The waveguide type biosensors for noninvasive glucose detection based on LSPR of silver nanoparticles were fabricated
by thermal diffusion in UV-irradiated photo-thermo-refractive (PTR) glasses and by ion-exchange method in sodiumborosilicate
glasses in water vapor atmosphere. The optical and structural properties of the obtained nanocomposites
were investigated. The D-glucose/D-galactose binding protein (GGBP) was chosen as a sensitive element of biosensor
and successable immobilized on top of PTR glass. The change in absorption spectra were judged due to the presence of
GGBP on the substrate surface.
Glucose sensing and odorant molecules sensing are used as a models to explore the advantages and problems deriving
from the use of either enzymes or odorant-binding proteins to develop stable optical biosensors. We report on a novel
approach to address the problem of substrate consumption by sensors based on enzymes, namely the utilization of apoenzymes
as non-active forms of the protein which are still able to bind the substrate/ligand. We also show studies in
which the isolation of an odorant-binding protein from the nose of the dog is used as non-consuming analyte probe for
the realization of an integrated optical sensor.
Thioflavin T (ThT) is known to have a very low quantum yield in water solutions itself and in the presence of native and
denatured proteins and their amorphous aggregates, but to form a highly fluorescent complex with amyloid and amyloid-like
fibrils. A new view on ThT spectral characteristics and mechanism of interaction with amyloid fibrils was elaborated
on the basis of experimental studies of solvent polarity and viscosity influence on ThT absorption, excitation and
fluorescence spectra and results of quantum-chemical calculations. It was shown that presence of the methyl group at
nitrogen atom in benzthiazole ring makes nonplanar conformation of ThT energetically profitable and decreases barrier
of intramolecular rotation of benzthiazole and aminobenzole rings relative to each other. Due to this ThT represents a
dynamic set of molecules with differently perturbed systems of π-conjugated bonds. Possibility of torsional oscillations
of ThT fragments relative to each other coupled with intramolecular charge transfer in the excited state permits to refer
ThT to the class of molecular rotors. The significant, by three orders, increase of quantum yield of ThT when incorporated in amyloid and amyloid-like fibrils is caused by restriction of torsional oscillations of ThT fragments relative to each other.
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