On the detection of both carbonyl and hydroxyl oxygens in amino acid derivatives: a 17O NMR reinvestigation (original) (raw)
Related papers
The Journal of Physical Chemistry, 1991
The I 7 0 NMR line widths of the a-carboxyl groups of the protein amino acids includin 4-hydroxyproline, sarcosine, linear correlation was found between the line widths and the molecular weights of the amino acids at the pH values 0.5, 6.0, and 12.5, which are characteristic of the three ionization states of the neutral amino acids. The slopes of the straight lines were independent of pH; however, the line widths at acidic pH were increased by 98 f 13 Hz relative to those at neutral or basic pH. Since the I7O quadrupole coupling constant is only weakly influenced by the protonation state of the amino acids, it can be concluded that the a-carboxylic group is hydrated by an excess of two molecules of water relative to the a-carboxylate group. The lifetime of the water association is far below the NMR chemical shift time scale. Of the oxygen-containing functional groups of the amino acid side chains, only the phenolate ion of tyrosine was found to form water complexes that are stable within the range of the correlation times. It is shown that the I7O line widths of the a-carboxyl groups reflect the overall rotational correlation time of the amino acids. In contrast, the a-carbons are characterized by shorter effective correlation times presumably due to internal rotation of the C,-H vector. N,N-dimethylglycine, and Omethyltyrosine were measured in aqueous solution at 40 O C (I ! 0 enrichment 10 atom W). A
Solid-state 17O NMR of amino acids
2004
17O solid-state NMR from 14 amino acids is reported here, greatly increasing the number investigated. In most cases well-separated resonances from carbonyl and hydroxyl oxygens with distinct second-order quadrupolar line shapes are observed using a 600 MHz spectrometer with fast magic angle spinning (MAS). This is in contrast to the motionally averaged resonances usually seen from amino acids in solution.
The determination of 17O NMR parameters of hydroxyl oxygen: a combined deuteration and DOR approach
Magnetic resonance in chemistry : MRC, 2007
The direct detection of hydroxyl oxygen (O-H) by (17)O double-rotation (DOR) NMR is very challenging because of the strong O-H dipole interaction. It is shown that deuteration of the hydroxyl site overcomes this using glycine.HCl as an illustration. Two well-separated sets of narrow (linewidth approximately 80-100 Hz) resonances with their spinning-sidebands are observed for the carboxyl and hydroxyl oxygens in the DOR spectrum of [(17)O,(2)H]glycine.HCl. The chemical shift anisotropy of these sites is obtained from a simulation of the DOR spinning-sideband intensities. The chemical shift span (Omega) for the carboxyl oxygen is found to be much larger than that of the hydroxyl oxygen, with Omega values of 540 +/- 15 and 210 +/- 10 ppm, respectively.
17O NMR and DFT study of hydrogen bonding: Proton sharing and incipient transfer
Lithuanian Journal of Physics
17O NMR spectra of pyridine N-oxide (PyO) complexes with the acids – acetic (AA), cyanoacetic (CyA), propiolic (PA), trichloroacetic (TCA), trifluoroacetic (TFA), hydrochloric (HCl) and methanesulfonic (MSA) – as well as some related molecules with intramolecular H-bonds (4-substituted picolinic acid N-oxides) were studied in an acetonitrile (ACN) solution. In order to evaluate the effect of proton positioning along the O–H…O bond on the measured chemical shifts the full geometry optimization was carried out, and 17O magnetic shielding tensors were calculated using density functional theory (DFT). The modified hybrid functional PBE1PBE with the 6-311++G** basis set and the gauge-including atomic orbital (GIAO) approach were applied. The solvent effect was taken into account by a polarized continuum model using the integral equation formalism (IEFPCM). Two stable structures were deduced for the PyO complexes with TCA and TFA that correspond to the H-bonds with and without proton tran...
15N NMR spectroscopy acids: 7—solvent effects on α-and ω-amino
Organic Magnetic Resonance, 1979
The natural abundance "N NMR spectra of several a-and o-amino auds were measured in various protic solvents. Increasing acidity of the solvents results in an upfield shift in the case of the a-amino acids, while o-amino acids are almost insensitive to solvent effects.
The Journal of Physical Chemistry B, 2006
Trends in the chlorine chemical shift (CS) tensors of amino acid hydrochlorides are investigated in the context of new data obtained at 21.1 T and extensive quantum chemical calculations. The analysis of chlorine-35/37 NMR spectra of solid L-tryptophan hydrochloride obtained at two magnetic field strengths yields the chlorine electric field gradient (EFG) and CS tensors, and their relative orientations. The chlorine CS tensor is also determined for the first time for DL-arginine hydrochloride monohydrate. The drastic influence of 1 H decoupling at 21.1 T on the spectral features of salts with particularly small 35 Cl quadrupolar coupling constants (C Q ) is demonstrated. The chlorine CS tensor spans (Ω) of hydrochloride salts of hydrophobic amino acids are found to be larger than those for salts of hydrophilic amino acids. A new combined experimental-theoretical procedure is described in which quantum chemical geometry optimizations of hydrogen-bonded proton positions around the chloride ions in a series of amino acid hydrochlorides are cross-validated against the experimental chlorine EFG and CS tensor data. The conclusion is reached that the relatively computationally inexpensive B3LYP/ 3-21G* method provides proton positions which are suitable for subsequent higher-level calculations of the chlorine EFG tensors. The computed value of Ω is less sensitive to the proton positions. Following this cross-validation procedure, |C Q ( 35 Cl)| is generally predicted within 15% of the experimental value for a range of HCl salts. The results suggest the applicability of chlorine NMR interaction tensors in the refinement of proton positions in structurally similar compounds, e.g., chloride ion channels, for which neutron diffraction data are unavailable.
15N NMR spectroscopy acids: 7�solvent effects on a-and ?-amino
Magn Reson Chem, 1979
The natural abundance "N NMR spectra of several a-and o-amino auds were measured in various protic solvents. Increasing acidity of the solvents results in an upfield shift in the case of the a-amino acids, while o-amino acids are almost insensitive to solvent effects.
17O NMR Studies of Solid Amino Acids
Springer eBooks, 1990
15 n labeled amino acids are routinely used to label proteins or nucleic acids for study by nMR. However, nMR studies of 15 n labeled amino acids in metabolite studies have not been pursued extensively, presumably due to line broadening present under standard experimental conditions. in this work, we show that lowering the temperature to −5 °C allows facile characterization of 15 n-labeled amino acids. further, we show that this technique can be exploited to measure 15 nH 3 produced in an enzyme catalyzed reaction and the transport and metabolism of individual amino acids in mammalian cell culture. With respect to 13 c-labeled amino acids, 15 n-labeled amino acids are less costly and enable direct characterization of nitrogen metabolism in complex biological systems by nMR. in summary, the present work significantly expands the metabolite pools and their reactions for study by NMR.
Organic Magnetic Resonance, 1982
Erythro and threo configurational assignments have been made for 11 p-fluoro-a-amino acids or esters using the effect of complexation of the ammonium group by 18-crown-6 ether on the '9 NMR parameters. For the erythro con6gurations, 'J(tFF) increases and a high-field ' % chemical shift is generally observed; these phenomena are accompanied by a decrease in 'J(J3H) and 3J(CF). The opposite effects are observed for the threo configurations. These observations can be explained by a change in the relative population of the conformers around the C,-C, bond on complexation of the ammonium group. This complexation impairs the interactions between the ammonium and fluorine groups and, concomitantly, the steric hindrance between the ammonium and R (methyl, phenyl or carboxylate) groups is increased. Compound R R' -0 A(-+) 'JIHF) A'J 'J(HF) AzJ Erythro 1 CH, H 183.3 +1.9 21.6 +3.0 45.8 0.0 2 CH, Et 183.7, +1.4 22.5, +3.9, 46.7 +0.65 3 C,H, Et 192.8, +3.8 22.9 +5.2 45.6 +0.2 4 COOH H 198.2 +1.7 29.1 +1.0 47.6 -0.1 5 COOMe Me 199.0 -0.4 28.7, +1.0 47.1 -0.4 Threo 6 CH, H 183.4 -1.3 24.8 -4.3 45.3 0.0 7 CH, Et 183.4 -1.2 24.5 -3.5 46.0 0.0 8 C,H, H 189.6 -9.0 26.0 -10.5 44.9 0.0 9 C,H, Et 185.7 -7.6 21.6, -7.6 45.5 +1.2 10
Probing O–H Bonding through Proton Detected 1H–17O Double Resonance Solid-State NMR Spectroscopy
Journal of the American Chemical Society, 2018
The ubiquity of oxygen in organic, inorganic, and biological systems has stimulated the application and development of 17O solid-state NMR spectroscopy as a probe of molecular structure and dynamics. Unfortunately, 17O solid-state NMR experiments are often hindered by the combination of broad NMR signals and low sensitivity. Here, it is demonstrated that fast MAS and proton detection with the D-RINEPT pulse sequence can be generally applied to enhance the sensitivity and resolution of 17O solid-state NMR experiments. Complete 2D 17O→1H D-RINEPT correlation NMR spectra were typically obtained in fewer than 10 hours from less than 10 milligrams of material, with low to moderate 17O enrichment (less than 20%). 2D 1H-17O correlation solid-state NMR spectra allow overlapping oxygen sites to be resolved on the basis of proton chemical shifts or by varying the mixing time used for 1H-17O magnetization transfer. In addition, J-resolved or separated local field (SLF) blocks can be incorporated into the D-RINEPT pulse sequence to allow direct measurement of one-bond 1H-17O scalar coupling constants (1JOH) or 1H-17O dipolar couplings (DOH), respectively; the latter of which can be used to infer 1H-17O bond lengths. 1JOH and DOH calculated from planewave density functional theory (DFT) show very good agreement with experimental values. Therefore, the 2D 1H-17O correlation experiments, 1H-17O scalar and dipolar couplings, and planewave DFT calculations provide a method to precisely determine proton positions relative to oxygen atoms. This capability opens new opportunities to probe interactions between oxygen and hydrogen in a variety of chemical systems. Disciplines