An Overview of the Antimicrobial Properties of Lignocellulosic Materials

Pathogenic microbes are a major source of health and environmental problems, mostly due to their easy proliferation on most surfaces. Currently, new classes of antimicrobial agents are under development to prevent microbial adhesion and biofilm formation. However, they are mostly from synthetic origin and present several disadvantages. The use of natural biopolymers such as cellulose, hemicellulose, and lignin, derived from lignocellulosic materials as antimicrobial agents has a promising potential. Lignocellulosic materials are one of the most abundant natural materials from renewable sources, and they present attractive characteristics, such as low density and biodegradability, are low-cost, high availability, and environmentally friendly. This review aims to provide new insights into the current usage and potential of lignocellulosic materials (biopolymer and fibers) as antimicrobial materials, highlighting their future application as a novel drug-free antimicrobial polymer.     

Silsesquioxane Modified with PAMAM Dendrimer and a Bimetallic Complex for Electrochemical Detection of Ascorbic Acid

Octakis(3-chloropropyl)octasilsesquioxane (S) was organofunctionalized with the PAMAM Dendrimer G.0 (SPD). After functionalization, silsesquioxane interacts with copper chloride and subsequently with potassium hexacyanoferrate (III) to produce the structure CuHSPD. The silsesquioxane functionalized with the PAMAM dendrimer (SPD) and the obtained novel hybrid composite (CuHSPD) were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The CuHSP voltammogram showed two well-defined redox pairs with E^θ′= 0.27 and 0.74 V, that are assigned to the Cu^I/Cu^II and Fe^II(CN)₆/Fe^III(CN)₆ redox pairs, respectively. The graphite paste electrode containing CuHSPD allowed the electrocatalytic determination of ascorbic acid using various electrochemical techniques such as cyclic voltammetry, differential pulse voltammetry, and chronoamperometry.     

Rhenium and technetium complexes bearing quinazoline derivatives: progress towards a 99mTc biomarker for EGFR-TK imaging

The quinazoline derivatives (3-chloro-4-fluorophenyl)quinazoline-4,6-diamine (2) and (3-bromophenyl)quinazoline-4,6-diamine (3) were labelled with (99m)Tc using the "4 + 1" mixed-ligand system [Tc(NS3)(CN-R)] and the tricarbonyl moiety fac-[Tc(CO)3]+. In the "4 + 1" approach the technetium(iii) is stabilized by a monodentate isocyanide bearing a quinazoline fragment (L1,L2 ) and by the tetradentate tripodal ligand tris(2-mercaptoethyl)-amine (NS3). In the "4 + 1" approach, 99mTc-labelling was performed in a two-step procedure, the complexes [Tc(NS3)(L1)] (7a) and [Tc(NS3)(L2)] (8a) being obtained in about 50-70% yield. In the tricarbonyl approach, the fac-[Tc(CO)3]+ unit is anchored by two different monoanionic chelators bearing the quinazoline derivatives (3-chloro-4-fluorophenyl)quinazoline-4,6-diamine (2) and (3-bromophenyl)quinazoline-4,6-diamine (3). Both chelators have a N2O donor atom set, but one contains a pyrazolyl ring (L5H) and the other contains a pyridine unit (L6H). In both cases the conjugation of the quinazoline to the chelator was done through the secondary amine of the potentially tridentate and monoanionic chelators, the corresponding 99mTc-complexes (10a, 11a) being obtained in quantitative yield. The identities of the 99mTc-labelled quinazolines (7a, 8a, 10a, 11a) were confirmed by comparison with the HPLC profiles of the analogous Re compounds (7, 8, 10, 11). All these Re complexes were characterized by NMR and IR spectroscopy, elemental analysis and in some cases by MS and X-ray diffraction analysis. In vitro studies indicate that the quinazoline fragments, after conjugation to the cyano group (L1, L2) or to the pyrazolyl containing chelator (L5H), as well as the corresponding Re complexes (7, 8, 10) inhibit significantly the EGFR autophosphorylation and also inhibit A431 cell growth. These two effects were also found for the pyridine-containing chelator (L6H) and corresponding Re complex (11), although to a lesser extent.     

Enzyme flexibility and the catalytic mechanism of farnesyltransferase: targeting the relation

Farnesyltransferase enzyme (FTase) is an interesting target for anticancer therapy that has been the subject of particular attention over the past decade. However, despite of the thrilling achievements in the development of farnesyltransferase inhibitors (FTIs) over the past few years, the farnesylation mechanism remains, to some degree, a mystery. This work describes the application of molecular dynamics simulations to the study of enzyme flexibility in the 4 key intermediate states formed during the FTase catalytic mechanism--FTase resting state, binary complex (FTase-FPP), ternary complex (FTase-FPP-Peptide), and product complex (FTase-Product)--thereby covering the main states in the mechanistic pathway of this mysterious enzyme, while relating, dissecting, and exploring, in minute detail, the set of structural and dynamical changes taking place with FPP binding, peptide coordination and product formation. This study reveals the existence of a series of variational patterns involving the mechanistic events taking place at the active site of the enzyme, increasing in magnitude away from the active-site, demonstrating that relatively small-scale events such as substrate binding or product formation cause minor changes at the neighboring residues and corresponding helices, but ultimately induce much more dramatic effects on the more external regions of the enzyme.     

Application of non-isothermal cure kinetics on the interaction of poly(ethylene terephthalate) — Alkyd resin paints

Samples of paint (P), reused PET (PET-R) and paint/PET-R mixtures (PPET-R) were evaluated using DSC to verify their physical-chemical properties and thermal behavior. Films from paints and PPET-R are visually similar. It was possible to establish that the maximum amount of PET-R that can be added to paint without significantly altering its filming properties is 2%. The cure process (80–203°C) was identified through DSC curves. The kinetic parameters, activation energy (E _a) and Arrhenius parameters (A) for the samples containing 0.5 to 1% of PET-R, were calculated using the Flynn-Wall-Ozawa isoconversional method. It was observed that for greater amounts of PET-R added, there is a decrease in the E _a values for the cure process. A Kinetic compensation effect (KCE), represented by the equation InA=−2.70+0.31E _a was observed for all the samples. The most suitable kinetic model to describe this cure process is the autocatalytic Šesták-Berggreen, model applied to heterogeneous systems.     

The VUV electronic spectroscopy of acetone studied by synchrotron radiation

The electronic state spectroscopy of acetone (CH3)2CO has been investigated using high-resolution VUV photoabsorption spectroscopy in the energy range 3.7-10.8 eV. New vibronic structure has been observed, notably in the low energy absorption band assigned to the 1(1)A(1) --> 1(1)A2 (ny --> pi*) transition. The local absorption maximum at 7.85 eV has been tentatively attributed to the 4(1)A1 (pi --> pi*) transition. Six Rydberg series converging to the lowest ionisation energy (9.708 eV) have been assigned as well as a newly-resolved ns Rydberg series converging to the first ionic excited state (12.590 eV). Rydberg orbitals of each series have been classified according to the magnitude of the quantum defect (delta) and are extended to higher quantum numbers than in the previous analyses.     

Bi-Lipschitz geometry of weighted homogeneous surface singularities

We show that a weighted homogeneous complex surface singularity is metrically conical (i.e., bi-Lipschitz equivalent to a metric cone) only if its two lowest weights are equal. We also give an example of a pair of weighted homogeneous complex surface singularities that are topologically equivalent but not bi-Lipschitz equivalent. L. Birbrair was supported under CNPq grant no. 300985/93-2. A. Fernandes was supported under CNPq grant no. 300393/2005-9. W. D. Neumann was supported under NSA grant H98230-06-1-011 and NSF grant no. DMS-0206464.     

1H and 13C NMR signal assignments of some new spiro[7H-benzo[de]anthracene-naphthopyrans

The complete 1H and 13C NMR signal assignment of four new photochromic spiro[7H-benzo[de]anthracene-naphthopyrans] was achieved using one- and two-dimensional methods (DEPT, COSY, HSQC, HMBC, NOESY).     

Chemical composition of tomato seeds affected by conventional and organic production systems

Tomato is amongst the most consumed vegetables in the world, not only for its culinary versatility but also for its high nutritional value. In the last years, consumers have shown an increased concern regarding food origin and safety. The organic tomato production has been a promising alternative for the consumer offering a safer food in relation to environmental, social and nutritional aspects. This study assessed the chemical composition of tomato seeds produced in both conventional and organic systems by INAA. The results showed significant differences (p≤0.05) in the mass fractions of Br, Cs, Eu, Fe, K, Mo, Na, Rb and Sm between both systems, indicating influence of the crop management adopted in the different tomato production systems.     

Chemical characterization of agricultural supplies applied to organic tomato cultivation

The agricultural supplies used in the organic system to control pests and diseases as well as to fertilize soil are claimed to be beneficial to plants and innocuous to human health and to the environment. The chemical composition of six agricultural supplies commonly used in the organic tomato culture, was evaluated by instrumental neutron activation analysis (INAA). Results were compared to the maximum limits established by the Environment Control Agency of the São Paulo State (CETESB) and the Guidelines for Organic Quality Standard of Instituto Biodinâmico (IBD). Concentrations above reference values were found for Co, Cr and Zn in compost, Cr and Zn in cattle manure and Zn in rice bran.