Polarization properties of v10 v11 and v19 modes of (de)oxyheme of hemoglobin as obtained from three-color CSRS

摘要

Abstract: We report polarization sensitive coherent Stokes Raman scattering (CSRS) measurements of oxy- and deoxyhemoglobin in aqueous solutions that were carried out under electronic resonance with the Q absorption bands. All independent susceptibility $Chi$+(3)$/ components as well as anisotropic and anti-symmetric scattering contributions were resolved within frequency nondegenerate CSRS scheme. Eight bands of oxy- and five of deoxyhemoglobin were observed in the range 1500 - 1680 cm$+$MIN@1$/. Each set of dispersion profiles was simultaneously fitted with a set of parameters including band positions, widths, amplitudes, phases and, importantly, all the CSRS depolarization ratios. On this basis the major bands were assigned to non-totally symmetric $nu$-10$/, $nu$-11$/, and $nu$-19$/ modes of the porphyrin macrocycle. These displayed a clear correlation of vibrational phase with the mode symmetry. Of eight bands resolved in oxyHb spectra three were attributed to features of intermediate deoxyHb, caused by a partial photolysis of oxyhemes. On a nanosecond time scale they were found essentially similar to those found for stable deoxyHb. A detectable isotropy was observed for all non-totally symmetric modes of both oxy- and deoxyhemes. The $nu$-10$/ and $nu$-11$/ modes were found to exhibit anti-symmetry as well. The decrease in depolarization ratio $rho$-1212$/$+R$/ of anomalously polarized $nu$- 19$/ mode from 7.7 (oxyheme) to 4.3 (deoxyheme) was detected. The latter evidenced heme deformation related with a further doming that occurs upon release of oxygen. !14