Spectroscopic Studies of Interactions of Some Biologically Important Small Molecules with Proteins
Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms and participate virtually in every process within cells. The work is based on studies of the interactions of erythroid membrane skeletal protein, Spectrin and Hb along with serum protein from human (HSA) and from bovine (BSA) and another soluble protein of non-erythroid origin, the lysozyme (Lyz) with small organic molecules like the phosphate metabolite ATP, hemin and other small molecules of therapeutic importance e.g. 4-Nitroquinoline (4NQO), Merocyanine 540 (MC 540) and Imatinib mesylate. To study these interactions we have been using spectroscopic tools like absorption, fluorescence, circular dichroism, synchronous fluorescence, time-resolved fluorescence and theoretical modelling.
SAs are the most important studied proteins in this field but the structural comparison between HSA and BSA was not studied previously. This aspect has been highlighted in this thesis while discussing the interactions of MC 540 with both HSA and BSA. The discrepancies between the spectroscopic data obtained with HSA and BSA while interacting with MC 540 depict that although both the SAs have 80% structural similarities but the conformational flexibility is greater in HSA than that of BSA that has further been confirmed by the results obtained from time-resolved fluorescence and induced CD experiments.
The Hb is the most studied blood protein and its structural changes have strong impact on blood-related or hematological diseases. In case of thalassemia, the prosthetic heme group of Hb is sometimes displaced from heme pocket. This type of phenomenon of heme loss could be stimulated in acidic pH. In erythrocyte cells, the membrane contains different types of phospholipids and cholesterol. Therefore, a detailed discussion on the impact of phospholipids on Hb has been done in my Ph. D. work. The heme loss and the release of oxygen from Hb occur simultaneously. The oxygen affinity of Hb decreases, in some diseased conditions as well as due to interaction with ATP. This aspect has been studied in detail by the spectroscopic techniques. Besides Hb, the Spectrin is also an erythrocyte membrane skeletal protein. The interaction of Spectrin with different phospholipids and drugs were studied previously. Here we have reported our findings regarding the interactions between Spectrin and an antileukemic drug, Imatinib as well as between Spectrin and another antileukemic as well as good fluorescent molecule, MC 540.