Effect of graphite oxide electrochemically exfoliated over a multimode interference filter.

In this work, we study multimodal interference filters with a graphite oxide coating. Use of the multimodal interference filter shows a distinctive peak in the signal spectrum, and when using the exfoliated graphite coated multimodal interference filter, the signal shows different spectral changes, such as the full width at half maximum of the curve, the maximum power, and central wavelength, which indicates that graphite oxide absorbs part of the energy. In addition, microscope observations when a He-Ne laser is passed through the filter confirm that graphite oxide is adhered to the filter.

Detection of aromatic compounds in tequila through the use of surface plasmon resonance.

For an expert nose, the aroma of a beverage is a fingerprint that can be used to certify its authenticity, distinguish between distillation processes, or even identify the raw material used to fabricate it. In this work, we propose a simple, automatic, and repeatable optical method, which can be used as a first and quick test to authenticate tequila samples. This method is based on the measurement of beam intensity changes, using the surface plasmon resonance technique, operating at a fixed angle. We observed that each tequila, depending on the alcohol content and aging process, produces a specific change in measured intensity level.

Differential effects of ozone on airway and tissue mechanics in obese mice.

Obesity is an important risk factor for asthma. We recently reported increased ozone (O(3))-induced hyperresponsiveness to methacholine in obese mice (Shore SA, Rivera-Sanchez YM, Schwartzman IN, and Johnston RA. J Appl Physiol 95: 938-945, 2003). The purpose of this study was to determine whether this increased hyperresponsiveness is the result of changes in the airways, the lung tissue, or both. To that end, we examined the effect of O(3) (2 parts/million for 3 h) on methacholine-induced changes in lung mechanics with the use of a forced oscillation technique in wild-type C57BL/6J mice and mice obese because of a genetic deficiency in leptin (ob/ob mice). In ob/ob mice, O(3) increased baseline values for all parameters measured in the study: airway resistance (Raw), lung tissue resistance (Rtis), lung tissue damping (G) and elastance (H), and lung hysteresivity (eta). In contrast, no effect of O(3) on baseline mechanics was observed in wild-type mice. O(3) exposure significantly increased Raw, Rtis, lung resistance (Rl), G, H, and eta responses to methacholine in both groups of mice. For G, Rtis, and Rl there was a significant effect of obesity on the response to O(3). Our results demonstrate that both airways and lung tissue contribute to the hyperresponsiveness that occurs after O(3) exposure in wild-type mice. Our results also demonstrate that changes in the lung tissue rather than the airways account for the amplification of O(3)-induced hyperresponsiveness observed in obese mice.

Responses to ozone are increased in obese mice.

Epidemiological data indicate an increased incidence of asthma in overweight adults and children. Ozone (O3) is a common trigger for asthma. Accordingly, the purpose of this study was to compare O3-induced airway hyperresponsiveness and airway inflammation in lean, wild-type (C57BL/6J) mice and mice that are obese as a consequence of a genetic defect in the gene encoding the satiety hormone leptin (ob/ob mice). The ob/ob mice eat excessively and weighed more than twice as much as age- and gender-matched wild-type mice. Airway responsiveness to intravenous methacholine was measured by forced oscillation. In air-exposed controls, baseline pulmonary resistance was greater, and the dose of methacholine required to double pulmonary resistance was lower in ob/ob than wild-type mice. Exposure to O3 (2 parts/million for 3 h) caused AHR and airway inflammation in both groups of mice, but responses to O3 were enhanced in ob/ob compared with wild-type mice. Administration of exogenous leptin did not reverse the enhanced inflammatory response observed in ob/ob mice, but augmented airway inflammation in wild-type mice. The inhaled dose of O3 per gram of lung tissue was greater in ob/ob than wild-type mice. Our results indicate that O3-induced airway responses are enhanced in ob/ob mice and suggest that inhaled O3 dose may be one factor contributing to this difference, but other aspects of the obese phenotype may also contribute. Our results also indicate that the hormone leptin, which is increased in the obese, has the capacity to increase airway inflammation.

Structural comparison in solution of a native and retro peptide derived from the third helix of Staphylococcus aureus protein A, domain B: retro peptides, a useful tool for the discrimination of helix stabilization factors dependent on the peptide chain orientation.

A peptide fragment corresponding to the third helix of Staphylococcus Aureus protein A, domain B, was chosen to study the effect of the main-chain direction upon secondary structure formation and stability, applying the retro-enantio concept. For this purpose, two peptides consisting of the native (Ln) and reversed (Lr) sequences were synthesized and their conformational preferences analysed by CD and NMR spectroscopy. A combination of CD and NMR data, such as molar ellipcitity. NOE connectivities, H alpha and NH chemical shifts, 3J alpha N coupling constants and amide temperature coefficients indicated the presence of nascent helices for both Ln and Lr in water, stabilized upon addition of the fluorinated solvents TFE and HFIP. Helix formation and stabilization appeared to be very similar in both normal and retro peptides, despite the unfavourable charge-macrodipole interactions and bad N-capping in the retro peptide. Thus, these helix stabilization factors are not a secondary structure as determined for this specific peptide. In general, the synthesis and confirmational analysis of peptide pairs with opposite main-chain directions, normal and retro peptides, could be useful in the determination of secondary structure stabilization factors dependent on the direction.

Characterization of the conformational domains of bradykinin by computational methods.

The AMBER 4.0 force field was used to perform a characterization of the conformational profile of the nonapeptide bradykinin. A thorough conformational search was carried out using molecular dynamics as sampling technique, by computing cycles of high (900 K) and low (300 K) temperature trajectories. A total of 2400 minima were generated and subsequently clustered using the root-mean-square of the backbone dihedral angles as criterium. After the use of a tolerance value of 20 degrees, the conformations were clustered in 233 unique conformations with energies up to 40 kcal/mol above the lowest minimum. The analysis of the low-energy conformations indicate that the peptide exhibits a high tendency to adopt a beta-turn at the C-terminus and a propensity to adopt a bent structure at the N-terminus. These results are in agreement with the experimental evidence reported in the literature and provide detailed information necessary to understand the conformational preferences of the peptide.