Decrease of Protein Vicinal Dithiols in Parkinsonism Disclosed by a Monoarsenical Fluorescent Probe.

Vicinal dithiol-containing proteins (VDPs) play an important role in maintaining the structures and functions of proteins mainly through the conversion between dithiols and disulfide bonds. The content of VDPs also reflects the redox status of an organism. To specifically and expediently detect VDPs, we developed a turn-on monoarsenical fluorescent probe (NEP) based on the intramolecular charge transfer mechanism. Naphthalimide was chosen as a fluorophore and linked with the receptor moiety (cyclic dithiarsolane) via carbamate segment. In the presence of VDPs, NEP displays a strong green fluorescence signal produced by the cyclic dithiarsolane cleavage and subsequent intramolecular cyclization to liberate the fluorophore. Furthermore, NEP exhibits high selectivity toward VDPs over other protein thiols and low molecular weight thiols. The favorable properties of NEP enable it readily to detect VDPs in live cells and in vivo. In addition, a remarkable decrease of VDPs in parkinsonism was disclosed for the first time, highlighting that regulating VDPs level has a therapeutic potential for parkinsonism.

Fluorophore-Dependent Cleavage of Disulfide Bond Leading to a Highly Selective Fluorescent Probe of Thioredoxin.

Finding specific small molecule probes of a biological target is extremely desired but remains a big challenge. We reported herein a highly selective fluorescent probe derivatized from the nile blue fluorophore, NBL-SS, for thioredoxin (Trx), a ubiquitous redox-regulating protein essentially involved in cell growth, differentiation, and death. NBL-SS displayed multiple favorable properties, such as red emission, fast response, and high fluorescence signal, which enabled the probe to readily image Trx functions in live cells and in vivo. The fluorophore-dependent selectivity indicates that manipulation of weak interactions between probes and their target biomacromolecules could further improve the probes' specificity. In addition, our discovery, i.e., the preference reduction of simple disulfide bonds by Trx over glutathione, also advances the development of disulfide cleavage-based probes, prodrugs, and theranostic agents.

An Azo Coupling Strategy for Protein 3-Nitrotyrosine Derivatization.

Herein, a strategy for the selective derivatization of 3-nitrotyrosine-containing proteins using the classic azo coupling reaction as the key step is described. This novel approach featured multiple advantages and was successfully applied to detect picomole levels of protein tyrosine nitration in biological samples.

Depletion of protein thiols and the accumulation of oxidized thioredoxin in Parkinsonism disclosed by a red-emitting and environment-sensitive probe.

Protein sulfhydryl groups play a vital role in maintaining cellular redox homeostasis and protein functions and have attracted increasing interests for the selective detection of protein thiols over low-molecular-weight thiols (LMWTs). Herein, we reported a red-emitting and environment-sensitive probe (FM-red) for detecting and labeling protein thiols. The probe contains a maleimide unit as a thiol receptor and an environment-sensitive fluorophore as a sensor. The emission signal of the probe was exclusively switched on by binding to protein sulfhydryl groups through the twisted intramolecular charge transfer mechanism, while negligible fluorescence was observed when FM-red reacted with LMWTs. Various experiments verified that FM-red possessed fast responsivity (∼10 min) and high selectivity to sense protein thiols over LMWTs with a red emission (∼655 nm). These favorable properties enable the probe to image protein sulfhydryl groups in live cells and in vivo. In addition, as FM-red has a relatively high molecular weight (MW 688), it is able to separate the labeled proteins from the unlabeled ones after FM-red derivatization via routine protein electrophoresis, which may be applied to determine the redox states of thioredoxin, a small redox protein ubiquitous in all cells. With the aid of the probe, we demonstrated a significant decrease in the protein thiols and the accumulation of oxidized thioredoxin in a cellular model of Parkinson's disease.