scholarly journals Isolation of mycobactins from various mycobacteria. The properties of mycobactins S and H

1969 ◽  
Vol 111 (5) ◽  
pp. 785-792 ◽  
Author(s):  
A. J. White ◽  
G. A. Snow
Keyword(s):  
Mycobacterium Smegmatis ◽  
Chemical Structure ◽  
Methyl Groups ◽  
Acid Moiety ◽  
Extraction And Purification ◽  
Acid Fragment ◽  
Previous Assignment ◽  
Optical Configuration ◽  
Synthetic Media ◽  
Mycobactin S

Mycobactin S has been isolated from Mycobacterium smegmatis and from Mycobacterium sp. Olitzky & Gershon, strain 2, and mycobactin H from M. thermoresistible; all three organisms were grown on synthetic media of low iron content. These two mycobactins are mixtures of compounds having the same nucleus but differing in their fatty side chains. The nucleus of mycobactin S has a chemical structure identical with that of mycobactin T but differs in the optical configuration at the β-carbon atom of the hydroxy acid fragment; the configuration in mycobactin S is S whereas that in mycobactin T is R (the previous assignment of this configuration was incorrect). The cobactin fragment of mycobactin H is identical with that of mycobactin S, but the mycobactic acid moiety differs in having methyl groups at position 6 in the benzene ring and at position 5 in the oxazoline ring. The configurations of all the asymmetric centres have been established for both mycobactins. Improved and simplified methods for the extraction and purification of mycobactins are described.

Chiral β3-isocyanopropionates for multicomponent synthesis of peptides and depsipeptides containing a β-amino acid fragment

2018 ◽  
Vol 16 (33) ◽  
pp. 5987-5998 ◽  
Author(s):  
Danil P. Zarezin ◽  
Olga I. Shmatova ◽  
Valentine G. Nenajdenko
Keyword(s):  
Amino Acid ◽  
Multicomponent Reactions ◽  
Short Peptides ◽  
Multicomponent Synthesis ◽  
Acid Moiety ◽  
Amino Acid Fragment ◽  
Acid Fragment ◽  
Amino Acid Moiety ◽  
New Type

Chiral β3-isocyanopropionic acids derivatives is a new type of isocyanides for multicomponent reactions. The use of these isocyanides in Ugi and Passerini reactions allows to prepare short peptides and depsipeptides with β-amino acid moiety in the structure.

Understanding the reaction that powers this world: Biomimetic studies of respiratory O2 reduction by cytochrome oxidase.

2004 ◽  
Vol 76 (6) ◽  
pp. 1293
Author(s):  
Roman Boulatov
Keyword(s):  
Organic Chemistry ◽  
Cytochrome Oxidase ◽  
Chemical Structure ◽  
Methyl Groups ◽  
Corrected Version ◽  
O2 Reduction ◽  
Fundamental Research

As was drawn to my attention by Prof.Y. Naruta (Institute for Fundamental Research of Organic Chemistry, Kyushu University, Japan; <[email protected]>), the chemical structure in original Fig. 5 erroneously omitted 3-methyl groups from the distal pyridines and showed an ether rather than the correct amide linker between the porphin and the distal superstructure. In addition, the caption did not make it sufficiently clear that the O2 adduct is a monocation,whose counterion, BF4−, was omitted for clarity.The corrected version of Fig. 5 with the caption is below.

scholarly journals The primary step of biotin synthesis in mycobacteria

2020 ◽  
Vol 117 (38) ◽  
pp. 23794-23801
Author(s):  
Zhe Hu ◽  
John E. Cronan
Keyword(s):  
Mycobacterium Smegmatis ◽  
Deletion Mutant ◽  
Essential Role ◽  
In Vivo Studies ◽  
Pimelic Acid ◽  
Chronic Infections ◽  
Acid Moiety ◽  
E Coli

Biotin plays an essential role in growth of mycobacteria. Synthesis of the cofactor is essential forMycobacterium tuberculosisto establish and maintain chronic infections in a murine model of tuberculosis. Although the late steps of mycobacterial biotin synthesis, assembly of the heterocyclic rings, are thought to follow the canonical pathway, the mechanism of synthesis of the pimelic acid moiety that contributes most of the biotin carbon atoms is unknown. We report that theMycobacterium smegmatisgene annotated as encoding Tam, anO-methyltransferase that monomethylates and detoxifiestrans-aconitate, instead encodes a protein having the activity of BioC, anO-methyltransferase that methylates the free carboxyl of malonyl-ACP. TheM. smegmatisTam functionally replacedEscherichia coliBioC both in vivo and in vitro. Moreover, deletion of theM. smegmatis tamgene resulted in biotin auxotrophy, and addition of biotin toM. smegmatiscultures repressedtamgene transcription. Although its pathogenicity precluded in vivo studies, theM. tuberculosisTam also replacedE. coliBioC both in vivo and in vitro and complemented biotin-independent growth of theM. smegmatis tamdeletion mutant strain. Based on these data, we propose that the highly conserved mycobacterial tamgenes be renamedbioC.M. tuberculosisBioC presents a target for antituberculosis drugs which thus far have been directed at late reactions in the pathway with some success.

scholarly journals The Extraction, Functionalities and Applications of Plant Polysaccharides in Fermented Foods: A Review

Foods ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3004
Author(s):  
Theoneste Niyigaba ◽  
Diru Liu ◽  
Jean de Dieu Habimana
Keyword(s):  
Chemical Structure ◽  
Biological Activities ◽  
Health Benefits ◽  
Fermented Foods ◽  
Plant Polysaccharides ◽  
Gelling Agents ◽  
Extraction And Purification ◽  
Fat Substitutes ◽  
Purification Methods ◽  
Structure Extraction

Plant polysaccharides, as prebiotics, fat substitutes, stabilizers, thickeners, gelling agents, thickeners and emulsifiers, have been immensely studied for improving the texture, taste and stability of fermented foods. However, their biological activities in fermented foods are not yet properly addressed in the literature. This review summarizes the classification, chemical structure, extraction and purification methods of plant polysaccharides, investigates their functionalities in fermented foods, especially the biological activities and health benefits. This review may provide references for the development of innovative fermented foods containing plant polysaccharides that are beneficial to health.

scholarly journals Crystal structures of a manganese(I) and a rhenium(I) complex of a bipyridine ligand with a non-coordinating benzoic acid moiety

2018 ◽  
Vol 74 (5) ◽  
pp. 731-736 ◽  
Author(s):  
Sheri Lense ◽  
Ilia A. Guzei ◽  
Jessica Andersen ◽  
Kong Choua Thao
Keyword(s):  
Hydrogen Bonds ◽  
Benzoic Acid ◽  
Metal Ion ◽  
Solvent Molecule ◽  
Acid Group ◽  
Distorted Octahedral Geometry ◽  
Acid Moiety ◽  
Rhenium Complex ◽  
Acid Fragment ◽  
Solvent Molecules

The structures of two facially coordinated Group VII metal complexes are reported, namely: fac-bromido[2-(2,2′-bipyridin-6-yl)benzoic acid-κ2 N,N′]tricarbonylmanganese(I) tetrahydrofuran monosolvate, [MnBr(C17H12N2O2)(CO)3]·C4H8O, I, and fac-[2-(2,2′-bipyridin-6-yl)benzoic acid-κ2 N,N′]tricarbonylchloridorhenium(I) tetrahydrofuran monosolvate, [ReCl(C17H12N2O2)(CO)3]·C4H8O, II. In both complexes, the metal ion is coordinated by three carbonyl ligands, a halide ion, and a 2-(2,2′-bipyridin-6-yl)benzoic acid ligand, in a distorted octahedral geometry. In manganese complex I, the tetrahydrofuran (THF) solvent molecule could not be refined due to disorder. The benzoic acid fragment is also disordered over two positions, such that the carboxylic acid group is either positioned near to the bromide ligand or to the axial carbonyl ligand. In the crystal of I, the complex molecules are linked by a pair of C—H...Br hydrogen bonds, forming inversion dimers that stack up the a-axis direction. In the rhenium complex II, there is hydrogen bonding between the benzoic acid moiety and a disordered co-crystallized THF molecule. In the crystal, the molecules are linked by C—H...Cl hydrogen bonds, forming layers parallel to (100) separated by layers of THF solvent molecules.

Inelastic Electron-Matter Interactions

1978 ◽  
Vol 36 (3) ◽  
pp. 259-267
Author(s):  
J. Silcox
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Chemical Structure ◽  
Inelastic Electron ◽  
Primary Concern ◽  
Unique Probe ◽  
Introductory Paper ◽  
Elastic Processes ◽  
Experimental Level ◽  
Inelastic Processes

In this introductory paper, my primary concern will be in identifying and outlining the various types of inelastic processes resulting from the interaction of electrons with matter. Elastic processes are understood reasonably well at the present experimental level and can be regarded as giving information on spatial arrangements. We need not consider them here. Inelastic processes do contain information of considerable value which reflect the electronic and chemical structure of the sample. In combination with the spatial resolution of the electron microscope, a unique probe of materials is finally emerging (Hillier 1943, Watanabe 1955, Castaing and Henri 1962, Crewe 1966, Wittry, Ferrier and Cosslett 1969, Isaacson and Johnson 1975, Egerton, Rossouw and Whelan 1976, Kokubo and Iwatsuki 1976, Colliex, Cosslett, Leapman and Trebbia 1977). We first review some scattering terminology by way of background and to identify some of the more interesting and significant features of energy loss electrons and then go on to discuss examples of studies of the type of phenomena encountered. Finally we will comment on some of the experimental factors encountered.

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