By Nnolim, Nonso Emmanuel
Crude haemoglobins were extracted from blood samples of identified individuals of normal (AA), sickle trait carrier (AS), and sickle (SS) by employing centrifugation techniques. The crude haemoglobins were dialysed at 4oC for 12hr against 50mM Tris-HCl buffer of pH 7.2. The effects of pyrimethamine and sulphadoxine on the haemoglobins in the presence and absence of sodium dodecyl sulphate (SDS) were studied at pH 5.0 and 7.2 with uv-visible titration spectrophotometry. The study showed that sodium dodecyl sulphate at pH 5.0 unfolded the studied proteins. These can be related to destabilization of haemoglobin structure by proteases such as plasmepsins and falcipains in the acidic environment of malaria parasite food vacuole due to malaria parasite infection. Pyrimethamine and sulphadoxine at pH 5.0 and 7.2 decreased the concentration of oxyhaemoglobin and increased the concentrations of methaemoglobin and deoxyhaemoglobin of the studied proteins. The results also show how haemoglobins are deoxygenated due to interaction with sodium dodecyl sulphate. Deoxygenation of haemoglobin as a result of their interaction with SDS can be likened to pathological condition whereby malaria parasites infection reduced the oxygen tension of erythrocytes of their host. HbS had the highest interaction with sulphadoxine and pyrimethamine followed by HbAS while HbA had the least interaction. Formation of methaemoglobin is associated with lipid oxidation. Increase in absorbance at 275 nm observed in this study refers to dynamic motion of the studied proteins and their deviation from normal structure and function. The interaction of haemoglobins with sulphadoxine-pyrimethamine combination at pH 5.0 caused a large perturbation of the protein conformation that was reflected in modest spectral shift of the soret band.