Goraczko Andrzej J
Department Inorganic Chemistry, University of Technology and Agriculture, Seminaryjna 3, 85-326, Bydgoszcz, Poland.
J Mol Model. 2007 Jul;13(6-7):813-21. doi: 10.1007/s00894-007-0206-7. Epub 2007 May 9.
The occurrence of poly-isotopic elements in a molecule or ion can result in complex isotopomeric cluster of an ion. The "isotopomer" better and correctly indicates different isotopic compositions of a molecule (compound) or ion and not a single atom. The ions of organic compounds show in accurate mass spectra single, isolated peaks or narrow sub-clusters regardless of their molecular masses. The occurrence of a PIE makes the molecular ion cluster more complex and significantly influences the location of the most abundant peak and the form of the cluster. The present study is an attempt at answering the following question: what is the mechanism of the molecular ion's isotopomeric cluster formation and is it step-by-step predictable? The accurate mass-resolved isotopomer cluster can be predicted from accurate masses and abundances of the stable isotopes. The cluster consists of several sub-patterns, each of which is composed of near signals (at the same nominal m/z). The range of the sub-cluster usually does not exceed 0.005 u. The low-resolution cluster can be predicted from the high-resolution pattern by addition of all peaks occurring over a given narrow mass range (m/z - 0.5; m/z+0.49). Surprisingly, predicting the accurate mass cluster is simpler than predicting the low-resolution one. A compliance of the model results with the experimental ones suggests a correct prediction.
分子或离子中多同位素元素的存在会导致离子形成复杂的同位素异构体簇。“同位素异构体”能更好且准确地表示分子（化合物）或离子的不同同位素组成，而非单个原子。有机化合物的离子在精确质量谱中呈现出单个、孤立的峰或狭窄的子簇，与它们的分子量无关。多同位素元素的存在会使分子离子簇更加复杂，并显著影响最丰度峰的位置和簇的形态。本研究旨在回答以下问题：分子离子的同位素异构体簇形成机制是什么，以及它是否可以逐步预测？精确质量分辨的同位素异构体簇可以根据稳定同位素的精确质量和丰度进行预测。该簇由几个子模式组成，每个子模式由相近的信号（在相同的标称m/z处）构成。子簇的范围通常不超过0.005 u。低分辨率簇可以通过将给定窄质量范围内（m/z - 0.5；m/z + 0.49）出现的所有峰相加，从高分辨率模式预测得到。令人惊讶的是，预测精确质量簇比预测低分辨率簇更简单。模型结果与实验结果的吻合表明预测是正确的。
