ライフサイエンスコーパス: semiquinone

1 nzyme has been demonstrated to stabilize the semiquinone.

2 duced, by a single electron transfer, to its semiquinone.

3 reduction of flavodoxin by NADH to the blue semiquinone.

4 ing site for ubiquinol that stabilizes a ubi-semiquinone.

5 none-7 and that the enzyme stabilizes a mena-semiquinone.

6 interaction and the formation of the anionic semiquinone.

7 f the FMN or the accumulation of the anionic semiquinone.

8 tion competes with disproportionation of the semiquinone.

9 ilize significant amounts of the neutral FMN semiquinone.

10 action that oxidizes 4-methylcatechol to the semiquinone.

11 ogen bond donor to the methoxy oxygen of the semiquinone.

12 ges in the CW EPR signals of the cluster and semiquinone.

13 nzyme has been demonstrated to stabilize the semiquinone.

14 eactivity of the nonfluorescent intermediate semiquinone.

15 measure the association rate of the unstable semiquinone.

16 ducing a neutral quinone to a bound, anionic semiquinone.

17 at the Q(A) site may do the same for anionic semiquinone.

18 ncreased stabilization of both UQ-* and MQ-* semiquinones.

19 However, the o-semiquinone 1S generated by pulse radiolysis oxidation o

20 idpoint potentials are -114 mV (FMN oxidized/semiquinone), -212 mV (FMN semiquinone/hydroquinone), -2

21 idpoint reduction potentials of the oxidized/semiquinone (-315 +/- 5 mV) and semiquinone/dihydroquino

22 The neutral imino-semiquinone, 4,6-di-tert-butyl-2-tert-butylimino-semiqui

23 ite to facilitate binding of half-protonated semiquinone - a reaction intermediate that is potentiall

24 reduction of the yellow quinone to the blue semiquinone, a second 1.4 times faster electron transfer

25 The observed superoxo:semiquinone-, alkylperoxo-, and product-bound intermedia

26 ke up one electron yielding a stable anionic semiquinone, alpha-FAD, which donates this electron furt

27 coupling of a cyanophthalide and a p-methoxy semiquinone aminal to forge the anthraquinone moiety of

28 ) based on fusion of cyanophthalides (V) and semiquinone aminals (VI, VII) under basic conditions are

29 n of the triplet diradical complex of flavin semiquinone and (*)OOH.

30 rs an electron to the copper, giving radical semiquinone and Cu(I), the latter of which reduces O2 (p

31 flavin semiquinone; in contrast, the anionic semiquinone and hydroquinone species were observed with

32 n 19 and 135 ps, whereas the excited anionic semiquinone and hydroquinone states donate an electron t

33 D reduces cyt c at a higher rate in both the semiquinone and hydroquinone states.

34 behavior is consistent with that expected of semiquinone and hydroquinone-like moieties respectively.

35 generation of both an unstable neutral blue semiquinone and hydroquinone.

36 in other flavoproteins that form the anionic semiquinone and promote access of oxygen to N5.

37 Oxidation of semiquinone and reduction of cyt b or O(2) are subsequen

38 ed by spectroelectrochemistry to the quinone/semiquinone and semiquinone/hydroquinone couples of the

39 The quinone/semiquinone and semiquinone/hydroquinone midpoint potent

40 The generated radical intermediates, namely semiquinone and superoxide, are of great importance in r

41 The functional role of semiquinone and the EPR assignment of clusters N6a/N6b a

42 o the perturbed electron distribution in the semiquinone and the loss of enzymatic activity.

43 es from the oxidized form, to the more rigid semiquinone and to the much looser hydroquinone.

44 was reduced to its respective anionic flavin semiquinone and used for measuring inter-flavin distance

45 teristics in comparison with H-bonds between semiquinones and Ndelta in other quinone-processing site

46 rm a redox cycle that continuously generates semiquinones and reduced haem, both of which react with

47 75, the FMN potentials are -103 mV (oxidized/semiquinone) and -175 mV (semiquinone/hydroquinone) at p

48 quinone/hydroquinone), -236 mV (FAD oxidized/semiquinone), and -264 mV (FAD semiquinone/hydroquinone)

49 forms of the oxidized, neutral, and anionic semiquinone, and anionic hydroquinone states.

50 the relative proportions of hydroxyquinone, semiquinone, and quinone species in the macromolecule.

51 x states--oxidized form, neutral and anionic semiquinones, and neutral and anionic fully reduced hydr

52 radical-producing step by time resolving the semiquinone anion (Anq*-), ketyl radical (*-BPA), and Y*

53 etching region (1600-1660 cm(-1)) and in the semiquinone anion band (1440-1490 cm(-1)), as well as in

54 Semiquinone anion bands are resolved at approximately 14

55 ose to the Rieske protein, or if an unstable semiquinone anion intermediate diffuses rapidly to the v

56 f SP-AQH* or, for the other redox mediators, semiquinone anion-quinone electron exchange leading to n

57 of DHODB, small amounts of the neutral blue semiquinone are observed at approximately 630 nm, consis

58 This semiquinone arises, in part, by comproportionation betwe

59 75H mutant stabilizes an anionic form of the semiquinone as a result of the altered hydrogen bond net

60 inone as a single electron reductant, flavin semiquinone as the hydrogen atom source, and the enzyme

61 the presence of a short-lived anionic flavin semiquinone (ASQ) is not sufficient to infer the existen

62 Light reduces the dCRY FAD to an anionic semiquinone (ASQ) radical and increases CTT proteolytic

63 la CRY (dCRY) flavin cofactor to the anionic semiquinone (ASQ) restructures a C-terminal tail helix (

64 ich can be chemically reduced to the anionic semiquinone (ASQ).

65 med protonated superoxide and anionic flavin semiquinone at N5, before elimination of water affords t

66 revious pulsed EPR studies have shown that a semiquinone at the QH site formed during the catalytic c

67 e, while the other goes from flavoquinone to semiquinone, at almost exactly the same redox potential,

68 ine aldehyde were consistent with the flavin semiquinone being not involved in catalysis.

69 The remaining non-stabilized neutral semiquinone, beta-FADH(*), immediately reduces ferredoxi

70 obtained for our isostructural series of bis(semiquinone) biradicals shows that both the magnitude of

71 WT enzyme was green, due to air-stable FMN semiquinone (blue) and oxidized FAD (yellow).

72 ion of the isoalloxazine ring to the neutral semiquinone, both of which involve N5 protonation.

73 Semiquinone-bridged bisdithiazolyls 3 represent a new cl

74 n mixtures reveal trace amounts of a neutral semiquinone, but evidence for the presence of IPP-based

75 rations show that the protein stabilized the semiquinone by reducing the electrochemical midpoint pot

76 protons involved in hydrogen bonding to the semiquinone by substitution of 1H2O by 2H2O.

77 ng product, or it may be reduced back to the semiquinone by superoxide.

78 f direct one-electron oxidation of quinol to semiquinone by the Rieske protein.

79 Blue neutral FMN semiquinone can be readily observed; potentials of one e

80 ierpont's structurally characterized vanadyl semiquinone catecholate dimer complex, [VO(DBSQ)(DTBC)]2

81 from resonance Raman spectra to be a Cu(II)-semiquinone complex.

82 Using hypothetical Ga(3+)-catecholate/semiquinone complexes as references, 3,4-PCD-PCA was fou

83 uggesting that b(562) reduction also affects semiquinone concentration and superoxide production.

84 dioxygen, with the result that steady-state semiquinone concentrations in SRFA solutions are 2-3 ord

85 dized minus reduced difference spectrum of a semiquinone, consistent with charge recombination betwee

86 c-oxide synthase oxygenase FMN, FMN oxidized/semiquinone couple = +70 mV, FMN semiquinone/hydroquinon

87 P (midpoint reduction potential for oxidized/semiquinone couple = -105 mV/-105 mV) with respect to th

88 The redox potential of the quinone/semiquinone couple of flavodoxin (Fld) is much higher th

89 Arg-alpha237 substantially destabilizes the semiquinone couple of the bound FAD and impedes electron

90 altered to a larger extent than the oxidized/semiquinone couple which is understood by a simple elect

91 is the position of the aminoquinol/Cu(II) to semiquinone/Cu(I) equilibrium on anaerobic reduction wit

92 increases the concentration of the cofactor semiquinone/Cu(I) following anaerobic reduction by subst

93 this study indicate that changes in cofactor semiquinone/Cu(I) levels are not sufficient to alter the

94 ubstrate, which varies from almost 0% to 40% semiquinone/Cu(I).

95 In addition, the electronic structure of the semiquinone cyt aa(3)-600 is more shifted toward the ani

96 rein that 1S and related 5,6-dihydroxyindole semiquinones decay mainly by a free radical coupling mec

97 As a rule, o-semiquinones decay through disproportionation leading to

98 he reoxidation process being rate limited by semiquinone deprotonation.

99 the oxidized/semiquinone (-315 +/- 5 mV) and semiquinone/dihydroquinone (-365 +/- 15 mV) couples of t

100 ate ubiquinone reductase activity and in ETF semiquinone disproportionation.

101 Thus, the slow semiquinone dissociation may not indicate significant th

102 ALR forms large amounts of neutral semiquinone during aerobic turnover with DTT.

103 dependent accumulation of the neutral flavin semiquinone during both the flavoenzyme reduction and re

104 idpoint reduction potentials of the oxidized/semiquinone (E(1)) and semiquinone/hydroquinone (E(2)) c

105 line widths of the neutral and anionic flavo-semiquinone EPR signals are unchanged from the wild-type

106 H results in development of the neutral blue semiquinone FAD species.

107 st, we find that upon excitation the anionic semiquinone (FAD(*-)) and hydroquinone (FADH(-)) have lo

108 state and photoreduced to the neutral flavin semiquinone (FADH degrees ) in its lit state.

109 FAD) in subpicosecond and of neutral radical semiquinone (FADH(*)) in tens of picoseconds through int

110 chrome b subunits minimizes the formation of semiquinone-ferrocytochrome b(H) complexes at center N a

111 The directions of the TDMs in oxidized and semiquinone flavins were characterized decades ago, and

112 Electron transfer from the TPQ semiquinone follows in the first irreversible step to fo

113 mescale of seconds: conformational gating of semiquinone for both forward and reverse electron transf

114 eotide (FAD) cofactor in its neutral radical semiquinone form (FADH(*)) results in the formation of F

115 rdIs, the B. anthracis NrdI is stable in its semiquinone form (NrdIsq) with a difference in electroch

116 ry confirmed the strong stabilization of the semiquinone form by both YkuN and YkuP (midpoint reducti

117 significant fraction of NrdI resides in its semiquinone form in vivo, underscoring that NrdIsq is ca

118 binds tightly to and stabilizes the radical semiquinone form of 3,5-di-tert-butylcatechol.

119 Further, when the semiquinone form of ETF is used instead of the oxidized

120 ificantly stabilize the one-electron-reduced semiquinone form of FMN.

121 The anionic semiquinone form of the flavin, which is highly stabiliz

122 MADH to structurally imprint the as-purified semiquinone form of wild-type ETF and that the ability o

123 uinol form of reduced TPQ and TPQ(SQ) is the semiquinone form) occurs at a rate that could permit the

124 a copper-ligated cofactor proposed to be the semiquinone form.

125 line width was ~12 G, indicating its neutral semiquinone form.

126 ters in the [Fe(III)][FMNH(*)] (FMNH(*): FMN semiquinone) form of a human inducible NOS (iNOS) bidoma

127 nhibited by rotenone and likely derived from semiquinone formation at complex III.

128 The anionic semiquinone, formed by forward electron transfer at the

129 These results clearly indicate that the Q(B) semiquinone forms hydrogen bonds with two nitrogens and

130 ctures corresponding to the iminoquinone and semiquinone forms of the enzyme.

131 The one-electron reduced semiquinone forms transiently during the reaction, and t

132 The one-electron reduced semiquinone forms transiently during the reaction, and t

133 d YkuP were expressed in their blue (neutral semiquinone) forms and reoxidized to the quinone form du

134 The FAD anionic semiquinone found in the crystals assumes a conformation

135 omproportionation to yield the corresponding semiquinone free radicals, as detected by electron param

136 ethyl and methoxy hyperfine couplings in the semiquinone generated in the three proteins indicated ab

137 e oxidized enzyme, whereas an anionic flavin-semiquinone has been reported in the reduced enzyme.

138 The neutral quinone and anionic semiquinone have similar affinities, which is required f

139 tials of the oxidized/semiquinone (E(1)) and semiquinone/hydroquinone (E(2)) couples for the FMN (E(1

140 P450, and the elevated potential of the FMN semiquinone/hydroquinone couple (-172 mV) is also an ada

141 MN oxidized/semiquinone couple = +70 mV, FMN semiquinone/hydroquinone couple = -180 mV, and heme = -1

142 droquinone (midpoint reduction potential for semiquinone/hydroquinone couple = -382 mV/-377 mV).

143 The potentials of the semiquinone/hydroquinone couple of both FMN and FAD are

144 odoxin (Fld) is much higher than that of the semiquinone/hydroquinone couple.

145 ctrochemistry to the quinone/semiquinone and semiquinone/hydroquinone couples of the protein's flavin

146 The quinone/semiquinone and semiquinone/hydroquinone midpoint potentials (E(q/sq) an

147 The FMN semiquinone/hydroquinone redox couple was found to be si

148 hydroquinone and a 30 mV increase in the FAD semiquinone/hydroquinone reduction potential.

149 -103 mV (oxidized/semiquinone) and -175 mV (semiquinone/hydroquinone) at pH 7.0 and 25 degrees C, an

150 mV (FMN oxidized/semiquinone), -212 mV (FMN semiquinone/hydroquinone), -236 mV (FAD oxidized/semiqui

151 (FAD oxidized/semiquinone), and -264 mV (FAD semiquinone/hydroquinone).

152 ochrome aa(3)-600 in comparison with the ubi-semiquinone in cytochrome bo(3).

153 ersibility renders popular models based on a semiquinone in Q(o) site catalysis prone to short-circui

154 volved in a hydrogen bond formation with the semiquinone in the high-affinity Q(H) site in the cytoch

155 te Q-reduction state because it comes from a semiquinone in the outer quinone-binding site in complex

156 reduction state of the Q pool, presumably a semiquinone in the Q-binding site (site I(Q)).

157 It explains the observed properties of the semiquinone in the Q-binding site, the rapid superoxide

158 al signal in PM2.5 was remarkably similar to semiquinones in cigarette smoke.

159 quinone, with no stabilization of the flavin semiquinone; in contrast, the anionic semiquinone and hy

160 Superoxide oxidizes epinephrine to a semiquinone, initiating a series of reactions leading to

161 tron quinone redox chemistry that avoids the semiquinone intermediate altogether.

162 d electron-transfer mechanism, (2) a neutral semiquinone intermediate is formed in the biomimetic sys

163 t with an inner-sphere reaction of the Cu(I)-semiquinone intermediate with O(2) and are inconsistent

164 2) directly with the Cu(I) center of a Cu(I)-semiquinone intermediate.

165 uction, the isolated RnfG produces a neutral semiquinone intermediate.

166 d two-electron/two-proton transfer without a semiquinone intermediate.

167 inoquinol catalytic intermediate and a Cu(I)-semiquinone intermediate.

168 nsfer, avoiding formation of highly reactive semiquinone intermediates and producing quinols that pro

169 cal dianion species and the stability of the semiquinone intermediates during further reduction are d

170 Since semiquinone intermediates of quinol oxidation are genera

171 ine coupling of other protein nitrogens with semiquinone is <0.1 MHz.

172 The semiquinone is also formed in the D75E mutant, where the

173 The results support a model that the semiquinone is bound to the protein in a very asymmetric

174 tent with recently proposed models where the semiquinone is destabilized to limit superoxide producti

175 nd rearrangement of the oxidized dopamine, a semiquinone is formed.

176 n, limiting O(2) reduction; 2) the Q(o) site semiquinone is highly stabilized making it unreactive to

177 serve that, while the transient formation of semiquinone is not proton-coupled, the second eT process

178 The neutral form of this semiquinone is observed during reductive titration of IY

179 is for the air stability of the neutral blue semiquinone is protonation of the flavin N5 and strong H

180 The semiquinone is substoichiometric, even with conditions o

181 coupling of other protein nitrogens with the semiquinone is weak (<0.1 MHz).

182 -) = 2,5-dioxidobenzoquinone/1,2-dioxido-4,5-semiquinone), is shown to exhibit a conductivity of 0.16

183 quinone, 4,6-di-tert-butyl-2-tert-butylimino-semiquinone (isqH.), can be prepared by a conproportiona

184 The semiquinone-like organic species formed during photolysi

185 ived organic species, (ii) relatively stable semiquinone-like organic species, and (iii) hydroperoxy

186 ecause of the stabilization by anthocyanidin semiquinone-like resonance.

187 pecificity by raising barriers in defense of semiquinone loss or energy wasting short-circuit reactio

188 First, electrons from the ETF flavin semiquinone may enter the ETF-QO flavin one by one, foll

189 If a Cu(I)-TPQ semiquinone mechanism operates, then an alternative oute

190 are inconsistent with a sequential "movable semiquinone" mechanism but are consistent with a model i

191 e-binding pocket of complex II, and unstable semiquinone mediated by the Q cycle of complex III.

192 ity and reactivity of reaction intermediate, semiquinone, might require a cofactor that functions to

193 As a result, semiquinone moieties in SRFA play a much more important

194 mpound that possesses a Donor-Acceptor (D-A) SemiQuinone-NitronylNitroxide (SQNN) biradical ligand.

195 ause of flavin photoreduction to the neutral semiquinone (NSQ).

196 71 mV with two electrons, consistent with no semiquinone observed in the potential range studied, a r

197 The semiquinone of DeltaG141/E142N was slightly more stable

198 uclei similar to those recorded for the blue semiquinone of free flavins in aqueous solution, thus co

199 orientation, be it the sole identity of the semiquinone or not, blocks the oxygen-binding site, sugg

200 account for this behavior: 1) The Q(o) site semiquinone (or quinol-imidazolate complex) is unstable

201 st example of free radical dimerization of o-semiquinones outcompeting the classic disproportionation

202 decrease 1000-fold and the rate constant for semiquinone oxidation by b(566) to depend on the b(562)

203 s of reducing equivalents which results from semiquinone oxidation to quinone.

204 ted in a specific alteration of the rates of semiquinone oxidation.

205 transfer in photolyase, particularly for the semiquinone photoreduction process, which involves nearb

206 Moreover, semiquinones produced at the flavin site initiate redox

207 gen bonds to the two carbonyl oxygens of the semiquinone Q(A)(.-) in the reaction center (RC) from th

208 gen bonds to the two carbonyl oxygens of the semiquinone QA*- in the well-characterized reaction cent

209 een the OH group of Ser-L223 and the anionic semiquinone QB-*.

210 The semiquinone/quinone reoxidation is found to exhibit slow

211 chain-propagating species, the deprotonated semiquinone radical (SQ(*) (-)) generated from both the

212 the formation of the protein tyrosine ortho-semiquinone radical (ToQ.).

213 a big concern, because the catechol-derived semiquinone radical after the oxidation of catechol (CA)

214 These states include the anionic semiquinone radical and fully reduced neutral and anioni

215 e low-energy (3)MLCT(SQ) state (Ru(III) phen-semiquinone radical anion) as the predominant nonradiati

216 mmogram, which leads to the formation of the semiquinone radical anions (P)-(+)-1(*-) and (M)-(-)-1(*

217 gher the steady-state level of the resulting semiquinone radical at near neutral pH.

218 We report the first direct detection of a semiquinone radical generated by the Q(o) site using con

219 A stable neutral flavin-semiquinone radical is observed in the air-oxidized enzy

220 A neutral flavin-semiquinone radical is observed in the oxidized enzyme,

221 uced forms exhibit neutral and anionic flavo-semiquinone radical signals, respectively, demonstrating

222 uggesting that Int-2 is a peroxo-Fe(III)-4NC semiquinone radical species.

223 eased amounts of reactive oxygen species and semiquinone radical, both of which can cause DNA damage,

224 adical, Ph = 1,4-phenylene, SQ = S = (1)/(2) semiquinone radical, Cat = S = 0 catecholate, and py = p

225 1 complex in the presence of an intermediate semiquinone radical, thus making the Qo-site a strong ca

226 ation methods gave rise to a transient DOPAL semiquinone radical, which was characterized by electron

227 d a species with the optical properties of a semiquinone radical.

228 yrosyl radical in the formation of the ortho-semiquinone radical.

229 uced enzyme exhibits a stable anionic flavin-semiquinone radical.

230 -based reaction mechanism possibly involving semiquinone radical.

231 tron out of the substrate to form a reactive semiquinone radical.

232 ces Fe(III) in acidic conditions, generating semiquinone radicals (Q(*-)) that can oxidize Fe(II) bac

233 oth dihydroxy PCBs and PCB quinones can form semiquinone radicals (SQ(*-)) in vitro.

234 environments, we were able to stabilize two semiquinone radicals and thus observed their weak emissi

235 Reactive semiquinone radicals are quickly produced upon the encou

236 These semiquinone radicals are reactive intermediates that hav

237 However, the semiquinone radicals generated in pure hydroquinone solu

238 are rapidly oxidized by dioxygen, while the semiquinone radicals generated in SRFA solution are resi

239 e critical role of quinoid intermediates and semiquinone radicals in CL generation from polychlorinat

240 inoid intermediates, but more interestingly, semiquinone radicals were produced during the degradatio

241 of O2 due to further cycling between oxygen, semiquinone radicals, and iron species.

242 The generation of semiquinone radicals, superoxide, and hydroxyl radicals

243 ve proxies, which includes the generation of semiquinone radicals.

244 of adrenochrome increases if the epinephrine semiquinone reacts with O(2) to form more superoxide, bu

245 stabilized blue semiquinone with an oxidized/semiquinone reduction potential of -179 mV.

246 in thermodynamic destabilization of the FAD semiquinone relative to the hydroquinone and a 30 mV inc

247 (14)N and (15)N HYSCORE spectra of the Q(B) semiquinone show the interaction with two nitrogens carr

248 More than 90% of the semiquinone signal originated from the single entity wit

249 The semiquinone signal(s) decreased by 60% when with asimici

250 Furthermore, we found small but significant semiquinone signal(s), which have been reported only for

251 For the FAD semiquinone, significantly different potentials were obt

252 of a spin interacting state between the FMN semiquinone species and the reduced 2Fe-2S center.

253 In each case, blue neutral flavin semiquinone species are stabilized on both flavins, and

254 The semiquinone species disappeared upon full reduction and

255 ference in the steady-state concentration of semiquinone species has a dramatic effect on the cycling

256 Paramagnetic interactions show that the new semiquinone species is buried in the protein, probably i

257 on." It is believed that a strongly reducing semiquinone species is essential for this process, and i

258 the redistribution of charge density in the semiquinone species, or the altered hydrogen bonding net

259 tate ubiquinone (UQ) and its reduced anionic semiquinone (SQ(-)) from the Q(A) site.

260 trogens from residues R71 and H98 around the semiquinone (SQ) at the high-affinity Q(H) site.

261 protons in the immediate neighborhood of the semiquinone (SQ) at the Qi-site of the bc1 complex (ubih

262 acterize the exchangeable protons around the semiquinone (SQ) in the Q(A) and Q(B) sites, using sampl

263 The design of novel, functionalized semiquinone (SQ) ligands which combine structural rigidi

264 ully oxidized (ox), the one-electron reduced semiquinone (sq), or the two-electron fully reduced hydr

265 ter P by reducing quinone (Q) at center N to semiquinone (SQ), which is bound tightly.

266 oxidized quinone, (ii) one-electron reduced semiquinone (stable neutral species (blue) or unstable r

267 protein environment for Q(B) in its reduced semiquinone state and suggest that the conformational ch

268 the unusually high stability of the anionic semiquinone state in wETF.

269 mammalian cytochrome P450 reductase, the FMN semiquinone state is not thermodynamically stable and ap

270 gen bonds in the redox tuning of the primary semiquinone state of photosystem II.

271 f IPP-bound enzyme indicate that the neutral semiquinone state of the flavin is stabilized thermodyna

272 dating the tuning and control of the primary semiquinone state, Q(A)(-), of photosystem II.

273 ibution map in the isoallosazine ring in its semiquinone state.

274 PSAO) exists predominantly in the Cu(I), TPQ semiquinone state.

275 but to a much greater extent for the anionic semiquinone state.

276 ximately 110 mV between the hydroquinone and semiquinone state.

277 rmined that the excited neutral oxidized and semiquinone states absorb an electron from the adenine m

278 vin interactions of the oxidized and anionic semiquinone states of the electron-transfer flavoprotein

279 placements destabilize both the oxidized and semiquinone states of the flavin, but to a much greater

280 Raman bands in both the oxidized and anionic semiquinone states of the protein.

281 ilization of the one-electron-reduced flavin semiquinone that is differentially expressed in the nitr

282 barrier toward the reduction of the anionic semiquinone that is observed in the wild-type wETF was e

283 which is readily photoreduced to the anionic semiquinone through a set of 3 highly conserved Trp resi

284 ge in the radicals formed was observed--from semiquinone to chlorophenoxyl radicals.

285 vin cofactor, one of which is converted from semiquinone to flavohydroquinone, while the other goes f

286 ith g-value between 2.0029 and 2.0044, and a semiquinone-type radical, with g-value from 2.0050 to as

287 These radicals are similar to semiquinone-type, environmentally persistent free radica

288 and thermodynamic destabilization of the FAD semiquinone uncouples or limits electron transfer to an

289 The enzyme-bound anionic flavin semiquinone was unusually insensitive to oxygen or ferri

290 Nonetheless, both DeltaGly-141 red semiquinones were less stable than those of the correspo

291 uced, and reduction of b(562) stabilized the semiquinone when b(566) was oxidized.

292 tein complex (CaCaMxFMN) forms an air-stable semiquinone when reduced with NADPH and reduces cytochro

293 Instead, O2 oxidizes the 4-methylcatechol semiquinone, which is formed by comproportionation of 4-

294 ggest that DNQ undergoes bioreduction to its semiquinone, which then is re-oxidized by molecular oxyg

295 reduced form of enzyme is an anionic flavin semiquinone, whose formation requires the substrate, but

296 eads to formation of an unstable red anionic semiquinone with a more negative potential than the hydr

297 The FMN formed a kinetically stabilized blue semiquinone with an oxidized/semiquinone reduction poten

298 differences in the interactions of the mena-semiquinone with cytochrome aa(3)-600 in comparison with

299 ed to study the interaction of the Q(B) site semiquinone with nitrogens from the local protein enviro

300 rous cyt P450 and oxidizes to the air-stable semiquinone, with rate constants of 8.4 and 0.37 s(-1) a

301 coupling, J) involving a spin SD = 1/2 metal semiquinone (Zn-SQ) donor and a spin S(A) = 1/2 nitronyl