First observation of the Greisen-Zatsepin-Kuzmin suppression

The High Resolution Fly's Eye (HiRes) experiment has observed the Greisen-Zatsepin-Kuzmin suppression (called the GZK cutoff) with a statistical significance of five standard deviations. HiRes' measurement of the flux of ultrahigh energy cosmic rays shows a sharp suppression at an energy of 6 x 10(19) eV, consistent with the expected cutoff energy. We observe the ankle of the cosmic-ray energy spectrum as well, at an energy of 4 x 10(18) eV. We describe the experiment, data collection, and analysis and estimate the systematic uncertainties. The results are presented and the calculation of the statistical significance of our observation is described.     

A method for computer analysis of kinetics of competing first- and second-order reactions

Competing first- and second-order reactions of transient molecular species (e.g., triplet states and free radicals) are a common occurrence in kinetic studies such as flash photolysis and pulse radiolysis. We have developed a method for analyzing the decay kinetics of any species (Y) whose disappearance is described by ?dY/dt = k₁Y + k₂Y². The computer program (written in time-sharing BASIC) employs an iterative technique to obtain the least-squares estimates of the three parameters in the integrated rate equation.     

Michael addition of amines and thiols to dehydroalanine amides: a remarkable rate acceleration in water

In water, the rate of Michael addition of amines and thiols to dehydroalanine amides was greatly accelerated, leading to shorter reaction times and higher yields. The scope of the new conditions was tested with a range of amines, thiols, and dehydroalanine amides. The ease and efficiency of this method provides an attractive route to the synthesis of natural and unnatural amino acid derivatives.     

Triterpenoids

This review covers the isolation and structure determination of triterpenoids including squalene derivatives, lanostanes, cycloartanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, uranes, hopanes, isomalabaricanes and saponins. The literature from January to December 2004 is reviewed and 243 references are cited.     

The production and characterisation of an antibody to detect the coccidiostat toltrazuril and its metabolite ponazuril

The production of an antibody to detect toltrazuril or its metabolite ponazuril is complicated due to structural constraints of conjugating these coccidiostats to a carrier protein. Therefore a search was carried out for a compound that shared a common substructure to use as an antigen mimic. The chosen compound, trifluoraminoether, was conjugated to two carrier proteins (HSA and BTG) and used in the immunisation of six rabbits. Two immunogen doses (1 mg and 0.1 mg) were also used. All six rabbits produced an immunological response to the hapten regardless of the carrier protein or immunogen dose used. The most sensitive polyclonal antibody produced, designated R609, was subsequently characterised. This antiserum exhibited an IC50 of 18 ng ml(-1) using a competitive ELISA format. Cross reactivity studies show that this serum is specific for toltrazuril and its metabolites (toltrazuril sulfoxide and toltrazuril sulfone) but does not cross-react with other coccidiostats such as halofuginone, nitroimidazoles or nicarbazin. This is the first reported production of an antibody capable of specifically binding toltrazuril and ponazuril.     

Simple Methods for Preparing Oligonucleotides Containing 1) Thiol Groups at their 5′-Termini, 2) 5′-Phosphates

Abstract

A simple method has been developed for synthesising oligonucleotides containing a thiol group at their 5′-termini. The sequence required is prepared using standard solid phase phosphoramidite methods and an extra round of synthesis is then performed with S-triphenylmethyl O-methoxymorpholino-phosphinyl 3-mercaptopropan (1) ol. After normal deblocking this gives an oligonucleotide containing a tritylthiol group attached to the 5′-phosphate of an oligonucleotide via a 3-carbon spacer arm. The trityl group can be removed with AgNO₃ at pH 5 to give the free thiol. This compound is stable at pH 8 and reacts cleanly and rapidly with sulphydryl specific probes (eg fluorescent iodoacetates) at this pH value. This method can be used to prepare a wide variety of usefully labelled oligonucleotides and it is envisaged that fluorescent oligonucleotides will be useful in the study of protein nucleic acid interactions and to replace ³²P labelled hybridisation probes.