Dispersion biochemical applications

Tuttle, T, and Thiel, W. (2008], OMx-D semiempirical methods with orthogonalization and dispersion corrections. Implementation and biochemical application, Phys. Chem. Chem. Phys. 10,2125-2272. 

The phenomenon of surface-enhanced infrared absorption (SEIRA) spectroscopy involves the intensity enhancement of vibrational bands of adsorbates that usually bond through contain carboxylic acid or thiol groups onto thin nanoparticulate metallic films that have been deposited on an appropriate substrate. SEIRA spectra obey the surface selection rule in the same way as reflection-absorption spectra of thin films on smooth metal substrates. When the metal nanoparticles become in close contact, i.e., start to exceed the percolation limit, the bands in the adsorbate spectra start to assume a dispersive shape. Unlike surface-enhanced Raman scattering, which is usually only observed with silver, gold and, albeit less frequently, copper, SEIRA is observed with most metals, including platinum and even zinc. The mechanism of SEIRA is still being discussed but the enhancement and shape of the bands is best modeled by the Bruggeman representation of effective medium theory with plasmonic mechanism pla dng a relatively minor role. At the end of this report, three applications of SEIRA, namely spectroelectrochemical measurements, the fabrication of sensors, and biochemical applications, are discussed. 

This chapter reviews the recent developments of two types of facilitated transport membranes (1) supported liquid membranes (SLMs) with strip dispersion and (2) carbon-dioxide-selective polymeric membranes, for environmental, energy, and biochemical applications. 

The rapid development of biotechnology during the 1980s provided new opportunities for the application of reaction engineering principles. In biochemical systems, reactions are catalyzed by enzymes. These biocatalysts may be dispersed in an aqueous phase or in a reverse micelle, supported on a polymeric carrier, or contained within whole cells. The reactors used are most often stirred tanks, bubble columns, or hollow fibers. If the kinetics for the enzymatic process is known, then the effects of reaction conditions and mass transfer phenomena can be analyzed quite successfully using classical reactor models. Where living cells are present, the growth of the cell mass as well as the kinetics of the desired reaction must be modeled [16, 17]. 

Advantages of three-phase fluidized beds over trickle beds and other fixed bed systems are temperature uniformity, high heat transfer, ability to add and remove catalyst particles continuously, and limited mass transfer resistances (both external to the particles and bubbles, because of turbulence and limited bubble size, and inside the particles owing to relatively small particle diameters). Disadvantages include substantial axial dispersion (of gas, liquid, and particles), causing substantial deviations from plug flow, and lack of predictability because of the complex hydrodynamics. There are two major applications of gas-liquid-solid-fluidized beds biochemical processes and hydrocarbon processing. 

Cortex Biochem has found interesting applications for magnetizahle particles in analytical fields. Particles of the analytic aid are prepared Ifom a combination of magnetizable materials (iron oxide) and absorbing material (e.g., charcoal, polyacrolein, ion exchange, cellulose). The particles are dispersed in a biological sample to selectively absorb required compounds. After absorption was accomplished, particles with absorbed substance are removed from solution by a magnetized rod. The materials are used for separation of enzymes, protein, cells or bacteria. 

R 466 J. G. Kempf and J. P. Loria, Theory and Applications of Protein Dynamics from Solution NMR , Cell Biochem. Biophys., 2002,37,187 R467 E. Kennett and P. Kuchel, Redox Reactions and Electron Transfer Across the Red Cell Membrane , lUBMB Life, 2003,55, 375 R 468 R. G. Khalifah, Reflections on Edsall s Carbonic Anhydrase Paradoxes of an Ultra Fast Enzyme , Biophys. Chem., 2003,100,159 R 469 A. A. Khrapitchev and P. T. Callaghan, Spatial Dependence of Dispersion , Magn. Reson. Imaging, 2003, 21, 373 R 470 I. V. Khudyakov, N. Arsu, S. Jockusch and N. J. Turro, Magnetic and Spin Effects in the Photoinitiation of Polymerization , Des. Monomers Polym., 2003, 6, 91... 

While many biological/biochemical samples had been studied by dispersive instruments, the difficulties of dealing with aqueous solutions was a severe limitation. Now, however, this general field became a major area of research attention for application of FT-IR in the 1980s. Of interest was the sensitivity of vibrational modes to subtle changes in molecular environment of the type crucial to biological mechanism and structure studies. Particular topics were how cell membrane conformations were affected by interactions with other chemicals or general physicochemical effects, and analyses of protein secondary structure. 

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