Dynamics and protein–solvent interactions of hemoglobin in T and R quaternary conformation

Article type: Research Article

Authors: Caronna, Chiara | Cupane, Antonio

Affiliations: Istituto Nazionale per la Fisica della Materia (INFM) and Dipartimento di Scienze Fisiche ed Astronomiche (DSFA), University of Palermo, via Archirafi, 36, I‐90123 Palermo, Italy

Note: [] Corresponding author: Dr. Antonio Cupane, Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo, via Archirafi 36, I‐90123, Palermo, Italy. Tel.: +39 091 6234221; Fax: +39 091 6162461; E‐mail: [email protected].

Abstract: In this work we report the thermal behaviour of the amide I′ band of carbonmonoxy and deoxy hemoglobin in 65% v/v glycerolD8/D2O solutions and in the temperature interval 10–295 K. Following recent suggestions in the literature, we analyze the amide I′ band in terms of two components, one at about 1630 cm−1 and the other at about 1650 cm−1, that are assigned to solvent‐exposed and buried α‐helical regions, respectively. For deoxy hemoglobin (in T quaternary structure) both components are narrower with respect to carbonmonoxy hemoglobin (in R quaternary structure), while the peak frequency blue shift observed, upon increasing temperature, for the component at about 1630 cm−1 is smaller. The reported data provide evidence of the dependence of hemoglobin dynamic properties upon the protein quaternary structure and suggest a more compact α‐helical structure of hemoglobin in T conformation, with reduced population of low‐frequency modes involving the solvent and protein.

Journal: Spectroscopy, vol. 16, no. 3-4, pp. 227-233, 2002