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Mark Cushman - One of the best experts on this subject based on the ideXlab platform.
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a new series of 3 Alkyl Phosphate derivatives of 4 5 6 7 tetrahydro 1 d ribityl 1h pyrazolo 3 4 d pyrimidinedione as inhibitors of lumazine synthase design synthesis and evaluation
Journal of Organic Chemistry, 2007Co-Authors: Yanlei Zhang, A. Bacher, Markus Fischer, Boris Illarionov, Guangyi Jin, Mark CushmanAbstract:Lumazine synthase catalyzes the penultimate step in the biosynthesis of riboflavin. A homologous series of three pyrazolopyrimidine analogues of a hypothetical intermediate in the lumazine synthase-catalyzed reaction were synthesized and evaluated as lumazine synthase inhibitors. The key steps of the synthesis were C-5 deprotonation of 4-chloro-2,6-dimethoxypyrimidine, acylation of the resulting anion, and conversion of the product to a pyrazolopyrimidine with hydrazine. Alkylation of the pyrazolopyrimidine with a substituted ribityl iodide and deprotection of the ribityl chain afforded the final set of three products. All three compounds were extremely potent inhibitors of the lumazine synthases of Mycobacterium tuberculosis, Magnaporthe grisea, Candida albicans, and Schizosaccharomyces pombe lumazine synthase, with inhibition constants in the low nanomolar to subnanomolar range. Molecular modeling of one of the homologues bound to Mycobacterium tuberculosis lumazine synthase suggests that both the hypothetical intermediate in the lumazine synthase-catalyzed reaction pathway and the metabolically stable analogues bind similarly.
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design synthesis and biochemical evaluation of 1 5 6 7 tetrahydro 6 7 dioxo 9 d ribitylaminolumazines bearing Alkyl Phosphate substituents as inhibitors of lumazine synthase and riboflavin synthase
ChemInform, 2005Co-Authors: Mark Cushman, Markus Fischer, Rudolf Ladenstein, Boris Illarionov, Guangyi Jin, A. BacherAbstract:The last two steps in the biosynthesis of riboflavin, an essential metabolite that is involved in electron transport, are catalyzed by lumazine synthase and riboflavin synthase. To obtain structural probes and inhibitors of these two enzymes, two ribityllumazinediones bearing Alkyl Phosphate substituents were synthesized. The synthesis involved the generation of the ribityl side chain, the Phosphate side chain, and the lumazine system in protected form, followed by the simultaneous removal of three different types of protecting groups. The products were designed as intermediate analogue inhibitors of lumazine synthase that would bind to its Phosphate-binding site as well as its lumazine binding site. Both compounds were found to be effective inhibitors of Bacillus subtilis lumazine synthase as well as Escherichia coli riboflavin synthase. Molecular modeling of the binding of one of the two compounds provided a structural explanation for how these compounds are able to effectively inhibit both enzymes. In ...
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design synthesis and evaluation of 9 d ribitylamino 1 3 7 9 tetrahydro 2 6 8 purinetriones bearing Alkyl Phosphate and α α difluorophosphonate substituents as inhibitors of riboflavin synthase and lumazine synthase
Journal of Organic Chemistry, 2004Co-Authors: Mark Cushman, Markus Fischer, Boris Illarionov, Guangyi Jin, Thota Sambaiah, A. BacherAbstract:Lumazine synthase and riboflavin synthase catalyze the last two steps in the biosynthesis of riboflavin, an essential metabolite that is involved in electron transport processes. To obtain structural probes of these two enzymes, as well as inhibitors of potential value as antibiotics, a series of ribitylpurinetriones bearing Alkyl Phosphate and α,α-difluorophosphonate substituents were synthesized. Since the purinetrione ring system and the ribityl hydroxyl groups can be Alkylated, the synthesis required the generation of these two moieties in protected form before the desired Alkylation reaction could be carried out. These substances were designed as intermediate analogue inhibitors of lumazine synthase that would bind to its Phosphate-binding site. All of the compounds were found to be effective inhibitors of both Bacillus subtilis lumazine synthase as well as Escherichia coli riboflavin synthase. Molecular modeling of the binding of 3-(1,3,7,9-tetrahydro-9-d-ribityl-2,6,8-trioxopurin-7-yl)propane 1-pho...
A. Bacher - One of the best experts on this subject based on the ideXlab platform.
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a new series of 3 Alkyl Phosphate derivatives of 4 5 6 7 tetrahydro 1 d ribityl 1h pyrazolo 3 4 d pyrimidinedione as inhibitors of lumazine synthase design synthesis and evaluation
Journal of Organic Chemistry, 2007Co-Authors: Yanlei Zhang, A. Bacher, Markus Fischer, Boris Illarionov, Guangyi Jin, Mark CushmanAbstract:Lumazine synthase catalyzes the penultimate step in the biosynthesis of riboflavin. A homologous series of three pyrazolopyrimidine analogues of a hypothetical intermediate in the lumazine synthase-catalyzed reaction were synthesized and evaluated as lumazine synthase inhibitors. The key steps of the synthesis were C-5 deprotonation of 4-chloro-2,6-dimethoxypyrimidine, acylation of the resulting anion, and conversion of the product to a pyrazolopyrimidine with hydrazine. Alkylation of the pyrazolopyrimidine with a substituted ribityl iodide and deprotection of the ribityl chain afforded the final set of three products. All three compounds were extremely potent inhibitors of the lumazine synthases of Mycobacterium tuberculosis, Magnaporthe grisea, Candida albicans, and Schizosaccharomyces pombe lumazine synthase, with inhibition constants in the low nanomolar to subnanomolar range. Molecular modeling of one of the homologues bound to Mycobacterium tuberculosis lumazine synthase suggests that both the hypothetical intermediate in the lumazine synthase-catalyzed reaction pathway and the metabolically stable analogues bind similarly.
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design synthesis and biochemical evaluation of 1 5 6 7 tetrahydro 6 7 dioxo 9 d ribitylaminolumazines bearing Alkyl Phosphate substituents as inhibitors of lumazine synthase and riboflavin synthase
ChemInform, 2005Co-Authors: Mark Cushman, Markus Fischer, Rudolf Ladenstein, Boris Illarionov, Guangyi Jin, A. BacherAbstract:The last two steps in the biosynthesis of riboflavin, an essential metabolite that is involved in electron transport, are catalyzed by lumazine synthase and riboflavin synthase. To obtain structural probes and inhibitors of these two enzymes, two ribityllumazinediones bearing Alkyl Phosphate substituents were synthesized. The synthesis involved the generation of the ribityl side chain, the Phosphate side chain, and the lumazine system in protected form, followed by the simultaneous removal of three different types of protecting groups. The products were designed as intermediate analogue inhibitors of lumazine synthase that would bind to its Phosphate-binding site as well as its lumazine binding site. Both compounds were found to be effective inhibitors of Bacillus subtilis lumazine synthase as well as Escherichia coli riboflavin synthase. Molecular modeling of the binding of one of the two compounds provided a structural explanation for how these compounds are able to effectively inhibit both enzymes. In ...
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design synthesis and evaluation of 9 d ribitylamino 1 3 7 9 tetrahydro 2 6 8 purinetriones bearing Alkyl Phosphate and α α difluorophosphonate substituents as inhibitors of riboflavin synthase and lumazine synthase
Journal of Organic Chemistry, 2004Co-Authors: Mark Cushman, Markus Fischer, Boris Illarionov, Guangyi Jin, Thota Sambaiah, A. BacherAbstract:Lumazine synthase and riboflavin synthase catalyze the last two steps in the biosynthesis of riboflavin, an essential metabolite that is involved in electron transport processes. To obtain structural probes of these two enzymes, as well as inhibitors of potential value as antibiotics, a series of ribitylpurinetriones bearing Alkyl Phosphate and α,α-difluorophosphonate substituents were synthesized. Since the purinetrione ring system and the ribityl hydroxyl groups can be Alkylated, the synthesis required the generation of these two moieties in protected form before the desired Alkylation reaction could be carried out. These substances were designed as intermediate analogue inhibitors of lumazine synthase that would bind to its Phosphate-binding site. All of the compounds were found to be effective inhibitors of both Bacillus subtilis lumazine synthase as well as Escherichia coli riboflavin synthase. Molecular modeling of the binding of 3-(1,3,7,9-tetrahydro-9-d-ribityl-2,6,8-trioxopurin-7-yl)propane 1-pho...
Masayuki Morita - One of the best experts on this subject based on the ideXlab platform.
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fluorinated Alkyl Phosphate based electrolytes with controlled lithium ion coordination structure
Physical Chemistry Chemical Physics, 2019Co-Authors: Saki Sawayama, Masayuki Morita, Yanko Todorov, Hideyuki Mimura, Kenta FujiiAbstract:Herein, we propose Li-ion solvation-controlled electrolytes based on non-flammable organic solvent TFEP and an LiFSA salt [TFEP: tris(2,2,2-trifluoroethyl)Phosphate, LiFSA: lithium bis(fluorosulfonyl)amide] to allow Li-ion insertion into a graphite electrode for Li-ion batteries. Comprehensive structural study based on (1) infrared (IR)/Raman spectroscopy, (2) high-energy X-ray total scattering (HEXTS), and (3) molecular dynamics (MD) simulation revealed the solvation (or coordination) structures of Li ions in TFEP-based electrolytes at the molecular level. In binary LiFSA/TFEP with a Li salt concentration (cLi) < 1.0 mol dm−3, Li ions are coordinated with both TFEP and FSA components; in detail, two TFEP molecules coordinate in an O-donating monodentate manner and one FSA in an O-donating bidentate manner to form [Li(TFEP)2(bi-FSA)] as the major species. We demonstrated that adding acetonitrile (AN) to the LiFSA/TFEP electrolytes caused structural changes in the Li-ion complexes. The bi-FSA bound to the Li ion changed its coordination mode to mono-FSA, which was induced by solvating AN molecules to Li ions. The redox reaction corresponding to insertion/deinsertion of Li ions into/from the graphite electrode successfully occurred in 1.0 mol dm−3 LiFSA/TFEP with an AN electrolyte system, while there was no or reduced Li-ion insertion in the electrolyte without AN. We discussed the relationship between the structure and electrode reaction of the Li-ion complexes based on the FSA-coordination characteristics; i.e., in LiFSA/TFEP with the AN system, the mono-FSA bound to the Li ion is easier to decoordinate due to weaker Li+⋯mono-FSA− interactions rather than the Li+⋯bi-FSA− interactions, which mainly contribute to charge-transfer at the electrode/electrolyte interface to allow Li-ion insertion/deinsertion in the graphite anode.
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electrochemical properties of a tetrapeg based gel electrolyte containing a nonflammable fluorinated Alkyl Phosphate for safer lithium ion batteries
Chemistry Letters, 2018Co-Authors: Jihae Han, Nobuko Yoshimoto, Masayuki Morita, Mari Yoshitake, Takamasa Sakai, Kenta FujiiAbstract:We report a nonflammable gel electrolyte based on two key soft materials: 1) a homogeneous polymer network prepared from tetra-armed poly(ethylene glycol) (TetraPEG) and 2) a tris(2,2,2-trifluoroethyl)Phosphate (TFEP)-based electrolyte solution. At the equilibrium swelling state, the concentration of the polymer in the TetraPEG gel was relatively low, at only 5.6 wt.%. The TetraPEG gel exhibits a wide electrochemical window of ∼5.0 V and thus works well as an electrolyte for a positive electrode, i.e., a lithium iron Phosphate (LiFePO4).
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role of solvent bulkiness on lithium ion solvation in fluorinated Alkyl Phosphate based electrolytes structural study for designing nonflammable lithium ion batteries
Journal of Physical Chemistry C, 2017Co-Authors: Michiru Sogawa, Nobuko Yoshimoto, Masayuki Morita, Yanko Todorov, Hideyuki Mimura, Daisuke Hirayama, Kenta FujiiAbstract:We report the characteristics of nonflammable tris(2,2,2-trifluoroethyl) Phosphate (TFEP) as a nonaqueous solvent for lithium (Li)-ion battery electrolytes at a molecular level, particularly focusing on the solvent parameters, such as the electron pair-donating ability and molecular bulkiness of TFEP, and the solvation behavior around Li ions. The binding energy for the interactions between a Li ion and several solvents using density functional theory (DFT) calculations indicated that TFEP can be categorized as a nonaqueous solvent with weak electron pair-donating ability, resulting in the prediction of a small Gutmann’s donor number (the DN value is approximately 12.9). The Walden plots based on ionic conductivity and viscosity suggested that Li ions tend to exist as contact ion pairs (Li+···TFSA–) in the TFEP-based solutions, irrespective of the Li salt concentration cLi. Infrared and Raman spectroscopic studies demonstrated that Li ions are solvated by two TFEP molecules and one TFSA anion to form the ...
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nonflammable gel electrolyte containing Alkyl Phosphate for rechargeable lithium batteries
Journal of Power Sources, 2006Co-Authors: Nobuko Yoshimoto, Yoshihiro Niida, Minato Egashira, Masayuki MoritaAbstract:Abstract A nonflammable polymeric gel electrolyte has been developed for rechargeable lithium battery systems. The gel film consists of poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP) swollen with lithium hexafluoroPhosphate (LiPF6) solution in ternary solvent containing trimethyl Phosphate (TMP). High ionic conductivity of 6.2 mS cm−1 at 20 °C was obtained for the gel electrolyte consisting of 0.8 M LiPF6/EC + DEC + TMP (55:25:20) with PVdF-HFP, which is comparable to that of the liquid electrolyte containing the same electrolytic salt. Addition of a small amount of vinylene carbonate (VC) in the gel electrolyte improved the rechargeability of a graphite electrode. The rechargeable capacity of the graphite in the gel containing VC was ca. 300 mAh g−1, which is almost the same as that in a conventional liquid electrolyte system.
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polymeric gel electrolyte containing Alkyl Phosphate for lithium ion batteries
Journal of Power Sources, 2005Co-Authors: Masayuki Morita, Nobuko Yoshimoto, Yoshihiro Niida, Kazuyuki AdachiAbstract:Abstract A nonflammable polymeric gel electrolyte film has been developed for rechargeable lithium battery systems. The gel film consists of poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP) swollen with LiPF 6 solution of a ternary solvent containing nonflammable trimethyl Phosphate (TMP). The addition of TMP to mixed ethylene carbonate plus diethyl carbonate (EC + DEC) solvent prevented the LiPF 6 salt from the thermal decomposition. The LiPF 6 solutions containing 20 vol% or higher content of TMP were fire-retardant. High ionic conductivity was obtained for both the liquid and the gel electrolyte systems containing 55 vol% of TMP in the liquid components: 7.1 × 10 −3 S cm −1 for the liquid and 2.9 × 10 −3 S cm −1 for the gel electrolytes at 20 °C. A wide potential window (−0.5 to 4.5 V versus Li/Li + ) and the redox activity of the electrode materials were established for the gel electrolyte containing TMP.
Kenta Fujii - One of the best experts on this subject based on the ideXlab platform.
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fluorinated Alkyl Phosphate based electrolytes with controlled lithium ion coordination structure
Physical Chemistry Chemical Physics, 2019Co-Authors: Saki Sawayama, Masayuki Morita, Yanko Todorov, Hideyuki Mimura, Kenta FujiiAbstract:Herein, we propose Li-ion solvation-controlled electrolytes based on non-flammable organic solvent TFEP and an LiFSA salt [TFEP: tris(2,2,2-trifluoroethyl)Phosphate, LiFSA: lithium bis(fluorosulfonyl)amide] to allow Li-ion insertion into a graphite electrode for Li-ion batteries. Comprehensive structural study based on (1) infrared (IR)/Raman spectroscopy, (2) high-energy X-ray total scattering (HEXTS), and (3) molecular dynamics (MD) simulation revealed the solvation (or coordination) structures of Li ions in TFEP-based electrolytes at the molecular level. In binary LiFSA/TFEP with a Li salt concentration (cLi) < 1.0 mol dm−3, Li ions are coordinated with both TFEP and FSA components; in detail, two TFEP molecules coordinate in an O-donating monodentate manner and one FSA in an O-donating bidentate manner to form [Li(TFEP)2(bi-FSA)] as the major species. We demonstrated that adding acetonitrile (AN) to the LiFSA/TFEP electrolytes caused structural changes in the Li-ion complexes. The bi-FSA bound to the Li ion changed its coordination mode to mono-FSA, which was induced by solvating AN molecules to Li ions. The redox reaction corresponding to insertion/deinsertion of Li ions into/from the graphite electrode successfully occurred in 1.0 mol dm−3 LiFSA/TFEP with an AN electrolyte system, while there was no or reduced Li-ion insertion in the electrolyte without AN. We discussed the relationship between the structure and electrode reaction of the Li-ion complexes based on the FSA-coordination characteristics; i.e., in LiFSA/TFEP with the AN system, the mono-FSA bound to the Li ion is easier to decoordinate due to weaker Li+⋯mono-FSA− interactions rather than the Li+⋯bi-FSA− interactions, which mainly contribute to charge-transfer at the electrode/electrolyte interface to allow Li-ion insertion/deinsertion in the graphite anode.
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electrochemical properties of a tetrapeg based gel electrolyte containing a nonflammable fluorinated Alkyl Phosphate for safer lithium ion batteries
Chemistry Letters, 2018Co-Authors: Jihae Han, Nobuko Yoshimoto, Masayuki Morita, Mari Yoshitake, Takamasa Sakai, Kenta FujiiAbstract:We report a nonflammable gel electrolyte based on two key soft materials: 1) a homogeneous polymer network prepared from tetra-armed poly(ethylene glycol) (TetraPEG) and 2) a tris(2,2,2-trifluoroethyl)Phosphate (TFEP)-based electrolyte solution. At the equilibrium swelling state, the concentration of the polymer in the TetraPEG gel was relatively low, at only 5.6 wt.%. The TetraPEG gel exhibits a wide electrochemical window of ∼5.0 V and thus works well as an electrolyte for a positive electrode, i.e., a lithium iron Phosphate (LiFePO4).
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role of solvent bulkiness on lithium ion solvation in fluorinated Alkyl Phosphate based electrolytes structural study for designing nonflammable lithium ion batteries
Journal of Physical Chemistry C, 2017Co-Authors: Michiru Sogawa, Nobuko Yoshimoto, Masayuki Morita, Yanko Todorov, Hideyuki Mimura, Daisuke Hirayama, Kenta FujiiAbstract:We report the characteristics of nonflammable tris(2,2,2-trifluoroethyl) Phosphate (TFEP) as a nonaqueous solvent for lithium (Li)-ion battery electrolytes at a molecular level, particularly focusing on the solvent parameters, such as the electron pair-donating ability and molecular bulkiness of TFEP, and the solvation behavior around Li ions. The binding energy for the interactions between a Li ion and several solvents using density functional theory (DFT) calculations indicated that TFEP can be categorized as a nonaqueous solvent with weak electron pair-donating ability, resulting in the prediction of a small Gutmann’s donor number (the DN value is approximately 12.9). The Walden plots based on ionic conductivity and viscosity suggested that Li ions tend to exist as contact ion pairs (Li+···TFSA–) in the TFEP-based solutions, irrespective of the Li salt concentration cLi. Infrared and Raman spectroscopic studies demonstrated that Li ions are solvated by two TFEP molecules and one TFSA anion to form the ...
Nicholas D. Spencer - One of the best experts on this subject based on the ideXlab platform.
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influence of Alkyl chain length on Phosphate self assembled monolayers
Langmuir, 2007Co-Authors: Doris M Spori, Nicholas D. Spencer, Nagaiyanallur V Venkataraman, Samuele Tosatti, Firat Durmaz, Stefan ZurcherAbstract:A series of Alkyl Phosphates with Alkyl chain lengths ranging from C10 to C18 have been synthesized. Self-assembled monolayers (SAMs) of these molecules were prepared on titanium oxide surfaces by immersion of the substrates in Alkyl Phosphate solutions of 0.5 mM concentration in n-heptane/isopropanol. The SAMs were characterized by means of dynamic water contact angle (dCA) measurements, variable-angle spectroscopic ellipsometry (VASE), X-ray photoelectron spectroscopy (XPS), and polarization-modulated infrared reflection−absorption spectroscopy (PM-IRRAS). A higher degree of order and packing density within the monolayers was found for Alkyl Phosphates with Alkyl chain lengths exceeding 15 carbon atoms. This is reflected in a lower dCA hysteresis, as well as a film thickness measured by VASE and XPS close to the expected values for SAMs with an average Alkyl chain tilt angle of 30° to the surface normal. Additionally a shift of the symmetric and antisymmetric C−H stretching modes in the PM-IRRAS spectra...
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selective molecular assembly patterning a new approach to micro and nanochemical patterning of surfaces for biological applications
Langmuir, 2002Co-Authors: Roger Michel, Marcus Textor, Jost W Lussi, Gabor Csucs, Ilya Reviakine, Gaudenz Danuser, Brigitte Ketterer, Jeffrey A Hubbell, Nicholas D. SpencerAbstract:A novel patterning technique based on selective self-assembly of alkane Phosphates on metal oxide surfaces is presented. Standard photolithography was used to create patterns of titanium dioxide within a matrix of silicon dioxide. Alkane Phosphates were found to self-assemble on TiO2, but not on SiO2, surfaces. Subsequent adsorption of poly(l-lysine)-g-poly(ethylene glycol) (PLL-g-PEG) rendered the exposed SiO2 surface resistant to protein adsorption. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry were employed to monitor the assembly processes. Protein-adsorption studies by means of fluorescence microscopy conclusively established that the resulting surfaces displayed protein-adhesive, Alkyl Phosphate modified TiO2 features, arranged within a protein-resistant PLL-g-PEG-modified SiO2 matrix. Human foreskin fibroblasts, incubated in a serum-containing medium, were found to selectively attach to the protein-adhesive areas, where they developed focal contacts. No interac...
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Alkyl Phosphate monolayers self assembled from aqueous solution onto metal oxide surfaces
Langmuir, 2001Co-Authors: Rolf Hofer, Marcus Textor, Nicholas D. SpencerAbstract:Metal oxide surfaces have been coated by self-assembled monolayers (SAMs) of dodecyl Phosphate (DDPO4) and 12-hydroxy dodecyl Phosphate (OH-DDPO4), by means of a novel surface-modification protocol based on the adsorption of the Alkyl Phosphate ammonium salts from aqueous solution. Formation of DDPO4 SAMs has been successfully demonstrated on anodized aluminum (Al2O3) as well as on smooth, thin films of tantalum oxide (Ta2O5), niobium oxide (Nb2O5), zirconium oxide (ZrO2), and titanium oxide (TiO2) deposited on glass substrates, resulting in highly hydrophobic surfaces with advancing water contact angles ≥110°. SAM formation does not occur on silica surfaces under the same conditions. The formation of SAMs based on hydroxy-terminated Alkyl Phosphates (OH-DDPO4) onto Ta2O5 and Nb2O5 has also been observed. DDPO4 and OH-DDPO4 were codeposited onto Ta2O5 from aqueous solutions at different concentration ratios. It is shown that the water contact angle can be precisely controlled within the range of 110−50° b...