Browsing by Author "Prakash Prabhu, N."

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    Determinants for macromolecular crowding-induced thermodynamic stabilization of acid-denatured cytochrome c to molten globules
    (Elsevier B.V., 2023-07-22T00:00:00) Kumari, Beeta; Shabnam; Yadav, Manisha; Kumar, Manoj; Kushwaha, Pratibha; Prakash Prabhu, N.; Kumar, Rajesh
    The macromolecular crowding effect transforms the acid-denatured ferricytochrome c (cyt cIII) (UA-state) to molten-globule (MGMC-state) at pH 1.85. Crowding-induced stabilization free energy (??G) and preferential hydration ??W were estimated for the UA ? MGMC transition. The magnitudes of ??G and ??W were found to be decreased as dextran 70 (D70) > dextran 40 (D40) > ficoll 70 (F70), which demonstrates that ??G and ??W track the molecular size and shape of the crowder towards refolding and stabilization of UA-state to MGMC-state. Analysis of effects of crowders (D40, D70, F70) on thermal and chemical-denaturations of acid-denatured cyt cIII provided several important information, (i) macromolecular crowding increased the thermodynamic stability of acid-denatured cyt cIII, (ii) concentration, size and shape of crowder control the crowding-induced thermodynamic stabilization of MGMC-state, (iii) crowding effect increased the thermal-denaturation midpoint (Tm) with a slight change in enthalpy (?Hm), suggesting that the steric-excluded volume effect contributes to the crowding-induced increased thermal stability of the acid-denatured protein. Analysis of entropy ? enthalpy plots for D40, D70, and F70 reveals that in addition to the steric-excluded volume effect, the enthalpic contribution is also added to the macromolecular crowding-induced stabilization of acid-denatured cyt cIII. The dilute-medium, compound-crowder, purely entropic-crowder and purely enthalpic-crowder curves were obtained for acid-denatured cyt cIII for D70, D40 and F70. The crossover temperature, Tx was calculated from the dilute and compound-crowder curves. The Tx values measured for D40, D70, and F70 were found to be ? 250.15 K, 272.15 K, and 275.15 K, respectively, which suggests that the Tx value depends on the size and shape of the crowder. Furthermore, the observation of a lower value of Tx and a minor enthalpic component for D40, D70, and F70 is likely due to the formation of weaker soft interactions of acid-denatured cyt cIII with D40, D70, and F70. � 2023 Elsevier B.V.