Operating systems and network protocols for wireless sensor networks

Sensor network protocols exist to satisfy the communication needs of diverse applications, including data collection, event detection, target tracking and control. Network protocols to enable these services are constrained by the extreme resource scarcity of sensor nodes-including energy, computing, communications and storage-which must be carefully managed and multiplexed by the operating system. These challenges have led to new protocols and operating systems that are efficient in their energy consumption, careful in their computational needs and miserly in their memory footprints, all while discovering neighbours, forming networks, delivering data and correcting failures.     

Heterogeneous single-molecule diffusion in one-, two-, and three-dimensional microporous coordination polymers: directional, trapped, and immobile guests

The diffusion of individual Nile red molecules in three different crystalline microporous coordination polymers (MCPs) is visualized with single-molecule fluorescence microscopy. By localizing molecules with high spatial resolution, the trajectories of the diffusing dyes are reconstructed with nanometer-scale precision. A detailed analysis of these tracks reveals different dynamics and guest-host interactions in each crystal as well as distinct motion types within the same system, suggesting the presence of structural heterogeneities in local environments.     

Cancer prognostics by direct detection of p53-antibodies on gold surfaces by impedance measurements

The identification and measurement of biomarkers is critical to a broad range of methods that diagnose and monitor many diseases. Serum auto-antibodies are rapidly becoming interesting targets because of their biological and medical relevance. This paper describes a highly sensitive, label-free approach for the detection of p53-antibodies, a prognostic indicator in ovarian cancer as well as a biomarker in the early stages of other cancers. This approach uses impedance measurements on gold microelectrodes to measure antibody concentrations at the picomolar level in undiluted serum samples. The biosensor shows high selectivity as a result of the optimization of the epitopes responsible for the detection of p53-antibodies and was validated by several techniques including microcontact printing, self-assembled-monolayer desorption ionization (SAMDI) mass spectrometry, and adhesion pull-off force by atomic force microscopy (AFM). This transduction method will lead to fast and accurate diagnostic tools for the early detection of cancer and other diseases.     

Azido and Diazarinyl Analogues of Bis‐Tyrphostin as Asymmetrical Inhibitors of Dynamin GTPase

Probing the dynamin binding site : Bis‐tyrphostin ( 1 , Bis‐T), is a potent inhibitor of the phospholipid‐stimulated GTPase activity of dynamin I. Analogues of Bis‐T have significant potential as a biological probes for the dissection of endocytic pathways. Bis‐T‐derived compounds were synthesised and evaluated for their ability to inhibit the GTPase activity of dynamin I. Two analogues ( 23 and 24 ) represent the first asymmetrically substituted Bis‐T analogues to retain dynamin inhibition.

     

Nano-LC FTICR tandem mass spectrometry for top-down proteomics: routine baseline unit mass resolution of whole cell lysate proteins up to 72 kDa

Current high-throughput top-down proteomic platforms provide routine identification of proteins less than 25 kDa with 4-D separations. This short communication reports the application of technological developments over the past few years that improve protein identification and characterization for masses greater than 25 kDa. Advances in separation science have allowed increased numbers of proteins to be identified, especially by nanoliquid chromatography (nLC) prior to mass spectrometry (MS) analysis. Further, a goal of high-throughput top-down proteomics is to extend the mass range for routine nLC MS analysis up to 80 kDa because gene sequence analysis predicts that ~70% of the human proteome is transcribed to be less than 80 kDa. Normally, large proteins greater than 50 kDa are identified and characterized by top-down proteomics through fraction collection and direct infusion at relatively low throughput. Further, other MS-based techniques provide top-down protein characterization, however at low resolution for intact mass measurement. Here, we present analysis of standard (up to 78 kDa) and whole cell lysate proteins by Fourier transform ion cyclotron resonance mass spectrometry (nLC electrospray ionization (ESI) FTICR MS). The separation platform reduced the complexity of the protein matrix so that, at 14.5 T, proteins from whole cell lysate up to 72 kDa are baseline mass resolved on a nano-LC chromatographic time scale. Further, the results document routine identification of proteins at improved throughput based on accurate mass measurement (less than 10 ppm mass error) of precursor and fragment ions for proteins up to 50 kDa.     

Sensitive localized surface plasmon resonance multiplexing protocols

Herein are reported two new protocols to obtain different zones of localized surface plasmon resonance (LSPR) gold nanostructures on single glass substrate by using a vacuum evaporation technique followed by a high-temperature annealing (550 °C). The thickness of the gold film, considered as the essential parameter to determine specific LSPR properties, is successfully modulated. In the first protocol, a metal mask is integrated onto the glass substrate during vacuum evaporation to vary the gold film thickness by a "shadowing effect", while in the second protocol several evaporation cycles (up to four cycles) at predefined areas onto the single substrate are performed. The resulting gold-modified samples are characterized using a transmission UV-vis extinction optical setup and scanning electron microscopy (SEM). The size distribution histograms of nanoparticles are also acquired. By employing the first protocol, thanks to the presence of different zones of gold nanoparticles on a single substrate, optimized LSPR responses to different (bio)functionalization zones are rapidly screened. Independently, the second protocol exhibited an excellent correlation between the nominative evaporated gold film thickness, gold nanoparticle sizes, and plasmonic properties (resonant wavelength and peak amplitude). Such substrates are further used in the construction of LSPR immunosensors for the detection of atrazine herbicide.     

Chiral analysis of chloro intermediates of methylamphetamine by one-dimensional and multidimentional NMR and GC/MS

Impurity profiling and classification of abused drugs using chiral analytical techniques is of particular interest and importance because of the additional information obtained from this approach. When these methods are applied to the synthesis of illicitly used substances, they can supply valuable information about the conditions/chemicals used in the synthesis. We have applied GC and NMR methods to the study of intermediates found in methylamphetamine manufacture with the aim of linking the intermediates to the ephedrine/pseudoephedrine starting materials. Therefore, determination of the stereochemical makeup within samples of forensic interest is important giving further specific information to the analyst. This study investigates the stereochemical course of the Emde synthesis of methylamphetamine with particular focus on intermediate formation via the chlorination of ephedrine and pseudoephedrine enantiomers. The configurations of these chloro-phenethylamines were determined by 1D and 2D NMR analysis, and thereafter, the GC/MS analysis was carried out. We have shown here that chlorination of the ephedrine/pseudoephedrine compounds occurs via inversion (S(N)2) and retention (S(N)i) of configuration around the α carbon and mixture of diastereoisomers (chloroephedrine and chloropseudoephedrine) were formed, with the ratio of the resulting compounds dependent on the precursors used. The preparation and analytical properties of these intermediate standards provide data for laboratories interested in the stereochemical analysis of methylamphetamine intermediates such as forensic/law enforcement, and illustrate the value of using a combination of analytical methodology.     

Robust analysis of the yeast proteome under 50 kDa by molecular-mass-based fractionation and top-down mass spectrometry

As the process of top-down mass spectrometry continues to mature, we benchmark the next installment of an improving methodology that incorporates a tube-gel electrophoresis (TGE) device to separate intact proteins by molecular mass. Top-down proteomics is accomplished in a robust fashion to yield the identification of hundreds of unique proteins, many of which correspond to multiple protein forms. The TGE platform separates 0-50 kDa proteins extracted from the yeast proteome into 12 fractions prior to automated nanocapillary LC-MS/MS in technical triplicate. The process may be completed in less than 72 h. From this study, 530 unique proteins and 1103 distinct protein species were identified and characterized, thus representing the highest coverage to date of the Saccharomyces cerevisiae proteome using top-down proteomics. The work signifies a significant step in the maturation of proteomics based on direct measurement and fragmentation of intact proteins.     

Speciation and quantitative mapping of metal species in microbial biofilms using scanning transmission X-ray microscopy

A scanning transmission X-ray microscope illuminated with synchrotron light was used to investigate the speciation and spatial distributions of metals in a microbial biofilm cultivated from river water. Metal 2p absorption edge signals were used to provide metal speciation (through shapes of the absorption spectra) and quantitative spatial distributions of the metal species. This paper presents sample data and describes methods for extracting quantitative maps of metal species from image sequences recorded in the region of the metal 2p edges. Comparisons were made with biochemical characterization of the same region using images recorded at the C 1s and O 1s edges. The method is applied to detailed quantitative analysis of ferrous and ferric iron in a river biofilm, in concert with mapping Ni(II) and Mn(II) species in the same region. The distributions of the metal species are discussed in the context of the biofilm structure. These results demonstrate that soft X-ray STXM measurements at the metal 2p absorption edges can be used to speciate metals and to provide quantitative spatial distribution maps for metal species in environmental samples with 50 nm spatial resolution.     

Mysterious outbreaks of gastrointestinal illness associated with burritos supplied through school lunch programs

From October 1997 through March 1998, three outbreaks of gastrointestinal illness among school children were linked to company A burritos. In September 1998, a similar outbreak occurred in three North Dakota schools following lunches that included company B burritos. We conducted an investigation to determine the source of the North Dakota outbreak, identify other similar outbreaks, characterize the illness, and gather evidence about the cause. The investigation included epidemiologic analyses, environmental investigation, and laboratory analyses. In North Dakota, a case was defined as nausea, headache, abdominal cramps, vomiting, or diarrhea after lunch on 16 September 1998. Case definitions varied in the other states. In North Dakota, 504 students and staff met the case definition; predominant symptoms were nausea (72%), headache (68%), abdominal cramps (54%), vomiting (24%), and diarrhea (16%). The median incubation period was 35 min and median duration of illness was 6 h. Eating burritos was significantly associated with illness (odds ratio, 2.6; 95% confidence interval, 1.6 to 4.2). We identified 16 outbreaks that occurred in seven states from October 1997 through October 1998, affecting more than 1,900 people who ate burritos from two unrelated companies. All tortillas were made with wheat flour, but the fillings differed, suggesting that tortillas contained the etiologic agent. Results of plant inspections, tracebacks, and laboratory investigations were unrevealing. More than two million pounds of burritos were recalled or held from distribution. The short incubation period, symptoms, and laboratory data suggest that these outbreaks were caused by an undetected toxin or an agent not previously associated with this clinical syndrome. Mass psychogenic illness is an unlikely explanation because of the large number of sites where outbreaks occurred over a short period, the similarity of symptoms, the common food item, the lack of publicity, and the link to only two companies. A network of laboratories that can rapidly identify known and screen for unknown agents in food is a critical part of protecting the food supply against natural and intentional contamination.