The glass transition temperature (T-g) of preparations of the restriction enzyme EcoRI, vacuum-dried in the presence of sucrose, trehalose, or raffinose, was determined using differential scanning calorimetry. T-g values were well below those expected for low-moisture sucrose, trehalose, or raffinose, and this was attributed to the presence of glycerol (a plasticizer), which was a main component of the restriction enzyme preparation. This was verified by determining the glass transition temperature of glycerol, which was found to be (onset value) -77 degrees C. Present results confirmed that vitrification (i.e., glass formation) was not necessary for enzyme protection in present low-moisture saccharide systems. As shown in previous work, enzyme EcoRI was very stable stored at 37/45 degrees C in spite of the fact that sugar matrices were completely rubbery, as unequivocally demonstrated in the present work.