Development of electrically powered DNA origami nanomachines requires effective means to actuate moving origami parts by externally applied electric fields. We demonstrate how origami nanolevers on ...an electrode can be manipulated (switched) at high frequency by alternating voltages. Orientation switching is long-time stable and can be induced by applying low voltages of 200 mV. The mechanical response time of a 100 nm long origami lever to an applied voltage step is less than 100 μs, allowing dynamic control of the induced motion. Moreover, through voltage assisted capture, origamis can be immobilized from folding solution without purification, even in the presence of excess staple strands. The results establish a way for interfacing and controlling DNA origamis with standard electronics, and enable their use as moving parts in electro-mechanical nanodevices.
The study of the aggregation of soluble proteins into highly ordered, insoluble amyloid fibrils is fundamental for the understanding of neurodegenerative disorders. Here, we present a method for the ...observation of single amyloid fibrils that allows the investigation of fibril growth, secondary nucleation or fibril breakup that is typically hidden in the average ensemble. Our approach of thermophoretic trapping and rotational diffusion measurements is demonstrated for single Aβ
, Aβ
and pyroglutamyl-modified amyloid-β variant (pGlu
-Aβ
) amyloid fibrils.
The microscopic mechanism of platinum cluster nucleation on DNA templates is studied by first-principle molecular dynamics simulations. We find that Pt(II) complexes bound to DNA can form strong ...Pt−Pt bonds with free Pt complexes after a single reduction step, and may thus act as preferential nucleation sites. This is confirmed by a series of reduction experiments, in which we achieve purely heterogeneous platinum growth on DNA, and use it to fabricate metal cluster necklaces of unprecedented thinness and regularity.
•An amperometric microbial electrochemical sensor for volatile fatty acids (VFA) is characterized.•Characterization included cross sensitivity as well as response behavior, latency and recovery.•A ...biphasic response behavior was shown to depend on the previous acetate exposure.•Future engineering on sensor stability, dynamic response behavior and cross sensitivity are discussed.
Microbial electrochemical sensors are an evolving technology platform based on electroactive microorganisms. Sensors based on anodic biofilms that oxidize organic substrates like acetate as living recognition element are promising for online monitoring of anaerobic digestion (AD), wastewater treatment as well as other processes. Essential for future engineering of microbial electrochemical sensors is the detailed characterization of its cross sensitivity as well as response behavior and latency. These parameters were examined on the example of a microbial electrochemical acetate sensor build in a 100mL continuously stirred tank reactor. Furthermore, the ability of the sensor to recover after different periods (5–10days) of shut down (i.e. open cell potential (OCP)) was studied. The sensor showed cross sensitivity towards propionate and butyrate that can be described as a baseline sum signal (0.040±0.008mAcm−2) irrespective of the applied concentration. The sensor also revealed biphasic response behavior towards dynamic changes in acetate concentration shown to be strongly dependent on prior exposure to low acetate concentrations. This behavior is discussed by means of the metabolic state of the microbial cells forming the recognition element. Furthermore, the sensor revealed full recovery of activity after three consecutive OCP periods showing that sensor shutdown is not a limiting factor. The dynamic response behavior and the cross sensitivity of the sensor are discussed as challenges for engineering of future applications.
Carbon nanotube yarns (CNY) are a novel carbonaceous material and have received a great deal of interest since the beginning of the 21st century. CNY are of particular interest due to their useful ...heat conducting, electrical conducting, and mechanical properties. The electrical conductivity of carbon nanotube yarns can also be influenced by functionalization and annealing. A systematical study of this post synthetic treatment will assist in understanding what factors influences the conductivity of these materials. In this investigation, it is shown that the electrical conductivity can be increased by a factor of 2 and 5.5 through functionalization with acids and high temperature annealing respectively. The scale of the enhancement is dependent on the reducing of intertube space in case of functionalization. For annealing, not only is the highly graphitic structure of the carbon nanotubes (CNT) important, but it is also shown to influence the residual amorphous carbon in the structure. The promising results of this study can help to utilize CNY as a replacement for common materials in the field of electrical wiring.
With the aim of preparing hybrid hydrogels suitable for use as patches for the local treatment of squamous cell carcinoma (SCC)-affected areas, curcumin (CUR) was loaded onto graphene oxide (GO) ...nanosheets, which were then blended into an alginate hydrogel that was crosslinked by means of calcium ions. The homogeneous incorporation of GO within the polymer network, which was confirmed through morphological investigations, improved the stability of the hybrid system compared to blank hydrogels. The weight loss in the 100-170 °C temperature range was reduced from 30% to 20%, and the degradation of alginate chains shifted to higher temperatures. Moreover, GO enhanced the stability in water media by counteracting the de-crosslinking process of the polymer network. Cell viability assays showed that the loading of CUR (2.5% and 5% by weight) was able to reduce the intrinsic toxicity of GO towards healthy cells, while higher amounts were ineffective due to the antioxidant/prooxidant paradox. Interestingly, the CUR-loaded systems were found to possess a strong cytotoxic effect in SCC cancer cells, and the sustained CUR release (~50% after 96 h) allowed long-term anticancer efficiency to be hypothesized.
In addition to the classic functions of proteins, such as acting as a biocatalyst or binding partner, the conformational states of proteins and their remodeling upon stimulation need to be ...considered. A prominent example of a protein that undergoes comprehensive conformational remodeling is transglutaminase 2 (TGase 2), the distinct conformational states of which are closely related to particular functions. Its involvement in various pathophysiological processes, including fibrosis and cancer, motivates the development of theranostic agents, particularly based on inhibitors that are directed toward the transamidase activity. In this context, the ability of such inhibitors to control the conformational dynamics of TGase 2 emerges as an important parameter, and methods to assess this property are in great demand. Herein, we describe the application of the switchSENSE
principle to detect conformational changes caused by three irreversibly binding
-acryloyllysine piperazides, which are suitable radiotracer candidates of TGase 2. The switchSENSE
technique is based on DNA levers actuated by alternating electric fields. These levers are immobilized on gold electrodes with one end, and at the other end of the lever, the TGase 2 is covalently bound. A novel computational method is introduced for describing the resulting lever motion to quantify the extent of stimulated conformational TGase 2 changes. Moreover, as a complementary biophysical method, native polyacrylamide gel electrophoresis was performed under similar conditions to validate the results. Both methods prove the occurrence of an irreversible shift in the conformational equilibrium of TGase 2, caused by the binding of the three studied
-acryloyllysine piperazides.
We investigate the conditions which should be fulfilled to grow chains of nanosized noble metal clusters on DNA templates according to a selectively heterogeneous, template-controlled mechanism. A ...long incubation of double-stranded DNA molecules with Pt(II) complexes is necessary to obtain a template-directed formation of thin and uniform cluster chains after chemical reduction of the DNA/salt solution. Without this “activation” step, DNA acts as a nonspecific capping agent for the formed clusters and does not hinder the formation of random cluster aggregates. The effect of binding Pt(II) complexes to the DNA is investigated by UV−vis spectroscopy, electrophoresis experiments, and scanning force microscopy, revealing that the base stacking along the DNA molecule is significantly distorted but the double-stranded DNA configuration is retained. Citrate ions can be used as additional stabilizers for the heterogeneously grown metal clusters, leading to significantly more regular metal cluster chains. After a systematic variation of the absolute concentration of the reactants (Pt salt, DNA, reducing agent), we can conclude that there is an optimum concentration value for the fabrication of cluster chains and that small variations around the optimum value do not have noticeable effects on the quality of the metallization products. The described metallization procedure can be resolved into a series of simple and efficient steps, which is essential for a biomimetic fabrication of nanostructures in a reproducible way.
Dielectrophoresis-assisted growth of metallic nanowires from an aqueous salt solution has been previously reported, but so far there has been no clear understanding of the process leading to such a ...bottom-up assembly. The present work, based on a series of experiments to grow metallic nano- and microwires by dielectrophoresis, provides a general theoretical description of the growth of such wires from an aqueous salt solution. Palladium nanowires and silver microwires have been grown between gold electrodes from their aqueous salt solution via dielectrophoresis. Silver microwire growth has been observed in situ using light microscopy. From these experiments, a basic model of dielectrophoresis-driven wire growth is developed. This model explains the dependence of the growth on the frequency and the local field enhancement at the electrode asperities. Such a process proves instrumental in the growth of metallic nanowires with controlled morphology and site specificity between the electrodes.
We present a novel concept for the synthesis of a self‐thermophoretic nanoswimmer, a construct consisting of a gold nanoparticle as a heating element and an artificial DNA structure as a ...thermophoretic active part. For the latter, DNA origami technique was applied to design and synthesize rod‐like bundle structures as well as a more complex 2‐leg construct. This novel concept is based on the versatile and easy‐to‐apply DNA origami toolbox to realize Janus particle‐like structures with various geometries. We synthesized a variety of different nanoswimmers and characterized them in terms of structure, yield, and thermal stability.
Schematic representation of the construction principle of a self‐thermophoretic nanoswimmer consisting of a DNA origami structure and a gold nanoparticle. Inset: TEM image of such a nanoswimmer structure.
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