Double-quantum filtered correlation

Sowinski and coworkers40 reported a structure of vacidin A (63), an aromatic hep-taene macrolide antibiotic. The constitution of vacidin A, a representative of the aromatic heptaene macrolide antibiotics, was established on the basis of 13C and H- H double quantum filtered correlated spectroscopy, rotating frame nuclear Overhauser effect spectroscopy, 7-resolved 11 as well as H-13C correlation NMR spectra. The geometry of the polyene chromophore was determined as 22E, 24E, 26E, 28Z, 30Z, 32E, 34E. 

Record the 2-D H- H double quantum filtered correlation spectroscopy (DQF-COSY) spectrum (Braun et al., 1998, pp. 481-484). 

By allowing multiple-quantum coherence to process during the evolution period of a two-dimensional experiment, Drobny et al. were able to detect its effects indirectly. This idea subsequently blossomed into the new technique of filtration through double-quantum coherence. Multiple-quantum coherence of order n possesses an n-fold sensitivity to radiofrequency phase shifts, which permits separation from the normal single-quantum coherence. This concept inspired the popular new techniques of double-quantum filtered correlation spectroscopy (DQ-COSY) and the carbon-carbon backbone experiment (INADEQUATE), both designed to extract useful connectivity information from undesirable interfering signals. 

QF-COSY 2D double Quantum Filtered Correlated SpectroscopY... 

All proton NMR spectra were recorded on a Varian Unity 600 at 25 C. 6 to 10 mg of the disulfide linked c-Myc-Max heterodimeric LZ were dissolved in 0.5 mL of potassium phosphate buffer (50 mM, 10% DiO / 90% H2O and pH 4.7) containing 100 mM KCl and ImM 2,2-dimethyl-2-silapentane-5-sulfonic acid (DSS) to yield solutions ranging from 0.75 to 1.25 mM. Proton resonances were assigned from two-dimensional double quantum filtered correlation spectroscopy (DQF-COSY (21)), two-dimensional total correlation spectrocopy (TOCSY mixing time = 50 ms (22)) and two-dimensional nuclear Overhauser enhancement spectrocopy (NOESY mixing times = 150 and 200 ms (23)) experiments. Sequential assignment of the proton resonances was performed as described by Wuthrich (24). 

Traditionally, homonuclear 2D double quantum filtered correlation spectroscopy (DQF-COSY) and total correlated spectroscopy (TOCSY) spectra are valuable in the identification of resonances of individual monosaccharide units. In the presence of small couplings, through space connectivities detected by NOESY/ROESY (nuclear Overhauser effect spectroscopy/ rotational nuclear Overhauser effect spectroscopy) experiments are also useful in completing the resonance assignment. When the H NMR spectra of complex oligosaccharides are too crowded to fully elucidate the structure by homonuclear correlation methods, it is efficient to use 2D heteronuclear correlation methods, such as heteronuclear single quantum correlation... 

DQFCOSY double-quantum-filtered correlated spectroscopy... 

DQF-COSY (double quantum filtered correlation spectroscopy) 157,158... 

Lin et al. have reported (p and angles for the sLc tetrasaccharide, determined with the aid of ROESY NMR measurements and Molecular Mechanics 2 (MM2) calculations. as NeuAc. Gal 163°, —61°, Gal, GlcNAc 48°, 15° andFuc, GlcNAc 22°, 30°. In a subsequent study from the same laboratory, Ichikawa etal. used DQF-COSY (double quantum-filtered correlation spectroscopy) and TOCSY (total correlation spectroscopy) to derive complete H and C... 

DQF-COSY Double-quantum filtered correlation spectroscopy 5.6.2... 

DQFCOSY. Double quantum filtered correlation spectroscopy. 

A new through-bond correlation method for disordered solids has been proposed. The new approach is based on the uniform-sign cross-peak double quantum filtered correlation spectroscopy experiment, which is a refocused version of the popular double quantum filtered correlation spectroscopy experiment in liquids. Its key feature is that it provides in-phase and doubly absorptive line shapes, which renders it robust for chemical shift correlation in solids. It has been shown that both theory and experiment point to distinct advantages of this protocol, which are illustrated by several experiments under challenging conditions, including fast MAS up to 30kHz, anisotropic molecular motion, and correlation spectroscopy at the natural abundance isotope level. 

HSQC) and Total Correlated spectroscopy (TOCSY) experiments. The methylene, methine and methyl (A/M and A/G) carbon resonances show both stereochemical (triad level) and compositional (dyad, triad, tetrad, pentad and hexad level) sensitivity. 2D Double Quantum Filtered Correlated Spectroscopy (DQFCOSY) experiment was used in A/B copolymers to assign the complex NMR spectrum to different compositional sequences. 

List of Abbreviations NMR, nuclear magnetic resonance O.D.260> optical density at 260 nm at 25 °C NOESY, nuclear Overhauser effect spectroscopy DQF-COSY, double quantum filtered correlation spectroscopy KP, potassium phosphate Tm, UV-melting point ER, endoplasmic reticulum PAGE, polyacrylamide gel electrophoresis TSP, trisilylpropionic acid sodium salt fid, free induction decay ffh, fifty-four-homologue j57iAf, methionine-rich domain of fifty-four-homologue. 

FIGURE 8.2. Flowchart for structure elucidation of purified compounds. DEPT Distortionless Enhancement by Polarization Transfer, HMBC Heteronuclear Multiple Bond Correlation, HSQC Heteronuclear Single Quantum Coherence, HMQC Heteronuclear Multiple Quantum Correlation, DQF-CQSY Double Quantum Filtered Correlated Spectroscopy and NOSEY Nuclear Overhauser effect spectroscopy. 

Double quantum filtered correlation (DQF-COSY) and totai correiation fTOCSY) spectroscopy... 

In principle, 2D NMR structural determination of proteins in solution involves the linking of information derived from a combination of three complementary experiments - TOCSY (Total Correlated Spectroscopy), DQF-COSY (Double-Quantum Filtered Correlated Spectroscopy) and NOESY (Nuclear Overhauser Effect Spectroscopy). The TOCSY (58) spectra are used to identify spin systems of the amino acids in the protein. COSY (59,60) spectra yield complementary information to the TOCSY, which can be used to obtain the direct scalar connectives. The NOESY (61) spectra yield information on the through space relationship of protons in the protein. It should be noted that because of the vast abundance of hydrogen atoms in a protein molecule proton NMR is the preferred technique to determine the solution structure of a protein. 

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