A new method for the rapid and efficient screening of affinity ligands to biological targets is reported. The fusion peptide of influenza virus A was used as the model target and immobilized on the PGMA beads. Antisense peptide YRSKQA of fusion peptide was chosen as the lead compound. The special positional scanning peptide libraries were designed based on YRSKQA and synthesized by utilizing solid phase peptide synthesis manually. The libraries were YRSKQX, YRSKXA, YRSXQA, YRXKQA, YXSKQA and XRSKQA, where X represented 18 L-amino acids(except for Cys and Trp). Each library was screened by affinity chromatography. The eluates from the fusion peptide affinity column were collected and analyzed by RP-HPLC and MS, respectively, in order to determine the kind of X at each position. After the preferred residues of six positions were decided, the two preferred peptide sequences, GRGKHK and TRGKHK, were obtained. The dissociation constants of GRGKHK, TRGKHK and YRSKQA, were 3.35×10 -6, 5.24×10 -6 and 1.15×10 -5 mol·L -1, respectively. The preferred peptides showed the higher affinity binding to immobilized fusion peptide than the lead peptide.
A micro-video imaging system on-line coupled with UV detection and capillary electrophoresis has been set up and used for the investigation of human red blood cells（hRBC）. Both free and aggregated cells were observed via the imaging and the broad peak overlain by bar-like peaks measured from UV detection was shown responsible for the free migrated and aggregated cells, respectively. More importantly, fast measurement of cell mobility was achieved within one second using the image acquired and the calculated mobility data agreed with that of UV, giving a deviation of less than 7%. Further more, this micro-video system allows us to vividly observe the adsorption-desorption process. In a fused-silica capillary, about 10% of the human red blood cells were turned out to adsorb on the tubing surface, they left the surface after 0.04 s to 3.12 s, giving an average retarding time of less than 1 s. This causes a loss of migration mobility of 5×10-6 cm2·V-1·s-1. It was thought that this system be applicable to the study of adsorption of other types of molecules with some modification.
