SMCC (N-Succinimidyl 4-(N-maleimidomethyl)cycl) is a heterobifunctional protein crosslinker.

N-Succinimidyl 4-(N-maleimidomethyl)cyclohexanecarboxylate（SMCC）是一种胺基至巯基交联剂，它在一个中等长度的环己烷稳定间隔臂（8.3埃）的两端含有NHS酯和马来酰亚胺活性基团。SMCC通过具有巯基（硫醇；-SH）活性的马来酰亚胺基团和具有胺活性的NHS酯基团进行结合，形成稳定的共价蛋白质交联。

Branched PEI (25 kDa) was dissolved in PBS buffer to yield a concentration of 1 mg/mL. No-weigh Sulfo-SMCC was dissolved in Milli-Q water with a concentration of 10 mg/mL, then a certain of the prepared no-weigh SulfoSMCC solution was added into 2 mL PEI solution to incubate for 30 min at 37 C. After the PEI-SMCC polymer was formed, TAT solution was added into the polymer at the given molar ratio and incubated for 2 h at 4 C. The concentration of unreacted SMCC and unreacted TAT were removed using Zeba Spin Desalting Columns. The polymer PEI-SMCC-TAT was also characterized and analyzed through FTIR to check if each element was added to the PEI backbone.