Effect of disordered hemes and dimerization in isolated <greek>a-subunits of hemoglobin detected by time-resolved fluorescence spectroscopy in the picosecond range

Zygmunt Gryczynski; Clara Fronticelli; Enrico Gratton; Jacek Lubkowski; Enrico Bucci

doi:10.1117/12.182718

17 August 1994 Effect of disordered hemes and dimerization in isolated <greek>a-subunits of hemoglobin detected by time-resolved fluorescence spectroscopy in the picosecond range

Zygmunt Gryczynski, Clara Fronticelli, Enrico Gratton, Jacek Lubkowski, Enrico Bucci

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Proceedings Volume 2137, Time-Resolved Laser Spectroscopy in Biochemistry IV; (1994) https://doi.org/10.1117/12.182718
Event: OE/LASE '94, 1994, Los Angeles, CA, United States

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.

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Zygmunt Gryczynski, Clara Fronticelli, Enrico Gratton, Jacek Lubkowski, and Enrico Bucci "Effect of disordered hemes and dimerization in isolated <greek>a-subunits of hemoglobin detected by time-resolved fluorescence spectroscopy in the picosecond range", Proc. SPIE 2137, Time-Resolved Laser Spectroscopy in Biochemistry IV, (17 August 1994); https://doi.org/10.1117/12.182718

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KEYWORDS

Energy transfer

Absorption

Proteins

Picosecond phenomena

Near ultraviolet

Dichroic materials

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