Chandra S, Ausserer W A, Morrison G H
Department of Chemistry, Cornell University, Ithaca, NY 14853-1301.
J Microsc. 1987 Dec;148(Pt 3):223-9. doi: 10.1111/j.1365-2818.1987.tb02869.x.
SIMS matrix effects (mass interferences, sputter yield variations and practical ion yield variations) were evaluated in freeze-fractured, freeze-dried cultured cells at the approximately 0.5 micron spatial resolution of the Cameca IMS-3f ion microscope. Cell lines studied include normal rat kidney (NRK), 3T3 mouse fibroblast, L6 rat myoblast, chinese hamster ovary (CHO) and rat kangaroo kidney (PtK2) cells. High mass resolution studies indicated that the secondary ion signals of H-, C-, O-, Na+, Mg+, CN-, P-, S-, Cl-, K+ and Ca+ were free from major mass interferences. However, a large mass interference was observed for nitrogen at mass 14. No significant sputtering yield difference between the nuclear and cytoplasmic compartments of the cells studied was observed. The subcellular distributions of the major (H, C, N and O) and minor (P, S, K, Cl, Na, Mg and Ca) matrix elements were found to be largely homogeneous with the exception of Ca, which was observed mainly in the cell cytoplasm. Practical ion yield variations were compared by three different approaches: (i) by the use of cells doped with known electrolyte concentrations, (ii) by quantitative ion implantation, and (iii) by analysis of the same cell with both electron probe and ion microscope. Each approach indicated an absence of significant practical ion yield differences between the nuclear and cytoplasmic regions of these specimens. These observations indicate that secondary ion signals in this type of sample are not significantly affected by local matrix effect variations. Hence, qualitative imaging of such specimens provides a true representation of subcellular elemental distributions. These observations should allow the development of quantitative ion imaging methodologies and enhance the applicability of ion microscopy to biomedical problems.
在使用卡美卡IMS-3f离子显微镜约0.5微米的空间分辨率下，对冷冻断裂、冷冻干燥的培养细胞中的二次离子质谱（SIMS）基质效应（质量干扰、溅射产率变化和实际离子产率变化）进行了评估。所研究的细胞系包括正常大鼠肾（NRK）、3T3小鼠成纤维细胞、L6大鼠成肌细胞、中国仓鼠卵巢（CHO）细胞和大鼠袋鼠肾（PtK2）细胞。高质量分辨率研究表明，H-、C-、O-、Na+、Mg+、CN-、P-、S-、Cl-、K+和Ca+的二次离子信号没有主要的质量干扰。然而，在质量数14处观察到氮有较大的质量干扰。在所研究的细胞的核区和胞质区之间未观察到明显的溅射产率差异。发现主要（H、C、N和O）和次要（P、S、K、Cl、Na、Mg和Ca）基质元素的亚细胞分布在很大程度上是均匀的，除了Ca主要存在于细胞质中。通过三种不同的方法比较了实际离子产率变化：（i）使用掺杂已知电解质浓度的细胞，（ii）通过定量离子注入，以及（iii）通过电子探针和离子显微镜对同一细胞进行分析。每种方法都表明这些样本的核区和胞质区之间没有明显的实际离子产率差异。这些观察结果表明，这类样品中的二次离子信号不受局部基质效应变化的显著影响。因此，此类样品的定性成像提供了亚细胞元素分布的真实表示。这些观察结果应有助于开发定量离子成像方法，并提高离子显微镜在生物医学问题中的适用性。
