Bacteriorhodopsin (BR) is a robust trans-membrane protein that functions as a light-driven proton pump, thus is an excellent candidate for biophotonics applications. For the development of new optical devices, the buildup of stable BR matrices has to be optimised. In this work, we present a multi-technique approach: the combination of optical waveguide lightmode spectroscopy (OWLS), atomic force microscopy (AFM) and multi-photon microscopy (MPM) aiming to analyze the optical and physico-chemical properties of BR embedded in polyelectrolyte multilayers (PEM) in its membrane bound form (purple membrane, PM), as well as solubilized BR immobilized within a photonic structure built of porous silicon (PSi). OWLS measurements revealed the possibility of incorporation of PM-BR layers into PE-multilayers. The calculated thickness and refractive index of the adsorbed layers demonstrate the successful adsorption of PM on top of the positively or negatively charged PE layers. Morphological studies by AFM proved a complete coverage of the positively charged PE layer with PM patches. As for the other model system, photonic responses of BR, after being immobilized within PSi substrates, have been evaluated using multi-photon microscopy. Fluorescence emission and second harmonic generation (SHG) of the BR-PSi system were observed at some particular pores of PSi and subsequent enhancement of the signal arising from the BR adsorbed within the pores was detected. Our results constitute the first steps of two interesting and innovative biomimetic approaches for the future design and development of BR based integrated optical devices.

OBJECTIVE: To test whether the presence of RA associated HLA-DRB1*0101, HLA-DRB1*0401 and HLA-DRB1*0404 alleles individually influences anti-cyclic citrullinated peptide antibodies (anti-CCP) production. METHODS: The frequency of anti-CCP antibodies was calculated in the sera of 260 RA patients expressing either two (double dose genotypes SE+/SE+), one (single dose genotypes SE+/SE-) or no RA associated HLA-DR alleles (SE-/SE-). Anti-CCP antibodies titers were also determined. RESULTS: RA associated HLA-DR alleles are not mandatory for production of anti-CCP. We found that 68% of SE-/SE- patients were anti-CCP positive. There was no significant difference in anti-CCP between SE negative patient (SE-/SE-) and patients expressing at least one SE (SE+/SE+ and SE+/SE-) (p=0.140). We observed no statistical difference in anti-CCP between RA patients expressing one or two SE (82% vs. 77%, p=0.577). Among SE+/SE-patients, HLA-DRB1*0404 was associated with anti-CCP with a statistically significant difference compared with SE negative patients (90% anti-CCP positive, p=0.02). HLA-DRB1*0404 was also associated with high titers of anti CCP with a statistically significant difference compared with HLA-DRB1*0401 and HLA-DRB1*0101 patients (p=0.025). CONCLUSIONS: The RA-associated HLA-DRB1*0404 allele was the most strongly associated with the presence of anti-CCP in RA sera. Moreover, HLA-DRB1*0404 patients had higher titers of anti CCP than patients with other RA associated HLA-DR alleles.

A diluted magnetic semiconductor (DMS) quantum well (QW) microcavity operating in the limit of the strong coupling regime is studied by magnetoptical experiments. The interest of DMS QW relies on the possibility to vary the excitonic, resonance over a wide range of energies by applying an external magnetic field, typically about 30 meV for 5 T in our sample. In particular, the anticrossing between the QW exciton and the cavity mode can be tuned by the external field. We observe the anticrossing and formation of exciton polaritons in magneto-reflectivity experiments. In contrast, magneto-luminescence exhibits purely excitonic character. Under resonant excitation conditions an additional emission line is observed at the energy of the dark exciton. The creation of dark excitons is made possible due to heavy hole-light hole mixing in the QW. The emission at this energy could be due to a combined spin flip of an electron and a bright exciton recombination. (c) 2007 Elsevier Ltd. All rights reserved.