Multicomponent synthesis of 3-heteroarylpropionic acids

A four component one-pot procedure (4-MC) was developed to assemble 3-heteroarylpropionic acids from commercially available materials. This new methodology affords the title compounds in high yields and without the use of chromatography. [reaction: see text]     

Fragmentation of Neutral Amino Acids and Small Peptides by Intense, Femtosecond Laser Pulses

High power femtosecond laser pulses have unique properties that could lead to their application as ionization or activation sources in mass spectrometry. By concentrating many photons into pulse lengths approaching the timescales associated with atomic motion, very strong electric field strengths are generated, which can efficiently ionize and fragment molecules without the need for resonant absorption. However, the complex interaction between these pulses and biomolecular species is not well understood. To address this issue, we have studied the interaction of intense, femtosecond pulses with a number of amino acids and small peptides. Unlike previous studies, we have used neutral forms of these molecular targets, which allowed us to investigate dissociation of radical cations without the spectra being complicated by the action of mobile protons. We found fragmentation was dominated by fast, radical-initiated dissociation close to the charge site generated by the initial ionization or from subsequent ultrafast migration of this charge. Fragments with lower yields, which are useful for structural determinations, were also observed and attributed to radical migration caused by hydrogen atom transfer within the molecule.

Estimating Loynes�� exponent

Loynes?? distribution, which characterizes the one dimensional marginal of the stationary solution to Lindley??s recursion, possesses an ultimately exponential tail for a large class of increment processes. If one can observe increments but does not know their probabilistic properties, what are the statistical limits of estimating the tail exponent of Loynes?? distribution? We conjecture that in broad generality a consistent sequence of non-parametric estimators can be constructed that satisfies a large deviation principle. We present rigorous support for this conjecture under restrictive assumptions and simulation evidence indicating why we believe it to be true in greater generality.     

New products

The Seventh International Workshop on Infrared Microscopy and Spectroscopy with Accelerator-Based Sources (WIRMS 2013) was hosted by the Australian Synchrotron at the Mantra Resort in the coastal town of Lorne on the Great Ocean Road west of Melbourne, Australia, from November 10 to 14, 2013. In common with previous WIRMS meetings, the conference saw a coming together of staff and users from the world's synchrotron and free electron laser facilities, several of which were represented at the meeting for the first time. Scientific highlights of WIRMS 2013 included reports on FTIR spectro-microtomography, near-field infrared imaging, and cultural heritage applications.     

Oriented colourings of graphs with maximum degree three and four

We show that any orientation of a graph with maximum degree three has an oriented 9-colouring, and that any orientation of a graph with maximum degree four has an oriented 69-colouring. These results improve the best known upper bounds of 11 and 80, respectively.     

Demonstration of an optical biosensor for the detection of faecal indicator bacteria in freshwater and coastal bathing areas

ColiSense, an early warning system developed for Escherichia coli detection, is assessed using environmental samples. The system relies on the detection of β-glucuronidase (GUS), a biomarker enzyme for E. coli. In contrast with other rapid GUS-based methods, ColiSense is the only method that uses 6-chloro-4-methyl-umbelliferyl-β-d-glucuronide (6-CMUG) as a fluorogenic substrate. The system measures a direct kinetic response of extracted GUS, and the detection was carried out in the absence of particles or bacteria. It is necessary to evaluate the system with environmental samples to establish the relationship between faecal indicator bacteria E. coli and the response measured by the ColiSense. This paper presents the results of tests carried out with the ColiSense system for 2 trials, one conducted with freshwater samples collected from rivers in the Dublin area and a second conducted with seawater samples from coastal areas collected over the bathing season. A positive linear correlation was found between E. coli (MPN 100 mL⁻¹) and ColiSense response (R² = 0.85, N = 125, p < 0.01) for the seawater sample. A ColiSense response threshold was identified as 0–1.8 pmol min⁻¹ 100 mL⁻¹, equivalent to 0–500 E. coli 100 mL⁻¹. Using this threshold, 96.8% of the samples were correctly classified as being above or below 500 E. coli 100 mL⁻¹ by the ColiSense system. Results presented demonstrate that the ColiSense system can be used as an early warning tool with potential for active management of bathing areas by providing results in 75 min from sample collection.