Molecular characterization of papaya genotypes using AFLP markers

Due to the low genetic variability reported in the commercial plantations of papaya (Carica papaya L.), the objective of this study was analyze the genetic diversity of 32 genotypes including cultivars, landraces, inbred lines, and improved germplasm using the AFLP technique (Amplified Fragment Length Polymorphism). The genetic distance matrix was obtained using the Nei and Li genetic distance and clustering was performed using the unweighted pair-method with arithmetic mean (UPGMA). Using 11 combinations of EcoRI/MseI primers, 383 polymorphic bands were obtained. On average, 34.8 polymorphic bands were obtained per primer combination. Five clusters were formed. The traditional cultivar 'Sunrise' and the inbred line CMF-L30-08 were the closest genotypes, and the improved germplasm (CMF041) and landrace (CMF233) the most distant. The main papaya cultivars commercially grown in Brazil, as well as four inbred lines and three improved germplasm, were clustered together, however, were not grouped in the same branch. The genetic distance between the Sunrise and Golden cultivars was 0.329, and even arising from mutation and selection within the Sunrise variety, the Golden stores considerable genetic variability. Additional variability was observed in the inbred lines derived from papaya breeding program at Embrapa Cassava and Fruits.

O uso de cálculos teóricos como ferramenta para a detecção de moléculas no meio interestelar: o caso dos carbenos CnNH (n=1, 3 e 5)

This work reviews some applications of ab initio molecular orbital calculations to the elucidation of structures of interstellar molecules. The case of the CnNH (n=1, 3 and 5 ) carbenes is extensively analyzed and discussed. Theoretical conformational analysis and predicted values for the rotational constants and dipole moments of the singlet state of C5NH are reported for the first time and a comparison is performed with results previously obtained for C3NH and CNH.

Excitação eletrônica das moléculas de metacrilato de metila e estireno na região do ultravioleta de vácuo

Angle-resolved electron energy-loss spectra have been measured for the methyl methacrylate (MMA) and styrene molecules in the 0 - 50 eV energy range. The spectra have been obtained at 1 keV incident energy, with an energy resolution of 0.8 eV and covering an angular range of 2.0 to 7.0 degrees. Within our knowledge, this is the first gas-phase excitation spectrum for MMA and styrene in this energy range. The spectra of MMA at small scattering angles are dominated by an intense peak at 6.7 eV followed by a broad band centered at about 16 eV. In the case of styrene, six bands can be observed in the spectra. Based on the angular behaviour of the excitation spectra of these molecules, the low-lying peaks observed are considered to be associated predominantly with dipole-allowed processes. In both cases, new bands can be observed for excitation energies greater than 20 eV. This could be associated with dipole-forbidden transitions to shake-up and doubly-excited states.

Isolamento e caracterização de acil-tiossemicarbazidas como intermediários na síntese de compostos mesoiônicos

1,3,4-thiadiazolium-2-aminides and their isomers 1,3,4-triazolium-2-thiolates have been synthesized via anhydroacylation reactions. This work presents a study by infrared monitoring of the reaction between substituted aroyl acid chlorides and 1,4-diphenylthiosemcarbazide. The intermediates and products were isolated, purified and charaterized by IR and 13C NMR spectroscopy. The increasing or decreasing in intensity of characteristic stretching bands indicated the rate dependence on the electronic nature of substituents. The results also demonstrate that 1,3,4-triazolium-2-thiolates are obtained in anhydrous conditions whereas presence of water leads to a mixture of the isomers.

Calibração multivariada para sistemas com bandas sobrepostas através da análise da fatores do tipo Q

A multivariate calibration method to determine chemical compositions of systems with severely overlapped bands is proposed. Q mode factors are determined from the spectral data and subsequently rotated using the varimax and oblique transformation of Imbrie. The method is applied to two sets of simulated data to test the sensitivity of analytical results to random experimental error. The chemical concentrations of alanine and threonine mixture are determined from spectral data of the 302,5 - 548,5 nm region.

Borohidreto complexos de cobre (I) contendo difosfinas: caracterização espectroscópica e comportamento térmico

Tetrahydroborate complexes of copper (I) with bidentate phosphines, [Cu(eta²-BH4)(dppm)] (1), [Cu(eta²-BH4)(dppe)] (2), [Cu(eta²-BH4)(cis-dppet)] (3) and [Cu(eta²-BH4)(dppb)] (4) (dppm = bis(diphenylphosphino)methane; dppe = 1,2-bis(diphenylphosphino) ethane; cis-dppet = 1,2-cis(diphenylphosphino)ethene; dppb = 1,4-bis(diphenylphosphino)butane) were prepared and characterized by elemental analysis, infrared spectroscopy, NMR and thermogravimetric analysis. The IR data for 1-4 showed bands typical of a bidentate coordination of BH4 group to the copper atom and the 31P{¹H} NMR spectra indicated that the phosphorous atoms are chelating the metal centre. The thermal behavior of the compounds was investigated and suggested that their thermal stability is influenced by the phosphines. Their thermal stability decreased as follows: [Cu(eta²-BH4)(dppe)] (2) > [Cu(eta²-BH4)(dppm)] (1) > [Cu(eta²-BH4)(dppb)] (4) > [Cu(eta²-BH4)(cis-dppet)] (3). According to thermal analysis and X-ray diffraction patterns all compounds decomposed giving Cu(BO2)2, CuO, CuO2 and Cu as final products.

Espectroscopia vibracional: sistemática para o cálculo dos estiramentos CO de complexos carbonílicos e determinação da sua atividade IV e Raman

IR bands related to M-C stretchings are not diagnostically significant for the identification of carbonyl groups in the spectra of carbonyl complexes. Otherwise, the frequency, intensity and number of bands for the CO stretchings provide very useful informations about the number of CO ligands and many others structural proprieties, like the presence of bridged CO groups. We report about a relatively simple and useful method for the determination of the CO stretchings of carbonyl complexes, which considers only the bond stretching internal coordinates of the CO groups.

Preparação e caracterização do complexo cobaloxima e sua utilização na construção de um eletrodo modificado: um experimento eletroquímico no curso de graduação

The present experiment describes the preparation, characterization of n-butyl(pyridil)cobaloxime complex and its electrochemical property. The infrared and uv-visible absorption spectra were used to characterize the complex obtained. The infrared spectrum of the compound showed characteristics bands that indicated the formation of the Co-C chemical bond formation. The electronic absorption spectrum in acetonitrile showed transition bands attributed to p-p*, metal-to-ligand charge transfer, d-d transitions and charge transfer Co-C. The electrochemical property was investigated by the pulse differential voltammetry technique. Two oxidation processes: Co(I)/Co(II) at -423 mV and Co(II)/Co(III) at 752 mV were observed.

Modelos para dispersão Raman em polímeros conjugados

Raman dispersion refers to the dependence of the position of Raman bands on the energy of the exciting radiation. In this work, the three main models currently used to explain this phenomenon (Conjugated Length Model, Amplitude Mode Model and Effective Conjugation Coordinate Model) are discussed. Raman dispersion is a consequence of pi electron delocalization, but each model describes in a different way how pi electron delocalization affects the position of Raman bands. Here the features, qualities and problems of the three models are highlighted.

Hemes férricos pentacoordenados e hexacoordenados dos monômeros d nativo e reconstituído da hemoglobina extracelular de Glossoscolex paulistus: estudos espectroscópicos em meio ácido

UV-Vis and fluorescence spectroscopic studies of the native and reconstituted d monomers of Glossoscolex paulistus were performed in acid medium. The coexistence of distinct species shows the complexity of the equilibria. Besides the hexacoordinate low spin hemichrome, with bands at 535 and 565 nm, a pentacoordinate high spin hemichrome is identified by the blue-shifted low intensity Soret band (371 nm) and the LMCT band (643 nm). The pentacoordinate hemichrome must be related to the partial unfolding of the polypeptide.

Da cor à cor inexistente: uma reflexão sobre espectros eletrônicos e efeitos cromáticos

Inexistent colors have been the inspiring theme of investigation by Israel Pedrosa, a Brazilian artist, who has devoted his life to creative painting, exploiting the chemical and physical effects associated with light, especially those generated in the light refraction domain. In this article, by focusing on the electronic spectra of phthalocyanines and gold nanoparticles, we discuss how such effects can influence the spectroscopic measurements, leading to inexistent bands and transitions.

Preparação e caracterização óptica de filmes de poli(estireno sulfonados) dopados com neodímio

In this work we describe the processing of poly(styrene sulphonate) films (PSS) doped with neodymium (Nd). Optical density measurements in the UV-Vis-NIR region show the typical bands observed for neodymium chloride (NdCl3) in solution. In the case of films, the intensity ratio between the peaks at 800 nm (4I9/2 -> 4F5/2 + ²H7/2) and 580 nm (4I9/2 -> 4G5/2 + ²G7/2) is equal to 0.83. Infrared spectra present an enhancement in the absorption region of aromatic rings. Site selective luminescence spectroscopy shows that the incorporation of Nd introduces a hipsochromic shift and a line shape definition in UV luminescence compared to PSS film, decreasing the interaction between aromatic groups. In addition, the film exhibits an intense radiative transition at 1061 nm (4F3/2->4I11/2), comparable to the one present in crystalline materials doped with Nd.

Atropoisomerismo: o efeito da quiralidade axial em substâncias bioativas

Atropisomerism is a special kind of stereoisomeric relationship that arises from the freezing of a certain conformation of an organic molecule, associated with a high rotational barrier about a single covalent bond. Atropisomerism has been originally described in orto-functionalyzed biphenyl derivatives, but a lot of other organic functionalities can present this structural phenomenon, characterized by the presence of chiral properties in compounds that don't present classical stereogenic centers. Atropisomeric compounds, intermediates and catalysts have well-know importance in organic synthesis, but the influence of the axial chirality in substances able to modulate biological systems is still not very exploited in drug design and development. In this context, the present account describes the importance of this structural property in the medicinal chemistry of different classes of bioactive compounds or therapeutic agents, emphasizing how atropisomerism could affect the molecular recognition of a ligand or a prototype by the target bioreceptor.

Preparation, spectroscopic and acidity properties of two hydrazones: an organic lab experiment

An undergraduate organic lab experiment is described based on the preparation of two readily accessible hydrazones. The UV-visible spectra of these N-H acids and of their conjugate bases are employed to illustrate the importance of through-conjugation in determining their acid strength and their internal charge-transfer-band transitions.

Um estudo teórico relativo à não-linearidade da ligação de hidrogênio em sistemas heterocíclicos C2H4O-C2H2 e C2H4S-C2H2

B3LYP/6-31G(d,p) calculations were used to determine the optimized geometries of the C2H4O-C2H2 and C2H4S-C2H2 heterocyclic hydrogen-bonded complexes. Results of structural, rotational, electronic and vibrational parameters indicate that the hydrogen bonding is non-linear due to the pi bond of the acetylene interacting with the hydrogen atoms of the methyl groups of the three-membered rings. Moreover, the theoretical investigation showed that the non-linearity is much more intriguing, since there is a structural disjunction on the acetylene within the heterocyclic system.