The Experts below are selected from a list of 171699 Experts worldwide ranked by ideXlab platform
Anthony A. Sauve - One of the best experts on this subject based on the ideXlab platform.
-
synthesis of β nicotinamide riboside using an efficient two Step Methodology
Current protocols in human genetics, 2017Co-Authors: Ning Zhang, Anthony A. SauveAbstract:A two-Step chemical method for the synthesis of β-nicotinamide riboside (NR) is described. NR has achieved wide use as an NAD+ precursor (vitamin B3) and can significantly increase central metabolite NAD+ concentrations in mammalian cells. β-NR can be prepared with an efficient two-Step procedure. The synthesis is initiated via coupling of commercially available 1,2,3,5-tetra-O-acetyl-β-D-ribofuranose with ethyl nicotinate in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf). 1 H NMR showed that the product was formed with complete stereoselectivity to produce only the β-isomer in high yield (>90% versus starting sugar). The clean stereochemical result suggests that the coupling proceeds via a cationic cis-1,2-acyloxonium-sugar intermediate, which controls addition by nucleophiles to generate predominantly β-stereochemistry. The subsequent deprotection of esters in methanolic ammonia generates the desired product in 85% overall yield versus sugar. © 2017 by John Wiley & Sons, Inc.
-
Syntheses of nicotinamide riboside and derivatives: effective agents for increasing nicotinamide adenine dinucleotide concentrations in mammalian cells.
Journal of medicinal chemistry, 2007Co-Authors: Tianle Yang, Noel Yan-ki Chan, Anthony A. SauveAbstract:A new two-Step Methodology achieves stereoselective synthesis of β-nicotinamide riboside and a series of related amide, ester, and acid nucleosides. Compounds were prepared through a triacetylated-nicotinate ester nucleoside, via coupling of either ethylnicotinate or phenylnicotinate with 1,2,3,5-tetra-O-acetyl-β-d-ribofuranose. Nicotinamide riboside, nicotinic acid riboside, O-ethylnicotinate riboside, O-methylnicotinate riboside, and several N-alkyl derivatives increased NAD+ concentrations from 1.2–2.7-fold in several mammalian cell lines. These findings establish bioavailability and potent effects of these nucleosides in stimulating the increase of NAD+ concentrations in mammalian cells.
Julian Ihssen - One of the best experts on this subject based on the ideXlab platform.
-
tempo oxidized nanofibrillated cellulose as a high density carrier for bioactive molecules
Biomacromolecules, 2015Co-Authors: Ramon Weishaupt, Gilberto Siqueira, Mark Schubert, Philippe Tingaut, Katharina Maniuraweber, Tanja Zimmermann, Linda Thonymeyer, Greta Faccio, Julian IhssenAbstract:Controlled and efficient immobilization of specific biomolecules is a key technology to introduce new, favorable functions to materials suitable for biomedical applications. Here, we describe an innovative and efficient, two-Step Methodology for the stable immobilization of various biomolecules, including small peptides and enzymes onto TEMPO oxidized nanofibrillated cellulose (TO-NFC). The introduction of carboxylate groups to NFC by TEMPO oxidation provided a high surface density of negative charges able to drive the adsorption of biomolecules and take part in covalent cross-linking reactions with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDAC) and glutaraldehyde (Ga) chemistry. Up to 0.27 μmol of different biomolecules per mg of TO-NFC could be reversibly immobilized by electrostatic interaction. An additional chemical cross-linking Step prevented desorption of more than 80% of these molecules. Using the cysteine-protease papain as model, a highly active papain-TO-NFC conjugate was achieved. Onc...
-
tempo oxidized nanofibrillated cellulose as a high density carrier for bioactive molecules
Biomacromolecules, 2015Co-Authors: Ramon Weishaupt, Gilberto Siqueira, Mark Schubert, Philippe Tingaut, Katharina Maniuraweber, Tanja Zimmermann, Linda Thonymeyer, Greta Faccio, Julian IhssenAbstract:Controlled and efficient immobilization of specific biomolecules is a key technology to introduce new, favorable functions to materials suitable for biomedical applications. Here, we describe an innovative and efficient, two-Step Methodology for the stable immobilization of various biomolecules, including small peptides and enzymes onto TEMPO oxidized nanofibrillated cellulose (TO-NFC). The introduction of carboxylate groups to NFC by TEMPO oxidation provided a high surface density of negative charges able to drive the adsorption of biomolecules and take part in covalent cross-linking reactions with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDAC) and glutaraldehyde (Ga) chemistry. Up to 0.27 μmol of different biomolecules per mg of TO-NFC could be reversibly immobilized by electrostatic interaction. An additional chemical cross-linking Step prevented desorption of more than 80% of these molecules. Using the cysteine-protease papain as model, a highly active papain-TO-NFC conjugate was achieved. Onc...
Kiyoshi Tomioka - One of the best experts on this subject based on the ideXlab platform.
-
facile asymmetric synthesis of α amino acids employing chiral ligand mediated asymmetric addition reactions of phenyllithium with imines
ChemInform, 2001Co-Authors: Masayoshi Hasegawa, Daisuke Taniyama, Kiyoshi TomiokaAbstract:Abstract A three-Step Methodology involving an external chiral ligand-mediated asymmetric addition of phenyllithium to an anisidine imine, oxidative removal of N-PMP group, and finally oxidative conversion of the phenyl group to a carboxyl group provides a facile synthesis of optically pure α-amino acid derivatives bearing a bulky α-substituent.
-
a facile asymmetric synthesis of 1 substituted tetrahydroisoquinoline based on a chiral ligand mediated addition of organolithium to imine
Tetrahedron-asymmetry, 1999Co-Authors: Daisuke Taniyama, Masayoshi Hasegawa, Kiyoshi TomiokaAbstract:Abstract A two-Step Methodology involving an asymmetric addition of organolithium to an imine and subsequent Moffat oxidation as the key Steps provided a new synthetic way to the optically and biologically active 1-substituted tetrahydroisoquinolines.
Ramon Weishaupt - One of the best experts on this subject based on the ideXlab platform.
-
tempo oxidized nanofibrillated cellulose as a high density carrier for bioactive molecules
Biomacromolecules, 2015Co-Authors: Ramon Weishaupt, Gilberto Siqueira, Mark Schubert, Philippe Tingaut, Katharina Maniuraweber, Tanja Zimmermann, Linda Thonymeyer, Greta Faccio, Julian IhssenAbstract:Controlled and efficient immobilization of specific biomolecules is a key technology to introduce new, favorable functions to materials suitable for biomedical applications. Here, we describe an innovative and efficient, two-Step Methodology for the stable immobilization of various biomolecules, including small peptides and enzymes onto TEMPO oxidized nanofibrillated cellulose (TO-NFC). The introduction of carboxylate groups to NFC by TEMPO oxidation provided a high surface density of negative charges able to drive the adsorption of biomolecules and take part in covalent cross-linking reactions with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDAC) and glutaraldehyde (Ga) chemistry. Up to 0.27 μmol of different biomolecules per mg of TO-NFC could be reversibly immobilized by electrostatic interaction. An additional chemical cross-linking Step prevented desorption of more than 80% of these molecules. Using the cysteine-protease papain as model, a highly active papain-TO-NFC conjugate was achieved. Onc...
-
tempo oxidized nanofibrillated cellulose as a high density carrier for bioactive molecules
Biomacromolecules, 2015Co-Authors: Ramon Weishaupt, Gilberto Siqueira, Mark Schubert, Philippe Tingaut, Katharina Maniuraweber, Tanja Zimmermann, Linda Thonymeyer, Greta Faccio, Julian IhssenAbstract:Controlled and efficient immobilization of specific biomolecules is a key technology to introduce new, favorable functions to materials suitable for biomedical applications. Here, we describe an innovative and efficient, two-Step Methodology for the stable immobilization of various biomolecules, including small peptides and enzymes onto TEMPO oxidized nanofibrillated cellulose (TO-NFC). The introduction of carboxylate groups to NFC by TEMPO oxidation provided a high surface density of negative charges able to drive the adsorption of biomolecules and take part in covalent cross-linking reactions with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDAC) and glutaraldehyde (Ga) chemistry. Up to 0.27 μmol of different biomolecules per mg of TO-NFC could be reversibly immobilized by electrostatic interaction. An additional chemical cross-linking Step prevented desorption of more than 80% of these molecules. Using the cysteine-protease papain as model, a highly active papain-TO-NFC conjugate was achieved. Onc...
Rui L Reis - One of the best experts on this subject based on the ideXlab platform.
-
design of nano and microfiber combined scaffolds by electrospinning of collagen onto starch based fiber meshes a man made equivalent of natural extracellular matrix
Tissue Engineering Part A, 2011Co-Authors: Kadriye Tuzlakoglu, Marina I Santos, Nuno M Neves, Rui L ReisAbstract:Mimicking the structural organization and biologic function of natural extracellular matrix has been one of the main goals of tissue engineering. Nevertheless, the majority of scaffolding materials for bone regeneration highlights biochemical functionality in detriment of mechanical properties. In this work we present a rather innovative construct that combines in the same structure electrospun type I collagen nanofibers with starch-based microfibers. These combined structures were obtained by a two-Step Methodology and structurally consist in a type I collagen nano-network incorporated on a macro starch-based support. The morphology of the developed structures was assessed by several microscopy techniques and the collagenous nature of the nano-network was confirmed by immunohistochemistry. In addition, and especially regarding the requirements of large bone defects, we also successfully introduced the concept of layer by layer, as a way to produce thicker structures. In an attempt to recreate bone microe...
-
nano and micro fiber combined scaffolds a new architecture for bone tissue engineering
Journal of Materials Science: Materials in Medicine, 2005Co-Authors: Kadriye Tuzlakoglu, Nimet Bolgen, Antonio J Salgado, Manuela E Gomes, Erhan Piskin, Rui L ReisAbstract:One possible interesting way of designing a scaffold for bone tissue engineering is to base it on trying to mimic the biophysical structure of natural extracellular matrix (ECM). This work was developed in order to produce scaffolds for supporting bone cells. Nano and micro fiber combined scaffolds were originally produced from starch based biomaterials by means of a fiber bonding and a electrospinning, two Step Methodology. The cell culture studies with SaOs-2 human osteoblast-like cell line and rat bone marrow stromal cells demonstrated that presence of nanofibers influenced cell shape and cytoskeletal organization of the cells on the nano/micro combined scaffolds. Moreover, cell viability and Alkaline Phosphatase (ALP) activity for both cell types was found to be higher in nano/micro combined scaffolds than in control scaffolds based on fiber meshes without nanofibers.
