Grant: Operating Grant

We are studying several types of ice-binding proteins. These include antifreeze proteins (AFP) which bind to the surface of ice crystals and stop them from growing. These proteins help organisms like fishes and some insects to avoid freezing through this lowering of the freezing point. One medical application of these AFPs is to help cool organs and tissues below zero prior to transplantation into patients without damage to the organs by ice crystals. The colder the organ, the longer it will last. We have discovered that some AFPs are ten times better at lowering the freezing point than others and we want to learn why this is and how their activity can be further improved by the addition of enhancer proteins, about which little is known. When ice freezes, the presence of some AFPs can make it form sharp needle-like crystals which are useful in cryosurgery for killing tumour cells. Again we need to know more about how these proteins interact with ice to change its shape. Other AFPs seem to help organisms tolerate freezing. Here their role seems to be stopping the growth of large ice crystals at the expense of small ones. In other words, they are ice recrystallization inhibitors, which are finding many uses in frozen products to stop freeze-thaw damage. Again, there are medical applications for the cryopreservation of cells and tissues. We are also exploring the link between AFPs and ice nucleating proteins. The latter have applications in rain/snow making and controlled freezing. We are investigating the hypothesis that ice nucleating proteins are like AFPs in structure but are 10- to 20- larger. If so, we should be able to protein engineer the interchange by making one smaller and the other larger. Learning how these different ice-binding proteins are related and how they function mechanistically will pave the way for biotechnological applications in the medical and biological fields.