a possible origin of semiconducting dna hiori kino(nims) masaru tateno(tit & aist) mauro...
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A possible origin of semiconducting DNA
Hiori Kino(NIMS)
Masaru Tateno(TIT & AIST)
Mauro Boero(Univ. Tsukuba &AIST)
Jose Torres(Univ. Tsukuba)
Takahisa Ohno(NIMS)
Kiyoyuki Terakura(Univ. Hokkaido & AIST)
Hidetoshi Fukuyama(Univ. Tohoku)
•Introduction•DC conductivity measurements•Theoretical study so far•This work, theoretical study•Anderson localization
History
1. Radiation damageDNA is damaged by ultraviolet rays. “How does a hole or electron created by ultraviolet rays move in DNA?”→ electron transfer theory
2. Is DNA metallic or insulating?They measured DC conductivity.
Electron/hole hopping measurements in DNA
UV
If electrons/holes move rapidly, little radiation damage
DNA in a living body
HOMO(band)
LUMO(band)
UV light(trigger)
energy
Gap ~ 6-7eV
Motion of a existing hole/electron
DC transport measurement
I
dry DNA
V (trigger)
L
R
)()()( RFLF nnTdI (Landauer formula)
L
R
RLV
nF()
~Temperature
~T
If V is very small
Possibility of low energy excitation ~TWhere does a hole/electron come from?
Two kinds of exp.
HOMO(band)
LUMO(band)
UV light(trigger)
Chemicalpotential
energy
Gap ~ 6-7eV
~T
Electron transfer by UV light DC transport
Energy scale ~ 100eVEnergy scale < 102Kelvin
No density of states→No transportQ. Finite DOS at
Nano device?
•DNA : small crosssection (~2nm): self-assemble (utilizing complementary pairs of base molecules)
Figures, from C. Dekker, Phys. World. 14, 29 (2001).
•Low resistance useful nanowire
Seeman’s cubeHolliday junction
•Etching technology of ultra-fine structures will encounter the barrier in the near future
1.4kbase single-stranded DNA→octahedron
Another example
W.M. Shih, et al., Nature, 427, 618 (2004).
Diameter~14nm
Raw mages by cryo-electron microscopy
DNA gearJ. Am. Chem. Soc., 126 (37), 11410 -11411, 2004.“Molecular Gears: A Pair of DNA Circles Continuously Rolls against Each Other “Ye Tian and Chengde Mao*
DNA biped walking deviceNano Letters, 4 (7), 1203 -1207, 2004“A Precisely Controlled DNA Biped Walking Device “ (bike= 二本足歩行 )William B. Sherman and Nadrian C. Seeman*
DNA nano-machine
•Introduction•DC conductivity measurements•Theoretical study so far•This work, theoretical study•Anderson localization
DC conductivity measurement
De Pablo et al. Phys. Rev. Lett. 85, 4992 (2000)
-DNA, scanning force microscopy~105cm (>70nm) (T=RT)
Bundle of DNA
Summary of Experiments
Fink et al., Nature 398, 407(1999)
Porath et al., Nature 403, 635(2000)
10-4cm(600nm-900nm),T=RT
10.4nm, T=100K-RT
-DNA
dG-dC
Cai, et al., APL 77 (2000) 3105
dG-dC
-DNA
Pablo et al. Phys. Rev. Lett. 85, 4992 (2000).
T=RT
T=RT
Yoo, et al. RPL 87 (2001) 198102
T=4.2K-RT
dG-dC
105cm (70nm)
1cm (50nm)
10-2cm (>20nm)
106cm (4m) -DNA
Zhang et al. Phys. Rev. Lett. 89, 198102-1 (2002).T=RT?
Metal,Insulator and doped semiconductor
Band gap~T*
~eV ~eV
E E E
E E
Impurity host
Thermally doped Intrinsically doped
metal insulator
schematically
semiconductor
Conductivity of semiconductor several order of magnitude depending on the density of impurities
•Introduction•DC conductivity measurements•Theoretical study so far•This work, theoretical study•Anderson localization
Structure of DNA
PO4
base moleculesbackbone
• G:C, A:T= hydrogen bond
• PO4= -1 charged, DNA=negatively charged system at pH~7
• charge neutrality= cations (Na+, K+, Mg++,…)
Figures, from C. Dekker, Phys. World. 14, 29 (2001).
sugar
Theoretical Study
PW91/6-31G(d,p)
Electronic structure of base molecules
GpC: HOMO G LUMO C
ApT: HOMO A LUMO T
Blue=HOMO, Red=LUMOcompletely separated, G-C: hydrogen bonding
(acid) Poly(dG)-poly(dC) (PO4- is terminated by H+, the system is neutral)
Artacho et al. Mol. Phys. 101 (2003), 1587.DFT/GGA, SIESTA
→Insulating(gap~2eV), (LDA underestimates band gap.)
EF
CG
ij
jiij cctH e.g. HOMO band
Theoretical study (2)Electronic structure of DNA
G
C
Is semiconducting DNA possible?
~eV ~eV
E E
insulator semiconductor
There can be some methods to dope carriers into insulating DNA.
carriers!
E.g. P is added to dope carriers into insulating Si. ppm order of P is sufficient to make Si conducting.
Shift
•Introduction•DC conductivity measurements•Theoretical study so far•This work, theoretical study•Anderson localization
Possible electronic structuresPoly(dG)-poly(dC)
HOMO(G)
LUMO(C)
(Without dopant)
DOS
(With dopant)
HOMO(G)
LUMO(C)
DOS(host)DOS(dopant)
hole
[(dG) 2
-X+?](X:impurity)
G
G
impurity
Intrinsic doping
Condition of DNA in experiments
GC
GC
DNA in solution
Dry DNA
Most cation metals are with solvation shells, some may be anhydrous
H2O
Possible loci of cations(study of effects of solvation shell of catons)
There are many possible loci of cations.There may be many possible loci of cations which dope carriers into DNA.
In this study, examine the electronic structure of one typical locus.
cation
DNA
Electronic structure of DNA hydrate v.s. anhydrous Mg
GC
[(dG)2Mg(H2O)n]+
PO4-1
Mg2+
Calc. UHF/6-31G(d)
(GGA/PBE gap~0.7eV)
(a)HOMO
LUMO
7.6 eV
Occupied stateB
(c)
G G(b)(a)
(c)
Unoccupied state
(b)Sz=0Mg2+
hydrated Mgcations
anhydrous Mgcation
LUMO
SOMO
(c’)
(b)
(a)(b)
(c’) Sz=1
(c’)
Mg+
LUMO@G
Schematic electronic structure of dry DNA
HOMO(G)
LUMO
DOS(host)DOS(dopant)
hole
[(dG) 2
-Mg2+]
G HOMO
impurity
poly(dG)-poly(dC)with anhydrous Mg
•Intrinsic doping = localized spin moment at Mg
# of injected holes into guanine HOMO band
# of anhydrous Mg=
A. degree of drying
Q. A possible origin of the diverse experimental results
Experimental suggestion of another method of doping I3
- , M. Taniguchi et al. Jpn. J. Apl. Phys. 42 (2003), L215
There will be a number of methods to dope carriers into insulating DNA chains.
c.f. P@Si, ppm order Very small # of injected holes can make DNA conducting
Maybe it is very hard to remove solvation shells.
Comment: doping a hole is different from moving of the hole easily
Other divalent cations Sz=0(para) Sz=0(AF) Sz=1(ferro) the most stable
A Mg -2604.691 -2604.700 -2604.725 ferroB Mg -2604.680 -2604.711 -2604.711 AF/ferro
A Zn -4182.521 -4182.581 -4182.555 AFB Zn -4182.482 -4182.546 -4182.536 AF
A Ca -3081.868 -3081.864 -3081.838 paraB Ca -3081.857 NG -3081.829 para
stru
ctur
eca
tion
GC
X PO4-
PO4-
X PO4-
X PO4-
PO4- X
PO4- Mg+
PO4- X
PO4- X
J
Intrinsic
Intrinsic
Thermal?
Doping mechanism
Band gap~T*EF
E E
Impurity Mother material
Unit: A.U., Gaussian 6-31G(d)/UHFabbreviation: A Mg = Mg@A-DNA
•Introduction•DC conductivity measurements•Theoretical study so far•This work, theoretical study•Anderson localization
Anderson localization
•If DNA has doped one-dimensional band → Anderson localization •In one-dimension, no mobility edge → the wavefunction is always localized.•Long-ranged hopping mechanism → maybe variable range hopping (VRH)
E
(Assumption of VRH=doped band)
EF
band
Nonzero DOS at EF
Polaron and so on. may be necessary at higher temperatures. We do not deny their theories.At very low temperature, Anderson localization plays important roles.
I-V curve ---electronic contribution---
nTTA /100 )/(exp
n=dimension+1 Mott VRHn=2 Efros-Shklovskii(ES) VRH
Log
[ co
nduc
tivity
]
(103/T)1/2
Replot from Yoo, et al. RPL 87 (2001) 198102
n=2T0~90K (poly(dG)-poly(dC))
4.2K
Non-ohmic conductivity OK!
ndn
d
T
eE
T
TJ
R
T
ReE
TRJ
//1
0 cos2
1expcos~
/1~
2exp~
-1: localization length
Nonohmic threshold band gap
(V)
Stacked DNA into the gate
Exp. Yoo, et al. RPL 87 (2001) 198102.Theory. adopted the theory by H. Fukuyama and K. Yosida, J. Phys. Soc. Jpn. 46, 102 (1979).
Summary
•Intrinsic doping: Mg->ferro, Zn->antiferro•(Thermal doping: Ca ?)
Hydrated cation
Anhydrous cationHOMO
LUMO
SOMO
LUMO
An injected hole
J
00 SsJcctHij
jiij
# of doped holes= # of anhydrous Mg or Zn,
or thermally doped
(Longer chains must be calculated )
CommentsThe most stable structures of Mg@G2
Siesta (GGA+PCC): paramagnetic, HOMO=G, LUMO=MgGaussian98(HF): Ferromagnetic, SOMO=Mg, LUMO=GGuassian98(PW91PW91): Ferromagnetic, SOMO=Mg, LUMO=G
In STATE(ultrasoft PS, GGA) and CPMD(GGA), to achieve self-consistency is harder. Ferromagnetic solution seems to be the most stable.
Some LDA/GGA calculations of anhydrous Mg@DNA are unstable probably due to the self-interaction correction problem. Mg is spatially localized. Maybe it is connected with the result of siesta. Siesta uses localized PAOs which may raise the orbital energy of isolated Mg more than those of extended states of DNA base molecules. Careful consideration may be necessary to use PAOs in this case.
(G: guanosine)
Electronic structure of DNA (GGA/PBE)
GP
O-
O
G
Mg++
“Mg++”Paramag.(Sz=0)
G HOMO (ev)
EF
HOMO-1 HOMO LUMO
siesta
Doped semiconductors
1/T
Log[nc]
-1/2 Eg
-1/2(c-d)
(c-d)
Log
[ co
nduc
tivity
]
(103/T)1/2
Aschcroft and Mermin, Solid State Physics, page 580 on ‘Homogenious Semiconductors’
d
c
Eg
Replot from Yoo, et al. RPL 87 (2001) 198102
DOS
DNA exp.
textbook