TY - JOUR
T1 - LINEAR DICHROISM STUDY OF METALLOPORPHYRIN TRANSITION MOMENTS IN VIEW OF RADIATIONLESS INTERACTIONS WITH TRYPTOPHAN IN HEMOPROTEINS
AU - Gryczynski, Zygmunt
AU - Bucci, Enrico
AU - Kuba, Joazee:
PY - 1993/10
Y1 - 1993/10
N2 - We measured the linear dichroism of several metalloporphyrins embedded in stretched polyvinyl alcohol (PVA) films to estimate the orientation of the absorption transition moments, which in hemoproteins are relevant to the radiationless energy transfer between tryptophan and heme. The metalloporphyrins were derivatives of protoporphyrin IX (PPIX), namely Fe3+‐PPIX (ferric‐heme) and Fe2+CO‐PPIX (CO‐heme), Mg‐PPIX (Mg‐heme) and Zn‐PPIX (Zn‐heme). Measurements were conducted between 300 and 700 nm. In all cases the linear dichroism was wavelength dependent, indicating the presence of several transition moments with different orientations. We focused our attention on the near‐UV (300–380 nm) and Soret (380450 nm) absorption bands. Deconvolution in terms of Gaussian components gave three components between 380 and 450 nm and only one in the 300–380 nm region. Deconvolution of the near‐UV and Soret spectra of oxy‐, deoxy‐ and carbonmonoxyhemoglobin gave very similar results, suggesting a very similar orientation of the various transition moments in the free and protein‐embedded hemes. It should be stressed that the single 300–380 nm band is the only one responsible for the overlap integral that regulates the energy transfer from tryptophan to heme in hemoproteins (Gryczynski et al., Biophys. J. 63, 648–653, 1992). The dichroism of this single band indicated that its transition moment is oriented at about 60 from the α‐γ meso‐axis of the heme moiety. We conclude that the heme should be considered a linear oscillator when it acts as acceptor of energy transfer from tryptophans.
AB - We measured the linear dichroism of several metalloporphyrins embedded in stretched polyvinyl alcohol (PVA) films to estimate the orientation of the absorption transition moments, which in hemoproteins are relevant to the radiationless energy transfer between tryptophan and heme. The metalloporphyrins were derivatives of protoporphyrin IX (PPIX), namely Fe3+‐PPIX (ferric‐heme) and Fe2+CO‐PPIX (CO‐heme), Mg‐PPIX (Mg‐heme) and Zn‐PPIX (Zn‐heme). Measurements were conducted between 300 and 700 nm. In all cases the linear dichroism was wavelength dependent, indicating the presence of several transition moments with different orientations. We focused our attention on the near‐UV (300–380 nm) and Soret (380450 nm) absorption bands. Deconvolution in terms of Gaussian components gave three components between 380 and 450 nm and only one in the 300–380 nm region. Deconvolution of the near‐UV and Soret spectra of oxy‐, deoxy‐ and carbonmonoxyhemoglobin gave very similar results, suggesting a very similar orientation of the various transition moments in the free and protein‐embedded hemes. It should be stressed that the single 300–380 nm band is the only one responsible for the overlap integral that regulates the energy transfer from tryptophan to heme in hemoproteins (Gryczynski et al., Biophys. J. 63, 648–653, 1992). The dichroism of this single band indicated that its transition moment is oriented at about 60 from the α‐γ meso‐axis of the heme moiety. We conclude that the heme should be considered a linear oscillator when it acts as acceptor of energy transfer from tryptophans.
UR - http://www.scopus.com/inward/record.url?scp=0027674726&partnerID=8YFLogxK
U2 - 10.1111/j.1751-1097.1993.tb04920.x
DO - 10.1111/j.1751-1097.1993.tb04920.x
M3 - Article
C2 - 8248322
AN - SCOPUS:0027674726
VL - 58
SP - 492
EP - 498
JO - Photochemistry and Photobiology
JF - Photochemistry and Photobiology
SN - 0031-8655
IS - 4
ER -