Cationization of neutral small molecules by site-specific carboxylation of 10-phenyl-10-phenothiazine in laser desorption/ionization.

It is a pre-requisite to ionize analyte molecules efficiently for detection by laser desorption/ionization mass spectrometry. Here, we report a conceptual demonstration of cationizing neutral small molecules which are typically difficult to be ionized with the traditional organic matrices due to their low proton/cation affinity values. Our strategy features generating radical cations from site-specifically carboxylated 10-(4-carboxyphenyl)-10-phenothiazine-3,7-dicarboxylic acid (PTZ(A)-Ph(A)) with a laser, and anchoring the chlorine ion from NaCl through covalent bond-like bridging interactions with the N/S atoms in the heterocyclic structure.

Carbon dots with positive surface charge from tartaric acid and m-aminophenol for selective killing of Gram-positive bacteria.

Gram-positive bacteria are one of the most common pathogens causing severe and acute infection, and hospital infection caused by Gram-positive bacteria have increased significantly. Also, as antibiotics have been widely used, abusing of antibiotics is becoming an increasingly serious problem which is followed by dangerous drug resistance. Here, we developed a series of cationic carbon dots (CDs) with high-performance as antibacterial agents by using tartaric acid and m-aminophenol as precursors.

Spatial-temporal profiling of antibiotic metabolites using graphite dots-assisted laser desorption ionization mass spectrometry.

Appropriate prescription of antibiotics requires the pharmacokinetic knowledge of the drugs and their metabolites in blood, and their distribution/retention in organ tissues. Here we report that highly crystalline graphite dots (GDs) allow for quantitative profiling of antibiotic metabolites in a spatial-temporal manner, in combination with matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI MSI). GDs matrix features an ultra-clean background base line and high efficiency in ionization of small molecules, thus enabling quantification of sulfamethoxazole (SMZ) and its metabolites with limit of detection (LOD) in the femtomole range.

Sensitive detection of clenbuterol by hybrid iridium/silicon nanowire-enhanced laser desorption/ionization mass spectrometry.

There is increasing demand for anti-doping drug monitoring in sports and food safety checks by developing sensitive and fast analytical methods. Here we report the development of hybrid Ir/SiNW as a new MALDI matrix for the detection of small molecules. This matrix is characterized by sufficient UV absorption, low-noise background, and high efficiency in ionization of small molecules.

Sensitive detection of caspase-3 enzymatic activities and inhibitor screening by mass spectrometry with dual maleimide labelling quantitation.

There is a great need to develop sensitive and specific methods for quantitative analysis of caspase-3 activities in cell apoptosis. Herein, we report a new method for sensitive detection of caspase-3 enzyme activities and inhibitor screening based on dual maleimide (DuMal) labeling quantitation and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Evaluation of caspase-3 activities is performed using MS analysis of the enzymatic product of the peptide probe, which fuses a caspase-3 cleavable peptide segment (DEVD) and a quantifiable "ID tag" (a peptide segment of FRGLRGFKC labeled by maleimide).