Hydrophilic ether-modified carboxybetaines: a molecular design approach for enzyme activation and stabilization

Abstract This study examines the impact of ether moieties on the properties of betaine derivatives, focusing on solubility, hydration, and effects on enzyme activity and stability. Alkoxybetaines were synthesized by adding ether groups to the alkyl chains of conventional alkylbetaines. Their physicochemical behavior was compared using dynamic light scattering (DLS), osmolarity measurements, water density analysis, and enzymatic assays with α-glucosidase. Alkoxybetaines showed greatly enhanced aqueous solubility over their alkyl counterparts. Enzyme activation assays showed that ether moieties preserved the activating ability of betaines while improving solubility. Introducing ether groups internally caused minimal disruption of the activation mechanisms. Hydration studies showed alkoxybetaines form compact yet highly hydrated shells, with lower DLS-measured particle sizes, higher osmolarity, and increased water density. These traits correlated with improved enzyme stabilization under heat and dilution. BO4 maintained over 98% residual activity after 51 d at 37 °C and enabled full enzymatic function at one-hundredth the concentration needed in controls. These results clarify the relationship between ether modification and hydration-mediated stabilization, offering a strategy for designing betaine-based additives with high solubility, enzyme activation, and long-term stability for enzyme preservation, diagnostics, and biocatalytic formulations.