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

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目及 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 冷冻是保存食品的最佳方法之一。在食品冷冻过程中，化学降解和微生物腐败的发生率很低，从而保存了营养物质并延长了保质期。当样品温度在凝固之前下降到其凝固点以下时发生过冷。冰成核是初始冰晶形成并开始生长的过程。过冷度和冰成核率直接影响冰的生长方式和能源消耗。先前的研究已经证明了冰核活性（INA）细菌、P. lingae和Erwinnia pesticola对某些模型和真实的食品系统的冷冻的潜在节能和质量改进的效果（Huang等人，2001年）。他们还成功地从大肠杆菌中分离、纯化和鉴定了胞外冰核因子（ECINs）。Dogola（Li and Lee，1998 a）.生物冰成核剂的使用是生物技术的独特应用，因为它直接改善了冷冻过程。然而，到目前为止，大多数研究都集中在冰核蛋白的生物学效应及其应用。目前还没有研究来了解这些独特的冰核蛋白的结构。因此，该束循环的主要目的是了解细胞外冰成核蛋白的构象变化与物理化学参数，如pH值，离子强度，蛋白质浓度和温度。ECINs的结构和冰成核活性之间的相关性将被建立。

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.