DNA Nanodevices with Selective Immune Cell Interaction and Function

DNA nanotechnology produces precision nanostructures of defined chemistry. Expanding their use in biomedicine requires designed biomolecular interaction and function. Of topical interest are DNA nanostructures that function as vaccines with potential advantages over nonstructured nucleic acids in terms of serum stability and selective interaction with human immune cells. Here, we describe how compact DNA nanobarrels bind with a 400-fold selectivity via membrane anchors to white blood immune cells over erythrocytes, without affecting cell viability. The selectivity is based on the preference of the cholesterol lipid anchor for the more fluid immune cell membranes compared to the lower membrane fluidity of erythrocytes. Compacting DNA into the nanostructures gives rise to increased serum stability. The DNA barrels furthermore functionally modulate white blood cells by suppressing the immune response to pro-inflammatory endotoxin lipopolysaccharide. This is likely due to electrostatic or steric blocking of toll-like receptors on white blood cells. Our findings on immune cell-specific DNA nanostructures may be applied for vaccine development, immunomodulatory therapy to suppress septic shock, or the targeting of bioactive substances to immune cells

Design, assembly, and characterization of membrane-spanning DNA nanopores

DNA nanopores are bio-inspired nanostructures that control molecular transport across lipid bilayer membranes. Researchers can readily engineer the structure and function of DNA nanopores to synergistically combine the strengths of DNA nanotechnology and nanopores. The pores can be harnessed in a wide range of areas, including biosensing, single-molecule chemistry, and single-molecule biophysics, as well as in cell biology and synthetic biology. Here, we provide a protocol for the rational design of nanobarrel-like DNA pores and larger DNA origami nanopores for targeted applications. We discuss strategies for the pores’ chemical modification with lipid anchors to enable them to be inserted into membranes such as small unilamellar vesicles (SUVs) and planar lipid bilayers. The procedure covers the self-assembly of DNA nanopores via thermal annealing, their characterization using gel electrophoresis, purification, and direct visualization with transmission electron microscopy and atomic force microscopy. We also describe a gel assay to determine pore–membrane binding and discuss how to use single-channel current recordings and dye flux assays to confirm transport through the pores. We expect this protocol to take approximately 1 week to complete for DNA nanobarrel pores and 2–3 weeks for DNA origami pores

The Jurassic–Cretaceous depositional and tectonic evolution of the southernwestern margin of the Neotethys Ocean, Northern Oman and United Arab Emirates

The concept that the autochthonous, parautochthonous and allochthonous Permian–Cretaceous sequences in the United Arab Emirates (UAE) and Oman record the transition from platform, slope to basin sedimentation within the southern part of Neotethys has been fundamental to the interpretation of the geological history of the region. The results of a major geological mapping programme of the UAE, carried out by the British Geological Survey for the Federal Government of the UAE, coupled with the detailed examination of key sections within northern Oman has led to a re-evaluation of the geological evolution of this region. This detailed study has led to a greater appreciation of the sedimentology and depositional setting of the sediments laid down along the northeastern Arabian continental margin during the Jurassic to Cretaceous, allowing a more refined model of Neotethys Ocean basin evolution to be established. The model charts the progressive breakup of the Arabian continental margin and closure of Neotethys during the mid to late Cretaceous and is divided into three main stages: Stage 1—Initial rifting and formation of the Neotethys Ocean, followed by a prolonged period of stable, passive margin sedimentation which extended from the Permian to Late Jurassic times; Stage 2—Uplift and erosion of the shelf margin during the Late Jurassic to Early Cretaceous, coincident with increased carbonate-clastic sedimentation in the outer ramp, distal slope and basinal areas; Stage 3—Increased instability during the Late Cretaceous leading to the breakup of the platform margin and foreland basin sedimentation accompanying the obduction of the Oman-UAE ophiolite. Data obtained for the upper part of the platform and platform margin to slope successions has revealed that the topography of the “shelf”-slope-basinal margin was more subdued than previously thought, with this more gentle ramp margin morphology persisting until early to mid-Cretaceous times when the platform margin started to become unstable during ophiolite obduction. The thrust-repeated allochthonous sedimentary rocks of the Hamrat Duru Group were deposited on the outer platform margin/lower slope rise to basinal plain of this basin margin and includes the dismembered remains of two turbidite fan systems which fed carbonate-rich detritus into deeper parts of the ocean. A re-evaluation of the chert-rich sequences, previously equated with deposition on the abyssal plain of Neotethys, has led to the conclusion that they may record sedimentation at a much shallower level within a starved ocean basin, possibly in a mid-ramp (above storm wave base) to outer ramp setting. A marked change in basin dynamics occurred during the mid-Cretaceous leading to the development of a shallow ramp basin margin in Oman with terrestrial to shallow marine sedimentary rocks interdigitating with red siliceous mudstones. By contrast, the contemporaneous succession in the Dibba Zone of the UAE indicates considerable instability on a steep shelf break. This instability is recorded by the presence of several major olistostrome deposits within the Aruma Group of the UAE which are thought to have been generated in advance of the rapidly obducting Oman-UAE ophiolite

A Biomimetic DNA‐Based Membrane Gate for Protein‐Controlled Transport of Cytotoxic Drugs

DNA nanotechnology can be used to rationally design a molecular gate to control the transport of small‐molecule drugs across bilayer membranes. The DNA pore with a thrombin‐binding aptamer lid opens in the presence of thrombin to increase the transport of the cytotoxic drug topotecan by 330‐fold. The nanodevice could be adapted for a range of different protein triggers with applications in biosensing, research, and biomedicine

A Biomimetic DNA-Based Membrane Gate for Protein-Controlled Transport of Cytotoxic Drugs

Chemistry is ideally placed to replicate biomolecular structures with tuneable building materials. Of particular interest are molecular nanopores, which transport cargo across membranes, as in DNA sequencing. Advanced nanopores control transport in response to triggers, but this cannot be easily replicated with biogenic proteins. Here we use DNA nanotechnology to build a synthetic molecular gate that opens in response to a specific protein. The gate self-assembles from six DNA strands to form a bilayer-spanning pore, and a lid strand comprising a protein-binding DNA aptamer to block the channel entrance. Addition of the trigger protein, thrombin, selectively opens the gate and enables a 330-fold increase inw the transport rate of small-molecule cargo. The molecular gate incorporates in delivery vesicles to controllably release enclosed cytotoxic drugs and kill eukaryotic cells. The generically designed gate may be applied in biomedicine, biosensing or for building synthetic cells

A Biomimetic DNA‐Based Membrane Gate for Protein‐Controlled Transport of Cytotoxic Drugs

DNA nanotechnology can be used to rationally design a molecular gate to control the transport of small‐molecule drugs across bilayer membranes. The DNA pore with a thrombin‐binding aptamer lid opens in the presence of thrombin to increase the transport of the cytotoxic drug topotecan by 330‐fold. The nanodevice could be adapted for a range of different protein triggers with applications in biosensing, research, and biomedicine

Stratigraphy, structure, and metamorphism in the central Panamint Mountains (Telescope Peak quadrangle), Death Valley area, California: Summary

The Telescope Peak quadrangle is located in the central Panamint Mountains, which form the western boundary of the central part of Death Valley, California. The central Panamint Mountains are composed of lower Precambrian gneiss and schist and upper Precambrian sedimentary rocks. These rocks were metamorphosed during late Mesozoic time and deformed during late Mesozoic and Cenozoic time. The stratigraphy of the upper Precambrian rocks indicates a tectonically active depositional environment during the initiation of the Cordilleran geosyncline; the petrology of the metamorphic rocks indicates that the metamorphism occurred along a gradient with a low dp/dT; and the structure suggests an evolution from a compressional to an extensional tectonic regime during late Mesozoic and Tertiary time. This report summarizes the results of geologic mapping in the Telescope Peak quadrangle, and Figure 1 is a generalized version of the geologic map of the Telescope Peak 15' quadrangle by Albee, Labotka, Lanphere, and McDowell (1980). A more complete discussion of the geology occurs in Part II of this article

Exploring the multicollection approach for the 40Ar/39Ar dating technique

International audienceWe present an original analytical system for 40Ar/39Ar dating. It makes use of a 180° sector multicollection mass spectrometer equipped with five Faraday cups, which renders peak switching unnecessary during argon isotopic analyses. Compared to the single-collector approach commonly used for argon isotopic analyses, our system presents greater stability during data acquisition. Faraday cup efficiencies, which can be a limiting factor for the multicollection mass spectrometer, were highly reproducible. The analytical validity of the 40Ar/39Ar ages obtained using this new mass spectrometer has been preliminarily tested using geological standard minerals (MMhb-1, FCT-San, and HD-B1) commonly used as neutron fluence monitors. Independent plateau age determinations of Ethiopian samples duplicated over a 1-year interval demonstrated the reproducibility of the analyses. The results of these measurements highlight the good behavior of this new instrument for 40Ar/39Ar step heating dating. The age reproducibility of successive steps leads to analytical errors lower than 0.1% for well-behaved samples. This system, still in its initial stage of development, represents an alternative solution that is worth exploring in order to improve absolute dating by the 40Ar/39Ar technique