Norbert Müller - Academia.edu (original) (raw)
Papers by Norbert Müller
Journal of Molecular Structure, 1995
Deuterium isotope effects on 13C chemical shifts have been determined in a series of monodeuteria... more Deuterium isotope effects on 13C chemical shifts have been determined in a series of monodeuteriated trans-N-benzylideneanilines. The effects over two bonds (2Δ) observed at C-1 and over three bonds (3Δ) observed at C-2,6 are sensitive to steric interactions involving nitrogen lone-pair electrons and C-Ph ortho-protons. Like in similar π-electron systems, the effect over six bonds (6Δ) is related to molecular
AIP Conference Proceedings, 1995
Journal of Natural Products, 2009
New brominated anthraquinone pigments, proisocrinins A-F (1-6), were isolated from the strikingly... more New brominated anthraquinone pigments, proisocrinins A-F (1-6), were isolated from the strikingly scarlet-colored stalked crinoid Proisocrinus ruberrimus, which had been collected in the deep sea of the Okinawa Trough, Japan. The structures of the compounds were elucidated by spectroscopic analysis including HRMS, 1D 1H and 13C NMR, and 2D NMR. CD spectroscopy revealed that all compounds are present as optically active enantiomers. This is the first report of tribromo and tetrabromo anthraquinones from a natural source.
The Journal of Chemical Physics, 1993
A group spin approach is used to describe the interconversion of magnetization modes in systems o... more A group spin approach is used to describe the interconversion of magnetization modes in systems of three equivalent spins 1/2. It is shown that the most prominent effect of cross correlation of the fluctuations of chemical shift anisotropy and dipolar interactions is the transformation of two-quantum coherences of second rank into third rank coherences. A novel experiment is described which allows one to observe such a process.
Journal of Agricultural and Food Chemistry, 2008
Four derivatives of thymol, carvacrol, and eugenol were synthesized: 4-(hydroxymethyl)-5-isopropy... more Four derivatives of thymol, carvacrol, and eugenol were synthesized: 4-(hydroxymethyl)-5-isopropyl-2-methylphenol, 4,4′-methylenebis(5-isopropyl-2-methyl)phenol, 4-allyl-6-(hydroxymethyl)-2-methoxyphenol, and 4-(hydroxymethyl)-2-isopropyl-5-methylphenol. The obtained derivatives showed remarkably better antioxidative properties according to 1,1-diphenyl-2-picrylhydrazyl assay (50% inhibitory concentrations ) 4-156 µg/mL) and Rancimat assay (protection factors ) 1.55-5.84) when compared with parent compounds and values similar to or better than those of butylated hydroxytoluene and vitamin C. At concentrations of 10 mM carvacrol derivatives had no toxic effect on viability of Escherichia coli K-12 (determined by minimum inhibitory concentrations). Other phenol derivatives showed reduced cytotoxic effect on E. coli K-12 at concentrations of 2-5 mM on the basis of 50% lethal dose measurements. In comparison with the parent compounds, phenol derivatives showed reduced cytotoxic effect for Saccharomyces cerevisiae cells (determined by yeast colony reduction). On the other hand, the majority of synthesized compounds had dose-dependent antiproliferative effects on human uterine carcinoma cells (HeLa), which makes them potentially interesting for the adjuvant experimental cancer treatments. The 4,4′-methylenebis(5-isopropyl-2-methyl)phenol derivative of carvacrol showed lower inhibiting capacity also for the HeLa cells, which makes this particular derivative attractive as an efficient antioxidant with negligible cytotoxic effects.
Journal of Magnetic Resonance, 2009
We have systematically investigated the line shapes observed in proton nuclear spinnoise spectra ... more We have systematically investigated the line shapes observed in proton nuclear spinnoise spectra which depend in a complex way on the properties of the resonance circuit, the number of spins present, transverse relaxation, inhomogeneous broadening, and radiation damping. Using highly sensitive high resolution probes these dependencies are investigated by way of high resolution 1 H noise power NMR spectra of liquid samples. Significant deviations from intuitive expectations are observed. Simulations based on an adapted Nyquist noise equation are used to understand and interpret the experimental findings.
Journal of Magnetic Resonance, 2009
We have systematically investigated the line shapes observed in proton nuclear spinnoise spectra ... more We have systematically investigated the line shapes observed in proton nuclear spinnoise spectra which depend in a complex way on the properties of the resonance circuit, the number of spins present, transverse relaxation, inhomogeneous broadening, and radiation damping. Using highly sensitive high resolution probes these dependencies are investigated by way of high resolution 1 H noise power NMR spectra of liquid samples. Significant deviations from intuitive expectations are observed. Simulations based on an adapted Nyquist noise equation are used to understand and interpret the experimental findings.
Journal of Biomolecular NMR, 2010
We have assessed the potential of an alternative probe tuning strategy based on the spin-noise re... more We have assessed the potential of an alternative probe tuning strategy based on the spin-noise response for application in common high-resolution multi-dimensional biomolecular NMR experiments with water signal suppression on aqueous and salty samples. The method requires the adjustment of the optimal tuning condition, which may be offset by several 100 kHz from the conventional tuning settings using the noise response of the water protons as an indicator. Although the radio frequency-pulse durations are typically longer under such conditions, signal-to-noise gains of up to 22% were achieved. At salt concentrations up to 100 mM a substantial sensitivity gain was observed.
Analytical and Bioanalytical Chemistry, 2004
Nano-electrospray-ionization mass spectrometry (nano-ESI-MS) is employed here to describe equilib... more Nano-electrospray-ionization mass spectrometry (nano-ESI-MS) is employed here to describe equilibrium protein conformational transitions and to analyze the influence of instrumental settings, pH, and solvent surface tension on the charge-state distributions (CSD). A first set of experiments shows that high flow rates of N(2) as curtain gas can induce unfolding of cytochrome c (cyt c) and myoglobin (Mb), under conditions in which the stability of the native protein structure has already been reduced by acidification. However, it is possible to identify conditions under which the instrumental settings are not limiting factors for the conformational stability of the protein inside ESI droplets. Under such conditions, equilibrium unfolding transitions described by ESI-MS are comparable with those obtained by other established biophysical methods. Experiments with the very stable proteins ubiquitin (Ubq) and lysozyme (Lyz) enable testing of the influence of extreme pH changes on the ESI process, uncoupled from acid-induced unfolding. When HCl is used for acidification, Ubq and Lyz mass spectra do not change between pH~7 and pH 2.2, indicating that the CSD is highly characteristic of a given protein conformation and not directly affected by even large pH changes. Use of formic or acetic acid for acidification of Ubq solutions results in major spectral changes that can be interpreted in terms of protein unfolding as a result of the increased hydrophobicity of the solvent. On the other hand, Lyz, cyt c, and Mb enable direct comparison of protein CSD (corresponding to either the folded or the unfolded protein) in HCl or acetic acid solutions at low pH. The values of surface tension for these solutions differ significantly. Confirming indications already present in the literature, we observe very similar CSD under these solvent conditions for several proteins in either compact or disordered conformations. The same is true for comparison between water and water-acetic acid for folded cyt c and Lyz. Thus, protein CSD from water-acetic solutions do not seem to be limited by the low surface tension of acetic acid as previously suggested. This result could reflect a general lack of dependence of protein CSD on the surface tension of the solvent. However, it is also possible that the effect of acetic acid on the precursor ESI droplets is smaller than generally assumed.
We demonstrate that proton NMR noise signals, i.e. NMR spectra without excitation by radio freque... more We demonstrate that proton NMR noise signals, i.e. NMR spectra without excitation by radio frequency, can be obtained from solid samples. Experimental results are shown for static and magic-angle spinning conditions. In addition, a tuning procedure based on the probes' NMR noise characteristics and similar to the one described previously for liquids probes can also be used to optimize signal-to-noise ratios in 1 H-MAS experiments.
The Journal of Physical Chemistry B, 2009
The dependence of the effective chemical shielding anisotropy (effective CSA, Δσ eff ) on the and... more The dependence of the effective chemical shielding anisotropy (effective CSA, Δσ eff ) on the and ψ peptide backbone torsion angles was calculated in the L-alanyl-L-alanine (LALA) peptide using the DFT method. The effects of backbone conformation, molecular charge including the cation, zwitterion, and anion forms of the LALA peptide, and the scaling taking into account the length of the dipolar vector were calculated for the effective CSAs in order to assess their structural behaviors and to predict their magnitudes which can be probed for the -sheet and R-helix backbone conformations via measurement of the cross-correlated relaxation rates (CCR rates). Twenty different CSA-DD cross-correlation mechanisms involving the amide nitrogen and carbonyl carbon chemical shielding tensors and the C R H R (R-carbon group), NH N (amide group), C R H N , NH R , C′H R , and C′H N (R ) R1, R2) dipolar vectors were investigated. The X-C R H R (X ) N, C′; R ) R1, R2) cross-correlations, which had already been studied experimentally, exhibited overall best performance of the calculated effective CSAs in the LALA molecule; they spanned the largest range of values upon variation of the ψ and torsions and depended dominantly on only one of the two backbone torsion angles. The X-NH N (X ) N, C′) cross-correlations, which had been also probed experimentally, depended on both backbone torsions, which makes their structural assignment more difficult. The N-NH R2 and N-C′H R1 crosscorrelations were found to be promising for the determination of various backbone conformations due to the large calculated range of the scaled effective CSA values and due to their predominant dependence on the ψ and torsions, respectively. The 20 calculated dependencies of effective CSAs on the two backbone torsion angles can facilitate the structural interpretation of CCR rates.
Journal of Molecular Structure, 1995
Deuterium isotope effects on 13C chemical shifts have been determined in a series of monodeuteria... more Deuterium isotope effects on 13C chemical shifts have been determined in a series of monodeuteriated trans-N-benzylideneanilines. The effects over two bonds (2Δ) observed at C-1 and over three bonds (3Δ) observed at C-2,6 are sensitive to steric interactions involving nitrogen lone-pair electrons and C-Ph ortho-protons. Like in similar π-electron systems, the effect over six bonds (6Δ) is related to molecular
AIP Conference Proceedings, 1995
Journal of Natural Products, 2009
New brominated anthraquinone pigments, proisocrinins A-F (1-6), were isolated from the strikingly... more New brominated anthraquinone pigments, proisocrinins A-F (1-6), were isolated from the strikingly scarlet-colored stalked crinoid Proisocrinus ruberrimus, which had been collected in the deep sea of the Okinawa Trough, Japan. The structures of the compounds were elucidated by spectroscopic analysis including HRMS, 1D 1H and 13C NMR, and 2D NMR. CD spectroscopy revealed that all compounds are present as optically active enantiomers. This is the first report of tribromo and tetrabromo anthraquinones from a natural source.
The Journal of Chemical Physics, 1993
A group spin approach is used to describe the interconversion of magnetization modes in systems o... more A group spin approach is used to describe the interconversion of magnetization modes in systems of three equivalent spins 1/2. It is shown that the most prominent effect of cross correlation of the fluctuations of chemical shift anisotropy and dipolar interactions is the transformation of two-quantum coherences of second rank into third rank coherences. A novel experiment is described which allows one to observe such a process.
Journal of Agricultural and Food Chemistry, 2008
Four derivatives of thymol, carvacrol, and eugenol were synthesized: 4-(hydroxymethyl)-5-isopropy... more Four derivatives of thymol, carvacrol, and eugenol were synthesized: 4-(hydroxymethyl)-5-isopropyl-2-methylphenol, 4,4′-methylenebis(5-isopropyl-2-methyl)phenol, 4-allyl-6-(hydroxymethyl)-2-methoxyphenol, and 4-(hydroxymethyl)-2-isopropyl-5-methylphenol. The obtained derivatives showed remarkably better antioxidative properties according to 1,1-diphenyl-2-picrylhydrazyl assay (50% inhibitory concentrations ) 4-156 µg/mL) and Rancimat assay (protection factors ) 1.55-5.84) when compared with parent compounds and values similar to or better than those of butylated hydroxytoluene and vitamin C. At concentrations of 10 mM carvacrol derivatives had no toxic effect on viability of Escherichia coli K-12 (determined by minimum inhibitory concentrations). Other phenol derivatives showed reduced cytotoxic effect on E. coli K-12 at concentrations of 2-5 mM on the basis of 50% lethal dose measurements. In comparison with the parent compounds, phenol derivatives showed reduced cytotoxic effect for Saccharomyces cerevisiae cells (determined by yeast colony reduction). On the other hand, the majority of synthesized compounds had dose-dependent antiproliferative effects on human uterine carcinoma cells (HeLa), which makes them potentially interesting for the adjuvant experimental cancer treatments. The 4,4′-methylenebis(5-isopropyl-2-methyl)phenol derivative of carvacrol showed lower inhibiting capacity also for the HeLa cells, which makes this particular derivative attractive as an efficient antioxidant with negligible cytotoxic effects.
Journal of Magnetic Resonance, 2009
We have systematically investigated the line shapes observed in proton nuclear spinnoise spectra ... more We have systematically investigated the line shapes observed in proton nuclear spinnoise spectra which depend in a complex way on the properties of the resonance circuit, the number of spins present, transverse relaxation, inhomogeneous broadening, and radiation damping. Using highly sensitive high resolution probes these dependencies are investigated by way of high resolution 1 H noise power NMR spectra of liquid samples. Significant deviations from intuitive expectations are observed. Simulations based on an adapted Nyquist noise equation are used to understand and interpret the experimental findings.
Journal of Magnetic Resonance, 2009
We have systematically investigated the line shapes observed in proton nuclear spinnoise spectra ... more We have systematically investigated the line shapes observed in proton nuclear spinnoise spectra which depend in a complex way on the properties of the resonance circuit, the number of spins present, transverse relaxation, inhomogeneous broadening, and radiation damping. Using highly sensitive high resolution probes these dependencies are investigated by way of high resolution 1 H noise power NMR spectra of liquid samples. Significant deviations from intuitive expectations are observed. Simulations based on an adapted Nyquist noise equation are used to understand and interpret the experimental findings.
Journal of Biomolecular NMR, 2010
We have assessed the potential of an alternative probe tuning strategy based on the spin-noise re... more We have assessed the potential of an alternative probe tuning strategy based on the spin-noise response for application in common high-resolution multi-dimensional biomolecular NMR experiments with water signal suppression on aqueous and salty samples. The method requires the adjustment of the optimal tuning condition, which may be offset by several 100 kHz from the conventional tuning settings using the noise response of the water protons as an indicator. Although the radio frequency-pulse durations are typically longer under such conditions, signal-to-noise gains of up to 22% were achieved. At salt concentrations up to 100 mM a substantial sensitivity gain was observed.
Analytical and Bioanalytical Chemistry, 2004
Nano-electrospray-ionization mass spectrometry (nano-ESI-MS) is employed here to describe equilib... more Nano-electrospray-ionization mass spectrometry (nano-ESI-MS) is employed here to describe equilibrium protein conformational transitions and to analyze the influence of instrumental settings, pH, and solvent surface tension on the charge-state distributions (CSD). A first set of experiments shows that high flow rates of N(2) as curtain gas can induce unfolding of cytochrome c (cyt c) and myoglobin (Mb), under conditions in which the stability of the native protein structure has already been reduced by acidification. However, it is possible to identify conditions under which the instrumental settings are not limiting factors for the conformational stability of the protein inside ESI droplets. Under such conditions, equilibrium unfolding transitions described by ESI-MS are comparable with those obtained by other established biophysical methods. Experiments with the very stable proteins ubiquitin (Ubq) and lysozyme (Lyz) enable testing of the influence of extreme pH changes on the ESI process, uncoupled from acid-induced unfolding. When HCl is used for acidification, Ubq and Lyz mass spectra do not change between pH~7 and pH 2.2, indicating that the CSD is highly characteristic of a given protein conformation and not directly affected by even large pH changes. Use of formic or acetic acid for acidification of Ubq solutions results in major spectral changes that can be interpreted in terms of protein unfolding as a result of the increased hydrophobicity of the solvent. On the other hand, Lyz, cyt c, and Mb enable direct comparison of protein CSD (corresponding to either the folded or the unfolded protein) in HCl or acetic acid solutions at low pH. The values of surface tension for these solutions differ significantly. Confirming indications already present in the literature, we observe very similar CSD under these solvent conditions for several proteins in either compact or disordered conformations. The same is true for comparison between water and water-acetic acid for folded cyt c and Lyz. Thus, protein CSD from water-acetic solutions do not seem to be limited by the low surface tension of acetic acid as previously suggested. This result could reflect a general lack of dependence of protein CSD on the surface tension of the solvent. However, it is also possible that the effect of acetic acid on the precursor ESI droplets is smaller than generally assumed.
We demonstrate that proton NMR noise signals, i.e. NMR spectra without excitation by radio freque... more We demonstrate that proton NMR noise signals, i.e. NMR spectra without excitation by radio frequency, can be obtained from solid samples. Experimental results are shown for static and magic-angle spinning conditions. In addition, a tuning procedure based on the probes' NMR noise characteristics and similar to the one described previously for liquids probes can also be used to optimize signal-to-noise ratios in 1 H-MAS experiments.
The Journal of Physical Chemistry B, 2009
The dependence of the effective chemical shielding anisotropy (effective CSA, Δσ eff ) on the and... more The dependence of the effective chemical shielding anisotropy (effective CSA, Δσ eff ) on the and ψ peptide backbone torsion angles was calculated in the L-alanyl-L-alanine (LALA) peptide using the DFT method. The effects of backbone conformation, molecular charge including the cation, zwitterion, and anion forms of the LALA peptide, and the scaling taking into account the length of the dipolar vector were calculated for the effective CSAs in order to assess their structural behaviors and to predict their magnitudes which can be probed for the -sheet and R-helix backbone conformations via measurement of the cross-correlated relaxation rates (CCR rates). Twenty different CSA-DD cross-correlation mechanisms involving the amide nitrogen and carbonyl carbon chemical shielding tensors and the C R H R (R-carbon group), NH N (amide group), C R H N , NH R , C′H R , and C′H N (R ) R1, R2) dipolar vectors were investigated. The X-C R H R (X ) N, C′; R ) R1, R2) cross-correlations, which had already been studied experimentally, exhibited overall best performance of the calculated effective CSAs in the LALA molecule; they spanned the largest range of values upon variation of the ψ and torsions and depended dominantly on only one of the two backbone torsion angles. The X-NH N (X ) N, C′) cross-correlations, which had been also probed experimentally, depended on both backbone torsions, which makes their structural assignment more difficult. The N-NH R2 and N-C′H R1 crosscorrelations were found to be promising for the determination of various backbone conformations due to the large calculated range of the scaled effective CSA values and due to their predominant dependence on the ψ and torsions, respectively. The 20 calculated dependencies of effective CSAs on the two backbone torsion angles can facilitate the structural interpretation of CCR rates.