scholarly journals The S-Layer Glycome—Adding to the Sugar Coat of Bacteria

2011 ◽  
Vol 2011 ◽  
pp. 1-16 ◽  
Author(s):  
Robin Ristl ◽  
Kerstin Steiner ◽  
Kristof Zarschler ◽  
Sonja Zayni ◽  
Paul Messner ◽  
...  
Keyword(s):  
Unique Feature ◽  
Nanometer Scale ◽  
Capsular Polysaccharides ◽  
Glycosidic Linkage ◽  
Cell Surfaces ◽  
X Ray ◽  
Tyrosine Residues ◽  
X Ray Crystallography ◽  
Gram Positive Bacteria ◽  
Self Assembling

The amazing repertoire of glycoconjugates present on bacterial cell surfaces includes lipopolysaccharides, capsular polysaccharides, lipooligosaccharides, exopolysaccharides, and glycoproteins. While the former are constituents of Gram-negative cells, we review here the cell surface S-layer glycoproteins of Gram-positive bacteria. S-layer glycoproteins have the unique feature of self-assembling into 2D lattices providing a display matrix for glycans with periodicity at the nanometer scale. Typically, bacterial S-layer glycans are O-glycosidically linked to serine, threonine, or tyrosine residues, and they rely on a much wider variety of constituents, glycosidic linkage types, and structures than their eukaryotic counterparts. As the S-layer glycome of several bacteria is unravelling, a picture of how S-layer glycoproteins are biosynthesized is evolving. X-ray crystallography experiments allowed first insights into the catalysis mechanism of selected enzymes. In the future, it will be exciting to fully exploit the S-layer glycome for glycoengineering purposes and to link it to the bacterial interactome.

Designer cyclopeptides for self-assembled tubular structures

2000 ◽  
Vol 72 (3) ◽  
pp. 365-372 ◽  
Author(s):  
Darshan Ranganathan ◽  
C. Lakshmi ◽  
V. Haridas ◽  
M. Gopikumar
Keyword(s):  
Design Strategy ◽  
Single Step ◽  
Simple Design ◽  
Tubular Structures ◽  
Peptide Nanotubes ◽  
X Ray ◽  
X Ray Crystallography ◽  
Self Assembling ◽  
Direct Condensation ◽  
Hydrogen Bonded

A simple design strategy for a facile and direct entry into hydrogen-bonded peptide nanotubes is delineated with polymethylene-bridged cystine-based macrocycles. The key feature of the design is the placement of a pair of self-complementary hydrogen-bonding (NH–CO or NH–CO–NH) groups at almost opposite poles of the ring. A large variety of cyclobisamides and bisureas prepared in a single step by direct condensation of commercially available 1,ω-alkane dicarbonyl dichloride or diisocyanate with either cystine diOMe or its extended bispeptide were examined by X-ray crystallography and shown to possess an inherent property of self-assembling into hydrogen-bonded, open-ended, hollow tubular structures. The totally hydrophobic interior of the cyclobisamide tubes creates a micro environment capable of solubilizing highly lipophilic substances in water. The cyclic bisurea tubes are demonstrated to act as excellent receptors for selective binding to 1,ω-alkane dicarboxylates. The scope of the design is extended to the creation of tubular structures by stacking of rings through aromatic π-π interactions.

scholarly journals Synthesis, Characterization, and Antibacterial Activity of Diethyl 1-((4-Methyl-2-phenyl-4,5-dihydrooxazol-4-yl)methyl)-1H-1,2,3-triazole-4,5-dicarboxylate

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
S. Boukhssas ◽  
Y. Aouine ◽  
H. Faraj ◽  
A. Alami ◽  
A. El Hallaoui ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Cycloaddition Reaction ◽  
Bactericidal Effect ◽  
High Yield ◽  
Dipolar Cycloaddition ◽  
Gram Negative Bacteria ◽  
X Ray ◽  
X Ray Crystallography ◽  
Gram Positive Bacteria

The compound, diethyl 1-((4-methyl-2-phenyl-4,5-dihydrooxazol-4-yl)methyl)-1H-1,2,3-triazole-4,5-dicarboxylate 2, was synthesized in high yield, through 1,3-dipolar cycloaddition reaction of 4-(azidomethyl)-4-methyl-2-phenyl-4,5-dihydrooxazole and diethyl but-2-ynedioate in the absence of a solvent. The structure of the synthesized compound was established on the basis of NMR spectroscopy (1H, 13C), X-ray crystallography, and MS data. The prepared compound was also tested in vitro for its antibacterial activity against Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli). The calculation of MBC/MIC ratio showed that this triazole derivative 2 had a bactericidal effect on the two strains tested.

scholarly journals Expanding the Family of Tetrahalide Iron Complexes: Synthesis, Structure and Biological Applications.

2020 ◽  
Author(s):  
Nusrat Abedin ◽  
Abdullah Hamed A Alshehri ◽  
Ali M A Almughrbi ◽  
Olivia Moore ◽  
Sheikh Alyza ◽  
...  
Keyword(s):  
Antimicrobial Properties ◽  
Biological Properties ◽  
Biological Applications ◽  
X Ray ◽  
Mononuclear Iron ◽  
X Ray Crystallography ◽  
Gram Positive Bacteria ◽  
Axial Ligands ◽  
The Family ◽  
Resistant Strains

A neutral octahedral mononuclear iron(II) tetrabromide complex, [Fe(Hampy)<sub>2</sub>Br<sub>4</sub>], that consists of equatorial bromide and protonated aminopyrazinium axial ligands is successfully synthesised through redox chemistry and analysed using X-ray crystallography. The iron(II) oxidation state is balanced by the protonated pyrazinium nitrogen just outside the coordination sphere. The biological properties of this and two other related complexes are investigated using both Gram-negative and Gram-positive bacteria as well as methicillin resistant strains. They all exhibit some antimicrobial properties albeit at moderate to poor concentrations. However, the tetrahalide complexes analysed exhibit excellent anti biofilm properties well below cytotoxic levels.

scholarly journals Synthesis, Characterization, and Bioactivity of Schiff Bases and TheirCd2+,Zn2+,Cu2+, andNi2+Complexes Derived from Chloroacetophenone Isomers with S-Benzyldithiocarbazate and the X-Ray Crystal Structure of S-Benzyl-β-N-(4-chlorophenyl)methylenedithiocarbazate

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Mohammed Khaled bin Break ◽  
M. Ibrahim M. Tahir ◽  
Karen A. Crouse ◽  
Teng-Jin Khoo
Keyword(s):  
Crystal Structure ◽  
Phenyl Ring ◽  
Crystallographic Analysis ◽  
Gram Negative Bacteria ◽  
Schiff Base Ligands ◽  
Gram Negative ◽  
X Ray ◽  
X Ray Crystallography ◽  
Gram Positive Bacteria ◽  
Antimicrobial Assay

Two bidentate Schiff base ligands having nitrogen sulphur donor sequence were derived from the condensation of S-benzyldithiocarbazate (SBDTC) with 2-chloroacetophenone and 4-chloroacetophenone to give S-benzyl-β-N-(2-chlorophenyl)methylenedithiocarbazate (NS2) and S-benzyl-β-N-(4-chlorophenyl)methylenedithiocarbazate (NS4) isomers. Each of the ligands was then chelated with Cd2+, Zn2+, Cu2+, and Ni2+. The compounds were characterized via IR spectroscopy and melting point while the structure of NS4 was revealed via X-ray crystallography. Finally, the compounds were screened for antimicrobial activity to investigate the effect that is brought by the introduction of the chlorine atom to the benzene ring. X-ray crystallographic analysis showed that the structure of NS4 is planar with a phenyl ring that is nearly perpendicular to the rest of the molecules. The qualitative antimicrobial assay results showed that NS4 and its complexes lacked antifungal activity while Gram-positive bacteria were generally inhibited more strongly than Gram-negative bacteria. Furthermore, NS4 metal complexes were inhibited more strongly than the ligand while the opposite was seen with NS2 ligand and its complexes due to the partial solubility in dimethyl sulfoxide (DMSO). It was concluded that generally NS2 derivatives have higher bioactivity than that of NS4 derivatives and that the Cd complexes of both ligands have pronounced activity specifically onK. rhizophila.

scholarly journals Expanding the Family of Tetrahalide Iron Complexes: Synthesis, Structure and Biological Applications.

2020 ◽  
Author(s):  
Nusrat Abedin ◽  
Abdullah Hamed A Alshehri ◽  
Ali M A Almughrbi ◽  
Olivia Moore ◽  
Sheikh Alyza ◽  
...  
Keyword(s):  
Antimicrobial Properties ◽  
Biological Properties ◽  
Biological Applications ◽  
X Ray ◽  
Mononuclear Iron ◽  
X Ray Crystallography ◽  
Gram Positive Bacteria ◽  
Axial Ligands ◽  
The Family ◽  
Resistant Strains

A neutral octahedral mononuclear iron(II) tetrabromide complex, [Fe(Hampy)<sub>2</sub>Br<sub>4</sub>], that consists of equatorial bromide and protonated aminopyrazinium axial ligands is successfully synthesised through redox chemistry and analysed using X-ray crystallography. The iron(II) oxidation state is balanced by the protonated pyrazinium nitrogen just outside the coordination sphere. The biological properties of this and two other related complexes are investigated using both Gram-negative and Gram-positive bacteria as well as methicillin resistant strains. They all exhibit some antimicrobial properties albeit at moderate to poor concentrations. However, the tetrahalide complexes analysed exhibit excellent anti biofilm properties well below cytotoxic levels.

scholarly journals Organotrifluoroborates as attractive self-assembling systems: the case of bifunctional dipotassium phenylene-1,4-bis(trifluoroborate)

2015 ◽  
Vol 44 (45) ◽  
pp. 19447-19450 ◽  
Author(s):  
Aurelia Falcicchio ◽  
Sten O. Nilsson Lill ◽  
Filippo M. Perna ◽  
Antonio Salomone ◽  
Donato I. Coppi ◽  
...  
Keyword(s):  
Computational Chemistry ◽  
Self Assembly ◽  
X Ray ◽  
Dipotassium Salt ◽  
X Ray Crystallography ◽  
Self Assembling ◽  
Non Covalent Interactions ◽  
Covalent Interactions

A multitude of non-covalent interactions, investigated by X-ray crystallography and computational chemistry techniques, proved to be responsible of the spontaneous self-assembly of a bis(trifluoroborate) dipotassium salt.

scholarly journals Chiral Self-Sorting in Truxene-Based Metallacages

Inorganics ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 1 ◽  
Author(s):  
Simon Séjourné ◽  
Antoine Labrunie ◽  
Clément Dalinot ◽  
Amina Benchohra ◽  
Vincent Carré ◽  
...  
Keyword(s):  
Solid State ◽  
The Self ◽  
X Ray ◽  
X Ray Crystallography ◽  
Self Assembling ◽  
Sorting Process ◽  
Non Covalent Interactions ◽  
Covalent Interactions

Two chiral face-rotating metalla-assembled polyhedra were constructed upon self-assembling achiral components, i.e., a tritopic ligand based on a truxene core (10,15-dihydro-5H-diindeno[1,2-a;1′,2′-c]fluorene) and two different hydroxyquinonato–bridged diruthenium complexes. Both polyhedra were characterized in solution as well as in the solid state by X-ray crystallography. In both cases, the self-sorting process leading to only two homo-chiral enantiomers was governed by non-covalent interactions between both truxene units that faced each other.

scholarly journals Determinants of Substrate Specificity in ω-Aminotransferases

2005 ◽  
Vol 280 (43) ◽  
pp. 36409-36416 ◽  
Author(s):  
Michaela Markova ◽  
Caroline Peneff ◽  
Michael J. E. Hewlins ◽  
Tilman Schirmer ◽  
Robert A. John
Keyword(s):  
Pyridoxal Phosphate ◽  
Ornithine Aminotransferase ◽  
X Ray ◽  
Aminobutyrate Aminotransferase ◽  
Tyrosine Residues ◽  
X Ray Crystallography ◽  
Atomic Structures ◽  
Reaction Conversion ◽  
Kinetics Of ◽  
C Nmr

Ornithine aminotransferase and 4-aminobutyrate aminotransferase are related pyridoxal phosphate-dependent enzymes having different substrate specificities. The atomic structures of these enzymes have shown (i) that active site differences are limited to the steric positions occupied by two tyrosine residues in ornithine aminotransferase and (ii) that, uniquely among related, structurally characterized aminotransferases, the conserved arginine that binds the α-carboxylate of α-amino acids interacts tightly with a glutamate residue. To determine the contribution of these residues to the specificities of the enzymes, we analyzed site-directed mutants of ornithine aminotransferase by rapid reaction kinetics, x-ray crystallography, and 13C NMR spectroscopy. Mutation of one tyrosine (Tyr-85) to isoleucine, as found in aminobutyrate aminotransferase, decreased the rate of the reaction of the enzyme with ornithine 1000-fold and increased that with 4-aminobutyrate 16-fold, indicating that Tyr-85 is a major determinant of specificity toward ornithine. Unexpectedly, the limiting rate of the second half of the reaction, conversion of ketoglutarate to glutamate, was greatly increased, although the kinetics of the reverse reaction were unaffected. A mutant in which the glutamate (Glu-235) that interacts with the conserved arginine was replaced by alanine retained its regiospecificity for the δ-amino group of ornithine, but the glutamate reaction was enhanced 650-fold, whereas only a 5-fold enhancement of the ketoglutarate reaction rate resulted. A model is proposed in which conversion of the enzyme to its pyridoxamine phosphate form disrupts the internal glutamate-arginine interaction, thus enabling ketoglutarate but not glutamate to be a good substrate.

scholarly journals De novo macrolide–glycolipid macrolactone hybrids: Synthesis, structure and antibiotic activity of carbohydrate-fused macrocycles

2014 ◽  
Vol 10 ◽  
pp. 2215-2221 ◽  
Author(s):  
Richard T Desmond ◽  
Anniefer N Magpusao ◽  
Chris Lorenc ◽  
Jeremy B Alverson ◽  
Nigel Priestley ◽  
...  
Keyword(s):  
Natural Product ◽  
Dihedral Angle ◽  
Hydroxy Group ◽  
De Novo ◽  
Antibiotic Activity ◽  
Anomeric Effect ◽  
Glycosidic Linkage ◽  
Antibacterial Compounds ◽  
X Ray ◽  
X Ray Crystallography

Natural product-like macrocycles were designed as potential antibacterial compounds. The macrocycles featured a D-glucose unit fused into a 12- or 13-member macrolactone. The rings are connected via the C6’ and anomeric (C1’) positions of the monosaccharide. The new macrocycles/macrolides were characterized by X-ray crystallography. Their structures showed that, in addition to the ester and alkene units, the dihedral angle about the glycosidic linkage (exo-anomeric effect) influenced the overall shape of the molecules. Glycosylation of an available hydroxy group on the macrocycle gave a hybrid macrolide with features common to erythromycin and sophorlipid macrolactone. Weak antibiotic activity (MICs <100 μg/mL) was observed for several of the compounds.

scholarly journals Following replicative DNA synthesis by time-resolved X-ray crystallography

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Nicholas Chim ◽  
Roman A. Meza ◽  
Anh M. Trinh ◽  
Kefan Yang ◽  
John C. Chaput
Keyword(s):  
Dna Synthesis ◽  
Structural Changes ◽  
Reaction Pathway ◽  
Dna Polymerases ◽  
Enzymatic Catalysis ◽  
Time Resolved ◽  
X Ray ◽  
Tyrosine Residues ◽  
X Ray Crystallography ◽  
Unidirectional Movement

AbstractThe mechanism of DNA synthesis has been inferred from static structures, but the absence of temporal information raises longstanding questions about the order of events in one of life’s most central processes. Here we follow the reaction pathway of a replicative DNA polymerase using time-resolved X-ray crystallography to elucidate the order and transition between intermediates. In contrast to the canonical model, the structural changes observed in the time-lapsed images reveal a catalytic cycle in which translocation precedes catalysis. The translocation step appears to follow a push-pull mechanism where the O-O1 loop of the finger subdomain acts as a pawl to facilitate unidirectional movement along the template with conserved tyrosine residues 714 and 719 functioning as tandem gatekeepers of DNA synthesis. The structures capture the precise order of critical events that may be a general feature of enzymatic catalysis among replicative DNA polymerases.

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