Nitrogen-15 nuclear magnetic resonance spectroscopy. Effects of hydrogen bonding and protonation on nitrogen chemical shifts of pyrazoles

Schuster, Ingeborg I.; Dyllick-Brenzinger, Christina; Roberts, John D.

doi:10.1021/jo01325a003

Cited by 40 publications

(14 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The standard one-dimensional CP/MAS pulse sequence" was used. General recording parameters were quadrature detection, 'H 90" pulse duration 5 ps, C P times [8][9][10][11][12][13][14][15] …”

Section: Methodsmentioning

confidence: 99%

¹⁵N NMR chemical shifts of NH‐pyrazoles in the solid state and in solution at low temperature

Aguilar‐Parrilla

Männle

Limbach

et al. 1994

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

“…The standard one-dimensional CP/MAS pulse sequence" was used. General recording parameters were quadrature detection, 'H 90" pulse duration 5 ps, C P times [8][9][10][11][12][13][14][15] …”

Section: Methodsmentioning

confidence: 99%

¹⁵N NMR chemical shifts of NH‐pyrazoles in the solid state and in solution at low temperature

Aguilar‐Parrilla

Männle

Limbach

et al. 1994

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

“…The chemical shift values of the detected nitrogen nuclei are in good agreement with literature data reported for unsubstituted pyrazole measured in DMSO (-79.8 and -173.1 ppm for N2 and N1, respectively), where the pyrazole NH proton location is known to be fixed. [40][41][42] The chemical shifts of the quaternary carbon atoms were likewise assigned on the basis of literature comparison with unsubsituted pyrazole dissolved in DMSO [43] or in hexamethylphosphoramide (HMPA), [44] 3,5-bis(methyl)-1H-pyrazole in HMPA [44] or the solid state, [45] and 3,5-bis(ethyl)-1H-pyrazole in the solid state, [46] where the NH protons are once again localized in each system.…”

Section: Prototropymentioning

confidence: 99%

Improved Synthesis and Detailed Characterization of a Hybrid Pyrazole‐TACN Dinucleating Ligand

Dalle

Dechert

Meyer

2015

Zeitschrift anorg allge chemie

View full text Add to dashboard Cite

Abstract. An improved synthetic procedure is reported for the hybrid ligand HL, composed of two TACN macrocycles bridged by a central pyrazole moiety. Detailed NMR spectroscopic characterization showed that asymmetry in this dinucleating organic scaffold can be induced at room temperature through the use of anhydrous conditions, owing to pyrazole-NH prototropy. Thermally induced line broadening allowed for an estimation of the thermodynamic parameters for this proton exchange reaction, giving ΔH ‡ = 46.

show abstract

“…The signal was found to lie 4.3 ppm downfield from its position in solution. Nitrogen-1 is quaternary and positively charged in NAD+ and is presumably less solvated in the active site; it is known that desolvation of positively charged 15N atoms moves their NMR signals downfield (Duthaler & Roberts, 1979;Schuster et al, 1979;Oppenheimer & Davidson, 1980). Reduction of the complex E.[ l-lSN]NAD+&JDP by glucose shifted the signal upfield to 112.5 ppm, which is similar to the value for [ 1-l5N]NADH in aqueous solution (Oppenheimer & Davidson, 1980; as calculated by subtracting the difference between the reported 6"N of [ 1 -l5N]NAD+ and [ 1 -l5N]NADH from the value of 615N for NAD+ in Figure 1).…”

Section: Microenvironmental Effects Of the Nad+ Binding Site On I5nanmentioning

confidence: 99%

The importance of binding energy in catalysis of hydride transfer by UDP-galactose 4-epimerase: A carbon-13 and nitrogen-15 NMR and kinetic study

Burke¹,

Frey²

1993

Biochemistry

View full text Add to dashboard Cite

UDP-galactose 4-epimerase contains NAD+ irreversibly but noncovalently bound to the active site. Uridine nucleotides bind to the substrate site and induce a protein conformational change that increases the chemical reactivity of NAD+ at the coenzyme site. Activation of NAD+ by uridine nucleotides perturbs the 15N and 13C NMR chemical shifts of selectively enriched NAD+ bound to the coenzyme site. The proton-decoupled 15N NMR signal for enzyme-bound [carboxamide-15N]NAD+ does not change upon addition of UDP, indicating that activation is not brought about by a change in the binding of the carboxamide group. The 15N NMR signal of enzyme-bound [nicotinamide-1-15N]NAD+ is shifted upfield 3.0 ppm and the 13C NMR signal for [nicotinamide-4-13C]NAD+ is shifted downfield 3.4 ppm downfield by the binding of UDP at the substrate site. These changes are consistent with the induction of a distortion into the nicotinamide ring, in which positive charge is transferred from N-1 to C-4. The kinetic and thermodynamic effects of these perturbations are significant, as indicated by the nonenzymatic chemical reactivities of a series of N-alkyl nicotinamides differing in the inductive electron withdrawing effects of the alkyl substituents. A downfield change of 3.4 ppm in the 4-13C chemical shifts brought about by electron withdrawal in the model compounds corresponds to a 3200-fold increase in the rate of reduction by NaBH3CN in water, a 15,000-fold increase in 86% ethanol, and a 152 mV more positive reduction potential in this series. The distortion of NAD+ by the binding of UDP is a long-range effect that is transmitted from the substrate binding site to the coenzyme through the protein conformational change. This apparently distorts the pi-electron distribution in the nicotinamide ring and reduces the activation energy for its reduction. Activation of enzyme-bound NAD+ toward reduction apparently arises from a destabilization in the nicotinamide ring structure rather than from a stabilization of the transition state through attractive interactions between the nicotinamide ring and the enzyme.

show abstract

Nitrogen-15 nuclear magnetic resonance spectroscopy. Effects of hydrogen bonding and protonation on nitrogen chemical shifts of pyrazoles

Cited by 40 publications

References 2 publications

¹⁵N NMR chemical shifts of NH‐pyrazoles in the solid state and in solution at low temperature

¹⁵N NMR chemical shifts of NH‐pyrazoles in the solid state and in solution at low temperature

Improved Synthesis and Detailed Characterization of a Hybrid Pyrazole‐TACN Dinucleating Ligand

The importance of binding energy in catalysis of hydride transfer by UDP-galactose 4-epimerase: A carbon-13 and nitrogen-15 NMR and kinetic study

Contact Info

Product

Resources

About

Nitrogen-15 nuclear magnetic resonance spectroscopy. Effects of hydrogen bonding and protonation on nitrogen chemical shifts of pyrazoles

Cited by 40 publications

References 2 publications

15N NMR chemical shifts of NH‐pyrazoles in the solid state and in solution at low temperature

15N NMR chemical shifts of NH‐pyrazoles in the solid state and in solution at low temperature

Improved Synthesis and Detailed Characterization of a Hybrid Pyrazole‐TACN Dinucleating Ligand

The importance of binding energy in catalysis of hydride transfer by UDP-galactose 4-epimerase: A carbon-13 and nitrogen-15 NMR and kinetic study

Contact Info

Product

Resources

About

¹⁵N NMR chemical shifts of NH‐pyrazoles in the solid state and in solution at low temperature

¹⁵N NMR chemical shifts of NH‐pyrazoles in the solid state and in solution at low temperature