Fluorescence intensity and anisotropy decays of the intrinsic tryptophan emission of hemoglobin measured with a 10-GHz fluorometer using front-face geometry on a free liquid surface

E. Bucci, Zygmunt Gryczynski, C. Fronticelli, Ignacy Gryczynski, J. R. Lakowicz

Research output: Contribution to journalArticle

10 Scopus citations

Abstract

We measured the intensity and anisotropy decays of the intrinsic tryptophan emission from hemoglobin solutions obtained using a 10-GHz frequency-domain fluorometer and a specially designed cuvette which allows front-face excitation on a free liquid surface. The cuvette eliminates reflections and stray emissions, which become significant for low-intensity fluorescence such as in hemoglobin. Three lifetimes are detectable in the subnanosecond range. The average lifetime of hemoglobin emission is ligand dependent. The measured values of average lifetimes are 91, 174, and 184 ps for deoxy-, oxy-, and carboxyhemoglobin, respectively. Fluorescence anisotropy decays of oxy-, deoxy-, and carbonmonoxyhemoglobin can be fitted with up to three correlation times. When three components are used, the floating initial anisotropy ro is, in each case, higher than the steady-state anisotropy of tryptophan in vitrified solution. For deoxy hemoglobin it is close to 0.4. The data are consistent with an initial loss of anisotropy from 0.4 to about 0.3 occurring in the first 2 ps.

Original languageEnglish
Pages (from-to)29-36
Number of pages8
JournalJournal of Fluorescence
Volume2
Issue number1
DOIs
StatePublished - 1 Mar 1992

Keywords

  • Fluorescence intensity decay
  • fluorescence anisotropy decay
  • free liquid surface
  • front-face geometry
  • hemoglobin
  • tryptophan emission

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