Label-free quantification of cystatin C as an improved marker for renal failure.

A label-free biosensor has been developed, allowing quantification of cystatin C in human serum. This was achieved by using reflectometric interference spectroscopy as detection method. Cystatin C is a small serum protein that allows detection of renal failure more reliably than established parameters as creatinine. The protein was immobilized on the surface of a glass transducer, forming the sensitive layer of the sensor chip. Based on a binding-inhibition assay, two different types of monoclonal cystatin C antibodies were compared, by their behavior and their obtained working range in buffer and serum as matrix. Both antibodies allowed quantification of the protein in serum as matrix within the required clinical ranges of 0.53-1.02 mg/L. Detected recovery rates are in a range between 84.8% and 116.1%. The developed sensor shows high inner chip reproducibility and low cross-sensitivity.

CCD camera image analysis for mapping solute concentrations in saturated porous media.

This paper presents an optical approach, based on the use of a low-cost charge-coupled device (CCD) camera, for the quantitative determination of solute concentrations in saturated porous media. The method is applied to evaluate tracer experiments carried out in a laboratory model tank. The CCD photos deliver RGB values which are transferred into concentrations for the evaluation of vertical concentration profiles over the whole tank area. A specially developed evaluation procedure, including internal referencing for noise reduction, considers the colour of the adjacencies of the evaluated spots and scattering effects. The CCD data evaluation technique is accompanied by conventional sampling and absorption measurements and by numerical flow and transport simulations. This non-invasive technique allows a direct mapping of the concentration distribution without any disturbance of the solute plume. Therefore, it turns out to be an important tool for a detailed investigation of fundamental processes (e.g. transverse dispersion) determining the solute (e.g. contaminant) transport in porous media.

Solid-state optical properties of linear polyconjugated molecules: pi-stack contra herringbone.

The intermolecular arrangement in the solid state and the consequences on the optical and photophysical properties are studied on different derivatives of oligophenylenevinylenes by UV/VIS absorption and angular-resolved polarized fluorescence spectroscopy. Unsubstituted distyrylbenzene (DSB) organizes in a herringbone manner, with the long axes of the molecules oriented in parallel, but the short axes almost perpendicular to each other. Fluorinated distyrylbenzene (F(12)DSB) as well as the DSB:F(12)DSB cocrystals prefer cofacial pi-stacking in the solid state. For all structures, the consequence of the parallel alignment of the transition moments is a strongly blueshifted H-type absorption spectrum and a low radiative rate constant k(F). Significant differences are observed for the emission spectra: the perpendicular arrangement of the short axes in DSB crystals leads to only very weak intermolecular vibronic coupling. Hence the emission spectrum is well structured, very similar to the one in solution. For F(12)DSB and DSB:F(12)DSB, the cofacial arrangement of the adjacent molecules enables strong intermolecular vibronic coupling of adjacent molecules. Thus, an unstructured and strongly redshifted excimerlike emission spectrum is observed. The differences in the electronic nature of the excited states are highlighted by quantum-chemical calculations, revealing the contribution of interchain excitations to the electronic transitions.