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  • Title: Photoinduced oxygen dynamics in lyophilized hemoglobin.
    Author: Nöllmann M, Etchegoin P.
    Journal: Spectrochim Acta A Mol Biomol Spectrosc; 2000 Dec; 56(14):2817-29. PubMed ID: 11145349.
    Abstract:
    Reversible laser induced deoxygenation in the lyophilized phase of hemoglobin is demonstrated by means of resonant Raman scattering, luminescence, and optical transmission. Specific Raman modes, which are both sensitive to the spin states of Fe(II) in the hemes and resonant in the visible, are monitored as a function of time to evaluate the effect of the illuminating laser. These modes act as in-situ markers of the oxygen content of the protein. The reversible photoinduced deoxygenation can be observed through both the Raman spin-markers and the optical transmission experiments. In the former, reversible changes in the intensities of specific Raman modes are observed, while in the latter, the oscillator strength of the two main absorptions of oxyhemoglobin in the visible are seen to vary accordingly. The luminescence in lyophilized hemoglobin is found to have at least two different contributions, (i) a resonant component with the Raman modes and; (ii) a nonresonant contribution, which increases at high input laser powers and eventually masks the Raman signals. The nonresonant contribution is the luminescence of the photoproduct achieved by thermal denaturation of the protein and remains standing as a permanent nonreversible damage in the illuminated spot. Semiempirical electronic calculations of the wavefunction and total energy of the iron porphyrin reveal the underlying physical origin of the laser induced deoxygenation process in the hemes and are also presented.
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