Department Of Chemistry

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Author: search.filters.author.Sharma, DeepakHas files: Yes

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    Single-molecule force-unfolding of titin I27 reveals a correlation between the size of the surrounding anions and its mechanical stability
    (Royal Societty of chemistry, 2018) Muddassir, Mohd; Manna, Bharat; Singh, Priyanka; Singh, Surjeet; Kumar,Rajesh; Ghosh, Amit; Sharma, Deepak
    Each cellular protein is surrounded by a biochemical milieu that affects its stability and the associated function. The role of this surrounding milieu in the proteins’ mechanical stability remains largely unexplored. Herein, we report an as yet unknown correlation between the size of the surrounding anions and the mechanical stability of a protein. Using single-molecule force spectroscopy of the 27th domain (I27) of human cardiac muscle protein titin, we show that the average unfolding force of the protein decreases with increase in the ionic radii of the surrounding anions in the order Cl− > Br− > NO3− > I− > SO42− ≈ ClO4−, indicating an inverse correlation between anion size and the mechanical stability of I27. The destabilizing effect was attributed to the combined effect of increase in the unfolding rate constant and unfolding distance upon incubation with the anion. These findings reveal that anion size can significantly affect the mechanical resistance of proteins and thus could be a convenient and promising tool for regulating the mechanical stability of proteins.
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    Role of Macromolecular Crowding on Stability and Iron Release Kinetics of Serum Transferrin
    (American Chemical Society, 2017) Kumar, Sandeep; Sharma, Deepak; Kumar, Rajesh
    The macromolecular crowding influences the structural stability and functional properties of transferrin (Tf). The equilibrium as well as kinetic studies of Tf at different concentrations of crowding agents (dextran 40, dextran 70, and ficoll 70) and at a fixed concentration of dextran 40 under different concentrations of NaCl at pH 7.4 and 5.6 (?1) revealed that (i) the crowder environment increases the diferric-Tf (Fe2Tf) stability against iron loss and overall denaturation of the protein, (ii) both in the absence and presence of crowder, the presence of salt promotes the loss of iron and overall denaturation of Fe2Tf which is due to ionic screening of electrostatic interactions, (iii) the crowder environment retards iron release from monoferric N-lobe of Tf (FeNTf) by increasing enthalpic barrier, (iv) the retardation of iron release by crowding is enthalpically dominated than the entropic one, (v) both in the absence and presence of crowder, the presence of salt accelerates the iron release from FeNTf due to ionic screening of electrostatic interactions and anion binding to KISAB sites, and (vi) the crowders environment is unable to diminish (a) the salt-induced destabilization of Fe2Tf against the loss of iron and overall denaturation and (b) the anion effect and ionic screening of diffusive counterions responsible to promote iron release from FeNTf. ? 2017 American Chemical Society.