Biomedical subjects

Leonid Ionov

Publications and source records attributed to Leonid Ionov.

5 recordsLinked to original sources

PubMed2006

Reversible switching of microtubule motility using thermoresponsive polymer surfaces.

We report a novel approach for the dynamic control of gliding microtubule motility by external stimuli. Our approach is based on the fabrication of a composite surface where functional kinesin motor-molecules are adsorbed onto a silicon substrate between surface-grafted polymer chains of thermoresponsive poly(N-isopropylacrylamide). By external temperature control between 27 and 35 degrees C, we demonstrate the reversible landing, gliding, and releasing of motor-driven microtubules in response to conformational changes of the polymer chains. Our method represents a versatile means to control the activity of biomolecular motors, and other surface-coupled enzyme systems, in bionanotechnological applications.

Acrylic Resins↗

PubMed2005

Stimuli-responsive mixed grafted polymer films with gradually changing properties: direct determination of chemical composition.

Infrared spectroscopic ellipsometry (IRSE) and visible monochromatic ellipsometry (VISE) approaches were applied to investigate the chemical structure and thickness of ultrathin polymer films. Mixed polystyrene-poly(2-vinylpyridine) and polystyrene-poly(tert-butyl acrylate) polymer grafted films (mixed brushes) with gradually changing composition (1D gradient mixed brush) along the sample were prepared on a temperature gradient stage via two subsequent "grafting to" reactions. The films were characterized by high-precision mapping VISE at a single wavelength (632.8 nm) and IRSE. The set of 1D IRSE spectra of the polymer brush films obtained by mapping the 1D gradient brush were used to estimate the thickness and the local composition of the film and to construct the 1D map of the film in terms of the chemical composition of the brush. The results were compared with the data obtained using monochromatic ellipsometry where the brush composition was estimated from the results of two subsequent measurements followed each grafting step. The measurements of the brush thickness and composition with both methods were found to be in gratifying agreement. The results demonstrate the high potential of IRSE methods for the one-step characterization (by thickness and chemical composition) of ultrathin polymer films of complex composition.

Journal Article↗

PubMed2005

Size sorting of protein assemblies using polymeric gradient surfaces.

We report on a novel approach for the size-dependent fractionation of protein assemblies on polymeric surfaces. Using a simple temperature gradient method to generate one-dimensional gradients of grafted poly(ethylene glycol), we fabricated silicon-oxide chips with a gradually changing surface density of kinesin motor molecules. We demonstrate that such a bioactive surface can be used to sort gliding microtubules according to their length. To our knowledge, this is the first example of the self-organized sorting of protein assemblies on surfaces.

Chemical Fractionation↗

PubMed2004

Inverse and reversible switching gradient surfaces from mixed polyelectrolyte brushes.

We report on a thin polyelectrolyte film (mixed polyelectrolyte brush) with a gradual change of the composition (ratio between two different oppositely charged surface-grafted weak polyelectrolytes) across the sample. The gradient of surface composition creates a gradient in surface charge density and, consequently, a gradient of the wetting behavior. The gradient film is sensitive to a pH signal and can be reversibly switched via pH change.

Journal Article↗

PubMed2003

Reversible chemical patterning on stimuli-responsive polymer film: environment-responsive lithography.

We report on a novel type of chemical patterning based on thin stimuli-responsive polymer films. The basic concept is the permanent storage (writing) of a pattern, which is reversibly developed and erased upon exposure to appropriate environment, e.g., solvent, pH, and temperature. The smart surface is fabricated from the mixed brush of poly(2-vinylpyridine) and polyisoprene. The mixed brush demonstrates switching behavior upon exposure to different solvents. Cross-linking of polyisoprene via illumination through a photomask results in formation of patterns with suppressed switching. Due to the contrast in switching between illuminated and dark areas, exposure of the smart surface to different solvents causes either reversible formation or erasing of chemical contrast between the illuminated and dark areas. Thus, the pattern surface can very locally attract colloidal particles or can be wetted by water only upon exposure to the special solvent which introduces the contrast between the illuminated and dark areas. Appearance of the patterns indicates particular environment and can be used for local switching of adsorption.

Journal Article↗