Spontaneous Symmetry Breaking and the Renormalization of the Chern-Simons Term

We calculate the one-loop perturbative correction to the coefficient of the \cs term in non-abelian gauge theory in the presence of Higgs fields, with a variety of symmetry-breaking structures. In the case of a residual $U(1)$ symmetry, radiative corrections do not change the coefficient of the \cs term. In the case of an unbroken non-abelian subgroup, the coefficient of the relevant \cs term (suitably normalized) attains an integral correction, as required for consistency of the quantum theory. Interestingly, this coefficient arises purely from the unbroken non-abelian sector in question; the orthogonal sector makes no contribution. This implies that the coefficient of the \cs term is a discontinuous function over the phase diagram of the theory.Comment: Version to be published in Phys Lett B., minor additional change

Effect of speaker age on speech recognition and perceived listening effort in older adults with hearing loss

Published online January 2012Purpose: Older adults exhibit difficulty understanding speech that has been experimentally degraded. Age-related changes to the speech mechanism lead to natural degradations in signal quality. We tested the hypothesis that older adults with hearing loss would exhibit declines in speech recognition when listening to the speech of older adults, compared with the speech of younger adults, and would report greater amounts of listening effort in this task. Methods: Nineteen individuals with age-related hearing loss completed speech recognition and listening effort scaling tasks. Both were conducted in quiet, when listening to high and low predictability phrases produced by younger and older speakers respectively. Results: No significant difference in speech recognition existed when stimuli were derived from younger or older speakers. However, perceived effort was significantly higher when listening to speech from older adults, as compared to younger adults. Conclusions: For older individuals with hearing loss, natural degradations in signal quality may require greater listening effort. However, they do not interfere with speech recognition – at least in quiet. Follow-up investigation of the effect of speaker age on speech recognition and listening effort under more challenging noise conditions appears warranted

Recombinant expression and functional characterisation of regiospecific flavonoid glucosyltransferases from Hieracium pilosella L.

Five glucosyltransferases were cloned by RT-PCR amplification using total RNA from Hieracium pilosella L. (Asteraceae) inflorescences as template. Expression was accomplished in Escherichia coli, and three of the HIS-tagged enzymes, UGT90A7, UGT95A1, and UGT72B11 were partially purified and functionally characterised as UDP-glucose:flavonoid O-glucosyltransferases. Both UGT90A7 and UGT95A1 preferred luteolin as substrate, but possessed different regiospecificity profiles. UGT95A1 established a new subgroup within the UGT family showing high regiospecificity towards the C-3' hydroxyl group of luteolin, while UGT90A7 primarily yielded the 4'-O-glucoside, but concomitantly catalysed also the formation of the 7-O-glucoside, which could account for this flavones glucoside in H. pilosella flower heads. Semi quantitative expression profiles revealed that UGT95A1 was expressed at all stages of inflorescence development as well as in leaf and stem tissue, whereas UGT90A7 transcript abundance was nearly limited to flower tissue and started to develop with the pigmentation of closed buds. Other than these enzymes, UGT72B11 showed rather broad substrate acceptance, with highest activity towards flavones and flavonols which have not been reported from H. pilosella. As umbelliferone was also readily accepted, this enzyme could be involved in the glucosylation of coumarins and other metabolite

Methyltransferases from Ruta graveolens L.: Molecular Biology and Biochemistry

The common rue, Ruta graveolens L., is an aromatic plant. It contains acridone alkaloids, furoquinolines, coumarins, and numerous volatile compounds with antimicrobial and allelopathic activity. The starting point of this work was the biosynthesis of acridone alkaloids in Ruta graveolens L., that are restricted to the family of Rutaceae. The N-methylation of anthranilate by the anthranilate N-methyltransferase represents the first step in acridone alkaloid biosynthesis by which the anthranilic acid is removed from the primary metabolism. The anthranilate N-methyltransferase coding cDNA had to be isolated from R. graveolens cell culture material and the recombinant enzyme expressed and characterized. An appropriated method to clone an unknown protein is to isolate it from native tissue followed by microsequencing of the resulted peptides. Specific primers designed from the determined peptides would then be used for the cDNA amplification. In this work, 500 g wet weight of Ruta graveolens R-20 cells grown in suspension culture, were employed for a six-step purification strategy leading to a 450 times purification fold. The gel electrophoresis showed a polypeptide band with an apparent molecular weight of 42-43 kDa. Radioactive mesurements with [Methyl-14C]-SAM showed a high specific activity. The microsequencing of the protein, performed by Dr. Peter Hunziker (Biochemistry Department, University of Zürich), resulted in only five short peptide fragments with no homology with other known methyltransferases. Degenerated oligonucleotide primers, designed based on the peptide fragments, produced a PCR amplicon with no homology to methyltransferases. As the purification did not bring the desired result, degenerated oligonucleotide primers were designed based on the conserved motives (SAM binding site) in O-methyltransferases (OMT). With this method, two full length cDNAs were isolated, R-23 and R-27. R-23 was coding for a 366 amino acid protein with a calculated molecular weight of 40 kDa. R-27 was coding for a 41.6 kDa protein of 374 amino acid residues. These genes were cloned in pQE-60 vector and expressed in E. coli M-15. The protein R-23 had 79% similarity with caffeic acid O-methyltransferases and preserved all the amino acids important for methylation. R-27 showed all the important methyltransferases conserved motifs and had 50% similarity with a putative methyltransferase from Prunus dulcis respectively orcinol and chavicol O-methyltrasnferases from Rosa hybrida. Both bacterial overexpressed proteins were tested for substrate specificity. R-23 coded enzyme did not methylate any of the tested substrates, including caffeic acid. R-27 did methylate 3,5-dimethoxyphenol and other methoxylated phenols. The protein R-27 was purified in four chromatographic steps and characterized. The enzyme showed narrow substrate specificity. The highest affinity was with 3,5-dimethoxyphenol (Km 20.1 µM) with an optimum pH of 7.5. Other accepted substrates were: 3-methoxyphenol, guaiacol, 3,4-dimethoxyphenol and 3,5-dihydroxyanisole. The reaction was independent on cations. The optimum temperature was around 36˚C. On Coomassie stained SDS gel, the purified protein showed a characteristic band of 42 kDa. The calculated molecular weight from a calibrated size exclusion chromatographie was 84 kDa, suggesting that the native enzyme is a homodimer. The reaction product of 3,5-dimethoxyphenol methylation, 1,3,5-trimethoxybenzene is an important component of the scent of roses. Therefore, is reasonable to postulate that the product of the methylation described in this work is a volatile component of the scent of R. graveolens. Based on its substrate specificity, the protein was designated as 3,5-dimethoxyphenol O-methyltransferase. It could be shown that in the presence of Zn2+ the protein efficiently methylate DTT. The product was identified by LC-MS as monomethylthioether. Therefore, 3,5-dimethoxyphenol O-methyltransferase, in addition to the OMT activity, had a thiolmethyltransferase (TMT) activity. Kinetic analysis of 3,5-dimethoxyphenol methylation in the presence of various Zn2+/DTT concentrations showed a competitive DTT binding with an affinity of Ki = 52.0 µM. These results indicate that the OMT and TMT take place in the same active site of the enzyme. Altogether, these results suggest that the substrate specificity of plant O-methyltransferases II and their function in vivo is probably much wider as assumed