Amide-iminol tautomerism was studied for ionized oxamic acid (OA+•) in the gas phase using theDFT method with the UB3LYP functional and various basis sets {6-31++G(d,p), 6-311+G(d,p), and augcc-pVDZ}. Among twenty tautomers-rotamers possible for OA+•, eleven isomers were found to bethermodynamically stable. Similarly as for the neutral molecule, ionization (OA → OA+• + e) favors theamidization ...

amide-iminol tautomerism was studied for ionized oxamic acid (oa+•) in the gas phase using thedft method with the ub3lyp functional and various basis sets {6-31++g(d,p), 6-311+g(d,p), and augcc-pvdz}. among twenty tautomers-rotamers possible for oa+•, eleven isomers were found to bethermodynamically stable. similarly as for the neutral molecule, ionization (oa → oa+• + e) favors theamidization ...

A metal ion that attaches to a peptide backbone has the choice of binding to an amide carbonyl oxygen atom or to an amide nitrogen atom by replacement of the amide proton. Coordination to the nitrogen atom is normally accompanied by elimination of the proton, thereby resulting in deprotonation of the ligand. An alternative possibility, not involving deprotonation, is the unusual amide/iminol ta...

The CapD enzyme of Bacillus anthracis is a γ-glutamyl transpeptidase from the N-terminal nucleophile hydrolase superfamily that covalently anchors the poly-γ-D-glutamic acid (pDGA) capsule to the peptidoglycan. The capsule hinders phagocytosis of B. anthracis by host cells and is essential for virulence. The role CapD plays in capsule anchoring and remodeling makes the enzyme a promising target...

Aspartic acid (Asp) residues in peptides and proteins are prone to isomerization to the β-form and racemization via a five-membered succinimide intermediate. These nonenzymatic reactions have relevance to aging and age-related diseases. In this paper, we report a three water molecule-assisted, six-step mechanism for the formation of succinimide from Asp residues found by density functional theo...

The structure and intramolecular mobility of some derivatives bis(thio)phosphorylated amides in CCl4, CD2Cl2, CD3CN solutions were examined by 1H 31P NMR spectroscopy. A comparative analysis the temperature-dependent spectra studied compounds with symmetric asymmetric substitution at phosphorus atoms was carried out. Various processes identified – rotation around C-N bonds, conformational trans...

The ring-chain tautomerism of 2-(3-tosyl-1,2,3,4-tetrahydroquinazolin-2-yl)quinolin-8-ol (H(2)L(ring)) has been exploited to produce mononuclear complexes or, alternatively, dinuclear complexes, as desired, by varying the stoichiometry of the ligand. Cu(2+) and Zn(2+) stabilise the ring tautomeric form of the ligand in their mononuclear complexes M(HL(ring))(2). The structural characterisation ...

The observed variety of metal-ion complexation sites offered by peptides reflects a basic tension between charge solvation of the ion by Lewis-basic chelating groups versus amide nitrogen deprotonation and formation of metal-nitrogen bonds. Gas-phase models of metal-ion coordination can illuminate the factors governing this choice in condensed-phase proteins and enzymes. Here, structures of gas...