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Proceedings Paper

Effect of disordered hemes and dimerization in isolated <greek>a-subunits of hemoglobin detected by time-resolved fluorescence spectroscopy in the picosecond range
Author(s): Zygmunt Gryczynski; Clara Fronticelli; Enrico Gratton; Jacek Lubkowski; Enrico Bucci
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Paper Abstract

Our recent linear dichroism study of transition moment directions for protoporphyrin derivatives [1,2] demonstrate that heme cannot be considered a planar oscillator when it acts as an acceptor of radiationless excitation energy transfer from tryptophan. The linear nature of the heme absorption transition moment implies a strong dependence of the transfer rate factors on the relative angular position of the heme and tryptophan, i.e. on the k2 orientation parameter of the Forster equation. Using the atomic coordinates of human hemoglobin and taking into account the direction of the transition moment of the near UV (300-380 nm) heme absorption band we have estimated the rate of energy transfer from tryptophan to heme in the isolated a chains, which are a single tryptophan protein. It appears that the rate of energy transfer is very sensitive to the orientation of the transition moment of the heme and similarly to myoglobin [3] natural heme disorder significantly reduces the transfer efficiency in isolated a subunits. On this basis we were able to predict very accurately the two lifetimes detectable in the systems, of 32 and 1050 ps respectively, where the amplitude of the longer lifetime is very consistent with the amount of disordered hemes found by La Mar [4,5] for the a subunits of hemoglobin.

Paper Details

Date Published: 17 August 1994
PDF: 6 pages
Proc. SPIE 2137, Time-Resolved Laser Spectroscopy in Biochemistry IV, (17 August 1994); doi: 10.1117/12.182718
Show Author Affiliations
Zygmunt Gryczynski, Univ. of Maryland/Baltimore School of Medicine (United States)
Clara Fronticelli, Univ. of Maryland/Baltimore School of Medicine (United States)
Enrico Gratton, Univ. of Illinois/Urbana-Champaign (United States)
Jacek Lubkowski, Univ. of Gdansk (Poland)
Enrico Bucci, Univ. of Maryland/Baltimore School of Medicine (United States)


Published in SPIE Proceedings Vol. 2137:
Time-Resolved Laser Spectroscopy in Biochemistry IV
Joseph R. Lakowicz, Editor(s)

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