Mechanism Of The Hydration Dynamics Of Organic/Inorganic Osmolytes Based On The O:H—O Hydrogen Bond Cooperative Relaxation

Osmolytes are a class of substances which commonly exist in living organisms.They play an important role for mediating cell osmotic pressure and for affecting the structure and performance of protein.The interaction mechanism between osmolyte molecule and water molecules has always been a concern yet long-term doubtful challenge.In order to elucidate the mechanism of this interaction,this paper investigated the hydration effect of glycines and ureas organic osmolytes and inorganic osmolytes such as potassium chloride,potassium bromide,calcium chloride and calcium bromide.Based on the hydrogen bond relaxation model,our research made use of Raman spectroscopy,contact angle,viscosity and conductivity detection,while combined with differential phonon spectrometrics and a series of derivative analysis creatively.The effect of different osmotic solute on the differentiation of solvent O:H—O bond network was clarified by this work.The experimental results show that:(1)According to the observation of the O:H—O bond relaxation process and the further analysis,one found that the polarization effect of glycines and ureas molecules on solvent molecules causes the molecular dipolar electrical field,which sources from the asymmetrical distribution of the H~+and the“:”on the solute.This electrical field stiffens the H—O covalent bond which its frequency peak has the blue shift,while softens the O:H nonbond,leading to the red shift of the peak as well as the increasing of viscosity for solutions.Meanwhile,the H?H fragmentation which exists between hydrogen protons H~+and surrounding water molecules disrupts surface stress.The capacity of molecular polarization is enhanced with the increasing number of alkyl,and also the surface stress disruption and viscosity have the rising.(2)The ureas osmolytes has a weaker polarization effect than the glycines,but they have a relatively easy to form the hydrogen bond with the H—O dangling bond.The reason may be related to the fact that the distribution of lone pair electrons of ureas is relatively dispersed,and their molecular dipole moment is small,then their molecular dipole field is weak.The increasing number of alkyl is also enabled to improve the polarization effect of these molecules,leading to the dissipation for the surface tension and the enhancement for the viscosity.(3)For osmolytes of inorganic salts,their polarization effect on the surrounding water molecules mainly result from the electrical field of ions.Ionic polarization effect motivates the energy strengthening and length contraction of the segmental H—O covalent bond whilst the energy weakening and length elongation of the O:H nonbond.Besides,the ionic polarization also enhances the surface stress,conductivity and viscosity of solutions.Based on the analysis of differential phonon spectrometrics,we discriminated the polarization effect of anions and cations,and found that difference of the polarized capacity are related to the characteristics of various ions.The observation exhibits that the polarization capacity of anions is stronger than the case of cations,and this capacity of cation slightly enhances with the increasing ionic radius.Meanwhile,for different ions,the shielding effect caused by water molecules has different level.Moreover,there are significant differences reflected in the effects of monovalent and divalent salt ions on the hydrogen network.In addition to the difference of ions,the ionic concentration is an essential factor to impacting properties of solutions.