Jongcheol Seo

Can the structures of small to medium-sized proteins be conserved after transfer from the solution phase to the gas phase? A large number of studies have been devoted to this topic, however the answer has not been unambiguously determined to date. A clarification of this problem is important since it would allow very sensitive native mass spectrometry techniques to be used to address problems relevant to structural biology. A combination of ion-mobility mass spectrometry with infrared spectrosco

The amino acid serine has long been known to form a protonated "magic-number" cluster containing eight monomer units that shows an unusually high abundance in mass spectra and has a remarkable homochiral preference. Despite many experimental and theoretical studies, there is no consensus on a Ser₈H⁺ structure that is in agreement with all experimental observations. Here, we present the structure of Ser₈H⁺ determined by a combination of infrared spectro

The charge distribution in a molecule is crucial in determining its physical and chemical properties. Aminobenzoic acid derivatives are biologically active small molecules, which have two possible protonation sites: the amine (N-protonation) and the carbonyl oxygen (O-protonation). Here, we employ gas-phase infrared spectroscopy in combination with ion mobility-mass spectrometry and density functional theory calculations to unambiguously determine the preferred protonation sites of p-, m-, and o

Organic redox-active molecules are a promising platform for designing sustainable, cheap, and safe charge carriers for redox flow batteries. However, radical formation during the electron-transfer process causes severe side reactions and reduces cyclability. This problem is mitigated by using naphthalene diimide (NDI) molecules and regulating their π-π interactions. The long-range π-stacking of NDI molecules, which leads to precipitation, is disrupted by tethering four ammonium functionalities,

Amphiphilic porphyrins are of great interest in the field of supramolecular chemistry because they can be fabricated into highly ordered architectures that are stabilized by π-π stacking of porphine rings as well as by non-covalent interactions between their hydrophilic substituents. Protoporphyrin IX (PPIX) has two flexible propionic acid tails and is one of the most common amphiphilic porphyrins. However, unlike other PPIX analogues, PPIX does not form stable extended nanostructures, and the r

Entangled proteins have attracted significant research interest. Herein, we report the first rationally designed lasso proteins, or protein [1]rotaxanes, by using a p53dim-entwined dimer for intramolecular entanglement and a SpyTag-SpyCatcher reaction for side-chain ring closure. The lasso structures were confirmed by proteolytic digestion, mutation, NMR spectrometry, and controlled ligation. Their dynamic properties were probed by experiments such as end-capping, proteolytic digestion, and heat

Mass-balanced (1)H/(2)H isotope dipeptide tags (MBITs) are presented for simultaneous protein quantitation and identification. MBIT is derived from N-acetyl-Ala-Ala dipeptide and conjugated to primary amines of target peptides. (1)H/(2)H isotopes are encoded in the methyl groups of N-acetylated dipeptide: one tag deuterated on the N-acetyl group and another on the C-terminal alanine. MBIT-linked peptides comigrate in reversed-phase liquid chromatography without significant (1)H/(2)H isotope effe

C(aryl)-OMe bond functionalization catalyzed by cobalt(II) chloride in combination with a nacnac-type ligand and magnesium as a reductant is reported. Borylation and benzoylation of aryl methoxides are demonstrated, and C(aryl)-SMe bond borylation can be achieved under similar conditions. This is the first example of achieving these transformations using cobalt catalysis. Mechanistic studies suggest that a Grignard reagent is generated as an intermediate in a rare example of a magnesiation <i>vi

The kinetics of competing multiple-barrier unimolecular dissociations of o-, m-, and p-chlorotoluene radical cations to C7H7(+) (benzyl and tropylium) are studied by ab initio/Rice-Ramsperger-Kassel-Marcus (RRKM) calculations. This system presents a very intriguing kinetic example in which the conventional approach assuming a single-barrier or a double-well potential surface with one transition state cannot predict or explain the outcome. The molecular parameters obtained at the SCF level of the

DNA-encoded library (DEL) technology is a powerful tool for discovering potent ligands for biological targets but constrained by limitations, including the insolubility of DNA in organic solvents and its instability under various reaction conditions, which restrict the reactivity scope and structural diversity achievable in library synthesis. Here, we present a new strategy called nanoDEL, where library molecules and DNA tags are displayed on the surface of nanoparticles. Since nanoparticles dis

Abstract Entangled proteins have attracted significant research interest. Herein, we report the first rationally designed lasso proteins, or protein [1]rotaxanes, by using a p53dim‐entwined dimer for intramolecular entanglement and a SpyTag‐SpyCatcher reaction for side‐chain ring closure. The lasso structures were confirmed by proteolytic digestion, mutation, NMR spectrometry, and controlled ligation. Their dynamic properties were probed by experiments such as end‐capping, proteolytic digestion,