Navegando por Assunto "Espectroscopia"

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Acesso aberto (Open Access)
Biologically active polyketides produced by Penicillium janthinellum isolated as an endophytic fungus from fruits of Melia azedarach
(2005-04) MARINHO, Andrey Moacir do Rosário; RODRIGUES FILHO, Edson; MOITINHO, Maria da Luz Ribeiro; SANTOS, Lourivaldo da Silva
Penicillium janthinellum, isolated as an endophytic fungus from fruits of Melia azedarach, was cultivated over 20 days on ground and autoclaved white corn, where the known polyketides citrinin, emodin, 1,6,8-trihydroxy-3-hydroxymethylanthraquinone, and a new modified anthraquinone, named janthinone, were produced and isolated by classical chromatographic procedures and identified by MS and 1D and 2D NMR spectroscopic data. The antibacterial properties of these polyketides were investigated. Citrinin inhibited 100% of Leishmania growth after 48h at a concentration of 40 μg mL-1.
Acesso aberto (Open Access)
Crescimento e caracterização dos cristais de sulfato de níquel hexahidratado dopados com íons [MnH2O]2+ e com sulfato de magnésio heptahidratado
(Universidade Federal do Pará, 2011) FERREIRA JÚNIOR, Messias de Nazaré Guimarães; REMÉDIOS, Cláudio Márcio Rocha; http://lattes.cnpq.br/7146076994037490
In this work, manganese ions doped nickel sulphate crystals (NSH:Mn) and magnesium ion doped nickel sulphate crystals (NMgSH) were grown and later characterized by X-ray diffraction and Raman spectroscopy techniques. The results obtained showed that the doped crystals possess a structure very similar to that of the pure nickel sulphate crystal (NSH), with an anisotropic deformation in the unit cell dimensions compared to the pure crystal, undergoing expansion in unit. The aim of the present study was to grow two new single crystals of good optical quality to be used as optical bandpass filters. Nickel sulfate hexahydrate (NHS) crystals are known to possess an optical transmission spectrum which has attracted much attention because it presents two regions with high transmission efficiency of approximately 80%, the first region being between 200 and 350 nm and the second between 400 and 600 nm, and a high absorption efficiency in other regions of the UV-VIS spectrum. A light transmission spectrum with these characteristics is similar to an optical filter. Termogravimetric (TGA) analyses were carried out for pure and doped crystals. The obtained decomposition temperature of NSH was found to be 73 °C while that NSH: Mn and NMgSH crystals present values of 82 ° C and 86 C respectively. As can be easily perceived, the thermal stability of crystals with Mn or Mg ions in their structures is significantly higher. The transmission band between 200 and 350 nm in the optical spectrum of NSH was found to be narrower in the transmission spectrum of the doped crystal thus restricting the region of the spectrum known as UVA.
Acesso aberto (Open Access)
Espectrometria Raman, UV, DOS e Circular Dicroísmo de alcalóides do cigarro
(Universidade Federal do Pará, 2011-02-28) GUEDES, Alberto Monteiro; CHAVES NETO, Antonio Maia de Jesus; http://lattes.cnpq.br/3507474637884699
This work is about spectroscopic analysis of some molecular structures present in tobacco (Nicotiana glauca), the base for cigarette, and their interactions with the DNA molecule. According to its importance, among the variety present in the cigarette, the molecules studied were derived from nicotinic acid, nicotinic acid (niacin / vitamin B3), nicotinamide, trigonelline, nicotine, nornicotine and anabasine. The optimizations of these structures were initially obtained in the Hyperchem 7.5 computational software based on the theory of molecular mechanics. Then, they were optimized using the method Density Functional Theory, on the basis B3LYP/ 6-311 + + G (d, p), simulated in software Gaussian 03. Once the optimized structures, we obtained the UV absorption, Raman, Infrared, Circular Dichroism and Density of States spectra using Time-Dependent Density Functional Theory also simulated the in the same software. At the end of this process was also simulated, via molecular mechanics, the interactions of these structures with the DNA molecule in order to verify the potential carcinogenic or not these substances.
Acesso aberto (Open Access)
Estudo de solvatocromismo em líquidos moleculares orgânicos via método seqüencial Monte Carlo/Mecânica Quântica
(Universidade Federal do Pará, 2007-03) MARTINS, Hardiney dos Santos; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
The Sequential Monte Carlo / Quantum Mechanical method was applied to study the solvatochromic shifts and the dipole moments for organic molecules: Uracil in water, - carotene in oleic acid, ricinoleic acid in methanol and in ethanol and oleic acid in methanol and in ethanol. The optimizations and charges distributions had found by Density Functional Theory through the B3LYP functional and sets basis functions 6-31G(d) to all molecules except water and Uracil, whose was applied the sets basis functions 6-311++G(d,p). In the classical approach, Monte Carlo, was applied the algorithm Metropólis through the DICE program. The sampling of statistically relevant configurations to averaged calculations of the properties was used with auto-correlation function performed to each system. The Radial Distribution Function of the molecular liquids was applied to separate the first shell solvation for each system, which gives the main interaction between solute-solvent. The statistically relevant configurations of the first shell of solvation of the each system were subject a quantum mechanical calculations at the semi-empiric level with the method ZINDO/S-CI. The absorptions spectrum had found to solutes in gas phase and to the systems of molecular liquids spoken. The electric dipole moments of these were also found. All the bands of spectrum absorptions had a blue shift, except the second band of the -carotene in oleic acid that was a red shift. The results found have a very good agreement with the values found in the literature. All the system had increase in the electric dipole moments because the solvents molecules are polar molecules. The system of fatty acids in alcohols had results very similar, in other words, the fatty acids mentioned had characteristics spectroscopic similar submitted to same solvents. The simulations whose with Sequential Monte Carlo / Quantum Mechanical method were studied show the methodology is effective to find the spectroscopic proprieties of molecular liquids analyzed.
Acesso aberto (Open Access)
Investigação espectroscópica dos carbonilos heterobimetálicos cis-[Fe(CO)4(HgX)2], X = Cl, Br, I
(1999-12) ZAMIAN, José Roberto; MAURO, Antônio Eduardo; NOGUEIRA, Vânia Martins
Spectroscopic studies of heterobimetallic carbonyls cis-[Fe(CO)4(Hgx)2], X=Cl, Br, I.The series of compounds cis-[Fe(CO)4(HgX)2], X=Cl,Br, I shows an octahedral geometry around the iron atom with the two HgX groups cis to each other. In this paper the assignment for the carbonyl stretching modes and the calculation of their force constants were performed on the basis of the Cotton-Krainhanzel model. Taking into account all the data from the IR, 199Hg NMR and UV-vis spectra it is possible to verify the influence of X on the electronic densities at the metallic centers.
Acesso aberto (Open Access)
Thermal decomposition and stability in a series of heterobimetallic carbonyl compounds of the type [Fe(CO)4(HgX)2] (X=Cl, Br, I)
(2000) ZAMIAN, José Roberto; MAURO, Antônio Eduardo; NUNES, Carolina Coimbra; ALMEIDA, Eduardo Tonon de
Foram preparados compostos carbonílicos heterobimetálicos do tipo [Fe(CO)4(HgX)2] ( X= Cl, Br, I), contendo ligação metal-metal, objetivando investigar suas estabilidades térmicas em função do halogênio coordenado aos átomos de mercúrio. A caracterização destes complexos foi feita usando-se de técnicas espectroscópicas de infravermelho e ressonância magnética nuclear, além de análise elementar. O produto final das termodecomposições foi identificado através de espectroscopia no infravermelho e difratograma de raios-X, método de pó.