The PSN peptide, with the amino acid sequence CDAEWVDVS, is a synthetic ligand designed to selectively bind to P-selectin. P-selectin is a cell adhesion molecule that is upregulated on the surface of activated platelets. The peptide functions as a targeting moiety, enabling specific molecular recognition and binding to this receptor. This interaction facilitates the directed association of peptide-conjugated constructs with activated platelet surfaces.

In the described research, the PSN peptide was conjugated to human serum albumin (HSA) to form a modified protein, PSN-HSA. This conjugate was subsequently used in the assembly of hybrid albumin-based nanoparticles via a disulfide reprogramming method. The incorporation of the PSN peptide imparts these nanoparticles with the capacity for targeted binding to P-selectin-expressing activated platelets. This property is leveraged in experimental systems to study directed interactions at cellular interfaces.

• Zhao W, Li T, Long Y, Guo R, Sheng Q, Lu Z, Li M, Li J, Zang S, Zhang Z, He Q. Self-promoted Albumin-Based Nanoparticles for Combination Therapy against Metastatic Breast Cancer via a Hyperthermia-Induced "Platelet Bridge". ACS Appl Mater Interfaces. 2021 Jun 9;13(22):25701-25714. doi: 10.1021/acsami.1c04442. Epub 2021 May 27. PMID: 34041901.
• Doolittle E, Peiris PM, Doron G, Goldberg A, Tucci S, Rao S, Shah S, Sylvestre M, Govender P, Turan O, Lee Z, Schiemann WP, Karathanasis E. Spatiotemporal Targeting of a Dual-Ligand Nanoparticle to Cancer Metastasis. ACS Nano. 2015 Aug 25;9(8):8012-21. doi: 10.1021/acsnano.5b01552. Epub 2015 Jul 28. PMID: 26203676; PMCID: PMC4579532.

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。