Proton Spin-spin Coupling Research Articles

Structure Revision of Decurrensides A–E Enabled by the RFF Parametric Calculations of Proton Spin–Spin Coupling Constants

Structure revision of the recently characterized natural products, decurrensides A-E, is described. The revision is aided by fast and accurate computations of proton spin-spin coupling constants. While the (13)C chemical shifts calculations could reveal the misassignment of the original structures, the calculated spin coupling constants possess much higher structural information content, informing and guiding the process of structure reassignment. Together, calculations of (13)C chemical shifts and spin coupling constants constitute a robust and now practical structure discovery tool.

Fungal biofilm inhibitors from a human oral microbiome-derived bacterium

The human mouth is home to a rich assortment of native and transient microorganisms. One of the commonly encountered bacterial species, Streptococcus mutans, was shown to generate the novel hybrid polyketide-nonribosomal peptide metabolite mutanobactin A (1). We have characterized three new analogues, mutanobactins B-D (2-4), and subjected these compounds to further biomedical evaluation. Metabolites 1, 2, and 4 were found to inhibit biofilm formation by the fungal oral-pathogen Candida albicans. Compound 4 was the most potent metabolite with an IC(50) value of 5.3 ± 0.9 μM. Using a combination of Marfey's analysis, proton spin-spin coupling, and (1)H-(1)H NOESY data, we proposed absolute configuration assignments in toto for 1-3 and a partial assignment for 4. In addition, feeding studies with isotopically labeled precursor metabolites (acetate and amino acids) have helped to determine the biosynthetic origins of this unique natural product family.

Structure of (Z)-(5R)-methyl-2-(4-phenylbenzylidene)cyclohexanone as chiral component of liquid-crystalline systems

The spatial structure of (Z)-(5R)-methyl-2-(4-phenylbenzylidene)cyclohexanone prepared by photochemical isomerization of the E-isomer was studied by analyzing the magnitudes and temperature dependence of the proton spin-spin coupling constants obtained by 1H NMR spectroscopy and the results of molecular modeling using semiempirical quantum chemical AM1 and PM3 methods and the density functional theory (DFT). Comparison of the results obtained for the Z-and E-isomers shows that in both cases the conformational equilibrium for both isomers is characterized by significant preference of the chair conformer having an equatorial methyl group, namely, − ΔH (chair a ⇌ chair e) = 1.98–2.12 and 1.36–1.54 kcal mole−1 for the Z-and E-isomers, respectively. Distinctions in the non-planarity of the enone fragment and cyclohexanone ring in the Z-and E-isomers under study following from the results of mathematical modeling were confirmed by the experimental values of the geminal spin-spin coupling constants of protons of the methylene groups in α,α ′-positions with respect to the enone group. Quantum chemical calculations of the Z-isomer revealed the existence of intramolecular hydrogen bond between the carbonyl oxygen and the nearest aromatic proton in ortho-position of the benzene ring. Possible reasons for different helical twisting power of (Z)-(5R)-methyl-2-(4-phenylbenzylidene)cyclohexanone and the E-and Z-arylidene derivatives of 1R, 4R-isomenthone in the mesophase are discussed based on the results of molecular structure studies for these compounds.

Application of the quantum theory of atoms in molecules to selected physico‐chemical and biophysical problems: Focus on correlation with experiment

This article reviews how the quantum theory of atoms in molecules (QTAIM) can be used to predict experimental physico-chemical properties of molecules of biologic interest: the amino acids, the polycyclic aromatic hydrocarbons (PAH), and the opiates, for example, morphine and PEO. The predicted experimental properties are as diverse as the partial molar volumes, the free energies of hydration, the second code-letter in the genetic code, the resonance energies, and the proton spin-spin coupling constants. Recent examples of the utilization of QTAIM to construct excellent statistical models (with squared correlation coefficients (r(2)) > 0.9) correlating properties of the electron density and of the pair density to experiment are reviewed. Some new results on the solvent effects on electron delocalization are also presented.

Nuclear magnetic resonance spin-spin relaxation of the crystals of bone, dental enamel, and synthetic hydroxyapatites.

Studies of the apatitic crystals of bone and enamel by a variety of spectroscopic techniques have established clearly that their chemical composition, short-range order, and physical chemical reactivity are distinctly different from those of pure hydroxyapatite. Moreover, these characteristics change with aging and maturation of the bone and enamel crystals. Phosphorus-31 solid state nuclear magnetic resonance (NMR) spin-spin relaxation studies were carried out on bovine bone and dental enamel crystals of different ages and the data were compared with those obtained from pure and carbonated hydroxyapatites. By measuring the 31P Hahn spin echo amplitude as a function of echo time, Van Vleck second moments (expansion coefficients describing the homonuclear dipolar line shape) were obtained and analyzed in terms of the number density of phosphorus nuclei. 31P magnetization prepared by a 90 degree pulse or by proton-phosphorus cross-polarization (CP) yielded different second moments and experienced different degrees of proton spin-spin coupling, suggesting that these two preparation methods sample different regions, possibly the interior and the surface, respectively, of bone mineral crystals. Distinct differences were found between the biological apatites and the synthetic hydroxyapatites and as a function of the age and maturity of the biological apatites. The data provide evidence that a significant fraction of the protonated phosphates (HPO4(-2)) are located on the surfaces of the biological crystals, and the concentration of unprotonated phosphates (PO4(-3)) within the apatitic lattice is elevated with respect to the surface. The total concentration of the surface HPO4(-2) groups is higher in the younger, less mature biological crystals.

Structure of a DNA duplex that contains alpha-anomeric nucleotides and 3'-3' and 5'-5' phosphodiester linkages: coexistence of parallel and antiparallel DNA.

We report a comparative spectroscopic study of a novel self-complementary duplex decamer, d(GCGAAT-3'-3'-(alpha T)-5'-5'-CGC)2, in which an alpha-anomeric nucleotide has been inserted into the sequence in a parallel orientation via 3'-3' and 5'-5' phosphodiester bonds, and its unmodified B-DNA analog, d(GCGAATTCGC)2. Plots of the hyperchromicity and circular dichroism of these oligonucleotides are virtually identical, indicating that the overall base stacking and handedness are preserved in the alpha duplex. Thermodynamic parameters extracted from UV melting experiments show that the alpha duplex is only slightly less stable than the control. A near complete set of 1H and 31P nuclear magnetic resonance (NMR) assignments were obtained for both duplexes using classical one- and two-dimensional approaches. Several lines of evidence, in particular, imino 1H, 31P, nuclear Overhauser enhancement, and deoxyribose ring proton spin-spin coupling data, convincingly demonstrate that the overall structural integrity of the alpha and control duplexes are quite comparable, with any perturbations in the former localized to the regions of the construct encompassing the alpha-nucleotide and the unique backbone linkages. Specifically, the alpha duplex exhibits normal Watson-Crick type base pairing, it remains antiparallel except at the inverted nucleotide, all bases are in the anti orientation, and the sugar ring puckering is predominantly "S"-type. However, the J-coupling information for the alpha-nucleotide and the neighboring (3') cytidine are notably different, and reflect a decrease in the amplitude of the sugar pucker in alpha T7, and a significant shift in the conformational equilibrium of the furanose ring in C8 toward the "N"-type pucker. The feasibility of synthesizing oligodeoxynucleotides containing a combination of alpha sugars and short parallel stranded segments, their propensity for forming stable duplexes, and the structural insights into such complexes reported here are of potential importance in the area of antisense therapy.

Accurateab initiocarbon-proton and proton-proton spin-spin coupling surfaces for the methane molecule

Accurate ab initio values of the carbon-proton and proton proton spin-spin coupling constants of the methane molecule have been calculated at each of fifty-one distinct geometries. For each geometry the Fermi contact, spin-dipolar, orbital paramagnetic and orbital diamagnetic contributions were individually calculated. The resulting surfaces are treated as functions of symmetry displacement coordinates. Sixteen independent coefficients are required to describe the carbon proton coupling surface and twenty-two independent coefficients to describe the proton proton coupling surface to second order in the symmetry coordinates. Values for these coefficients are presented. The principal features of the results are the dominance of the Fermi contact contributions to the two couplings at all geometries, the greater importance of bond stretching for the carbon-proton coupling, the greater importance of angle-bending for the proton-proton coupling and the almost total cancellation of the orbital paramagnetic and o...

Inter-ring Long-range Spin-Spin Proton Coupling in some 8-Hydroxyquinoline Derivatives

A study of the 1 H NMR spectra of a series of 8-hydroxyquinolines has been carried out using the 2D-COSYLR method and inter-ring proton spin-spin coupling constants 4 J , 5 J , 6 J and 7 J have been detected; it has been established that the π- mechanism for transmission of spin–spin coupling predominates and in the case of the planar zig-zag arrangement this results in unexpected annulment of 6 J 2,7 and 6 J 3,6 .

Proton NMR investigation of the collective proton motion in hydrogen-bonded systems of monoaurates of 2,6-bis((diethylamino)methyl)-4-R-phenols

This paper discusses studies of monoaurates of 2,6-bis((diethylamino)methyl)-4-R-phenols in CD{sub 2}Cl{sub 2} solutions using {sup 1}H NMR. Proton deshielding increases with increasing phenolic group acidity, with the strongest deshielding and largest polarizability in the R=Cl system. Increasing acidity causes increasing proton shielding by N atoms. When H{sub 2}-bonded protons are preferentially present at the N atoms, Ph-Ch{sub 2} and N-CH{sub 2} protons signals broaden strongly with doublet and octet formation occurring when the protons are almost localized at these atoms; this is due to methylene proton-NH{sup +} proton spin-spin coupling. 9 refs., 1 fig., 2 tabs.

The relationship between partial bond fixation induced by through-bond and/or through-space perturbations in nonplanar benzene derivatives and proton spin-spin coupling constants

4 J Me-C-C-H = 4 J OB , the spin-spin coupling constant over four formal bonds between methyl protons and a proton bonded to an sp carbon, previously established 9-17 was a probe for bond order, was determined for 6-methyl-1,4-dihydro-1,4-methanonaphthalene (1) and for a number of reference compounds 2-5. Self-consistent field (SCF) calculations at the 3-21G level for 1-4 predict partial bond fixation in the benzene ring for all molecules in the sense predicted by interpretation of previously-reported photoelectron spectra of closely-related molecules

Effect of the substituents on the conformational behavior of five-membered rings: Application to the cis- and trans-2,5-dimethoxytetrahydrofuran

A model is proposed which assumes that the pseudorotational potential in five-membered rings is given by the combination of contributions from the unsubstituted ring, from the individual substituents and from interactions between pairs of substituents. The application of this model to the potentials calculated by the MM2 force field for the cis and trans-2,5-dimethoxytetrahydrofuran shows that the contributions from the individual substituents explain the main features of the potentials of these disubstituted rings. The pseudorotational analysis from vicinal proton spin-spin coupling constants 3JHH confirms the realibility of the MM2 potentials.

Conformational analysis of the pyrrolidine ring of the N-methylthiohydantoin of 2-methylproline

The conformational analysis of the pyrrolidine ring in 2-methylproline-N-methylthiohydantoin was achieved from the vicinal proton spin-spin coupling constants obtained from the 360 MHz 1H NMR spectrum in hexadeuterobenzene solution. Two descriptions are consistent with the experimental data. One is a large amplitude torsional oscillation centered between a β-endo envelope (C8) and a β-endo-α-exo twist (C2). The other is a 3 : 1 dynamic equilibrium between two fixed states: a (major) β-exo envelope and a minor N-endo envelope with N-endo-δ-exo twist character. The effect of the 2-methyl group on the pyrrolidine ring conformation is evaluated and discussed.

Temperature dependence of the carbon-13 proton spin-spin coupling constant in gaseous methane

The nuclear spin-spin coupling constant 1 J(13C, H) in 13C-enriched methane gas has been observed by 13C resonance to increase from 125·264 Hz at 180 K to 125·347 Hz at 369 K. The dependence on temperature is non-linear with a much steeper variation at higher temperatures. Very similar results are observed in 1H resonance. There appears to be a very slight dependence of 1 J(13C, H) on density at the lower temperatures. The theory of the temperature dependences of 1 J(13C, H) and 1 J(13C, D) in the low density, gaseous, isotopomers of methane 13CH x D4 - x is presented in terms of the coefficients of a single carbon-13 proton spin-spin coupling surface, the elements of the tensor of vibration-rotation theory and the average values of reduced normal coordinates and their squares. Results are applicable to the temperature dependences of all X, Y coupling constants and Y nuclear shielding constants in X Y 4 molecules of Td symmetry. Application of the theory to the results on 13CH4 gives an equilibrium value ...

Theory of the carbon-13 proton spin-spin coupling and the proton shielding surfaces of the methane molecule

The form of the carbon-13 proton spin-spin coupling surface of the methane molecule is investigated. The three first-order and twelve second-order independent symmetry coordinate coefficients required to determine the four distinct coupling constants for small but otherwise arbitary displacements from equilibrium are identified. Valence coordinate coefficients for the surface are also determined. The results will be of help in understanding the effects of temperature and of primary and secondary isotopic substitution on the observed coupling and also in simplifying ab initio calculations of the surface for methane and for 1 J(X, Y) in other XY 4 compounds of Td symmetry. The results are also applicable to the proton shielding surface of methane and the Y nuclear shielding surfaces in other XY 4 compounds of Td symmetry.

Nuclear magnetic resonance and molecular orbital study of internal hydrogen bonding in salicyl alcohol. Principal site analysis based on the sidechain methylene and hydroxy proton long-range coupling constants

The 1H n.m.r. spectra of 2-hydroxybenzyl, 2-methoxybenzyl, 2-hydroxy-3-methoxy-, and 2,6-dimethoxy-benzyl alcohols are studied in various solvents. The long-range proton–proton spin-spin coupling constants, certain chemical shifts, and some STO-3G MO calculations are used to characterize the conformational behaviour of salicyl alcohol. The observed variation of the coupling constants is reproduced by a three-site model: salicyl alcohol and its 2-methoxy derivative seem to have three principal conformations: clsd1(= closed 1) with a hydrogen bond between the phenolic hydrogen and CH2OH, open with a rather freely rotating CH2OH sidechain, and clsd2 with a hydrogen bond between the CH2OH hydroxy group and the phenolic oxygen atom. The free energy of the internal hydrogen bond in clsd2 is smaller than in clsd1. The presence of the clsd2 form is inferred by indirect methods, not from direct indicators like hydroxy stretching frequencies or proton chemical shifts. The hydrogen-bonded forms predominate in non-polar solvents. The hydrogen bonds are opened by nucleophilic solvents. For D2O solutions a deuterium-bridged structure is suggested.

ChemInform Abstract: A NUCLEAR MAGNETIC RESONANCE STUDY ON CONFORMATIONAL BEHAVIOR OF DIARYLMETHYLENEMALONALDEHYDES AND THEIR COMPLEX FORMATION WITH MAGNESIUM AND LITHIUM PERCHLORATES BY USING FOUR‐BOND ALDEHYDE PROTON AND THREE‐BOND ALDEHYDE CARBON‐PROTON SPIN‐SPIN COUPLINGS: A STRATEGY FOR STUDYING STRONGLY ENTROPICALLY CONTROLLED FLEXIBLE MOLECULAR SYSTEMS

Chemischer InformationsdienstVolume 16, Issue 48 Physical Organic Chemistry ChemInform Abstract: A NUCLEAR MAGNETIC RESONANCE STUDY ON CONFORMATIONAL BEHAVIOR OF DIARYLMETHYLENEMALONALDEHYDES AND THEIR COMPLEX FORMATION WITH MAGNESIUM AND LITHIUM PERCHLORATES BY USING FOUR-BOND ALDEHYDE PROTON AND THREE-BOND ALDEHYDE CARBON-PROTON SPIN-SPIN COUPLINGS: A STRATEGY FOR STUDYING STRONGLY ENTROPICALLY CONTROLLED FLEXIBLE MOLECULAR SYSTEMS R. LAATIKAINEN, R. LAATIKAINENSearch for more papers by this authorV. KRAL, V. KRALSearch for more papers by this author R. LAATIKAINEN, R. LAATIKAINENSearch for more papers by this authorV. KRAL, V. KRALSearch for more papers by this author First published: December 3, 1985 https://doi.org/10.1002/chin.198548068Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume16, Issue48December 3, 1985 RelatedInformation

Calibration of the angular dependence of the amide proton-C α proton coupling constants, 3JHN α, in a globular protein : Use of 3JHN α for identification of helical secondary structure

The vicinal amide proton-C α proton spin-spin coupling constants, 3 J HNα in the globular protein basic pancreatic trypsin inhibitor (BPTI) have been measured using phase-sensitive correlated spectroscopy at high digital resolution. In conjunction with the crystal structure of BPTI, these data were used to calibrate the correlation between 3 J HN α and the dihedral angle φ. The resulting “BPTI curve” is 3J HNα = 6.4 cos 2 θ − 1.4 cos θ + 1.9 (θ = ¦φ − 60° ¦) . It is further shown that measurement of the spin-spin couplings 3 J HN α presents an independent, reliable method for identification of the location of helical structure in the amino acid sequence of proteins.

ChemInform Abstract: PEPTIDE CONFORMATIONS. 20. CONFORMATIONAL ANALYSIS OF PROLINE RINGS FROM PROTON SPIN‐SPIN COUPLING CONSTANTS AND FORCE‐FIELD CALCULATIONS: APPLICATION TO THREE CYCLIC TRIPEPTIDES

Chemischer InformationsdienstVolume 14, Issue 31 Physical Organic Chemistry ChemInform Abstract: PEPTIDE CONFORMATIONS. 20. CONFORMATIONAL ANALYSIS OF PROLINE RINGS FROM PROTON SPIN-SPIN COUPLING CONSTANTS AND FORCE-FIELD CALCULATIONS: APPLICATION TO THREE CYCLIC TRIPEPTIDES F. A. A. M. DE LEEUW, F. A. A. M. DE LEEUWSearch for more papers by this authorC. ALTONA, C. ALTONASearch for more papers by this authorH. KESSLER, H. KESSLERSearch for more papers by this authorW. BERMEL, W. BERMELSearch for more papers by this authorA. FRIEDRICH, A. FRIEDRICHSearch for more papers by this authorG. KRACK, G. KRACKSearch for more papers by this authorW. E. HULL, W. E. HULLSearch for more papers by this author F. A. A. M. DE LEEUW, F. A. A. M. DE LEEUWSearch for more papers by this authorC. ALTONA, C. ALTONASearch for more papers by this authorH. KESSLER, H. KESSLERSearch for more papers by this authorW. BERMEL, W. BERMELSearch for more papers by this authorA. FRIEDRICH, A. FRIEDRICHSearch for more papers by this authorG. KRACK, G. KRACKSearch for more papers by this authorW. E. HULL, W. E. HULLSearch for more papers by this author First published: August 2, 1983 https://doi.org/10.1002/chin.198331082AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume14, Issue31August 2, 1983 RelatedInformation

Peptide conformations. 20. Conformational analysis of proline rings from proton spin-spin coupling constants and force-field calculations: application to three cyclic tripeptides

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPeptide conformations. 20. Conformational analysis of proline rings from proton spin-spin coupling constants and force-field calculations: application to three cyclic tripeptidesFrank A. A. M. De Leeuw, Cornelis Altona, Horst Kessler, Wolfgang Bermel, Axel Friedrich, Gerhard Krack, and William E. HullCite this: J. Am. Chem. Soc. 1983, 105, 8, 2237–2246Publication Date (Print):April 1, 1983Publication History Published online1 May 2002Published inissue 1 April 1983https://doi.org/10.1021/ja00346a023RIGHTS & PERMISSIONSArticle Views182Altmetric-Citations50LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

ChemInform Abstract: DETERMINATION OF PROLINE RING NONPLANARITY FROM PROTON SPIN‐SPIN COUPLING CONSTANTS: APPLICATIONS TO TWO CYCLIC PENTAPEPTIDES

Chemischer InformationsdienstVolume 13, Issue 18 Physical Organic Chemistry ChemInform Abstract: DETERMINATION OF PROLINE RING NONPLANARITY FROM PROTON SPIN-SPIN COUPLING CONSTANTS: APPLICATIONS TO TWO CYCLIC PENTAPEPTIDES A. C. II BACH, A. C. II BACHSearch for more papers by this authorA. A. BOTHNER-BY, A. A. BOTHNER-BYSearch for more papers by this authorL. M. GIERASCH, L. M. GIERASCHSearch for more papers by this author A. C. II BACH, A. C. II BACHSearch for more papers by this authorA. A. BOTHNER-BY, A. A. BOTHNER-BYSearch for more papers by this authorL. M. GIERASCH, L. M. GIERASCHSearch for more papers by this author First published: May 4, 1982 https://doi.org/10.1002/chin.198218073Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume13, Issue18May 4, 1982 RelatedInformation