Abstract
A central issue in the adaptation of proteins and enzymes to extreme conditions is the conservation of their functional state, which is characterized by a well-balanced compromise of stability and flexibility. In this review work an overview of elastic neutron scattering (ENS) findings on a class of bioprotectant glass-forming systems, such as trehalose and its homologous (maltose and sucrose) water mixtures, is presented as a function of temperature and concentration. ENS, in fact, allows to determine some remarkable quantities in order to characterize the correlation among dynamical properties, the flexibility and fragility of biomolecules. The experimental results have pointed out a dynamical transition, which shows a crossover in molecular fluctuations between harmonic and anharmonic dynamical regimes. The ENS findings allow to characterize both the trehalose rigidity and flexibility, which are strictly connected to its superior bioprotective effectiveness. In this frame the lowest flexibility and fragility character of trehalose/H2O mixture with respect to maltose and sucrose/H2O mixtures indicate a better attitude to encapsulate biostructures in more rigid and temperature insensitive structures in approaching the glass transition.
Highlights
A central issue in the adaptation of proteins and enzymes to extreme conditions is the conservation of their functional state, which is characterized by a well-balanced compromise of stability and flexibility
We focus the attention on the use of a sophisticated physical methodology, such as the elastic neutron scattering (ENS) to investigate the dynamical properties of trehalose, compared to its homologous disaccharides, maltose and sucrose, and a class of extremophiles
It is evident that a dynamical transition occurs for the three investigated systems; for the trehalose mixture at T ∼ 238 K, whereas for maltose and sucrose mixtures at T ∼ 235 K and T ∼ 233 K, respectively
Summary
In recent years a lot of attention has been addressed to the understanding of the mechanisms present in organisms able to survive under environmental stress conditions, that is, the extremophiles [1,2,3,4,5,6,7,8,9,10]. One of the most significant examples of the biological role of trehalose is represented by tardigrada, that, thanks to the disaccharide synthesis, are able to survive at temperatures near absolute zero and above the boiling point of water, pressure of 6000 atm, a hard vacuum (as in outer space), high doses of radiation, X-rays, nitric acid, hydrochloric acid, carbon dioxide, and carbon monoxide They can live more 125 years, alternating periods of active life and of cryptobiotic life [25]. In their work the orientational order parameter and the dynamical structure factor have been combined to differentiate the actions of trehalose, sucrose, and maltose They showed for trehalose a higher distortion of the hydrogen bonded network of water from its tetrahedrality and that the relaxation times of water in the presence of disaccharides result in 1.2 to 10 times longer than those of pure water; in addition, water in presence of trehalose shows the longest relaxation times [35]. The experimental findings allow to characterize both the trehalose rigidity and flexibility, which are strictly connected to its superior bioprotective effectiveness
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