Experimentally Observed Glassy State

The life-time of the ionic intermediates in the liquid solutions is so short that it is difficult or impossible to observe them directly. One of the convenient ways to overcome this difficulty is to prolong the life-time by freezing the irradiated solution at low temperature. For convenience of measurement, organic substances frozen to a glassy state have been widely used as solvents for the study by means of optical absorption measurement at low temperature. A rigid glass matrix is preferably used also in the ESR study, because the experimental results are readily compared with those obtained by the optical study. 

The role of water in the conformation, the activity and the stability of proteins has been investigated with many experimental and theoretical approaches. Because of its importance it has been coined as the 21 amino acid . There is now sufficient experimental evidence for the fact that dry proteins do not unfold by increased temperature or pressure [21]. Low levels of hydration give rise to a glassy state and the temperature of the glass transition depends on the amount of water as observed for synthetic polymers. Water can therefore be considered as a plasticizer of the protein conformation. Whereas hydrophobic interactions have dominated the interpretation of the data, hydrogen bond networks of water may also play a predominant role in water-mediated interactions [48,49]. 

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