ELECTRON CRYSTALLOGRAPHY

电子晶体学

• 批准号: 6280686
• 负责人: WILLIAM TIVOL
• 金额: $ 0.05万
• 依托单位: WADSWORTH CENTER
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-01-01 至 1998-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6280686
• 关键词: biomedical resource; microscopy; technology /technique

(Supported by NIH GMS 46733 to D. Dorsett). During the last few years it has become obvious that electron crystallography is a practical method for determining molecular structure at the atomic level. Further, theoretical advances have made it possible to solve such structures using the traditional methods of crystallography with and without the use of images to make initial phase guesses. Dr. Dorset is a world leader in the development of these methodologies in general and in the use of direct methods of structure determination in particular. A co-worker of Dr. Dorset's, Dr. Herbert Hauptman, received the Noble Prize for development of these methods as applied to x-ray crystallography. One of the major problems limiting the advancement of electron crystallography is the treatment of secondary and dynamic scattering. Both of these phenomena are reduced if not eliminated by collecting the diffraction data using high-voltage, i.e. megavolt, electron beams. Previous progress reports have described the successful determination of the structures of copper perchloro- and perbromo-phthalocyanine. These model compounds illustrated both the possibility of determining atomic-level structures using electron crystallography and the necessity of high-voltage for the reduction of dynamical scattering. In contrast to the phthalocyanines, anthracene requires that a three-dimensional (3-D) data set be collected, which makes it a logical next step in the development of our capability. Anthracene also requires the use of our cryostage which allows us to gain experience in cryoelectron diffraction using relatively inexpensive and easily prepared specimens. A 3-D data set from anthracene is being collected to test our ability to extend our methods from two-dimensional projections to true 3-D structure determination. The anthracene data are being analyzed to determine both the intensities and the zone axes. Many patterns have been collected and analyze d, and this is ongoing. We are still working on determining how many different zone axes are represented, and will subsequently use the data set to identify problems with the merging of the data into a 3-D set. After an adequate data set has been assembled a full 3-D structure will be determined. A through-focus series of germanium film was caried out for determining the spherical aberration coefficient of the HVEM, needed for this work.

（由NIH GMS 46733支持。Dorsett）。 在过去几 多年来，电子晶体学显然是一种 测定分子原子结构的实用方法 水平 此外，理论上的进步使解决 这种结构使用传统的晶体学方法， 并且不使用图像来进行初始相位猜测。 博士 多塞特是这些方法发展的世界领导者， 一般和在使用直接方法的结构测定， 特别的。 多塞特医生的同事赫伯特·豪普特曼医生 获得了诺贝尔奖的发展，这些方法的应用 到X射线晶体学 其中一个主要的问题限制了 电子晶体学的进步是对二次 和动态散射。 如果不这样做，这两种现象都会减少 通过使用高电压收集衍射数据来消除，即， 兆伏电子束 以前的进度报告描述了 成功地测定了四氯合铜的结构， 和全溴酞菁。 这些模型化合物说明了 利用电子确定原子级结构可能性 晶体学和高电压的必要性， 动态散射 与酞菁相反，蒽 需要收集三维（3-D）数据集， 使其成为我们能力发展的合理下一步。 蒽还需要使用我们的冷冻台， 在低温电子衍射方面积累经验， 廉价且易于制备的样品。 一个三维数据集， 收集蒽是为了测试我们扩展我们的能力， 从二维投影到真三维结构的方法 保持战略定力 我们正在分析蒽的数据 强度和区域轴。 许多模式已经被 收集和分析数据，这是正在进行的。 我们还在努力 确定表示了多少个不同的区域轴，并将 随后使用该数据集来识别合并的问题， 把数据转换成三维图像 在获得足够的数据集后， 一个完整的三维结构将被确定。 一个贯穿焦点 用一系列锗膜测定了锗的球形度 HVEM的像差系数，这项工作所需的。