Hydrogen bond studies by nitrogen-14 nuclear magnetic resonance. III. Electron redistribution associated with hydrogen bonding and metal-complex formation of formamide and N-methylacetamide

Saitô, Hazime; Tanaka, Yuji; Nukada, Kenkichi

doi:10.1021/ja00734a006

Cited by 38 publications

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“…The sensitivity of the chemical-shift displacement due to a slight variation of electron distribution is significantly enhanced by a contribution of the paramagnetic current around the heteroatom under consideration. Therefore, if adequate accuracy of the chemicalof data using this method have been accumulated (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14).…”

Section: Introductionmentioning

confidence: 99%

¹³C Nuclear Magnetic Resonance Studies on Molecular Association. I. Self-association of Dipolar Molecules

Saitô¹,

Tanaka²,

Nagata³

et al. 1973

Can. J. Chem.

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Self-association of dipolar substances is studied by 13C magnetic resonance. The dilution shifts in carbon tetrachloride are analyzed in terms of the monomer–dimer equilibrium. Downfield 13C shifts of the nitrile and carbonyl groups are observed for the formation of the dimer of acetone, acetonitrile, and ethyl acetate. Upfield 13C shifts, on the other hand, are observed in the methyl and methylene groups of acetone, methylethyl ketone, ethyl acetate, acetonitrile, propionitrile, nitromethane, nitroethane, N,N-di-methylformamide, and N,N-dimethylacetamide. The equilibrium constants are 0.1–0.5 in units of mole fraction. The downfield 13C shifts of the nitrile and carbonyl groups are interpreted in terms of electric (reaction) field effects imposed by another molecule through dimer formation. The alternation of polarity by polarization of the X–Y group explains the upfield 13C shifts of methyl and methylene groups as shown in the following scheme: Hs+—C−—X+—Y−, where X—Y stands for C=O, C≡N, and NO2 groups which have been classified as –I− groups by Pople and Gordon.

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Section: Introductionmentioning

confidence: 99%

¹³C Nuclear Magnetic Resonance Studies on Molecular Association. I. Self-association of Dipolar Molecules

Saitô¹,

Tanaka²,

Nagata³

et al. 1973

Can. J. Chem.

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“…36 Additional studies have also reported that nitrogen chemical shift is substantially affected due to making and breaking of hydrogen bonds. 40,41 Hence, we have chosen 15 N for our measurements which have been correlated with local conformation and hydrogen bond formation. 42 We can also study exclusive backbone properties and effects of various treatments on Pro/Hyp and Gly nitrogen environment inside chains of the helix.…”

Section: Resultsmentioning

confidence: 99%

Mechanistic Insights into the Role of Water in Backbone Dynamics of Native Collagen Protein by Natural Abundance ¹⁵N NMR Spectroscopy

Singh

Sinha

2016

J. Phys. Chem. C

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Collagen being the most abundant animal protein is an integral component of muscle, connective tissues, cartilage, and bones, having function to provide strength, load bearing, and flexibility to organisms. The structural and functional role of water mediated hydrogen bonding network of collagen has been debated. We present here a solid–state nuclear magnetic resonance (ssNMR) spectroscopy method to observe water dependent backbone dynamics of collagen protein in its absolute native environment inside bone. The load bearing function of collagen is directly dependent on its backbone dynamics. The picoseconds backbone dynamics has been measured by relaxation rate measurement (R1) of natural isotopic abundance 15N (∼0.37%) resonance. The sensitivity of natural abundance 15N ssNMR spectrum is enhanced by paramagnetic doping of copper-ethylenediaminetetraacetic acid (Cu (II) EDTA) inside bone matrix. Exclusive backbone resonances originating from proline/hydroxyproline (Pro/Hyp) and glycine (Gly) resonances are well resolved in 15N spectrum, giving access to relaxation rates from native collagen backbone. The water dependent site-resolved relaxation measurements have provided mechanistic insights into role of water mediated hydrogen bonding network in native collagen backbone dynamics. Our study has given new insights in the understanding of water dependent native collagen dynamics, functions, and stability.

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“…In the literature there are conflicting explanations of the chemistry of metal ion–polymer functional group complexes. For instance, for polyamides some studies have concluded that metal ions coordinate to amides via the carbonyl oxygen30, 31; others attribute the results to the formation of a metal–nitrogen ligand 32, 33…”

Section: Resultsmentioning

confidence: 99%

Binary blends of poly(vinyl chloride) stabilized by lithium acetate-thermal studies

Pielichowski

1999

J. Appl. Polym. Sci.

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A series of blends of poly(vinyl chloride) (PVC) with (1) poly(methyl methacrylate) (PMMA) or (2) polyoxymethylene (POM), with lithium acetate as a stabilizing agent, was investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA), either alone or coupled with Fourier transform infrared (FTIR) spectroscopy. It was found that lithium acetate has a significant effect on the thermal properties of blends under investigation. It causes the initial decomposition temperatures to increase by about 60 -150°C for PVC-POM blends, a substantial suppression of the volatile products evolution for PVC/PMMA blends, and an improvement in the surface morphology for both polymer systems by lowering the degree of roughness. The origin of these effects was discussed by analysis of the intermolecular complexation between metal salt and PVC structural arrangements in the blends. Such interactions may lead to the formation of long-range, directional-specific structural regularities, which in turn thermally stabilize the whole system (strong interactions model).

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Hydrogen bond studies by nitrogen-14 nuclear magnetic resonance. III. Electron redistribution associated with hydrogen bonding and metal-complex formation of formamide and N-methylacetamide

Cited by 38 publications

References 0 publications

¹³C Nuclear Magnetic Resonance Studies on Molecular Association. I. Self-association of Dipolar Molecules

¹³C Nuclear Magnetic Resonance Studies on Molecular Association. I. Self-association of Dipolar Molecules

Mechanistic Insights into the Role of Water in Backbone Dynamics of Native Collagen Protein by Natural Abundance ¹⁵N NMR Spectroscopy

Binary blends of poly(vinyl chloride) stabilized by lithium acetate-thermal studies

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Hydrogen bond studies by nitrogen-14 nuclear magnetic resonance. III. Electron redistribution associated with hydrogen bonding and metal-complex formation of formamide and N-methylacetamide

Cited by 38 publications

References 0 publications

13C Nuclear Magnetic Resonance Studies on Molecular Association. I. Self-association of Dipolar Molecules

13C Nuclear Magnetic Resonance Studies on Molecular Association. I. Self-association of Dipolar Molecules

Mechanistic Insights into the Role of Water in Backbone Dynamics of Native Collagen Protein by Natural Abundance 15N NMR Spectroscopy

Binary blends of poly(vinyl chloride) stabilized by lithium acetate-thermal studies

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¹³C Nuclear Magnetic Resonance Studies on Molecular Association. I. Self-association of Dipolar Molecules

¹³C Nuclear Magnetic Resonance Studies on Molecular Association. I. Self-association of Dipolar Molecules

Mechanistic Insights into the Role of Water in Backbone Dynamics of Native Collagen Protein by Natural Abundance ¹⁵N NMR Spectroscopy