Bovine lactoferricin (LfcinB) is a cationic antimicrobial peptide derived from the N-terminus of bovine lactoferrin, an iron-binding glycoprotein found in neutrophil granules and secretions such as tears, saliva, and milk. LfcinB consists of amino acid residues 17–41 and possesses a net charge of +8 due to five arginine and three lysine residues, along with two tryptophan and two phenylalanine residues that confer both aromatic and hydrophobic properties. The peptide adopts an amphipathic beta-sheet configuration in aqueous solution, with hydrophobic residues aligned on one face and basic residues on the opposing face, enabling interaction with anionic components of cell membranes. The antimicrobial core of LfcinB, designated LfcinB6, comprises the six-amino acid sequence RRWQWR. This core peptide adopts a well-defined amphipathic structure when bound to sodium dodecyl sulfate micelles.

LfcinB6 has a net charge of +3 conferred by its three arginine residues. Unlike the full-length LfcinB, LfcinB6 does not bind to or disrupt the cell membranes of cancer cells, such as T-leukemia or breast carcinoma cells, and shows weaker binding to isolated mitochondria. However, when delivered directly into the cytosolic compartment via fusogenic liposomes, LfcinB6 exhibits strong cytotoxicity. This intracellular cytotoxicity involves cathepsin B and caspase activation, but not reactive oxygen species, and does not involve mitochondrial membrane permeabilization or cytochrome c release, indicating a mechanism of action distinct from that of the full-length LfcinB peptide.

• Goodman RE, Schanbacher FL. Bovine lactoferrin mRNA: sequence, analysis, and expression in the mammary gland. Biochem Biophys Res Commun. 1991 Oct 15;180(1):75-84. doi: 10.1016/s0006-291x(05)81257-4. PMID: 1718281.
• Richardson A, de Antueno R, Duncan R, Hoskin DW. Intracellular delivery of bovine lactoferricin's antimicrobial core (RRWQWR) kills T-leukemia cells. Biochem Biophys Res Commun. 2009 Oct 30;388(4):736-41. doi: 10.1016/j.bbrc.2009.08.083. Epub 2009 Aug 21. PMID: 19699713.

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。