How We Make DNA Origami

DNA origami has attracted substantial attention since its invention ten years ago, due to the seemingly infinite possibilities that it affords for creating customized nanoscale objects. Although the basic concept of DNA origami is easy to understand, using custom DNA origami in practical applications requires detailed know‐how for designing and producing the particles with sufficient quality and for preparing them at appropriate concentrations with the necessary degree of purity in custom environments. Such know‐how is not readily available for newcomers to the field, thus slowing down the rate at which new applications outside the field of DNA nanotechnology may emerge. To foster faster progress, we share in this article the experience in making and preparing DNA origami that we have accumulated over recent years. We discuss design solutions for creating advanced structural motifs including corners and various types of hinges that expand the design space for the more rigid multilayer DNA origami and provide guidelines for preventing undesired aggregation and on how to induce specific oligomerization of multiple DNA origami building blocks. In addition, we provide detailed protocols and discuss the expected results for five key methods that allow efficient and damage‐free preparation of DNA origami. These methods are agarose‐gel purification, filtration through molecular cut‐off membranes, PEG precipitation, size‐exclusion chromatography, and ultracentrifugation‐based sedimentation. The guide for creating advanced design motifs and the detailed protocols with their experimental characterization that we describe here should lower the barrier for researchers to accomplish the full DNA origami production workflow.     

Hydrophobic cellulose fibers via ATRP and their performance in the removal of pyrene from water

In the present work, cellulose fibers were modified by grafting with poly(lauryl acrylate) and poly(octadecyl acrylate). The grafted materials were prepared by polymerization of the corresponding monomers via surface initiated atom transfer radical polymerization, starting from cellulose papers previously modified with 2‐bromoisobutyryl groups. The polymerizations were carried out in the presence of ethyl‐2‐bromoisobutyrate, as a sacrificial initiator, added to control the molecular weight of the anchored segments, and polymerization kinetics. The grafting of both polymers was confirmed by infrared spectroscopy and elemental analysis. The effect of grafting these polymers on the thermal stability, morphology, and surface properties of cellulose fibers was studied using thermogravimetric analysis, scanning electron microscopy, and measuring water contact angle, respectively. The results reveal that grafting poly(lauryl acrylate) and poly(octadecyl acrylate) to cellulose confers the filter paper a hydrophobic character, and increases its affinity with pyrene, allowing the removal of this pollutant from water. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44482.     

Nitrogen and phosphorus uptake,yield and agronomic traits of oat cultivars as affected by fertilizer N rates under diverse environments

Oat has been gaining renewed interest due to its role in human healthy diet. A field study was conducted across three diverse locations in Canada to determine N and P uptake, agronomic traits and yield performance of 10–12 cultivars under four fertilizer N rates. Our data showed that ‘SA060123’ and ‘OA1331-5’ were the highest-yielding cultivars, and ‘Dieter’ and ‘Morrison’ the lowest, across sites-years. Yield components were altered to adapt to soil-environmental conditions, specifically, panicles m^?2 mostly accounted for yield variation at Melfort, seeds panicle^?1 and 1000-seed weight at Normandin, and lodging index was an additional yield-determining factor at Ottawa. It was noted that severe crop lodging that occurred mainly at Ottawa, was logically associated with greater accumulation of straw N and plant biomass under high N supply conditions, and that crop lodging displayed a strong correlation with straw P content. Relationship of lodging index and straw P was best-fit into a split-line model with a change-point of 13.6 kg P ha^?1, below which lodging rarely occurred. We speculate that high straw P content, induced by external N supply, may have exhibited similar behavior as N in weakening the strength of stem base and anchorage system, leading to crop lodging. This study also demonstrated an interactive genotype-by-environment effect on all traits except for the seed number panicle^?1. Multidimensional preference analysis revealed the best performance of ‘SA060123’ for outstanding yield and 'Minstrel' for harvest index, respectively.     

Formation of a Ti-siliceous trimodal material with macroholes, mesopores and zeolitic features via a one-pot templating synthesis

Based on a facile one-pot templating synthesis, using a TS-1 zeolite recipe whereby part of the zeolite structure directing agent is replaced by a mesopore templating agent, a trimodal material is formed. The resulting meso-TSM material combines mesoporosity (Ti-MCM-41) with zeolitic features (TS-1) and a unique sheet-like morphology with uniform macroporous voids (macroholes). Moreover, the macrohole formation, mesoporosity and zeolitic properties of the meso-TSM material can be controlled in a straightforward way by adjusting the length of the hydrothermal treatment. This newly developed material may imply great potential for catalytic redox applications and diffusion limitated processes because of its highly tunable character in all three dimensions (micro-, meso- and macroporous scale).     

Physiochemical Properties of <Emphasis Type="Italic">Jatropha curcas</Emphasis> Seed Oil from Different Origins and Candidate Plus Plants (CPPs)

The physicochemical properties of Jatropha seed oil from 9 geographical origins and 24 candidate plus plants (CPPs) were evaluated. The yield of seed oil obtained by Soxhlet extraction using n-hexane as solvent varied from 40.0% (Malaysia) to 48.4% (Vietnam) among seeds from different origins and 32.1% (CPP-17) to 48.8% (CPP-01) (w/w) among CPPs. Density, specific gravity, and refractive index of oil showed very little differences among all the seed sources. Oil from Borneo had the highest free fatty acid (FFA) content (2.3%) and a South African sample had the lowest FFA (0.4%), as oleic acids. Seed oil of CPP-13 had the highest FFA content (1.2%) and seed oil of CPP-17 the lowest (0.3%). Most of the CPPs in this study had an FFA content of less than 1%. Jatropha seed oil of Philippine origin had the highest iodine value (187.3 mg/g oil) and seed oil from Borneo the lowest (83.5 mg/g oil). The lowest saponification values were obtained from seed oil of Philippine origin (189.5 mg KOH/g) and CPP-22 (183.3 mg KOH/g oil) from Malaysia. The maximum higher heating value (40.3 MJ/kg) was obtained from seed oil from Borneo. The cetane numbers range from 25.4 (Indonesia) to 56.0 (Borneo) among the oils of base material and 46.4 (CPP-15) to 53.7 (CPP-06) among CPPs. This study gives basic information of relevance for biodiesel production using Jatropha seeds from various origins.     

Antimicrobial materials based on poly(ethylene-co-vinyl alcohol) and silver acetate produced by reactive extrusion

The use of silver as an antimicrobial agent has exhibited great interest in recent years. In this research, poly(ethylene-co-vinyl alcohol) (EVOH)–silver acetate-based antimicrobial materials were prepared at high temperature by reactive extrusion. Silver acetates were used without pretreatment. The thermal reaction of silver acetates in the material and their effect on the thermal and mechanical properties of the polymer were investigated as a function of their concentration. The dispersed silver acetate salts within the EVOH matrix have displayed a significant thermal reaction. This reaction of metallic salts was partial when the extrusion temperature was fixed at 190 °C and completed at 230 °C. The antimicrobial agents also had significant effects on the properties of the matrix. Reductions of glass temperature and storage modulus were observed by the analyses. All the variations were dependent on both the concentration of silver acetate and the extrusion parameters. The antimicrobial activity was studied and demonstrated a promising potential to create an antimicrobial material in a one-step solvent free extrusion method. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47799.     

Investigation of ZnFe2O4 spinel ferrite nanocrystalline screen-printed thick films for application in humidity sensing

Zinc ferrite nanocrystalline powder was obtained by solid state synthesis of starting zinc oxide and hematite nanopowders. Field emission scanning electron microscopy and transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy confirmed the formation of nanocrystalline zinc-ferrite powder with a mixed spinel structure with small amounts of remaining zinc oxide and hematite as impurities. Thick film paste was formed and screen printed on test interdigitated PdAg electrodes on alumina substrate. Formation of a porous nanocrystalline structure was confirmed by scanning electron microscopy and Hg porosimetry. Humidity sensing properties of zinc ferrite thick films were investigated by monitoring the change in impedance in the relative humidity interval 30%-90% in the frequency range 42 Hz-1 MHz at room temperature (25°C) and 50°C. At 42 Hz at both analyzed temperatures the impedance reduced ~46 times in the humidity range 30%-90%. The dominant influence of grain boundaries was confirmed by analysis of complex impedance with an equivalent circuit.     

The effects of cryogenic treatment on the toughness and tribological behaviors of eutectoid steel

Cryogenic treatment is a supplementary heat treatment usually applied after quenching. Its effects are permanent and this process affects the entire section. There have been many studies related to cryogenic treatment, most of which have been focused on tool steels. In the current study, a high-speed-train railway material was investigated, and different heat treatment processes were applied to the eutectoid steel. The effects of quenching and cryogenic treatment were investigated on the mechanical properties (toughness, hardness and wear). Four different structures were obtained with different heat treatment cycles: Pearlitic, tempered martensite, 12 hour cryo-treated tempered and 36 hour cryo-treated tempered. As a result of Charpy v-notch tests and hardness tests, cryogenic treatment was found to improve the toughness and hardness of quenched samples. The results of the ball-on-disc wear tests showed that the cryo-treated samples have better wear resistance than pearlitic and martensitic samples.     

Analysis of Publications on Porous Silicon: From Photoluminescence to Biology

The issue of porous silicon has attracted much research during last seven years due to perspectives of the formation of all-silicon optoelectronic devices (first of all—LEDs). The work presents a bibliographic analysis of publications made during the period from 1990 (when red-light photoluminescence from porous silicon was first reported by Dr. L. Canham) to the present time in order to reveal the existing tendencies of the researches (what particular field attracts the most research, who is the most fruitful in publishing articles related to porous silicon, etc.). The contributions of different research centres and countries are also evaluated. Personal contributions of leading researchers are disclosed and their citation ranking is given. It is concluded that emerging applications of porous silicon in micro-machining, chemical and biological monitoring will stimulate further activities in studying the mechanism of porous silicon growth and its physical and chemical properties.     

Stress relaxation in carbon black loaded butyl rubber

The dependence of equilibrium force (F^*) on the strain ratio (α) of carbon black loaded butyl rubber was studied. The relation between elastic constant and volume fraction of carbon black was found in good agreement with that obtained by Guth and Gold relation at low concentrations using the shape factor (f = 6.5). The relaxation time and viscosity (η) were calculated by using stress relaxation of these samples at different compression strains. The same agreement was observed in the relation between viscosity and volume fraction of carbon black concentration. The results are discussed according to the dispersion mechanism of carbon black in rubber. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1067–1076, 2000