| Summary: | 碩士 === 淡江大學 === 化學學系碩士班 === 100 === Mastoparan-B (MPB-NH2) is an antibacterial cationic tetradecapeptide, isolated from the venom of black-bellied hornet (Vespa basalis) with a primary structure
(LKLKSIVSWAKKVL -CONH2) and amide C-terminus. It forms a random coil in aqueous solution and adopts an ampliphlic α-helical conformation in trifluoroethanol(TFE). A previous study showed that Alanine (Ala) in substitution for Trp9 cause a collapse of the helix. The aromatic ring of the tryptophan in MPB-NH2 is important in the helical stabilization. Recognizing this, we attempt to uncover how an aromatic residue affect the structure and the biological activity of MPB-NH2 and its analogous.
In this study, we replaced Trp9 by phenylalanine and tyrosine in the primary structure of MPB-NH2. Results of CD and NMR indicated no significant change in the helical structure in 30% trifluoroethanol solution.
However, the experiments of antibacterial activity showed that MPB-NH2 has stronger antibacterial activity than [Phe9]- MPB-NH2and [Tyr9]- MPB-NH2. It is likely that the indole ring of tryptophan residue is more effective for membrane perturbation than benzene ring of phenylalanine and the phenol of tyrosine.
Also, a number of NOEs have been found between aromatic residue and other residues.
Here, we proposed that some of these NOEs may imply the fundamental interaction for structure stabilization and activity.
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