Gradient selection in inverse heteronuclear correlation spectroscopy

Willker, Wieland; Leibfritz, Dieter; Kerssebaum, Rainer; Bermel, Wolfgang

doi:10.1002/mrc.1260310315

Cited by 955 publications

(693 citation statements)

References 18 publications

Supporting

Mentioning

685

Contrasting

Unclassified

Order By: Relevance

“…The pulse sequence described previously [40] was used to record the 2D 1 H-13 C multiplicity edited HSQC experiment shown in Figure 4, by using a heteronuclear coupling constant 1 J ( 1 H-13 C) of 145 Hz and an evolution delay of 3.45 ms. This allowed the 1 H-13 C HSQC spectrum to be edited by showing the correlations due to CH/CH 3 groups and the CH 2 groups as positive and negative, respectively.…”

Section: Nuclear Magnetic Resonancementioning

confidence: 99%

Tandem mass spectrometry of poly(methacrylic acid) oligomers produced by negative mode electrospray ionization

Giordanengo

Viel

Allard-Breton

et al. 2009

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

Dissociation of small poly(methyl acrylic acid) (PMAA) anions produced by electrospray was characterized by tandem mass spectrometry. Upon collisional activation, singly, and doubly deprotonated PMAA oligomers were shown to fragment via two major reactions, dehydration and decarboxylation. The elimination of a water molecule would occur between two consecutive acid groups in a charged-remote mechanism, giving rise to cyclic anhydrides, and was shown to proceed as many times as pairs of neutral pendant groups were available. As a result, the number of dehydration steps, together with the abundance of the fragment ions produced after the release of all water molecules, revealed the polymerization degree of the molecule in the particular case of doubly charged oligomers. For singly deprotonated molecules, the exact number of MAA units could be reached from the number of carbon dioxide molecules successively eliminated from the fully dehydrated precursor ions. In contrast to dehydration, decarboxylation reactions would proceed via a charge-induced mechanism. The proposed dissociation mechanisms are consistent with results commonly reported in thermal degradation studies of poly(acrylic acid) resins and were supported by accurate mass measurements. These fragmentation rules were successfully applied to characterize a polymeric impurity detected in the tested PMAA sample. (J Am Soc Mass

show abstract

Section: Nuclear Magnetic Resonancementioning

confidence: 99%

Tandem mass spectrometry of poly(methacrylic acid) oligomers produced by negative mode electrospray ionization

Giordanengo

Viel

Allard-Breton

et al. 2009

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

show abstract

“…Two-dimensional, gradient-selected, one-bond proton-nitrogen correlation spectroscopy, HSQC (17)(18)(19), and multiple-bond proton-nitrogen correlation spectroscopy, HMBC (20,21) were recorded in the phase sensitive mode (HSQC) or the absolute value mode (HMBC). The HSQC pulse sequence included the TANGO block to suppress signals from N14-coupled protons (22) and 15 N-decoupling during proton acquisition, using a 2.1 kHz field strength and the GARP decoupling scheme (23).…”

Section: Synthesis Of Model Compoundsmentioning

confidence: 99%

“…The list of compounds and relevant equations are listed in Scheme 2. One-and two-dimensional NMR spectra were acquired at 25 °C using a Varian INOVA NMR spectrometer (Varian Inc., Palo Alto, CA) operating at a proton frequency of 499.9 MHz and equipped with either a 5 mm triple resonance HCN z-gradient probe or a 5 mm dual broadband z-gradient probe.Direct 15 N observation was achieved by DEPT (16), taking advantage of the 90 Hz one-bond NH coupling of N1-methyl-4-aminopyrimidinium iodide.Two-dimensional, gradient-selected, one-bond proton-nitrogen correlation spectroscopy, , and multiple-bond proton-nitrogen correlation spectroscopy, HMBC (20,21) were recorded in the phase sensitive mode (HSQC) or the absolute value mode (HMBC). The HSQC pulse sequence included the TANGO block to suppress signals from N14-coupled protons (22) and 15 N-decoupling during proton acquisition, using a 2.1 kHz field strength and the GARP decoupling scheme (23).…”

mentioning

confidence: 99%

Electronic and Nuclear Magnetic Resonance Spectroscopic Features of the 1‘,4‘-Iminopyrimidine Tautomeric Form of Thiamin Diphosphate, a Novel Intermediate on Enzymes Requiring This Coenzyme

2006

View full text Add to dashboard Cite

Appropriate compounds were synthesized to create models for the 1',4'-imino tautomer of the 4'-aminopyrimidine ring of thiamin diphosphate recently found to exist on the pathway of enzymatic reactions requiring this cofactor (Jordan, F., and Nemeria, N.S. (2005) Bioorganic Chemistry, 33, 190−215). The N1-methyl-4-aminopyrimidinium compounds synthesized on treatment with a strong base produce the 1,4-imino tautomer whose UV spectrum indicates a maximum between 300−320 nm, depending on the absence or presence of a methyl group at the 4-amino nitrogen. The λ max found is in the same wavelength range as the positive circular dichroism band observed on several enzymes and showed a very strong dependence on solvent dielectric constant. To help with the 15 N chemical shift assignments, the model compounds were specifically labeled with 15 N at the amino nitrogen atom. The chemical shift of the amino nitrogen was deshielded by N1-methylation, then dramatically further deshielded by more than 100 ppm on formation of the 1,4-iminopyrimidine tautomer. Both the UV spectroscopic values and the 15 N chemical shift for the 1,4-iminopyrimidine tautomer should serve as useful guides to the assignment of enzyme-bound signals.The notion that the 4'-aminopyrimidine group of thiamin diphosphate (ThDP) undergoes tautomerization to the 1',4'-imino form (1',4'-iminoThDP) during the catalytic cycle of enzymes that utilize it has gained wider acceptance since the appearance of X-ray crystal structural data (1). The role and likelihood of tautomerization is suggested by two totally conserved structural features on all ThDP enzymes: (a) the V coenzyme conformation ensuring that the C2 thiazolium atom and the N4' atom of the 4'-aminopyrimidine ring are within less than 3.5Å from each other (2), potentially enabling the 1',4'-imino tautomer to participate in proton transfers; and (b) the presence of a glutamate within hydrogen bonding distance of the N1' atom of the 4-aminopyrimidine ring, as a potential catalyst for the tautomerization (Scheme 1, as exemplified with the reaction of yeast pyruvate decarboxylase, YPDC). As illustrated in the active site structure of YPDC in Figure 1, the residue E51 probably carries out this function (3). Chemical evidence for the importance of the 4'-aminopyrimidine moiety of ThDP in catalysis was obtained from ThDP analogues in which one or another nitrogen atom was replaced by carbon (4), while a model for activation of the ring for catalysis via tautomerization by N1-protonation was suggested from our laboratories (5-7). Notwithstanding the attractive features of this hypothesis, until recently no direct spectroscopic or structural evidence was available on any ThDP enzymes for the presence of the 1',4'-imino tautomer. In rapid-scan stopped flow experiments, mixing slow active-center variants of YPDC with pyruvate, a UV # Supported by National Institutes of Health grants GM050380 and GM062330. In these examples, the keto group of the substrate analog phosphonate forms a covalent adduct with the t...

show abstract

“…The syntheses of (2R)-2-hydroxy-3-methylbutanoic acid (56) and N-methyl-L-valine (N-Me-Val) (57) The synthesis of (2S,3S,4R)-3,4-dihydroxy-3-methylproline was achieved by adapting Sardina's synthesis of a structurally related triol (165). Despite the previous report, extensive optimizations were required to reproduce the MOM protection of the …”

Section: L-proline Cis-4-hydroxy-l-proline and Trans-4-hydroxy-l-promentioning

confidence: 99%

Total Synthesis of Depsilairdin

Ward

Pardeshi

2010

J. Org. Chem.

View full text Add to dashboard Cite

The total synthesis of depsilairdin, a host-selective phytotoxin isolated from Leptosphaeria maculans (the causal agent of blackleg disease of oilseed Brassicas), has been achieved by N-terminal extension of a suitably protected derivative of the hitherto unknown amino acid (2S,3S,4R)-3,4-dihydroxy-3-methyl-proline (Dhmp) followed by esterification with lairdinol A. The latter esterification, complicated by the sterically hindered nature of the carboxyl group, was accomplished by a novel method involving reaction of the 1-hydroxybenzotriazole (HOBt) derived active ester with the bromomagnesium alkoxide of lairdinol A. Three depsilairdin analogues were also prepared by replacing the Dhmp residue with L-proline and cis-and trans-4-hydroxy-L-proline. Phytotoxicity assays showed that the analogues were nontoxic to both blackleg-susceptible (brown mustard) and -resistant (canola) plants, suggesting that the presence of the Dhmp residue in depsilairdin is important for its host-selective toxicity toward brown mustard.

show abstract

Gradient selection in inverse heteronuclear correlation spectroscopy

Cited by 955 publications

References 18 publications

Tandem mass spectrometry of poly(methacrylic acid) oligomers produced by negative mode electrospray ionization

Tandem mass spectrometry of poly(methacrylic acid) oligomers produced by negative mode electrospray ionization

Electronic and Nuclear Magnetic Resonance Spectroscopic Features of the 1‘,4‘-Iminopyrimidine Tautomeric Form of Thiamin Diphosphate, a Novel Intermediate on Enzymes Requiring This Coenzyme

Total Synthesis of Depsilairdin

Contact Info

Product

Resources

About