Rates of energy transfer between tryptophans and hemes in hemoglobin, assuming that the heme is a planar oscillator

Z. Gryczynski, T. Tenenholz, E. Bucci

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Using the Förster equations we have estimated the rate of energy transfer from tryptophans to hemes in hemoglobin. Assuming an isotropic distribution of the transition moments of the heme in the plane of the porphyrin, we computed the orientation factors and the consequent transfer rates from the crystallographic coordinates of human oxy- and deoxy-hemoglobin. It appears that the orientation factors do not play a limiting role in regulating the energy transfer and that the rates are controlled almost exclusively by the intrasubunit separations between tryptophans and hemes. In intact hemoglobin tetramers the intrasubunit separations are such as to reduce lifetimes to 5 and 15 ps/ns of tryptophan lifetime. Lifetimes of several hundred picoseconds would be allowed by the intersubunit separations, but intersubunits transfer becomes important only when one heme per tetramer is absent or does not accept transfer. If more than one heme per tetramer is absent lifetimes of more than 1 ns would appear.

Original languageEnglish
Pages (from-to)648-653
Number of pages6
JournalBiophysical Journal
Volume63
Issue number3
DOIs
StatePublished - 1 Jan 1992

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Energy Transfer
Heme
Tryptophan
Hemoglobins
Transfer Factor
Porphyrins

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Rates of energy transfer between tryptophans and hemes in hemoglobin, assuming that the heme is a planar oscillator. / Gryczynski, Z.; Tenenholz, T.; Bucci, E.

In: Biophysical Journal, Vol. 63, No. 3, 01.01.1992, p. 648-653.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Rates of energy transfer between tryptophans and hemes in hemoglobin, assuming that the heme is a planar oscillator

AU - Gryczynski, Z.

AU - Tenenholz, T.

AU - Bucci, E.

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N2 - Using the Förster equations we have estimated the rate of energy transfer from tryptophans to hemes in hemoglobin. Assuming an isotropic distribution of the transition moments of the heme in the plane of the porphyrin, we computed the orientation factors and the consequent transfer rates from the crystallographic coordinates of human oxy- and deoxy-hemoglobin. It appears that the orientation factors do not play a limiting role in regulating the energy transfer and that the rates are controlled almost exclusively by the intrasubunit separations between tryptophans and hemes. In intact hemoglobin tetramers the intrasubunit separations are such as to reduce lifetimes to 5 and 15 ps/ns of tryptophan lifetime. Lifetimes of several hundred picoseconds would be allowed by the intersubunit separations, but intersubunits transfer becomes important only when one heme per tetramer is absent or does not accept transfer. If more than one heme per tetramer is absent lifetimes of more than 1 ns would appear.

AB - Using the Förster equations we have estimated the rate of energy transfer from tryptophans to hemes in hemoglobin. Assuming an isotropic distribution of the transition moments of the heme in the plane of the porphyrin, we computed the orientation factors and the consequent transfer rates from the crystallographic coordinates of human oxy- and deoxy-hemoglobin. It appears that the orientation factors do not play a limiting role in regulating the energy transfer and that the rates are controlled almost exclusively by the intrasubunit separations between tryptophans and hemes. In intact hemoglobin tetramers the intrasubunit separations are such as to reduce lifetimes to 5 and 15 ps/ns of tryptophan lifetime. Lifetimes of several hundred picoseconds would be allowed by the intersubunit separations, but intersubunits transfer becomes important only when one heme per tetramer is absent or does not accept transfer. If more than one heme per tetramer is absent lifetimes of more than 1 ns would appear.

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