The PTD-p65-P1 peptide is derived from the p65 subunit of NF-κB, specifically targeting amino acid residues 271–282, which include the phosphorylation site Ser276. This peptide is linked to a protein transduction domain (PTD) from the third helix sequence of antennapedia, enabling efficient cellular uptake. PTD-p65-P1 selectively inhibits NF-κB activation by blocking p65 phosphorylation and nuclear translocation without affecting IκBα degradation or IKK activation. It suppresses NF-κB DNA binding and downstream gene expression, demonstrating specificity by not interfering with AP-1 activation. The peptide's mechanism involves competitive inhibition of p65 phosphorylation, crucial for NF-κB transcriptional activity.

In vitro studies show that PTD-p65-P1 directly inhibits recombinant p65 binding to DNA, independent of PTD linkage. The peptide's efficacy is sequence-dependent, requiring intact Ser276 for function. PTD-p65-P1 broadly inhibits NF-κB activation induced by diverse stimuli, including TNF, LPS, and oxidative stress, indicating action at a convergent pathway step. Its ability to modulate NF-κB-dependent processes highlights its utility as a molecular tool for studying NF-κB signaling.

• Takada Y, Singh S, Aggarwal BB. Identification of a p65 peptide that selectively inhibits NF-kappa B activation induced by various inflammatory stimuli and its role in down-regulation of NF-kappaB-mediated gene expression and up-regulation of apoptosis. J Biol Chem. 2004 Apr 9;279(15):15096-104. doi: 10.1074/jbc.M311192200. Epub 2004 Jan 7. PMID: 14711835.

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。