Esculentin-2CHa is a host-defense peptide originally isolated from the skin secretions of the Chiricahua leopard frog, Lithobates chiricahuensis. The peptide has the primary structure GFSSIFRGVAKFASKGLGKDLAKLGVDLVACKISKQC and demonstrates potent growth-inhibitory activity against a range of bacteria, including multidrug-resistant isolates of Staphylococcus aureus, Acinetobacter baumannii, and Stenotrophomonas maltophilia, with minimum inhibitory concentrations (MICs) of ≤6 µM. Esculentin-2CHa also exhibits differential cytotoxic activity, with lower toxicity toward human erythrocytes (LC50 = 150 µM) compared to human non-small cell lung adenocarcinoma A549 cells (LC50 = 10 µM).

The peptide has immunomodulatory properties, as it significantly stimulates the release of the anti-inflammatory cytokine IL-10 by mouse lymphoid cells and elevates TNF-α production by peritoneal macrophages. Structure-function analysis reveals that the N-terminal hexapeptide (GFSSIF) is critical for both antimicrobial and cytotoxic activities, as its removal abolishes activity against S. aureus and reduces potency against other bacteria. The cyclic C-terminal domain (CKISKQC) also contributes to peptide activity, while increasing cationicity through amino acid substitutions enhances potency but also raises cytotoxicity against mammalian cells.

• Conlon JM, Mechkarska M, Coquet L, et al. Characterization of antimicrobial peptides in skin secretions from discrete populations of Lithobates chiricahuensis (Ranidae) from central and southern Arizona. Peptides. 2011;32(4):664-9.
• Attoub S, Mechkarska M, Sonnevend A, Radosavljevic G, Jovanovic I, Lukic ML, Conlon JM. Esculentin-2CHa: a host-defense peptide with differential cytotoxicity against bacteria, erythrocytes and tumor cells. Peptides. 2013 Jan;39:95-102.
• Ojo OO, Srinivasan DK, Owolabi BO, Vasu S, Conlon JM, Flatt PR, Abdel-Wahab YH. Esculentin-2CHa-Related Peptides Modulate Islet Cell Function and Improve Glucose Tolerance in Mice with Diet-Induced Obesity and Insulin Resistance. PLoS One. 2015 Oct 29;10(10):e0141549.
• Pantic JM, Jovanovic IP, Radosavljevic GD, Arsenijevic NN, Conlon JM, Lukic ML. The Potential of Frog Skin-Derived Peptides for Development into Therapeutically-Valuable Immunomodulatory Agents. Molecules. 2017 Dec 13;22(12):2071.
• Adesanoye OA, Farodoye OM, Adedara AO, Falobi AA, Abolaji AO, Ojo OO. Beneficial actions of esculentin-2CHa(GA30) on high sucrose-induced oxidative stress in Drosophila melanogaster. Food Chem Toxicol. 2021 Nov;157:112620.

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。