Six pigment-containing bands were isolated from Codium fragile thylakoids using sodium dodecyl sulphate/polyacrylamide gel electrophoresis. Two, designated CPla and CP1, were associated with Photosystem I and enriched in chlorophyll a and a-carotene, and two light-harvesting complexes (dimer LHCP1 and monomer LHCP2) were enriched in chlorophyll b, siphonoxanthin, siphonein and neoxanthin. A fifth pigment/protein (CPa) was not successfully characterized. Undissociated free pigment contained almost all the violaxanthin recovered from gel eluates and a high concentration of siphonoxanthin.

Several high (100 ± 3.0 to 62 ± 7.7 kilodaltons) and two low molecular weight proteins (15.2 ± 1.2 to 16.5 plusmn; 1.2 and 18.0 kilodaltons) were thought to be associated with CPla and CP1. LHCP1 contained a protein of molecular weight 56 ± 24 kilodaltons and LHCP, a 29 kilodaltons protein, however the behaviour of these complexes after denaturation was particularly unusual in that on re-electrophoresis the denatured monomer appeared to reassociate and proteins of 59, 56 and 28 kilodaltons were resolved. The composition of these pigment/protein complexes suggests that a large proportion of the pigments present in C. fragile chloroplasts function in a light-harvesting capacity and this may be an adaptation to submarine photosynthesis.