Optical studies of the genesis of ligand-free cobalt and rhodium clusters: relevance to oxide- and polymer-bound cobalt and rhodium clusters

1979 ◽  
Vol 18 (7) ◽  
pp. 1781-1790 ◽  
Author(s):  
Geoffrey A. Ozin ◽  
A. J. Lee Hanlan
Keyword(s):  
Optical Studies ◽  
Rhodium Clusters ◽  
Ligand Free

CarR, a MarR-family regulator from Corynebacterium glutamicum, modulated antibiotic and aromatic compound resistance

2019 ◽  
Vol 476 (21) ◽  
pp. 3141-3159 ◽  
Author(s):  
Meiru Si ◽  
Can Chen ◽  
Zengfan Wei ◽  
Zhijin Gong ◽  
GuiZhi Li ◽  
...  
Keyword(s):  
Stress Response ◽  
Ligand Binding ◽  
Corynebacterium Glutamicum ◽  
Conformational Changes ◽  
Cysteine Oxidation ◽  
Transcriptional Regulatory ◽  
Ligand Free ◽  
Redox Sensing

Abstract MarR (multiple antibiotic resistance regulator) proteins are a family of transcriptional regulators that is prevalent in Corynebacterium glutamicum. Understanding the physiological and biochemical function of MarR homologs in C. glutamicum has focused on cysteine oxidation-based redox-sensing and substrate metabolism-involving regulators. In this study, we characterized the stress-related ligand-binding functions of the C. glutamicum MarR-type regulator CarR (C. glutamicum antibiotic-responding regulator). We demonstrate that CarR negatively regulates the expression of the carR (ncgl2886)–uspA (ncgl2887) operon and the adjacent, oppositely oriented gene ncgl2885, encoding the hypothetical deacylase DecE. We also show that CarR directly activates transcription of the ncgl2882–ncgl2884 operon, encoding the peptidoglycan synthesis operon (PSO) located upstream of carR in the opposite orientation. The addition of stress-associated ligands such as penicillin and streptomycin induced carR, uspA, decE, and PSO expression in vivo, as well as attenuated binding of CarR to operator DNA in vitro. Importantly, stress response-induced up-regulation of carR, uspA, and PSO gene expression correlated with cell resistance to β-lactam antibiotics and aromatic compounds. Six highly conserved residues in CarR were found to strongly influence its ligand binding and transcriptional regulatory properties. Collectively, the results indicate that the ligand binding of CarR induces its dissociation from the carR–uspA promoter to derepress carR and uspA transcription. Ligand-free CarR also activates PSO expression, which in turn contributes to C. glutamicum stress resistance. The outcomes indicate that the stress response mechanism of CarR in C. glutamicum occurs via ligand-induced conformational changes to the protein, not via cysteine oxidation-based thiol modifications.

OPTICAL STUDIES OF TYPE I AND TYPE II RECOMBINATION IN GaAs-AlAs QUANTUM WELLS

1987 ◽  
Vol 48 (C5) ◽  
pp. C5-525-C5-528 ◽  
Author(s):  
K. J. MOORE ◽  
P. DAWSON ◽  
C. T. FOXON
Keyword(s):  
Quantum Wells ◽  
Type I ◽  
Type Ii ◽  
Optical Studies

Copper-Catalyzed Hydrocarboxylation of Allenes

2019 ◽  
Author(s):  
Rémi blieck ◽  
Marc Taillefer ◽  
Florian Monnier
Keyword(s):  
Carboxylic Acids ◽  
Copper Catalysis ◽  
Ligand Free ◽  
First Time

The addition of carboxylic acids to allenes was performed for the first time with copper catalysis. The hydrocarboxylation reaction is totally regio- and stereoselective, ligand-free and used catalytic amounts of copper and base.

Optical studies of cadmium

1970 ◽  
Author(s):  
Roger James Bartlett
Keyword(s):  
Optical Studies

Ag2O/GO/TiO2 composite nanoparticles: synthesis, characterization, and optical studies

2020 ◽  
Author(s):  
Farzad Bayati ◽  
Mohammad Kazem Mohammadi ◽  
Reza Jalilzadeh Yengejeh ◽  
Ali Akbar Babaei
Keyword(s):  
Composite Nanoparticles ◽  
Optical Studies ◽  
Nanoparticles Synthesis
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