The TAT-DEF-Elk-1 peptide is a synthetic cell-penetrating peptide designed to specifically interfere with the DEF docking domain of the transcription factor Elk-1. This domain is crucial for the interaction between Elk-1 and activated extracellular signal-regulated kinases (ERKs). The peptide mimics the DEF domain, thereby blocking ERK-mediated phosphorylation of Elk-1 on critical serine residues (Ser383/389) without affecting ERK activation or its ability to phosphorylate other substrates such as MSK-1 and CREB.

Elk-1 is a key transcription factor involved in neuronal differentiation and cytoskeleton dynamics. Its phosphorylation by ERKs triggers nuclear translocation and subsequent serum response element (SRE)-dependent gene expression. The TAT-DEF-Elk-1 peptide effectively prevents Elk-1 nuclear translocation and phosphorylation, providing a tool to study the specific role of Elk-1 activation in cellular processes. This peptide has been shown to differentially regulate immediate early gene expression compared to classical ERK pathway inhibitors, highlighting its specificity for Elk-1-dependent pathways.

• Lavaur J, Bernard F, Trifilieff P, Pascoli V, Kappes V, Pagès C, Vanhoutte P, Caboche J. A TAT-DEF-Elk-1 peptide regulates the cytonuclear trafficking of Elk-1 and controls cytoskeleton dynamics. J Neurosci. 2007 Dec 26;27(52):14448-58. doi: 10.1523/JNEUROSCI.2279-07.2007. PMID: 18160653; PMCID: PMC6673434.

三氟乙酸（TFA）是一种强酸，常用于从固相树脂中裂解合成的多肽，也可用于提高多肽纯化步骤中的HPLC性能。默认情况下，定制的多肽是以冻干的TFA盐的形式交付的，其中TFA的含量可能高达10-45%。

定制多肽中的TFA可能会导致后续检测数据出现无法解释的差异。例如，nM浓度的TFA已被证明会干扰细胞实验，在某些情况下会抑制细胞增殖，而在其他情况下会增加细胞活力。

TFA去除服务推荐用于:

• 将用于细胞试验的多肽
• 将被用作原料药或制成品的多肽
• 含有大量碱性残基的亲水多肽

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。