Other Reported Cell Designs

Bond and coworkershave developed a small-volume (0.2 ml) variable-temperature EPR spectroelectrochemical cell that enables simultaneous rapid-scan voltammetry and EPR measurements to be made. The performance of this cell is compared to that of a flow-through cell designed by Coles and Compton. The small-volume cell permits cyclic voltammetric studies at variable temperatures but has significantly lower sensitivity compared to the flow-through cell, which is not amenable to low-temperature work. 

In 1990 Kaim el al detailed an in-situ two-electrode EPR cell with a Pt tip working electrode and a Pt wire electrode contained in an EPR tube with an 

A laminated platinum-mesh working electrode positioned in an EPR fiat cell combined with a Ag pseudoreference electrode and a Pt counter electrode was used by Dunsch and coworkers for the in-situ study of C120O. The same group also performed simultaneous variable temperature EPR/UV-Vis-NIR experiments on Wurster s reagent and thianthrene. Similar cells using laminated ITO and gold working electrodes have also been reported.  

An EPR microspectroelectrochemical low-temperature cell has been detailed by Wilgocki and Rybak with a Pt working electrode and has been used to characterise the unstable cation [O = Re(OEt)Cl2(py)2] - 

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It should be emphasized at this point that the use of physicochemical methods is so far the only way to demonstrate the import of transgene DNA into the mitochondrial matrix in living mammalian cells. The unavailability of a mitochondria-specific reporter plasmid designed for mitochondrial expression severely hampers current efforts toward the development of effective mitochondrial expression vectors. Although any new nonviral transfection system (i.e., cationic lipids, polymers, and others) aimed at the nuclear-cytosolic expression of proteins can be systematically tested and subsequently improved by utilizing anyone of many commercially available reporter gene systems, such a methodical approach to develop mitochondrial transfection systems is currently impossible. 

Besides this remarkably fast commercial development, other research groups designed their own laboratory-compatible LAPS systems for similar purposes. The use of, e.g., a nicotinic acetylcholine receptor was reported to create a LAPS-receptor biosensor capable of detecting receptor ligands (acetylcholine, carbamylcholine, succinylcholine, sub-eryldicholine, nicotine as well as d-tubocurarine, a-bungarotoxin and a-Naja toxin) [85]. Another system quite similar to the Cytosensor setup was introduced, where mouse fibroblast fine 3T6 cells were chosen to demonstrate the determination of metabolic processes of these cells [86]. 

Lunsford and coworkers (Xie et al., 1999) reported kinetics data characterizing the catalytic NO decomposition measured in their Raman cell. Other attempts were made by Volta and coworkers (Abdelouahab et al., 1992), but only low conversions were reached for alkane oxidation because of significant temperature gradients (Volta et al., 1992). The cell designed by Stair (2001) appears to be suitable for simultaneous determination of spectra and catalytic activity. Several groups have addressed the issue of obtaining accurate catalytic performance data when the reactor is a spectroscopic cell (Banares and Khatib, 2004 Guerrero-Perez and Banares, 2002 Kerkhof et al., 1979 Mestl, 2002). 

In an early application of energy dispersive XAFS spectroscopy, Keegan et al. (1991) performed time-resolved measurements by using a "stage of the type commonly used for microscopy" to hold the catalyst sample in the beam. The design consisted of a small furnace with Kapton windows that held a pressed wafer of the catalyst. Unfortunately no other detail is provided in the report of this cell design. 

Emf measurements were made with a Leeds and Northrup K-5 potentiometer equipped with a Leeds and Northrup DC null detector (Model 9829). The temperature of the bath was regulated to within 0.02 K. Details of the experimental procedure, including preparation of the electrodes (19), cell design, preparation of solutions, purification of the hydrogen gas, and other experimental aspects, have been reported elsewhere (13,14). 

The capped porphyrins prepared by Baldwin et al. [56, 57] are other model systems designed to test the consequences of steric hindrance on CO binding (Scheme 4). These compounds were reported to discriminate against dioxygen in favor of carbon monoxide [62, 119-121]. The CO affinity of the capped porphyrins differs by less than a factor of three from that of unprotected iron(II) tetraphenylporphyrin, while the dioxygen affinity is more than a factor of 100 lower. Kinetic studies of CO binding show that the CO dissociation rate constants are very similar to those of unprotected hemes. Recently, the X-ray crystal structure of a carbonylated complex of the smallest capped porphyrin was obtained [122]. The CO ligand is reported to deviate 7° and 4° from the heme normal, respectively, for each independent molecule present in the unit cell. 

The experiments reported here were designed to demonstrate the feasibility of the measurement and to provide an initial test of the theory. As single beam experiments, the results are laser noise limited. Planned elaboration of the equipment to make double beam measurements should provide an increase in sensitivity. Other modifications which may improve detectability are cell design changes to reduce cell wall absorptions while maintaining minimal cell volume, laser output feed-back control, and signal averaging. With improved sensitivity the use of lower power tunable laser excitation will be feasible. Eventual improvement of sensitivity to the level required for use of continuum sources is at present doubtful. 

At the top level, if one has a number of cells, a few sub-designs, and others, library cells, report cell is one wry to get the entire list of cells and their instance names at the top level. This script helps to get the instance names of only the subdesigns in the hierarchy. 

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