Preparation And Structural Analysis Of Natural Peptides From The Frog Skin Secretions

The widespread use and misuse of traditional antibiotics has resulted in the emergence of many multidrug-resistant microorganisms. Therefore, antibiotic resistance is an increasingly serious problem, and the development of new types of antibiotics is urgently needed. Antimicrobial peptides (AMPs) from amphibian have become important candidates as potential therapeutic agents because of their broad-spectrum antimicrobial and ancancer activity.Chinese brown frogs (Rana chensinensis) growth in the northeast of China. Like other amphibian, the skin of Chinese brown frogs is a natural barrier against the invasion of microorganisms and other pathogens in the environment via production of various bioactive peptides in the dorsal skin granular glands. Therefore, these glands are thought to be one of the richest sources of bioactive peptides, exhibiting a broad spectrum of antimicrobial activity against Gram-positive and Gram-negative bacterium and cytotoxic activity responsible for inhibiting the growth of cancer cells. In this present study, Rana Chensinensis was used as experimental material. The frog skin secretions were obtained by mild electrical stimulation. Then, these secretions were isolated and purified by the prepared high performance liquid chromatography and the fractions F18, F24, F28, F30, F31, F34, F36, F37, F40, F43, F46, F49, F5020, F55, F57, F58, F60, F62,F66and F70were obtained. Among of them, F40, F43, F46, F49, F50, F57, F60, F62and F66exhibited antimicrobial active and were further purified by the analyzed high performance liquid chromatography. The molecular weight and amino acid sequence of the purified fractions F46, F49, F57, the F60were determined by MALDI-TOF/TOF MS and Q-TOF/TOF MS, respectively. The molecular weight range of these fractions is566-3699Da, the amino acid number of peptide was from five to thirty seven. The results of bioinformatics showed that these fractions contained three of bradykinin peptides, an angiotensin-like peptide and other peptides. All of these peptides adopted stable structure, such as8peptide adopted a-helix structure and another peptides exhibited random coil structure...