TY - JOUR
T1 - Reduction of Guanosyl Radicals in Reactions with Proteins Studied by TR-CIDNP
AU - Morozova, O.B.
AU - Kaptein, R.
AU - Sagdeev, R.Z.
AU - Yurkovskaya, A.V.
PY - 2013
Y1 - 2013
N2 - Pulsed-field-gradient nuclear magnetic resonance (NMR) combined with
time-resolved chemically induced dynamic nuclear polarization (TR-CIDNP) was
applied to study the reduction of guanosyl radicals in reactions with the proteins hen egg
white lysozyme (HEWL) and bovine a-lactalbumin (BLA) in their native state.Guanosyl
radicalswere generated photochemically in the reaction of guanosine-50-monophosphate
with photosensitizer, triplet-excited 2,20-dipyridyl. In this reaction, at pH 5 guanosyl
cation radical is formed, which deprotonates to yield the neutral guanosyl radical. To
minimize the contribution of the cation radical, phosphate buffer was added, which
accelerates the deprotonation of guanosyl cation radical. From model simulations of
CIDNP kinetics the rate constants of the reduction were found to be (3.1 ±
0.5) 9 107 M-1s-1 for HEWL and (1.6 ± 0.4) 9 107 M-1s-1 for BLA. Also, experiments
were carried out at the conditions for denatured HEWL, i.e., at 50 C in the
presence of 10 M urea-d4. The rate constant of the reduction of guanosyl radical in this
case was (3.6 ± 0.5) 9 108 M-1s-1.
AB - Pulsed-field-gradient nuclear magnetic resonance (NMR) combined with
time-resolved chemically induced dynamic nuclear polarization (TR-CIDNP) was
applied to study the reduction of guanosyl radicals in reactions with the proteins hen egg
white lysozyme (HEWL) and bovine a-lactalbumin (BLA) in their native state.Guanosyl
radicalswere generated photochemically in the reaction of guanosine-50-monophosphate
with photosensitizer, triplet-excited 2,20-dipyridyl. In this reaction, at pH 5 guanosyl
cation radical is formed, which deprotonates to yield the neutral guanosyl radical. To
minimize the contribution of the cation radical, phosphate buffer was added, which
accelerates the deprotonation of guanosyl cation radical. From model simulations of
CIDNP kinetics the rate constants of the reduction were found to be (3.1 ±
0.5) 9 107 M-1s-1 for HEWL and (1.6 ± 0.4) 9 107 M-1s-1 for BLA. Also, experiments
were carried out at the conditions for denatured HEWL, i.e., at 50 C in the
presence of 10 M urea-d4. The rate constant of the reduction of guanosyl radical in this
case was (3.6 ± 0.5) 9 108 M-1s-1.
U2 - 10.1007/s00723-012-0403-0
DO - 10.1007/s00723-012-0403-0
M3 - Article
SN - 0937-9347
VL - 44
SP - 233
EP - 245
JO - Applied Magnetic Resonance
JF - Applied Magnetic Resonance
ER -