Indian Institute of Technology(Delhi), India
Meghna Sheoran has received her Master’s degree in Chemical Engineering from National Institute of Technology, Rourkela and she is a PhD student in Dr. Sudip K. Pattanayek’s group. Her PhD work focuses on adsorption of proteins at interfaces.
The structural stability of a protein is important for its biological function and activity. Various environmental factors such as temperature, salt, pH and additives are responsible for the structural stability of proteins. Various researchers have found the effect of various ions on the structural stability of various proteins and have proposed a “Hofmeister series”. It is also found that the cations and anions can affect the surface tension of the protein solution. Thus properties of protein due to presence of salt can affect both the solution and the interface properties. Myoglobin, a globular low molecular weight protein (Mol. Wt. 17,800 Da and isoelectric point 7.4) is found to increase in blood due to myocardial damage. So, scientists have started working on Myoglobin as a biomarker to detect the disease. We have investigated the effect of different salts (NH4)2SO4, Na2SO4, NaCl, MgCl2, NH4Cl, Na2HPO4 on solution properties and interfacial properties of myoglobin. We have measured interfacial tension and interfacial rheology near air by using oscillatory deformed drop module of Tensiometer. In addition, we have studied thermodynamic effects of salts on protein. We observed that the equilibrium surface tension effects are in correspondence with the Hofmeister series. Increase in ionic strength tends to lower the surface tension as more molecules will come to the surface. Higher surface tension values are observed with kosmotropic salts such as (NH4)2SO4. Chaotropic salts as Na2HPO4 has lower surface tension value. As frequency is increased, the interfacial tension value decrease and elastic modulus increases. The conformational changes of protein structure in presence of salts were determined using Fourier Transform Infrared Spectroscopy. These results show that a combination of surface and thermodynamic properties is useful in studying the influence of salts on properties of proteins.