indicating an excess of the conformation of the pigment. But when the pigment's propionic acids are linked together by -(CH2)n- chains in cyclic esters, the choice of cyclic ester conformation and pigment helicity is governed by the number (n) of CH2 units, with Δϵ near 640 nm varying from positive when n=1, 5 and 6, to negative when n=2, 3 and 4.
(βS,β '小号)-Dimethylmesobiliverdin-XIIIα二甲
酯显示出阳性长波长圆二色性Cotton效应(Δε 644最大= 6.1)在CHCl 3,说明过量的的
颜料的构象。但是,当
颜料的
丙酸通过环
酯中的-(CH 2)n链连接在一起时,环
酯构象和
颜料螺旋度的选择取决于CH 2单元的数量(n),Δϵ在640 nm附近变化从当n = 1、5和6时为正,到当n为负时= 2、3和4。