STRUCTURAL STUDIES OF ICE NUCLEATOR PROTEINS USING SMALL-ANGLE X-RAY SCATTERING

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Freezing is one of the best methods for food preservation. During the process of food freezing, chemical degradation and microbial spoilage occur at a very low rate, resulting in preserved nutrients and prolonged shelf life. Supercooling occurs when sample temperatures drop below their freezing points prior to solidification. Ice nucleation is a process where initial ice crystals are formed and begin to grow. Supercooling and ice nucleation rates directly affect ice growth pattern and energy costs. Previous researches have demonstrated the effect of potential energy saving and quality improvement of Ice-Nucleation Active (INA) bacteria, P. syringae and Erwinnia herbicola on the freezing of some model and real food systems (Huang et al., 2001). They also succeeded in isolation, purification and characterization of the extracellular ice nucleators (ECINs) from E. herbicola (Li and Lee, 1998a). The use of a biogenic ice nucleator is a unique application of biotechnology, as it directly improves freezing processes. However, until now, most of the researches have been focused on biological effects of ice nucleator proteins as well as their applications. No research has been done to understand the structure of these unique ice nucleator proteins. Therefore, the main objective of this beam- cycle is to understand the conformation change of extracellular ice nucleator proteins with physicochemical parameters, such as pH, ionic strength, protein concentration, and temperature. The correlation between structure and ice nucleating activities of ECINs will be established.