Several mutations in the gene encoding the microtubule-associated protein tau are responsible for the formation of neurofibrillary inclusions in frontotemporal dementia with Parkinsonism linked to chromosome 17 (FTDP-17). Here we present the high-resolution characterization of the conformational properties of two FTDP-17 mutants of the four-repeat domain of tau, P301L and DeltaK280, and their properties for binding to polyanions and microtubules. Multidimensional NMR spectroscopy shows that the mutations do no lead to a significant increase in the level of beta-structure in their monomeric state, even though the mutations strongly promote beta-structure during aggregation. However, local structural changes are induced in the second repeat. These changes only weakly affect the binding to the polyanion heparin, which promotes paired helical filament formation. The extent of binding to microtubules, however, is strongly decreased. Our results demonstrate that the reversible binding of tau to microtubules involves specific interactions, which are not essential for binding to polyanions.

The phenomenon of fluorescence in immunosensors is described in this paper. Both structure and characteristics of biosensors and immunosensors are presented. Types of immunosensors and the response of bioreceptor layers to the reaction with analytes as well as measurements of electrochemical, piezoelectric and optical parameters in immunosensors are also presented. In addition, detection techniques used in studies of optical immunosensors based on light-matter interactions (absorbance, reflectance, dispersion, emission) such as: UV/VIS spectroscopy, reflectometric interference spectroscopy (RIfs), surface plasmon resonance (SPR), optical waveguide light-mode spectroscopy (OWLS), fluorescence spectroscopy. The phenomenon of fluorescence in immunosensors and standard configurations of immunoreactions between an antigen and an antibody (direct, competitive, sandwich, displacement) is described. Fluorescence parameters taken into account in analyses and fluorescence detection techniques used in research of immunosensors are presented. Examples of immunosensor applications are given.

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The last two decades has seen a significant increase in interest in biosensors. According to the Web of Science database, the number of scientific publications over the past 20 years increased from 309 in 1993 up to 3,467 in 2013 (Fig. 1).The demand for developing new detection methods, increasing interest in visualization techniques [1][2][3], emphasis placed on new drug discovery programs [4], diagnostic test development [5][6][7], and attempts to explain cellular action mechanisms and to trace a cell's metabolism pathway [7,8], and the possibility of using biosensors in numerous fields of application, (for example: medicine [9-11], environmental protection [12-14, 16-17], food industry [18], and defense industry [19]) has results in an increasing number of research projects targeted at biosensor design and fabrication. Biosensors used in environmental monitoring measure the toxicity effect based on the detection of a chemical compound or compound group by selective recognition of a biomolecule in the receptor layer and then by detection of a signal after passing through the transducer layer [16].The application of fluorescence biosensors in environmental protection applications [20][21][22][23][24][25], medical diagnostics [26][27][28][29][30][31][32][33][34][35], and industries [36][37][38][39][40][41][42][43][44][45] also is growing.Pol. J. Environ. Stud. Vol. 24, No. 1 (2015) AbstractEnzyme-based fluorescence biosensors and their applications in environmental protection, medicine, and industry are described. Biosensors used in environmental protection measure toxicity effects. A chemical compound or group of compounds is detected by the recognition of molecules in the receptor layer and then by detecting a signal passing through the transducer layer. Biosensors are classified according to the transduction method. Special emphasis is placed on optical biosensors, especially fluorescent biosensors, and such measurement techniques as FRET (Fröster resonance energy transfer), FLIM (fluorescence lifetime imaging), FCS (fluorescence correlation spectroscopy), and changes in fluorescence intensity. The phenomenon of fluorescence in biosensors and the selection of appropriate methods are described. The use of enzymes in the receptor layer and enzyme classification according to its category and functions used for analyte detection are presented. The fluorescence properties of enzymes resulting from possessing such cofactors as flavin or heme (prosthetic) groups are discussed. Several methods for enzyme immobilization, namely entrapment, adsorption, covalent immobilization, cross linking, and affinity interaction are described, and the use of enzymatic fluorescence biosensors in the detection of analytes is presented.