TY - JOUR
T1 - Regeneration of β-carotene from the radical cation by tyrosine and tryptophan
AU - Cheng, Hong
AU - Han, Rui-Min
AU - Lyu, Ming-Kuan
AU - Zhang, Jian-Ping
AU - Skibsted, Leif Horsfelt
PY - 2015/6/4
Y1 - 2015/6/4
N2 - The phenolic amino acid tyrosine (Tyr) was found more efficient in regenerating β-carotene (β-Car) from the radical cation (β-Car•+) than tryptophan (Trp) in the presence of base for conditions where the reduction potentials for Trp and Tyr are comparable. Electron transfer from Tyr in 4:1 chloroform/methanol to β-Car•+ in the presence of excess base, (CH3)4N+OH-, had a rate close to diffusion control and a second-order rate constant in agreement with the Marcus theory for electron transfer when compared to plant phenols. A maximum of 40% β-Car was regenerated for ten times excess of Tyr as studied by 532 nm laser flash photolysis followed by transient absorption spectroscopy in the visible and near-infrared regions. The nonregenerated fraction of β-Car is assigned to secondary degradation processes. For Trp, the rate constant for regeneration of β-Car•+ was 1 order of magnitude smaller compared to Tyr and slower than expected from Marcus theory by comparison with plant phenols.
AB - The phenolic amino acid tyrosine (Tyr) was found more efficient in regenerating β-carotene (β-Car) from the radical cation (β-Car•+) than tryptophan (Trp) in the presence of base for conditions where the reduction potentials for Trp and Tyr are comparable. Electron transfer from Tyr in 4:1 chloroform/methanol to β-Car•+ in the presence of excess base, (CH3)4N+OH-, had a rate close to diffusion control and a second-order rate constant in agreement with the Marcus theory for electron transfer when compared to plant phenols. A maximum of 40% β-Car was regenerated for ten times excess of Tyr as studied by 532 nm laser flash photolysis followed by transient absorption spectroscopy in the visible and near-infrared regions. The nonregenerated fraction of β-Car is assigned to secondary degradation processes. For Trp, the rate constant for regeneration of β-Car•+ was 1 order of magnitude smaller compared to Tyr and slower than expected from Marcus theory by comparison with plant phenols.
U2 - 10.1021/acs.jpcb.5b02657
DO - 10.1021/acs.jpcb.5b02657
M3 - Journal article
C2 - 25959586
SN - 1520-6106
VL - 119
SP - 6603
EP - 6610
JO - Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical
JF - Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical
IS - 22
ER -