The taming of cyclobutadiene was accomplished in the interior hemicarcerand 1. Cyclobutadiene is a stable compound with singlet ground state when it synthesized In order to synthesize incarcerated and characterize its structure, one bimolecular, three photochemical, two thermal reactions were carried out authors consider both realistic useful regard internal phase carcerands hemicarcerands as new matter.

Des widerspenstigen Cyclobutadiens Zähmung gelang im Innern des Hemicarceranden 1 . Cyclobutadien ist eine stabile Verbindung mit einem Singulett‐Grundzustand, wenn es von synthetisiert wird. Zur Synthese und Strukturbestimmung eingekapselten wurden drei photochemische, zwei thermische bimolekulare Reaktion herangezogen. Die Autoren halten für realistisch nützlich, die innere Phase Carceranden als einen neuen Zustand der Materie zu betrachten. magnified image

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHost-guest complexation. 58. Guest release and capture by hemicarcerands introduces the phenomenon of constrictive bindingDonald J. Cram, Martin E. Tanner, Carolyn B. KnoblerCite this: Am. Chem. Soc. 1991, 113, 20, 7717–7727Publication Date (Print):September 1, 1991Publication History Published online1 May 2002Published inissue 1 September 1991https://pubs.acs.org/doi/10.1021/ja00020a039https://doi.org/10.1021/ja00020a039research-articleACS...

Norcoclaurine synthase catalyzes an asymmetric Pictet−Spengler condensation of dopamine and 4-hydroxyphenylacetaldehyde to give (S)-norcoclaurine. This is the first committed step in biosynthesis benzylisoquinoline alkaloids that include morphine codeine. In this work, gene encoding for Thalictrum flavum norcoclaurine highly overexpressed Escherichia coli resulting His-tagged recombinant enzyme purified time. A continuous assay based on circular dichroism spectroscopy developed used monitor...

Teleocidin B is an indole terpenoid isolated from Streptomyces. Due to its unique chemical structure and ability activate protein kinase C, it has attracted interest in the areas of organic chemistry cell biology. Here, we report identification genes encoding enzymes for teleocidin biosynthesis, including nonribosomal peptide synthetase (tleA), P-450 monooxygenase (tleB), prenyltransferase (tleC), methyltransferase (tleD). The tleD gene, which located outside tleABC cluster on chromosome,...

Bacterial UDP-N-acetylglucosamine 2-epimerase catalyzes the reversible epimerization at C-2 of (UDP-GlcNAc) and thereby provides bacteria with UDP-N-acetylmannosamine (UDP-ManNAc), activated donor ManNAc residues. is critical for several processes in bacteria, including formation antiphagocytic capsular polysaccharide pathogens such as Streptococcus pneumoniae types 19F 19A. We have determined X-ray structure (2.5 A) UDP-GlcNAc bound UDP identified a previously unsuspected structural...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIsotope effects and the identification of catalytic residues in reaction catalyzed by glutamate racemaseMartin E. Tanner, Kathleen A. Gallo, Jeremy R. KnowlesCite this: Biochemistry 1993, 32, 15, 3998–4006Publication Date (Print):April 20, 1993Publication History Published online1 May 2002Published inissue 20 April 1993https://pubs.acs.org/doi/10.1021/bi00066a021https://doi.org/10.1021/bi00066a021research-articleACS PublicationsRequest reuse...

We report the synthesis and initial evaluation of first effective inhibitors D-glutamic acid-adding enzyme (UDP-N-acetylmuramoyl-L-alanine:D-glutamate ligase or MurD). This plays a key role in bacterial peptidoglycan biosynthesis is therefore target for antibiotic design. Phosphinic acid 3 dipeptide analog linked to uridine diphosphate by hydrophobic spacer. It good inhibitor (IC(50) = 0.68 &mgr;M) as it closely resembles tetrahedral intermediate that presumed form ligation reaction....

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMechanism of the reaction catalyzed by glutamate racemaseKathleen A. Gallo, Martin E. Tanner, and Jeremy R. KnowlesCite this: Biochemistry 1993, 32, 15, 3991–3997Publication Date (Print):April 20, 1993Publication History Published online1 May 2002Published inissue 20 April 1993https://doi.org/10.1021/bi00066a020Request reuse permissionsArticle Views492Altmetric-Citations76LEARN ABOUT THESE METRICSArticle Views are COUNTER-compliant sum full text...

The enzyme dimethylallyltryptophan synthase catalyzes the "normal" prenylation of Trp at C-4 in first step ergot alkaloid biosynthesis. Lys174Ala mutant is found to produce a hexahydropyrroloindole that "reverse-prenylated" C-3 as its major product. This interpreted evidence support mechanism involves an initial "reverse-prenylation" C-3, followed by Cope rearrangement and rearomatization.

Glutamate racemase, MurI, catalyzes the interconversion of glutamate enantiomers in a cofactor-independent fashion and provides bacteria with source d-Glu for use peptidoglycan biosynthesis. The enzyme uses "two-base" mechanism involving deprotonation substrate at α-position to form an anionic intermediate, followed by reprotonation opposite stereochemical sense. In Lactobacillus fermenti enzyme, Cys73 is responsible d-glutamate, Cys184 l-glutamate; however, very little known about roles...

Bacterial UDP-glucose dehydrogenase (UDPGlcDH) is essential for formation of the antiphagocytic capsule that protects many virulent bacteria such as Streptococcus pyogenes and pneumoniae type 3 from host's immune system. We have determined X-ray structures both native Cys260Ser UDPGlcDH S. (74% similarity to pneumoniae) in ternary complexes with UDP-xylose/NAD+ UDP-glucuronic acid/NAD(H), respectively. The 402 residue homodimeric composed an N-terminal NAD+ dinucleotide binding domain a...

Dimethylallyltryptophan synthase is an aromatic prenyltransferase that catalyzes electrophilic substitution reaction between dimethylallyl diphosphate (DMAPP) and l-tryptophan. The found in a variety of fungi, where it the first committed step biosynthesis ergot alkaloids. enzymatic could follow either dissociative mechanism involving discrete cation intermediate or associative which indole ring directly displaces single step. In this work, positional isotope exchange (PIX) experiments are...

Catch a tiger by the tail: We have demonstrated that feeding nonmotile mutant C. jejuni bacteria with neutral azide-labelled pseudaminic acid precursor we can restore their ability to generate functional flagella. The presence of azido-pseudaminic on surface flagella provides bio-orthogonal chemical handle be used modify flagellar proteins.

Legionaminic acid is a nine-carbon α-keto that similar in structure to other members of the sialic family includes neuraminic and pseudaminic acid. It found as component lipopolysaccharide several bacterial species perhaps best known for its presence O-antigen causative agent Legionnaires' disease, Legionella pneumophila. In this work, enzymes responsible biosynthesis activation N,N′-diacetyllegionaminic are identified first time. A cluster three L. pneumophila genes bearing homology...

Glutamate racemase is a cofactor-independent enzyme that employs two active-site cysteine residues as acid/base catalysts during the interconversion of glutamate enantiomers. In given reaction direction, thiolate from one cysteines abstracts α-proton, and other thiol delivers proton to opposite face resulting carbanionic intermediate. This paper reports C73S C184S mutants are still capable racemizing with specificity constants about 103-fold lower than those wild-type enzyme. A "one-base...

In Neisseria meningitidis and related bacterial pathogens, sialic acids play critical roles in mammalian cell immunity evasion are synthesized by a conserved enzymatic pathway that includes acid synthase (NeuB, SiaC, or SynC). NeuB catalyzes the condensation of phosphoenolpyruvate (PEP) N-acetylmannosamine, directly forming N-acetylneuraminic (or acid). this paper we report development coupled assay to monitor reaction kinetics an 18O-labeling study demonstrates operates via C-O bond...

Campylobacter jejuni and coli are the main causes of bacterial diarrhea worldwide, Helicobacter pylori is known to cause duodenal ulcers. In all these pathogenic organisms, flagellin proteins heavily glycosylated with a 2-keto-3-deoxy acid, pseudaminic acid (5,7-diacetamido-3,5,7,9-tetradeoxy-L-glycero-L-manno-nonulosonic acid). The presence required for proper development flagella thereby necessary motility in, invasion of, host. this study we report first characterization NeuB3 from C. as...

UDP-glucuronic acid is used by many pathogenic bacteria in the construction of an antiphagocytic capsule that required for virulence. The enzyme UDP-glucose dehydrogenase catalyzes NAD+-dependent 2-fold oxidation and provides a source acid. In present study recombinant from group A streptococci has been purified found to be active as monomer. contains no chromophoric cofactors, its activity unaffected presence EDTA or carbonyl-trapping reagents. Initial velocity product inhibition kinetic...