ndolicidin有廣泛的抗生活性，可以用來對抗多種細菌、黴菌與病毒，但是少許的溶血活性限制了它的應用。本研究主要探討鹼性胜肽抗生素indolicidin (IL)造成溶血的原因，我們將其第8與第9位置的tryptophan(Trp)置換為phenylalanine而成為ILF89，測量IL與ILF89的抗生與溶血活性，並搭配tryptophan的螢光光譜探究IL及ILF89與膜之作用機制。在生物活性檢測上，發現ILF89不僅維持與IL相當的抗菌性，其溶血活性相較於IL有大幅降低，此證實W8與W9與胜肽的溶血性確實相關。而從IL及ILF89於水相的螢光光譜，發現在低濃度時，具有5個Trp的IL，其螢光強度卻低於僅有3個Trp的ILF89，因此推測IL可能會以寡聚體的形式存在而降低自身螢光。另外，我們也進一步探討胜肽與POPC (1-Palmitoyl-2-Oleoyl-sn- Glycero-3-Phosphocholine)或POPC/POPG (1-Palmitoyl-2-Oleoyl-sn- Glycero-3-[Phospho-rac-(1-glycerol)])微脂粒間的作用，發現IL與磷脂膜共存的系統，單位Trp的螢光值大幅提高，推測此為寡聚體的IL，於吸附於膜面後散開所致；而ILF89雖也有類似的表現，但單位Trp產生的螢光升高有限，因此推測ILF89產生寡聚體較小。配合其他文獻的觀察，我們認為W8、W9與胜肽的聚集很有關係，而胜肽的聚集在其溶血活性上扮演著重要的角色。 Indolicidin has broad spectrum of antimicrobial activity against Gram-positive and Gram-negative bacteria, fungi, and virus. However, a limitation to the expression of indolicidin in therapeutic application is its hemolytic activiry. In this study, we focus on the reason of hemolysis of indolicidin. Here, a new indolicidin’s analog ILF89, where the tryptophan at the 8th, and 9th position replaced by phenylalanine, is designed to decrease hemolytic activity. We measure the antimicrobial and hemolytic activity of indolicidin and its analogs, and investigate the mechanism of peptides with the help of fluorescence spectrum. ILF89 remains good antimicrobial activity and substantially decreases the hemolytic activity in biological assay. It demonstrates that W8 and W9 are related to hemolysis of peptides. In the fluorescence spectrum for IL and ILF89 in aqueous phase, the fluorescence intensity of IL with five tryptophans is lower than that of ILF89 with three tryptophans. We conjecture that IL may aggregate in oligomer form at low concentration in aqueous phase and decrease self-fluorescence. In addition, we research the interaction between peptides and POPC or POPG/POPC liposomes. The unit of tryptophan intensity substantially rises in IL and liposomes coexistence system. We infer that IL aggregates disperse after its adsorption to liposomes. ILF89 has similar exhibition but the unit of tryptophan intensity is lower than that of IL. Thus, we think that the oligomers of ILF89 are smaller than that of IL. According to the observation of other literatures, we consider that W8 and W9 are related to peptide aggregation, which plays an important role in hemolytic activity.
