posted on 2020-01-07, 21:10authored byNatasha
Lynn Smith, Andrew Eagle Coukouma, Ryan S. Jakubek, Sanford A. Asher
Responsive
pure protein organogel sensors and catalysts are fabricated
by replacing the aqueous mobile phase of protein hydrogels with pure
ethylene glycol (EG). Exchanging water for EG causes irreversible
volume phase transitions (VPT) in bovine serum albumin (BSA) polymers;
however, BSA hydrogel and organogel sensors show similar volume responses
to protein–ligand binding. This work elucidates the mechanisms
involved in this enabling irreversible VPT by examining the protein
secondary structure, hydration, and protein polymer morphology. Organogel
proteins retain their native activity because their secondary structure
and hydration shell are relatively unperturbed by the EG exchange.
Conversely, the decreasing solvent quality initiates polymer phase
separation to minimize the BSA polymer surface area exposed to EG,
thus decreasing distances between BSA polymer strands. These protein
polymer morphology changes promote interprotein interactions between
BSA polymer strands, which increase the effective polymer cross-link
density and prevent organogel swelling as the mobile phase is exchanged
back to water.