Effect of Size of Crowder on Protein Stabilization

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 of two model proteins using UV-Vis spectroscopy. We
observed that the extent of stabilization of α-lactalbumin and lysozyme increases with the increasing
concentration of the crowding agents due to the excluded volume effect and the small-sized and rodshaped
crowder, i.e., dextran 40 resulted in greater stabilization of both proteins than dextran 70 and
ficoll 70. Since different osmolytes have functional and structural consequence on IDPs, they may
assist in enhancing the disease pathology of various human diseases (such as amyloidosis,
neurodegeneration, cancer, and diabetes), with the aggregation of IDPs as the common hallmark.
Hence, the crowders (polymers of sugar osmolytes) used in our study may have clinical implications
for diseases including IDPs.