ELEMENTAL MAPPING AT LOW DOSE

低剂量元素图谱

• 批准号: 6120553
• 负责人: JOSEPH S WALL
• 金额: $ 0.96万
• 依托单位: BROOKHAVEN SCIENCE ASSOC-BROOKHAVEN LAB
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-04-01 至 2000-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6120553
• 关键词: biomedical equipment development; biomedical resource; building /facility design /renovation; nucleic acids; proteins; technology /technique

The phosphorus L2, edge at 132 eV energy loss is very weak but provides an element-specificsignal. Direct imaging of phosphorus using electrons which have lost this amount of energy would require a dose much higher than that known to damage molecules. However low dose imaging is possible in the STEM using the simultaneously recorded dark field annular detector signal to locate particles for image averaging. Summing the weak phosphorus signal from several thousand aligned particles should be adequate to obtain a phosphorus map of essentially undamaged molecules. Preliminary data on ribosomal subunits indicated the feasibility -of many parts -of the project In that case the difference of large angle and small angle scattering gave a significant signal when averaged -over 1,000 aligned particle images, whereas the TMV (tobacco mosaic virus) control subtracted to background. This may be indicative of the RNA distribution in the subunits, but the arguments are indirect The elemental map should be much more straightforward to interpret. A key unknown is the degree of localization possible with the 132 eV loss electrons. This is -estimated to be better than'b.5 nra, but needs to be tested. Control specimens will be TMV and filamentous viruses which are ideal for alignment and have known or strongly predicted phosphorus distributions. Once the protocols for data collection are established and control spectra match theory, phosphorus mapping will be attempted on 30S and 50S ribosomal subunits. In addition to distinguishing nucleic, acid from protein, this technique should be useful for ing phosphorylated proteins and phospholipids. The same technique can be applied to elemental mapping of B, C, N, 0, F; Fe, Mg, Ca and other elements in our specimens using the appropriate energy loss and control signals.

在132 eV能量损失下，磷L2，EDGE很弱，但是 提供特定于元素的信号。磷的直接成像 使用已经失去这种能量的电子将需要一个 比已知的破坏分子的剂量高得多。不管多低 在STEM中使用同时记录的剂量成像是可能的 用于定位图像中粒子的暗场环形探测器信号 平均。从几千个微弱的磷信号中求和 排列好的颗粒应足以获得磷图 基本上没有损坏的分子。核糖体的初步数据 分单位表明了该项目许多部分的可行性。 在这种情况下，大角度和小角度散射的区别 在平均时给出了显著的信号 1,000个排列的颗粒图像，而TMV(烟草花叶病毒) 控件减去到背景。这可能是RNA的指示 子单元中的分布，但参数是间接的 元素地图应该更容易理解。一把钥匙 未知的是132 eV损耗可能的本地化程度 电子。据估计，这比b.5NRA更好，但需要 接受测试。对照标本为烟草花叶病毒和丝状病毒 它们是配准的理想对象，并且已知或已强烈预测 磷的分布。一旦用于数据收集的协议 建立和控制光谱匹配理论，将磷映射 在30s和50s核糖体亚基上尝试。除了……之外 区分核酸、酸和蛋白质，这项技术应该是 适用于磷酸化蛋白质和磷脂。相同 该技术可应用于B，C，N，0，F，Fe， 在我们的标本中使用适当的镁、钙和其他元素 能量损失和控制信号。