NMR光谱学的一项重要最新进展是非原位动态核极化(DNP)方法的问世,该方法能够产生的液相灵敏度要远远超过最高光谱仪所提供的灵敏度。灵敏度的提高引发了新的研究途径,特别是有关通过NMR光谱法对体内代谢和疾病进行监测的方法。到目前为止,主要针对非质子化低γ核的实验已经实现了这种收益。较长的弛豫时间T 1所支持的目标,这使他们能够承受从低温超极化器到感兴趣的反应中心的转移。最近的研究还表明,通过间接检测的方法将这种超极化转移到质子上可以成功地产生具有高灵敏度的超极化化合物的1 H NMR光谱。本研究表明,当与空间编码方法合并时,间接检测的1 H NMR光谱也可以用作时间分辨超极化光谱。因此,引入了一种可以成功交付一系列超极化1的方法。1分钟长的时间范围内的1 H NMR光谱。通过跟踪胆碱激酶(一种潜在的癌症代谢标志物)对胆碱进行体外磷酸化,可以举例说明这种方法带来的原理和机遇。并通过乙酰胆
NMR光谱学的一项重要最新进展是非原位动态核极化(DNP)方法的问世,该方法能够产生的液相灵敏度要远远超过最高光谱仪所提供的灵敏度。灵敏度的提高引发了新的研究途径,特别是有关通过NMR光谱法对体内代谢和疾病进行监测的方法。到目前为止,主要针对非质子化低γ核的实验已经实现了这种收益。较长的弛豫时间T 1所支持的目标,这使他们能够承受从低温超极化器到感兴趣的反应中心的转移。最近的研究还表明,通过间接检测的方法将这种超极化转移到质子上可以成功地产生具有高灵敏度的超极化化合物的1 H NMR光谱。本研究表明,当与空间编码方法合并时,间接检测的1 H NMR光谱也可以用作时间分辨超极化光谱。因此,引入了一种可以成功交付一系列超极化1的方法。1分钟长的时间范围内的1 H NMR光谱。通过跟踪胆碱激酶(一种潜在的癌症代谢标志物)对胆碱进行体外磷酸化,可以举例说明这种方法带来的原理和机遇。并通过乙酰胆
Dynamic Reorganization and Correlation among Lipid Raft Components
作者:Mónica M. Lozano、Jennifer S. Hovis、Frank R. Moss、Steven G. Boxer
DOI:10.1021/jacs.6b05540
日期:2016.8.10
Lipid rafts are widely believed to be an essential organizational motif in cell membranes. However, direct evidence for interactions among lipid and/or protein components believed to be associated with rafts is quite limited owing, in part, to the small size and intrinsically dynamic interactions that lead to raft formation. Here, we exploit the single negative charge on the monosialoganglioside Gmi, commonly associated with rafts, to create a gradient of Gm, in response to an electric field applied parallel to a patterned supported lipid bilayer. The composition of this gradient is visualized by imaging mass spectrometry using a NanoSIMS. Using this analytical method, added cholesterol and sphingomyelin, both neutral and not themselves displaced by the electric field, are observed to reorganize with Gml. This dynamic reorganization provides direct evidence for an attractive interaction among these raft components into some sort of cluster. At steady state we obtain an estimate for the composition of this cluster.
Colocalization of the Ganglioside G<sub>M1</sub> and Cholesterol Detected by Secondary Ion Mass Spectrometry
作者:Mónica M. Lozano、Zhao Liu、Eva Sunnick、Andreas Janshoff、Krishna Kumar、Steven G. Boxer
DOI:10.1021/ja310831m
日期:2013.4.17
The characterization of the lateral organization of components in biological membranes and the evolution of this arrangement in response to external triggers remain a major challenge. The concept of lipid rafts is widely invoked; however, direct evidence of the existence of these ephemeral entities remains elusive. We report here the use of secondary ion mass spectrometry (SIMS) to image the cholesterol-dependent cohesive phase separation of the ganglioside G(M1) into nano- and microscale assemblies in a canonical lipid raft composition of lipids. This assembly of domains was interrogated in a model membrane system composed of palmitoyl sphingomyelin (PSM), cholesterol, and an unsaturated lipid (dioleoylphosphatidylcholine, DOPC). Orthogonal isotopic labeling of every lipid bilayer component and monofluorination of G(M1) allowed generation of molecule specific images using a NanoSIMS. Simultaneous detection of six different ion species in SIMS, including secondary electrons, was used to generate ion ratio images whose signal intensity values could be correlated to composition through the use of calibration curves from standard samples. Images of this system provide the first direct, molecule specific, visual evidence for the colocalization of cholesterol and G(M1) in supported lipid bilayers and further indicate the presence of three compositionally distinct phases: (1) the interdomain region; (2) micrometer-scale domains (d > 3 mu m); (3) nanometer-scale domains (d = 100 nm to 1 mu m) localized within the micrometer-scale domains and the interdomain region. PSM-rich, nanometer-scale domains prefer to partition within the more ordered, cholesterol-rich/DOPC-poor/G(M1)-rich micrometer-scale phase, while G(M1)-rich, nanometer-scale domains prefer to partition within the surrounding, disordered, cholesterol-poor/PSM-rich/DOPC-rich interdomain phase.