WFU Physics Colloquium

TITLE: N CO partial pressure dependence of the kinetics of melting of HbS aggregates studied in high concentration phosphate buffer

SPEAKER: Svetlana Aroutiounian,

Department of Physics
Wake Forest University

TIME: Thursday Oct. 17, 2002 at 4 PM

PLACE: George P. Williams, Jr. Lecture Hall, (Olin 101)

Refreshments will be served at 3:30 PM in the lounge. All interested persons are cordially invited to attend.

ABSTRACT

(Practice talk for SESAPS meeting.) Deoxygenated sickle cell hemoglobin (HbS) monomers enter the polymer phase either by incorporation into a critical nucleus, through heterogeneous nucleation and or through linear growth of the polymers when the concentration of monomers exceeds the solubility. CO-bound, R-state HbS monomers do not polymerize. Thus, polymer melting is enhanced by binding of carbon monoxide (CO) to HbS polymerized monomers. In our study, the melting of HbS aggregates mediated by dilution and CO binding to polymerized monomers is observed with the time-resolved extinction spectroscopy. The CO partial pressure (pCO) dependence of the kinetics of melting is studied for pCO=0.23, 0.45, 0.68, 0.91 atm with difference progress curves. Progress curves at isosbestic wavelength are shown to be a good model for melting kinetics of CO-ligated HbS monomers. A considerable spread near the pCO=0.45 along with striking similarity near pCO=0.23atm of the relaxation times indicates a presence of the threshold pCO. Near linear power law observed above the threshold pCO is due to non-cooperative CO binding. Considerable slowing down of the kinetics of melting due to gelation is observed in sample stability measurements. As possible mechanism for threshold pCO and linear power low above it the fractional percolation threshold is discussed.

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