| Photosynthesis is the most important biochemical reaction in the world, which occurs at the thylakoid in chloroplast. Because solar energy is the power of photosynthesis, absorbing and transferring solar energy is the key factor affecting the photosynthetic process directly. In higher plants, the peripheral light-harvesting complex (LHCIIb) of photosystem II (PSII) is the most important apparatus to absorb solar energy. Besides light harvesting, LHCIIb plays an important role in photoprotection via heat dissipation, and in proper energy distribution between the two photosystems via the migration of the phosphorylated LHCIIb. LHCIIb is also very important in maintaining the grana structure in thylakoid. The electron crystallography to the structure of LHCIIb at 2.72? resolution reveals that each monomeric LHCIIb contains three transmembraneα-helix (helix A, B and C) and two amphipathicα-helix (helix D and E) which binds 14 chlorophylls (8 chlorophyll a and 6 chlorophyll b), two luteins, one neoxanthin and one violaxanthin. Although the structure and the function of LHCIIb have already been illuminated in detail, the character of the structure and function of each isoforms of LHCIIb (Lhcb1, Lhcb2 and Lhcb3) is still lacking. In order to study the character of three isoforms of LHCIIb, the gene of each form from pea (Pisum sativum L.) has been amplified and overexpressed in E.coli, the protein has been reconstituted in vitro, and the spectral character and structure stability of each isoform have been investigated in this thesis.The alignment results show that the Lhcb1 and Lhcb3 are more conserved than Lhcb2. The sequence of Lhcb1 shows higher level of identity to Lhcb2 than to Lhcb3. Analysis of the CD spectra in UV region shows thatα-helices content of Lhcb1 homotrimer is higher than that of Lhcb1 monomer, and similar to those of Lhcb2 and Lhcb3. The fourth deviation of absorption spectra of each isoform shows that there are two absorption centers of Chl a in Lhcb1 and Lhcb2.
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