DNP method

Figure 2.4. Survey of the structures of TMI hosted in various zeolite- and silica-derived clusters as a function of the electron configuration obtained by VWN/DNP method (after [37]).

Figure 2.20. Transformation of silica supported dinitrosyl complexes of nickel(II) leading to formation of nitrogen dioxide and its final stabilization on the support. The picture shows the molecular structure and the spin density contours calculated with BP/DNP method of the involved species, and evolution of the X-band EPR spectra of the NiN02 Si02 complex due to spillover of the ligand (adopted from [71]).

Large-amplitude ( normal ) pulse voltammetry techniques were introduced in Chapter 3. The differential normal pulse (DNP) method combines several features of both the small- and large-amplitude pulse techniques. This technique is normally performed at a DME and is actually a form of polarography. The... 

Oxidative hydrolysis of BLM A2 with N-bromosuccinimide (NBS) gives tetrapep-tide S which consists of I, III, VI and VII. The N-terminal was III as determined by Sanger s DNP-method. Thus, the sequence of all amine components of BLM A2 has been determined. 

All structural information on BLM described above can be assembled as shown in Fig. 4. The results of N- and C-teiminal group analyses of BLM are only a-DNP-V, but neither nor di-DNP-V, was isolated by Sanger s DNP-method, and no free car-boxy group was detected by Koshland s glycine condensation method24). Potentio-metric titration of BLM B2, which was most easily purified among natural BLMs, shows that there are four basic groups at pKa > 11.5,7.4,4.7 and 2.7. The pKa >... 

Finally, ONP may be achieved with the aid of applied electromagnetic (i.e., radiofrequency, rf or microwave, mw) fields (c), and thus can most simply be considered as extensions of conventional DNP methods these approaches are referred to as radio-frequency induced ONP (RFONP) and microwave-induced ONP (MIONP), respectively. In conventional DNP, magnetization from thermally polarized electron spins (residing, for example, in permanent paramagnetic centers) is driven via hyperfine interactions to surrounding nuclei using resonant or near-resonant AC fields. More specifically, this process is governed by the conventional Overhauser effect in the case of dynamic hyperfine interactions (e.g., in metals or semiconductors),... 

The DNP method (p. 5) may also be used for the identification of the A-terminal residues in peptides. It is rather more laborious than the above deamination procedure, but the results are usually more clear-cut. Two methods are available. Either the terminal DNP amino acid is identified by chromatography or the remaining unsubstituted amino acids are identified by paper chromatography. The former method has the advantage that it may be carried out quantitatively but requires rather more material than is usually available from the elution of one paper chromatogram. 

Middlebrook (1949) investigated the Al-terminal residues by the DNP method and found rather a complex mixture, which would seem to be a further indication of the heterogeneity of wool. 

The DNP method showed the presence of four i f-terminal residues two of which were glycine and two phenylalanine (Sanger, 1945). From a study of the action of carboxypeptidase on insulin Lens (1949) found that free alanine was liberated before any other free amino acids, indicating the presence of alanine in the C-terminal position. Using their respective methods of reduction of the free carboxyl groups to alcohol... 

Using the DNP method it has been shown that ovalbumin has no A -terminal residue (Desnuelle and Casal, 1948 Porter, 1950a). Either the amino groups at the end of the chains are masked by the carbohydrate moiety or the protein contains one or more cyclopeptide units. 

In addition to the DNP methods described above, laser-polarized xenon can be used for the development of NMR and MRI techniques, and it is possible to enhance the nuclear spin polarization of gaseous xenon by four to five orders of magnitude. More details of this technique can be found in [86, 87]. 

New DNP methods should be able to overcome the limitation of the very short lifetime of the hyperpolarization, and should be integrated into the currently available solid-state and liquid-state NMR experiments. 

The N-terminal amino acids are generally determined by the fluorodinitrobenzene method (DNP method, Sanger s reagent) ... 

The N-terminal amino acid residues of normal adult hemoglobin A quantitative study of certain aspects of Sanger s DNP-method. J. Am. Chem. Soc. 79 (1957) 609—615. (Herbert S. Rhinesmith, W. A. Schroeder, and Linus Pauling). 

The number of arginine residues was estimated more precisely by independent analyses in which the molar ratio, amino terminus (DNP method) Pro (Chinard, 1952, for the hydrolyzate) Arg (Sakaguchi, 1951, for the hydrolyzate) was determined as 1.00 2.00 20.9. 

A rechromatographed specimen of clupeine YII obtained unmodified by the chromatographic fractionation of TNP-(trinitrophenylated) whole clupeine (cf. Chap. VII. B. 3), has the molecular formula Arg2o Pro3 Ala2 2 Val2. This is based on the analysis of amino-acid composition and a molecular weight of about 5,000 for the hydrochloride as estimated by the DNP method (MW calculated from the amino acid composition 4,047 as a free base or 4,777 as the hydrochloride). 

The focus of this review is on DNP methods with applications in liquids. This includes dissolution DNP, which is of course strictly a solid-state polarization method although targeted towards NMR spectroscopy or imaging in the liquid state. 

Interest in paramagnetism in NMR has recently experienced an additional impulse due to the advent of high-field dynamic nuclear polarization (DNP) methods. The sensitivity of NMR poses a major barrier to the stmctural characterization of... 

---