A diminished role for hydrogen bonds in antifreeze protein binding to ice

The most abundant isoform (HPLC-6) of type I antifreeze protein (AFP1) in winter flounder is a 37-amino-acid-long, alanine-rich, alpha-helical peptide, containing four Thr spaced 11 amino acids apart. It is generally assumed that HPLC-6 binds ice through a hydrogen-bonding match between the Thr and neighboring Asx residues to oxygens atoms on the {2021} plane of the ice lattice. The result is a lowering of the nonequilibrium freezing point below the melting point (thermal hysteresis). HPLC-6, and two variants in which the central two Thr were replaced with either Ser or Val, were synthesized. The Ser variant was virtually inactive, while only a minor loss of activity was observed in the Val variant. CD, ultracentrifugation, and NMR studies indicated no significant structural changes or aggregation of the variants compared to HPLC-6. These results call into question the role of hydrogen bonds and suggest a much more significant role for entropic effects and van der Waals interactions in binding AFP to ice.     

Fate of C-triclocarban in biosolids-amended soils

Triclocarban (TCC) is an antibacterial compound commonly detected in biosolids at parts-per-million concentrations. Approximately half of the biosolids produced in the United States are land-applied, resulting in a systematic release of TCC into the soil environment. The extent of biosolids-borne TCC environmental transport and potential human/ecological exposures will be greatly affected by its bioavailability and the rate of degradation in amended soils. To investigate these factors, radiolabeled TCC (¹⁴C-TCC) was incorporated into anaerobically digested biosolids, amended to two soils, and incubated under aerobic conditions. The evolution of ¹⁴CO2 (biodegradation) and changes in chemical extractability (bioavailability) was measured over time. Water extractable TCC over the study period was low and significantly decreased over the first 3 weeks of the study (from 14% to 4% in a fine sand soil and from 3 to < 1% in a silty clay loam soil). Mineralization (i.e. ultimate degradation), as measured by evolution of ¹⁴CO₂, was < 4% over 7.5 months. Methanol extracts of the amended soils were analyzed by radiolabel thin-layer chromatography (RAD-TLC), but no intermediate degradation products were detected. Approximately 20% and 50% of the radioactivity in the amended fine sand and silty clay loam soils, respectively, was converted to bound residue as measured by solids combustion. These results indicate that biosolids-borne TCC becomes less bioavailable over time and biodegrades at a very slow rate.     

Measured physicochemical characteristics and biosolids-borne concentrations of the antimicrobial Triclocarban (TCC)

Triclocarban (TCC) is an active ingredient in antibacterial bar soaps, a common constituent of domestic wastewater, and the subject of recent criticism by consumer advocate groups and academic researchers alike. Activated sludge treatment readily removes TCC from the liquid waste stream and concentrates the antimicrobial in the solid fraction, which is often processed to produce biosolids intended for land application. Greater than half of the biosolids generated in the US are land-applied, resulting in a systematic release of biosolids-borne TCC into the terrestrial and, potentially, the aquatic environment. Multiple data gaps in the TCC literature (including basic physicochemical properties and biosolids concentrations) prevent an accurate, quantitative risk assessment of biosolids-borne TCC. We utilized the USEPA Office of Prevention, Pesticides, and Toxic Substances (OPPTS) harmonized test guidelines to measure TCC solubility and log K_ow values as 0.045 mg L⁻¹ and 3.5, respectively. The measured physicochemical 2 properties differed from computer model predictions. The mean concentration of TCC in 23 biosolids representative of multiple sludge processing methods was 19 ± 11 mg kg⁻¹.     

Social comparison processes and academic achievement: The dependence of the development of self-evaluations on friends' performance.

The purpose of this study was to examine the role of social comparison processes in children's self-evaluations. Children's aptitudes to gauge their self-evaluations of their abilities in school activities (i.e., perceived academic competence) on the basis of their actual performance depended on how well their reciprocated friends performed academically. Self-evaluations of performance were not affected when the comparison was based on levels of nonreciprocated friends' achievement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Timing Recovery in Digital Subscriber Loops Using Baud-Rate Sampling

Sampled-data techniques are the most practical means of obtaining the necessary signal processing functions for timing recovery in the VLSI implementation of a digital subscriber loop transceiver. The sampled-data timing recovery techniques described in this paper are applicable to both echo cancellation and time-compression multiplexing systems. Timing recovery using baud-rate sampling in conjunction with a special pulse-shaping and timing function fulfills all the objectives for timing recovery in this application. It recovers a timing phase that has minimum precursor intersymbol interference, and makes possible the combination of decision feedback equalizer and echo canceler, reducing the convergence time and increasing the step size. The pulse-shaping function can be performed either in the transmitter by means of digital coding, or in the receiver by means of analog filtering. In the latter case, the transmitted pulse is compatible with more conventional approaches. The proposed partial-response line coding, a special form of AMI coding, is less susceptible to line impairments if detected as a two-level signal. Performance by analysis, simulation, and experimental measurements is reported on a variety of cable configurations, some including bridged taps. Analysis of jitter performance leads to design techniques for reducing the jitter magnitude.     

Is knowledge of famous people disproportionately impaired with patients with early and questionable Alzheimer's disease?

Twenty-two patients with early dementia of Alzheimer's type (DAT) and 31 controls were administered tests of person-specific semantics (Experiment 1). DAT patients were impaired on all test components. In Experiment 2, 31 DAT patients, 28 questionable DAT (QDAT) patients, and 42 controls were administered the Graded Naming Test (GNT) and the newly designed Graded Faces Test (GFT), matched for difficulty with the GNT. DAT patients were impaired throughout but showed an advantage for naming objects over faces. The QDAT patients were impaired on the GFT only. Of the 7 QDAT patients who evolved to DAT within 1-2 years, 6 showed initial impairment on the GFT, whereas 17 of the nonconverters scored normally on the GFT. Results suggest greater and earlier vulnerability of person knowledge than general semantic knowledge in DAT. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Quantitative evaluation of autoradiographs by X-ray spectroscopy.

Measurements of mass of developed silver in autoradiograms have been made using X-ray microanalysis. This procedure has been applied to a scanning electron microscopic study of protease-induced cell stimulation in 3H-thymidine-labelled bladder tissues in vitro. Differences in silver concentrations over individual nuclei were demonstrated by X-ray analysis and quantitative data was obtained showing an increased rate of 3H-thymidine incorporation in protease-treated cultures. The initial evidence indicates that X-ray microanalysis could provide a potentially useful quantitative procedure for autoradiography.