Evidence for damped hemoglobin dynamics in a room temperature trehalose glass

David S. Gottfried, Eric S. Peterson, Asim G. Sheikh, Jiaqian Wang, Ming Yang, Joel M. Friedman

Research output: Contribution to journalArticle

108 Scopus citations

Abstract

Upon photodissociation of its ligand, COHbA exhibits a wide range of nonequilibrium relaxation phenomena that start within a fraction of a picosecond and extend out to tens of microseconds. In addition, equilibrium fluctuations of the protein result in conformational averaging. All of these dynamics can have an impact on ligand rebinding. In an effort to better understand the relationship between conformational dynamics and ligand-binding reactivity, COHbA was embedded in a room temperature trehalose sugar glass (Hagen et al. Science 1995, 269, 959) in order to uncouple solvent motions from protein dynamics as well as reduce the amplitude of large-scale protein conformational fluctuations. Time-resolved resonance Raman spectroscopy and ligand-rebinding kinetics show that the trehalose glass does not impede the initial fast relaxation of the iron-histidine linkage, but does dramatically impede conformational averaging and completely eliminates ligand escape at all temperatures from 140 K to room temperature. Fluorescence measurements indicate that in the trehalose glass the picosecond tryptophan lifetimes are nearly unchanged, but there is a complete absence of the nanosecond fluorescence decay (observed in aqueous solutions), which is replaced by a decay of ∼700 ps. This change in the fluorescence decay is ascribed to a significant decrease in the structural dynamics that normally allow transient opening of the distal heme pocket.

Original languageEnglish (US)
Pages (from-to)12034-12042
Number of pages9
JournalJournal of physical chemistry
Volume100
Issue number29
DOIs
StatePublished - Jul 18 1996

ASJC Scopus subject areas

  • Engineering(all)
  • Physical and Theoretical Chemistry

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