Hemoglobin vibrational spectroscopy

The natural geometry of biomolecules can be exploited to clarify the SERS sensitivity dependence on distance from the surface. This aspect of SERS spectroscopy is important for the interpretation of the SERS spectrum of a biopolymer. The electromagnetic model predicts very rapid decay of SERS with increasing distance Thus, in small molecules with a dimension of approximately 0.6 nm (benzene) all vibrations of the molecule can be enhanced. In large biomolecules with diameters of about 6 nm (hemoglobin protein) only groups which are attached directly to the surface will yield SERS. This important aspect is illustrated by SERS studies of three examples mono-, di-, and polynucleotides. 

Perhaps the most important application of resonance Raman spectroscopy has been to the study of biological molecules under physiologically significant conditions that is, in the presence of water and at low to moderate concentration levels. As an example, the technique has been used to determine the oxidation state and spin of iron atoms in hemoglobin and cytochrome c. In these molecules, the resonance Raman bands are due solelv to vibrational modes of the tetra-... 

---