A simple method for kinetic control of DNA-induced nanoparticle assembly

A regulation of the kinetic behavior in DNA-based nanosystems is required for emerging applications in sensing, nanodevice assembling, and gene delivery. Here we describe a broadly applicable method for controlling the kinetics of DNA-mediated nanoparticle self-assembly by tailoring the DNA-capping between single-stranded and partially rigid double-stranded designs. An effect of enhanced assembly kinetics was facilitated by the added rigidity which reduced chain entropy while extending crucial linker segments away from the nanoparticle interface where they are known to coordinate.     

Styryl Dyes as Two-Photon Excited Fluorescent Probes for DNA Detection and Two-Photon Laser Scanning Fluorescence Microscopy of Living Cells

Spectral-fluorescent properties of benzothiazole styryl monomer (Bos-3) and homodimer (DBos-21) dyes in presence of DNA were studied. The dyes enhance their fluorescence intensity in 2–3 orders of magnitude upon interaction with DNA. Studied styrylcyanines in DNA presence demonstrate rather high values of two-photon absorption (TPA) cross-section, which are comparable with the values of TPA cross section of the rhodamine dyes. An applicability of the styrylcyanines as probes for the fluorescence microscopy of living cells was studied. It was shown that both dyes are cell-permeable but homodimer dye DBos-21 produces noticeably brighter staining of HeLa cells comparing with monomer dye Bos-3. Molecules of DBos-21 initially bind to the nucleic acids- containing cell organelles (presumable mitochondria) and are able to penetrate into the cell nucleus. Thus, homodimer styryl DBos-21 dye is viewed as efficient stain for single-photon and two-photon excitation fluorescence imaging of living cells.     

Study of the island morphology at the early stages of Fe/Mo(110) MBE growth

We present theoretical study of morphology of Fe islands grown at Mo(110) surface in submonolayer MBE mode. We utilize atomistic SOS model with bond counting, and interactions of Fe adatom up to third nearest neighbors. We performed KMC simulations for different values of adatom interactions and varying temperatures. We have found that, while for the low temperature islands are fat fractals, for the temperature 500 K islands have faceted rhombic-like shape. For the higher temperature, islands acquire a rounded shape. In order to evaluate qualitatively morphological changes, we measured average aspect ratio of islands. We calculated dependence of the average aspect ratio on the temperature, and on the strength of interactions of an adatom with neighbors.      

NMR relaxation interference effects and internal dynamics in gamma-cyclodextrin

Multiple-magnetic field (9.4, 14.1 and 21.1 T) measurements of (13)C spin-lattice and spin-spin relaxation rates, the heteronuclear Overhauser enhancement and cross-correlated relaxation rates (CCRRs) in the methylene groups are reported for gamma-cyclodextrin in water/dimethylsulfoxide solution at 323 and 343K. The CCRRs are obtained from differences in the initial relaxation rates of the components of the CH(2) triplet in the (13)C spectra. The relaxation data are analyzed using the Lipari-Szabo approach and a novel modification of the two-site jump model. According to the latter model, inclusion of the dipolar (CH,CH(')) cross-correlated longitudinal and transverse relaxation is important for estimating the rate of the conformational jumps in the hydroxymethyl group. Using the dynamic information from the jump model, we have also used the differences in the initial relaxation rates for the triplet components to estimate the anisotropy of the chemical shielding tensor.     

Synthesis,anticancer and antiviral activities of novel thiopyrano[2,3-d]thiazole-6-carbaldehydes

Novel rel-(6R,7R)-2-oxo-7-phenyl-3,5,6,7-tetrahydro-2H-thiopyrano[2,3-d]thiazole-6-carbaldehydes were synthesized via regio- and diastereoselective hetero-Diels-Alder reaction of 5-arylidene-4-thioxo-2-thiazolidinones with acrolein. The synthesized compounds were evaluated for anticancer and antiviral activities by the National Institutes of Health (NIH) following US NCI and AACF protocols. Anticancer activity screening on NCI60 cell lines allowed identification of 7-phenyl-2-oxo-7-phenyl-3,5,6,7-tetrahydro-2H-thiopyrano[2,3-d]thiazole-6-carbaldehyde 3a with the highest level of antimitotic activity against leukemia with mean GI₅₀/TGI values 1.26/25.22 μM. The screening of antiviral activity lead to identification of 7-(4-methoxyphenyl)-2-oxo-3,5,6,7-tetrahydro-2H-thiopyrano[2,3-d]thiazole-6-carbaldehyde 3b with a promising influence on EBV virus (EC₅₀ = 0.07 μM, SI = 3279) and moderate effect on Herpes simplex virus type 1 and Varicella zoster virus and 7-[4-(benzyloxy)phenyl]-2-oxo-3,5,6,7-tetrahydro-2H-thiopyrano[2,3-d][1,3]thiazole-6-carbaldehyde 3e with a promising influence on Hepatitis C virus (EC₅₀ = 12.6 μM, SI = 43.1).     

Voltammetric Determination of Cymoxanil and Famoxadone at Different Types of Carbon Electrodes

Differential pulse voltammetry (DPV) at a carbon fibre rod electrode (CFRE) and a capillary carbon paste electrode (CPE) have been used for the determination of pesticides cymoxanil and famoxadone, respectively. In the cathodic potential range, optimum conditions were found for the determination of cymoxanil by DPV at CFRE at pH 4 with limit of quantification (L_Q) of 5.9×10^?7 mol L^?1. In the anodic area, determination of famoxadone by DPV at CPE was performed at optimum pH 2 with L_Q=1.4×10^?7 mol L^?1. Practical applicability of the newly developed methods was verified on spiked samples of river water and soil.     

A Rotational BODIPY Nucleotide: An Environment‐Sensitive Fluorescence‐Lifetime Probe for DNA Interactions and Applications in Live‐Cell Microscopy

Fluorescent probes for detecting the physical properties of cellular structures have become valuable tools in life sciences. The fluorescence lifetime of molecular rotors can be used to report on variations in local molecular packing or viscosity. We used a nucleoside linked to a meso‐substituted BODIPY fluorescent molecular rotor ( dC^bdp ) to sense changes in DNA microenvironment both in vitro and in living cells. DNA incorporating dC^bdp can respond to interactions with DNA‐binding proteins and lipids by changes in the fluorescence lifetimes in the range 0.5–2.2 ns. We can directly visualize changes in the local environment of exogenous DNA during transfection of living cells. Relatively long fluorescence lifetimes and extensive contrast for detecting changes in the microenvironment together with good photostability and versatility for DNA synthesis make this probe suitable for analysis of DNA‐associated processes, cellular structures, and also DNA‐based nanomaterials.