**6. Concluding remarks**

The present study amply demonstrated the sensitivity of FTIR technique in the association of biomacromolecule vibrational frequencies to relatively small conformational changes induced by hydration. The critical dependence of the structural properties on the water content may be related to the shape of isotherm curves obtained for ν(OH) component bands and in particu‐ lar to the isteretic behavior of sub‐bands. Water molecules set up very intimate interactions with biological macromolecules. Their structural rearrangement induced by water depriva‐ tion would provide local restructuring of the molecule and modification in the exposition of the side chain groups. The first effect, portrayed by ν(OH) stretching band, affects the second one, monitored by changes in fingerprint characteristic features. The critical interrelations between the hydration shell and the relative mobility of different regions of the molecule allows considerable progresses in this field accounting for the loss of enzymatic activity and functionality for proteins [41], phase transition in lipid assembly [10] and change in physical properties for melanins [9], in conditions of extreme dehydration.
