Hanaoka, Kenjiro’s team published research in Scientific Reports in 7 | CAS: 459420-09-8

Scientific Reports published new progress about 459420-09-8. 459420-09-8 belongs to pyrimidines, auxiliary class Metabolic Enzyme,3MST, name is 6-Methyl-2-((2-(naphthalen-1-yl)-2-oxoethyl)thio)pyrimidin-4(3H)-one, and the molecular formula is C17H14N2O2S, Safety of 6-Methyl-2-((2-(naphthalen-1-yl)-2-oxoethyl)thio)pyrimidin-4(3H)-one.

Hanaoka, Kenjiro published the artcileDiscovery and Mechanistic Characterization of Selective Inhibitors of H2S-producing Enzyme: 3-Mercaptopyruvate Sulfurtransferase (3MST) Targeting Active-site Cysteine Persulfide, Safety of 6-Methyl-2-((2-(naphthalen-1-yl)-2-oxoethyl)thio)pyrimidin-4(3H)-one, the publication is Scientific Reports (2017), 40227, database is CAplus and MEDLINE.

Very recent studies indicate that sulfur atoms with oxidation state 0 or -1, called sulfane sulfurs, are the actual mediators of some physiol. processes previously considered to be regulated by hydrogen sulfide (H2S). 3-Mercaptopyruvate sulfurtransferase (3MST), one of three H2S-producing enzymes, was also recently shown to produce sulfane sulfur (H2Sn). Here, we report the discovery of several potent 3MST inhibitors by means of high-throughput screening (HTS) of a large chem. library (174,118 compounds) with our H2S-selective fluorescent probe, HSip-1. Most of the identified inhibitors had similar aromatic ring-carbonyl-S-pyrimidone structures. Among them, compound 3 showed very high selectivity for 3MST over other H2S/sulfane sulfur-producing enzymes and rhodanese. The X-ray crystal structures of 3MST complexes with two of the inhibitors revealed that their target is a persulfurated cysteine residue located in the active site of 3MST. Precise theor. calculations indicated the presence of a strong long-range electrostatic interaction between the persulfur anion of the persulfurated cysteine residue and the pos. charged carbonyl carbon of the pyrimidone moiety of the inhibitor. Our results also provide the exptl. support for the idea that the 3MST-catalyzed reaction with 3-mercaptopyruvate proceeds via a ping-pong mechanism.

Scientific Reports published new progress about 459420-09-8. 459420-09-8 belongs to pyrimidines, auxiliary class Metabolic Enzyme,3MST, name is 6-Methyl-2-((2-(naphthalen-1-yl)-2-oxoethyl)thio)pyrimidin-4(3H)-one, and the molecular formula is C17H14N2O2S, Safety of 6-Methyl-2-((2-(naphthalen-1-yl)-2-oxoethyl)thio)pyrimidin-4(3H)-one.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

Elduque, Xavier’s team published research in Bioconjugate Chemistry in 24 | CAS: 186046-81-1

Bioconjugate Chemistry published new progress about 186046-81-1. 186046-81-1 belongs to pyrimidines, auxiliary class Pyrimidine,Carboxylic acid,Amine,Benzene,Amide,Others,PNA,, name is 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(4-(((benzhydryloxy)carbonyl)amino)-2-oxopyrimidin-1(2H)-yl)acetamido)acetic acid, and the molecular formula is C39H35N5O8, Recommanded Product: 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(4-(((benzhydryloxy)carbonyl)amino)-2-oxopyrimidin-1(2H)-yl)acetamido)acetic acid.

Elduque, Xavier published the artcileProtected Maleimide Building Blocks for the Decoration of Peptides, Peptoids, and Peptide Nucleic Acids, Recommanded Product: 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(4-(((benzhydryloxy)carbonyl)amino)-2-oxopyrimidin-1(2H)-yl)acetamido)acetic acid, the publication is Bioconjugate Chemistry (2013), 24(5), 832-839, database is CAplus and MEDLINE.

Monomers allowing for the introduction of [2,5-dimethylfuran]-protected maleimides into polyamides such as peptides, peptide nucleic acids, and peptoids were prepared, as well as the corresponding oligomers. Suitable maleimide deprotection conditions were established in each case. The stability of the adducts generated by Michael-type maleimide-thiol reaction and Diels-Alder cycloaddition to maleimide deprotection conditions was exploited to prepare a variety of conjugates from peptide and PNA scaffolds incorporating one free and one protected maleimide. The target mols. were synthesized by using two subsequent maleimide-involving click reactions separated by a maleimide deprotection step. Carrying out maleimide deprotection and conjugation simultaneously gave better results than performing the two reactions subsequently.

Bioconjugate Chemistry published new progress about 186046-81-1. 186046-81-1 belongs to pyrimidines, auxiliary class Pyrimidine,Carboxylic acid,Amine,Benzene,Amide,Others,PNA,, name is 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(4-(((benzhydryloxy)carbonyl)amino)-2-oxopyrimidin-1(2H)-yl)acetamido)acetic acid, and the molecular formula is C39H35N5O8, Recommanded Product: 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(4-(((benzhydryloxy)carbonyl)amino)-2-oxopyrimidin-1(2H)-yl)acetamido)acetic acid.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

Elduque, Xavier’s team published research in Bioconjugate Chemistry in 24 | CAS: 169396-92-3

Bioconjugate Chemistry published new progress about 169396-92-3. 169396-92-3 belongs to pyrimidines, auxiliary class Pyrimidine,Carboxylic acid,Amine,Amide,Others,PNA, name is 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamido)acetic acid, and the molecular formula is C26H26N4O7, Application of 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamido)acetic acid.

Elduque, Xavier published the artcileProtected Maleimide Building Blocks for the Decoration of Peptides, Peptoids, and Peptide Nucleic Acids, Application of 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamido)acetic acid, the publication is Bioconjugate Chemistry (2013), 24(5), 832-839, database is CAplus and MEDLINE.

Monomers allowing for the introduction of [2,5-dimethylfuran]-protected maleimides into polyamides such as peptides, peptide nucleic acids, and peptoids were prepared, as well as the corresponding oligomers. Suitable maleimide deprotection conditions were established in each case. The stability of the adducts generated by Michael-type maleimide-thiol reaction and Diels-Alder cycloaddition to maleimide deprotection conditions was exploited to prepare a variety of conjugates from peptide and PNA scaffolds incorporating one free and one protected maleimide. The target mols. were synthesized by using two subsequent maleimide-involving click reactions separated by a maleimide deprotection step. Carrying out maleimide deprotection and conjugation simultaneously gave better results than performing the two reactions subsequently.

Bioconjugate Chemistry published new progress about 169396-92-3. 169396-92-3 belongs to pyrimidines, auxiliary class Pyrimidine,Carboxylic acid,Amine,Amide,Others,PNA, name is 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamido)acetic acid, and the molecular formula is C26H26N4O7, Application of 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamido)acetic acid.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

Zheltovsky, N. V.’s team published research in Biopolimery i Kletka in 10 | CAS: 608-34-4

Biopolimery i Kletka published new progress about 608-34-4. 608-34-4 belongs to pyrimidines, auxiliary class Pyrimidine,Amide, name is 3-Methylpyrimidine-2,4(1H,3H)-dione, and the molecular formula is C2H3N3, Synthetic Route of 608-34-4.

Zheltovsky, N. V. published the artcileInteractions of methyl and glycosyl derivatives of pyrimidine nucleotide bases with amino acid carboxylic group, Synthetic Route of 608-34-4, the publication is Biopolimery i Kletka (1994), 10(6), 45-51, database is CAplus.

By UV, IR, and NMR interactions of a number of Me and glycosyl derivatives of pyrimidine bases with amino acid carboxylic group in DMSO were studied as a model of probable point contacts in real nucleoprotein complexes. It was found that like the unsubstituted base 1-methylcytosine, 5-methylcytosine, 1,5-dimethylcytosine, cytidine, deoxycytidine, 5-methyldeoxycytidine form complexes with a neutral carboxylic group, and 3-methylcytosine and isocytosine interact with deprotonated carboxylic group (carboxylate ion). Like free thymine and uracil, their derivatives 1-methylthymine, 1-methyluracil, 3-methyluracil, thymidine, uridine, 5-methyluridine, deoxyuridine interact only with carboxylate ion. Anal. of the results obtained and the data of previous works points out the ability of amino acid carboxylic group to differentiate between cytosine and thymine (uracil), and between their nucleosides and derivatives as well.

Biopolimery i Kletka published new progress about 608-34-4. 608-34-4 belongs to pyrimidines, auxiliary class Pyrimidine,Amide, name is 3-Methylpyrimidine-2,4(1H,3H)-dione, and the molecular formula is C2H3N3, Synthetic Route of 608-34-4.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

Beesu, Mallesh’s team published research in Journal of Medicinal Chemistry in 59 | CAS: 56-05-3

Journal of Medicinal Chemistry published new progress about 56-05-3. 56-05-3 belongs to pyrimidines, auxiliary class Pyrimidine,Chloride,Amine,API, name is 2-Amino-4,6-dichloropyrimidine, and the molecular formula is C4H3Cl2N3, Application In Synthesis of 56-05-3.

Beesu, Mallesh published the artcileHuman Toll-like Receptor (TLR) 8-Specific Agonistic Activity in Substituted Pyrimidine-2,4-diamines, Application In Synthesis of 56-05-3, the publication is Journal of Medicinal Chemistry (2016), 59(17), 8082-8093, database is CAplus and MEDLINE.

Activation of human toll-like receptor-8 (TLR8) evokes a distinct cytokine profile favoring the generation of Type 1 helper T cells. A multiplexed high-throughput screen had led to the identification of N4-butyl-5-iodo-6-methylpyrimidine-2,4-diamine as a pure TLR8 agonist, and a detailed SAR study of this chemotype was undertaken. A Bu substituent at N4 was optimal, and replacement of the 5-iodo group with chloro, bromo, or fluoro groups led to losses in potency, as did the introduction of aromatic bulk. Drawing from the previous structure-based design, several 5-alkylamino derivatives were evaluated. Significant enhancement of potency was achieved in 5-(4-aminobutyl)-N4-butyl-6-methylpyrimidine-2,4-diamine. This compound potently induced Th1-biasing IFN-γ and IL-12 in human blood, but lower levels of the proinflammatory cytokines IL-1β, IL-6 and IL-8. These results suggest that the inflammatory and reactogenic propensities of this compound could be considerably more favorable than other TLR8 agonists under evaluation.

Journal of Medicinal Chemistry published new progress about 56-05-3. 56-05-3 belongs to pyrimidines, auxiliary class Pyrimidine,Chloride,Amine,API, name is 2-Amino-4,6-dichloropyrimidine, and the molecular formula is C4H3Cl2N3, Application In Synthesis of 56-05-3.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

Siddiraju, S.’s team published research in Annales Pharmaceutiques Francaises in 73 | CAS: 74638-76-9

Annales Pharmaceutiques Francaises published new progress about 74638-76-9. 74638-76-9 belongs to pyrimidines, auxiliary class Pyrimidine, name is 2,4-Diaminopyrimidine-3-oxide, and the molecular formula is C7H7IN2O, Application of 2,4-Diaminopyrimidine-3-oxide.

Siddiraju, S. published the artcileStability indicating RP-HPLC method development and validation for the simultaneous determination of aminexil and minoxidil in pharmaceutical dosage form, Application of 2,4-Diaminopyrimidine-3-oxide, the publication is Annales Pharmaceutiques Francaises (2015), 73(2), 114-122, database is CAplus and MEDLINE.

The objective of the present work is to develop stability indicating high-performance liquid chromatog. method for the simultaneous determination of aminexil and minoxidil in pharmaceutical dosage form. The chromatog. separation was achieved with BDS Hypersil C18 column (250 mm × 4.6 mm × 5 μ) as stationary phase and phosphate buffer and acetonitrile (78:22) as mobile phase. The method was employed by using a flow rate of 1.1 mL/min kept at 30 °C. The detection wavelength was kept at 238 nm by using photo-diode array detector. The retention times of the aminexil and minoxidil were found to be 2.3 min and 3.9 min, resp. The method developed was validated in accordance with ICH guidelines with respect to the stability indicating capacity of the method including system suitability, accuracy, precision, linearity, range, limit of detection, limit of quantification and robustness. The linearity responses of aminexil and minoxidil were found to be in the concentration ranges of 18.75-112.5 μg/mL and 25-150 μg/mL, resp. The LOD and LOQ values for aminexil were found to be 0.31 and 0.92 μg/mL and minoxidil were found to be 0.03 and 0.10 μg/mL resp. The percentage recoveries for both the drugs were found in the range of 98-101%. This method is accurate, precise and sensitive; hence, it can be employed for routine quality control of aminexil and minoxidil in pharmaceutical industries and drug testing laboratories

Annales Pharmaceutiques Francaises published new progress about 74638-76-9. 74638-76-9 belongs to pyrimidines, auxiliary class Pyrimidine, name is 2,4-Diaminopyrimidine-3-oxide, and the molecular formula is C7H7IN2O, Application of 2,4-Diaminopyrimidine-3-oxide.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

Mannisto, Jere K.’s team published research in Chemistry – A European Journal in 25 | CAS: 944401-58-5

Chemistry – A European Journal published new progress about 944401-58-5. 944401-58-5 belongs to pyrimidines, auxiliary class Trifluoromethyl,Pyrimidine,Fluoride,Boronic acid and ester,Amine,Boronate Esters,Boronic acid and ester,, name is 5-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-4-(trifluoromethyl)pyrimidin-2-amine, and the molecular formula is C11H15BF3N3O2, SDS of cas: 944401-58-5.

Mannisto, Jere K. published the artcileOne-Step Synthesis of 3,4-Disubstituted 2-Oxazolidinones by Base-Catalyzed CO2 Fixation and Aza-Michael Addition, SDS of cas: 944401-58-5, the publication is Chemistry – A European Journal (2019), 25(44), 10284-10289, database is CAplus and MEDLINE.

A new, single-step approach to 3,4-disubstituted 2-oxazolidinones by aza-Michael addition using CO2 as a carbonyl source and 1,1,3,3-tetramethylguanidine (TMG) as a catalyst was reported. The modular reaction, which occurred between a γ-brominated Michael acceptor, CO2 and an arylamine, aliphatic amine or phenylhydrazine was performed under mild conditions. The regiospecific reaction displayed good yields (average 75 %) and excellent functional-group compatibility. In addition, late-stage functionalization of drug and drug-like mols. wais demonstrated. The exptl. results suggested a mechanism consisting of several elementary steps: TMG-assisted carboxylation of aniline; generation of an O-alkyl carbamate; and the final ring-forming step through an intramol. aza-Michael addition

Chemistry – A European Journal published new progress about 944401-58-5. 944401-58-5 belongs to pyrimidines, auxiliary class Trifluoromethyl,Pyrimidine,Fluoride,Boronic acid and ester,Amine,Boronate Esters,Boronic acid and ester,, name is 5-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-4-(trifluoromethyl)pyrimidin-2-amine, and the molecular formula is C11H15BF3N3O2, SDS of cas: 944401-58-5.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

James, Carrie R.’s team published research in Journal of the American Chemical Society in 136 | CAS: 186046-81-1

Journal of the American Chemical Society published new progress about 186046-81-1. 186046-81-1 belongs to pyrimidines, auxiliary class Pyrimidine,Carboxylic acid,Amine,Benzene,Amide,Others,PNA,, name is 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(4-(((benzhydryloxy)carbonyl)amino)-2-oxopyrimidin-1(2H)-yl)acetamido)acetic acid, and the molecular formula is C39H35N5O8, COA of Formula: C39H35N5O8.

James, Carrie R. published the artcilePoly(oligonucleotide), COA of Formula: C39H35N5O8, the publication is Journal of the American Chemical Society (2014), 136(32), 11216-11219, database is CAplus and MEDLINE.

Here we report the preparation of poly(oligonucleotide) brush polymers and amphiphilic brush copolymers from nucleic acid monomers via graft-through polymerization We describe the polymerization of PNA-norbornyl monomers to yield poly-PNA (poly(peptide nucleic acid)) via ring-opening metathesis polymerization (ROMP) with the initiator, (IMesH2)(C5H5N)2(Cl)2RuCHPh. In addition, we present the preparation of poly-PNA nanoparticles from amphiphilic block copolymers and describe their hybridization to a complementary single-stranded DNA (ssDNA) oligonucleotide.

Journal of the American Chemical Society published new progress about 186046-81-1. 186046-81-1 belongs to pyrimidines, auxiliary class Pyrimidine,Carboxylic acid,Amine,Benzene,Amide,Others,PNA,, name is 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(4-(((benzhydryloxy)carbonyl)amino)-2-oxopyrimidin-1(2H)-yl)acetamido)acetic acid, and the molecular formula is C39H35N5O8, COA of Formula: C39H35N5O8.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

James, Carrie R.’s team published research in Journal of the American Chemical Society in 136 | CAS: 169396-92-3

Journal of the American Chemical Society published new progress about 169396-92-3. 169396-92-3 belongs to pyrimidines, auxiliary class Pyrimidine,Carboxylic acid,Amine,Amide,Others,PNA, name is 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamido)acetic acid, and the molecular formula is C26H26N4O7, Related Products of pyrimidines.

James, Carrie R. published the artcilePoly(oligonucleotide), Related Products of pyrimidines, the publication is Journal of the American Chemical Society (2014), 136(32), 11216-11219, database is CAplus and MEDLINE.

Here we report the preparation of poly(oligonucleotide) brush polymers and amphiphilic brush copolymers from nucleic acid monomers via graft-through polymerization We describe the polymerization of PNA-norbornyl monomers to yield poly-PNA (poly(peptide nucleic acid)) via ring-opening metathesis polymerization (ROMP) with the initiator, (IMesH2)(C5H5N)2(Cl)2RuCHPh. In addition, we present the preparation of poly-PNA nanoparticles from amphiphilic block copolymers and describe their hybridization to a complementary single-stranded DNA (ssDNA) oligonucleotide.

Journal of the American Chemical Society published new progress about 169396-92-3. 169396-92-3 belongs to pyrimidines, auxiliary class Pyrimidine,Carboxylic acid,Amine,Amide,Others,PNA, name is 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamido)acetic acid, and the molecular formula is C26H26N4O7, Related Products of pyrimidines.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

Pinto, Brunella’s team published research in Biochimica et Biophysica Acta, General Subjects in 1861 | CAS: 169396-92-3

Biochimica et Biophysica Acta, General Subjects published new progress about 169396-92-3. 169396-92-3 belongs to pyrimidines, auxiliary class Pyrimidine,Carboxylic acid,Amine,Amide,Others,PNA, name is 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamido)acetic acid, and the molecular formula is C26H26N4O7, HPLC of Formula: 169396-92-3.

Pinto, Brunella published the artcileSynthesis and label free characterization of a bimolecular PNA homo quadruplex, HPLC of Formula: 169396-92-3, the publication is Biochimica et Biophysica Acta, General Subjects (2017), 1861(5_Part_B), 1222-1228, database is CAplus and MEDLINE.

G-quadruplex DNA is involved in many physiol. and pathol. processes. Both clin. and exptl. studies on DNA G-quadruplexes are slowed down by their enzymic instability. In this frame, more stable chem. modified analogs are needed. The bis-end-linked-(gggt)2 PNA mol. (BEL-PNA) was synthesized using in solution and solid phase synthetic approaches. Quadruplex formation was assessed by CD (CD) and surface enhanced Raman scattering (SERS). An unprecedented bimol. PNA homo quadruplex is here reported. To achieve this goal, we developed a bifunctional linker that once functionalized with gggt PNA strands and annealed in K+ buffer allowed the obtainment of a PNA homo quadruplex. 4The identification of the strong SERS band at âˆ?1481 cm 1, attributable to vibrations involving the quadruplex diagnostic Hoogsteen type hydrogen bonds, confirmed the formation of the PNA homo quadruplex. By tethering two G-rich PNA strands to the two ends of a suitable bifunctional linker it is possible to obtain bimol. PNA homo quadruplexes after annealing in K+-containing buffers. The formation of such CD-unfriendly complexes can be monitored, even at low concentrations, by using the SERS technique. Given the importance of DNA G-quadruplexes in medicine and nanotechnol., the obtainment of G-quadruplex analogs provided with enhanced enzymic stability, and their monitoring by highly sensitive label-free techniques are of the highest importance. This article is part of a Special Issue entitled “G-quadruplex” – guest edited by Dr. Concetta Giancola and Dr. Daniela Montesarchio.

Biochimica et Biophysica Acta, General Subjects published new progress about 169396-92-3. 169396-92-3 belongs to pyrimidines, auxiliary class Pyrimidine,Carboxylic acid,Amine,Amide,Others,PNA, name is 2-(N-(2-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-2-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamido)acetic acid, and the molecular formula is C26H26N4O7, HPLC of Formula: 169396-92-3.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia