No abstract

The excited-state proton transfer in LB films of 2-naphthol-6-sulfonamide of dodecylamine (NSDA) has been studied by spectrofluorimetric methods. A modification of the composition of the atmosphere surrounding the samples enables an identification of emission peaks of the reactants, namely, an excited protonated (ROH*) form and a dissociated (RO-*) form taking part in the excited-state deprotonation (ESDP). The mechanism of proton transfer and the nature of the proton acceptor were assessed from the study of separated emission spectra, taken at various experimental conditions and for various film layouts. The estimated rate of proton transfer was between 5 × 108 and 5 × 109 s-1. The results concerning ESDP in LB films suggest that water molecules, probably forming chains of hydrogen bonds (“proton wires”), and carboxyl groups forming a type of hydrogen bonds with a proton donor could be the main proton acceptors.

Abstract. In this paper we report the biological synthesis of gold nanoparticles (GNPs) by the reduction of gold ions using a suspension and supernatant of P. aeruginosa. The biosynthesis method was straightforward and yielded good results without using toxic chemicals. The size distribution of the gold nanoparticles synthesized by P. aeruginosa at higher temperatures was larger than that synthesized at lower temperatures. The GNPs morphology was isotropic at various temperatures. With an increase in the temperature, the stability of the GNPs decreased. The absorption and fluorescence spectra accorded well with the size distribution of the particles, with the nanoparticle size increasing as the absorption and fluorescence increased too. The optical properties of the GNPs observed in the study accorded well with the scanning electron microscopy (SEM) observations. The visible photoluminescence (PL) around 435 nm indicated the possible use of the obtained colloids, which consisted of GNPs and capping biomaterial, in therapeutic applications. Moreover, the synthesized GNPs showed good antibacterial activity toward E. coli indicating their potential in biological applications.

No abstract

Distribution of the isoelectric point (pI) was calculated for the hypervariable regions of Fab fragments of the antibody molecules, which structure is annotated in the structural antibody database SabDab. The distribution is consistent with the universal for all organisms dividing the proteome into two sets of acidic and basic proteins. It shows the additional fine structure in a form of the narrow-sized peaks of pI values. This is an explanation why a small change of the environmental pH can have a strong effect on the antibody-antigen affinity. To show this, a typical enzyme-linked immunospecific assay experiment for testing the reaction of goat anti-human IgA antibodies with human IgA immunoglobulins of saliva as antigens was modified in such a way that Fe3O4magnetic nanoparticles were added to PBS buffer. The magnetic nanoparticles were remotely heated by the radio frequency magnetic field providing the local change of temperature and pH. It was observed that short times of the heating were significantly increasing the antibody-antigen binding strength while it was not the case for a longer time. The finding discussed in the study can be useful for biopharmaceuticals using antibodies, the immunoassay techniques as well as for control over the use of hyperthermia.