Mapping of functionalized regions on carbon nanotubes by scanning tunneling microscopy

Scanning tunneling microscopy (STM) gives us the opportunity to map the surface of functionalized carbon nanotubes in an energy resolved manner and with atomic precision. But this potential is largely untapped, mainly due to sample stability issues which inhibit reliable measurements. Here we present a simple and straightforward solution that makes away with this difficulty, by incorporating the functionalized multiwalled carbon nanotubes (MWCNT) into a few layer graphene - nanotube composite. This enabled us to measure energy resolved tunneling conductance maps on the nanotubes, which shed light on the level of doping, charge transfer between tube and functional groups and the dependence of defect creation or functionalization on crystallographic orientation.Comment: Keywords: functionalization, carbon nanotubes, few layer graphene, STM, CITS, ST

Extracellular deposition of matrilin-2 controls the timing of the myogenic program during muscle regeneration.

Here, we identify a role for the matrilin-2 (Matn2) extracellular matrix protein in controlling the early stages of myogenic differentiation. We observed Matn2 deposition around proliferating, differentiating and fusing myoblasts in culture and during muscle regeneration in vivo. Silencing of Matn2 delayed the expression of the Cdk inhibitor p21 and of the myogenic genes Nfix, MyoD and Myog, explaining the retarded cell cycle exit and myoblast differentiation. Rescue of Matn2 expression restored differentiation and the expression of p21 and of the myogenic genes. TGF-β1 inhibited myogenic differentiation at least in part by repressing Matn2 expression, which inhibited the onset of a positive-feedback loop whereby Matn2 and Nfix activate the expression of one another and activate myoblast differentiation. In vivo, myoblast cell cycle arrest and muscle regeneration was delayed in Matn2(-/-) relative to wild-type mice. The expression levels of Trf3 and myogenic genes were robustly reduced in Matn2(-/-) fetal limbs and in differentiating primary myoblast cultures, establishing Matn2 as a key modulator of the regulatory cascade that initiates terminal myogenic differentiation. Our data thus identify Matn2 as a crucial component of a genetic switch that modulates the onset of tissue repair

The effect of nasal provocation with a single-dose allergen on the physical and cognitive performance of patients with ragweed allergy

Purpose This study aims to compare the impact of active allergic rhinitis on physical and cognitive abilities of trained allergic athletes to untrained allergic patients. Methods Cognitive, respiratory, and fitness functions were assessed before and after allergen exposure. Participants in both groups were provoked intranasally with ragweed allergen. Results The group of athletes revealed significantly higher average values in peak inspiratory flow and fitness index before and after provocation. In neuropsychological assessments, athletes performed significantly better after allergen provocation in complex working memory capacity. Due to single acute allergen exposure, the size of the nasal cavity and nasal inspiratory peak flow significantly decreased in both groups. The physical performance of both groups did not change after provocation. Executive functions and complex working memory capacity of athletes significantly improved resulting from provocation. Conclusions A single-shot allergen in high dose might cause an increase in mental concentration, which was more pronounced in the group of athletes. This study indicates that acute exposure to allergen cannot affect the physical performance and may result in increased mental focus in patients with allergy notwithstanding the declining respiratory functions

Pulmonary impact of titanium dioxide nanorods: examination of nanorod-exposed rat lungs and human alveolar cells

Background: Titanium dioxide nanoparticles have numerous applications, resulting in human exposure. Nonetheless, available toxicological and safety data are insufficient regarding aspherical particles, such as rod-shaped nanoparticles

Propene adsorption and reaction on zeolites and pillared clays

Comparative IR and UV-Vis spectroscopic studies of propene adsorption and reaction on H-mordenite, dealuminated H-mordenite, dealuminated mazzite, montmorillonite and Al~3-pillared montmorillonite have been carried out. On all systems propene is first transformed into polymeric species (C.H2.+~+). On HMOR (both as such and dealuminated), allylic carbocations are successively produced by loss of H 2, the monoenic species (C.H2~., +) being formed at room temperature and the dienic (C,H2..3 § and trienic (C.Hz,_s +) species at higher temperatures. These species are not observed on the other systems, although they are presumably formed as unstable intermediates. In fact, on all the zeolites studied here two cyclic penta-atomic and hexa-atomic allylic carbocations have been observed for the first time. On all systems, the final products of reaction are polyaromatic species which, on the basis of their reaction with NH 3 still exhibit unsaturated carbocation behaviour. The activity of the various samples depends on their pore dimensions and on the nature of acidic sites involved: the larger the available pore space, the more branched is the polymer and the more difficult it is to observe allylic carbocations. Evidence is provided for a Bronsted-induced mechanism

Silver nanoparticles: aggregation behavior in biorelevant conditions and its impact on biological activity

Péter Bélteky,1 Andrea Rónavári,1,2 Nóra Igaz,2 Bettina Szerencsés,3 Ildikó Y Tóth,1 Ilona Pfeiffer,3 Mónika Kiricsi,2 Zoltán Kónya1,4 1Department of Applied and Environmental Chemistry, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary; 2Department of Biochemistry and Molecular Biology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary; 3Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary; 4MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, Szeged, Hungary Purpose: The biomedical applications of silver nanoparticles (AgNPs) are heavily investigated due to their cytotoxic and antimicrobial properties. However, the scientific literature is lacking in data on the aggregation behavior of nanoparticles, especially regarding its impact on biological activity. Therefore, to assess the potential of AgNPs in therapeutic applications, two different AgNP samples were compared under biorelevant conditions.Methods: Citrate-capped nanosilver was produced by classical chemical reduction and stabilization with sodium citrate (AgNP@C), while green tea extract was used to produce silver nanoparticles in a green synthesis approach (AgNP@GTs). Particle size, morphology, and crystallinity were characterized using transmission electron microscopy. To observe the effects of the most important biorelevant conditions on AgNP colloidal stability, aggregation grade measurements were carried out using UV-Vis spectroscopy and dynamic light scatterig, while MTT assay and a microdilution method were performed to evaluate the effects of aggregation on cytotoxicity and antimicrobial activity in a time-dependent manner.Results: The aggregation behavior of AgNPs is mostly affected by pH and electrolyte concentration, while the presence of biomolecules can improve particle stability due to the biomolecular corona effect. We demonstrated that high aggregation grade in both AgNP samples attenuated their toxic effect toward living cells. However, AgNP@GT proved less prone to aggregation thus retained a degree of its toxicity.Conclusion: To our knowledge, this is the first systematic examination regarding AgNP aggregation behavior with simultaneous measurements of its effect on biological activity. We showed that nanoparticle behavior in complex systems can be estimated by simple compounds like sodium chloride and glutamine. Electrostatic stabilization might not be suitable for biomedical AgNP applications, while green synthesis approaches could offer new frontiers to preserve nanoparticle toxicity by enhancing colloidal stability. The importance of properly selected synthesis methods must be emphasized as they profoundly influence colloidal stability, and therefore biological activity. Keywords: colloidal stability, green synthesis, antimicrobial activity, cytotoxicity &nbsp