Molecular recognition of guanosine and 2-acetylaminofluorene-modified guanosine. A comparative study

Abstract

The ability of an abiotic receptor, 7-acetylamino-2-methyl–1,8-naphthyridine, to bind to guanosine was analysed by a combination of NMR determinations and molecular modeling studies. The results indicate that this receptor simulates the base-pairing properties of cytidine in its Watson-Crick interaction with guanosine. Binding of the same receptor to N-(guanosin-8-yl)-2-acetylaminofluorene, the guanosine adduct containing the carcinogen 2-acetylaminofluorene, was found to occur in a similar manner. The calculated binding energies show that the molecular recognition of the adduct is lower than that of the unmodified guanosine. The theoretical studies suggest that the predominance of an abnormal low energy syn conformation for the adduct is the main structural feature accounting for the observed decrease of the host-guest interaction.     

Thermoanalytical and phytochemical study of the cupuassu (Theobroma grandiflorum Schum.) seed by-product in different processing stages

Journal of Thermal Analysis and Calorimetry - Cupuassu (Theobroma grandiflorum Schum.) is a typical Amazonian fruit, whose seed is used as raw material to produce cupulate. The by-product of its...     

Chemistry Platform for the Ultrafast Continuous Synthesis of High-Quality III–V Quantum Dots

A chemistry platform for the fast continuous synthesis of III–V quantum dots is demonstrated. III-nitride QDs are prepared by using short residence times (less than 30 s) in a one-step continuous process with supercritical solvents. GaN QDs prepared via this route exhibit strong UV photoluminescence with a structuring of the emission signal at low temperature (5 K), confirming their high quality. An example of metal site substitution is given with the synthesis of In_xGa_1-xN solid solution. A continuous bandgap shift towards lower energies is demonstrated when increasing the indium content with strong photoluminescence signals from UV to visible. The chemistry platform proposed could be easily extrapolated to binary and ternary III phosphides or arsenides with the homologous V source.     

Characterization of PE-g-HEMA films prepared by gamma irradiation through nuclear microprobe techniques

PE-g-HEMA films with different grafting yields prepared by mutual gamma irradiation method at a ⁶⁰Co source were characterized with ion beam analytical techniques using a nuclear microprobe. Qualitative analysis showed a random and heterogeneous distribution of contaminant elements, independent of the grafting degree, suggesting the existence of several sources of contamination at different stages of their preparation. Results also suggest that this “phased” contamination occurs simultaneously with mechanisms of agglomeration/entrapment of impurities during the gamma induced copolymerization reaction. Moreover, quantitative data showed that all contaminants found in the copolymeric films are natural contaminants of their reagents of preparation, although at concentrations without toxicological hazard, which points to a low cytotoxic potential.     

Laser remelting of Al-1.5 wt%Fe alloy surfaces: Numerical and experimental analyses

A 3D heat transfer mathematical model based on the finite element method is applied to the laser surface remelting (LSR) process with a view to simulating temperature fields and melt pool dimensions. The theoretical predictions furnished by the model are validated against LSR experimental results from tests carried out in the present study with Al-1.5 wt%Fe alloy samples. The work also encompasses an analysis of microstructural and microhardness variations throughout the resulting treated and untreated zones. A remarkable effect of the LSR treatment on the mechanical and corrosion resistance of the treated samples is shown.     

Analysis of thick isotropic and cross-ply laminated plates by radial basis functions and a Unified Formulation

In this paper, we combine Carrera's Unified Formulation and a radial basis function collocation technique for predicting the static deformations and free vibration behavior of thin and thick isotropic and cross-ply laminated plates. Through numerical experiments, the capability and efficiency of this collocation technique for static and vibration problems are demonstrated, and the numerical accuracy and convergence are thoughtfully examined.