DESORP TION

Peptide mass fingeiprinting (PMF) is a mass spectrometry based method for protein identification. The protein is cleaved by an enzyme with high specificity (trypsin, Lys-C, Asp-N, etc.) or chemical (CNBr). The peptide mixture generated is analyzed by matrix-assisted laser desorp-tion/ionization (MALDI) or electrospray ionization (ESI)... 

An effective means to facilitate the mass-spectral analysis of rubber acetone extracts is to use desorp-tion/ionisation techniques, such as FD [92,113] and FAB [92]. FAB mass spectra for rubber extracts are generally more complex (due to fragment ions) than FD spectra of the same materials. Nevertheless, the FAB spectra are often complementary to FD, since ... 

Du, Z. Yang, R. Guo, Z. Song, Y. Wang, J. Identification of Staphylococcus aureus and determination of its methicillin resistance by matrix-assisted laser desorp-tion/ionization time-of-flight mass spectrometry. Anal. Chem. 2002,74,5487-5491. 

Dai, Y. Li, L. Roser, D. C. Long, S. R. Detection and identification of low-mass peptides and proteins from solvent suspensions of Escherichia coli by high performance liquid chromatography fractionation and matrix-assisted laser desorp-tion/ionization mass spectrometry. Rapid Comm. Mass Spectrom. 1999,13, 73-78. 

Merkel, D., et al., Proteomic study of human bronchoalveolar lavage fluids from smokers with chronic obstructive pulmonary disease by combining surface-enhanced laser desorp-tion/ionization-mass spectrometry profiling with mass spectrometric protein identification, Proteomics. 5, 11, 2972, 2005. 

A number of models have been developed to reflect the actual sorption/desorp-tion processes that occur in the natural environment [1,29-33]. Some models have a sound theoretical basis however, they may have only limited experimental utility because the assumptions involved in the development of the relationship apply only to a limited number of sorption processes. Other models are more empirical in their derivation, but tend to be more generally applicable. In the latter case, the theoretical basis is uncertain. 

Accordingly, sorption has received a tremendous amount of attention and any method or modeling technique which can reliably predict the sorption of a solute will be of great importance to scientists, environmental engineers, and decision makers (references herein and in Chaps. 2 and 3). The present chapter is an attempt to introduce an advanced modeling approach which combines the physical and chemical properties of pollutants, quantitative structure-activity, and structure-property relationships (i. e., QSARs and QSPRs, respectively), and the multicomponent joint toxic effect in order to predict the sorption/desorp-tion coefficients, and to determine the bioavailable fraction and the action of various organic pollutants at the aqueous-solid phase interface. 

Each of the properties of the PCB isomers, listed above (Sect. 3.1.2) and either measured or calculated using various equations presented in Sect. 2.1, plays a role in the environmental distribution of these contaminants, especially at air-solid and water-solid interfaces. From the physical and chemical properties specific for PCBs and their isomers (Table 7, Figs. 2-8), the following information evaluates routes by which PCBs are lost from a particular source, spill or environmental compartment, that includes air-solid or aqueous-solid phase interfaces. These include vaporization (i.e., solid— air process), sorption/desorp-tion and partitioning (i.e., water <- solid processes) and biodegradation (i.e., water <- biosolid interactions). 

Modifying the surface characteristics to enhance the charge storage. There is a broad protocol to modify the surface characteristics of carbon materials, especially the nanostructured carbon materials, to have excellent adsorption/desorp-tion behavior ... 

Frauenkron, M. Berkessel, A. Gross, J.H. Analysis of Ruthenium Carbonyl-Porphyrin Complexes a Comparison of Matrix-Assisted Laser Desorp-tion/Ionization Time-of-Flight, Fast-Atom Bombardment and Field Desorption Mass Spectrometry. Eur. Mass Spectrom. 1997, 5,427-438. 

Overberg, A. Karas, M. Bahr, U. Kauf-maim, R. Hillenkamp, F. Matrix-Assisted Infrared-Laser (2.94 Mm) Desorp-tion/Ionization-MS of Large Biomolecules. Rapid Commun. Mass Spectrom. 1990,... 

Beavis, R.C. Chaudhary, T. Chait, B.T. a-Cyano-4-Hydroxycinnamic Acid As a Matrix for Matrix-Assisted Laser Desorp-tion-MS. Org. Mass Spectrom. 1992, 27, 156-158. 

Prans, J.K. Vietzke, J.-P. Strassner, M. Rapp, C. Hintze, U. Konig, W.A. Characterization of Low Molecular Weight Hydrocarbon Oligomers by Laser Desorp-tion/Ionization-TOF-MS Using a Solvent-Free Sample Preparation Method. Rapid... 

Jones, R.M. Lamb, J.H. Lim, C.K. Urinary Porphyrin Profiles by Laser Desorp-tion/Ionization-TOF-MS Without the Use of Classical Matrixes. Rapid Commun. Mass Spectrom. 1995, 9, 921-923. 

Welham, K.J. Domin, M.A. Johnson, K. Jones, L. Ashton, D.S. Characterization of Fungal Spores by Laser Desorp-tion/Ionization-TOF-MS. Rapid Commun. Mass Spectrom. 2000,14, 307-310. 

Wei, J. Buriak, J.M. Siuzdak, G. Desorp-tion-lonization-MS on Porous Silicon. Nature 1999,599,243-246. 

Shen, Z. Thomas, J.J. Averbuj, C. Broo, K.M. Engelhard, M. Crowell, J.E. Finn, M.G. Siuzdak, G. Porous Silicon As a Versatile Platform for Laser Desorp-tion/Ionization-MS. Anal. Chem. 2001, 75, 612-619. 

Z. Shen, f. J. Thomas, C. Averbuj, K. M. Broo, M. Engelhard, J. E. Crowell, M. G. Finn, G. Siuzdak Porous silicon as a versatile platform for laser desorp-tion/ionization mass spectrometry, Anal. Chem. 2001, 73, 612-619. 

Zhang, P.C. Sparks, D.L. (1989) Kinetics and mechanism of molybdate adsorption/desorp-tion at the goethite/water interface using pressure-jump relaxation. Soil Sci. Soc. Am. 

Carson, P. G., M. V. Johnston, and A. S. Wexler, Laser Desorp-tion/Ionization of Ultrafine Aerosol Particles, Rapid Commun. Mass Spectrosc., 11, 993-996 (1997b). 

Dale, J. M M. Yang, W. B. Whitten, and J. M. Ramsey, Chemical Characterization of Single Particles by Laser Ablation/Desorp-tion in a Quadrupole Ion Trap Mass Spectrometer, Anal. Chem., 66, 3431-3435 (1994). 

The use of chemical modelling to predict the formation of secondary phases and the mobility of trace elements in the CCB disposal environment requires detailed knowledge of the primary and secondary phases present in CCBs, thermodynamic and kinetic data for these phases, and the incorporation of possible adsorp-tion/desorption reactions into the model. As noted above, secondary minerals are typically difficult to identify due to their low abundance in weathered CCB materials. In many cases, appropriate thermochemical, adsorption/desorp-tion and kinetic data are lacking to quantitatively describe the processes that potentially affect the leaching behaviour of CCBs. This is particularly tme for the trace elements. Laboratory leaching studies vary in the experimental conditions used (e.g., the type and concentration of the extractant solution, the L/S ratio, and other parameters such as temperature and duration/ intensity of agitation), and therefore may not adequately simulate the weathering environment (Rai et al. 1988 Eary et al. 1990 Spears Lee, 2004). 

Liu, S.Q., Sun, H.R., Sun, M.Z., and Xu, J.Q. 1999. Investigation of a series of synthetic cationic porphyrins using matrix-assisted laser desorp-tion/ionization time-of-flighl mass spectrometry. Rapid Commun. Mass Spectrom. 13 2034-2039. 

N diffuses into the structural pores of clinoptilolite 10 to 10 times faster than does CH4. Thus internal surfaces are kinetically selective for adsorption. Some clino samples are more effective at N2/CH4 separation than others and this property was correlated with the zeolite surface cation population. An incompletely exchanged clino containing doubly charged cations appears to be the most selective for N2. Using a computer-controlled pressure swing adsorption apparatus, several process variables were studied in multiple cycle experiments. These included feed composition and rates, and adsorber temperature, pressure and regeneration conditions. N2 diffusive flux reverses after about 60 seconds, but CH4 adsorption continues. This causes a decay in the observed N2/CH4 separation. Therefore, optimum process conditions include rapid adsorber pressurization and short adsorption/desorp-tion/regeneration cycles. 

They screened seven libraries, each containing 19 peptides of different masses, and found the sequences that bound most tightly to Tom20. Matrix-assisted laser desorp-tion/ionization time-of-flight mass spectrometry (MALDI-TOF MS) served as a readout that allowed the ionized peptides to be observed directly. Using this approach, Kohda and colleagues discovered that the recognition site spans six residues, not the previously established five, and were able to refine sequence preferences further. 

Stutz H Advances in the analysis of proteins and peptides by capillary electrophoresis with matrix-assisted laser desorp-tion/ionization and electrospray-mass spectrometry detection. Electrophoresis (2005) 26 1254-1290. 

Fig. 2 (a) The optical image of a rat brain from a coronal section, (b) Matrix-assisted laser desorp-tion/ionization (MALDI)-mass spectrometry (MS)/MS images of astemizole in the rat brain slice without perfusion and (c) with perfusion cortex, hippocampus, corpus callosum, hypothalamic region, thalamus region, choroid plexus, dorsal third ventricle, and lateral ventricle are indicated by arrows, (d) MALDI-MS/MS images of M-14 metabolite of astemizole in the rat brain slice (Li et al. [152], Reproduced with permission from Future Science Ltd)... 

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