Biomedical subjects

Jean Gamby

Publications and source records attributed to Jean Gamby.

4 recordsLinked to original sources

PubMed2005

Supercapacitive admittance tomoscopy.

A sensor for measuring adsorption on a substrate has been designed including a contactless detection scheme, called supercapacitive admittance tomoscopy (SCAT). The sensor comprises a thin dielectric layer with two parallel band electrodes on the one side and a chemically modified surface on the other onto which the adsorption of molecules occurs. Upon application of a high frequency ac voltage between the two electrodes, a capacitive coupling is established across the dielectric layer, and the admittance measured depends on the surface state of the chemically modified interface. On the basis of this principle, a flow sensor has been developed to measure sensorgrams to follow the dynamics of the adsorption and has been tested for the adsorption of IgG on the modified surface.

Adsorption↗

PubMed2004

A flexible sample introduction method for polymer microfluidic chips using a push/pull pressure pump.

A push/pull sample introduction method based on push/pull pressure flow for microfluidic systems (cross, double T and multichannel structures) is presented. This leads to well-defined and controllable sample plugs even when dealing with long channels. By tuning the relative push/pull pressure, it is shown that the size of the sample plug can effectively be controlled. Good signal reproducibility upon continued sample introduction and subsequent chip electrophoresis employing fluorescence detection is demonstrated for different chip geometries (i.e. short channels and long channels). Since the performance of the method is relatively insensitive to chip geometry, it is particularly useful for polymeric prototype microchips as tedious optimization is not required. Furthermore, the push/pull sample introduction is extended to multichannel chips thus demonstrating the possibilities of applying the methodology for realizing single chip high throughput sample analysis.

Equipment Design↗

PubMed2003

Evidence for inverted region behavior in proton transfer to carbanions.

The diphenylmethane-diphenylmethyl anion acid/base couple in N,N-dimethylformamide is taken as an example for investigating the dynamics of proton transfer at carbon in a system where the acid is not activated by an electron-withdrawing group or by removal of an electron. The laser flash electron photoinjection technique is applied to the determination of the rate constant for the protonation of diphenylmethyl anion by an extended series of acids that offers a range of driving forces encompassing over 1.2 eV. The plot of the rate constant versus the pK(a) difference between diphenylmethane and the acids or of the activation free energy versus the standard free energy of the reaction exhibits clear "inverted region" behavior (by a factor of 80 in terms of rate constants). While such behaviors have been predicted and observed for outersphere electron-transfer reactions, previous evidence for proton-transfer reactions was scarce. Entropic factors, derived from an investigation of the temperature dependence of the experimental rate constants, are also discussed.

Journal Article↗

PubMed2002

Dynamics of proton transfer at nonactivated carbons from laser flash electron photoinjection experiments.

The investigation of proton exchange dynamics at carbon atoms has been so far limited to molecules activated by an electron-withdrawing substituent or by the removal of one electron yielding the corresponding cation radical. A method is proposed to overcome this limitation and extend the gathering of data to nonactivated carbon acids, RH. It consists of using photoinjected electrons to generate the radical R. from a rapidly or concertedly cleaving substrate, RX. The variations of the radical "polarogram" (in which R. is converted into R-) upon addition of an acid are then exploited to derive the protonation rate constant of R-. The method is demonstrated with the example of the diphenylmethyl carbanion. The Brönsted plot thus obtained indicates that proton transfer to this carbanion is intrinsically slow, with a barrier on the order of 1 eV. An inverted region behavior seems to appear at large driving forces.

Journal Article↗