Probe technology

This new structure determination scheme has been termed PANACEA (parallel acquisition NMR, an all-in-one combination of experimental applications) and is outlined in Section 8.3. 

Advances in NMR technology have allowed researchers to identify molecules using only very small quantities of material. However, working with minuscule amounts of sample presents additional challenges. For 5 mm cryoprobes, the volume of solvent can be critical and typical deuterated solvents result in large solvent peaks that can negatively affect two-dimensional (2D) spectra. 

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Group II assays consist of those monitoring cellular second messengers. Thus, activation of receptors to cause Gs-protein activation of adenylate cyclase will lead to elevation of cytosolic or extracellularly secreted cyclic AMP. This second messenger phosphorylates numerous cyclic AMP-dependent protein kinases, which go on to phosphorylate metabolic enzymes and transport and regulatory proteins (see Chapter 2). Cyclic AMP can be detected either radiometrically or with fluorescent probe technology. 

Over the past years, synthetic base-modified nucleosides and nucleotides have displayed important impact in diverse fields. Their biological properties have found application as antiviral tools against hepatitis virus (HBV), herpes virus (VZV) and human immunodeficiency (HIV).94,95,136 Many of those compounds exhibit antiproliferative, antibiotic and antifungal activities and some have been used as probes for DNA damages96,97,137 as well as in the anti-sense approach and DNA-probe technology with fluorescence properties.99... 

E. Rhodes, C. E. Dickerman, C. W. Peters, Associated-Particle Sealed-Tube Neutron Probe for Characterization of Materials, ANL/B-E/CP-78949, Active Probe Technologies Conference on International Symposium on Substance Identification Technologies, 4—8 October 1993, Innsbruck, Austria. 

The methanol solution containing the colored impurity was bright red and provided the feedstock used for preparative chromatographic isolation of the unstable, colored impurity, which had a half life of about 18 h in methanol and <10 m in acetone. Using a 1.7-mm 600-MHz SMIDG probe, which was the most sensitive probe technology routinely available when this work was done in 1999 [49, 59], a sample was prepared and a data set consisting of a proton reference... 

Wolfender et ah, and this coupled technique is treated more comprehensively in Chapter 1. The LC-NMR technique is by nature rather insensitive however, high-field magnets and recent improvements in solvent suppression, pulse field gradients, and probe technology have made it possible to achieve useful results on various flavonoid struc-tures. The detection limit with a 60 p.1 cell in a 500 MHz instrument for a compound with a molecular weight of around 400 amu may typically be around 20 p.g, and the information provided is hitherto mainly based on NMR spectra or correlation experiments. 

The evolution of lasers and detectors has enabled Raman spectra of high signal-to-noise ratio to be acquired in shorter time frames with lower laser powers, thus opening up new possibilities for Raman spectroscopic analysis of biological samples. Some applications have evolved to the point that it is no longer necessary to excise out the sample and bring it to the spectrometer for analysis. Rather, with fibre-optic probe technology, it is now possible... 

Fiber optic sensors are an alternative to thermocouples as embedded temperature distribution mapping sensors. As described in Section 2.2.7, McIntyre et al.104 developed two distinct fiber optic temperature probe technologies for fuel cell applications (free space probes and optical fiber probes). Both sensor technologies showed similar trends in fuel cell temperature and were also used to study transient conditions. 

Since investigators continuously strive to extract increasing amounts of data from shrinking sample sizes, much commercial and academic research on NMR hardware focuses on optimizing RF probe sensitivity to allow the analysis of trace materials. Significant advances have been achieved through several distinct modifications of instrumentation. This present chapter provides a review of the characterization of nanoliter volumes via static NMR spectroscopy and emphasizes some of the more relevant developments in probe technology that have enabled such measurements. 

An overview of the basic operation of a STM and of STM of silicon surfaces has been presented. In particular, as scanning probe technology continues to improve it has been shown that it is possible to not only image surfaces with atomic-resolution, but to controllably place and manipulate atoms... 

We notice that the S/N grows proportionately to Vns, where ns is the number of scans or repetitions of the pulse program. This relationship is not typically a problem with H experiments where only a few pg to a mg of material is enough to get good S/N in a few scans. As mention previously, l3C is 6000 times less sensitive than H, and therefore requires either more sample (N), higher field strengths B0 (or better probe technology, i.e., a cryo-probe), or an increase in the number of scans (ns). 

With these features, 33S is one of the most difficult nuclei to detect by NMR. However, the increasing availability of high-field NMR spectrometers and the development of hardware and probe technology can partly facilitate its detection. 

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