Mass defect, plot

Mass defect plots utilized by Jones and coworkers44 highlight impossible mass defects for the compounds considered and suggest chemical com-... 

Figure 13.2 Theoretical mass defect plot for six common classes of phospholipids.

Figure 13.5 Mass defect plot of a 9.4 T MALDI-FTMS spectrum of Saccharomyces cerevisiae.

The results for bacterial whole-cell analysis described here establish the utility of MALDI-FTMS for mass spectral analysis of whole-cell bacteria and (potentially) more complex single-celled organisms. The use of MALDI-measured accurate mass values combined with mass defect plots is rapid, accurate, and simpler in sample preparation then conventional liquid chromatographic methods for bacterial lipid analysis. Intact cell MALDI-FTMS bacterial lipid characterization complements the use of proteomics profiling by mass spectrometry because it relies on accurate mass measurements of chemical species that are not subject to posttranslational modification or proteolytic degradation. 

As shown in Fig. 6.11, the mass defect plot of each biological matrix analyzed revealed certain dense clusters that are roughly monotonic with mass. (The continuous vertical dots at the low-mass end of each plot are from chemical noise above the arbitrary noise cutoff settings.) The dense mass defect clusters of plasma, bile, and... 

Figure 6.11. Mass defect plots of human biological matrices obtained from high-resolution LC-MS data (a) plasma, (b) bile, (c) feces, and (d) urine. LC-MS data from each biological matrix were combined into one spectrum to generate the mass defect plots, (e) Mass defect plot of 115 marketed drugs. The dotted circle in each plot represents the dense population of the mass defects of 115 marketed drugs.

Fig. S —Binding energies (mass defects) in ergs, plotted against n, where n is the greatest integer such that does not exceed the atomic weight (From Proc. Roy. Soc. A., Vol. 136)...

Fig. 4 shows the minimum film thickness and the maximum mass flux defect, plotted against the number of nodal points. From this figure It can be seen that Che minimum film thickness Is close to Its final value, from six levels upwards. 

To construct such a diagram, a set of defect reaction equations is formulated and expressions for the equilibrium constants of each are obtained. The assumption that the defects are noninteracting allows the law of mass action in its simplest form, with concentrations instead of activities, to be used for this purpose. To simplify matters, only one defect reaction is considered to be dominant in any particular composition region, this being chosen from knowledge of the chemical attributes of the system under consideration. The simplified equilibrium expressions are then used to construct plots of the logarithm of defect concentration against an experimental variable such as the log (partial pressure) of the components. The procedure is best illustrated by an example. 

Figure 1.12. A plot of the number of catalytically produced CO2 molecules against the nuclearity of Au clusters supported on a defect-rich MgO(IOO) surface. The CO2 molecules produced by oxidation of CO are studied by means of temperature-programmed desorption mass spectrometry. (Reproduced with permission from reference 81.)...

A mass spectrum is a plot of the relative abundance of each cation versus mass-to-charge ratio. The peak resulting from the most abundant cation is called the base peak and is assigned an arbitrary intensity of 100. The relative abundances of all other cations in a mass spectrum are reported as percentages of the base peak. Figure 14.2 shows a partial mass spectrum of dopamine, a neurotransmitter in the brain s caudate nucleus, a center involved with coordination and integration of fine muscle movement. A deficiency of dopamine is an underlying biochemicd defect in fhrkinson s disease. 

The mass action expressions can be combined with the full or limited cases of the electroneutrality condition to obtain exact or approximate (limiting case) expressions for the concentration of defects. Such concentrations are typically a function of the oxygen partial pressure, temperature, and doping. It is common to illustrate defect stmctures for oxides by plotting log defect concentrations vs log Pq (Brouwer diagrams) or In or log defect concentrations vs 1/T. We have... 

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