CHEMILUMINESCENCE FROM THE OXIDATION OF AUXIN DERIVATIVES

Abstract— The thiophenyl ester of indole-3-acetic acid and indole-3-acetonitrile produce chemiluminescence in aerated dimethylsulfoxide in the presence of potassium t -butoxide. The emitter is the aromatic aldehyde. In the case of acetonitrile, the other product expected from the cleavage of an intermediate dioxetane, cyanate/isocyanate, has also been identified. Other auxins also chemiluminesce under similar conditions, but the emitters have not been properly identified.
These systems are models for the peroxidase catalyzed oxidation of indole-3-acetic acid to indole-3-carboxaldehyde and as such support the earlier inference (Vidigal et al , 1975) that the excited aldehyde is generated in the enzymic process.
An additional result is the observation of an exciplex between excited indole-3-carboxaldehyde and the thiophenylester of indole-3-acetic acid. This appears to be the first case of chemical generation of an exciplex by a route other than radical ion reaction, presumably by the dioxetane route.     

Models for the modern power grid

This article reviews different kinds of models for the electric power grid that can be used to understand the modern power system, the smart grid. From the physical network to abstract energy markets, we identify in the literature different aspects that co-determine the spatio-temporal multilayer dynamics of power system. We start our review by showing how the generation, transmission and distribution characteristics of the traditional power grids are already subject to complex behaviour appearing as a result of the the interplay between dynamics of the nodes and topology, namely synchronisation and cascade effects. When dealing with smart grids, the system complexity increases even more: on top of the physical network of power lines and controllable sources of electricity, the modernisation brings information networks, renewable intermittent generation, market liberalisation, prosumers, among other aspects. In this case, we forecast a dynamical co-evolution of the smart grid and other kind of networked systems that cannot be understood isolated. This review compiles recent results that model electric power grids as complex systems, going beyond pure technological aspects. From this perspective, we then indicate possible ways to incorporate the diverse co-evolving systems into the smart grid model using, for example, network theory and multi-agent simulation.     

Efficiency and sustainability assessment for a group of farmers in the Brazilian Amazon

The aim of this paper is to use DEA models to evaluate sustainability in agriculture. Several variables are taken into account and the resulting efficiency is measured by comparison. The performance of family farms is analysed here (variables: farmed area, work force, and production). As agricultural sustainability depends on the maintenance of systems of production for long periods of time, the models were run for the years of 1986 and 2002. Tiered DEA models were used to group farmers in sustainability categories. Non-parametric regression models were used to identify the factors affecting the efficiency measurements. All the results indicate that the majority of the farmers increased their efficiency along the time. These improvements may support the existence of sustainability.     

Chemical composition and antibacterial activity of the essential oil of Espeletia nana

The essential oil of the leaves of Espeletia nana Cuatrec., obtained by hydrodistillation, was analyzed by GC-MS, which allowed the identification of 24 components, which made up 99.9% of the oil. The most abundant compounds were a-pinene (38.1%), beta-pinene (17.2%), myrcene (15.0%), spathulenol (4.2%), bicyclogermacrene (4.0%), a-zingiberene (4.0%), and gamma-himachalene (3.7%). Antibacterial activity was tested against Gram-positive and Gram-negative bacteria using the agar disk diffusion method. Activity was observed only against Gram-positive bacteria. MIC values were determined for Staphylococcus aureus ATCC 25923 (200 microg/mL) and Enterococcusfaecalis ATCC 29212 (600 microg/mL).     

p53‐Dependent and p53‐Independent Responses of Cells Challenged by Photosensitization

The p53 protein exerts fundamental roles in cell responses to a variety of stress stimuli. It has clear roles in controlling cell cycle, triggering apoptosis, activating autophagy and modulating DNA damage response. Little is known about the role of p53 in autophagy‐associated cell death, which can be induced by photoactivation of photosensitizers within cells. The photosensitizer 1,9‐dimethyl methylene blue (DMMB) within nanomolar concentration regimes has specific intracellular targets (mitochondria and lysosomes), photoinducing a typical scenario of cell death with autophagy. Importantly, in consequence of its subcellular localization, photoactive DMMB induces selective damage to mitochondrial DNA, saving nuclear DNA. By challenging cells having different p53 protein levels, we investigated whether p53 modulates DMMB/light‐induced phototoxicity and cell cycle dynamics. Cells lacking p53 activity were slightly more resistant to photoactivated DMMB, which was correlated with a smaller sub‐G1 population, indicative of a lower level of apoptosis. DMMB photosensitization seems to induce mostly autophagy‐associated cell death and S‐phase cell cycle arrest with replication stress. Remarkably, these responses were independent on the p53 status, indicating that p53 is not involved in either process. Despite describing some p53‐related responses in cells challenged by photosensitization, our results also provide novel information on the consequences of DMMB phototoxicity.     

Fluence Rate Determines PDT Efficiency in Breast Cancer Cells Displaying Different GSH Levels

Photodynamic therapy (PDT) appears as a promising alternative in the treatment of breast cancer since it can be highly effective in curing cancer while preserving normal tissue. However, predicting outcomes in PDT still constitutes a great challenge. One of the parameters that are usually empirically determined is the rate of photon flux delivered to the tissue (light fluence rate). In the present study, we intended to understand why monolayers of human cells derived from mammary adenocarcinomas (MDA-MB-231 and MCF-7) respond quite differently to fluence rates (cells were irradiated either for 6 or for 16 min) at a fixed light dose (4.5 J cm⁻²) delivered with an array of LEDs in a typical methylene blue PDT protocol. While death rates of MDA-MB-231 cells were insensitive to the fluence rate, MCF-7 cells showed a quite impressive (three times) decrease in cell death levels in the shorter irradiation protocol. Independent on cell type cell death was invariably correlated with the depletion of reduced glutathione intracellular levels and consequently with widespread redox misbalance. Our data show the potential to optimize fluence rates to provide exhaustion of the cell antioxidant responses in order to circumvent therapy resistance of breast tumors.     

Effects of X-ray absorption in the analysis of thick target samples by XRF

The accuracy of the quantitative analysis of thick targets by XRF is impaired by effects due to the absorption of X-rays in the matrix associated with the non-uniformity of the X-ray beam and the lack of knowledge of the actual distribution of trace elements in the target. The uncertainty in the elemental mass associated to a definite number X-rays detected is discussed in the paper. A correction factor is derived to account specifically for the effect of the absorption of X-rays and the non-uniformity of the X-ray beam. Work partially supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico, Financiadora de Estudos e Projetos and International Atomic Energy Agency.     

Fluorescence of the single tryptophan of cutinase: temperature and pH effect on protein conformation and dynamics

The cutinase from Fusarium solani pisi is an enzyme with a single L-tryptophan (Trp) involved in a hydrogen bond with an alanine (Ala) residue and located close to a cystine formed by a disulfide bridge between two cysteine (Cys) residues. The Cys strongly quenches the fluorescence of Trp by both static and dynamic quenching mechanisms. The Trp fluorescence intensity increases by about fourfold on protein melting because of the disruption of the Ala-Trp hydrogen bond that releases the Trp from the vicinity of the cystine residue. The Trp forms charge-transfer complexes with the disulfide bridge, which is disrupted by UV light irradiation of the protein. This results in a 10-fold increase of the Trp fluorescence quantum yield because of the suppression of the static quenching by the cystine residue. The Trp fluorescence anisotropy decays are similar to those in other proteins and were interpreted in terms of the wobbling-in-cone model. The long relaxation time is attributed to the Brownian rotational correlation time of the protein as a whole below the protein-melting temperature and to protein-backbone dynamics above it. The short relaxation time is related to the local motion of the Trp, whose mobility increases on protein denaturation.