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Biomolecular nanotechnology has helped emulate basic robotic capabilities such as defined motion, sensing, and actuation in synthetic nanoscale systems. DNA origami is an attractive approach for nanorobotics, as it enables creation of devices with complex geometry, programmed motion, rapid actuation, force application, and various kinds of sensing modalities. Advanced robotic functions like feedback control, autonomy, or programmed routines also require the ability to transmit signals among subcomponents. Prior work in DNA nanotechnology has established approaches for signal transmission, for example through diffusing strands or structurally coupled motions. However, soluble communication is often slow and structural coupling of motions can limit the function of individual components, for example to respond to the environment. Here, we introduce an approach inspired by protein allostery to transmit signals between two distal dynamic components through steric interactions. These components undergo separate thermal fluctuations where certain conformations of one arm will sterically occlude conformations of the distal arm. We implement this approach in a DNA origami device consisting of two stiff arms each connected to a base platform via a flexible hinge joint. We demonstrate the ability for one arm to sterically regulate both the range of motion and the conformational state (latched or freely fluctuating) of the distal arm, results that are quantitatively captured by mesoscopic simulations using experimentally informed energy landscapes for hinge-angle fluctuations. We further demonstrate the ability to modulate signal transmission by mechanically tuning the range of thermal fluctuations and controlling the conformational states of the arms. Our results establish a communication mechanism well-suited to transmit signals between thermally fluctuating dynamic components and provide a path to transmitting signals where the input is a dynamic response to parameters like force or solution conditions.

Species of Brachycephalus has been having taxonomical issues due its morphological similarity and genetic conservatism. Herein, we describe a new species of Brachycephalus from the south Mantiqueira mountain range and semidecidual forests in the municipalities of Mogi das Cruzes, Campinas and Jundiaí, state of São Paulo, Brazil, based on an integrative approach. It can be distinguished from all species of the B. ephippium species group based on morphological characters (especially osteology and head shape), advertisement call and divergence in partial mitochondrial DNA gene sequences (16S). The new species is genetically similar to B. margaritatus and morphologically similar to B. ephippium. It can be differentiated from B. ephippium by the presence of dark faded spots on skull and post-cranial plates, presence of black connective tissue connective tissue scattered over dorsal musculature, parotic plate morphology, smaller snout-vent length (adult SVL: males 13.46-15.92 mm; females 16.04-17.69 mm) and 3% genetic distance. We also present natural history data and discuss the robustness of the integrative approach, geographic distribution, genetic data, behaviour, fluorescence in ontogeny, and conservation status., Competing Interests: The authors have declared that no competing interests exist.

Some chlorinated hydrocarbon solvents--1,1,1-trichloroethane, trichloroethylene and perchloroethylene--have a common biotransformation product, trichloroacetic acid, which can be used as their biological exposure index. The spectrophotometric and gas chromatographic methods for the determination of trichloroacetic acid were studied and used as well as in its determination in the urine of workers exposed to 1,1,1-trichloroethane. Both methods showed good precision and no statistically significant difference was found although the gas chromatographic method presented a lower detection limit.

We have analyzed the structure of genes encoding the glyoxylate cycle enzyme isocitrate lyase from Brassica napus L. and their expression during embryogeny and postgermination. Restriction mapping, nucleotide sequence, and DNA gel blot hybridization analyses of cDNA and genomic clones indicated that there are approximately six isocitrate lyase genes in the B. napus genome that can be divided into at least two subfamilies based upon their divergence in 5' and 3' untranslated regions. We showed previously that isocitrate lyase mRNA accumulates during late embryogeny and postgermination. Here, we present results which indicate that several isocitrate lyase genes are expressed at both stages of development. First, gene-specific probes were used to show that mRNAs encoded by representatives of both gene subfamilies accumulated in both late maturation stage embryos and in seedlings of B. napus. Second, a single B. napus isocitrate lyase gene, together with 3.5 kb and 1.4 kb of 5' and 3' flanking regions, respectively, was expressed in both embryos and seedlings of transgenic tobacco plants. The results indicated that accumulation of isocitrate lyase in late embryogeny and postgermination does not result from the alternate expression of distinct members of the gene family.

Human alpha-thalassemia-2 genotype -alpha 4.2 is the result of meiotic recombination between two 1.3 kb long, homologous DNA segments, X(alpha 2) and X(alpha 1), located in the adult alpha globin locus. The two segments can also undergo intramolecular recombination on extrachromosomal vectors transfected into mitotically dividing primate cells (COS 7). The existence of a gradient of sequence divergence between X(alpha 2) and X(alpha 1) makes them an interesting system to study the relationship between efficiencies of homologous DNA recombination and the extent of dispersed and localized base mismatches. By partial restriction mapping and DNA sequencing of plasmids recombined in COS 7 cells and rescued from bacteria HB 101, we have determined the distribution of recombinational resolution sites along the two X blocks. Most, if not all, of the homologous recombination events between the two X blocks appear to be single crossing-over without efficient gene correction or repair of base mismatches. The distribution of the sites of recombinational resolution is inversely correlated with that of the gradient of sequence divergence, with only approximately 7% of the X recombinants resolved within the 3' third of the X blocks where two diverged Alu family repeats reside. The Alu sequence within which one of the X recombinants resolved is homologous to a previously characterized alpha thalassemia deletion point.

In Brazil, glue sniffing has been of growing concern due to the increasing number of abusers, most of them children and teen-agers of low socio-economic level. This review article presents some aspects of this kind of abuse, with special emphasis on the deleterious effects of acute and/or chronic solvent inhalation (glue-sniffing).

Penicillin acylase (PA) is an industrial enzyme that is used to convert penicillin G into a precursor for semisynthetic penicillins. We have cloned a segment of DNA that codes for the two subunits required for PA activity. We also report the nucleotide sequence of a DNA fragment that codes for (i) the small subunit, (ii) the N-terminal region of the large subunit and (iii) a putative connecting peptide. These results confirm the existence of a common precursor for both peptides.