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Several studies have described that quinoid rings with electron-rich olefins at re
mote position experiencechanges in their redox potential. Since the original description of these changes, different approacheshave been developed to describe the properties of the binding sites of ubiquinones. The origin of thispheno
menon has been attributed to lateral chain flexibility
and its effect on the recognition betweenproteins
and substrates associated with their i
mportant biological activity. The use of electroche
mical-electron spin 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 confor
mers of perezone [(2-(1,5-di
methyl-4-hexenyl)-3-hydroxy-5-
methyl-1,4-benzoquinone] established that a weak
![](/i<font color=)
mages/gifchars/pi.gif" BORDER=0 >-
![](/i<font color=)
mages/gifchars/pi.gif" BORDER=0 > interaction controls not only the
molecular confor
mation but also its diffusion coefficient
and electroche
mical properties. An analogousinteraction can be suggested as the origin of si
milar properties of ubiquinone Q
10. The use of nuclear
magnetic resonance rendered, for the first ti
me, direct evidence of the participation of different perezoneconfor
mers in solution
and explained the cycloaddition process observed when the afore
mentioned quinoneis heated to for
m pipitzols, sesquiterpenes with a cedrene skeleton. The fact that biological syste
ms can
modulate the redox potential of this type of quinones depending on the confor
mer recognized by anenzy
me during a biological transfor
mation is of great relevance.