DR8 (DHNNPQIR-NH2) is an antioxidant peptide extracted and purified from rapeseed (Brassica campestris L.). It belongs to a class of naturally occurring peptides with biological activity. However, natural peptides are susceptible to degradation by proteases, which limits their stability and duration of action.

To address this limitation, a structural analog, DR7dA [DHNNPQ(D-alanine)R-NH2], was developed by replacing L-isoleucine with D-alanine. This modification significantly improved the serum stability of DR7dA compared to its parent peptide, DR8. DR7dA retains the ability to inhibit fibrogenesis and extracellular matrix deposition by suppressing the mitogen-activated protein kinase (MAPK) signaling pathway and reducing oxidative stress. These properties make it a promising candidate for further scientific investigation.

• [1] Cheng L, Wang D, Deng B, Li J, Zhang J, Guo X, Yan T, Yue X, An Y, Zhang B, Xie J. DR7dA, a Novel Antioxidant Peptide Analog, Demonstrates Antifibrotic Activity in Pulmonary Fibrosis In Vivo and In Vitro. J Pharmacol Exp Ther. 2022 Aug;382(2):100-112. doi: 10.1124/jpet.121.001031. Epub 2022 Jun 30. PMID: 35772783.
• [2] Xu F, Wang L, Ju X, et al. Transepithelial Transport of YWDHNNPQIR and Its Metabolic Fate with Cytoprotection against Oxidative Stress in Human Intestinal Caco-2 Cells. Journal of Agricultural and Food Chemistry. 2017;65(10):2056-2065 DOI: 10.1021/acs.jafc.6b04731
• [3] Wang D, Yan Z, Bu L, et al. Protective effect of peptide DR8 on bleomycin-induced pulmonary fibrosis by regulating the TGF-β/MAPK signaling pathway and oxidative stress. Toxicology and Applied Pharmacology. 2019;382:114703 DOI: 10.1016/j.taap.2019.114703
• [4] Deng B, Yang W, Wang D, et al. Peptide DR8 suppresses epithelial-to-mesenchymal transition via the TGF-β/MAPK signaling pathway in renal fibrosis. Life Sciences. 2020;261:118465 DOI: 10.1016/j.lfs.2020.118465

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。