PACE=5> |
Several studies have described that quinoid rings with electron-rich olefins at remote
position ex
periencechanges in their redox
potential. Since the original descri
ption of these changes, different a
pproacheshave been develo
ped to describe the
pro
perties of the binding sites of ubiquinones. The origin of this
phenomenon has been attributed to lateral chain flexibility and its effect on the recognition between
proteins and substrates associated with their im
portant biological activity. The use of electrochemical-electron s
pin resonance (EC-ESR) assays and theoretical calculations at MP2/6-31G(d,
p) and MP2/6-31++G(d,
p)//MP2/6-31G(d,
p) levels of several conformers of
perezone [(2-(1,5-dimethyl-4-hexenyl)-3-hydroxy-5-methyl-1,4-benzoquinone] established that a weak
![](/images/gifchars/<font color=)
pi.gif" BORDER=0 >-
![](/images/gifchars/<font color=)
pi.gif" BORDER=0 > interaction controls not only themolecular conformation but also its diffusion coefficient and electrochemical
pro
perties. An analogousinteraction can be suggested as the origin of similar
pro
perties of ubiquinone Q
10. The use of nuclearmagnetic resonance rendered, for the first time, direct evidence of the
partici
pation of different
perezoneconformers in solution and ex
plained the cycloaddition
process observed when the aforementioned quinoneis heated to form
pi
pitzols, sesquiter
penes with a cedrene skeleton. The fact that biological systems canmodulate the redox
potential of this ty
pe of quinones de
pending on the conformer recognized by anenzyme during a biological transformation is of great relevance.