Circular dichroism studies at variable temperature: urobilinoid conformation.
Measurements of the temperature dependence of the circular dichroism spectra of l-stercobilin and d-urobilin show that the conformations of these optically-active urobilinoids change with temperature between 163 and 297 degrees K. These conformational changes depend critically on the hydrogen bonding characteristics of the solvent. Thus, in methanol-glycerol (9:1), the chiral sense of the helical conformation of the dipyrrylmethene chromophore is reversed on lowering the temperature, whereas in chloroform, reversal does not occur.
D001654:Bile Pigments; D002942:Circular Dichroism; D008956:Models, Chemical; D009905:Optical Rotatory Dispersion; D012997:Solvents; D013237:Stereoisomerism; D013696:Temperature
D001654:Bile Pigments; D012997:Solvents