Correlation spectroscopy DQF-COSY

The data from H NMR studies of 63, which included double quantum filtered phase sensitive correlated spectroscopy (DQF-COSY) and rotating frame nuclear Overhauser effect spectroscopy (ROESY) experiments (Figure 12), are collected in Table 17. 

The structures of the compounds were elucidated by a combination of NMR techniques (lH-, 13C-, and 13C-DEPT NMR) and chemical transformation, enzymatic degradation, and as well as mass spectrometry, which gives information on the saccharide sequence. A more recent approach consists of an extensive use of high-resolution 2D NMR techniques, such as homonuclear and heteronuclear correlated spectroscopy (DQF-COSY, HOHAHA, HSQC, HMBC) and NOE spectroscopy (NOESY, ROESY), which now play the most important role in the structural elucidation of intact glycosides. These techniques are very sensitive and non destructive and allow easy recovery of the intact compounds for subsequent biological testing. 

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

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... 

The double quantum fdtering correlation spectroscopy (DQF-COSY) assignment, and observance of diagnostic cross-peaks between R-CH2 of the 2-aminoethyl and the CH2 adjacent to the cyanuryl residue, in the nuclear Overhauser enhancement spectroscopy (NOESY) H NMR of 376 indicated the major rotamer to be the trans-isomer, identical to that of the crystal structure (Figure 44). 

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. 

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. 

NMR spectroscopy was carried out using a Varian Unity 300MHz spectrometer. Peptides were dissolved in 500 pL of 90% H,O/10% D20 (or 100% D20) giving a sample concentration of 1-2 mM and the pH adjusted to 5.5. H DQF-COSY (double quantum filtered two-dimensional correlated spectroscopy), ROESY, and TOCSY spectra were collected at 25 °C and processed as described.1 6-281... 

The structural connectivity derived from examination of the 111, 13C/DEPT, DQF-COSY, HMQC, and HMBC data (DEPT = distortionless enhancement by polarization transfer DQF = double quantum filtering COSY = correlation spectroscopy HMQC = heteronuclear multiple quantum correlation HMBC = heteronuclear multiple bond correlation) resulted in global reevaluation of sclerophytin B structure and demonstrated that this compound and the related alcohol are not composed of two ether bridges as in the originally formulated structure 37, but share the structural features depicted as 38 <20000L1879>. Comparison of 13C and 111 NMR data of Norte s... 

H, C, and NMR chemical shifts of 10 substituted pyrazolo[l,5- ]pyrimidines 40 were assigned based on double quantum filtering (DQF) H, H correlation spectroscopy (COSY), pulsed field gradient (PFG) H, C... 

Two-dimensional NMR spectroscopy ((double quantum fdtering (DQF), correlation spectroscopy (COSY), hetero-nuclear multiple quantum correlation (HMQC), heteronuclear multiple bond correlation (HMBC)) as well as liquid secondary ionization mass spectrometry (LSI MS) and UV-Vis spectroscopies were used to establish crown structures of TTFs 33 ( =l-3). In the case of the macrocycle 33 ( = 1), two protons of each methylene group of the SCH2CH2O fragments were not identical and gave an AA BB system. This observation was in accordance with the expected low conformational mobility of the polyether bridge in ( )-33 ( = 1) as compared with (Z)-33 ( = 1). The macrocycle ( )-33 ( = 2) behaved similarly to ( )-33 ( =1), whereas the protons under discussion were equivalent in ( )-33 ( = 3) <2001CFJ447>. 

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... 

The homonudear 2-D NMR experiments that use I-coupling indude the correlation spectroscopy (COSY, and variants induding gradient-selected COSY or gCOSY, double-quantum filtered COSY or DQF-COSY) experiment, the total correlation spectroscopy (TOCSY) experiment, and the incredible natural abimdance double quantum transfer experiment (INADEQUATE) [3]. 

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