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Hannover 2013 – scientific programme

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MO: Fachverband Molekülphysik

MO 19: Poster 2: Biomolecules, Cold Molecules, Experimental Techniques, Various Topics

MO 19.22: Poster

Wednesday, March 20, 2013, 16:00–18:30, Empore Lichthof

Role of hydration on the functionality of a proteolytic enzyme α-chymotrypsin under crowded environment — •Pramod Verma1, Rajib Mitra2, and Samir Pal21Institut für Physikalische und Theoretische Chemie, Lehrstuhl 1, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany — 2CBMS Department, S.N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700098, India

In the present contribution, the role of hydration on the functionality of a proteolytic enzyme α-chymotrypsin (CHT) is investigated by modulating the water activity with the addition of polyethylene glycols (PEG;average molecular weight=400). The addition of PEG increases the affnity of the enzyme to its substrate, however, followed by a decrease in the turnover number. Energetic calculations show that entrance path for the substrate is favoured, whereas the exit channel is restricted with increasing concentration of the crowding agent. This decrease is attributed to the thinning of the hydration shell of the enzyme due to the loss of critical water residues from the hydration surface of the enzyme. The overall secondary and tertiary structures of CHT determined from far-UV and near-UV circular dichroism measurements show no considerable change in the studied osmotic stress range. Spectroscopic observation of water relaxation and rotational dynamics of ANS-CHT complex at various concentrations of the osmoting agent support the dehydration of the hydration layer. Such dehydration/hydration processes during turnover imply a significant contribution of solvation to the energetics of the conformational changes.

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