Compatible osmolytes - bioprotectants: Is there a common link between their hydration and their protective action under abiotic stresses?

Compatible osmolytes accumulate in the cell cytoplasm in order to protect the structure of proteins and enzymes under abiotic stresses. It is assumed that the osmolyte hydration is playing an important role in their protective mechanism. However, the details of osmolyte interactions with water surroundings are far from being fully understood. This contribution summarizes our recent published data on the hydration structure of a set of compatible osmolytes such as glycine, TMAO, proline, ectoine, glycine betaine under the effect of concentration, temperature, pressure, and salt addition. As it follows from the discussed data, under these factors the molecules in question are strongly hydrated, that is an evidence for their strong ability to bind a significant amount of water and, thus, is a confirmation for their stabilizing effect on proteins via an indirect mechanism. Moreover, the salt additions stimulate a cooperative binding between the charged groups of osmolytes and inorganic ions as a result of ion-specific interactions. A link between the hydration features as well as the ion-binding of osmolytes and their biological role is given. (C) 2019 Elsevier B.V. All rights reserved.