Using the fl
ash-quench technique to probe
DNA ch
arge tr
ansport in
assemblies cont
aining
a tethere
d ruthenium interc
al
ator, the kinetics
an
d yiel
d of methylin
dole r
adic
al form
ation
as
a function of DNA sequence were stu
die
d by l
aser spectroscopy
an
d biochemic
al metho
ds. In these
assemblies, the methylin
dole moiety serves
as
an
artifici
al b
ase of low oxi
dation potenti
al. Hole injection
an
d subsequent form
ation of the methylin
dole r
adic
al c
ation were observe
d at
a dist
ance of over 30 Å
at r
ates
![](/im<font color=)
ages/entities/ge.gif">10
7 s
-1 in
assemblies cont
aining no gu
anine b
ases intervening the ruthenium interc
al
ator
an
d GMG oxi
dation site. R
adic
al yiel
d w
as, however, strikingly sensitive to
an intervening b
ase mism
atch; no signific
ant methylin
dole r
adic
al form
ation w
as evi
dent with
an intervening AA mism
atch. Also critic
al is the sequence
at the injection site; this sequence
determines initi
al hole loc
aliz
ation
an
d hence the prob
ability of hole prop
ag
ation. With gu
anine r
ather th
an inosine ne
ar the site of hole injection,
decre
ase
d yiel
ds of r
adic
als
an
d long-r
ange oxi
dative
dam
age
are observe
d. The presence of the low-energy gu
anine site in this c
ase serves to loc
alize the hole
an
d therefore
diminish ch
arge tr
ansport through the b
ase p
air st
ack.