Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “layer”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources
PubMed2007

From cloudy to transparent: chain rearrangement in hydrogen-bonded layer-by-layer assembled films.

The cloudiness of hydrogen-bonded LBL films assembled from polyvinylpyrrolidone (PVPON) and poly(acrylic acid) (PAA) is studied in detail by two approaches: spectroscopy (Fabry-Pérot fringes) and microscopy (AFM). Fabrication parameters such as temperature, molecular weight, pH value, and rinsing time, have notable influences on film cloudiness. The buildup of the PVPON/ PAA film is a two-stage process of adsorption and chain rearrangement. Generally, adsorption is fast, while chain rearrangement is slow. The fast adsorption process traps defects, whereas the relatively slow chain-rearrangement process can not heal the defects in time; therefore; the number of defects continuously increases as LBL assembly proceeds, and a cloudy, heterogeneous film is produced. However, the as-prepared cloudy films become transparent and homogeneous on subsequent annealing in acidic water. UV/Vis spectroscopy and fluid AFM were applied to monitor this transition ex situ and in situ, respectively. It is found that increasing the annealing temperature accelerates the transition from cloudy to transparent, and the transition of the film made from higher molecular weight polymer is slower.

Journal Article↗
PubMed1990

Enzyme visualization with partially dehydrated agarose substrate layers: detection of paraoxonase after thin-layer isoelectric focusing in agarose.

A new approach is described for studying the polymorphism of paraoxon hydrolyzing serum esterases after isoelectric focusing of native sera. Enzyme visualization is performed by a modified sandwich procedure which is faster and also affords higher resolution and considerably improved sensitivity. Up to seven paraoxon splitting isoenzymes can be visualized and clearly distinguished from arylesterases and phosphatases by using 3-naphtyl acetate, paraoxon, 5-bromo-4-chloro-3-indolyl acetate and 5-bromo-4-chloro-3-indolyl phosphate as substrates. The new technique is also able to differentiate between paraoxonase isoenzymes sensitive to EDTA and those which are EDTA-stable. Immunofixation with anti-human serum albumin-antibodies revealed similar isoelectric points for these isoenzymes, although they are not assumed to be identical. The new technique may prove useful in other applications of enzyme visualization where diffusion of enzymes and/or cleavage products is the major problem.

Aryldialkylphosphatase↗
PubMedDate not supplied

Layer-by-layer analysis of the components of thalamocortical responses of the sensorimotor cortex in the rabbit during ontogenesis.

The complex dynamics of the changes in the spatial-temporal disposition of the heterocomponent thalamocortical responses (TCR) when traversing the sensorimotor cortex (SMC), are governed by the characteristics of the electrogenesis of each of the components of the TCR, the age of the animal, and the frequency of stimulation of the ventroposterolateral (VPL) nucleus of the thalamus. At the same time, the transformation of the electrical profile of the second positive component (PC-2) of the TCR during traversal of the SMC may suggest the algebraic summation in this component of the bioelectrical processes of several sources of generation (of the inverted and noninverted PC-2). The characteristics of the ontogenetic dynamics of the profiles of the biological fields of the third negative component (NC-3) of the TCR which were found may be the result of age-related stages of development and of a change in the embryonal mechanisms of electrogenesis to the definitive mechanisms in the presence of outwardly similar negativities.

Animals↗
PubMed2005

Construction of anti-adhesive and antibacterial multilayer films via layer-by-layer assembly of heparin and chitosan.

Chitosan as an antibacterial agent and heparin as an anti-adhesive agent were alternatively deposited onto aminolyzed poly(ethylene terephthalate) (PET) films to construct anti-adhesive and antibacterial multilayer films. The contact-angle and UV data verified the progressive buildup of the multilayer film by alternate deposition of the polyelectrolytes. The properties of multilayer films were investigated by contact angle, atomic force microscopy (AFM), lateral force microscopy (LFM) and UV spectra. The results of initial adhesion of Escherichia coli (E. coli) on PET substrates showed that the number of E. coli adhered onto the control PET was in a much greater extent than onto the chitosan/heparin multilayer films, and the number of adhesive bacteria decreased with a decrease in assembly pH. The in vitro antibacterial test indicated that a multilayer of chitosan/heparin could kill the bacteria effectively. The number of viable bacteria decreased by 7% after 7 h in contact with the control PET films, but by 46-68% for the multilayer-modified PET films. Only 3-8% of the cells were viable for the multilayer-modified PET films after 24h. It is interesting to find the assembly pH has a remarkable effect on the antibacterial property of the multilayer. The number of viable bacteria on the multilayer assembled at pH = 3.8, 2.9 and 6.0 decreased by 68%, 58% and 46%, respectively. Such an easy processing and shape-independent method to prepare an anti-adhesive and antibacterial surface may have good potential for surface modification of cardiovascular devices.

Anti-Bacterial Agents↗