Victor Acha

In excitation-emission fluorescence spectroscopy, the simultaneous quantitative prediction and qualitative resolution of mixtures of fluorophores using chemometrics is a major challenge because of the scattering and reabsorption effects (turbidity) presented mainly in biomaterials. The measured fluorescence spectra are distorted by multiple scattering and reabsorption events in the surrounding medium, thereby diminishing the performance of the commonly used three-way resolution methods such as parallel factor (PARAFAC) analysis or multivariate curve resolution-alternating least squares (MCR-ALS). In this work we show that spectral loadings and concentration profiles from model mixtures provided using PARAFAC and MCR-ALS are severely distorted by reabsorption and scattering phenomena, although both models fit rather well the experimental data in terms of percentage of the explained variance. The method to correct the fluorescence excitation-emission matrix (EEM) consisted in measuring the optical properties (absorption parameter μa , scattering parameter μs, and anisotropy factor g) of samples and calculating the corresponding transfer function by means of the Monte Carlo simulation method. By applying this transfer function to the measured EEM, it was possible to compensate for reabsorption and scattering effects and to restore the ideal EEM, i.e., the EEM that is due only to fluorophores, without distortions from the absorbers and scatterers that are present. The PARAFAC and MCR-ALS decomposition of the resulting ideal EEMs provided spectral loadings and concentration profiles that matched the true profiles.

ABSTRACT Biosensors based on tissue structures in living animals can be used to detect and measure hormones, drugs, and toxins. The potential use of tissue-based biosensors extends to such diverse fields of biomedical science as physiology, pharmacology, and biodefense. In general, tissue-based biosensors can be formed from genetically modified cells or by direct genetic modification in order to introduce biosensor proteins into a tissue in the animal. Biosensor cells transduce the concentration of the molecule being detected into a physical signal, which can be precisely measured. Biophotonics provides the most versatile basis for tissue-based biosensors. Light output from biosensor cells can be in the form of fluorescence or bioluminescence, and, of these two, bioluminescence offers advantages of not requiring an input source of light and having a more favorable signal to noise ratio in living animals than fluorescence. Protein-protein interactions can be used to detect almost any molecule, by means of fusion proteins that can be used to generate resonance energy transfer. Bioluminescence resonance energy transfer (BRET) has the potential to be used for the measurement of a wide variety of molecules in living animals. Two examples are discussed here: a tissue-based biosensor for the hormone vasopressin, and a biosensor for rapamycin, both based on BRET. The possible extension of tissue-based biosensors to human subjects will require solutions to several problems, particularly the mode of detection of the physical output, and demonstration of the safety of the genetic modifications needed to introduce biosensor proteins into cells in vivo. KeywordsBiosensors-Tissues-Animals-Biomedicine-Hormones-Drugs-Toxins-Bioluminescence-Fluorescence-Resonance energy transfer-Luciferase-Photon counting-Imaging-BioMEMS-Vasopressin-Rapamycin-Human subjects

El autor nos propone una relectura de la catequesis familiar que nacio despues del Concilio vaticano ii con ocasion de la iniciacion de los ninos a la Eucaristia. Despues de establecer cuatro etapas que ha de seguir el proceso catequistico, en cuanto proceso de fe, y de destacar lo especifico de la catequesis con adultos, el articulo senala algunas posibilidades que ofrece el proyecto de la catequesis familiar y llama a la formacion de catequistas animadores de esta pastoral. Una catequesis familiar que asuma la nueva realidad que vivimos sera un aporte valido para la reevangelizacion de las familias y de sus integrantes.

This article describes the continuous on-line monitoring of a dechlorination process by a novel attenuated total reflection-Fourier transform infrared (ATR-FTIR) sensor. This optical sensor was developed to measure noninvasively part-per-million (ppm) concentrations of trichloroethylene (TCE), tetrachloroethylene (PCE), and carbon tetrachloride (CT) in the aqueous effluent of a fixed-bed dechlorinating bioreactor, without any prior sample preparation. The sensor was based on an ATR internal reflection element (IRE) coated with an extracting hydrophobic polymer, which prevented water molecules from interacting with the infrared (IR) radiation. The selective diffusion of chlorinated compound molecules from aqueous solution into the polymer made possible their detection by the IR beam. With the exclusion of water the detection limits were lowered, and measurements in the low ppm level became possible. The best extracting polymer was polyisobutylene (PIB) in the form of a 5.8-microm thick film, which afforded a detection limit of 2, 3, and 2. 5 mg/L (ppm) for TCE, PCE, and CT, respectively. Values of the enrichment factors between the polymer coating and the water matrix of these chloro-organics were determined experimentally and were compared individually with predictions obtained from the slopes of absorbance/concentration curves for the three analytes. Before coupling the ATR-FTIR sensor to the dechlorinating bioreactor, preliminary spectra of the chlorinated compounds were acquired on a laboratory scale configuration in stop-flow and flow-through closed-loop modes. In this way, it was possible to study the behavior and direct response of the optical sensor to any arbitrary concentration change of the analytes. Subsequently, the bioreactor was monitored with the infrared sensor coupled permanently to it. The sensor tracked the progression of the analytes' spectra over time without perturbing the dechlorinating process. To calibrate the ATR-FTIR sensor, a total of 13 standard mixtures of TCE, PCE and CT at concentrations ranging from 0 to 60 ppm were selected according to a closed symmetrical experimental design derived from a 3(2) full-factorial design. The above range of concentrations chosen for calibration reflected typical values during normal bioreactor operation. Several partial least squares (PLS) calibration models were generated to resolve overlapping absorption bands. The standard error of prediction (SEP) ranged between 0.6 and 1 ppm, with a relative standard error of prediction (RSEP) between 3 and 6% for the three analytes. The accuracy of this ATR-FTIR sensor was checked against gas chromatography (GC) measurements of the chlorocompounds in the bioreactor effluents. The results demonstrate the efficiency of this new sensor for routine continuous on-line monitoring of the dechlorinating bioreactor. This strategy is promising for bioprocess control and optimization.

... In order to visualize the cells in the kidney, a plastic window was fitted in the skin of the mice over this organ. The window allows the measurement of light emission from the transplanted cells without distortion by intervening layers of βγ GRK GRK βγ βγ α α GRK βγ α α βγ ...

In excitation-emission fluorescence spectroscopy, the simultaneous quantitative prediction and qualitative resolution of mixtures of fluorophores using chemometrics is a major challenge because of the scattering and reabsorption effects (turbidity) presented mainly in biomaterials. The measured fluorescence spectra are distorted by multiple scattering and reabsorption events in the surrounding medium, thereby diminishing the performance of the commonly used three-way resolution methods such as parallel factor (PARAFAC) analysis or multivariate curve resolution-alternating least squares (MCR-ALS). In this work we show that spectral loadings and concentration profiles from model mixtures provided using PARAFAC and MCR-ALS are severely distorted by reabsorption and scattering phenomena, although both models fit rather well the experimental data in terms of percentage of the explained variance. The method to correct the fluorescence excitation-emission matrix (EEM) consisted in measurin...

An aerobic methanotrophic-heterotrophic soil community has been characterised when growing with different partial pressures of CO2. The methanotrophic population using methane as carbon source reached 3 × 107 cfu ml-1 with one of the major methanotrophs being of type II which uses the serine pathway for C assimilation. Optimal methanotrophic activity required the addition of CO2, and in the absence of CO2 no methane oxidisers grew. Partial pressures of CO2 from 1.6 to 11.6 kPa gave optimal cell growth and production of soluble organic compounds. Biomass yield, soluble organics and CO2 production were 0.36, 0.15, and 0.48 mg mg-1 methane uptake, respectively, with CO2 at 11.6 kPa. The results presented here may have important implications for the use of methane-oxidising bacteria in bioremedial applications.

ABSTRACT Three-way fluorescence data originating from mixtures of fluorophores embedded in turbid media such as biological media get strongly modulated by wavelength dependent absorption and scattering phenomena. Thus the consistent resolution and quantitative determination of the mixture becomes a difficult task. In this study two chemometric methodologies frequently used to deal with this type of data were applied to fluorescence simulated data sets qualitatively similar to those measured in biological samples: Parallel Factor Analysis (PARAFAC) that does require the fulfillment of trilinearity, and multivariate curve resolution‐alternating least squares (MCR‐ALS) which decomposes the data according to a model lacking this structure. Monte Carlo simulations were used to simulate fluorescence excitation–emission matrices (EEMs) of known fluorescent mixtures under separated and simultaneous variations of the absorption parameter μa and the scattering parameter μs. PARAFAC and constrained MCR-ALS models were then fitted to the simulated data. Both algorithms failed the recover the true profiles. The results obtained with PARAFAC and MCR-ALS models are similar and the recovered profiles exhibit severe distortions due to the absorption and scattering effects. Finally, qualitative and quantitative effects of the absorption and scattering on the fluorescence data were assessed and discussed.