Effect of Sodium Dodecyl Sulfate on Structure and Spectroscopic Characteristics of Water-Soluble Chlorophyll Protein Complex Isolated from Stems of <italic>Lepidium virginicum</italic>

Abstract

The relationship between structure and spectroscopic characteristics of the watersoluble chlorophyll protein complex isolated from stems of Lepidium virginicum (CP663S) was studied. Addition of 0.08% SDS induced a red shift of the 663 nm absorption maximum. At the same time, under excitation at 435 nm, the maximum of fluorescence emission shifted from 672 nm to 675 nm and the fluorescence yield increased. When CP663S was excited at 480 nm, the 660 nm emission band of chlorophyll b became more prominent. Fluorescence lifetime of emission from chlorophyll a increased on addition of SDS. The energy transfer from chlorophyll 4 to chlorophyll a was decreased by the SDS addition, as judged by the fluorescence spectra and lifetime measurement. Symmetrical positive and negative peaks of the circular dichroism (CD) spectrum around 669 nm, which indicate the interaction between chlorophyll a molecules at short distances, disappeared after addition of SDS. These SDS-induced changes of spectroscopic characteristics occurred in similar SDS concentration ranges and were reversible. SDS polyacrylamide gel electrophoresis cleaved CP663S into subunits. Chlorophyll molecules moved with protein moieties. Glutaraldehyde treatment suppressed the effects of SDS on absorption, fluorescence and CD characteristics. We conclude that chlorophyll molecules in CP663S are in the hydrophobic region of the protein and the interaction between chlorophyll a molecules occurs at short distances. Changes of spectroscopic characteristics are a result of cleavage of CP663S.