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Biochemistry 1988, 27, 3507-351 1 3507 Reactive Line-Shape Narrowing in Low-Temperature Inhomogeneous Geminate
 

Summary: Biochemistry 1988, 27, 3507-351 1 3507
Reactive Line-Shape Narrowing in Low-Temperature Inhomogeneous Geminate
Recombination of CO to Myoglobin
Noam Agmon*
Department of Physical Chemistry, The Hebrew University, Jerusalem 91904, Israel
Received October 8, 1987; Revised Manuscript Received January 11, 1988
ABSTRACT: The temporal shift in the near-IR absorption peak of myoglobin (Mb) following flash photolysis
of MbCO at cryogenic temperatures appears to be due largely to an inhomogeneous reactive process rather
than to relaxation. This conclusion, which follows from a new analysis of the experimental data, is based
on the following three points: First, at very low temperatures (60 K) a transient line-narrowing effect can
be detected. Second, there is a universal, temperature-independent, correlation between spectral shift and
survival probability in the rebinding kinetics, and third, the same quantitative model which accounts for
rebinding accounts semiquantitatively for the temporal shift in the peak. A fit to the model indicates that
the inhomogeneous broadening of the near-IR peak in myoglobin is 15-20% of the total width. The same
rebinding process which governs the loss of intensity of this peak is therefore most likely responsible for
the shift in its center wavelength.
r e low-temperature rebinding kinetics of CO and O2to
myoglobin (Mb) has been studied in detail over wide tem-
perature and time domains (Austin et al., 1975). By moni-
toring the Soret absorption subsequent to laser-pulse photolysis

  

Source: Agmon, Noam - Institute of Chemistry, Hebrew University of Jerusalem

 

Collections: Chemistry