Triple resonance spectra

Figure 3 Special TRIPLE resonance spectra of the primary donor radical-cation P in the bRC of R. sphaeroides wild type and mutant HE(M202) (His - Glu) and of monomeric BChl a " in organic solvents, all spectra in isotropic solution. The isotropic hfcs are directly obtained from the special TRIPLE frequency nSJ = Ais,J2.H The oxidation potential of the primary donor is also given (vs. NHE). Adapted from reference 68.

F, H, triple-resonance spectra. [Figure reproduced from Ref. 83.]... 

Rovnyak D, Frueh DP, Sastry M, Sun ZYJ, Stem AS, Hoch JC, Wagner G (2004) Accelerated acquisition of high resolution triple-resonance spectra using non-uniform sampling and maximum entropy reconstruction. J Magn Reson 170 15-21... 

Moseley HNB, Riaz N, Aramini JM, Szyperski T, Montelione CT (2004) A generalized approach to automated NMR peak list editing application to reduced-dimensionality triple resonance spectra. J Magn Reson 170 263-277... 

Schmieder P, Stem AS, Wagner G, Hoch JC (1994) Improved resolution in triple-resonance spectra by nonlinear sampling in the constant-time domain. J Biomol NMR 4 483 90... 

We have shown previously that the resolution of triple resonance experiments can be dramatically enhanced with random NUS in the indirect dimensions, and high-resolution 3D or 4D triple-resonance spectra of large proteins can be recorded within a few days, which would otherwise require months of instrument time with US [32, 35]. This works rather well with triple resonance experiments where peaks have similar intensities and there is not much of a sensitivity and dynamic range issue. In fact, if there are primarily strong signals, such as methyl peaks in ILV labeled samples, a straight Fourier transformation of the NUS data where the... 

Application to TRIPLE resonance spectra of the chlorophyll a cation radical, J. Magn. Res. 84 537 (1989). 

McFarlane and Rycroft (241) have determined the spin-spin coupling constant in the Cu[P(OCH3)3]4 ion on the basis of the INDOR spectrum which is found to be a faithful reproduction of the direct P spectrum, consisting of two partly overlapping 1 1 1 1 quartets whose splittings of 1210 Hz and 1290 Hz correspond to J( Cu- P) and J( Cu- P). By simultaneously irradiating one of the components of the Cu quintet a triple resonance spectrum referred to as MINDOR (modified INDOR) is obtained from which the Cu resonance frequency can be determined. 

Xemr is an (ESR) EPR (Electron Paramagnetic Resonance), ENDOR (Electron Nuclear DOuble Resonance), and TRIPLE (electron-nuclear-nuclear TRIPLE resonance) spectrum manipulation and simulation package written for Linux systems. It should be noted that Xemr does not run under Microsoft DOS/Windows environments and the porting would currently be a rather lengthy task. Xemr source and binary code is distributed under the GNU General Public License. 

While the CA and CO secondary chemical shifts cannot be determined using conventional triple-resonance experiments that employ the H-15N correlation spectrum, incorporation of individual... 

ESR methods unambiguously establishes the presence of species bearing unpaired electrons (ion-radicals and radicals). The ESR spectrum quantitatively characterizes the distribution of electron density within the paramagnetic particle by a hyperfine structure of ESR spectra. This establishes the nature and electronic configuration of the particle. A review by Davies (2001) is highly recommended as a guide to current practice for ESR spectroscopic studies (this quotation is from the title of the review). The ESR method dominates in ion-radical studies. Its modern modifications, namely, ENDOR and electron-nuclear-nuclear triple resonance (TRIPLE) and special methods to observe ion-radicals by swiftness or stealth are described in special literatures (Moebius and Biehl 1979, Kurreck et al. 1988, Werst and Trifunac 1998). 

Figure 2.10 (a) 2D H- N HETCOR correlation spectrum of fully N-labeled complex [(=SiO)2Ta(=NH) (NHj)] and [=Si- NH2] and comparison with 2D double quantum (b) and triple quantum (c) correlation spectra. An exponential line broadening of 100 Hz was applied to all the proton dimensions before Fourier transform. The dotted gray lines correspond to the resonances of the tantalum NH, NH2 and NH3 protons. The dotted circles underline the absence of auto-correlation peaks for the imido proton in the double quantum spectrum (b), and for the amido proton in the triple quantum, spectrum (c) (from Reference [9]). 

Almost all spectra were acquired on a AMX-600 Bruker NMR spectrometer equipped with a 5 mm inverse broad-band probe. The only exception were the gradient-enhanced spectra acquired on an INOVA-600 Varian NMR spectrometer using a 5 mm triple-resonance probe with z gradients. The experimental details are given for each spectrum in the figure captions. 

Because of the inherent non-planar structure of helicenes it seemed of interest to examine the spin distribution in helicene radical anions. For the mono anion of hexahelicene a set of 8 hyperfine splitting constants (hfsc s) and 38 = 6561 ESR lines can be expected. Such a spectrum will be poorly resolved. Indeed, it was not possible to determine hfsc s from the ESR-spectrum of hexahelicene 132). Using the ENDOR technique which reduces the amount of lines the eight hfsc s could be deduced, however, and the relative signs could be determined l33) by the triple resonance technique. 

FIGURE 40. 29Si detected 29Si— 13C correlated 2D spectrum enhanced by 1H—- Si INEPT (50% solution of polymer silicon oil in CD3COCD3 triple resonance probe with 1H inner coil double tuned to 13C frequency, 64 increments with 128 scans each, 1024 data points in F2 relaxation delay 3 s, d = 7 111s and A = 30 ms). Reproduced by permission of Academic Press from Reference 297... 

Fig. 20. Experimental setup for applications of the SPECIFIC CP experiment in the context of triple-resonance solid-state NMR experiments. After an initial broadband adiabatic CP step from protons to the I nuclei, SPECIFIC transfer to the observed 5 nucleus occurs during the mixing time tm. The resulting signal represents a dipolar and chemical shift-filtered spectrum and can be controlled by variation of the carrier frequencies and the radiofrequency during the SPECIFIC transfer. A conventional HETCOR experiment is obtained by the introduction of an evolution time t. (Adapted from Baldus et al.215 with permission.)...

Another method that is important for structure assignment is the electron-nuclear-nuclear triple resonance (TRIPLE) spectroscopy (Endeward et al., 1998 Makinen et al., 1998), which is an extension of the ENDOR method. In the general TRIPLE experiment, transitions of different nuclei are driven simultaneously. One ENDOR transition is irradiated saturating rf power at a constant frequency, while the entire ENDOR frequency range is swept to obtain the TRIPLE spectrum. 

Fig. 5. HMQC spectrum of a 0.55 pmol sample of cryptolepine (1) dissolved in 30 pL d6-DMSO. The data were acquired in a 25.5 h experiment using a 1.7 mm gradient triple resonance submicro-NMR probe at 600 MHz. The minor correlation responses in the spectrum designated by arrows are an 8% ( 12pg) impurity of cryptolepine A-oxide present in the sample. All of the impurity responses were visible in a 12 h contour plot. Full HMBC data consistent with the structure were acquired for the impurity in 55 h. (Reprinted with permission from Ref. 12. Copyright 1998, American Chemical Society and American Society of Pharmacognosy.)...

Fig. 11. Eight transient 500 MHz H-NMR spectra of an 11.9 pg (0.027 pmol) sample of the antibiotic clindamycin (7) prepared in 500 pL of CDC13 in a 5 mm NMR tube (top trace) 292 pL in a 4mm tube (middle trace) and 163 pL in a 3 mm tube (bottom trace). All data were acquired using a 500 MHz 5 mm gradient inverse triple resonance Varian Cold-probe . The s/n ratio was measured for each spectrum using a 200 Hz region of representative noise downfield of the anomeric proton resonating at 5.3 ppm. The s/n ratios were 14.4 1, 20.8 1, and 21.5 1 for the 5, 4, and 3mm tubes, respectively.

Fig. 15. Comparison of HMBC spectra for a 20 gg sample of retrorsine (3) dissolved in 150 pL rf4-metlianol in a sealed 3 mm NMR tube. The data shown in both panels are 8 Hz optimized non-gHMBC spectra. The spectrum shown in Panel A was acquired in 15 h using a 5 mm 500 MHz cryogenic gradient inverse triple resonance. Almost all of the expected resonances are observed when these data are compared to those for a 700 pg sample of 3 shown in Fig. 2. In contrast, the spectrum shown in Panel B, which was acquired with identical conditions using a 3 mm gradient inverse triple resonance probe, shows the most prominent responses in the spectrum and only a relatively small number of the other responses expected. For a sample of this size to yield a useful HMBC spectrum, it would be necessary to acquire data for a weekend when using a conventional 3 mm NMR gradient inverse-detection NMR probe.

Many workers have in fact used density matrix methods for the calculation of line shapes and intensities in multiple resonance experiments, and two excellent reviews of the background theory are available. (49, 50) In addition there is also a simple guide (51) to the actual use of the method which is capable of predicting the results of quite elaborate experiments. Major applications have included the calculation of the complete double resonance spectrum from an AX spin system which gives 12 transitions in all (52) an extremely detailed study of the relaxation behaviour of the AX2 systems provided by 1,1,2-trichloroethane and 2,2-dichloroethanol (53) the effects of gating and of selective and non-selective pulses on AB and AX spin systems and the importance of the time evolution of the off-diagonal elements of the density matrix in repetitively pulsed FT NMR and spin-echo work (54) the use of double resonance to sort out relaxation mechanisms and transient responses (55) the calculation of general multiple resonance spectra (56) and triple resonance studies of relaxation in AB and AX spin systems. (57)... 

C, Li3 spin systems). The HMQC experiment, which also allows a straightfoward determination of the involved C, Li coupling constants, is especially easy to perform with a triple resonance probehead which has, aside from the H and the lock channel, a fixed frequency for and a variable X frequency (see Chapter 2). It is of interest to note that Li, C cross peaks can also be observed in cases where the corresponding Li, C coupling is not resolved in the ID spectrum [14]. An example for an experiment using sequence (v) is shown in Figure 14 with the spectrum of isopropyllithium, where in hydrocarbon solvents solvation leads to the formation of tetramers and hexamers [76]. 

---