HIGH PRESSURE CRYOCOOLING AND RADIATION DAMAGE

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 生物样品的辐射损伤是目前大分子X射线结晶学的主要限制因素之一。在室温下减少辐射损害的最著名的方法之一是将晶体快速冷冻到低温，这通常需要找到穿透性的低温保护剂。最近发展了一种新的晶体冷冻方法--高压冷冻，该方法通过在高压(1000~2000大气压)下冻结晶体来避免使用低温保护剂。高密度无定形(HDA)冰在常压下的密度为1.17g/cm3。 由于二次辐射损伤高度依赖于X射线辐射产生的自由基的扩散，与通常在常压下在晶体内形成的低密度无定形冰相比，HDA冰具有高粘度和高密度，因此可能有效地减少辐射损伤。 我们将测试高压冷冻对辐射损伤的影响。在本研究中，将在几种不同的压力(1atm~4000atm)和不同的化学条件下制备高质量的蛋白质晶体。

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. Radiation damage to biological samples is currently one of the major limiting factors in macromolecular x-ray crystallography. One of the best known method to reduce radiation damage at room temperature is flash freezing crystals to cryogenic temperature, which often requires finding penetrating cryoprotectants. Recently a new crystal freezing method, high pressure cryocooling, was developed, where using of cryoprotectants was avoided by freezing crystals under high pressures (1000 ~ 2000 atm). The mechanism was suggested involving high density amorphous (HDA) ice which has density of 1.17 g/cm3 at ambient pressure. Since the secondary radiation damage highly depends on the diffusion of the free radicals produced by x-ray radiation, HDA ice might be effective to reduce radiation damage due to its high viscosity and density compared to low density amorphous ice that usually forms inside crystal at ambient pressure. We will test the effect of high pressure cryocooling on radiation damage. For the study, high quality protein crystals will be prepared at several different pressures(1 atm ~ 4000 atm) and different chemical conditions.