Dual probe

Fig. 6. Spectra of 2-methyl-5-bromopentaiie acquired using a Bruker 300AMX spectrometer (a) TOCSY using a 5-mm dual probe and (b) HMQC...

There is a vast array of probes available to do many specialist jobs but for the work that we will discuss in this book, a proton-carbon dual probe would perform most of the experiments (although having a four nucleus probe is better as this would allow other common nuclei such as fluorine or phosphorus to be observed). 

An example experiment is shown in Fig. 6.3A. Here, a dual probe RPA was performed on 1 /ig of total RNA purified from cells transfected with cap tail R-luc-4 sites and F-luc mRNA, with and without miCXCR4. The assay was performed on total RNA from untransfected cells to test for specificity. The level of R-luc-4 sites mRNA was not significantly different between cells transfected with miCXCR4 (+) and those not (—). 

Brown, M., Edmonds, T., Miller, J. and Seare, N. (1993). Use of nile red as a long-wavelength fluorophore in dual-probe studies of ligand-protein interactions. J. Fluorescence 3, 129-130. 

Cecchi, M., Passani, M. B., Bacciottini, L., Mannaioni, P. F. and Blandina, P. Cortical acetylcholine release elicited by stimulation of histamine HI receptors in the nucleus basalis magnocellularis a dual-probe microdialysis study in the freely moving rat. Eur. J. Neurosci. 13 68-78, 2001. 

S. Macha and A. K. Mitra. Ocular pharmacokinetics in rabbits using a novel dual probe microdialysis technique. Exp. Eye Res. 72 289-299 (2001). 

Enrico P, Bouma M, de Vries JB, Westerink BH. 1998. The role of afferents to the ventral tegmental area in the handling stress-induced increase in the release of dopamine in the medial prefrontal cortex a dual-probe microdialysis study in the rat brain. Brain Res 779(1-2) 205-213. 

Kawahara Y, Kawahara H, Westerink BH. 1999. Tonic regulation of the activity of noradrenergic neurons in the locus coeruleus of the conscious rat studied by dual-probe microdialysis. Brain Res 823(1-2) 42-48. 

Moor E, Schirm E, Jacso J, Westerink BH. 1998. Involvement of medial septal glutamate and GABAA receptors in behaviour-induced acetylcholine release in the hippocampus a dual probe microdialysis study. Brain Res 789(1) 1-8. 

Yamamuro Y, Hori K, Tanaka J, Iwano H, Nomura M. 1995. Septo-hippocampal cholinergic system under the discrimination learning task in the rat a microdialysis study with the dual-probe approach. Brain Res 684(1) 1-7. 

DCE characterization can be conveniently carried out by H-NMR, elemental analysis, pH, and viscosity determination. The trimethyl ammonium and dimethyldodecyl ammonium content were evaluated, as well as an indirect percent nitrogen (% N), by H-NMR (Gemini 200 NMR, H/ C dual probe at 25°C, as 3.3% solutions in de-DMSO). The %N via H-NMR correlated extremely well with elemental analysis (Tables 3 and 4). 

Fig. 27 LF AFM image of a dual-probe array containing stripes of the complement (10 jjim) and control (5 xm) oligonucleotides. The length scale is 50 xm and the vertical scale is 250 mV [164]. Reprinted with permission...

Fig. 37.11. Use of an NO microsensor for detection of the NO release from cultured endothelial cells. The sensor is a dual probe microsensor. The small sensor is a bare Pt UME used to position the sensor in the feedback mode. Onto the larger Pt electrode a polymer was deposited from an acrylic resin containing Ni(4-lV-tetramethyl) pyridyl porphyrin and served as amperometric NO sensor, (a) Schematic of the sensor, (b) optical microphotograph of the sensor surface, (c) Response of the NO sensor to the stimulation of the cells with bradykinin at different distances of the sensor to the surface of the cells. Reprinted with permission from Ref. [104], Copyright 2004, American Chemical Society.

Very fast electron transfers from P+ to bacteriochlorophyl (Bchl) and from (Bchl)- to QA do not depend on media dynamics and occur via conformationally non-equilibrium states (Fig.3.18). The dual fluorophore-nitroxide molecules (D-A) are also convenient objects for analysing the activity-dynamics relationship. The marked irreversible photoreduction of the nitroxide fragment of the dual probe incorporated into the binding site of HSA only took place when the nanosecond dynamical processes around the probe traced by ESR and fluorescence methods were detected (Rubtsova et al., 1993, Fogel et al, 1994 Likhtenshtein, 1986 Lozinsky et al., 2002). Similar results were reported for another model protein system, i.e. a-chymotrypsin with spin labeled methionin-92 groups (Belonogova et al., 1997). In the latter enzyme, the excited tryptophan group serves as an electron donor. 

To investigate the effect of a protein on electron transfer and the energy conversion, the dual probes (R ) were incorporated to the hydrophobic pocket obovin serum albumin (Rubtsova et al., 1993 Vogel et al., 1994 Likhtenshtein, 1996 Lozinsky et al., 2001). Experimental temperature dependence on the rate constant of photoreduction kpr was found to be similar to that in the above-mentioned solvent. Values estimated from experiments of parameters of local molecular dynamics with the correlation frequency at... 

Aside from the obvious improvement in the s/n ratio, which arises in part from concentrating the sample from 145 to 40 pL as well as from having all of the sample in the rf coil rather than 70%, the ketone carbonyl resonance at 219.5 ppm was observed with reasonable signal intensity whereas its presence was questionable at best in the 3 mm micro-dual probe 13C spectrum shown in the top panel. The s/n ratios of the overnight acquisitions were 5.5 1 for the 3 mm micro-dual probe vs. 11 1 for the Nano-probe . There is no obvious reason why the carbonyl resonance was not observed in the 3 mm micro-dual 13C spectrum, as the relaxation delay between acquisitions was set identically in the two experiments. These data also suggest that on a per-transient basis, that the performance of the Nanoprobe is perhaps somewhat lower than that of the 3 mm micro-dual probe. This inference is based on the nearly 4-fold concentration difference between the two probe formats. Assuming probe efficiencies were identical, an s/n ratio approaching 22 1 should have been observed for the Nano-probe based on the concentration increase. 

Later in 1996 the first example of a dimeric indoloquinoline alkaloid, crypt-omisrine (22), was isolated and its structure elucidated.73 Inverse-detected 2D-NMR spectra were recorded using a 3 mm micro-inverse probe 13C chemical shift data were recorded for the sample using a 3 mm micro-dual probe. In addition to the mass spectral data, a 0.9% nuclear overhauser effect (NOE) observed between the HI and H9 protons was used to confirm the structure. 

Musser and colleagues utilized 3 mm micro-probe technology in a study reporting the identification of a new series of fumonisins containing 3-hydroxypyridine moieties (24A-C).77 A 400 MHz 3 mm micro-dual probe was used to both record 13C spectra as well as for the acquisition of HMQC and HMBC data used in the characterization of these fungal secondary metabolites. 

The extent of gas dispersion can usually be computed from experimentally measured gas residence time distribution. The dual probe detection method followed by least square regression of data in the time domain is effective in eliminating error introduced from the usual pulse technique which could not produce an ideal Delta function input (Wu, 1988). By this method, tracer is injected at a point in the fast bed, and tracer concentration is monitored downstream of the injection point by two sampling probes spaced a given distance apart, which are connected to two individual thermal conductivity cells. The response signal produced by the first probe is taken as the input to the second probe. The difference between the concentration-versus-time curves is used to describe gas mixing. 

HMQC spectra using H as the detector (/) spin can be recorded on a conventional two-chaimel NMR spectrometer with a normal broad band, or selective dual, probe head. However, better signal-to-noise will be achieved using an inverse probe head due to the better filling factor. 

Fig. 1 illustrates the automated venting system. The dual-probe unit has a long probe and a short one. When the long probe is not covered by slurry, the relay opens an automatic control valve, which vents the tank. When slurry contacts the short probe, the valve clo.ses and the venting is completed. The length differential betw een the probes determines the venting interval. 

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