Amyloidogenic Properties of Peptides Derived from the VHL Tumor Suppressor Protein

The von Hippel-Lindau tumor suppressor protein (pVHL) is involved in maintaining cellular oxygen homeostasis through the regulated degradation of HIF-α. The intrinsically disordered nature of pVHL makes it prone to aggregation that impairs its function, and this is further aggravated in mutant versions of the protein, thus promoting tumor development. By using in silico analysis, we predicted six peptide fragments from pVHL to be amyloidogenic. This was verified for two of the peptides by biophysical approaches, which demonstrated self-assembly and formation of β-sheet-rich aggregates, which, under transmission electron microscopy, atomic force microscopy, and X-ray diffraction, displayed typical fibrillar amyloid characteristics. These motifs may serve as proxies for exploring the nature of pVHL aggregation.     

n-Hexadecane hydroisomerization over Pt/ZSM-12: role of Si/Al ratio on product distribution

The crystallization of pure ZSM-12 phase was accomplished at Si/Al ratios ranging from 45 to 120 using tetraethylammonium bromide as the structure directing agent. The obtained samples were characterized by X-ray diffraction, scanning electron microscopy, temperature programmed desorption of ammonia, and nitrogen adsorption–desorption measurements at 77 K, respectively. The well characterized samples were used to prepare Pt (0.5 wt%)/ZSM-12 hydroisomerization catalysts which were employed to perform n-hexadecane isomerization reaction. The catalysts were compared in terms of their activity, selectivity and product distribution at different conversion levels obtained through variation in temperature and residence times. Thus, obtained trend for product distribution over Pt/ZSM-12 system has been discussed in terms of framework Si/Al ratio to understand its role in determining the product selectivity. ZSM-12 with Si/Al ratio of 120 depicted the highest overall selectivity and favored mono-branching while those having Si/Al ratio of 45, 60 and 90 were found to favor mutlti-branching.     

Formation of Zinc–Antimony-Based Spinel Phases

Formation of spinel phases in ZnO–Sb₂O₃and ZnO–Sb₂O₃–Bi₂O₃systems is studied by the use of X-ray diffraction. The formation of nonstoichiometric Zn_2.33Sb_0.67O₄phase is observed in both the systems at ∼900°C. However, in these systems, at higher temperatures ( T ≥ 1100°C), formation of the inverse spinel phase Zn₇Sb₂O₁₂is observed. The study has been extended to understand the effect of CrO₃doping on the stability of the different spinel phases in the previously mentioned systems. Interestingly, in both the systems, samples doped with CrO₃, displayed the presence of Zn_2.33Sb_0.67O₄phase <1200°C, indicating the stabilization of the spinel phase by CrO₃.     

Low Concentrations of Salicylic Acid Stimulate Insect Elicitor Responses in <Emphasis Type="Italic">Zea mays</Emphasis> Seedlings

Salicylic acid (SA) generally is thought to suppress jasmonic acid (JA) related signaling events. However, when we treated the roots of corn seedlings overnight with low physiological concentrations of SA (50 μM), we found a priming effect of this pretreatment on typical insect elicitor (IE)-induced responses in the leaves of these plants. IE-induced JA was more than 2-fold up regulated in SA-pretreated plants. Consequently, IE-induced volatile organic compounds (VOC) release also was significantly increased. In contrast, when corn seedlings were treated with SA overnight and then mechanically damaged, we found no significant differences in JA accumulation. We also found that the application of even lower concentrations of SA (5 μM) had no significant effect on IE-induced responses, while higher concentrations (500 μM) inhibited IE-induced JA accumulation. Likewise, shorter exposure to SA did not affect subsequent JA accumulation induced by IE or mechanical wounding. These results provide evidence for the existence of non-compatible defense priming by signaling molecules that usually are involved in a conflictive defense signaling pathway and suggests common elements in the regulation of priming plant defense responses.     

Electrochemical investigation of chromium nanocarbide coated Ti–6Al–4V and Co–Cr–Mo alloy substrates

This study investigated the electrochemical behavior of chromium nano-carbide cermet coating applied on Ti–6Al–4V and Co–Cr–Mo alloys for potential application as wear and corrosion resistant bearing surfaces. The cermet coating consisted of a highly heterogeneous combination of carbides embedded in a metal matrix. The main factors studied were the effect of substrate (Ti–6Al–4V vs. Co–Cr–Mo), solution conditions (physiological vs. 1 M H₂O₂ of pH 2), time of immersion (1 vs. 24 h) and post coating treatments (passivation and gamma sterilization). The coatings were produced with high velocity oxygen fuel (HVOF) thermal spray technique at atmospheric conditions to a thickness of 250 μm then ground and polished to a finished thickness of 100 μm and gamma sterilized. Native Ti–6Al–4V and Co–Cr–Mo alloys were used as controls. The corrosion behavior was evaluated using potentiodynamic polarization, mechanical abrasion and electrochemical impedance spectroscopy under physiologically representative test solution conditions (phosphate buffered saline, pH 7.4, 37 °C) as well as harsh corrosion environments (pH ～ 2, 1 M H₂O₂, T = 65 °C). Severe environmental conditions were used to assess how susceptible coatings are to conditions that derive from possible crevice-like environments, and the presence of inflammatory species like H₂O₂. SEM analysis was performed on the coating surface and cross-section. The results show that the corrosion current values of the coatings (0.4–4 μA/cm²) were in a range similar to Co–Cr–Mo alloy. The heterogeneous microstructure of the coating influenced the corrosion performance. It was observed that the coating impedances for all groups decreased significantly in aggressive environments compared with neutral and also dropped over exposure time. The low frequency impedances of coatings were lower than controls. Among the coated samples, passivated nanocarbide coating on Co–Cr–Mo alloy displayed the least corrosion resistance. However, all the coated materials demonstrated higher corrosion resistance to mechanical abrasion compared to the native alloys.     

Determination of the structure and orientation of organic molecules tethered to flat graphitic carbon by ATR-FT-IR and Raman spectroscopy

Mono- and multilayers of nitroazobenzene (NAB), azobenzene (AB), nitrobiphenyl (NBP), biphenyl (BP), and fluorene (FL) were covalently bonded to flat pyrolyzed photoresist films (PPF) by electrochemical reduction of their diazonium derivatives. The structure and orientation of the molecular layers were probed with ATR-FT-IR and Raman spectroscopy. A hemispherical germanium ATR element used with p-polarized light at 65 degrees incidence angle yielded high signal/noise IR spectra for monolayer coverage of molecules on PPF. The IR spectra are dominated by in-plane vibrational modes in the 1000-2000-cm(-1) spectral range but also exhibit weaker out-of-plane deformations in the 650-1000-cm(-1) region. The average tilt angle with respect to the surface normal for the various molecules varied from 31.0 +/- 4.5 degrees for NAB to 44.2 +/- 5.4 degrees for FL with AB, NBP, and BP exhibiting intermediate adsorption geometries. Raman intensity ratios of NAB and AB for p- and s-polarized incident light support the conclusion that the chemisorbed molecules are in a predominantly upright orientation. The results unequivocally indicate that molecules electroreduced from their diazonium precursors are not chemisorbed flat on the PPF surface, but rather at an angle, similar to the behavior of Au/thiol self-assembled monolayers, Langmuir-Blodgett films, and porphyrin molecules chemisorbed thermally on silicon and PPF from alkyne and alkene precursors.     

Modeling mobile source emissions in presence of stationary sources

The impact of oxides of nitrogen (NO(x)) emissions from motor vehicles to the air quality in city-state Singapore is analyzed using AIRVIRO, a regional scale dispersion model developed by the Swedish Meteorological and Hydrological Institute. In a predominantly urban location like Singapore, it is difficult to separate out the contribution of pollutants from mobile and point sources at different locations. In this work, a new approach is used by first modeling only the impact of point and area sources and then overlaying the traffic impact on air quality at different locations. Monthly scenario simulations are run with point, area and traffic sources of emissions for the Gaussian model validation. Street Canyon modeling is used for street segments surrounded by buildings on either side. A simplified photochemical model, which takes into account NO(x) undergoing chemical transformations in the urban atmosphere, is used to account for variations in NO(x) and ozone levels with respect to traffic data. The diurnal variation of NO(x) concentration levels is studied as a function of ozone levels at site, hourly traffic counts and meteorological parameters. The impact on ambient air quality within the breathing zone of the public from mobile sources, is found to be about 40% at urban stations although overall emissions from mobile sources is only 24%. The proposed approach appears to predict the variations in NO(x) as a function of traffic and meteorological conditions.     

Vibration analysis of cross-ply laminated truncated conical shells using a spline method

Free vibration of symmetric and antisymmetric cross-ply composite laminated truncated conical shells using the spline function technique is studied. The equilibrium equations for a truncated conical shells are formulated including first-order shear deformation theory. The equations of motion are derived in terms of displacement functions and rotational functions using stress–strain and strain–displacement relationships. The coupled differential equations are solved using Bickley-type splines to obtain the generalized eigenvalue problem by combining suitable boundary conditions. The convergence and comparative results are presented. Both symmetric and anti-symmetric cross-ply shells are considered using various types of material properties. Parametric studies are made to investigate the effect of transverse shear deformation on the frequency parameter with respect to the thickness ratio, length ratio, cone angle, and circumferential mode number using different numbers of layers under various types of boundary conditions.     

Early detection of visual field progression in glaucoma: a comparison of PROGRESSOR and STATPAC 2

AIM: To compare the performance of PROGRESSOR (pointwise linear regression) and STATPAC 2 (comparison with baseline values) in detecting early deterioration in the visual fields of glaucoma patients. METHODS: Visual field series from 19 untreated normal tension glaucoma eyes which were deteriorating on clinical grounds were analysed by PROGRESSOR and STATPAC 2. Progression criteria for PROGRESSOR were (1) inner points: slope < -1 dB/year, p < 0.05 and (2) edge points: slope < -2 dB/year, p < 0.05. Criteria for STATPAC 2 were p < 0.05 change probability for any point on three consecutive fields. Detection time was defined as the time interval between the initial field and the first field in which at least one progressing point was identified. Detection times produced by the two techniques were compared. RESULTS: PROGRESSOR and STATPAC 2 agreed on progression in all 19 eyes. Mean detection time for PROGRESSOR was 1.077 (SD 0.985) years and for STATPAC 2 was 2.161 (1.357) years. PROGRESSOR detected progression sooner than STATPAC 2 in 18 eyes (p < 0.01), Wilcoxon matched pairs signed rank test). PROGRESSOR detected progression earlier by a mean of 1.085 (0.936) years. CONCLUSIONS: PROGRESSOR consistently detected progression earlier than STATPAC 2. The PROGRESSOR software is a useful tool for the early detection of visual field deterioration in glaucoma.