Protonation de l'adénine, de la purine et de l'adénosine en milieu acide fort

1984 ◽  
Vol 62 (5) ◽  
pp. 995-1000 ◽  
Author(s):  
Robert L. Benoit ◽  
Monique Fréchette
Keyword(s):  
Chemical Shifts ◽  
Imidazole Ring ◽  
Pyrimidine Ring ◽  
The Other ◽  
Medium Effect ◽  
Hydrolytic Cleavage ◽  
The Third ◽  
Nmr Data ◽  
Solid Bases ◽  
Proton Chemical Shifts

In view of a previously proposed enthalpy value for the second protonation of adenine, a calorimetric and nmr spectroscopic study has been made of the protonation of biologically important bases B: adenine, purine, adenosine and, incidentally, that of imidazole and 3-amino pyridine. Heats of solution of the solid bases, and their carbon-13 and proton chemical shifts were determined as a function of HClO4 and H2SO4 concentration. Our results demonstrate that, contrary to previous usage, a strong medium effect precludes the use of the calorimetric results to calculate the thermodynamic functions for the protonation reactions. On the other hand, the carbon-13 nmr data are successfully interpreted on the basis of the Cox and Yates excess acidity method. The values obtained for [Formula: see text] and [Formula: see text] are, respectively: adenine −0.43, −4.23, purine −1.66, < −6, adenosine −1.4 with hydrolytic cleavage of the glycosidic bond. The protonation sites are confirmed as being essentially on the imidazole ring for the second protonation and on the pyrimidine ring (N-3) for the third one.

scholarly journals Real-time prediction of 1H and 13C chemical shifts with DFT accuracy using a 3D graph neural network

2021 ◽  
Author(s):  
Yanfei Guan ◽  
S. V. Shree Sowndarya ◽  
Liliana C. Gallegos ◽  
Peter C. St. John ◽  
Robert S. Paton
Keyword(s):  
Neural Network ◽  
Real Time ◽  
Quantum Chemical ◽  
Organic Molecules ◽  
Chemical Shifts ◽  
13C Chemical Shifts ◽  
Time Prediction ◽  
Nmr Data ◽  
Proton Chemical Shifts

From quantum chemical and experimental NMR data, a 3D graph neural network, CASCADE, has been developed to predict carbon and proton chemical shifts. Stereoisomers and conformers of organic molecules can be correctly distinguished.

Correlations of substituent effects on proton and fluorine chemical shifts with inverse ionization potentials

1967 ◽  
Vol 45 (24) ◽  
pp. 3143-3151 ◽  
Author(s):  
T. Schaefer ◽  
F. Hruska ◽  
H. M. Hutton
Keyword(s):  
Electric Fields ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Group Iv ◽  
The Other ◽  
Ionization Potentials ◽  
Time Dependent ◽  
Practical Application ◽  
Methyl Proton ◽  
Proton Chemical Shifts

The fluorine and proton chemical shifts in some geminally disubstituted vinylidene fluorides and ethylenes are discussed. For these compounds, at least, there are difficulties with an interpretation based on intramolecular time-dependent electric fields. On the other hand, the shifts correlate with the inverse ionization potentials of the substituents, indicating a paramagnetic effect arising from the second term in Ramsey's expression. It is suggested that the effect operates via the bonds and not across space. Methyl proton shifts in a series of substituted methyl compounds of group IV, V, and VI elements show similar correlations. A practical application of the correlation to spectral analysis problems is given.

The Molecular Structure of Allenes and Ketenes, XI Semiempirical Calculations of 1H-Chemical Shifts of Allenes

1977 ◽  
Vol 32 (11) ◽  
pp. 1296-1303 ◽  
Author(s):  
W. Runge
Keyword(s):  
Molecular Structure ◽  
Boundary Conditions ◽  
Chemical Shifts ◽  
Quantitative Description ◽  
Algebraic Model ◽  
Coupling Constants ◽  
Semiempirical Calculations ◽  
Proton Coupling ◽  
Nmr Data ◽  
Proton Chemical Shifts

A comparison between calculated and observed values demonstrates that “ansätze” derived from an algebraic model in connection with appropriate boundary conditions are able to account for a quantitative description of the proton chemical shifts of allenes.Correlations of the proton chemical shifts with other NMR data, such as 13C-chemical shifts and one-bond carbon-proton coupling constants, reveal some insigths into the nature of the 1H substituent chemical shifts of alienes.

Efficacy of some insecticide modules against major insect pests and spider population of rice, Oryza sativa L.

ENTOMON ◽  
2018 ◽  
Vol 43 (4) ◽  
pp. 257-262
Author(s):  
Atanu Seni ◽  
Bhimasen Naik
Keyword(s):  
Oryza Sativa ◽  
Grain Yield ◽  
Untreated Control ◽  
Insect Pests ◽  
Oryza Sativa L ◽  
Gall Midge ◽  
Stem Borer ◽  
The Other ◽  
The Third ◽  
Treated Plot

Experiments were carried out to assess some insecticide modules against major insect pests of rice. Each module consists of a basal application of carbofuran 3G @ 1 kg a.i ha-1 at 20 DAT and Rynaxypyr 20 SC @ 30 g a.i ha-1 at 45 DAT except untreated control. All modules differ with each other only in third treatment which was applied in 65 DAT. The third treatment includes: Imidacloprid 17.8 SL @ 27 g a.i ha-1, Pymetrozine 50 WG @ 150 g a.i ha-1, Triflumezopyrim 106 SC @ 27 g a.i ha-1, Buprofezin 25 SC @ 250 g a.i ha-1; Glamore (Imidacloprid 40+Ethiprole 40% w/w) 80 WG @ 100 g a.i. ha-1, Thiacloprid 24 SC @ 60 g a.i ha-1, Azadirachtin 0.03 EC @ 8 g a.i ha-1, Dinotefuran 20 SG@ 40 g a.i ha-1 and untreated control. All the treated plots recorded significantly lower percent of dead heart, white ear- head caused by stem borer and silver shoot caused by gall midge. Module with Pymetrozine 50 WG @ 150 g a.i ha-1 treated plot recorded significantly higher per cent reduction of plant hoppers (>80% over untreated control) and produced higher grain yield (50.75 qha-1) than the other modules. Among the different treated modules the maximum number of spiders was found in Azadirachtin 0.03 EC @ 8 g a.i ha-1 treated module plot followed by other treatments.

Retroaktive Neuverhandlung

2018 ◽  
Vol 63 (1) ◽  
Author(s):  
Daniel Martin Feige
Keyword(s):  
Original Work ◽  
The Other ◽  
Final Part ◽  
Critical Reading ◽  
The Third ◽  
Works Of Art ◽  
The Relationship

Der Beitrag widmet sich der Frage historischer Folgeverhältnisse in der Kunst. Gegenüber dem Gedanken, dass es ein ursprüngliches Werk in der Reihe von Werken gibt, das späteren Werken seinen Sinn gibt, schlägt der Text vor, das Verhältnis umgekehrt zu denken: Im Lichte späterer Werke wird der Sinn früherer Werke neu ausgehandelt. Dazu geht der Text in drei Schritten vor. Im ersten Teil formuliert er unter der Überschrift ›Form‹ in kritischer Abgrenzung zu Danto und Eco mit Adorno den Gedanken, dass Kunstwerke eigensinnig konstituierte Gegenstände sind. Die im Gedanken der Neuverhandlung früherer Werke im Lichte späterer Werke vorausgesetzte Unbestimmtheit des Sinns von Kunstwerken wird im zweiten Teil unter dem Schlagwort ›Zeitlichkeit‹ anhand des Paradigmas der Improvisation erörtert. Der dritte und letzte Teil wendet diese improvisatorische Logik unter dem Label ›Neuaushandlung‹ dann dezidiert auf das Verhältnis von Vorbild und Nachbild an. The article proposes a new understanding of historical succession in the realm of art. In contrast to the idea that there is an original work in the series of works that gives meaning to the works that come later, the text proposes to think it exactly the other way round: in the light of later works, the meanings of earlier works are renegotiated. The text proceeds in three steps to develop this idea. Under the heading ›Form‹ it develops in the first part a critical reading of Danto’s and Eco’s notion of the constitution of the artworks and argues with Adorno that each powerful work develops its own language. In the second part, the vagueness of the meaning of works of art presupposed in the idea of renegotiating earlier works in the light of later works is discussed under the term ›Temporality‹ in terms of the logic of improvisation. The third and final part uses this improvisational logic under the label ›Renegotiation‹ to understand the relationship between model and afterimage in the realm of art.

Features of the course and treatment of glaucoma during pregnancy

2020 ◽  
Vol 98 (3) ◽  
pp. 178-184
Author(s):  
T. V. Chernyakova ◽  
A. Yu. Brezhnev ◽  
I. R. Gazizova ◽  
A. V. Kuroyedov ◽  
A. V. Seleznev
Keyword(s):  
Pregnant Women ◽  
Laser Treatment ◽  
Progressive Disease ◽  
Clinical Course ◽  
The Other ◽  
Third Trimester ◽  
The Third ◽  
Chronic Progressive Disease ◽  
Hypotensive Therapy ◽  
Eye Pressure

In the review we have integrated all up-to-date knowledge concerning clinical course and treatment of glaucoma among pregnant women to help specialists choose a proper policy of treatment for such a complicated group of patients. Glaucoma is a chronic progressive disease. It rarely occurs among childbearing aged women. Nevertheless the probability to manage pregnant patients having glaucoma has been recently increasing. The situation is complicated by the fact that there are no recommendations on how to treat glaucoma among pregnant women. As we know, eye pressure is progressively going down from the first to the third trimester, so we often have to correct hypotensive therapy. Besides, it is necessary to take into account the effect of applied medicines on mother health and evaluate possible teratogenic complications for a fetus. The only medicine against glaucoma which belongs to category B according to FDA classification is brimonidine. Medicines of the other groups should be prescribed with care. Laser treatment or surgery may also be a relevant decision when monitoring patients who are planning pregnancy or just bearing a child. Such treatment should be also accompanied by medicines.

The Nile Delta during the Early Dynastic and Old Kingdom periods. Preliminary remarks on the evolution of settlement landscape

2020 ◽  
pp. 13-61
Author(s):  
Natalia Małecka-Drozd
Keyword(s):  
Nile Delta ◽  
Ancient Egypt ◽  
The Other ◽  
Old Kingdom ◽  
The Third ◽  
Other Hand ◽  
Early Dynastic ◽  
Territorial Structure ◽  
Settlement Landscape ◽  
New Settlements

The 3rd millennium BC appears to be a key period of development of the historical settlement landscape in ancient Egypt. After the unification of the country, the process of disappearance of the predynastic socio-political structures and settlement patterns associated with them significantly accelerated. Old chiefdoms, along with their centres and elites, declined and vanished. On the other hand, new settlements emerging in various parts of the country were often strictly related to the central authorities and formation of the new territorial administration. Not negligible were climatic changes, which influenced the shifting of the ecumene. Although these changes were evolutionary in their nature, some important stages may be recognized. According to data obtained during surveys and excavations, there are a number of sites that were considerably impoverished and/or abandoned before and at the beginning of the Old Kingdom. On the other hand, during the Third and Fourth Dynasties some important Egyptian settlements have emerged in the sources and begun their prosperity. Architectural remains as well as written sources indicate the growing interest of the state in the hierarchy of landscape elements and territorial structure of the country.

17O and 13C NMR spectra of some geminal diacetates

1988 ◽  
Vol 53 (3) ◽  
pp. 588-592 ◽  
Author(s):  
Antonín Lyčka ◽  
Josef Jirman ◽  
Jaroslav Holeček
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
The Other ◽  
13C Nmr Spectra ◽  
Other Hand ◽  
Carboxylic Esters ◽  
C Nmr ◽  
Oxygen Atoms

The 17O and 13C NMR spectra of eight geminal diacetates RCH(O(CO)CH3)2 derived from simple aldehydes have been measured. In contrast to the dicarboxylates R1R2E(O(CO)R3)2, where E = Si, Ge, or Sn, whose 17O NMR spectra only contain a single signal, and, on the other hand, in accordance with organic carboxylic esters, the 17O NMR spectra of the compound group studied always exhibit two well-resolved signals with the chemical shifts δ(17O) in the regions of 183-219 ppm and 369-381 ppm for the oxygen atoms in the groups C-O and C=O, respectively.

Avoiding Shame and Guilt

2018 ◽  
Author(s):  
C. Daniel Batson
Keyword(s):  
Empathic Concern ◽  
The Other ◽  
The Third ◽  
Helping Relationship ◽  
Shame And Guilt

After rejecting the remove–empathy hypothesis (Chapter 4), attention turned to the other two classic egoistic explanations for the motivation to help produced by empathic concern: empathy-specific punishment and empathy-specific reward. This chapter considers two kinds of empathy-specific punishment, shame and guilt. The shame hypothesis claims that we help more when we feel empathic concern because we’re motivated to avoid disapproval and censure from others. The guilt hypothesis says that we’re motivated to avoid self-condemnation for failing to do what we should. Contradicting the shame hypothesis, experiments revealed that even when no one else will know if participants fail to help, empathy still increased helping. Contradicting the guilt hypothesis, participants induced to feel empathy helped more even when provided a good excuse for not helping. Given that neither form of empathy-specific punishment could account for the empathy–helping relationship, our search shifted to the third classic egoistic explanation: pursuing pride.

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