运用休克尔分子轨道 (HMO)理论对紫红质中的色基 -视黄醛骨架异构化现象进行了讨论。近似计算结果表明 :紫红质中视黄醛骨架共轭体系π→π* 跃迁的最大吸收峰λmax=5 63 nm,这与紫红质的 λmax=498nm相近 ,但更接近受压紫红质的实验结果 λmax=5 3 4nm;且视黄醛骨架结构共轭体系中 C11-C12 之间激发态的 π键级为 1 .5 860 ,明显小于基态 π键级 1 .7469值 ,故当紫红质吸收光能进入激发态之后 ,1 1 -顺式视黄醛色基则更易发生异构化 Shock molecular orbital (HMO) theory is used to discuss the isomerisation of chromophore-retinal skeleton in purpurin. The approximate calculation results show that the maximal absorption peak λmax of π → π * transition of retinol skeleton conjugate in purpuroids is close to λmax = 498nm, but closer to the experimental result λmax of pressurized rhodopsin = 5 3 4nm; and the π bond order of the excited state of C11-C12 in the retinoid framework conjugate system is 1.5860, which is obviously smaller than the value of the ground state π-bond 1 .7469, Into the excited state, 1 1 - cis retinal chromophore is more prone to isomerization