两栖动物皮肤中含有大量分子结构特殊、功能复杂多样的生物活性物质，其中抗菌肽含量及种类尤为丰富。来自于非洲爪蟾的抗菌肽magainin的修饰物已应用于临床，用于治疗糖尿病人足部感染。海南省由于独特的地理条件，自然环境和气候条件，两栖动物资源丰富而独特。本项目选取种群数较多的沼蛙，构建其皮肤活性蛋白多肽分子资源库，目前已在其中筛选分离出一个抗菌肽。该抗菌肽对革兰氏阳性菌，如金黄色葡萄球菌、无乳链球菌、枯草芽胞杆菌，及革兰氏阴性菌大肠杆菌均显示较强的抑制活性。本研究将利用RT-PCR方法，并结合N-末端氨基酸序列测定，确定其氨基酸序列。利用化学合成法合成该抗菌肽及其突变体，检测化学合成抗菌肽的抗菌活性及抗菌谱，尤其对于临床耐药菌的抗菌活性，以分析其结构和功能的关系。利用生物膜模型结合电子显微镜观察，研究其抗菌机理。该结果将为研究与开发新型广谱抗菌药物提供理论依据及基础。

Amphibian skin is a morphologically, biochemically, and physiologically complex organ that fulfills a wide range of functions necessary for amphibian survival. Many bioactive substances with special molecular structure and complex function are found in amphibian skin, especially for antimicrobial peptides. Magainin, a class of antimicrobial peptide obtained from Xenopus laevis has been applyed to treat the infection in diabetic foot. Endemic amphibian are widely distributed in Hainan province, because of the special localization, environment，and climate. At present, the libiraies of bioactive proteins and peptides have been constructed from Rana guentheri skin secretion of Hainan province, in which an antimicrobial peptide has been screened and purified. The antimicrobial peptide exhibited potent antibacterial activities not only to Gram-positive bacteria, such as Staphylococcus aureus,S. Agalactiae and Bacillus subtilis, but also Gram-negative bacteria Escherich coli. The amino acid sequence of the antimicrobial peptide will be determined by RT-PCR and N-terminal amino acid analyses. The solid-phase peptide systhesis strategy will be used to obtain the original peptide and mutants which is used to detect the antimicrobial activity, especially to the drug-resistant strains in clinic. The results will elicit the relationship between structure and function of the antimicrobial peptide. The antibacterial mechanism of the antimicrobial peptide will be detected with the artificial cell membrane. The results will help us to research and develope a novel wide-spectrum antibiotic peptide.