Department of Chemistry, Stanford University, Stanford, California 94305, United States.
Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
Anal Chem. 2022 Jul 12;94(27):9750-9757. doi: 10.1021/acs.analchem.2c01336. Epub 2022 Jun 27.
Although it is thought that there is lateral heterogeneity of lipid and protein components within biological membranes, probing this heterogeneity has proven challenging. The difficulty in such experiments is due to both the small length scale over which such heterogeneity can occur, and the significant perturbation resulting from fluorescent or spin labeling on the delicate interactions within bilayers. Atomic recombination during dynamic nanoscale secondary ion imaging mass spectrometry (NanoSIMS) is a non-perturbative method for examining nanoscale bilayer interactions. Atomic recombination is a variation on conventional NanoSIMS imaging, whereby an isotope on one molecule combines with a different isotope on another molecule during the ionization process, forming an isotopically enriched polyatomic ion in a distance-dependent manner. We show that the recombinant ion, CH, is formed in high yield from C- and H-labeled lipids. The low natural abundance of triply labeled acetylide also makes it an ideal ion to probe GM clusters in model membranes and the effects of cholesterol on lipid-lipid interactions. We find evidence supporting the cholesterol condensation effect as well as the presence of nanoscale GM clusters in model membranes.
虽然人们认为生物膜内的脂质和蛋白质成分存在横向异质性，但证明这种异质性具有挑战性。这种实验的困难既源于这种异质性可能发生的小长度尺度，也源于荧光或自旋标记对双层内精细相互作用的显著干扰。在动态纳米二次离子质谱成像（NanoSIMS）中，原子重组是一种非侵入性的方法，可以检查纳米级双层相互作用。原子重组是常规 NanoSIMS 成像的一种变体，在该方法中，在电离过程中一个分子上的一种同位素与另一个分子上的不同同位素结合，以距离依赖的方式形成同位素富集的多原子离子。我们表明，重组离子 CH 是从 C 和 H 标记的脂质中以高产率形成的。三标记乙炔的低天然丰度也使其成为探测模型膜中 GM 簇和胆固醇对脂质-脂质相互作用影响的理想离子。我们发现了支持胆固醇凝聚效应以及模型膜中存在纳米级 GM 簇的证据。
