An excess electron binding to the ‘purple’ zwitterion quinonoid

The stabilization of arginine's zwitterion by dipole-binding of an excess electron.

The arginine parent anion was generated by a newly developed, infrared desorption-electron photoemission hybrid anion source. The photoelectron spectrum of the arginine anion was recorded and interpreted as being due to dipole binding of the excess electron. The results are consistent with calculations by Rak, Skurski, Simons, and Gutowski, who predicted the near degeneracy of arginine's canoni...

Quasidegeneracy of zwitterionic and canonical tautomers of arginine solvated by an excess electron.

The zwitterionic tautomers of isolated amino acids have not been identified in the gas-phase despite serious experimental efforts.1,2 The main reason is that a typical OH bond is stronger than a NH bond by ca. 17 kcal/mol,3 and thus the canonical tautomer is lower in energy. Indeed, numerous ab initio calculations have confirmed the energy preference for canonical tautomers H2N-CHR-COOH in the ...

On the stability of glycine-water clusters with excess electron: implications for photoelectron spectroscopy.

Calculations are presented for the glycine-(H(2)O)(n) (-) (n=0-2) anionic clusters with excess electron, with the glycine core in the canonical or zwitterion form. A variety of conformers are predicted, and their relative energy is examined to estimate thermodynamic stability. The dynamic (proton transfer) pathways between the anionic clusters with the canonical and the zwitterion glycine core ...

Pre-steady-state reaction of 5-aminolevulinate synthase. Evidence for a rate-determining product release.

5-Aminolevulinate synthase (ALAS) is the first enzyme of the heme biosynthetic pathway in non-plant eukaryotes and the alpha-subclass of purple bacteria. The pyridoxal 5'-phosphate cofactor at the active site undergoes changes in absorptive properties during substrate binding and catalysis that have allowed us to study the kinetics of these reactions spectroscopically. Rapid scanning stopped-fl...

Ruthenium Complexes with Non-Innocent Quinonoid, Quinoline- 5,8-dione and Iminoquinone Ligands: Synthesis, Structure, Redox Properties and Electron Distribution