Thermal dissociation of multimeric protein complexes by using nanoelectrospray mass spectrometry

The behavior of macromolecular systems at different temperatures is often crucial to their biological activity and function. While heat-induced changes of individual proteins are readily monitored by a number of spectroscopic methods, changes in noncovalent complexes of biomolecules are more challenging to interpret. Nanoelectrospray mass spectrometry is becoming increasingly powerful in the study of large noncovalent complexes, and here we describe the design, characterization, and application of a novel probe that allows the thermocontrol of the solution in the electrospray capillary. The transition temperature for the unfolding of the protein lysozyme is readily obtained and correlates closely with that measured by fluorescence spectroscopy, thereby demonstrating the validity of this approach. We apply this technique to the study of the 200-kDa complex of the small heat shock protein TaHSP16.9, revealing both its dissociation into suboligomeric species and an increase in its size and polydispersity at elevated temperatures. In contrast, gas-phase activation of this complex is also carried out and yields a dissociation pathway fundamentally different from that observed for thermal activation in solution. As such, this probe allows the study of the reversible heat-induced changes of noncovalent complexes in a biologically relevant manner.     

Premorbid anomalies and risk of schizophrenia and depressive disorders in a birth cohort exposed to prenatal rubella.

In a birth cohort prenatally exposed to rubella, we assessed whether prospectively documented premorbid neuromotor dysfunction, mannerisms, deviant behaviors, and temperament during childhood and adolescence were impaired in cases who developed depressive disorder (DD) relative to rubella-exposed controls and cases who developed schizophrenia spectrum psychosis (SSP). Premorbid neuromotor dysfunction and mannerisms were not increased among DD cases compared to controls or SSP cases. With regard to temperament, approachability was greater in DD cases than in controls and SSP cases. There were numerical increases in the proportions of DD cases with premorbid deviant behaviors compared to controls, but the findings fell short of statistical significance; the proportion of subjects with deviant behaviors in DD cases was similar to that found for SSP. These results indicate that premorbid neuromotor dysfunction and mannerisms may be specific to SSP among major psychiatric disorders in this cohort, and suggest that premorbid deviant behaviors are increased in both DD and SSP. Greater premorbid approachability may be associated with an increased risk of adult DD. Implications of these findings for school psychology are furnished. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fraternity and sorority involvement, social influences, and alcohol use among college students: A prospective examination.

This study used latent growth curve modeling to investigate whether the effects of gender and Greek involvement on alcohol use and problems over the first 2 years of college are best characterized by selection, socialization, or reciprocal influence processes. Three social influences (alcohol offers, social modeling, and perceived norms) were examined as potential mediators of these effects. Undergraduate participants (N = 388) completed self-report measures prior to enrollment and in the spring of their freshmen and sophomore years. Male gender and involvement in the Greek system were associated with greater alcohol use and problems prior to college. Both gender and Greek involvement significantly predicted increases in alcohol use and problems over the first 2 years of college. Cross-domain analyses provided strong support for a mediational role of each of the social influence constructs on alcohol use and problems prior to matriculation, and prematriculation social modeling and alcohol offers mediated relations between Greek involvement and changes in alcohol use over time. Findings suggest that students, particularly men, who affiliate with Greek organizations constitute an at-risk group prior to entering college, suggesting the need for selected interventions with this population, which should take place before or during the pledging process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The formation of an apatite coating on carboxylated polyphosphazenes via a biomimetic process

The biomimetic deposition of an apatite coating on polyphosphazene was investigated. A polyphosphazene having carboxylatophenoxy side groups was synthesized as a candidate polymer with heterogeneous nucleation sites for apatite deposition. Poly[bis(carboxylatophenoxy)phosphazene] (PCPP) was synthesized by a two-step synthetic route involving the synthesis of poly(dichlorophosphazene) (PDP) followed by nucleophilic replacement of the chlorine atoms of PDP with carboxylatophenoxy groups. The surface of the carboxylated polyphosphazene induced the formation of a dense layer of apatite on the surface after incubation in simulated body fluid at 37 °C with an ionic concentration approximately the same as that of human blood plasma. The results suggested an early precipitation of octacalcium phosphate and calcium phosphate intermediates on the surface, both of which are known to promote osteoblast differentiation and proliferation.     

More IMPATIENT: A gridding-accelerated Toeplitz-based strategy for non-Cartesian high-resolution 3D MRI on GPUs

Several recent methods have been proposed to obtain significant speed-ups in MRI image reconstruction by leveraging the computational power of GPUs. Previously, we implemented a GPU-based image reconstruction technique called the Illinois Massively Parallel Acquisition Toolkit for Image reconstruction with ENhanced Throughput in MRI (IMPATIENT MRI) for reconstructing data collected along arbitrary 3D trajectories. In this paper, we improve IMPATIENT by removing computational bottlenecks by using a gridding approach to accelerate the computation of various data structures needed by the previous routine. Further, we enhance the routine with capabilities for off-resonance correction and multi-sensor parallel imaging reconstruction. Through implementation of optimized gridding into our iterative reconstruction scheme, speed-ups of more than a factor of 200 are provided in the improved GPU implementation compared to the previous accelerated GPU code.     

The importance of island surveys in documenting disease-related mortality and Botulism E in Great Lakes colonial waterbirds

Type E Botulism is an important source of mortality for waterbirds on the lower Great Lakes. The purpose of this study was to determine: 1) the spatial distribution of waterbird mortality and 2) if that mortality possibly impacted the breeding colonial waterbird populations in eastern Lake Ontario. Six islands in eastern Lake Ontario, Canada, were searched, July–November, 2004–2009, for dead/moribund waterbirds. Over 6600 dead/dying birds were located; five species accounted for > 98% of the birds found: double-crested cormorant (Phalacrocorax auritus), herring, ring-billed and great black-backed gulls (Larus argentatus, Larus delawarensis, Larus marinus, respectively) and Caspian tern (Hydroprogne caspia). Cormorants accounted for 65–78% of all birds annually. Mortality was greatest in 2005 (7.5%). Most carcasses (91%) were documented on four islands. Most necropsied carcasses (58%, N = 95) were confirmed/suspected to have died from Type E Botulism; it was the only mortality factor identified in all years and in all five main species. These results produced a different guild of affected birds from previous beached bird surveys; virtually no birds that roost on water (loons and waterfowl) were found. Deaths reported here had minimal impact to herring and ring-billed gull, double-crested cormorant and Caspian tern populations nesting in eastern Lake Ontario. However, they accounted for > 100% of the great black-backed gulls breeding there. The species was extirpated from Lake Ontario during the study period. When assessing mortality in aquatic birds, it is crucial to examine off-shore islands, where birds roost, to fully document this critical demographic parameter.     

High-Throughput Analysis of Algal Crude Oils Using High Resolution Mass Spectrometry

Lipid analysis often needs to be specifically optimized for each class of compounds due to its wide variety of chemical and physical properties. It becomes a serious bottleneck in the development of algae-based next generation biofuels when high-throughput analysis becomes essential for the optimization of various process conditions. We propose a high-resolution mass spectrometry-based high-throughput assay as a ‘quick-and-dirty’ protocol to monitor various lipid classes in algal crude oils. Atmospheric pressure chemical ionization was determined to be most effective for this purpose to cover a wide range of lipid classes. With an autosampler-LC pump set-up, we could analyze algal crude samples every one and half minutes, monitoring several lipid species such as TAG, DAG, squalene, sterols, and chlorophyll a. High-mass resolution and high-mass accuracy of the orbitrap mass analyzer provides confidence in the identification of these lipid compounds. MS/MS and MS3 analysis could be performed in parallel for further structural information, as demonstrated for TAG and DAG. This high-throughput method was successfully demonstrated for semi-quantitative analysis of algal oils after treatment with various nanoparticles.     

Field-Assisted Sintering of Nanocrystalline Titanium Nitride

Nanosized TiN powder was densified via field-assisted sintering at temperatures of 1150°–1350°C and a pressure of 66 MPa under vacuum. A maximum relative density of ∼97% and a maximum mean grain size of 150–200 nm were obtained. Densification and microstructural evolution have been discussed, in terms of superplasticity and electric-field effects.     

The mechanical behaviour of a cross-weave ceramic matrix composite

In order to find out whether or not a cross-weave ceramic composite, graphite fibre/SiC matrix, would be prone to fatigue failure, tests in pulsating tension and pulsating compression have been carried out with the weave oriented in the 0/90 configuration. Both types of testing (at fairly high fractions of the ultimate monotonic failure load) cause creep strain, which is frequency dependent in tension, and ultimately complete failure can occur. Damage in pulsating tension is found to consist of cumulative microcracking and spalling, with the final failure mechanism broadly similar to that in monotonic deformation. Damage in pulsating compression appears dominated by delamination.