Coordination of Thrombolytic Pro-Ala-Lys peptides with Cu (II): Leading to Nanoscale Self-assembly, Increase of Thrombolytic Activity and Additional Vasodilation

Vasodilation is one of the biologically important properties for thrombolytic agents because of it may help thrombolysis via dilating blood vessels. Aimed at discovering agents with the dual-action of vasodilative and thrombolytic activities, H-Pro-Ala-Lys (PAK, 3a) and five novel analogs H-Pro-Ala-AA (2b-f, AA = Val, Phe, Ser, Glu, and His) were coordinated with Cu(II) to form Cu(II)-Pro-Ala-AA [(3a-f)-Cu(II)]. The coordination chemistry was confirmed by the d-d transition occurred in their UV and circular dichroism (CD) spectra and the molecular ion in their electrospray ionization mass spectrometry (ESI-MS) spectra. The particle size tests of their solution and powders revealed that the coordination generally resulted in nanoscale self-assembly. Zeta potential and half-peak width tests indicated that the formed nanoparticles were sufficiently stable during the monitored 8 days. The bioassays implied that comparing to the PAK peptides themselves and CuCl 2 the coordination led to a 3000-fold increase of the in vitro thrombolytic activity, a 10-fold increase of the in vivo thrombolytic activity, and especially an additional vasodilation. Thus Cu(II)-peptide coordination indeed is a way for thrombolytic peptide design.