Three cell-penetrating peptides (CPPs), Tat, Pep-3 and penetratin, were split into two parts and each fragment was terminated with a cysteine residue, to allow disulfide bridge formation, as well as a fluorescent label, for visualization and quantitative analysis. After disulfide formation between two complementary CPP fragments, cellular uptake of the resulting conjugates was observed. As confirmed by in vitro experiments, the conjugated peptides showed uptake activity comparable to the native CPP sequences, while the truncated peptides were hardly active. Until now, this split CPP strategy has only been demonstrated for oligo-arginine CPPs, but here we demonstrate that it is also applicable to other cell-penetrating peptides. This wider applicability may help in the design of new activatable cell-penetrating peptides for, e.g., targeted drug delivery.

将三个穿透细胞的肽（CPP）Tat，Pep-3和penetratin分成两部分，每个片段都以半胱氨酸残基终止，以形成二硫键以及荧光标记，以进行可视化和定量分析。在两个互补的CPP片段之间形成二硫键后，观察到细胞吸收了所得的缀合物。如体外实验所证实，缀合的肽显示出与天然CPP序列相当的摄取活性，而截短的肽几乎没有活性。到目前为止，这种分裂CPP策略仅在寡精氨酸CPP中得到证明，但在这里我们证明它也适用于其他穿透细胞的肽。这种更广泛的适用性可能有助于设计新的可激活的细胞穿透肽，例如