the strain induced in the iron-imidazole bond by the short hemin results in a higher nu ( fe -- n epsilon ) frequency , in contrast to the strain induced by sterically hindered 2-methylimidazole or 1,2-dimethylimidazole complexes in which the fe -- n epsilon bond is tilted and lengthened , but the imidazole ring remains perpendicular to the heme plane .
C0018988
hemin
C0018966
heme