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European Biophysics Journal

, Volume 27, Issue 2, pp 113–125 | Cite as

From metmyoglobin to deoxy myoglobin: relaxations of an intermediate state

  • D. C. Lamb
  • Andreas Ostermann
  • Valeri E. Prusakov
  • F. G. Parak
ARTICLE

Abstract

Metmyoglobin has been reduced at low temperature (below 100 K) using x-rays or by excitation of tris(2,2′,bipyridine)ruthenium(II) chloride with visible light. Upon reduction, an intermediate state is formed where the structure of the protein is very similar to that of metmyoglobin with the water molecule still bound to the heme iron, but the iron is II low spin. The nature of the intermediate state has been investigated with optical spectroscopy. The Qo and Qv bands of the intermediate state are split, suggesting that the protoporphyrin is distorted. The intermediate state undergoes a relaxation observed by a shifting of the Soret band at temperatures above 80 K. Above 140 K, the protein begins to relax to the deoxy conformation. The relaxation kinetics of the protein have been monitored optically as a function of time and temperature from minutes to several hours and from 150 K to 190 K. By measuring the entire visible spectrum, we are able to distinguish between electron transfer processes and the protein relaxation from the intermediate state to deoxy myoglobin. The relaxation has been measured in both horse myoglobin and sperm whale myoglobin with the relaxation occurring on faster time scales in horse myoglobin. Both the reduction kinetics and the relaxation show non-exponential behavior. The reduction kinetics can be fit well to a stretched exponential. The structural relaxation from the intermediate state to the deoxy conformation shows a more complex, dynamical behavior and the reaction is most likely affected by the relaxation of the protein within the intermediate state.

Key words Myoglobin Protein dynamics Ru(2 2′ bipyridine) Intermediate states Photochemical reduction 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • D. C. Lamb
    • 1
  • Andreas Ostermann
    • 1
  • Valeri E. Prusakov
    • 2
  • F. G. Parak
    • 1
  1. 1.Fakultät für Physik E17, TU München, D-85747 Garching, Germany (Fax: +49-89-28912548)DE
  2. 2.Institute of Chemical Physics, Russian Academy of Science, Moscow, RussiaRU

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