Urea is a widely employed denaturation agent for numerous macromolecules in aqueous solutions. To date, significant effort has been focused on exploring the molecular level mechanisms behind its universal denaturation power. Various molecular mechanisms have been proposed including direct urea-macromolecule interactions and entropically driven ones. To elucidate the dominant contribution to universal urea denaturation power, we performed macromolecule solubility and vibrational spectroscopy measurements. The solubility of poly(N-isopropyl acrylamide), and poly(N, N-dimethyl acrylamide) is systematically probed in the presence of urea, 1, 3 dimethyl urea, and tetramethyl urea. We find that the macromolecule solubility increases as osmolyte concentration increases, except for PNIPAM in the presence of highly concentrated urea (> 3M) solution. The vibrational fingerprints of the osmolytes and macromolecules are probed that show both direct macromolecule-urea interactions along with presence of non-interacting osmolytes in the vicinity of the macromolecule surface. Both solubility and vibrational spectroscopy results correlate and give clues on dominant macromolecule – urea interactions. The results also indicate that although having very similar molecular structures, these two macromolecules act oppositely at least in the presence of highly concentrated urea solutions.

On the mechanism of macromolecule denaturation in aqueous urea solutions

ACS Spring Meeting 2021

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