Cross-peaks ’fingerprints

Figure 3. Fingerprint region of the COSY spectrum of RpII in H O showing the amide to a proton connectivities. Cross peaks are labeled with the identity of the amino acid in the sequence from which they arise.

Fig. 30. TOCSY (A,B) and HNHA-TACSY (C,D) spectra of the peptide Gln-Lys-Leu-Glu-Ala-Met-His-Arg-Gln-Lys-Tyr-Pro are shown for mbdng times of 45 (A, C) and 85 (B, D) ms. The expansions show the region (0.75 ppm 6, < 4.85 ppm, 7.43 ppm < 62 8.38 ppm) that contains the (H, H ) fingerprint signals as well as the cross-peaks between and side chain protons. The experimental TOCSY sequence was DIPSI-2 with = 5 kHz and the HNHA-TACSY sequence was CABBY-1 with — 2.661 kHz. At a spectrometer frequency of 400 MHz with the carrier at 6.15 ppm, the range of offsets and Vj l is region is —2.156 kHz < —0.516 kHz and 0.520 kllz < i>2 < 0.9 kHz. The...

Fig. 22. Fingerprint regions of 2D TOCSY spectra of angiotensin (0.7 mM in 90 10 HaOrHaO, pH 7.0) at 298 K acquired at 500 MHz. (A) TOCSY with presaturation, (B) basic TOCSY-WATERGATE and (C) flip-back TOCSY-WATERGATE. There is considerable bleaching of cross-peaks near the water frequency in (A). Spectrum (B) is cleaner with some cross-peaks visible at the water frequency. TTie ffip-back TOCSY-WATERGATE (C) has improved suppression with increased intensity of many of the cross-peaks. (From Fulton et al. with permission.)...

It is clear that the unmistakable resonance fingerprint provided by a narrow Lorentzian peak in the integral cross section (ICS) will be rare for reactive resonances in a collision experiment. However, a fully resolved scattering experiment provides a wealth of data concerning the reaction dynamics. We expect that the state-to-state differential cross sections (DCS) as functions of energy can be analyzed, using various methods, to reveal the presence of reactive resonances. In the following subsections, we discuss how various collision observables are influenced by existence of a complex intermediate. Many of the resonance detection schemes that have been proposed, such as the use of collision time delay, are purely theoretical in that the observations required are not currently feasible in the laboratory. Nevertheless, these ideas are also discussed since it is useful to have method available... 

Bonding electrons are also photoemitted and these appear in the valence band between, say 0-30 eV BE. Emission from many closely spaced levels with different cross-sections gives rise to a complex spectrum, often rich in structure, which in principle contains more direct structural information than the core level peaks. The spectrum is rather low in intensity (typically only a few percent that of major core lines) but with higher power instruments it is routinely accessible. The fingerprint utility of the valence band is increasingly being augmented by full interpretations based on theoretical calculations. 

That an NMR spectrum of an organic solid can exhibit more peaks than there are unique chemical sites in the molecule raises the issue of how to assign the spectrum. Peak assignments may not be necessary if only a simple fingerprint is required, but confirmation of which peak corresponds to which nuclear site is essential before proceeding with more detailed characterization. To assist the assignment process, methods that vary the phases of cross-... 

---