Note: cryogenic coaxial microwave filters.

The careful filtering of microwave electromagnetic radiation is critical for controlling the electromagnetic environment for experiments in solid-state quantum information processing and quantum metrology at millikelvin temperatures. We describe the design and fabrication of a coaxial filter assembly and demonstrate that its performance is in excellent agreement with theoretical modelling. We further perform an indicative test of the operation of the filters by making current-voltage measurements of small, underdamped Josephson junctions at 15 mK.

Berry phenolics selectively inhibit the growth of intestinal pathogens.

AIMS: To investigate the effects of berries and berry phenolics on pathogenic intestinal bacteria and to identify single phenolic compounds being responsible for antimicrobial activity. METHODS AND RESULTS: Antimicrobial activity of eight Nordic berries and their phenolic extracts and purified phenolic fractions were measured against eight selected human pathogens. Pathogenic bacterial strains, both Gram-positive and Gram-negative, were selectively inhibited by bioactive berry compounds. Cloudberry and raspberry were the best inhibitors, and Staphylococcus and Salmonella the most sensitive bacteria. Phenolic compounds, especially ellagitannins, were strong inhibitory compounds against Staphylococcus bacteria. Salmonella bacteria were only partly inhibited by the berry phenolics, and most of the inhibition seemed to originate from other compounds, such as organic acids. Listeria strains were not affected by berry compounds, with the exception of cranberry. Phenolic compounds affect the bacteria in different mechanisms. CONCLUSIONS: Berries and their phenolics selectively inhibit the growth of human pathogenic bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: Antimicrobial properties of berries could be utilized in functional foods. Furthermore these compounds would be of high interest for further evaluation of their properties as natural antimicrobial agents for food and pharmaceutical industry.

The upstream limit of nuclease-sensitive chromatin in Dictyostelium rRNA genes neighbors a topoisomerase I-like cluster.

In the chromatin of Dictyostelium ribosomal RNA (rRNA) genes, the coding and upstream flanking regions are sensitive to endonucleases. This sensitivity stops about 2.3 x 10(3) bases upstream from the transcription start, at a point we call the structural boundary. Upstream from the boundary an 850 base-pair region is strongly protected against micrococcal nuclease cleavage, particularly in rapidly transcribing vegetative cells, and upstream from this the pattern of nuclease protection suggests that positioned nucleosomes are present. On the gene side of the structural boundary nucleosomes are known to be absent in vegetative cells but present in differentiating slug cells where the rRNA synthesis rate is lower. We show that in slugs these nucleosomes are randomly distributed, in contrast to those upstream from the boundary. Close to the gene side of the boundary is a duplication of the putative promoter located 29 base-pairs distant from four clustered topoisomerase I recognition sequences, which are cleaved by endogenous topoisomerase I-like activity. An additional topoisomerase I recognition sequence found upstream from the structural boundary is not cleaved in chromatin. The possible significance of these sequences and structures in transcription is discussed.

A lysine-rich protein functions as an H1 histone in Dictyostelium discoideum chromatin.

Mononucleosomes released from Dictyostelium discoideum chromatin by micrococcal nuclease contained two distinctive DNA sizes (166-180 and 146 bp). Two dimensional gel electrophoresis suggested a lysine-rich protein protected the larger mononucleosomes from nuclease digestion. This was confirmed by stripping the protein from chromatin with Dowex resin. Subsequently, only the 146 bp mononucleosome was produced by nuclease digestion. Reconstitution of the stripped chromatin with the purified lysine-rich protein resulted in the reappearance of the larger mononucleosomes. Two-dimensional gel electrophoresis showed the protein was associated with mononucleosomes. Hence, the protein functions as an H1 histone in bringing the two DNA strands together at their exit point from the nucleosome. Trypsin digestion of the lysine-rich protein in nuclei resulted in a limiting peptide of approx. 10 kilodaltons. Trypsin concentrations which degraded the protein to peptides of 12-14 kilodaltons and partially degraded the core histones did not change the DNA digestion patterns obtained with micrococcal nuclease. Thus, the trypsin-resistant domain of the lysine-rich protein is able to maintain chromatosome structure.