Stroke Damage Is Exacerbated by Nano-Size Particulate Matter in a Mouse Model

This study examines the effects of nano-size particulate matter (nPM) exposure in the setting of murine reperfused stroke. Particulate matter is a potent source of inflammation and oxidative stress. These processes are known to influence stroke progression through recruitment of marginally viable penumbral tissue into the ischemic core. nPM was collected in an urban area in central Los Angeles, impacted primarily by traffic emissions. Re-aerosolized nPM or filtered air was then administered to mice through whole body exposure chambers for forty-five cumulative hours. Exposed mice then underwent middle cerebral artery occlusion/ reperfusion. Following cerebral ischemia/ reperfusion, mice exposed to nPM exhibited significantly larger infarct volumes and less favorable neurological deficit scores when compared to mice exposed to filtered air. Mice exposed to nPM also demonstrated increases in markers of inflammation and oxidative stress in the region of the ischemic core. The findings suggest a detrimental effect of urban airborne particulate matter exposure in the setting of acute ischemic stroke.     

Compositional and Solvent Engineering in Dion–Jacobson 2D Perovskites Boosts Solar Cell Efficiency and Stability

Hybrid halide 2D perovskites deserve special attention because they exhibit superior environmental stability compared with their 3D analogs. The closer interlayer distance discovered in 2D Dion–Jacobson (DJ) type of halide perovskites relative to 2D Ruddlesden–Popper (RP) perovskites implies better carrier charge transport and superior performance in solar cells. Here, the structure and properties of 2D DJ perovskites employing 3‐(aminomethyl)piperidinium (3AMP²⁺) as the spacing cation and a mixture of methylammonium (MA⁺) and formamidinium (FA⁺) cations in the perovskite cages are presented. Using single‐crystal X‐ray crystallography, it is found that the mixed‐cation (3AMP)(MA_0.75FA_0.25)₃Pb₄I₁₃ perovskite has a narrower bandgap, less distorted inorganic framework, and larger Pb? I? Pb angles than the single‐cation (3AMP)(MA)₃Pb₄I₁₃. Furthermore, the (3AMP)(MA_0.75FA_0.25)₃Pb₄I₁₃ films made by a solvent‐engineering method with a small amount of hydriodic acid have a much better film morphology and crystalline quality and more preferred perpendicular orientation. As a result, the (3AMP)(MA_0.75FA_0.25)₃Pb₄I₁₃‐based solar cells exhibit a champion power conversion efficiency of 12.04% with a high fill factor of 81.04% and a 50% average efficiency improvement compared to the pristine (3AMP)(MA)₃Pb₄I₁₃ cells. Most importantly, the 2D DJ 3AMP‐based perovskite films and devices show better air and light stability than the 2D RP butylammonium‐based perovskites and their 3D analogs.     

Conformational study of new amphipathic alpha-helical peptide models of apoA-I as potential atheroprotective agents

Aiming at contributing to the development of potential atheroprotective agents, we report on the concept and design of two peptide models, which mimic the amphipathic helices of apoA-I and incorporate Met into their sequences to validate its role as oxidant scavenger: Ac-ESK(Palm)KELSKSW(10)SEM(13)LKEK(Palm)SKS-NH(2) (model 1 [W(10), M(13)]) and Ac-ESK(Palm)KELSKSM(10)SEW(13)LKEK(Palm)SKS-NH(2) (model 2 [M(10), W(13)]). Hydrophobic residues of both models cover about the half of the surface, while the positively and negatively charged residues constitute two separate clusters on the hydrophilic face. Palmitoyl groups were introduced into the Lys-N(epsilon)H(2) groups at positions 3 and 17 to contribute to the amphipathic character of the peptides and stabilize the nonpolar face of the helix. Conformational study by the combined application of 2D-NMR and molecular dynamics simulations, CD, FTIR, and fluorescence spectroscopy revealed that model 1 adopts helical conformation and Met is well exposed to the microenvironment. Model 2 that derives from model 1 by exchanging W(10) (model 1) with M(10) and M(13) (model 1) with W(13) also displays helical characteristics, while Met is rather shielded. Oxidation experiments indicated that model 1 exhibits a 2-fold more potent antioxidant activity towards LDL oxidation, compared to model 2, confirming the role of Met, when is devoid of steric hindrances, as oxidant scavenger for the protection of LDL.     

Development of an amperometric biosensing method for the determination of L-fucose in pretreated urine

The first amperometric biosensing method for the determination of L-fucose is described. L-Fucose is the objective of much current research, as it is considered as a potential marker for various pathologic disorders. Recombinant L-fucose dehydrogenase, having as cofactor beta-nicotinamide adenine dinucleotide phosphate (NAD+P), was cross-linked in a water-soluble photosensitive polymer matrix, that is, polyvinyl alcohol (PVA) modified with styrylpyridinium (SbQ), in the presence of BSA and glutaraldehyde. The resulting membrane was sandwiched between two polycarbonate membranes and was mounted in an amperometric cell. The oxidation of the enzymatically produced NADPH was monitored at a platinum anode at +0.25 V versus a silver pseudoreference electrode in the presence of ferricyanide. The system was fully optimized with respect to various analytical parameters. Regarding to the mechanical properties of the membrane and the storage stability of the immobilized enzyme, various parameters were also optimized. Several methods for the pretreatment of urine samples were investigated. Treatment of the samples with PbO2 found to eliminate the interference effect of various electroactive species exist in urine; optimum incubation time was determined since at prolonged incubation times L-fucose is also affected. Calibration curves for the direct and the mediated monitoring of NADPH were liner over the concentration ranges 0.04-1.0 mM (r2=0.9995) and 0.03-3.0 mM (r2=0.9997) fucose, respectively. The detection limits (S/N 3) were 2 and 1.5 microM fucose, respectively. The R.S.D. of the mediated biosensor is better than 1.5% (n=10, 0.5 mM fucose). The proposed biosensor correlates well with a reference enzymatic method and exhibits very good working and storage stability.     

Diterpenes from the brown algae Dictyota dichotoma and Dictyota linearis

Nineteen secondary metabolites of the brown alga Dictyota dichotoma (Huds.) Lam. and fifteen metabolites of the brown alga D. linearis (Ag.) Grev. were isolated and their chemical structures were elucidated on the basis of their NMR and mass spectral data. The diterpenes isopachydictyolal (1) from D. dichotoma and 4alpha-acetyldictyodial (2) from D. linearis are new natural products. The antiviral activity of metabolites isolated in adequate amounts was evaluated in laboratory assays against Herpes simplex virus I (HSV I) and Poliomyelitis Virus I, using Vero cells as hosts.     

Tendon conditioning: artefact or property?

Isolated tendons subjected to cyclic tensile loads higher than those experienced in the tendons' recent history exhibit 'conditioning', i.e. gradually increasing elongations upon loading and gradually increasing residual elongations after unloading in the first few loading-unloading cycles. The present study examines whether this behaviour is a measurement artefact or an actual time-dependent property. The gastrocnemius tendons of six men who refrained from rigorous physical activities prior to the experiment were loaded cyclically by 10 repeated isometric plantarflexion contractions at 80% of the moment generated during plantarflexion maximal voluntary contraction (MVC). In each contraction, the elongation of the gastrocnemius tendon at 80% of MVC and the residual tendon elongation after relaxation were obtained from the analysis of sonographs recorded during the test. The tendon elongation during activation and the residual tendon elongation after relaxation increased by ca. 5 mm from the first contraction to the tenth contraction, with no changes obtained after the fifth contraction. The behaviour of the tendon in the first five contractions indicates the presence of conditioning. It is therefore concluded that conditioning is a relevant property and not an artefact associated with in vitro testing. This has implications for joint kinematics and muscle excursion.     

Hydroxyl-platelet-activating factor exists in blood of healthy volunteers and periodontal patients

Periodontal diseases are localized chronic inflammatory conditions of the gingival and underlying bone and connective tissue. Platelet-activating factor (PAF), a potent inflammatory phospholipid mediator that has been previously detected in elevated levels in inflamed gingival tissues, in gingival crevicular fluid and in saliva, is implicated in periodontal disease. Our results from previous studies showed that the biologically active phospholipid detected in gingival crevicular fluid is a hydroxyl-PAF analogue. In this study, hydroxyl-PAF analogue was detected for the first time in human blood derived from patients with chronic periodontitis as well as from periodontally healthy volunteers. The hydroxyl-PAF analogue was purified by high-performance liquid chromatography, detected by biological assays and identified by electrospray analysis. In addition, the quantitative determination of PAF and hydroxyl-PAF analogue (expressed as PAF-like activity) showed a statistically significant increase in the ratio of hydroxyl-PAF analogue levels to PAF levels in periodontal patients, suggesting that this bioactive lipid may play a role in oral inflammation.     

Time-resolved resonance Raman and time-resolved step-scan FTIR studies of nitric oxide reductase from Paracoccus denitrificans: comparison of the heme b3-FeB site to that of the heme-CuB in oxidases

Time-resolved resonance Raman (TR(3)) and time-resolved step-scan (TRS(2)) FTIR spectroscopies have been used to probe the structural dynamics at the heme b(3) proximal and distal sites after carbon monoxide photolysis from fully reduced CO-bound nitric oxide reductase. The Raman spectra of the transient species exhibit structural differences relative to the equilibrium geometry of heme b(3). The most significant of these is a shift of 8 cm(-1) to higher frequency of the 207 cm(-1) mode, and a shift of 7 cm(-1) to lower frequency of the nu(4) mode. Our results indicate that the 207 cm(-1) mode observed in the equilibrium-reduced heme b(3) originates from nu(Fe-His). Its behavior in the photolytic transients indicates that the relaxed Fe-His state is not significantly populated. We suggest that relaxation along the tilt angle (theta) of the proximal histidine with respect to the heme plane and the out-of-plane displacement of the Fe (q) are coupled, and ligand binding and dissociation are accompanied by significant changes in the angular orientation of the His ligand. The results are compared to those obtained for the aa(3)-cytochrome c oxidase from Paracoccus denitrificans. The results are compared to those obtained for the aa(3)-cytochrome c oxidase from P. denitrificans. The TR(3) and TRS(2) FTIR data demonstrate significant alterations in the nature of the heme-protein dynamics between nitric oxide reductase and heme-copper oxidases resulting from specific structural differences in their respective hemepockets.     

Aminoacyl-tRNA formation in the extreme thermophile Thermus thermophilus

Thermophilic organisms must be capable of accurate translation at temperatures in which the individual components of the translation machinery and also specific amino acids are particularly sensitive. Thermus thermophilus is a good model organism for studies of thermophilic translation because many of the components in this process have undergone structural and biochemical characterization. We have focused on the pathways of aminoacyl-tRNA synthesis for glutamine, asparagine, proline, and cysteine. We show that the T. thermophilus prolyl-tRNA synthetase (ProRS) exhibits cysteinyl-tRNA synthetase (CysRS) activity although the organism also encodes a canonical CysRS. The ProRS requires tRNA for cysteine activation, as is known for the characterized archaeal prolyl-cysteinyl-tRNA synthetase (ProCysRS) enzymes. The heterotrimeric T. thermophilus aspartyl-tRNA(Asn) amidotransferase can form Gln-tRNA in addition to Asn-tRNA: however, a 13-amino-acid C-terminal truncation of the holoenzyme A subunit is deficient in both activities when assayed with homologous substrates. A survey of codon usage in completed prokaryotic genomes identified a higher Glu:Gln ratio in proteins of thermophiles compared to mesophiles.