluorescence quenching ability and antimicrobial activity. Besides, the fluorescence quenching effect of Ber-C8-n on Trp residue far higher than on Tyr and Phe residues of BSA. CONCLUSION： Results indicated the antimicrobial activity of Ber-C8-n is higher, the fluorescence quenching ability is stronger, and antimicrobial activities of Ber-C8-n were related to their ability of combining with rich Trop resides region of target protein.