9 research outputs found
First Step Towards Larger DNA-Based Assemblies of Fluorescent Silver Nanoclusters: Template Design and Detailed Characterization of Optical Properties
Besides being a passive carrier of genetic information, DNA can also serve as an architecture template for the synthesis of novel fluorescent nanomaterials that are arranged in a highly organized network of functional entities such as fluorescent silver nanoclusters (AgNCs). Only a few atoms in size, the properties of AgNCs can be tuned using a variety of templating DNA sequences, overhangs, and neighboring duplex regions. In this study, we explore the properties of AgNCs manufactured on a short DNA sequence—an individual element designed for a construction of a larger DNA-based functional assembly. The effects of close proximity of the double-stranded DNA, the directionality of templating single-stranded sequence, and conformational heterogeneity of the template are presented. We observe differences between designs containing the same AgNC templating sequence—twelve consecutive cytosines, (dC)12. AgNCs synthesized on a single “basic„ templating element, (dC)12, emit in “red„. The addition of double-stranded DNA core, required for the larger assemblies, changes optical properties of the silver nanoclusters by adding a new population of clusters emitting in “green„. A new population of “blue„ emitting clusters forms only when ssDNA templating sequence is placed on the 5′ end of the double-stranded core. We also compare properties of silver nanoclusters, which were incorporated into a dimeric structure—a first step towards a larger assembly
The Problems of Passive Remote Sensing of the Earth’s Surface in the Range of 1.2–1.6 GHz
The main problems of remote sensing of the Earth’s surface within the frequency range 1.2–1.6 GHz are discussed. They are related to the resonant quantum properties of the radio wave propagation medium in the lower ionosphere. It is shown that, for the passive remote sensing, the main source is incoherent microwave radiation of the D and E ionospheric layers in the decimeter range. For the first time, a theoretically grounded principally new scheme of measurements is suggested. The scheme assumes that the radiation source exists below the satellite orbit and accounts for the fact that two types of radiation (direct and reflected) reach the satellite sensor. The separation of the respective fluxes is a serious problem that should be solved for the correct interpretation of the measurements. The question is raised regarding the correct calibration of measuring equipment, depending on the current state of the ionosphere
Radiation exposure does not significantly contribute to the risk of recurrence of Chernobyl thyroid cancer.
Papillary thyroid carcinoma (PTC) in patients exposed to environmental radioiodine after the Chernobyl accident is thought to have a relatively aggressive clinical course. Long-term results of treatment are not well known, especially in comparison with sporadic PTC
Dynamic Behavior of RNA Nanoparticles Analyzed by AFM on a Mica/Air Interface
RNA is an attractive biopolymer for
engineering self-assembling
materials suitable for biomedical applications. Previously, programmable
hexameric RNA rings were developed for the controlled delivery of
up to six different functionalities. To increase the potential for
functionalization with little impact on nanoparticle topology, we
introduce gaps into the double-stranded regions of the RNA rings.
Molecular dynamic simulations are used to assess the dynamic behavior
and the changes in the flexibility of novel designs. The changes suggested
by simulations, however, cannot be clearly confirmed by the conventional
techniques such as nondenaturing polyacrylamide gel electrophoresis
(native-PAGE) and dynamic light scattering (DLS). Also, an in vitro
analysis in primary cultures of human peripheral blood mononuclear
cells does not reveal any discrepancy in the immunological recognition
of new assemblies. To address these deficiencies, we introduce a computer-assisted
quantification strategy. This strategy is based on an algorithmic
atomic force microscopy (AFM)-resolved deformation analysis of the
RNA nanoparticles studied on a mica/air interface. We validate this
computational method by manual image analysis and fitting it to the
simulation-predicted results. The presented nanoparticle modification
strategy and subsequent AFM-based analysis are anticipated to provide
a broad spectrum approach for the future development of nucleic acid-based
nanotechnology
Dynamics of Synaptic SfiI-DNA Complex: Single-Molecule Fluorescence Analysis
A single-molecule analysis was applied to study the dynamics of synaptic and presynaptic DNA-protein complexes (binding of two DNA and one DNA duplex, respectively). In the approach used in this study, the protein was tethered to a surface, allowing a freely diffusing fluorescently labeled DNA to bind to the protein, thus forming a presynaptic complex. The duration of fluorescence burst is the measure of the characteristic lifetime of the complex. To study the formation of the synaptic complex, the two SfiI-bound duplexes with the labeled donor and acceptor were used. The synaptic complex formation by these duplexes was detected by the fluorescence resonance energy transfer approach. The duration of the fluorescence resonance energy transfer burst is the measure of the characteristic lifetime of the synaptic complex. We showed that both synaptic and presynaptic complexes have characteristic dissociation times in the range of milliseconds, with the synaptic SfiI-DNA complex having the shorter dissociation time. Comparison of the off-rate data for the synaptic complex with the rate of DNA cleavage led to the hypothesis that the complex is very dynamic, so the formation of an enzymatically active synaptic complex is a rather rare event in these series of conformational transitions