Stability of Proteins Inside a Hydrophobic Cavity

Abstract

We study the effects of confinement and hydrophobicity of a spherical cavity on the structural and thermal stability of proteins in the framework of a hydrophobic-polar (HP) lattice model. We observe that a neutral confinement stabilizes the folded state of the protein by eliminating many of the open-chain conformations of the unfolded state. Hydrophobic confinement always destabilizes the protein because of protein-surface interactions. However, for moderate surface hydrophobicities, the protein remains stabilized relative to its state in free solution because of the dominance of entropic effects. These results are consistent with our experimental findings of (a) enhanced activity of alcohol dehydrogenase (ADH) when immobilized inside the essentially cylindrical pores of hydrophilic mesoporous silica (SBA-15) and (b) unaffected activity when immobilized inside weakly hydrophobic pores of methacrylate resin compared to its activity in free solution. In the same vein, our predictions are also consistent with the behavior of lysozyme and myoglobin in hydrophilic and hydrophobic SBA-15, which show qualitatively the same trends. Apparently, our results have validity across these very different enzymes, and we therefore suggest that confinement can be used to selectively improve enzyme performance.

Engineering aspects of immobilized lipases on esterification: A special emphasis of crowding, confinement and diffusion effects

“…Radhakrishna et al. 2013 reported the influence of crowding and confinement conditions for higher activities associated with the immobilized alcohol dehydrogenase (ADH) in SBA‐15. However in case of CLEC, the enzyme stability is mainly dependent on the crosslinking efficiency, internal mass‐transfer resistance and crowding and confinement environment created by modification of essential amino groups by the cross linking agents such as glutaraldehyde .…”

Packaging biological cargoes in mesoporous materials: opportunities for drug delivery

“…Also using activity as a gauge for stability, Radhakrishna et al . [69] found that immobilisation on the internal surface of SBA-15 increases the activity and stability of alcohol dehydrogenase. Using computational methods it was determined that the elimination of possible open-chain conformations provides entropic effects enhancing the observed increased stabilisation.…”

Towards efficient chemical synthesis via engineering enzyme catalysis in biomimetic nanoreactors

“…Another point worthy of note is that the moderate hydrophobic nanopores are more favorable to the thermal stability of immobilized PCL than the hydrophilic and strong hydrophobic nanopores. 41 They proposed that the surface hydrophobicity of nanopores plays a non-monotonic role in affecting the stability of these immobilized enzymes. 40 Similar trends were observed for alcohol dehydrogenase, lysozyme and myoglobin according to a new study by Belfort and Kumar.…”

“…41,57,58 This benefits from the restricted space endowed by the fitted nanopores, which can eliminate many of the open-chain conformations of enzyme under adverse conditions. A general conception deriving from massive experimental and theoretical investigations is that a pore size only slightly larger than the enzyme dimensions can effectively improve the enzyme stability against heat and harmful reagents.…”