Vibrational spectra of cholorophylls a and b labeled with 26Mg and 15N

Chlorophyll molecules having their central natural magnesium replaced by 26Mg and their natural nitrogens by 15N were obtained by biosynthesis and examined by infrared and resonance Raman spectrometry. These observations provide unequivocal assignments of the molecular vibrational frequencies which involve the magnesium and nitrogen atoms. In particular, in both infrared and resonance Raman spectra, the absence of displacements in bands of frequency higher than 1550 cm-1 indicated the insignificant contributions of C=N stretching modes, which have maximum activity in the 1050 to 1180 cm-1 region. These results also indicate a configuration of chlorophyll in which the magnesium atom is not at a center of symmetry