Self-assembly and applications of nucleic acid solid-state films.

While most nucleic acid (NA)-lipid or NA-polymer complexes are studied in solution, there is growing interest in understanding their properties as naturally derived, biodegradable, biocompatible, solid-state materials with tailorable properties influenced by environmental parameters. Therapeutic and cell programming applications comprise an important new research field, particularly in gene transfection and silencing using plasmid DNA and siRNA with targeted local delivery for use in cell culture. Dried solid films have lower nuclease degradation, fewer barriers to long term storage, and allow localized delivery by direct implantation in combination with controlled release and dosage adjustment.

Temperature and time-resolved total internal reflectance fluorescence analysis of reusable DNA hydrogel chips.

Total internal reflection fluorescence (TIRF) coupled with hydrogel-DNA droplet microarrays covalently bound on PMMA substrates presents a reusable, sensitive platform for evaluating DNA hybridization and for rapid biochip development. Hydrogel microarrays, which contain covalently bound DNA probes, are created via a simple printing and photocross-linking process. TIRF measurements of the arrays display robust reusability, show linear sensitivity down to 5 fmol of fluorescently labeled target DNA, and are sensitive to single basepair mismatches.

Structural responses of DNA-DDAB films to varying hydration and temperature.

The structure of a DNA-dimethyldidodecylammonium bromide (DDAB) film was recently described to undergo a distinctive transition in response to the water content in the surrounding environment. The existence, preparation, and basic properties of DNA-surfactant films have been known in the literature for some time. Here, we describe the structural response of DNA-DDAB films to environmental changes, particularly temperature and humidity, in greater detail revealing new structural states.

Linker chemistry determines secondary structure of p5314-29 in peptide amphiphile micelles.

Biofunctional micelles formed via self-assembly of synthetic peptide-lipid conjugates are a class of promising biomaterials with applications in drug delivery and tissue engineering. The micelle building block, termed peptide amphiphile, consists of a lipid-like chain covalently linked through a spacer to a peptide headgroup. Self-assembly results in formation of a hydrophobic core surrounded by a dense shell with multiple, functional peptides.

Comment on "Analytical investigation of the open boundary conditions in the Nagel-Schreckenberg model".

In their recent paper [Phys. Rev. E 79, 031115 (2009)], Ning Jia and Shoufeng Ma used some Markov chain arguments for the analytical description of inflow in the deterministic Nagel-Schreckenberg model with open boundaries.

Tracking transcription factor complexes on DNA using total internal reflectance fluorescence protein binding microarrays.

We have developed a high-throughput protein binding microarray (PBM) assay to systematically investigate transcription regulatory protein complexes binding to DNA with varied specificity and affinity. Our approach is based on the novel coupling of total internal reflectance fluorescence (TIRF) spectroscopy, swellable hydrogel double-stranded DNA microarrays and dye-labeled regulatory proteins, making it possible to determine both equilibrium binding specificities and kinetic rates for multiple protein:DNA interactions in a single experiment. DNA specificities and affinities for the general transcription factors TBP, TFIIA and IIB determined by TIRF-PBM are similar to those determined by traditional methods, while simultaneous measurement of the factors in binary and ternary protein complexes reveals preferred binding combinations.

Reversible structural switching of a DNA-DDAB film.

We describe the novel structure and behavior of a DNA-DDAB complex film cast from an organic solvent and exhibiting a structural switching transition as it is dried or wetted with water. The film was easily prepared by formation of a complex between the negatively charged phosphate groups of DNA and the positively charged headgroup of the surfactant DDAB. This complex was then purified, dried, dissolved in 2-propanol, and cast onto a glass slide to form a self-standing film by means of slow evaporation.

Noncovalent self-assembling nucleic acid-lipid based materials.

We detail a method originally described by Okahata et al. (Macromol. Rapid Commun.

Schlieren visualization of ultrasonic wave fields with high spatial resolution.

The visualization of ultrasonic wave fields in optically transparent liquids using the acousto-optic interaction is a well proven tool for the experimental investigation of wave propagation including wave field interaction effects with certain discontinuities and obstacles like reflection, refraction, and diffraction effects as well as for transducer testing and design. For high resolution visualization of wave fields including pulsed waveforms, pulsed light sources and sensitive optical imaging sensors with certain specifications are needed. In this paper the technical requirements of optical and electronic components for high resolution visualization of ultrasound wave fields will be presented.

High activity of enzymes immobilized in colloidal nanoreactors.

We present a novel type of nanoreactor suitable for the immobilization of enzymes. The particles used consist of a polystyrene core onto which long chains of poly(acrylic acid) are grafted ("spherical polyelectrolyte brush"). Proteins adsorbed spontaneously onto these particles from aqueous solutions if the ionic strength is low.