Elon Lages Lima,Fundamental groups and Covering space

Rendiconti del Circolo Matematico di Palermo Series 2 -     

Theoretical investigation of the intermolecular H-bonding and proton transfer in cytosine assisted by water and methanol

Abstract  

This investigation is devoted to study of the electronic structure of several H-bonded complexes of cytosine tautomers with water and methanol. The stability of these “supersystems” (aggregates) was estimated by calculating the bonding energies ΔE and ΔE _b. The energy barriers of water/methanol-assisted tautomeric conversions were calculated (intermolecular proton transfer), and the electronic structures of the transition states were studied. Each transition state of the proton-transfer reaction was determined as a first-order saddle point on the potential energy surface (full coordinate hyperspace). The crystal structure of the tetramer of cytosine monohydrate was also investigated. It was found that this structure is close to a conical intersection.     

Détermination de la vitamine B1 (thiamine) au moyen du picrolonate de lithium

Résumé On a élaboré une méthode de détermination de la vitamine B₁ au moyen de picrolonate de lithium. La vitamine B₁ est précipitée par le picrolonate de lithium.Le précipité de picrolonate de thiamine est éliminé par filtrage au moyen d'un microfiltre de Schott. L'excès de picrolonate de lithium est titré au moyen de bleu de méthylène. On titre aussi dos essais à blanc de picrolonate de lithium.Les autres vitamines ne gênent pas la détermination. Seuls gênent les métaux lourds, alcalino-terreux et les amines.L'erreur relative moyenne de la méthode est de 3,25%.La méthode de détermination de la vitamine B₁ au moyen de picrolonate de lithium peut être utilisée avantageusement pour analyser une nombre de matières et de préparations pharmaceutiques comportant la dite vitamine.

---

Summary A method of determining vitamin B₁ by means of lithium picrolonate has been worked out. The B₁ vitamin is precipitated by the lithium picrolonate. The precipitate of the picrolonate of thiamine is removed by filtering through a Schott microfilter. The excess of lithium picrolonate is titrated with methylene blue. Blanks of lithium picrolonate are likewise titrated.The other vitamins do not interfere in this determination. The only interfering materials are the heavy metals, the alkaline earths and the amines.The mean relative error of the method is 3.25%.The method of determining vitamin B₁ by means of lithium picrolonate may be used to advantage in the analysis of a number of materials and pharmaceutical preparations.

---

Zusammenfassung Eine Methode zur Bestimmung von Vitamin B₁ mit Lithiumpikrolonat wurde ausgearbeitet. B₁ wird damit gefällt, das Thiaminpikrolonat abfiltriert und der Überschuß des Fällungsmittels mit Methylenblau titriert. Außerdem wird ein Leerversuch mit Lithiumpikrolonat ausgeführt.Die anderen Vitamine stören die Bestimmung nicht, aber die Schwermetalle, die alkalischen Erden und Amine.Der mittlere Fehler der Methode beträgt 3,25%.Das Verfahren eignet sich zur Analyse pharmazeutischer Produkte und Zubereitungen.

     

Equilibrium Configurations of Lipid Bilayer Membranes and Carbon Nanostructures

The present article concerns the continuum modelling of the mechanical behaviour and equilibrium shapes of two types of nano-scale objects: fluid lipid bilayer membranes and carbon nanostructures. A unified continuum model is used to handle four different case studies. Two of them consist in representing in analytic form cylindrical and axisymmetric equilibrium configurations of single-wall carbon nanotubes and fluid lipid bilayer membranes subjected to uniform hydrostatic pressure. The third one is concerned with determination of possible shapes of junctions between a single-wall carbon nanotube and a flat graphene sheet or another single-wall carbon nanotube. The last one deals with the mechanical behaviour of closed fluid lipid bilayer membranes (vesicles) adhering onto a flat homogeneous rigid substrate subjected to micro-injection and uniform hydrostatic pressure.     

Identification microcristalloscopique de la Vitamine B1 au moyen d'acide picrolonique

Résumé On propose une réaction microcristalloscopique pour l'identification de la vitamine B₁ au moyen d'acide picrolonique. On observe au microscope, au grossissement de 400×, des cristaux en éventail, dont les deux bouts sont recourbés en forme d'hélice. Les cristaux ayant un faciès spécifique, la réaction est strictement spécifique pour la vitamine B₁ seulement. Les autres vitamines B ne réagissent pas avec l'acide picrolonique. La sensibilité de la réaction est de 0,0062g/l. Limite de dilution 1150000.On a déterminé les relations molaires de la réaction selon la méthode des séries isomolaires et par analyse du composé obtenu. La thiamine et l'acide picrolonique réagissent dans les rapports molaires de l'ordre de 11. On obtient le sel: le picrolonate de thiamine.

---

Summary A microcrystalloscopic reaction is proposed for the identification of vitamin B₁ employing picrolonic acid. At a magnification of 400×, the microscope reveals fan-shaped crystals, whose two ends are bent back in a helical form. The crystals have a specific form and consequently the reaction is strictly specific for vitamin B₁ only. The other B vitamins do not react with picrolonic acid. The sensitivity of the reaction is 0.0062g/l. The dilution limit is 1150000.The molar relation of the reaction was determined by the method of isomolar series and by the analysis of the compound obtained. Thiamin and picrolonic acid react in the molar ratios of the order 11. The salt, the picrolonate of thiamin, is obtained.

---

Zusammenfassung Eine Kristallfällunggreaktion zur Identifizierung von Vitamin B₁ mit Pikrolonsäure wird vorgeschlagen. Bei 400facher Vergrößerung beobachtet man unter dem Mikroskop fächerförmige Kristalle, die beiderseits schneckenförmig gebogen sind. Sie haben einen charakteristischen Habitus, die Reaktion ist für Vitamin B₁ streng spezifisch. Die anderen Vitamine der B-Gruppe reagieren nicht mit Pikrolonsäure. Die Empfindlichkeit der Reaktion beträgt 6,2 pg/l, die Grenzkonzentration 1150000.Nach der Methode vonJob und durch Analyse des Reaktionsproduktes wurde das Molverhältnis bestimmt. Thiamin und Pikrolonsäure reagieren im Verhältnis 11, wobei Thiaminpikrolonat entsteht.

---

---

Collaborateurs techniques:B. Banev etCh. Droumeva.     

A Novel Nitrone Cycloaddition/Rearrangement

Adamantanone-derived nitrone 4 and some other keto-nitrones, when reacted with aromatic and aliphatic aldehydes in refluxing toluene or tetrahydrofuran, formed the corresponding aldonitrones (Z)- 10 , the latter arising from the fragmentation of an initially formed 1 , 4 , 2 -dioxazolidine 6 to adamantan-2-one and an oxaziridine intermediate 11 , which then rearranges to (Z)- 10 .     

Drug-induced modifications of the immune response part 94-(Arylamino)-2,5-dihydro-2-oxo-N-(trans-2-phenylcycolopropyl)furan-3-carboxamides as Novel Antiallergic Compounds

The synthesis and antiallergic activity of a series of 4-(arylamino)-2,5-dihydro-2-oxo-N-(trans-2-phenyl-cyclopropyl)furan-3-carboxamides 10 are described. Treatment of N-substituted 2-amino-4,5-dihydro-4-oxofuran-3-carboxylic acids 9 with chlorooxobis(2-oxo-1,3-oxazolidin-3-yl)phosphorus ( 2 ) and an appropriate aromatic amine in the presence of Et₃N, resulted in a novel 3(2H)-furanone-→2(5H)-furanone rearrangement that led to the facile preparation of the new amides 10 . The latter exerted a potent antiallergic activity when tested in the dermal vascular permeability and active anaphylaxis assays in rats. The most active compound 10b inhibited the action of serotonin, histamine, and bradykinin by 94, 92, and 100%, respectively, when administered intraperitoneally to rats at doses of 100 mg/kg. The present series of 10 represents a novel class of antiallergic agents.     

Electron and Geometry Structure of Hydrogen-Bonded Complexes of Guanine with One Molecule Methanol. A DFT Level Study

Summary. The geometries, harmonic vibrational frequencies, and energies of eight hydrogen-bonded complexes of guanine with one molecule methanol are computed using the DFT (B3LYP) method together with the 6-31+G* basis functions. In the investigation two stable tautomers of guanine (oxo-amino N9H and oxo-amino N7H) were chosen. They were included in a variety of H-bonded complexes with one molecule methanol. In order to investigate the nature of the intermolecular bonds, the bonding energies and thermodynamic properties of the complexes were calculated.     

Hydrogen Bonded Complexes of Acetylacetone and Methanol: HF and DFT level Study

Several possible hydrogen-bonded complexes between the tautomeric forms of acetylacetone and methanol were studied by ab initio methods using 6-311G** and D95** basis functions at the HF and DFT (B3LYP) levels of theory. The calculations were carried out for isolated molecules and solvent assisted complexes by means of the isodensity polarized model (IPCM). The theoretical frequencies were compared with the experimental IR spectrum of an equimolar mixture of acetylacetone and methanol. It was proved that the most stable H-bonded complex acetylacetone–methanol is formed between O-bonded methanol- and the enol molecule.