Cosolvents Restrain Self-Assembly of a Fibroin-Like Peptide on Graphite.

Controllable self-assembly of peptides on solid surfaces has been investigated for establishing functional bio/solid interfaces. In this work, we study the influence of organic solvents on the self-assembly of a fibroin-like peptide on a graphite surface. The peptide has been designed by mimicking fibroin proteins to have strong hydrogen bonds among peptides enabling their self-assembly. We have employed cosolvents of water and organic solvents with a wide range of dielectric constants to control peptide self-assembly on the surface. Atomic force microscopy has revealed that the peptides self-assemble into highly ordered monolayer-thick linear structures on graphite after incubation in pure water, where the coverage of peptides on the surface is more than 85%. When methanol is mixed, the peptide coverage becomes zero at a threshold concentration of 30% methanol on graphite and 25% methanol on MoS2. The threshold concentration in ethanol, isopropanol, dimethyl sulfoxide, and acetone varies depending on the dielectric constant with restraining self-assembly of the peptides, and particularly low dielectric-constant protic solvents prevent the peptide self-assembly significantly. The observed phenomena are explained by competitive surface adsorption of the organic solvents and peptides and the solvation effect of the peptide assembly.

Comparative genomic analysis of two novel plasmids from Acidithiobacillus ferrivorans strain PQ33 / Análisis genómico comparativo de dos nuevos plásmidos de la cepa PQ33 de Acidithiobacillus ferrivorans

Abstract Acidithiobacillus ferrivorans is a psychrotolerant acidophile capable of growing and oxidizing ferrous and sulphide substrates at low temperatures. To date, six genomes of this organism have been characterized; however, evidence of a plasmid in this species has been reported only once, whereby there is no conclusive role of the plasmids in the species. Herein, two novel plasmids of A. ferrivorans PQ33 were molecularly characterized and compared at a genomic scale. The genomes of two plasmids (12 kbp and 10 kbp) from A. ferrivorans PQ33 (NZ_LVZL01000000) were sequenced and annotated. The plasmids, named pAfPQ33-1 (NZ_CP021414.1) and pAfPQ33-2 (NZ_CP021415.1), presented 9 CDS and 13 CDS, respectively. In silico analysis showed proteins involved in conjugation (TraD, MobA, Eep and XerD), toxin-antitoxin systems (HicA and HicB), replication (RepA and DNA binding protein), transcription regulation (CopG), chaperone DnaJ, and a virulence gene (vapD). Furthermore, the plasmids contain sequences similar to phosphate-selective porins O and P and a diguanylate cyclase-phosphodiesterase protein. The presence of these genes suggests the possibility of horizontal transfer, a regulatory system of plasmid maintenance, and adhesion to substrates for A. ferrivorans species and PQ33. This is the first report of plasmids in this strain.

Resumen Acidithiobacillus ferrivorans es un acidófilo psicrotolerante capaz de hacer crecer y oxidar sustratos ferrosos y sulfurosos a bajas temperaturas. Hasta la fecha se han caracterizado seis genomas de este organismo; sin embargo, la evidencia de un plásmido en esta especie ha sido informado solo una vez, por lo que no hay un rol concluyente de los plásmidos en la especie. Aquí, dos plásmidos novedosos de A. ferrivorans PQ33 se caracterizaron molecularmente y se compararon a escala genómica. Se secuenciaron y anotaron los genomas de dos plásmidos (12 kpb y 10 kpb) de A. ferrivorans PQ33 (NZ_LVZL01000000). Los plásmidos, denominados pAfPQ33-1 (NZ_CP021414.1) y pAfPQ33-2 (NZ_CP021415.1), presentaron 9 CDS y 13 CDS, respectivamente. El análisis in silico mostró proteínas involucradas en la conjugación (TraD, MobA, Eep y XerD), sistemas de toxina-antitoxina (HicA y HicB), replicación (RepA y proteína de unión al ADN), regulación de la transcripción (CopG), chaperona DnaJ y un gen de virulencia (vapD). Además, los plásmidos contienen secuencias similares a las porinas selectivas de fosfato O y P y una proteína diguanilato ciclasa-fosfodiesterasa. La presencia de estos genes sugiere la posibilidad de transferencia horizontal, un sistema regulador de mantenimiento de plásmidos y adhesión a sustratos para especies de A. ferrivorans y PQ33. Este es el primer informe de plásmidos en esta cepa.

Draft Genome Sequences of Two Textile Azo Dye-Degrading Shewanella sp. Strains Isolated from a Textile Effluent in Peru.

Here, we report the annotated genome sequences of two Shewanella sp. strains isolated from textile industry wastewater effluent in Peru. Potential genes for encoding enzymes that enable the strain to decolorize and degrade textile azo dyes were detected in both genomes.

Reconstitution properties of biologically active polymersomes after cryogenic freezing and a freeze-drying process.

Reconstitution of biologically active polymersomes from the frozen or solid state into any fluid state is still a challenging issue for the design of new biological experiments and for the formulation of therapeutic agents. To gain knowledge about the reconstitution of pH-responsive and photo-crosslinked polymersomes, surface-functionalized and enzyme-containing polymersomers were cryogenically frozen (-20 °C) or freeze-dried with inulin as the lyoprotectant (0.1% w/v) and stored for a defined time period. Reconstituting those polymersomes in solution by thawing or a re-dispersing process revealed their original physical properties as well as their function as a pH-switchable enzymatic nanoreactor.

Hydrazine treatment improves conductivity of bacterial cellulose/graphene nanocomposites obtained by a novel processing method.

A novel method to prepare BC nanocomposites reinforced with reduced graphene oxide (RGO) is reported. A simple hydrazine treatment is shown to in-situ reduce the graphene oxide (GO) incorporated to BC films while increasing their conductivity. Raman spectroscopy was used to confirm the presence of graphene and assess the effect of the hydrazine treatment on its structure. XRD tests revealed no changes on BC structure. We hypothesize that this treatment removes the hydroxyl and epoxy groups present on the reduced graphene and increases the content of nonoxygenated carbon. These changes account for the increase in conductivity of the BC-based films, which behaved as an insulating material before the hydrazine treatment and reach an average conductivity value of 12S/m after such a treatment.