%0 Journal Article
%A Yadav, Manisha
%A Muthusamy, Sureshan
%A Kadhirvel, Saraboji
%A Sharma, Deepak
%A Kumar, Rajesh
%D 2025
%F open:3289
%I American Chemical Society (ACS)
%J Biochemistry
%N 13
%P 2899-2915
%T Determining factors for spermidine-induced modulation of conformational stability and dynamics of horse myoglobin
%U http://crdd.osdd.net/open/3289/
%V 64
%X The present work describes how water-miscible natural polyamine (NPA) spermidine (SPD) alters the conformational stability and dynamics of horse myoglobin (h-Mb) at pH 7.4. Analysis of thermal- and chemical-induced unfolding profiles of h-Mb at different concentrations of SPD at pH 7.4 revealed that SPD (\geq5 mM) reduces the conformational stability of h-Mb. The effect of SPD was further corroborated using MD simulations, which showed that SPD (\geq5 mM) enhanced the conformational fluctuations and reduced the structural stability of h-Mb. The SPD concentration effect on the thermodynamic equilibria (KU) of h-Mb was translated to the changes in preferential interaction coefficient (ΔΓ23) and hydration number (ΔΓw). The finding of the positive value of ΔΓ23 and the negative value of ΔΓw suggests that the interaction of SPD with h-Mb and the exclusion of water from the protein reduce the conformational stability of h-Mb. Analysis of SPD effects on enthalpy-entropy plots and temperature dependence of unfolding free energy of h-Mb suggests that the SPD forms soft, attractive enthalpic interactions with h-Mb. Analysis of SPD impact on the urea-concentration-dependent thermal unfolding midpoint temperature showed that SPD exhibits an additive effect to the urea-mediated decrease in the thermal stability of h-Mb.