Novel Fluorescently Labeled Peptide Compounds for Detection of Oxidized Low‐Density Lipoprotein at High Specificity

The probes for specific detection of oxidized low‐density lipoprotein (ox‐ LDL ) in plasma and in atherosclerotic plaques are expected to be useful for the identification, diagnosis, prevention, and treatment for atherosclerosis. In this study, to develop a fluorescent peptide probe for specific detection of ox‐ LDL , we investigated the interaction of fluorescein isothiocyanate ( FITC )‐labeled peptides with ox‐ LDL using polyacrylamide gel electrophoresis. Two heptapeptides ( KWYKDGD and KP 6) coupled through the ε ‐amino group of K at the N‐terminus to FITC in the presence/absence of 6‐amino‐n‐caproic acid ( AC ) linker to FITC —( FITC ‐ AC ) KP 6 and ( FITC ) KP 6—both bound with high specificity to ox‐ LDL in a dose‐dependent manner. In contrast, a tetrapeptide ( YKDG ) labeled with FITC at the N‐terminus and a pentapeptide ( YKDGK ) coupled through the ε ‐amino group of K at the C‐terminus to FITC did not bind selectively to ox‐ LDL . Furthermore, ( FITC ) KP 6 and ( FITC ‐ AC ) KP 6 bound with high specificity to the protein in mouse plasma (probably ox‐ LDL fraction). These findings strongly suggest that ( FITC ) KP 6 and ( FITC ‐ AC ) KP 6 may be effective novel fluorescent probes for specific detection of ox‐ LDL .