ELEMENTAL MAPPING AT LOW DOSE

低剂量元素图谱

• 批准号: 6308950
• 负责人: JOSEPH S WALL
• 金额: $ 0.97万
• 依托单位: BROOKHAVEN SCIENCE ASSOC-BROOKHAVEN LAB
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-04-01 至 2001-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6308950
• 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.

磷 L2，132 eV 处的边缘能量损失非常弱，但 提供元素特定信号。 磷的直接成像 使用失去这么多能量的电子将需要 剂量远高于已知的破坏分子的剂量。 无论多么低 使用同时记录的 STEM 中的剂量成像是可能的 暗场环形探测器信号用于定位图像颗粒 平均。 总结数千个微弱的磷信号 对齐的颗粒应该足以获得磷图 分子基本上未受损。 核糖体的初步数据 子单位表明了该项目许多部分的可行性 这种情况下大角度和小角度散射的差异 平均时给出显着信号 1,000 个对齐的颗粒图像，而 TMV（烟草花叶病毒） 对照减去背景。 这可能表明 RNA 分布在子单元中，但参数是间接的 元素图应该更容易解释。 一把钥匙 未知的是 132 eV 损失可能实现的定位程度 电子。 据估计，这比 'b.5 nra 更好，但需要 被测试。 对照标本为 TMV 和丝状病毒 这是对齐的理想选择并且已经已知或强烈预测 磷分布。 一旦数据收集协议确定 建立并控制光谱匹配理论，磷图谱将 尝试在 30S 和 50S 核糖体亚基上进行。 此外 区分核酸、蛋白质和核酸，这项技术应该是 可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的元素映射；铁， 我们的样品中的 Mg、Ca 和其他元素使用适当的 能量损失和控制信号。