Role of dietary antioxidant (-)-epicatechin in the development of ß-lactoglobulin fibrils.

Under specific physico-chemical conditions ß-lactoglobulin is seen to form fibrils structurally highly similar to those that are formed by the amyloid-like proteins associated with neurodegenerative disorders, such as Alzheimer and Parkinson diseases. In the present study we provide insights on the possible role that the dietary flavonoid (-)-epicatechin plays on ß-lactoglobulin fibril formation. Fibril formation is induced by keeping ß-lactoglobulin solutions at pH2.0 and at a temperature of 80°C for 24h. Atomic Force Microscopy measurements suggest that, by adding (-)-epicatechin in the solution, fibrils density is visibly lowered. This last observation is confirmed by Fluorescence Correlation Spectroscopy experiments. With the use of Fourier Transform IR spectroscopy we monitored the relative abundances of the secondary structures components during the heating process. We observed that in the presence of (-)-epicatechin the spectral-weight exchange between different secondary structures is partially inhibited. Molecular Dynamics simulations have been able to provide an atomistic explanation of this experimental observation, showing that (-)-epicatechin interacts with ß-lactoglobulin mainly via the residues that, normally in the absence of (-)-epicatechin, are involved in ß-sheet formation. Unveiling this molecular mechanism is an important step in the process of identifying suitable molecules apt at finely tuning fibril formation like it is desirable to do in food industry applications.

Intrinsic linewidth of the plasmonic resonance in a micrometric metal mesh.

The intrinsic linewidth and angular dispersion of Surface Plasmon Polariton resonance of a micrometric metal mesh have been measured with a collimated mid-infrared beam, provided by an External Cavity tunable Quantum Cascade Laser. We show that the use of a collimated beam yields an observed resonance linewidth γ = 12 cm(-1) at the resonance frequency ν0 = 1658 cm(-1), better by an order of magnitude than with a non-collimated beam. The extremely narrow plasmon resonance attained by our mesh is then exploited to reconstruct, by varying the QCL angle of incidence θ, the angular intensity distribution f(θ) of a globar at the focal plane of a conventional imaging setup. We thus show that f(θ) is better reproduced by a Gaussian distribution than by a uniform one, in agreement with ray-tracing simulation.

Relationship between digestibility and secondary structure of raw and thermally treated legume proteins: a Fourier transform infrared (FT-IR) spectroscopic study.

The secondary structure of proteins in legumes, cereals, milk products and chicken meat was studied by diffuse reflectance infrared spectroscopy in the region of the amide I band. Major secondary structure components ( ß-sheets, random coil, α-helix, turns), together with the low- and high-frequency side contributions, were resolved and related to the in vitro digestibility behaviour of the different foods. A strong inverse correlation between the relative spectral weights of the ß-sheet structures and in vitro protein digestibility values was measured. Structural modifications in legume proteins induced by autoclaving were monitored by the changes in the amide I spectra. The results indicate that the ß-sheet structures of raw legume proteins and the intermolecular ß-sheet aggregates, arising upon heating, are primary factors in adversely affecting the digestibility.

Infrared spectra of phosphatidylethanolamine-cardiolipin binary system.

We report on the infrared spectra of binary di-palmitoyl-phosphatidyl-ethanolamine-cardiolipin (DPPE 1-x CLPx) monolayers and multilamellar vesicles as a function of CLP molar fraction x and temperature T. These data, which clearly show the presence of, at least, two kind of lipid domains with different thermodynamic stability and ordering of the lipid acyl chains, are consistent with similar domains observed in Langmuir-Blodgett films of the same binary system. Infrared results suggest the presence of lateral phase separation phenomena both in the bilayers and in the monolayers build up with this binary lipid mixture. These results further support the hypothesis that, within these structures, DPPE 1-x CLPx molecules, for given values of x, are organized in a superlattice as shown by thermodynamic and AFM measurements.

Observation of charge-density-wave excitations in manganites.

In the optical conductivity of four different manganites with commensurate charge order (CO), strong peaks appear in the meV range below the ordering temperature T_{CO}. They are similar to those reported for one-dimensional charge density waves (CDW) and are assigned to pinned phasons. The peaks and their overtones allow one to obtain, for La_{1-n/8}Ca_{n/8}MnO_{3} with n=5, 6, the electron-phonon coupling, the effective mass of the CO system, and its contribution to the dielectric constant. These results support a description of the CO in La-Ca manganites in terms of moderately weak coupling and of the CDW theory.

Haloperidol administration in humans lowers plasma nerve growth factor level: evidence that sedation induces opposite effects to arousal.

Studies reported in recent years have indicated that the level of nerve growth factor (NGF), in both the brain and in the bloodstream, increases following stressful events and anxiety-associated behaviour. These observations prompted us to investigate whether an anti-arousal drug would induce an opposite effect. We have reported that the administration of haloperidol (HA), a neuroleptic drug clinically used for psychiatric disorders, decreases NGF levels in the hypothalamus of adult male mice. In the present study, we showed that HA reduced the basal NGF plasma levels in 8 neuroleptic-free schizophrenic patients. These observations strengthen the hypothesis that NGF may play a functional role in stress-coping responses.

Phase diagram of La2-xSrxCuO4 probed in the infared: imprints of charge stripe excitations.

While there is increasing evidence for antiferromagnetic (AF) ordering in the Cu-O planes of high-T(c) superconductors, either static or fluctuating, there is no direct evidence so far for the charge stripes that should separate the AF domains. By investigating the optical response of La2-xSrxCuO4 for 0

II Simposio Internacional de cisticercosis; I Curso de Inmunodiagnóstico Dr Rafael Flores

Comprende cuatro grandes capítulos que ofrecen un panorama del gran problema de cisticercosis y establece criterios para diagnóstico, tratamiento y control: Biología de Cisticercosis, Inmunodiagnósticos de Cisticercosis, Diagnóstico y tratamiento de Cisticercosis, Epidemiología de teniasis-Cisticercosis. Para el curso de inmunodiagnóstico se presenta la investigación de anticuerpos - anti Cysticercus cellulosae para el ensayo inmunoenzimático en fase sólida ELISA. Contiene además las primeras publicaciones que sobre Cisticercosis se han hecho en Guatemala