Matrix-assisted laser desorption/ionization(MALDI)mass spectrometry(MS)plays an indispensable role in analyzing protein covalent structures.The reliable identification of amino acid residues and modifications relies o...Matrix-assisted laser desorption/ionization(MALDI)mass spectrometry(MS)plays an indispensable role in analyzing protein covalent structures.The reliable identification of amino acid residues and modifications relies on the mass accuracy,which is highly dependent on calibration.However,the accuracy provided by the currently available calibrants still needs further improvement in terms of compatibility with multiple tandem MS modes or ion polarity modes,calibratable range,and minimizing suppression of and interference with analyte signals.Here aiming at developing a versatile calibrant to solve these problem,we designed a synthetic peptide format of calibrant R_x(GDP_n)_m(referred to as“Gly-Asp-Pro,GDP”)according to the chemical natures of amino acids and polypeptide fragmentation rules in tandem MS.With four types of amino acid residues selected and arranged through rational designs,a GDP peptide produces highly regulated fragments that give rise to evenly spaced signals in each tandem MS mode and is compatible with both positive and negative ion modes.In internal calibration,its regulated fragmentation pattern minimizes interference with analyte signals,and using a single peptide as the input minimizes suppression of the analyte signals.As demonstrated by analyses of proteins including monoclonal antibody and Aβ-42,these features allowed significant increase of the mass accuracy and precision,which improved sequence coverage and sequence resolution in sequence analyses(including de novo sequencing).This rational design strategy may also inspire further development of synthetic calibrants that benefit structural analysis of biomolecules.展开更多
Photoredox-catalyzed aminoarylation and thioami-nation of unactivated alkenes have been developed,providing novel synthetic routes to access synthe-tically challenging quaternary carbon-centered benzoindolizidinones a...Photoredox-catalyzed aminoarylation and thioami-nation of unactivated alkenes have been developed,providing novel synthetic routes to access synthe-tically challenging quaternary carbon-centered benzoindolizidinones and trifluoromethylthiolated piperidines using readily available starting materials.Notably,these transformations were enabled by merging amidyl radical generation from N-alkyl benzamides with oxidant incorporation.Density functional theory calculations were performed to understand the reaction mechanism and to rationa-lize the regioselectivities.Moreover,the newly deve-loped catalytic aminoarylation provided a convenient synthetic route for natural product tylophorine and its gem-dimethyl analogues with greatly improved drug-like properties such as enhanced solubility and stability.展开更多
基金supported by grants from the National Natural Science Foundation of China(No.21974069)Open Fund Programs of Shenzhen Bay Laboratory(No.SZBL2020090501001)。
文摘Matrix-assisted laser desorption/ionization(MALDI)mass spectrometry(MS)plays an indispensable role in analyzing protein covalent structures.The reliable identification of amino acid residues and modifications relies on the mass accuracy,which is highly dependent on calibration.However,the accuracy provided by the currently available calibrants still needs further improvement in terms of compatibility with multiple tandem MS modes or ion polarity modes,calibratable range,and minimizing suppression of and interference with analyte signals.Here aiming at developing a versatile calibrant to solve these problem,we designed a synthetic peptide format of calibrant R_x(GDP_n)_m(referred to as“Gly-Asp-Pro,GDP”)according to the chemical natures of amino acids and polypeptide fragmentation rules in tandem MS.With four types of amino acid residues selected and arranged through rational designs,a GDP peptide produces highly regulated fragments that give rise to evenly spaced signals in each tandem MS mode and is compatible with both positive and negative ion modes.In internal calibration,its regulated fragmentation pattern minimizes interference with analyte signals,and using a single peptide as the input minimizes suppression of the analyte signals.As demonstrated by analyses of proteins including monoclonal antibody and Aβ-42,these features allowed significant increase of the mass accuracy and precision,which improved sequence coverage and sequence resolution in sequence analyses(including de novo sequencing).This rational design strategy may also inspire further development of synthetic calibrants that benefit structural analysis of biomolecules.
基金This study was funded by the National“973”grant from the Ministry of Science and Technology(grant no.2011CB965300)National Natural Science Foundation of China(grant nos.21232001 and 21302106)+1 种基金National Science and Technology Major Project(grant no.2018ZX09711001)Tsinghua University Initiative Scientific Research Program.
文摘Photoredox-catalyzed aminoarylation and thioami-nation of unactivated alkenes have been developed,providing novel synthetic routes to access synthe-tically challenging quaternary carbon-centered benzoindolizidinones and trifluoromethylthiolated piperidines using readily available starting materials.Notably,these transformations were enabled by merging amidyl radical generation from N-alkyl benzamides with oxidant incorporation.Density functional theory calculations were performed to understand the reaction mechanism and to rationa-lize the regioselectivities.Moreover,the newly deve-loped catalytic aminoarylation provided a convenient synthetic route for natural product tylophorine and its gem-dimethyl analogues with greatly improved drug-like properties such as enhanced solubility and stability.
