Decarboxylation is a significant reaction pathway for photolabile calcium chelators and related compounds.
Photolysis of amino acids that bear a 2-nitrobenzyl protecting group on the amino nitrogen involves a normal 2-nitrobenzyl-type photocleavage to release the amino acid but also a second mechanistic pathway, that appears to be initiated by single electron transfer from the amino group to the excited state of the nitroaromatic. The end result of this pathway is photodecarboxylation. Quantitative experiments suggest that this latter pathway can contribute between 10 and 80% of the total reaction flux in different compounds. It appears that the aminium radical, the first product of the single electron transfer, can be intercepted by certain amino acids, resulting in a transfer of decarboxylation to this "sacrificial" amino acid. Possible implications for precise details of calcium release from photolabile derivatives of EDTA and EGTA are discussed.
Barth
Andreas
A
Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91, Stockholm, Sweden.
Martin
Stephen R
SR
Corrie
John E T
JE
D002118:Calcium / Q000737:chemistry* / Q000528:radiation effects*; D002614:Chelating Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000528:radiation effects*; D003653:Decarboxylation; D004579:Electron Transport; D005609:Free Radicals / Q000138:chemical synthesis / Q000737:chemistry / Q000528:radiation effects; D015394:Molecular Structure; D010777:Photochemistry; D010782:Photolysis; D012680:Sensitivity and Specificity; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D014466:Ultraviolet Rays
D002614:Chelating Agents; D005609:Free Radicals; D002118:Calcium