Two-step elution of human serum proteins from different glass-modified bioactive surfaces: a comparative proteomic analysis of adsorption patterns

Plasma protein adsorption patterns on surfaces may give vital information to evaluate biocompatibility of biomaterials designed for direct blood-contacting applications or tissue integration. Adsorption of human serum proteins on four different types of biomaterials (glass, aminosilanized glass, hyaluronan and sulfated hyaluronan) was analyzed by two-dimensional electrophoresis. Desorption of proteins from the surfaces was first classically achieved by sodium dodecyl sulfate (SDS) elution. We introduced a second elution step (by use of isoelectric focusing (IEF) sample buffer consisting of urea, 3-[(3-cholamidopropyl)dimethylammonio]-1-propansulfonate, and dithioerythritol) which allows more stringent elution conditions and is a tool to evaluate the protein adsorption strength to biomaterials. Moreover, the two-step elution may discriminate between irreversible and reversible adsorption of plasma proteins for biomaterials, thus helping to elucidate the structure of protein multilayers which form a complex system at the surfaces. The IEF sample buffer proved not to alter the biomaterial structure and integrity. Hydrophobic bonds resulted to be the main strength driving protein adsorption onto our biomaterials. Apolipoproteins were the most important proteins interacting with the surfaces suggesting that high-density lipoprotein (HDL) particles could play a role in biocompatibility due to their beneficial effects on endothelial cells.     

Analogue simulation of stochastic parametric oscillators III: A new resonance mechanism

The Duffing oscillator with fluctuating elastic constant is simulated by means of an analogue circuit. The regime oflarge intensity andlong correlation time of the applied fluctuation is shown not to be correctly reproduced by previous theoretical predictions. The results found are interpreted in terms of the deterministic counterpart of the system under study (parametric Duffing oscillator). The new resonance mechanism provides a more convincing picture of the relaxation dynamics taking place in the stochastic pumped Duffing oscillator, especially in the underdamped limit.     

PMMA nanofibers production by electrospinning

Electrospinning is a process by which polymer nanofibers (with submicron scale diameters) can be formed when a droplet of viscoelastic polymer solution is subjected to high voltage electrostatic field. As this droplet travels in air, the solvent evaporates leaving behind a charge fiber that can be electrically deflected on a substrate. A series of nanofibers with various wt.% of PMMA (poly-methyl-methacrylate) to acetone were produced and characterized regarding their morphology and chemical composition. The nanofibers were characterized by Secondary Electron Microscopy, Atomic force microscopy and X-ray photoelectron spectroscopy.     

Is there any fast sound in water?

We measured the dynamic structure factor S(Q,omega) of liquid and undercooled water down to 253 K in the Q approximately 0.02-0.1 nm;{-1} momentum transfer region. We observe the neat departure of the apparent speed of sound from the adiabatic regime as a function of decreasing temperature. Our evaluation of the infinite-frequency limit of sound velocity, c_{infinity}, matches with the results obtained in the high momentum transfer limit by inelastic neutron and x-ray scattering. These results strongly support the viscoelastic interpretation of the dynamics of water. Hence, we propose to call c_{infinity} the high-frequency speed of sound and to abandon the term fast sound, which recalls a propagation mechanism through lighter atoms, like in gas mixtures.     

Energy dependence of multiplicity in proton-nucleus collisions and models of multiparticle production

This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett. 50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratioR _em = 〈n _s〉/〈n _ch〉, where 〈n _ch〉 is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1·6 at 68 GeV/c and attains a constant value of 1·71 ± 0·04 in the region 200 to 8000 GeV/c. Furthermore,R _em = 1·71 implies an effectiveA-dependence ofR _A =A ^0.18,i.e., a very weak dependence. Predictions ofR _em on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production.     

Structure of water-in-oil microemulsions of AOT by infrared spectroscopy

Summary The structure of water in water/AOT/n-heptane reverse micelles has been studied as a function of the [H₂O]/[AOT] ratio (W) by using the absorption IR due to O−H stretching modes in the 3800–3000 cm⁻¹ range. The results show that the IR spectra can be expressed as a sum of contributions from bound- and bulk-like water. The fraction of water in the two ?regions? within the water pool was evaluated as a function ofW. The ?bound? water region seems to hold 3.5 water molecules (corresponding to 7 O−H oscillators) per AOT molecule and its formation is nearly complete atW>6. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Stochastic resonance in paramagnetic resonance systems

Experimental evidence of the stochastic resonance phenomenon in an electron paramagnetic resonance (EPR) system is reported. The amplitude and phase response of the EPR system operating in bistable conditions are measured for increasing values of the noise intensity. Theoretical predictions based on a simple dynamical model for the relevant system observables are shown to be in good agreement with experimental results.     

Amplitude modulated transversal and longitudinal EPR spectroscopy

The amplitude modulated EPR spectroscopy is analyzed both in the time and the frequency domain. The results of numerical calculations and analytical approximate treatments indicate that the signal lineshape is differently affected by relaxation mechanisms when transversal or longitudinal detection is used in spectroscopies with variable frequencies of modulation. Measurements of longitudinally detected electron-spin double resonance obtained in dependence on the frequency of modulation confirm the lineshape expected by the theoretical analysis.     

Self-association behaviour of alcohols in diluted aqueous solutions

Summary Our recent studies related to the properties of alcohol/water mixtures show the occurrence of some kind of molecular aggregation in the water-rich region of composition beyond a threshold alcohol concentrationx ₂ ^*. The observed behaviour suggests that forx ₂<x ₂ ^* the alcohol molecules are essentially dispersed and surrounded by ?water cages? where the short-range order and microdynamic of water molecules are changed with respect to those of pure water. Alcohol molecules are in mutual contact at higher concentration only when almost all water is involved in hydration shells of alcohol molecules. The structural transition atx ₂ ^* resembles, for some aspect, the micellization process. The main results of these investigations are reviewed and discussed in this paper. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8 1994