Monitoring of glass derivatization with pulsed force mode atomic force microscopy

Non-specific adsorption of proteins at solid/liquid interfaces is a major problem in the use of synthetic biomaterials and in ultrasensitive detection methods. Grafting surfaces with a dense layer of poly(ethylene glycol) (PEG) or other polymers is a most widely used strategy to solve this task. While such modified surfaces have been characterized by their ability to resist protein adsorption, the polymer layers themselves have rarely been studied in fine detail. Atomic force microscopy (AFM) using the pulsed force mode (PFM), is an ideal technique to investigate structural features and physiochemical properties of surfaces because topology and adhesion are simultaneously detected with high lateral resolution. In the present study, PFM-AFM was applied to thoroughly characterize different stages of glass derivatization, up to the formation of a dense PEG layer. Lateral inhomogeneities in topology and/or adhesion were observed at all stages before PEG attachment. The covalently bound PEG, however, was seen to form a densely packed monolayer with maximal thickness, smooth surface, and weak adhesion. Thus, PFM-AFM appears to be a valuable tool for the characterization of protein-repelling surfaces in solution.     

Promoting occupational health in secondary schools through virtual patients

Adolescents with asthma or allergies do not consider their disease when making their career choice. Therefore the aim of this project was to sensitize secondary school students for occupational diseases before they start working.     

Why Distinctive Information Reduces False Memories: Evidence for Both Impoverished Relational-Encoding and Distinctiveness Heuristic Accounts.

Two accounts explain why studying pictures reduces false memories within the Deese-Roediger-McDermott paradigm (J. Deese, 1959; H. L. Roediger & K. B. McDermott, 1995). The impoverished relational-encoding account suggests that studying pictures interferes with the encoding of relational information, which is the primary basis for false memories in this paradigm. Alternatively, the distinctiveness heuristic assumes that critical lures are actively withheld by the use of a retrieval strategy. When participants were given inclusion recall instructions to report studied items as well as related items, they still reported critical lures less often after picture encoding than they did after word encoding. As the impoverished relational-encoding account suggests, critical lures appear less likely to come to mind after picture encoding than they do after word encoding. However, the results from a postrecall recognition test provide evidence in favor of the distinctiveness heuristic. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serotonin transporter genotype and depressive symptoms moderate effects of nicotine on spatial working memory.

Smokers may use nicotine to self-medicate for situation-specific or person-specific cognitive or affective deficits. Although evidence suggests that nicotine replacement therapy (NRT), relative to placebo, enhances spatial working memory (SWM) in smoking-abstinent smokers with schizophrenia, the extent to which NRT may be helpful in attenuating abstinence-related SWM in other groups with deficits in SWM is unknown. Depressive symptoms are associated with both tobacco smoking and deficits in SWM. Previous studies have found that smoking abstinence increases depressive affect and depression-related hemispheric asymmetries in brain activation. Although the serotonin neurotransmitter system is closely associated with depression and the effects of nicotine, the authors are not aware of any studies that have evaluated the possible role of individual differences in serotonin transporter (5-HTT) genotype and depressive symptoms as moderators of the effects of NRT on SWM. Thus, the current study assessed the effects of NRT (nicotine patch) on SWM in relation to: (1) depressive traits and (2) 5-HTT genotype. Smoking-deprived habitual smokers (N = 64) completed the dot recall test of SWM during counterbalanced and double-blind nicotine and placebo testing sessions. There was a marginal overall effect of NRT on SWM. More importantly, NRT enhanced SWM in 5-HTT short allele carriers, relative to those with two long alleles, and this enhancement in short-allele carriers was greater for individuals with higher levels of depressive symptoms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Toxicity of Carbon Nanomaterials—Towards Reliable Viability Assessment via New Approach in Flow Cytometry

The scope of application of carbon nanomaterials in biomedical, environmental and industrial fields is recently substantially increasing. Since in vitro toxicity testing is the first essential step for any commercial usage, it is crucial to have a reliable method to analyze the potentially harmful effects of carbon nanomaterials. Even though researchers already reported the interference of carbon nanomaterials with common toxicity assays, there is still, unfortunately, a large number of studies that neglect this fact. In this study, we investigated interference of four bio-promising carbon nanomaterials (graphene acid (GA), cyanographene (GCN), graphitic carbon nitride (g-C₃N₄) and carbon dots (QCDs)) in commonly used LIVE/DEAD assay. When a standard procedure was applied, materials caused various types of interference. While positively charged g-C₃N₄ and QCDs induced false results through the creation of free agglomerates and intrinsic fluorescence properties, negatively charged GA and GCN led to false signals due to the complex quenching effect of the fluorescent dye of a LIVE/DEAD kit. Thus, we developed a new approach using a specific gating strategy based on additional controls that successfully overcame all types of interference and lead to reliable results in LIVE/DEAD assay. We suggest that the newly developed procedure should be a mandatory tool for all in vitro flow cytometry assays of any class of carbon nanomaterials.     

LytR-CpsA-Psr Glycopolymer Transferases: Essential Bricks in Gram-Positive Bacterial Cell Wall Assembly

The cell walls of Gram-positive bacteria contain a variety of glycopolymers (CWGPs), a significant proportion of which are covalently linked to the peptidoglycan (PGN) scaffolding structure. Prominent CWGPs include wall teichoic acids of Staphylococcus aureus, streptococcal capsules, mycobacterial arabinogalactan, and rhamnose-containing polysaccharides of lactic acid bacteria. CWGPs serve important roles in bacterial cellular functions, morphology, and virulence. Despite evident differences in composition, structure and underlaying biosynthesis pathways, the final ligation step of CWGPs to the PGN backbone involves a conserved class of enzymes—the LytR-CpsA-Psr (LCP) transferases. Typically, the enzymes are present in multiple copies displaying partly functional redundancy and/or preference for a distinct CWGP type. LCP enzymes require a lipid-phosphate-linked glycan precursor substrate and catalyse, with a certain degree of promiscuity, CWGP transfer to PGN of different maturation stages, according to in vitro evidence. The prototype attachment mode is that to the C6-OH of N-acetylmuramic acid residues via installation of a phosphodiester bond. In some cases, attachment proceeds to N-acetylglucosamine residues of PGN—in the case of the Streptococcus agalactiae capsule, even without involvement of a phosphate bond. A novel aspect of LCP enzymes concerns a predicted role in protein glycosylation in Actinomyces oris. Available crystal structures provide further insight into the catalytic mechanism of this biologically important class of enzymes, which are gaining attention as new targets for antibacterial drug discovery to counteract the emergence of multidrug resistant bacteria.     

Effects of nicotine on affect are moderated by stressor proximity and frequency, positive alternatives, and smoker status

The Situation x Trait Adaptive Response (STAR) model hypothesizes that nicotine reduces negative and enhances positive affect to a greater degree in situations involving internally driven attention, as when stressor stimuli are distal (past or future), thereby allowing nicotine-primed biasing of attentional processing away from negative and toward positive stimuli. To test this hypothesis, the effects of nicotine were assessed in 64 smokers and 64 never-smokers, half of whom viewed emotionally negative pictures in a no-choice picture attention task that required them to focus on the picture stressors. The other half viewed the same stimuli in a two-choice picture attention task that presented stressor pictures in one visual field and simultaneously presented positive or neutral pictures in the other visual field. Participants received a nicotine patch during one session and a placebo patch during the other session. Nicotine modulated affect only in smokers. In smokers, compared with placebo, nicotine patch reduced negative affect more during the distal periods (between stressors) than during actual stressor exposure and in women reduced negative affect more when the proportion of negative stimuli was low. Nicotine also enhanced positive affect more during distal than proximal stressors. Nicotine tended to reduce eye-gaze at negative pictures, especially when the alternative picture was positive. The overall findings are consistent with the view that nicotine biases attention away from negative stimuli when equally salient positive or benign stimuli are present.     

The effect of thermal treatment on the structure and fine structure of Cu-Zn-Al martensite

The effect of thermal treatment on the structure and fine structure of CU-17.4Zn-13.0Al (at%) matensite has been studied using X-ray powder diffraction and transmission electron microscopy. It has been found that when the directly-quenched M18R₁ martensite is aged at increasing temperatures, the structure parameters andx-parameter tend evidently towards the values of the N18R₁ martensite, while the DO₃-derived long-range order parameterS is not changed substantially. The activation energy of the structure parameter variation process of the 18R₁ martensite during aging has been measured to be 58 kJ mol^–1 (0.60 eV) for the directly-quenched specimen using the X-ray reflection splitting data. The aging kinetics of the step-quenched martensite is much lower compared with the directly-quenched martensite. Moreover, the anti-phase domain size of the step-quenched martensite inherited from the parent phase is much larger than that of the directly-quenched and the aged martensites. Based on our observations the mechanisms of the aging and stabilization of martensite are discussed.