Proton nuclear activation

Perhaps surprisingly for such an abundant element, reference levels in biological fluids have not been determined. Versieck and Comelis [7] found only one recent study [8] of Ti in serum from healthy individuals, but consider the reported value of 90 p,g/liter, determined by proton nuclear activation, to be highly questionable and likely to arise from a failure to consider contamination and sampling problems. 

As examples of Ti measurements, the application of ICP-atomic emission spectrometry to the analysis of bone [14], of proton nuclear activation (PNA) to serum [8], and of particle-induced X-ray emission (PIXE) to lung tissue [15] are described in Sec. 4.2. The authors of these studies report measurements at the level of 0.2-0.5 p.g/g in bone, 10 xg/g in lung, and 90 p.g/liter in serum. However, it must be stressed that there is insufficient comparative data to coimnent on the accuracy of these results. Further, these were all multielement investigations and sampling procedures were not specific to Ti. 

Silver M, Howarth OW, Kelly DP. 1976. Rhodanese from Thiobacillus A2 determination of activity by proton nuclear magnetic resonance spectroscopy. J Gen Microbiol 97 285-8. 

Use of an integrated system incorporating CCC separation, PDA detector, and LC-MS proved to be a valuable tool in the rapid identification of known compounds from microbial extracts.6 This collection of analytical data has enabled us to make exploratory use of advanced data analysis methods to enhance the identification process. For example, from the UV absorbance maxima and molecular weight for the active compound(s) present in a fraction, a list of potential structural matches from a natural products database (e.g., Berdy Bioactive Natural Products Database, Dictionary of Natural Products by Chapman and Hall, etc.) can be generated. Subsequently, the identity of metabolite(s) was ascertained by acquiring a proton nuclear magnetic resonance ( H-NMR) spectrum. 

In order to characterize the active site structure of Ca ATPase from sarcoplasmic reticulum, we have employed Gd + as a paramagnetic probe of this system in a series of NMR and EPR investigations. Gadolinium and several other lanthanide ions have been used in recent years to characterize Ca + (and in some cases Mg2+) binding sites on proteins and enzymes using a variety of techniques, including water proton nuclear relaxation rate measurements (35,36,37), fluorescence (38) and electron spin resonance (39). In particular Dwek and Richards (35) as well as Cottam and his coworkers (36,37) have employed a series of nuclear relaxation measurements of both metal-bound water protons and substrate nuclei to characterize the interaction of Gd + with several enzyme systems. 

Let us finally also mention here the results of proton nuclear relaxation time 7 measurements on TEA(TCNQ)2 [53,54], From the frequency dependence of 7, it is deduced that the spin motion is a nearly one-dimensional diffusion. Moreover, the temperature dependence of the on-chain spin diffusion rate shows a quite remarkable feature while it is thermally activated below 220 K, it suddenly becomes temperature independent above 220 K. 

Hamburger M, Slacanin 1, Hostettmann K et al (1992) Acetylated saponins in mollusciddtd activity from Sapindus rarak unambiguous structure determination by proton nuclear magnetic resonance and quantitative analysis. Phytochem Anal 3 231-237 Hart KJ, Yanez-Ruiz DR, Duval SM et al (2008) Plant extracts to manipulate rumen fermentation. Anim Feed Sci Technol 147 8-35... 

Fleckenstein et al. (1960) have used a similar method to follow the turnover rates of 0 -labeled phosphate in muscle. ATP, creatine phosphate, and inorganic phosphate were separated by paper chromatography, eluted onto a platinum plate, and bombarded with 4 Mev protons. The activity of F formed is measured by an Nal scintillation counter, 2 hours after the end of bombardment. Nevertheless some difficulties were experienced due to nuclear side reactions, including activation of the platinum. The amount of can be calculated from the flux and the length of bombardment (see original paper), or may be determined by comparison with monitor foils with known concentrations of oxygen-18-labeled phosphate. 

All the techniques discussed here involve the atomic nucleus. Three use neutrons, generated either in nuclear reactors or very high energy proton ajccelerators (spallation sources), as the probe beam. They are Neutron Diffraction, Neutron Reflectivity, NR, and Neutron Activation Analysis, NAA. The fourth. Nuclear Reaction Analysis, NRA, uses charged particles from an ion accelerator to produce nuclear reactions. The nature and energy of the resulting products identify the atoms present. Since NRA is performed in RBS apparatus, it could have been included in Chapter 9. We include it here instead because nuclear reactions are involved. 

As active substances are separated and purified they are characterized by a combination of spectroscopic analyses and chemical correlations. Particularly useful spectroscopic analysis techniques are nuclear magnetic resonance (proton and carbon), mass spectrometry and Infra-red and ultraviolet spectrophotometry. 

Protons are easily detached from the furan nucleus, especially when some activating group is present. Even the carbonate ion will catalyze the deuter-ation of position 5 in 2-furoic acid salt.177 And 40% NaOD in D20, will catalyze the replacement of all the nuclear protons giving the fully deuterated product. The acid can be converted into d4-furan by treatment with mercury salts, and then DC1.178 For general synthetic purposes it is now usual to obtain nuclear carbanions by lithiation as described in Section IV. 

Assignment of the isotropically shifted signals observed for the CuNiSOD example discussed in the previous paragraph has been achieved by means of anion titrations (not discussed here) and nuclear Overhauser enhancement spectroscopy (NOESY), to be discussed next. In Figure 3.24B the CuNiSOD active site is depicted with histidine nitrogens and protons identified for the discussion of the NOESY results. The copper(II) ion is coordinated to the N ligand atoms of his46... 

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