Dynamical Transition in Dehydrated Proteins

Abstract

Terahertz time-domain spectroscopy and differential scanning calorimetry were used to study the role of the dynamics of biomolecules decoupled from solvent effects. Lyophilized sucrose exhibited steadily increasing absorption with temperature as anharmonic excitations commenced as the system emerged from a deep minimum of the potential energy landscape where harmonic vibrations dominate. The polypeptide bacitracin and two globular proteins, lysozyme and human serum albumin, showed a more complex temperature dependence. Further analysis focused on the spectral signature below and above the boson peak. We found evidence of the onset of anharmonic motions that are characteristic for partial unfolding and molecular jamming in the dry biomolecules. The activation of modes of the protein molecules at temperatures comparable to the protein dynamical transition temperature was observed in the absence of hydration. No evidence of Froḧlich coherence, postulated to facilitate biological function, was found in our experiments.

Anti-plasticizing effect of water on prilocaine and lidocaine – the role of the hydrogen bonding pattern

“…44 The strong interactions between plasticizers and amorphous drugs can break the original intra- and inter-molecular network of the anhydrous drugs, leading to an increase in molecular mobility and a subsequent decrease in the T g s of the drugs. 45 However, it has been shown that intermolecular interactions with water can also reduce the potential energy barrier of some macromolecules more effectively than sterically hindered intramolecular interactions, 46,47 and thus may show an anti-plasticizing effect of water. In addition, Wang et al have reported an anti-plasticizing effect of urea/water mixtures on starch molecules.…”