gem-Difluorination versus 1,2-migration and fragmentation in the reaction of 2- and 3-uloses with DAST. Influence of stereochemistry at the anomeric carbon atom

1991 ◽  
Vol 56 (14) ◽  
pp. 4556-4559 ◽  
Author(s):  
Anas El-Laghdagh ◽  
Raouf Echarri ◽  
M. Isabel Matheu ◽  
M. Isabel Barrena ◽  
Sergio Castillon ◽  
...  
Keyword(s):  
Carbon Atom ◽  
Anomeric Carbon ◽  
Anomeric Carbon Atom

A simple method of calculating the molecular rotations of the sulfur, nitrogen and phosphorus analogues of α-D-glycopyranoses having different substituents at the anomeric carbon atom

1984 ◽  
Vol 37 (5) ◽  
pp. 971 ◽  
Author(s):  
B Poh
Keyword(s):  
Carbon Atom ◽  
Phosphorus Atom ◽  
Nitrogen And Phosphorus ◽  
Simple Method ◽  
Anomeric Carbon ◽  
Molecular Rotations ◽  
Anomeric Carbon Atom

The values of m and I of equation (1) for several series of α-D-glycopyranoses having different substituents at the anomeric carbon atom have been obtained earlier. From these values, the molecular rotations of the corresponding sugars containing a sulfur, nitrogen, or phosphorus atom in the ring have been calculated and found to agree satisfactorily with the corresponding literature values.

ChemInform Abstract: gem-Difluorinations versus 1,2-Migration and Fragmentation in the Reaction of 2- and 3-Uloses with DAST. Influence of Stereochemistry at the Anomeric Carbon Atom.

ChemInform ◽  
2010 ◽  
Vol 22 (47) ◽  
pp. no-no
Author(s):  
A. EL-LAGHDACH ◽  
R. ECHARRI ◽  
M. I. MATHEU ◽  
M. I. BARRENA ◽  
S. CASTILLON ◽  
...  
Keyword(s):  
Carbon Atom ◽  
Anomeric Carbon ◽  
Anomeric Carbon Atom

scholarly journals The β-glucosidase from Botryodiplodia theobromae Pat. Kinetics of enzyme-catalysed hydrolysis of o-nitrophenyl β-d-glucopyranoside in dioxan/water

1978 ◽  
Vol 175 (2) ◽  
pp. 455-459 ◽  
Author(s):  
G M Umezurike
Keyword(s):  
Maximum Rate ◽  
Buffer System ◽  
Botryodiplodia Theobromae ◽  
Hydrolytic Reaction ◽  
Anomeric Carbon ◽  
Rate Of Hydrolysis ◽  
Beta Glucosidase ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Anomeric Carbon Atom

1. The hydrolysis of o-nitrophenyl beta-D-glucopyranoside by the high-molecular-weight beta-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) from Botryodiplodia theobromae Pat. has been studied in the presence of added dioxan. 2. At donor saturation, the maximum rate of hydrolysis in the presence of up to 50%(v/v) dioxan was pH4.3-4.5 (pH of the buffer system in water) in McIlvaine's buffer. 3. Increasing dioxan concentrations progressively decreased the maximum rate of hydrolysis. 4. The rate of enzyme-catalysed reaction was enhanced at high donor concentrations, but inhibited at low donor concentrations in the presence of glycerol, methanol, fructose of sucrose. 5. The hydrolytic reaction was found to proceed with retention of configuration at the anomeric carbon atom. 6. The kinetics of the enzyme-catalysed process in the presence of added acceptors indicated that water was necessary for the maintenance of the active enzyme conformation apart from its acceptor function.

An atomic resolution study of a carbide phase in platinum

1992 ◽  
Vol 50 (1) ◽  
pp. 20-21
Author(s):  
M.J. Witcomb ◽  
M.A. O'Keefe ◽  
CJ. Echer ◽  
C. Nelson ◽  
J.H. Turner ◽  
...  
Keyword(s):  
Solid Solution ◽  
Carbon Atom ◽  
Carbide Phase ◽  
Structural Changes ◽  
Critical Role ◽  
Alloy System ◽  
Atomic Resolution ◽  
Excess Carbon ◽  
Interstitial Carbon ◽  
Resolution Study

Under normal circumstances, Pt dissolves only a very small amount of interstitial carbon in solid solution. Even so, an appropriate quench/age treatment leads to the formation of stable Pt2C {100} plate precipitates. Excess (quenched-in) vacancies play a critical role in the process by accommodating the volume and structural changes that accompany the transformation. This alloy system exhibits other interesting properties. Due to a large vacancy/carbon atom binding energy, Pt can absorb excess carbon at high temperatures in a carburizing atmosphere. In regions rich in carbon and vacancies, another carbide phase, Pt7C which undergoes an order-disorder reaction was formed. The present study of Pt carburized at 1160°C and aged at 515°C shows that other carbides in the PtxC series can be produced.

A common precursor to both prebiotic and biological pathways to RNA nucleotides

2018 ◽  
Author(s):  
Andrea Pérez-Villa ◽  
Thomas Georgelin ◽  
Jean-François Lambert ◽  
Marie-Christine Maurel ◽  
François Guyot ◽  
...  
Keyword(s):  
Enzymatic Synthesis ◽  
De Novo ◽  
Life Forms ◽  
Hydrothermal Conditions ◽  
Modern Life ◽  
Ab Initio Simulations ◽  
Spontaneous Formation ◽  
Common Precursor ◽  
Open Issue ◽  
Anomeric Carbon

Understanding the mechanism of spontaneous formation of ribonucleotides under realistic prebiotic conditions is a key open issue of origins-of-life research. In cells, <i>de novo</i> and salvage nucleotide enzymatic synthesis combines 5-phospho-α -D-ribose-1-diphosphate ( α-PRPP) and nucleobases. Interestingly, these reactants are also known as prebiotically plausible compounds. Combining ab initio simulations with mass spectrometry experiments, we compellingly demonstrate that nucleobases and α -PRPP spontaneously combine, through the same facile mechanism, forming both purine and pyrimidine ribonucleotides, under mild hydrothermal conditions. Surprisingly, this mechanism is very similar to the biological one, and yields ribonucleotides with the same anomeric carbon chirality as in biological systems. These results suggest that natural selection might have optimized – through enzymes – a pre-existing ribonucleotide formation mechanism, carrying it forward to modern life forms.

A common precursor to both prebiotic and biological pathways to RNA nucleotides

2017 ◽  
Author(s):  
Andrea Pérez-Villa ◽  
Thomas Georgelin ◽  
Jean-François Lambert ◽  
Marie-Christine Maurel ◽  
François Guyot ◽  
...  
Keyword(s):  
Enzymatic Synthesis ◽  
De Novo ◽  
Life Forms ◽  
Hydrothermal Conditions ◽  
Modern Life ◽  
Ab Initio Simulations ◽  
Spontaneous Formation ◽  
Common Precursor ◽  
Open Issue ◽  
Anomeric Carbon

Understanding the mechanism of spontaneous formation of ribonucleotides under realistic prebiotic conditions is a key open issue of origins-of-life research. In cells, <i>de novo</i> and salvage nucleotide enzymatic synthesis combines 5-phospho-α -D-ribose-1-diphosphate ( α-PRPP) and nucleobases. Interestingly, these reactants are also known as prebiotically plausible compounds. Combining ab initio simulations with mass spectrometry experiments, we compellingly demonstrate that nucleobases and α -PRPP spontaneously combine, through the same facile mechanism, forming both purine and pyrimidine ribonucleotides, under mild hydrothermal conditions. Surprisingly, this mechanism is very similar to the biological one, and yields ribonucleotides with the same anomeric carbon chirality as in biological systems. These results suggest that natural selection might have optimized – through enzymes – a pre-existing ribonucleotide formation mechanism, carrying it forward to modern life forms.

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