S-Denitrosylase-Like Activity of Cyclic Diselenides Conjugated with Xaa-His Dipeptide: Role of Proline Spacer as a Key Activity Booster

This study developed dipeptide-conjugated 1,2-diselenan-4-amine ( 1 ), i. e., 1 -Xaa-His, as a new class of S-denitrosylase mimic. The synthesized compounds, especially 1 -Pro-His, remarkably promoted S-denitrosylation of nitrosothiols (RSNO) via a catalytic cycle involving the reversible redox reaction between the diselenide and its corresponding diselenol ([SeH,SeH]) form with coexisting reductant thiols (R′SH), during which the [SeH,SeH] form as a key reactive species reduces RSNO to the corresponding thiol (RSH). Structural analyses of 1 -Pro-His suggested that the peptide backbone of [SeH,SeH] is rigidly bent to form a γ-turn, possibly including an NH⋅⋅⋅Se hydrogen bond between the imidazole ring of His and selenol group, thus stabilizing the [SeH,SeH] form thermodynamically, and dramatically enhancing the catalytic activity. Furthermore, the synthetic compounds were found to prohibit S-nitrosylation-induced protein misfolding in the presence of RSNO, eventually implying their potential as a drug seed for misfolding diseases caused by the dysregulation of the S-denitrosylation system.     

Multi-agent consensus with stopping rules under bounded measurement noise

A multi-agent consensus protocol is investigated over noisy undirected connected graphs. It is supposed that each agent can know her neighbors' states with bounded noise. A theoretical stopping rule having a probabilistic guarantee is established for the consensus protocol, which explicitly relates the number of iterations with the closeness of the agreement. The stopping rule is derived by utilizing Bernstein inequality that deals with a given noise bound explicitly. The sample complexity with respect to the number of agents is also investigated, where it is shown that the number of iterations required by the proposed stopping rule based on the bound of noise itself is generally smaller than that of the conventional stopping rules that utilize bound of noise variance. The results are demonstrated through numerical examples.     

Fluorophore-Decorated Mie Resonant Silicon Nanosphere for Scattering/Fluorescence Dual-Mode Imaging

Inorganic nanoparticles with multiple functions have been attracting attention as multimodal nanoprobes in bioimaging, biomolecule detection, and medical diagnosis and treatment. A drawback of conventional metallic nanoparticle-based nanoprobes is the Ohmic losses that lead to fluorescence quenching of attached molecules and local heating under light irradiation. Here, metal-free nanoprobes capable of scattering/fluorescence dual-mode imaging are developed. The nanoprobes are composed of a silicon nanosphere core having efficient Mie scattering in the visible to near infrared range and a fluorophore doped silica shell. The dark-field scattering and photoluminescence images/spectra for nanoprobes made from different size silicon nanospheres and different kinds of fluorophores are studied by single particle spectroscopy. The fluorescence spectra are strongly modified by the Mie modes of a silicon nanosphere core. By comparing scattering and fluorescence spectra and calculated Purcell factors, the fluorescence enhancement factor is quantitatively discussed. In vitro scattering/fluorescence imaging studies on human cancer cells demonstrate that the developed nanoparticles work as scattering/fluorescence dual-mode imaging nanoprobes.