Goldbeck R A, Sagle L, Kim-Shapiro D B, Flores V, Kliger D S
Department of Chemistry and Biochemistry, University of California, Santa Cruz 95064, USA.
Biochem Biophys Res Commun. 1997 Jun 27;235(3):610-4. doi: 10.1006/bbrc.1997.6845.
In order to study interdimer heme-heme electronic interactions in human hemoglobin, the Soret circular dichroism spectrum of the carboxy adduct is measured as a function of protein concentration, the spectrum at the highest concentration representing primarily that of alpha2beta2 tetramers (93%) and the lowest concentration representing primarily alphabeta dimers (68%). The tetramer-dimer difference spectrum, obtained using singular value decomposition and linear least squares fitting from a matrix of CD spectra measured at ten concentrations, is roughly conservative, with a larger negative lobe at shorter wavelengths and a peak-to-trough magnitude that is 18% of the tetramer's maximum Soret CD magnitude. It is tentatively assigned to heme-heme excitonic interactions on the basis of theoretical predictions by R. W. Woody [(1985) in Optical Properties and Structure of Tetrapyrroles (Blauer, G., and Sund, H., Eds.), pp. 239-256, Walter de Gruyter, New York].
