Carbohydrate-Based Macromolecular Crowding-Induced Stabilization of Proteins: Towards Understanding the Significance of the Size of the Crowder

There are a large number of biomolecules that are accountable for the extremely crowded intracellular environment, which is totally different from the dilute solutions, i.e., the idealized conditions. Such crowded environment due to the presence of macromolecules of different sizes, shapes, and composition governs the level of crowding inside a cell. Thus, we investigated the effect of different sizes and shapes of crowders (ficoll 70, dextran 70, and dextran 40), which are polysaccharide in nature, on the thermodynamic stability, structure, and functional activity of two model proteins using UV-Vis spectroscopy and circular dichroism techniques. We observed that (a) the extent of stabilization of alpha-lactalbumin and lysozyme increases with the increasing concentration of the crowding agents due to the excluded volume effect and the small-sized and rod-shaped crowder, i.e., dextran 40 resulted in greater stabilization of both proteins than dextran 70 and ficoll 70; (b) structure of both the proteins remains unperturbed; and (c) enzymatic activity of lysozyme decreases with the increasing concentration of the crowder.