Two-photon induced responsive f-f emissive detection of Cyclin A with a europium-chelating peptide

Responsive linear and two-photon induced europium emissive probes have been synthesised with a tailor made peptide for the detection of Cyclin A, the hypersensitive Eu emission (Eu-2) gave the real time signalling and also enhanced the two-photon absorption cross section from 12 GM to 68 GM after Cyclin A binding.     

Liquid chromatography-tandem mass spectrometry analysis of 17α-trenbolone, 17β-trenbolone and trendione in airborne particulate matter

Trenbolone acetate (TbA) is a potent synthetic anabolic steroid that was approved by the FDA as a growth promoter in beef cattle in 1987. Given the endocrine-modulating activity of TbA and its metabolites in all vertebrates, a sensitive and reliable analytical method is needed to detect TbA and related residues in environmental matrices. We have developed a method that incorporates solid phase extraction and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the simultaneous determination of the three major TbA metabolites (trendione, 17β-trenbolone, 17α-trenbolone) in total suspended particulate matter (TSP) samples. Sample preparation involved pressurized liquid extraction followed by cleanup on solid-phase extraction cartridges. The procedure was optimized to obtain maximum recovery and minimum signal suppression/enhancement from matrix effects. Analytes were separated with a Phenomenex Gemini-NX C18 analytical column (150 mm × 2.0 mm, 3 μm particle size) using an aqueous methanol gradient at a flow rate of 0.2 mL/min. Column effluent underwent positive electrospray ionization (ESI). Two or more diagnostic product ions were acquired from analyte specific precursor ions for unambiguous confirmation and quantification. The method detection limit was 3.27-4.87 ng/g of particulate matter (PM). Method accuracy, determined with analyte recoveries, ranged between 68% and 117%, and method precision, expressed as relative standard deviation, was below 15% at spiked levels of 6.67, 33.3, and 167 ng/g PM. Analysis of TSP samples demonstrated the presence of the target species associated with PM in the vicinity of beef cattle feeding operations.     

On the convergence of the ensemble Kalman filter

Convergence of the ensemble Kalman filter in the limit for large ensembles to the Kalman filter is proved. In each step of the filter, convergence of the ensemble sample covariance follows from a weak law of large numbers for exchangeable random variables, the continuous mapping theorem gives convergence in probability of the ensemble members, and L ^p bounds on the ensemble then give L ^p convergence.     

Exchange-mediated contrast in CEST and spin-lock imaging

Purpose

Magnetic resonance images of biological media based on chemical exchange saturation transfer (CEST) show contrast that depends on chemical exchange between water and other protons. In addition, spin–lattice relaxation rates in the rotating frame (R_1ρ) are also affected by exchange, especially at high fields, and can be exploited to provide novel, exchange-dependent contrast. Here, we evaluate and compare the factors that modulate the exchange contrast for these methods using simulations and experiments on simple, biologically relevant samples.

Methods

Simulations and experimental measurements at 9.4 T of rotating frame relaxation rate dispersion and CEST contrast were performed on solutions of macromolecules containing amide and hydroxyl exchanging protons.

Results

The simulations and experimental measurements confirm that both CEST and R_1ρ measurements depend on similar exchange parameters, but they manifest themselves differently in their effects on contrast. CEST contrast may be larger in the slow and intermediate exchange regimes for protons with large resonant frequency offsets (e.g. > 2 ppm). Spin-locking techniques can produce larger contrast enhancement when resonant frequency offsets are small (< 2 ppm) and exchange is in the intermediate-to-fast regime. The image contrasts scale differently with field strength, exchange rate and concentration.

Conclusion

CEST and R_1ρ measurements provide different and somewhat complementary information about exchange in tissues. Whereas CEST can depict exchange of protons with specific chemical shifts, appropriate R_1ρ-dependent acquisitions can be employed to selectively portray protons of specific exchange rates.     

Synthesis and molecular structure of a perfluorinated pyridyl carbanion

Reaction of pentafluoropyridine with sodium nitromethanide allowed the isolation and characterisation of the first perfluorinated pyridyl carbanion system, sodium nitrobis(perfluoropyridin-4-yl)methanide, by X-ray crystallography.     

Peptoids with Antibiofilm Activity against the Gram Negative Obligate Anaerobe,Fusobacterium nucleatum

Peptoids (oligo N-substituted glycines) are peptide analogues, which can be designed to mimic host antimicrobial peptides, with the advantage that they are resistant to proteolytic degradation. Few studies on the antimicrobial efficacy of peptoids have focused on Gram negative anaerobic microbes associated with clinical infections, which are commonly recalcitrant to antibiotic treatment. We therefore studied the cytotoxicity and antibiofilm activity of a family of peptoids against the Gram negative obligate anaerobe Fusobacterium nucleatum, which is associated with infections in the oral cavity. Two peptoids, peptoid 4 (NaeNpheNphe)4 and peptoid 9 (NahNspeNspe)₃ were shown to be efficacious against F. nucleatum biofilms at a concentration of 1 μM. At this concentration, peptoids 4 and 9 were not cytotoxic to human erythrocytes or primary human gingival fibroblast cells. Peptoids 4 and 9 therefore have merit as future therapeutics for the treatment of oral infections.     

Measurement of the nucleon structure function F2 in muon-iron interactions at 120,250 and 280 GeV

A measurement of the nucleon structure function F₂ on iron is presented. The data cover a kinematic range of $\text{3.25 ? Q}{}^2\text{? 200}\text{GeV}{}^2\text{and}\text{0.05 ? x ? 0.65}$. The data clearly show scaling violation. Fits in leading-order QCD have been made and values for the scale breaking parameter λ are given.     

Semiclassical expanding discrete space-times

Given the close ties between general relativity and geometry one might reasonably expect that quantum effects associated with gravitation might also be tied to the geometry of space-time, namely, to some sort of discreteness in space-time itself. In particular we suppose space-time to consist of a discrete lattice of points rather than the usual continuum. Since astronomical evidence seems to suggest that the universe is expanding, we also demand that the lattice is expanding. Some of the implications of such a model are that the proton should presently be stable, and the universe should be closed although the mechanism for closure is quantum mechanical.     

Two general routes to 1,4-disubstituted-2,3,4,5-tetrahydro- 1H-3-benzazepines

[structure] Two general routes to 1,4-disubstituted-2,3,4, 5-tetrahydro-1H-3-benzazepines are described. Both routes utilize an appropriately functionalized phenethylamino alcohol as the penultimate intermediate: the first route makes use of the reductive amination of a benzyl alkyl ketone with alpha-(aminomethyl)benzyl alcohol, while the second route utilizes the addition of a Grignard reagent to the oxazolidine derived from a substitued phenylacetaldehyde and alpha-(methylaminomethyl)benzyl alcohol. In all cases studied, the cis-1,4-disubstituted-2,3,4, 5-tetrahydro-1H-3-benzazepine was obtained as the major product.