The core antenna CP43 of photosystem II was purified from the PSII core complex of spinach by DEAE-Toyopearl-650S anion-exchange chromatography, using the mild nonionic detergent beta-dodecyl maltoside and high concentration of LiClO(4). At room temperature, the purified CP43 has a maximum absorption at 671 nm, a fluorescence maximum at 683 nm and doublet CD signals which indicated the presence of excitonic interactions between some chlorophylls. The pigment content of the CP43 was 20 - 21 Chl a per CP43 polypeptide as determined by a spectroscopic method. The results suggested that the purified CP43 was still in a native state. Moreover, the specific antiserum was obtained and identified.