The 11R-VEET peptide is a synthetic, cell-permeable peptide designed as a control for studies of calcineurin-NFAT signaling interference. It is composed of an 11-arginine cell-penetrating peptide (11R) linked via a three-glycine linker to a scrambled version of the VIVIT peptide sequence (MAGPPHIVEETGPHVI). The 11R sequence facilitates translocation across cellular membranes. Unlike the active VIVIT peptide, which contains the high-affinity calcineurin-docking PxIxIT motif, the VEET sequence has the same amino acid residues rearranged in a scrambled order. This renders the 11R-VEET peptide incapable of specifically competing with the native NFAT PxIxIT motif for binding to calcineurin. Consequently, it does not affect calcineurin-dependent NFAT dephosphorylation, nuclear translocation, or transcriptional activity.

In experimental contexts, particularly in human glioma cells, the 11R-VEET peptide serves as a negative control. Its use allows researchers to distinguish specific effects of the active 11R-VIVIT peptide from non-specific effects, such as those potentially induced by the 11R transduction domain or general peptide uptake. The 11R-VEET peptide does not alter the subcellular localization of NFAT proteins (e.g., NFATc1, NFATc3), nor does it modulate the activity of NFAT-responsive promoters or the expression of endogenous NFAT target genes like COX2 and c-MYC, confirming its inert role in the calcineurin-NFAT pathway.

• Ellert-Miklaszewska A, Szymczyk A, Poleszak K, Kaminska B. Delivery of the VIVIT Peptide to Human Glioma Cells to Interfere with Calcineurin-NFAT Signaling. Molecules. 2021 Aug 7;26(16):4785. doi: 10.3390/molecules26164785. PMID: 34443374; PMCID: PMC8400789.
• Pereverzev A, Komarova SV, Korcok J, Armstrong S, Tremblay GB, Dixon SJ, Sims SM. Extracellular acidification enhances osteoclast survival through an NFAT-independent, protein kinase C-dependent pathway. Bone. 2008 Jan;42(1):150-61. doi: 10.1016/j.bone.2007.08.044. Epub 2007 Sep 14. PMID: 17964236.

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。