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The time-series state and parameter estimations of indoor localization continue to be a topic of growing importance. To deal with the nonlinear and positive skewed non-Gaussian dynamic of indoor CSS&ndash, TOF (Chirp-Spread-Spectrum Time-of-Flight) ranging measurements and position estimations, Monte Carlo Bayesian smoothers are promising as involving the past, present, and future observations. However, the main problems are how to derive trackable smoothing recursions and to avoid the degeneracy of particle-based smoothed distributions. To incorporate the backward smoothing density propagation with the forward probability recursion efficiently, we propose a lightweight Marginalized Particle Smoother (MPS) for nonlinear and non-Gaussian errors mitigation. The performance of the position prediction, filtering, and smoothing are investigated in real-world experiments carried out with vehicle on-board sensors. Results demonstrate the proposed smoother enables a great tool by reducing temporal and spatial errors of mobile trajectories, with the cost of a few sequence delay and a small number of particles. Therefore, MPS outperforms the filtering and smoothing methods under weak assumptions, low computation, and memory requirements. In the view that the sampled trajectories stay numerically stable, the MPS form is validated to be applicable for time-series position tracking.

Ligands of G-quadruplex have received great attention because of their potential anticancer activity. Here, we designed a label-free electrochemical method to identify electrochemically active molecules that stabilize G-quadruplexes in homogeneous medium. Daunorubicin (DNR) was used as model drug. In the presence of GDNA, the voltammetry of DNR changed. The binding constant (β) and binding-site number (m) of GDNA–mDNR are simultaneously obtained from dependence of the current on the amount of added GDNA in voltammetry, concluding that β=(2.37±2.25)×107 M−1and m was near 1, respectively. Control experiment was performed, indicating that this method can specific identify G-quadruplex-binding ligand. The interaction mechanism of DNR with GDNA was also investigated by circular dichroism (CD). The result demonstrated that it is a simple and selective method for identification electroactive ligand with potential anticancer activity. Keywords: G-quadruplex, Ligand, Label-free, Electroactive

The G-rich overhang of human telomere tends to form a G-quadruplex structure, and G-quadruplex formation can effectively inhibit telomerase activity in most cancer cells. Therefore, it is important to identify the formation and properties of the G-quadruplex, with the particular aim of selecting G-quadruplex-binding ligands that could potentially lead to the development of anticancer therapeutic agents. With this goal in mind, we report a fluorescence resonance energy transfer (FRET) assay system for the identification of G-quadruplex ligands using DNA-functionalized gold nanoparticles (DNA-GNPs) as the fluorescence quencher and a carboxyfluorescein (FAM)-tagged human telomeric sequence (F-GDNA) as the recognition probe. A thiolated complementary strand of human telomeric DNA (cDNA), which first adheres to the surface of the GNPs and then hybridizes with F-GDNA, results in the fluorescence quenching of F-GDNA by the GNPs. However, fluorescence is restored when single-stranded F-GDNA folds into a G-quadruplex structure upon the binding of quadruplex ligands, leading to the release of F-GDNA from the surface of the GNPs. Combined data from fluorescence measurements and CD spectroscopy indicated that ligands selected by this FRET method could induce GDNA to form a G-quadruplex. Therefore, this FRET G-quadruplex assay is a simple and effective approach to identify quadruplex-binding ligands, and, as such, it promises to provide a solid foundation for the development of novel anticancer therapeutic agents.

Ligands that bind and stabilize G-quadruplex DNA structures are of significant interest because of their potential to inhibit telomerase and halt tumor cell proliferation. An electrochemical method was proposed to select natural G-quadruplex-binding ligands using ferrocene as the electrochemical indicator.