Generalized Physicochemical Model for the Natural pH Gradient in Classic IEF

In this paper we present a generalized physicochemical model for carrier ampholyte isoelectric focusing techniques. Accurate analysis of electrokinetic phenomena can only be performed when the physicochemical interactions of the carrier matrix with the electrode solutions are taken into consideration. It should also be taken into account that the majority of the constituents of electrolyte systems are weak, multivalent acids and bases, which have complex stoichiometric behavior, intricately linked with local transport phenomena. A generalized formulation to couple the migration/diffusion of weak electrolytes with transport phenomena is presented along with a broad treatment of macroscopic transport, which leads ultimately to the creation of an ampholyte pH gradient. These formulations and a novel scheme for the mechanism of mass transport constitute the core of the present paper.     

Novel Methods for Controlling the Current During Isoelectric Focusing

While studying the effect of electrochemical reactions occurring at the electrodes on achievement of steady state in isoelectric focusing (IEF) we observed an abnormal increase of the current. Because the magnitude of the current determines the progress of IEF, knowledge gained from studies of its nature and generation may enable this effect to be controlled. We observed that addition of gelatin to the electrode solutions suppresses the magnitude of the current flowing through the system; this enables IEF to be performed under conditions closer to steady state, and steady state is achieved more quickly.     

Synthesis,metal ion binding,and photochromic properties of benzo- and naphthopyrans annelated by crown ether moieties

Combining a photochromic chromene with a crown ether moiety results in systems in which photochromism and ionophoric properties could significantly influence each other. In this paper, we report the synthesis of several chromenes annelated by 15(18)-crown-5(6) ethers. The approach involves the building of the photochromic fragment upon the initial crown ether via phenols. The two main routes for chromene preparation are discussed. The complex formation of the synthesized photochromic crown-containing naphthopyran with magnesium(II) and barium(II) cations was studied. The kinetic behavior of the colored form of the compound is affected by complex formation.     

Nafion®-Separated Electrode Solutions in Isoelectric Focusing

In the present paper, we present our results from studies where the electrode solutions were separated from the carrier with the polytetrafluoroethylene-based membranes (Nafion^®). We achieved a 40-fold decrease of the average ionic strength in the gel and a twofold lowering of the current already during the first 30 min from the start of IEF, as compared to the routinely employed method. The change of these parameters made it possible to carry out the electrophoresis under conditions considerably closer to steady state, and to achieve a sharp protein separation and shortening of the duration of the process. The comparative analysis of the electrophoretic parameters in question proved that the basis for this newly developed improvement of the method is the selective restriction of the processes of migration and diffusion in the whole electrophoretic system, due to the specific properties of the semi-permeable membrane Nafion^®.

     

Fabrication of three-focal diffractive lenses by two-photon polymerization technique

Fabrication of submicron-height relief of three-focal diffractive lenses using two-photon polymerization is studied. Optical properties of the designed lenses are investigated theoretically and experimentally. The proposed design of the combined diffractive?Crefractive lenses is promising for the realization of three-focal optical ophthalmological implants with predetermined light intensity distribution between the foci. The realized three-focal optical element has a diameter size of 2.7?mm with the focal distances in the range of 27?C34?mm.     

Whole-cell aquatic biosensors

The use of various whole-cell organisms as tools for monitoring water contaminants is reviewed and evaluated. Their suitability and value for assessing a range of environmental problems from the impact of pollution, homeland defense issues, conservation, and the long-term degradation and recovery of ecosystems is discussed. Guidelines are provided for the choice of appropriate bioreporter organisms, transducers, and immobilization methods. Examples of the use of a broad spectrum of whole-cell bioreporters in assessing a variety of environmental problems are summarized.     

Determination of hydroxyl radicals from photolysis of Fe(III)-pyruvate complexes in homogeneous aqueous solution ?

Summary Benzene was used as a probe to detect ^·OH produced by photolysis of Fe(III)-pyruvate complexes in a homogeneous system. The Fe(III)-Pyr system was found to be not catalytic. Influence of pH, temperature, as well as the concentration of Fe(III) and pyruvate (Pyr) on the ^·OH yield was investigated.     

Connection between the virial equation of state and physical clusters in a low density vapor

We carry out Monte Carlo simulations of physical Lennard-Jones and water clusters and show that the number of physical clusters in vapor is directly related to the virial equation of state. This relation holds at temperatures clearly below the critical temperatures, in other words, as long as the cluster-cluster interactions can be neglected--a typical assumption used in theories of nucleation. Above a certain threshold cluster size depending on temperature and interaction potential, the change in cluster work of formation can be calculated analytically with the recently proposed scaling law. The breakdown of the scaling law below the threshold sizes is accurately modeled with the low order virial coefficients. Our results indicate that high order virial coefficients can be analytically calculated from the lower order coefficients when the scaling law for cluster work of formation is valid. The scaling law also allows the calculation of the surface tension and equilibrium vapor density with computationally efficient simulations of physical clusters. Our calculated values are in good agreement with those obtained with other methods. We also present our results for the curvature dependent surface tension of water clusters.     

Evaporation rate of nucleating clusters

The Becker-D?ring kinetic scheme is the most frequently used approach to vapor liquid nucleation. In the present study it has been extended so that master equations for all cluster configurations are included into consideration. In the Becker-D?ring kinetic scheme the nucleation rate is calculated through comparison of the balanced steady state and unbalanced steady state solutions of the set of kinetic equations. It is usually assumed that the balanced steady state produces equilibrium cluster distribution, and the evaporation rates are identical in the balanced and unbalanced steady state cases. In the present study we have shown that the evaporation rates are not identical in the equilibrium and unbalanced steady state cases. The evaporation rate depends on the number of clusters at the limit of the cluster definition. We have shown that the ratio of the number of n-clusters at the limit of the cluster definition to the total number of n-clusters is different in equilibrium and unbalanced steady state cases. This causes difference in evaporation rates for these cases and results in a correction factor to the nucleation rate. According to rough estimation it is 10(-1) by the order of magnitude and can be lower if carrier gas effectively equilibrates the clusters. The developed approach allows one to refine the correction factor with Monte Carlo and molecular dynamic simulations.