Kinetic changes in activity of HR-peroxidase, induced by very low doses of phenol

The allosteric protein of horseradish peroxidase (HRP) shows two main types of activity, peroxidase and oxidase, depending on the kind of low molecular effectors. The effects of very low doses of phenol, prepared by successive dilutions in water or in 75% ethanol, on initial HRP activity in oxidation of o-dianisidine or luminol were tested in a systematic manner by colorimetric and luminometric methods. Results showed that phenol dilutions, including those below Avogadro’s number, could activate or inhibit HRP in peroxidase and oxidase type reactions with a sinusoidal pattern. Km values for the studied substrates changed parallel to HRP peroxidase/oxidase activity and the maximum activity in the peroxidase reaction corresponded to the minimum activity in the oxidase reaction and vice versa. The effect also depended on the type of dilutor. The observations of the peroxidase/oxidase oscillations in the sinusoidal pattern of HRP activity, dependent on the rate of phenol dissolution and the time of preincubation, point out to the conclusion that HRP might be a good model for high dilutions research. The experiments provide strong evidence that horseradish peroxidase (HRP) is a very sensitive detector of subtle changes in the concentration of phenol used as a cofactor in the peroxidase/oxidase reaction. Keywords: HR-peroxidase, peroxidase-oxidase, phenol, hormesis, homeopathy, high dilutions.  Mudanças cinéticas na atividade da HR-peroxidade induzidas por doses muito baixas de fenol Resumo A proteína alostérica da peroxidase do rabano (HRP) mostra dois tipos principais de atividade, peroxidase e oxidase, de acordo com o tipo de efetores de baixa molecularidade. Os efeitos de doses muito baixas de fenol, preparadas através de diluições sucessivas em água ou etanol 75% na atividade inicial da HRP sobre a oxidação da o-dianisidina ou luminol for testados de modo sistemático através de métodos colorimétricos e luminométricos. Os resultados mostram que as diluições de fenol, incluindo aquelas por baixo do número de Avogadro, foram capazes de ativar ou inibir a HRP em reações de tipo peroxidade e oxidase com um padrão sinusoidal. os valores Km dos substratos estudados variaram paralelamente àatividade peroxidase/oxidase da HRP; a atividade máxima da reação peroxidase correspondeu àatividade mínima na reação oxidase e vice-versa. O efeito também se mostrou dependente do tipo do solvente. A observação das oscilações sinusoidais na atividade da HRP, dependentes da taxa de dissolução do fenol e do tempo de pré-incubação, permitem concluir que a HRP pode ser um bom modelo na pesquisa das altas diluições. Os experimentos oferecem fortes evidéncias a favor da HRP como detector muito sensível de mudanças mínimas na concentração do fenol, utilizado como cofator na reação peroxidase/oxigenase. Palavras-chave: HR-peroxidase, peroxidase-oxidase, fenol, hormese, homeopatia, altas diluições.  Cambios cinéticos en la actividad de la HR-peroxidasa inducidos por dosis muy bajas de fenol Resumen La proteína alostérica de la peroxidasa del rábano (HRP) muestra dos tipos principales de actividad, peroxidasa y oxidasa, dependiendo del tipo de efectores de baja molecularidade. Los efectos de doses muy bajas de fenol, preparadas mediante diluciones sucesivas en agua o etanol al 75% sobre la actividad inicial de la HRP sobre la oxidación de o-dianisidina o luminol fueron testados de modo sistemático mediante métodos colorimétricos y luminométricos. Los resultados muestran que las diluciones de fenol, incluyendo aquellas abajo del número de Avogadro, pudieron activar o inhibir la HRP en reacciones de tipo peroxidasa y oxidasa con un patrón sinusoidal. Los valores Km de los sustratos estudiados variaron paralelamente a la actividad peroxidasa/oxidasa de la HRP; la actividad máxima de la reacción peroxidasa correspondió a la actividad mínima en la reacción oxidasa y viceversa. El efecto también se mostró dependiente del tipo de solvente. La observación de las oscilaciones sinusoidales en la actividad de la HRP, dependientes de la tasa de disolución del fenol y del tiempo de preincubación, llevan a concluir que la HRP puede ser un buen modelo para la investigación de las altas diluciones. Los experimentos ofrecen fuertes evidencias a favor de la HRP como detector muy sensible de cambios mínimos en la concentración de fenol, utilizado como cofactor en la reacción peroxidasa/oxigenasa. Palabras-clave: HR-peroxidasa, oxidasa-peroxidasa, fenol, hormesis, homeopatía, altas diluciones.  Correspondence author: Elzbieta Malarczyk, [email protected] How to cite this article: Malarczyk E. Kinetic changes in the activity of HR-peroxidase induced by very low doses of phenol. Int J High Dilution Res [online]. 2008 [cited YYYY Mmm DD]; 7(23): 48-55. Available from: http://journal.giri-society.org/index.php/ijhdr/article/view/37/349. ÂÂÂ

MEMS-Scanner Testbench for High Field of View LiDAR Applications

LiDAR sensors are a key technology for enabling safe autonomous cars. For highway applications, such systems must have a long range, and the covered field of view (FoV) of >45° must be scanned with resolutions higher than 0.1°. These specifications can be met by modern MEMS scanners, which are chosen for their robustness and scalability. For the automotive market, these sensors, and especially the scanners within, must be tested to the highest standards. We propose a novel measurement setup for characterizing and validating these kinds of scanners based on a position-sensitive detector (PSD) by imaging a deflected laser beam from a diffuser screen onto the PSD. A so-called ray trace shifting technique (RTST) was used to minimize manual calibration effort, to reduce external mounting errors, and to enable dynamical one-shot measurements of the scanner’s steering angle over large FoVs. This paper describes the overall setup and the calibration method according to a standard camera calibration. We further show the setup’s capabilities by validating it with a statically set rotating stage and a dynamically oscillating MEMS scanner. The setup was found to be capable of measuring LiDAR MEMS scanners with a maximum FoV of 47° dynamically, with an uncertainty of less than 1%.

Development of an Energy-Sensitive Detector for the Atom Probe Tomography

A position and energy-sensitive detector has been developed for atom probe tomography (APT) instruments in order to deal with some mass peak overlap issues encountered in APT experiments. Through this new type of detector, quantitative and qualitative improvements could be considered for critical materials with mass peak overlaps, such as nitrogen and silicon in TiSiN systems, or titanium and carbon in cemented carbide materials. This new detector is based on a thin carbon foil positioned on the front panel of a conventional MCP-DLD detector. According to several studies, it has been demonstrated that the impact of ions on thin carbon foils has the effect of generating a number of transmitted and reflected secondary electrons. The number generated mainly depends on both the kinetic energy and the mass of incident particles. Despite the fact that this phenomenon is well known and has been widely discussed for decades, no studies have been performed to date for using it as a means to discriminate particles energy. Therefore, this study introduces the first experiments on a potential new generation of APT detectors that would be able to resolve mass peak overlaps through the energy-sensitivity of thin carbon foils.