The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Pierre Wins - One of the best experts on this subject based on the ideXlab platform.
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thiaminylated adenine nucleotides chemical synthesis structural characterization and natural occurrence
FEBS Journal, 2009Co-Authors: Michel Frederich, Tiziana Gigliobianco, Gabriel Mazzucchelli, Luc Angenot, Marjorie Gangolf, Edwin De Pauw, David Delvaux, Georges Dive, Benjamin Elias, Pierre WinsAbstract:Thiamine and its three phosphorylated derivatives (mono-, di- and triphosphate) occur naturally in most cells. Recently, we reported the presence of a fourth thiamine derivative, adenosine thiamine triphosphate, produced in Escherichia coli in response to carbon starvation. Here, we show that the chemical synthesis of adenosine thiamine triphosphate leads to another new compound, adenosine thiamine diphosphate, as a side product. The structure of both compounds was confirmed by MS analysis and H-1-, C-13- and P-31-NMR, and some of their chemical properties were determined. Our results show an upfield shifting of the C-2 proton of the thiazolium ring in adenosine thiamine derivatives compared with conventional thiamine phosphate derivatives. This modification of the electronic environment of the C-2 proton might be explained by a Through-Space Interaction with the adenosine moiety, suggesting U-shaped folding of adenosine thiamine derivatives. Such a structure in which the C-2 proton is embedded in a closed conformation can be located using molecular modeling as an energy minimum. In E. coli, adenosine thiamine triphosphate may account for 15% of the total thiamine under energy stress. It is less abundant in eukaryotic organisms, but is consistently found in mammalian tissues and some cell lines. Using HPLC, we show for the first time that adenosine thiamine diphosphate may also occur in small amounts in E. coli and in vertebrate liver. The discovery of two natural thiamine adenine compounds further highlights the complexity and diversity of thiamine biochemistry, which is not restricted to the cofactor role of thiamine diphosphate.
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Thiaminylated adenine nucleotides — chemical synthesis, structural characterization and natural occurrence
The FEBS journal, 2009Co-Authors: Michel Frederich, Tiziana Gigliobianco, Gabriel Mazzucchelli, Luc Angenot, Marjorie Gangolf, Edwin De Pauw, David Delvaux, Georges Dive, Benjamin Elias, Pierre WinsAbstract:Thiamine and its three phosphorylated derivatives (mono-, di- and triphosphate) occur naturally in most cells. Recently, we reported the presence of a fourth thiamine derivative, adenosine thiamine triphosphate, produced in Escherichia coli in response to carbon starvation. Here, we show that the chemical synthesis of adenosine thiamine triphosphate leads to another new compound, adenosine thiamine diphosphate, as a side product. The structure of both compounds was confirmed by MS analysis and H-1-, C-13- and P-31-NMR, and some of their chemical properties were determined. Our results show an upfield shifting of the C-2 proton of the thiazolium ring in adenosine thiamine derivatives compared with conventional thiamine phosphate derivatives. This modification of the electronic environment of the C-2 proton might be explained by a Through-Space Interaction with the adenosine moiety, suggesting U-shaped folding of adenosine thiamine derivatives. Such a structure in which the C-2 proton is embedded in a closed conformation can be located using molecular modeling as an energy minimum. In E. coli, adenosine thiamine triphosphate may account for 15% of the total thiamine under energy stress. It is less abundant in eukaryotic organisms, but is consistently found in mammalian tissues and some cell lines. Using HPLC, we show for the first time that adenosine thiamine diphosphate may also occur in small amounts in E. coli and in vertebrate liver. The discovery of two natural thiamine adenine compounds further highlights the complexity and diversity of thiamine biochemistry, which is not restricted to the cofactor role of thiamine diphosphate.
Michel Frederich - One of the best experts on this subject based on the ideXlab platform.
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thiaminylated adenine nucleotides chemical synthesis structural characterization and natural occurrence
FEBS Journal, 2009Co-Authors: Michel Frederich, Tiziana Gigliobianco, Gabriel Mazzucchelli, Luc Angenot, Marjorie Gangolf, Edwin De Pauw, David Delvaux, Georges Dive, Benjamin Elias, Pierre WinsAbstract:Thiamine and its three phosphorylated derivatives (mono-, di- and triphosphate) occur naturally in most cells. Recently, we reported the presence of a fourth thiamine derivative, adenosine thiamine triphosphate, produced in Escherichia coli in response to carbon starvation. Here, we show that the chemical synthesis of adenosine thiamine triphosphate leads to another new compound, adenosine thiamine diphosphate, as a side product. The structure of both compounds was confirmed by MS analysis and H-1-, C-13- and P-31-NMR, and some of their chemical properties were determined. Our results show an upfield shifting of the C-2 proton of the thiazolium ring in adenosine thiamine derivatives compared with conventional thiamine phosphate derivatives. This modification of the electronic environment of the C-2 proton might be explained by a Through-Space Interaction with the adenosine moiety, suggesting U-shaped folding of adenosine thiamine derivatives. Such a structure in which the C-2 proton is embedded in a closed conformation can be located using molecular modeling as an energy minimum. In E. coli, adenosine thiamine triphosphate may account for 15% of the total thiamine under energy stress. It is less abundant in eukaryotic organisms, but is consistently found in mammalian tissues and some cell lines. Using HPLC, we show for the first time that adenosine thiamine diphosphate may also occur in small amounts in E. coli and in vertebrate liver. The discovery of two natural thiamine adenine compounds further highlights the complexity and diversity of thiamine biochemistry, which is not restricted to the cofactor role of thiamine diphosphate.
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Thiaminylated adenine nucleotides — chemical synthesis, structural characterization and natural occurrence
The FEBS journal, 2009Co-Authors: Michel Frederich, Tiziana Gigliobianco, Gabriel Mazzucchelli, Luc Angenot, Marjorie Gangolf, Edwin De Pauw, David Delvaux, Georges Dive, Benjamin Elias, Pierre WinsAbstract:Thiamine and its three phosphorylated derivatives (mono-, di- and triphosphate) occur naturally in most cells. Recently, we reported the presence of a fourth thiamine derivative, adenosine thiamine triphosphate, produced in Escherichia coli in response to carbon starvation. Here, we show that the chemical synthesis of adenosine thiamine triphosphate leads to another new compound, adenosine thiamine diphosphate, as a side product. The structure of both compounds was confirmed by MS analysis and H-1-, C-13- and P-31-NMR, and some of their chemical properties were determined. Our results show an upfield shifting of the C-2 proton of the thiazolium ring in adenosine thiamine derivatives compared with conventional thiamine phosphate derivatives. This modification of the electronic environment of the C-2 proton might be explained by a Through-Space Interaction with the adenosine moiety, suggesting U-shaped folding of adenosine thiamine derivatives. Such a structure in which the C-2 proton is embedded in a closed conformation can be located using molecular modeling as an energy minimum. In E. coli, adenosine thiamine triphosphate may account for 15% of the total thiamine under energy stress. It is less abundant in eukaryotic organisms, but is consistently found in mammalian tissues and some cell lines. Using HPLC, we show for the first time that adenosine thiamine diphosphate may also occur in small amounts in E. coli and in vertebrate liver. The discovery of two natural thiamine adenine compounds further highlights the complexity and diversity of thiamine biochemistry, which is not restricted to the cofactor role of thiamine diphosphate.
Hiroshi Nakanishi - One of the best experts on this subject based on the ideXlab platform.
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Conformationally favored CH---O intramolecular Interaction and restricted rotation in sterically crowded ester
Tetrahedron Letters, 1998Co-Authors: Yoshinobu Nagawa, Tohru Yamagaki, Hiroshi Nakanishi, Masatoshi Nakagawa, Takahiro TezukaAbstract:Abstract Restricted rotation of a sterically crowded ester, which has two tert -butyl groups and one isopropyl group, was studied by dynamic NMR spectroscopy. The intramolecular Through-Space Interaction between the methine hydrogen of the isopropyl group and the carbonyl oxygen exists in the ester. Bulky alkyl substituents in close proximity cause both restricted rotation of the C(sp 3 )C(sp 3 ) single bond and CH---O intramolecular Interaction.
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Studies of steric effects. Spectroscopic evidence for Through-Space Interaction in CH3 …. O in crowded alcohols
Tetrahedron Letters, 1997Co-Authors: Takahiro Tezuka, Yoshinobu Nagawa, Tohru Yamagaki, Masatoshi Nakagawa, Koji Yokoi, Hiroshi NakanishiAbstract:Abstract Through-Space Interaction of the γ-methyl hydrogen with the oxygen atom in crowded tertiary aliphatic alcohols generates an abnormally low-field chemical shift in the 17 O NMR spectra. The intramolecular Through-Space attractive Interaction or hydrogen bonding Interaction between the γ-methyl hydrogen and the oxygen lone pair (CH 3 …. O) is proposed as the cause of this shift. By this Interaction, the less polar CO bond is generated.
Michael R Wasielewski - One of the best experts on this subject based on the ideXlab platform.
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fluorescence dynamics of chlorophyll trefoils in the solid state studied by single molecule fluorescence spectroscopy
Journal of Physical Chemistry Letters, 2010Co-Authors: Jaesung Yang, Victoria L Gunderson, Michael R WasielewskiAbstract:We have comparatively investigated the single-molecule photophysical properties of two chlorophyll trefoils that feature distinctive electronic couplings induced by differences in linkage: one is an ethynyl-linked chlorophyll trefoil (1) in which relatively short and rigid linkage between the chromophores promotes effective electronic coupling, and the other is a phenyl−ethynyl-linked chlorophyll trefoil (2) in which the phenyl addition induces an orthogonal geometry impeding π-conjugation and provides a longer interchlorophyll distance reducing Through-Space Interaction. By recording single-molecule fluorescence intensity trajectories and their corresponding lifetimes, we observed one-step photobleaching behaviors, less frequent on−off behaviors, a narrower fluorescence lifetime distribution, and higher photostability in 1 as compared with 2. These results indicate that the performance of molecular photosynthetic systems in the solid state is strongly associated with electronic couplings and, thus, give ...
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Factoring Through-Space and through-bond contributions to rates of photoinduced electron transfer in donor-spacer-acceptor molecules
Journal of Photochemistry and Photobiology A: Chemistry, 1996Co-Authors: David J. Gosztola, Bing Wang, Michael R WasielewskiAbstract:Abstract Contributions from direct orbital overlap (Through-Space Interactions) and superexchange (through-bond Interactions) to the electronic coupling matrix elements for photoinduced charge separation and recombination in a series of linked donor—spacer—acceptor molecules were studied. The molecules consisted of a 4-piperidinyl-naphthalene-1,8-dicarboximide (ANI) electron donor and a N -(n-octyl)pyromellitimide (PI) electron acceptor attached to the 1,5- and 1,8-positions of either anthracene (ANC) or dibenzobicyclo(2.2.2)octatriene (DBO) spacers. For the 1,8-disubstituted compounds, ANI and PI are held approximately cofacial with a center-to-center distance of 5.3 A, whereas for the 1,5-disubstituted compounds, the center-to-center distance increases to 13.5 A. The through-bond Interaction was investigated by replacing the ANC spacer with DBO. The charge separation and recombination reactions were examined in both toluene and tetrahydrofuran (THF). The results show that for the 1,8-disubstituted DBO system in both toluene and THF, charge separation and recombination is dominated by Through-Space Interactions. For the 1,8-disubstituted ANC system in both toluene and THF, charge separation occurs by means of a direct, Through-Space Interaction, while charge recombination occurs through the intermediacy of the ANI ANC + PI - ion pair in toluene and directly from ANI + ANC PI - to ground state in THF. For the 1,5-disubstituted molecules, possessing either the ANC or the DBO spacers, electron transfer from 1* ANI to PI was not kinetically competitive with the decay of 1* ANI to ground state in either toluene or THF.
Edwin De Pauw - One of the best experts on this subject based on the ideXlab platform.
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thiaminylated adenine nucleotides chemical synthesis structural characterization and natural occurrence
FEBS Journal, 2009Co-Authors: Michel Frederich, Tiziana Gigliobianco, Gabriel Mazzucchelli, Luc Angenot, Marjorie Gangolf, Edwin De Pauw, David Delvaux, Georges Dive, Benjamin Elias, Pierre WinsAbstract:Thiamine and its three phosphorylated derivatives (mono-, di- and triphosphate) occur naturally in most cells. Recently, we reported the presence of a fourth thiamine derivative, adenosine thiamine triphosphate, produced in Escherichia coli in response to carbon starvation. Here, we show that the chemical synthesis of adenosine thiamine triphosphate leads to another new compound, adenosine thiamine diphosphate, as a side product. The structure of both compounds was confirmed by MS analysis and H-1-, C-13- and P-31-NMR, and some of their chemical properties were determined. Our results show an upfield shifting of the C-2 proton of the thiazolium ring in adenosine thiamine derivatives compared with conventional thiamine phosphate derivatives. This modification of the electronic environment of the C-2 proton might be explained by a Through-Space Interaction with the adenosine moiety, suggesting U-shaped folding of adenosine thiamine derivatives. Such a structure in which the C-2 proton is embedded in a closed conformation can be located using molecular modeling as an energy minimum. In E. coli, adenosine thiamine triphosphate may account for 15% of the total thiamine under energy stress. It is less abundant in eukaryotic organisms, but is consistently found in mammalian tissues and some cell lines. Using HPLC, we show for the first time that adenosine thiamine diphosphate may also occur in small amounts in E. coli and in vertebrate liver. The discovery of two natural thiamine adenine compounds further highlights the complexity and diversity of thiamine biochemistry, which is not restricted to the cofactor role of thiamine diphosphate.
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Thiaminylated adenine nucleotides — chemical synthesis, structural characterization and natural occurrence
The FEBS journal, 2009Co-Authors: Michel Frederich, Tiziana Gigliobianco, Gabriel Mazzucchelli, Luc Angenot, Marjorie Gangolf, Edwin De Pauw, David Delvaux, Georges Dive, Benjamin Elias, Pierre WinsAbstract:Thiamine and its three phosphorylated derivatives (mono-, di- and triphosphate) occur naturally in most cells. Recently, we reported the presence of a fourth thiamine derivative, adenosine thiamine triphosphate, produced in Escherichia coli in response to carbon starvation. Here, we show that the chemical synthesis of adenosine thiamine triphosphate leads to another new compound, adenosine thiamine diphosphate, as a side product. The structure of both compounds was confirmed by MS analysis and H-1-, C-13- and P-31-NMR, and some of their chemical properties were determined. Our results show an upfield shifting of the C-2 proton of the thiazolium ring in adenosine thiamine derivatives compared with conventional thiamine phosphate derivatives. This modification of the electronic environment of the C-2 proton might be explained by a Through-Space Interaction with the adenosine moiety, suggesting U-shaped folding of adenosine thiamine derivatives. Such a structure in which the C-2 proton is embedded in a closed conformation can be located using molecular modeling as an energy minimum. In E. coli, adenosine thiamine triphosphate may account for 15% of the total thiamine under energy stress. It is less abundant in eukaryotic organisms, but is consistently found in mammalian tissues and some cell lines. Using HPLC, we show for the first time that adenosine thiamine diphosphate may also occur in small amounts in E. coli and in vertebrate liver. The discovery of two natural thiamine adenine compounds further highlights the complexity and diversity of thiamine biochemistry, which is not restricted to the cofactor role of thiamine diphosphate.