WFU Physics Colloquium

TITLE: Biophysical studies of potential therapies of hemoglobin-associated diseases

SPEAKER: Andrea Belanger

TIME: Thursday April 30, 2015 at 9:00 AM

PLACE: Room 101 Olin Physical Laboratory

Hemoglobin (Hb), the most abundant protein found in the red blood cell (RBC), carries gases like oxygen and carbon dioxide throughout the body. However, various conditions, both genetic and environmental, can impede its ability to perform this (and other) necessary functions. We studied some of the most imperative properties of Hb and the RBC as they pertain to sickle cell disease (SCD): oxygen affinity and RBC deformability. A Hemox Analyzer, a dual-wavelength spectrophotometer, was used to measure oxygen affinity in sRBC treated with a potential drug intended to reduce sickling and improve oxygen affinity. Deformability, the ability of the cells to elongate when exposed to shear, was measured as a function of osmotic pressure in a refurbished Technicon Ektacytometer. This characteristic of the cells is extremely important, especially in SCD, as rigid cells 1) are unable to traverse the narrow capillaries and 2) are more likely to get filtered out by the spleen prematurely, leading to severe anemia. The effects of nitric oxide (NO) and its cogeners were rigorously tested and were shown to improve deformability under specific conditions.

In addition to genetic abnormalities of Hb, alterations to the gaseous homeostasis of the body, such as the presence of carbon monoxide (CO), can lead to diminished Hb function and subsequent injury or even death. We used laser-assisted flash photolysis to measure the binding affinities of CO to Hb and a genetically modified neuroglobin (Ngb) that was designed to have a superphysiologically high affinity for ligands such as CO. We found that this mutated Ngb had a binding affinity for CO almost 500 times greater than that of Hb for CO, demonstrating its promising potential as an antidote for CO poisoning.

It is well understood that NO and nitrite play a major role in the modulation of blood flow and proper platelet function. Several proteins, including deoxygenated Hb, are capable of reducing nitrite to NO, however the mechanism by which this event occurs in vivo is still under much debate. We demonstrated that while several proteins are able to reduce nitrite to NO, the relatively high concentration of Hb in the vasculature casts doubt on the role other proteins play in nitrite bioactivation, at least by red blood cells.