We introduce a general design to construct fluorescence-switching probes. Upon the interaction of the ligand with the protein, the crowded surroundings restrict the bond rotation of the fluorescent molecular rotor to trigger a strong fluorescence signal, which is reduced upon the addition of a competitive ligand or after protein degradation.

Quantitative detection of trace amounts of a biomarker in protein rich human blood plasma using fluorescent probes is a great challenge as the real signal is usually obscured by nonspecific fluorescence. This problem occurs because most of the fluorescent dyes bind very tightly with blood proteins to produce a large fluorescence increase, resulting in overestimation of the biomarker concentrations and false positive diagnosis. In this paper, we report that biotinylated fluorescent probes encapsulated in avidin protein can generate very specific fluorescence in blood serum by blocking out nonspecific dye-protein interactions. We applied our novel probe design to detect two different types of biomolecules, hydrogen sulfide and nitroreductase. Our Avidin conjugated probes achieved quantitative analyte detection in blood serum; whereas concentrations were overestimated up to 320-fold when bare fluorescent probes were employed. As compared to conventional approaches where fluorescent probes are encapsulated into polymers and nanoparticles, our simple approach successfully overcomes many key issues such as dye leakage, long preparation steps, inconsistent dye-host ratios, difficulty in constructing in situ in a complex medium, and limited application to detect only small metabolites.

Despite the promising improvements made recently on fluorescence probes for the detection of enzymes and reactive small molecules, two fundamental problems remain: weaker fluorescence of many dyes in aqueous buffers and strong nonspecific signals in samples containing high protein levels. In this paper, we introduce a novel fluorescent probe encapsulated in protein cavity (FPEPC) concept as demonstrated by SNAP-tag protein and three environment-sensitive fluorescence probes to overcome these two problems. The probes were constructed by following the current probe design for enzymes and reactive small molecules but with an additional benzylguanine moiety for selective SNAP-tag conjugation. The SNAP-tag conjugated probes achieved quantitative nitroreductase and hydrogen sulfide detection in blood plasma, whereas analyte concentrations were overestimated up to 700-fold when bare fluorescent probes were employed for detection. Furthermore, detection sensitivity was increased dramatically, as our probes displayed 390-fold fluorescence enhancement upon SNAP-tag conjugation, in stark contrast to the weak fluorescence of the free probes in aqueous solutions. Compared with the conventional approaches where fluorescent probes are encapsulated into polymers and nanoparticles, our simple and general approach successfully overcame many key issues such as dye leakage, long preparation steps, inconsistent dye-host ratios, difficulty in constructing in situ in a complex medium, and limited application to detect only small metabolites.

The shallow Nice submarine slope is notorious for the 1979 tsunamigenic landslide that caused eight casualties and severe infrastructural damage. Many previous studies have tackled the question whether earthquake shaking would lead to slope failure and a repetition of the deadly scenario in the region. The answers are controversial. In this study, we assess for the first time the factor of safety using peak ground accelerations (PGAs) from synthetic accelerograms from a simulated offshore Mw 6.3 earthquake at a distance of 25km from the slope. Based on cone penetration tests (CPTu) and multichannel seismic reflection data, a coarser grained sediment layer was identified. In an innovative geotechnical approach based on uniform cyclic and arbitrary triaxial loading tests, we show that the sandy silt on the Nice submarine slope will fail under certain ground motion conditions. The uniform cyclic triaxial tests indicate that liquefaction failure is likely to occur in Nice slope sediments in the case of a Mw 6.3 earthquake 25km away. A potential future submarine landslide could have a slide volume (7.7 × 10 6 m 3 ) similar to the 1979 event.Arbitrary loading tests reveal post-loading pore water pressure rise, which might explain post-earthquake slope failures observed in the field. This study shows that some of the earlier studies offshore Nice may have overestimated the slope stability because they underestimated potential PGAs on the shallow marine slope deposits.