The carbonate radical: its reactivity with oxygen, ammonia, amino acids, and melanins.
The carbonate radical (CO 3 (*-)) is of importance in biology and chemistry. We used pulse radiolysis to generate the CO 3 (*-) radical and show there is no reaction with oxygen. However, in the presence of ammonia the CO 3 (*-) radical is removed by NO (*), which itself arises from the scavenging of NH 2 (*) by oxygen, and the mechanism of this process is reported. The CO 3 (*-) radical shows complex decay patterns in the presence of ammonia, which can be understood as a balance between the radical-radical reaction CO 3 (*-) + CO 3 (*-) and CO 3 (*-) + NH 2 (*) (the amino radical). Also, we report reactivity with glycine and alanine and with melanin models. The CO 3 (*-) reacts with both dopa-melanin (DM, a model of black eumelanin) and with cysteinyl-dopa-melanin (CDM, a model of red/blond phaeomelanin). However, the reaction rate constant is much higher with CDM than with DM.
Clarke
K
K
Chemistry Section, School of Physical and Geographical Sciences, Keele University, Staffs ST5 5BG, UK.
Edge
R
R
Johnson
V
V
Land
E J
EJ
Navaratnam
S
S
Truscott
T G
TG
D000596:Amino Acids / Q000737:chemistry*; D000641:Ammonia / Q000737:chemistry*; D002254:Carbonates / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D007700:Kinetics; D008543:Melanins / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D013997:Time Factors
D000596:Amino Acids; D002254:Carbonates; D005609:Free Radicals; D008543:Melanins; D000641:Ammonia; D010100:Oxygen