Guest editorial: Membranes and biotechnology

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26788/1/0000344.pd

Book reviews

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46733/1/251_2005_Article_BF01561580.pd

Protein-Protein Affinity Determination by Quantitative FRET Quenching.

The molecular dissociation constant, Kd, is a well-established parameter to quantitate the affinity of protein-protein or other molecular interactions. Recently, we reported the theoretical basis and experimental procedure for Kd determination using a quantitative FRET method. Here we report a new development of Kd determination by measuring the reduction in donor fluorescence due to acceptor quenching in FRET. A new method of Kd determination was developed from the quantitative measurement of donor fluorescence quenching. The estimated Kd values of SUMO1-Ubc9 interaction based on this method are in good agreement with those determined by other technologies, including FRET acceptor emission. Thus, the acceptor-quenched approach can be used as a complement to the previously developed acceptor excitation method. The new methodology has more general applications regardless whether the acceptor is an excitable fluorophore or a quencher. Thus, these developments provide a complete methodology for protein or other molecule interaction affinity determinations in solution

An analysis of carrier-mediated photodiffusion membranes

Reversible photochromic reactions can be combined with carrier-mediated transport in partially illuminated membranes to achieve very high degrees of flux enhancement. Transport across these membranes can be achieved even against a concentration gradient. Coupled systems of non-linear diffusion-reaction equations for these membranes were solved using the technique of orthogonal collocation on finite elements to study and optimize the transport across them. The results indicate that the efficiency of light utilization is maximum for thin membranes at low degrees of illumination. Carrier-mediated photodiffusion membranes in combination with a fuel cell can be used for the storage of solar energy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25139/1/0000575.pd

Light-assisted transport of nitric oxide across membranes containing nitrosyl chloride solutions

Experimental evidence for the light-assisted concentration of nitric oxide taking part in a reversible photochemical reaction in a solution is presented. For the system, nitrosyl chloride-nitric oxide, a gradient of light energy across the membrane sandwich containing nitrosyl chloride solution results in a gradient of nitric oxide concentration across the membrane. For the experimental conditions employed, nitric oxide concentration ratios of up to 15 were obtained. The experimental results are explained using an "equilibrium-facilitation" model. The photodiffusion membrane configuration of the kind discussed can be used for the chemical storage of solar energyPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26217/1/0000297.pd

A Numerical technique for solving carrier-mediated transport problems

A numerical technique and a computer program based on the method of orthogonal collocation on finite elements for solving steady state carrier-mediated transport problems is presented. The method is especially suitable in solving boundary layer type of problems as arise in carrier-mediated transport. The method uses an efficient LU decomposition of a blockdiagonal matrix. A residual criterion is used for the placement of elements which can be easily implemented using an interactive feature in the computer program. Numerical results for three different systems; a system with simple kinetics and equal diffusivities for carrier and its complex, a system with simple kinetics and unequal diffusivities and a system with complex kinetics and equal diffusivities, indicate that the method is very versatile and has very good convergence properties. The method can be used very easily for all these systems by making minor modifications to the computer program.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23958/1/0000207.pd

A Dielectric Affinity Microbiosensor

We present an affinity biosensing approach that exploits changes in dielectric properties of a polymer due to its specific, reversible binding with an analyte. The approach is demonstrated using a microsensor comprising a pair of thin-film capacitive electrodes sandwiching a solution of poly(acrylamide-ran-3-acrylamidophenylboronic acid), a synthetic polymer with specific affinity to glucose. Binding with glucose induces changes in the permittivity of the polymer, which can be measured capacitively for specific glucose detection, as confirmed by experimental results at physiologically relevant concentrations. The dielectric affinity biosensing approach holds the potential for practical applications such as long-term continuous glucose monitoring

Status of monitoring in biotechnology

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26527/1/0000066.pd

Design, manufacture and characterization of an optical fiber glucose affinity sensor based on an homogeneous fluorescence energy transfer assay system

Optical fiber biosensors based on fluorescence assays have several distinct advantages when measuring biological analytes such as metabolites, cofactors, toxins, etc. Not only are optical signals immune to electronic interferences, but the polychromatic nature of most fluorochemical assays provides more potentially useful data about the system being studied. One of the most common difficulties normally encountered with optical biosensors is the inability to routinely recalibrate the optical and electronic components of the system throughout the life of the sensor. With this in mind, an optical biosensor system for glucose has been constructed along with the peripheral electronic instrumentation. The biochemical assay is based on an homogeneous singlet/singlet energy transfer affinity assay. The sensor probe indirectly measures glucose concentrations from the level of fluorescence quenching caused by the homogeneous competition assay between TRITC labeled concanavalin A (receptor) and FITC labeled Dextran (ligand). The FITC signal is used as an indicator for glucose concentrations and the TRITC signal is used for internal calibration. Chemical derivatization procedures using succinic anhydride were developed to prevent aggregation of the receptor protein in solution, and the TRITC/ConA ratios were optimized to achieve the best sensor performance. Using this sensor system, the FITC-Dextran detection limit was 0.05 [mu]g/ml and glucose concentrations up to 1600 mg/dl could be detected with a time response of approximately 10 min.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30643/1/0000285.pd

The permeability of gases through reacting solutions: the carbon dioxide--bicarbonate membrane system

The transport of a gas across a stationary liquid film containing reactive species is investigated for the purpose of determining gas permeabilities or mass transfer coefficients in reacting solutions. Under limiting conditions when the reaction time constant far exceeds the diffusional time constant, the flux of the transported gas follows Fick's law of diffusion. Analytical series solution for the contribution of the chemical reaction to the transport process is obtained using the technique of perturbation analysis; criteria for the validity of various terms in the series solution are presented. The permeability of carbon dioxide in water and in 1N NaHCO3-Na2CO3 solution is estimated. It is shown that a high degree of accuracy in the data is necessary for obtaining separate estimates of diffusivity and solubility by this technique.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22433/1/0000884.pd