Visualization of vesicle transport along and between distinct pathways in neurites of living cells

Trafficking of secretory vesicles along neurites of PC12 cells was visualized by 2D and 3D real-time imaging using fluorescence microscopy. Vesicle motion along distinct pathways was directly seen. From an overlay of individual pathways, the underlying cytoskeletal filament could be imaged at a subwavelength resolution. Continuous vesicle transport was interrupted by periods of diffusive motion with concomitant pathway changes. Statistical analysis shows that such interruptions were distributed stochastically along the filament, indicating a limited processivity of motor proteins also in a cellular context. Periods of diffusive motion facilitated the interaction with actively transported vesicles. Frequent associations and dissociations of vesicles have been observed consistently, pointing to a functional relevance of vesicle cotransport.     

Burdens of mercury in residents of Temirtau, Kazakhstan: I: Hair mercury concentrations and factors of elevated hair mercury levels

Mercury (Hg) is released either naturally in the environment or by anthropogenic activities. During its global circulation, Hg presents in a diversity of chemical forms and transforms between each other. Among Hg species, methylmercury (MeHg) is readily absorbed by humans via the aquatic food chain and thus it is very neurotoxic to exposed populations including fetuses due to perinatal exposure. In 2005, a survey was carried out in Temirtau, an Hg-contaminated site in North Central Kazakhstan, to investigate Hg concentrations in the hair samples of the residents and the relationship between Hg exposure levels and the related factors. Among the 289 hair samples, Hg concentrations ranged from 0.009 to 5.184 µg/g with a mean of 0.577 µg/g. Nearly 17% of the population exceeded 1 µg/g for hair Hg, which corresponds to the reference of dose (RfD) 0.1 µg/kg body weight/day developed by the United States Environmental Protection Agency (USEPA). Subgroups of males, people aged over 45 and fishermen or anglers were found to have elevated Hg exposure levels in their hair. A positive correlation was found between Hg concentrations in hair and frequencies of river fish consumption. As a result, the finding that people were exposed to high levels of Hg was expected due to the frequent consumption of fish caught from the polluted River Nura or the neighbouring lakes. A regression model showed that approximately 41% of variance of Hg concentrations in the study population's hair was attributed to the variables of gender, residential location, age and fishery occupation. The model implied that demographic characteristics together with dietary behaviour should be taken into account in studies associated with Hg exposure risk, in order to clearly define the group potentially sensitive to Hg exposure.     

The hydroxycinnamic acid content of barley and brewers’ spent grain (BSG) and the potential to incorporate phenolic extracts of BSG as antioxidants into fruit beverages

The hydroxycinnamic acid (HA) content of starting barley for brewers’ spent grains (BSG), whole BSG and phenolic extracts from BSG was measured using high performance liquid chromatography (HPLC) and correlated with antioxidant potential. The effect of BSG phenolic extracts on antioxidant activity of fruit beverages was also assessed (using the total phenolic content (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays). The concentration of HA present in barley extract and BSG was in the order of ferulic acid (FA), p-coumaric acid (p-CA) derivatives, FA derivatives, p-CA, caffeic acid (CA) and CA derivatives. Results suggested that brewing and roasting decreased the HA content. Antioxidant activity was significantly (P < 0.05) correlated with caffeic acid (R² = 0.8309) and total HA (R² = 0.3942) concentrations. Addition of extracts to fruit beverages resulted in a significant (P < 0.05) increase in antioxidant activity of cranberry juice, measured by the FRAP assay. In vitro digestion significantly (P < 0.05) reduced TPC, DPPH and FRAP activity of the fruit beverages.     

Optical Control of Transcription: Genetically Encoded Photoswitchable Variants of T7 RNA Polymerase

Light-sensing protein domains that link an exogenous light signal to the activity of an enzyme have attracted much attention for the engineering of new regulatory mechanisms into proteins and for studying the dynamic behavior of intracellular reactions and reaction cascades. Light–oxygen–voltage (LOV) photoreceptors are blue-light-sensing modules that have been intensely characterized for this purpose and linked to several proteins of interest. For the successful application of these tools, it is crucial to identify appropriate fusion strategies for combining sensor and enzyme domains that sustain activity and light-induced responsivity. Terminal fusion of LOV domains is the natural strategy; however, this is not transferrable to T7 RNA polymerase because both of its termini are involved in catalysis. It is shown herein that it is possible to covalently insert LOV domains into the polymerase protein, while preserving its activity and generating new light-responsive allosteric coupling.     

Continuous Process for the Production of Hexafluoroisopropanol

There has been a renewed interest in the design of catalytic reactors to reduce transport limitations. Towards this goal, a novel single fluid-phase recirculating packed bed reactor concept has been developed and demonstrated for the hydrogenation of hexafluoroacetone to hexafluoroisopropanol, a precursor to Sevoflurane, used as an inhalation anesthetic, in the presence of a Ni/Al₂O₃ catalyst.

     

Continuous Process for the Production of Hexafluoroisopropanol

There has been a renewed interest in the design of catalytic reactors to reduce transport limitations. Towards this goal, a novel single fluid-phase recirculating packed bed reactor concept has been developed and demonstrated for the hydrogenation of hexafluoroacetone to hexafluoroisopropanol, a precursor to Sevoflurane, used as an inhalation anesthetic, in the presence of a Ni/Al₂O₃ catalyst.     

Electron Donation–Backdonation and the Rules of Catalytic Promotion

The rules of classical and electrochemical promotion of catalysis, which allow for the prediction of the effect of electropositive and electronegative promoters on catalytic rate and selectivity on the basis of the catalytic reaction kinetics, are compared with experiment for all relevant catalytic studies during the last two decades and are used to show that the rate versus catalyst work function dependence always parallels the rate versus electron donor reactant dependence. This generalized rule is rationalized both by considering the interaction of the electric field in the effective double layer at the metal catalyst–gas interface with the electric dipoles of the adsorbed reactants and also by considering the electron donation–backdonation between the adsorbed reactants and the catalyst. This generalized promotional rule allows for promoter selection on the basis of the reaction kinetics.     

A MALDI MS Investigation of the Lysophosphatidylcholine/Phosphatidylcholine Ratio in Human Spermatozoa and Erythrocytes as a Useful Fertility Marker

The human spermatozoa membrane is characterized by a unique fatty acyl composition with significant amounts of highly unsaturated fatty acids, particularly docosahexaenoic acid (22:6), whereby phosphatidylcholine (PtdCho) (16:0/22:6) is the most abundant glycerophospholipid. The large amount of highly unsaturated fatty acyl residues is crucial for the fluidity of the membrane and, therefore, the successful fertilization process. Consequently, however, the spermatozoa are very sensitive to reactive oxygen species (ROS) that are generated under conditions of “oxidative stress” and key players in many pathological conditions. Lipid oxidation of the sperm membrane is accompanied by the loss of the oxidatively modified unsaturated residue (normally in the sn-2 position) and the generation of saturated lysophosphatidylcholine (LysoPtdCho). Although other lysolipids are also generated, LysoPtdCho is the “marker” lipid of choice due to the high abundance of PtdCho. In particular, obesity (body mass index >30 kg/m²) is characterized by increased ROS generation and negatively affects the reproductive potential. We will show here that the LysoPtdCho/PtdCho ratio can be easily determined by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). The data found do correlate with clinical markers of sperm quality. A very interesting aspect is that the LysoPtdCho/PtdCho ratios determined in the spermatozoa extracts correlate with the LysoPtdCho/PtdCho values determined in the organic extracts of erythrocytes. Thus, there is no absolute need for a sperm investigation, but an estimation of the fertilizing ability of the corresponding male could be also made directly from the blood which is more readily available than the spermatozoa.