Possible overestimation of the external standard quench parameter on Wallac 1220 Quantulus™ with high energetic beta-emitters

The 1220 Quantulus is equipped with an ¹⁵²Eu external source used to determine an external standard quench parameter SQP(E). The relationship between ⁹⁰Sr/⁹⁰Y counting efficiency and SQP(E) was found linear in a defined range of SQP(E) values. This function was fixed after many counting experiences made with ⁹⁰Sr/⁹⁰Y standards. The sasme equation is used for the measurement of ⁹⁰Sr in environmental samples. The first goal of this paper is to objectify an overestimation of the SQP(E) when high energetic beta-emitters like ⁹⁰Y are present (1 to 4% in routine conditions). The second one is to show how this artefact could induce a bias in the calculation of ⁹⁰Sr activity in environmental samples. The median of this overestimation is estimated around 6%. Another approach using ⁸⁵Sr standard is suggested to avoid this overestimation. Provided the chemical composition — and thus the quenching — is similar for the two standards, the counting efficiency measured with the ⁹⁰Sr/⁹⁰Y standard could be related to the SQP(E) value of the ⁸⁵Sr standard. Indeed this one appears to be more robust regarding to the range of activity and to the counting time of the external source.     

Synthesis of 3,4,7,8-tetrahydronaphthalene-1,5(2H,6H)-dione

A short and high yielding route for the preparation of the title compound, starting from commercially available 1,5-dihydroxynaphthalene, is described. The key step in the sequence is the air oxidation of a bis(trimethylsilyloxy)diene precursor.     

Presence of thiamine pyrophosphate in mammalian peroxisomes

Background

Thiamine pyrophosphate (TPP) is a cofactor for 2-hydroxyacyl-CoA lyase 1 (HACL1), a peroxisomal enzyme essential for the α-oxidation of phytanic acid and 2-hydroxy straight chain fatty acids. So far, HACL1 is the only known peroxisomal TPP-dependent enzyme in mammals. Little is known about the transport of metabolites and cofactors across the peroxisomal membrane and no peroxisomal thiamine or TPP carrier has been identified in mammals yet. This study was undertaken to get a better insight into these issues and to shed light on the role of TPP in peroxisomal metabolism.

Results

Because of the crucial role of the cofactor TPP, we reanalyzed its subcellular localization in rat liver. In addition to the known mitochondrial and cytosolic pools, we demonstrated, for the first time, that peroxisomes contain TPP (177 ± 2 pmol/mg protein). Subsequently, we verified whether TPP could be synthesized from its precursor thiamine, in situ, by a peroxisomal thiamine pyrophosphokinase (TPK). However, TPK activity was exclusively recovered in the cytosol.

Conclusion

Our results clearly indicate that mammalian peroxisomes do contain TPP but that no pyrophosphorylation of thiamine occurs in these organelles, implying that thiamine must enter the peroxisome already pyrophosphorylated. Consequently, TPP entry may depend on a specific transport system or, in a bound form, on HACL1 translocation.     

Tip‐enhanced Raman spectroscopy – an interlaboratory reproducibility and comparison study

Since its first experimental realization, tip‐enhanced Raman spectroscopy (TERS) has emerged as a potentially powerful nanochemical analysis tool. However, questions about the comparability and reproducibility of TERS data have emerged. This interlaboratory comparison study addresses these issues by bringing together different TERS groups to perform TERS measurements on nominally identical samples. Based on the spectra obtained, the absolute and relative peak positions, number of bands, peak intensity ratios, and comparability to reference Raman and surface‐enhanced Raman spectroscopy (SERS) data are discussed. Our general findings are that all research groups obtained similar spectral patterns, irrespective of the setup or tip that was used. The TERS (and SERS) spectra consistently showed fewer bands than the conventional Raman spectrum. When comparing these three methods, the spectral pattern match and substance identification is readily possible. Absolute and relative peak positions of the three major signals of thiophenol scattered by 19 and 9 cm⁻¹, respectively, which can probably be attributed to different spectrometer calibrations. However, within the same group (but between different tips), the signals only scattered by 3 cm⁻¹ on average. This study demonstrated the suitability of TERS as an analytical tool and brings TERS a big step forward to becoming a routine technique. Copyright © 2014 John Wiley & Sons, Ltd.     

Straightforward synthesis of cholic acid stabilized loop mimetics

We here report on a new straightforward strategy for the synthesis of cyclic cholic acid–peptide conjugates. A solid-phase synthesis method is presented in which a selected anti-lysozyme CDR3 fragment, Asp-Ser-Thr-Ile-Tyr-Ala-Ser-Tyr-Tyr-Glu-Ser, is immobilized onto a steroidal cholic acid derived scaffold in order to yield a loop-like structure. Therefore, part of the desired sequence, that is, Ser-Tyr-Tyr-Glu-Ser, is introduced, at the C12 position of the scaffold. Subsequently, the remainder of the envisaged sequence is introduced at C3 via a Cu-catalyzed cyclo-addition reaction. Finally, amide bond formation delivers the desired cyclic peptidosteroid. This new synthetic strategy offers an easy and short access to cyclic peptidosteroids via convergent peptide ligation and macrocyclization.     

Universal cycles of -partitions of an -set

In 1992 Chung, Diaconis and Graham generalized de Bruijn cycles to other combinatorial families with universal cycles. Universal cycles have been investigated for permutations, partitions, k-partitions and k-subsets. In 1990 Hurlbert proved that there exists at least one Ucycle of n−1-partitions of an n-set when n is odd and conjectured that when n is even, they do not exist. Herein we prove Hurlbert’s conjecture by establishing algebraic necessary and sufficient conditions for the existence of these Ucycles. We enumerate all such Ucycles for n≤13 and give a lower bound on the total number for all n. Additionally we give ranking and unranking formulae. Finally we discuss the structures of the various solutions.     

Automated quantitative gait analysis in animal models of movement disorders

Background  

Accurate and reproducible behavioral tests in animal models are of major importance in the development and evaluation of new therapies for central nervous system disease. In this study we investigated for the first time gait parameters of rat models for Parkinson's disease (PD), Huntington's disease (HD) and stroke using the Catwalk method, a novel automated gait analysis test. Static and dynamic gait parameters were measured in all animal models, and these data were compared to readouts of established behavioral tests, such as the cylinder test in the PD and stroke rats and the rotarod tests for the HD group.     

Weak coupling many-polaron description of ultracold bosonic impurities in a condensate

The weak coupling many-polaron formalism is applied to ultracold bosonic impurities in a Bose-Einstein condensate. This formalism allows calculating the ground state and response properties. We apply this to calculate both the inertial and spectral effective masses of the impurities and the response of the system to Bragg scattering.     

Spectroscopic Investigations of Polymer Nanocomposites

The addition of an inorganic component to polymers leads to improvements in various physical and mechanical properties. Various examples on filled elastomeric networks will show that a mechanical characterization can be nicely combined with a spectroscopic investigation for a better understanding of the properties of the composite materials.