Sub-atomic resolution X-ray crystallography and neutron crystallography: promise, challenges and potential.
Sub-atomic resolution X-ray crystallography and neutron crystallography: promise, challenges and potential.
复制标题
DOI：
10.1107/s2052252515011239
复制
发表时间：
2015-07-01
期刊：
影响因子：
3.9
通讯作者：
Antonyuk SV
中科院分区：
文献类型：
--
作者：
Blakeley MP;Hasnain SS;Antonyuk SV
中子晶体学和亚原子X射线晶体学在确定氢在大分子中的位置方面相互补充。中子晶体学已经取得了重大进展，但仍需作出很大努力，才能成为主流活动。在国际晶体学年，蛋白质数据库中储存的大分子结构数量超过了10万个，其中超过9万个是由X射线晶体学提供的。被确定为亚原子分辨率（即≤1 μ m）的X射线结构的数量已经超过600个，并且随着衍射限制同步辐射源（如MAX-IV（瑞典）和Sirius（巴西））的建设，这可能会继续快速增长。 已经沉积了十几个超高分辨率的X射线结构（即≤0.7 μ m），可以利用精确的电子密度来获得电荷密度，并提供有关催化或电子转移位点的键合特征的信息。 虽然中子大分子晶体学多年来的发展远没有那么明显，其应用也不那么广泛，但新的和改进的仪器的可用性，以及专用的氘化设施，正在开始改变该领域。在83个沉积有中子衍射数据的大分子结构中，超过一半（49/83，59%）是自2010年以来发布的。亚毫米3晶体现在经常被用于数据收集，一些小蛋白质的结构已经被确定为原子分辨率，更大的单位细胞系统（细胞边缘>100 μ m）正在成功研究中。 虽然与H原子位置有关的一些细节在亚原子分辨率下用X射线晶体学是容易处理的，但某些H原子的移动性使它们无法被定位。此外，高度极化的H原子和质子（H+）在X射线下仍然不可见。此外，大多数X射线结构是由100 K的低温冷却晶体确定的，尽管辐射损伤可以被强烈控制，特别是自从无快门快速探测器的出现以来，并且通过使用有限的剂量和微焦点光束的晶体平移，辐射损伤仍然可以发生。 因此，中子晶体学仍然是可以在室温下收集衍射数据而没有辐射损伤问题的唯一方法，并且是定位移动的或高度极化的H原子和质子的唯一方法。本文综述了亚原子X射线和中子大分子晶体学的现状，并展望了两者结合的前景。还包括两种金属蛋白质亚硝酸铜还原酶和细胞色素c′的新结果，这些结果说明了可以从亚原子分辨率（10.8 μ m）X射线结构中获得的信息类型，同时也强调了补充中子研究的必要性，这些中子研究可以提供X射线晶体学无法提供的H原子细节。
Neutron crystallography and sub-atomic X-ray crystallography complement each other in defining hydrogen positions in macromolecules. Significant advances have been made but much effort is still required if neutron crystallography is to become a mainstream activity. The International Year of Crystallography saw the number of macromolecular structures deposited in the Protein Data Bank cross the 100000 mark, with more than 90000 of these provided by X-ray crystallography. The number of X-ray structures determined to sub-atomic resolution (i.e. ≤1 Å) has passed 600 and this is likely to continue to grow rapidly with diffraction-limited synchrotron radiation sources such as MAX-IV (Sweden) and Sirius (Brazil) under construction. A dozen X-ray structures have been deposited to ultra-high resolution (i.e. ≤0.7 Å), for which precise electron density can be exploited to obtain charge density and provide information on the bonding character of catalytic or electron transfer sites. Although the development of neutron macromolecular crystallography over the years has been far less pronounced, and its application much less widespread, the availability of new and improved instrumentation, combined with dedicated deuteration facilities, are beginning to transform the field. Of the 83 macromolecular structures deposited with neutron diffraction data, more than half (49/83, 59%) were released since 2010. Sub-mm3 crystals are now regularly being used for data collection, structures have been determined to atomic resolution for a few small proteins, and much larger unit-cell systems (cell edges >100 Å) are being successfully studied. While some details relating to H-atom positions are tractable with X-ray crystallography at sub-atomic resolution, the mobility of certain H atoms precludes them from being located. In addition, highly polarized H atoms and protons (H+) remain invisible with X-rays. Moreover, the majority of X-ray structures are determined from cryo-cooled crystals at 100 K, and, although radiation damage can be strongly controlled, especially since the advent of shutterless fast detectors, and by using limited doses and crystal translation at micro-focus beams, radiation damage can still take place. Neutron crystallography therefore remains the only approach where diffraction data can be collected at room temperature without radiation damage issues and the only approach to locate mobile or highly polarized H atoms and protons. Here a review of the current status of sub-atomic X-ray and neutron macromolecular crystallography is given and future prospects for combined approaches are outlined. New results from two metalloproteins, copper nitrite reductase and cytochrome c′, are also included, which illustrate the type of information that can be obtained from sub-atomic-resolution (∼0.8 Å) X-ray structures, while also highlighting the need for complementary neutron studies that can provide details of H atoms not provided by X-ray crystallography.