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A new method is proposed for the fabrication of a well-defined size and shape distribution of silver nanoparticles in solution; the method employs direct laser irradiation of an aqueous solution containing a silver salt and a surfactant in the absence of reducing agents.

A new protein fractionation technique based on off-gel isoelectric focusing (IEF) is presented, where the proteins are separated according to their isoelectric point (pI) in a multiwell device with the advantage to be directly recovered in solution for further analysis. The protein fractions obtained with this technique have then been characterized with polymer nanoelectrospray for mass spectrometry (MS) analyses or with Bioanalyzer for mass identification. This methodology shows the possibility of developing alternatives to the classical two-dimensional (2-D) gel electrophoresis. One species numerical simulation of the electric field distribution during off-gel separation is also presented in order to demonstrate the principle of the purification. Experiments with pI protein markers have been carried out in order to highlight the kinetics and the efficiency of the technique. Moreover, the resolution of the fractionation was shown to be 0.1 pH unit for the separation of beta-lactoglobulin A and B. In addition, the isoelectric fractionation of an Escherichia coli extract was performed in standard solubilization buffer to demonstrate the performances of the technique, notably for proteomics applications.

The extinction profiles as well as the hyper Rayleigh scattering signal of a highly monodisperse 22 nm diameter gold colloidal sol in the presence of pyridine have been measured. A strong enhancement of the HRS signal is observed in the presence of small amounts of pyridine. The relationship between the extinction spectra, the distribution of aggregated particles, and the second harmonic response has been investigated by evaluating the enhancement factor of the electromagnetic field in the colloids as they slowly aggregate. It is also shown that at larger pyridine concentrations, the hyper Rayleigh scattering signal levels off owing to the formation of large aggregates.