The molar extinction coefficient of bacteriochlorophyll e and the pigment stoichiometry in Chlorobium phaeobacteroides

We have determined the molar extinction coefficient of bacteriochlorophyll (BChl) e, the main light-harvesting pigment from brown-coloured photosynthetic sulfur bacteria. The extinction coefficient was determined using pure[Pr,E]BChl eF isolated by reversed-phase HPLC from crude pigment extracts of Chlorobium (Chl.) phaeobacteroides strain CL1401. The extinction coefficients at the Soret and Qy bands were determined in four organic solvents. The extinction coefficient of BChl e differs from those of other related Chlorobium chlorophylls (BChl c and BChl d) but is similar to that of chlorophyll b. The determined extinction coefficient was used to calculate the stoichiometric BChl e to BChl a and BChl e to carotenoids ratios in whole cells and isolated chlorosomes from Chl. phaeobacteroides strain CL1401 using the spectrum-reconstruction method (SRCM) described by Naqvi et al. (1997) (Spectrochim Acta A Mol Biomol Spectrosc 53: 2229–2234). In isolated chlorosomes, BChl a content was ca. 1% of the total BChl content and the stoichiometric ratio of BChl e to carotenoids was 6. In whole cells,however, BChl a content was 3–4%, owing to the presence of BChl a-containing elements, i.e. FMO protein and reaction centre. An average of 5 BChl e molecules per carotenoid was determined in whole cells.EU(Contract No FMRX–CT96–0081). Ministerio de Educación y Ciencia (Ref. BIO96–1229–002–01)Peer reviewe

Phase profile analysis of transparent objects through the use of a two windows interferometer based on a one beam splitter configuration

AbstractIn this research we implemented a two windows interferometer based on polarization phase shifting and grating interferometry techniques in order to retrieve the phase data profile of the object in a single capture. The optical configuration has two optical beams with circular polarization in opposite directions, and it is coupled with a 4-f system. An amplitude grid is used as a filter which is placed at the Fourier plane to obtain replicas of each beam which can properly interfere, depending on the separation between beams. The interferometer presents the capability of changing the beam separation in order to make different orders interfere properly. The interference patterns produced can be separately modulated through the operation of linear polarizer's placed on each interference replica. In order to present the capabilities of the system we will select four interferograms result of contiguous orders interference

Nanosecond laser photolysis studies of chlorosomes and artificial aggregates containing bacteriochlorophyll e: Evidence for the proximity of carotenoids and bacteriochlorophyll a in chlorosomes from Chlorobium phaeobacteroides strain CL1401

Time-resolved, laser-induced changes in absorbance, ΔA(λ; t), have been recorded with a view to probing pigment–pigment interactions in chlorosomes (control as well as carotenoid-depleted) and artificial aggregates of bacteriochlorophyll e (BChle). Control chlorosomes were isolated from Chlorobium phaeobacteroides strain CL1401, whose chromophores comprise BChle, bacteriochlorophyll a (BChla) and several carotenoid (Car) pigments; Car-depleted chlorosomes, from cells grown in cultures containing 2-hydroxybiphenyl. Artificial aggregates were prepared by dispersing BChle in aqueous phase in the presence of monogalactosyl diglyceride. In chlorosomes ΔA(λ; t) shows, besides a signal attributable to triplet Car (with a half-life of about 4 μs), signals in the Qy regions of both BChl. The BChla signal decays at the same rate as the Car signal, which is explained by postulating that some Car are in intimate contact with some baseplate BChla pigments, and that when a ground-state Car changes into a triplet Car, the absorption spectrum of its BChla neighbors undergoes a concomitant change (termed transient environment-induced perturbation). The signal in the Qy-region of BChle behaves differently: its amplitude falls, under reducing conditions, by more than a factor of two during the first 0.5 μs (a period during which the Car signal suffers negligible diminution), and is much smaller under nonreducing conditions. The BChle signal is also attributed to transient environment-induced perturbation, but in this case the perturber is a BChle photoproduct (probably a triplet or a radical ion). The absence of long-lived BChle triplets in all three systems, and of long-lived BChla triplets in chlorosomes, indicates that BChle in densely packed assemblies is less vulnerable to photodamage than monomeric BChle and that, in chlorosome, BChla rather than BChle needs, and receives, photoprotection from an adjacent Car.Research Council of Norway. EU (contract FMRX-CT96-0081)Peer reviewe

Study on extraction, purification and characterization of a novel peroxidase from white Spanish broom (Cytisus multiflorus)

Peroxidases (EC 1.11.1.7) are a large group of enzymes widely distributed in the plant kingdom. The present work describes a study on the isolation, purification and some features of a novel peroxidase from white Spanish broom (Cytisus multiflorus), a tree legume very abundant in the northern half of Spain and Portugal. Optimal conditions are proposed for enzyme extraction, removal of phenolic compounds and enzyme purification by consecutive hydrophobic, ion-exchange and size-exclusion chromatographies. Peroxidase from Cytisus multiflorus (CMP) was found to have a molecular weight of 49 kDa. The spectrum of CMP showed a Soret band at 403 nm with a Rz factor of 3.3. Substrate specificity and the effect of some variables on the activity of CMP with guaiacol as cosubstrate have also been investigated.This work was partially supported by project SA052A10-2, funded by Consejería de Educación de la Junta de Castilla y León (Spain).Peer reviewe

Evaluation of inflammatory cytokine secretion by human alveolar macrophages.

The alveolar macrophage (AM) secretes interleukin 1beta (IL-1beta), tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and interleukin-8 (IL-8), all of them inflammatory cytokines involved in the pathogenesis of many lung diseases. The aim of the present work was to evaluate the basal and stimulated secretion of these cytokines by human AMs. Human AMs were collected by bronchoalveolar lavage (BAL) from four healthy controls and 13 patients with diffuse interstitial lung disease (five cases of sarcoidosis, three of hypersensitivity pneumonitis and five of idiopathic pulmonary fibrosis). AMs were cultured in the presence or absence of different concentrations of lipopolysaccharide (LPS), phorbolmyristate and gamma-interferon. IL-1beta, TNF-alpha, IL-6 and IL-8 levels were measured in BAL fluid and culture supernatant using specific enzyme-linked immunosorbent assays. The substance found to stimulate the secretion of inflammatory cytokines to the greatest extent was LPS at a concentration of 10 microg/ml. Regarding the secretion of IL-1beta, four observations were of interest: basal secretion was very low; LPS exerted a potent stimulatory effect; considerable within-group variability was observed; and there were no significant differences in the comparisons among groups. With respect to TNF-alpha secretion, the results were similar. The only striking finding was the higher basal secretion of this cytokine with respect to that of IL-1beta. Regarding the secretion of IL-6, the same pattern followed by TNF-alpha was found. However, it should be stressed that the increase induced by LPS was smaller than in the two previous cytokines. Regarding the secretion of IL-8, three findings were patent: the strong basal secretion of this cytokine; the moderate increase induced by LPS; and the existence of significant differences among the different groups with respect to the stimulated secretion of this cytokine, which reached maximum values in patients with idiopathic pulmonary fibrosis. Finally, it should be noted that the pattern of cytokines observed in the BAL fluid was similar to that found in cultured AM supernatants. The pattern of inflammatory cytokine secretion by AMs differs from that of other cells of the mononuclear phagocyte system (MPS). In this sense. AMs secrete low amounts of IL-1, moderate amounts of TNF-alpha and IL-6, and high quantities of IL-8. Adherence is an important stimulus in the secretion of these molecules and LPS elicits an increased secretion inverse to the basal secretion. There is considerable individual variability in the secretion of inflammatory cytokines by the AMs of patients with interstitial lung disease and the AMs of these patients are primed in vivo for the secretion of these cytokines. The results of our study, carried out in vitro, can be extrapolated to the in vivo setting

Validación de negocio Startup MX

Uno de los principales objetivos anuales en las empresas de manufactura electrónica es la disminución de costo en la operación del área de Mantenimiento. Este objetivo es difícil de alcanzar pues siempre se busca la mejor calidad de refacciones, materiales y mano de obra disponible. Además, en empresas como Continental y Sanmina, el control de residuos que se genera en planta es un tema importante ya que están comprometidas con el medio ambiente con certificación ISO 14001 y como Empresa Socialmente Responsable (ESR). En este trabajo se presenta el modelo de negocio de la empresa Startup MX que ofrece soluciones en la reducción de costos y residuos específicamente a la empresa Continental. Con la propuesta que se expone, esta empresa ahorraría el 75% del costo en tarjetas electrónicas. Se presenta el lienzo del modelo de negocio para el que se usó la técnica "Get out of the building". Se realizaron más de 20 entrevistas a diferentes directivos de Continental para entender las necesidades específicas del área y los requerimientos para ser su proveedor

A search for diffuse bands in the circumstellar envelopes of post-AGB stars

In this work we present the results of a systematic search for diffuse bands (DBs, hereafter) in the circumstellar envelopes of a carefully selected sample of post-AGB stars. We concentrated on the analysis of 9 of the DBs most commonly found in the interstellar medium. The strength of these features is determined using high resolution optical spectroscopy and the results obtained are compared with literature data on field stars affected only by interstellar reddening. Based on the weak features observed in the subsample of post-AGB stars dominated by circumstellar reddening we conclude that the carrier(s) of these DBs must not be present in the circumstellar environment of these sources, or at least not under the excitation conditions in which DBs are formed. The conclusion is applicable to all the post-AGB stars studied, irrespective of the dominant chemistry or the spectral type of the star considered. A detailed radial velocity analysis of the features observed in individual sources confirms this result, as the Doppler shifts measured are found to be consistent with an interstellar origin.Comment: Accepted for A&

Molecular method for the characterization of Coxiella burnetii from clinical and environmental samples: variability of genotypes in Spain

BACKGROUND: Coxiella burnetii is a highly clonal microorganism which is difficult to culture, requiring BSL3 conditions for its propagation. This leads to a scarce availability of isolates worldwide. On the other hand, published methods of characterization have delineated up to 8 different genomic groups and 36 genotypes. However, all these methodologies, with the exception of one that exhibited limited discriminatory power (3 genotypes), rely on performing between 10 and 20 PCR amplifications or sequencing long fragments of DNA, which make their direct application to clinical samples impracticable and leads to a scarce accessibility of data on the circulation of C. burnetii genotypes. RESULTS: To assess the variability of this organism in Spain, we have developed a novel method that consists of a multiplex (8 targets) PCR and hybridization with specific probes that reproduce the previous classification of this organism into 8 genomic groups, and up to 16 genotypes. It allows for a direct characterization from clinical and environmental samples in a single run, which will help in the study of the different genotypes circulating in wild and domestic cycles as well as from sporadic human cases and outbreaks. The method has been validated with reference isolates. A high variability of C. burnetii has been found in Spain among 90 samples tested, detecting 10 different genotypes, being those adaA negative associated with acute Q fever cases presenting as fever of intermediate duration with liver involvement and with chronic cases. Genotypes infecting humans are also found in sheep, goats, rats, wild boar and ticks, and the only genotype found in cattle has never been found among our clinical samples. CONCLUSIONS: This newly developed methodology has permitted to demonstrate that C. burnetii is highly variable in Spain. With the data presented here, cattle seem not to participate in the transmission of C. burnetii to humans in the samples studied, while sheep, goats, wild boar, rats and ticks share genotypes with the human population