Pexiganan is a 22-amino-acid antimicrobial peptide, chemically synthesized as an analog of the magainin peptides originally isolated from the skin of the African clawed frog Xenopus laevis. Its primary structure is Gly-Ile-Gly-Lys-Phe-Leu-Lys-Lys-Ala-Lys-Lys-Phe-Gly-Lys-Ala-Phe-Val-Lys-Ile-Leu-Lys-Lys-NH₂, with a molecular weight of 2478 Da for the free peptide base. This cationic peptide exhibits broad-spectrum in vitro antibacterial activity against a wide range of gram-positive and gram-negative bacteria, including aerobic and anaerobic species.

The peptide demonstrates rapid bactericidal activity, which is attributed to a membrane-disruptive mechanism. Studies indicate that for the majority of bacterial isolates tested, the minimum bactericidal concentrations (MBCs) are identical to or within a narrow range of the minimum inhibitory concentrations (MICs), confirming its bactericidal mode of action. The antimicrobial activity of pexiganan is largely unaffected by variations in pH within a physiological range. Furthermore, attempts to generate bacterial resistance to pexiganan through repeated in vitro passage with subinhibitory concentrations or through mutagenesis were unsuccessful, and no cross-resistance with several conventional antibiotic classes has been observed.

• Ge Y, MacDonald DL, Holroyd KJ, Thornsberry C, Wexler H, Zasloff M. In vitro antibacterial properties of pexiganan, an analog of magainin. Antimicrob Agents Chemother. 1999 Apr;43(4):782-8. doi: 10.1128/AAC.43.4.782. PMID: 10103181; PMCID: PMC89207.

三氟乙酸（Trifluoroacetic acid，简称 TFA）是高效液相色谱（简称 HPLC）纯化过程中常用的反离子。TFA 的存在可能会对肽的净重量、外观及溶解度产生影响，具体如下：

对净重量的影响：TFA 盐会增加产物的总质量。在大多数情况下，肽的含量占总重量的 80% 以上，剩余部分则为 TFA。

对溶解度的影响：TFA 盐通常能提高肽在水溶液中的溶解度。

在生物检测中的影响：对于大多数标准的体外检测，残留的 TFA 水平一般不会造成干扰。但需注意，在高灵敏度的细胞研究或生化研究中，需关注其存在可能带来的影响。

干品多肽的重量中不仅仅包含多肽，还包含有一些非肽的组份，如水、被吸收的溶剂、配位离子和盐等。肽的净含量是指肽在其中的重量百分比，这个百分比的数值范围很大，可能从50%到90%，取决于纯度、序列以及合成和纯化的方法，不要将肽的净含量和肽的纯度混为一谈，他们是两个完全不同的概念。纯度通常是通过HPLC测定的。纯度定义的是多肽样品中含正确序列的组分的百分比，而肽的净含量是指样品中肽类物质相对于总物质所占的百分比，肽的净含量通常是氨基酸组分分析或紫外分光法测定的，这个信息主要是在一些对肽的浓度很敏感的实验中，对计算肽的浓度是很重要的。