Direct Detection\nof Bound Water in Hydrated Powders\nof Lysozyme by Differential Scanning Calorimetry

While exploring the behavior of lysozyme powders at different\npercentages\nof rehydration by differential scanning calorimetry, we noticed a\nsmall peak persistently on the left of the melting point of bulk water,\nwhich, when heating up the system, was always around −10 °C.\nThe intensity of the transition was maximal at 160% rehydration and\ndisappeared at higher values. By comparing the premelting peak properties\nin H<sub>2</sub>O and D<sub>2</sub>O, we attributed it to freezable\nwater bound on the protein surface. This is the first time that such\nan observation has been reported.