Density gradient centrifugation technique

Table I. Elemental Analysis and Maceral Composition of Coal PSOC-2 and PSOC-858 Separated by Density Gradient Centrifugation Techniques...

Electron spin resonance determinations of g-values, linewidths, radical densities and saturation properties have been performed on carbon radicals in samples of coal macerals isolated by density gradient centrifugation techniques. These data are compared with elemental analyses and density measurements. Each maceral type exhibits a different ESR signature" which can be understood in terms of the nature of the starting organic and the extent of coalification. 

Density gradient centrifugation is used to separate macromolecules that differ only slightly in size or density. Two techniques are commonly used. 

Although the blood is an easily accessible tissue to study, because red blood cells outnumber leukocytes by about 1000 to 1 in the peripheral circulation, the analysis of leukocytes by any technique is difficult unless the red cells can be removed. Techniques for removing red cells usually involve either density gradient centrifugation (pelleting red cells and neutrophils, leaving lymphocytes and monocytes behind to be collected from a layer as a peripheral blood mononuclear cell preparation [PBMC]) or differential lysis of red blood cells, leaving intact the more robust lymphocytes, monocytes, and neutrophils. 

Enrichment of rare cancer cells from peripheral blood samples is an application that typically requires density gradient centrifugation as a first step. Application of this technique addresses two objectives depletion of erythrocytes and depletion of polymorphonuclear cells. It is expected that cancer cells undergo sedimentation with the mononuclear cell fraction because of their similar density. However, some studies have found that cancer cells are also lost in the polymorphonuclear fraction or the erythrocyte fraction (8,9). Optimization of the density gradient sedimentation step is an important issue in such an application, because it will determine the recovery of rare cells from blood and affect the chances of their detection by immunochemical means. 

We wish to report data on a series of whole coals and coal macerals using conventional CP/MAS, dipolar dephasing, and 2-D dipolar dephasing techniques. These data provide a wealth of new structural information and demonstrate that multiple pulse and 2-D spectroscopic techniques can be utilized on complex carbonaceous materials. We also report data obtained on maceral samples separated by the density gradient centrifugation method which separates coal maceral groups according to density. 

The maceral groups from these coals were separated by the density gradient centrifugation (DGC) technique described by Dyrkacz... 

Techniques are also available for the separation of various cell types in the central nervous system. Among the most widely used methods to separate neuroglial cells from neurons are the techniques described by Sellinger and Azcurra (1974), but other techniques using acetone-glycerol separation of cells or trypsinization of cell suspensions are also available (see Rose, 1968, for a discussion). Methods for the isolation of myelin, postsynaptic membranes, lysosomes, and the vesicles present within nerve terminals that contain neurotransmitters are also available. Invariably, these preparative methods employ some form of density-gradient centrifugation. 

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