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  1. 1 University of Athens, Physics Department, Athens, Greece 2 University of Patras, Materials Science Department, Patras, Greece 0 (no longer at Leibniz Institute for Neurobiology, Magdeburg, Germany) small polaron hopping A model for the multi-phonon-assisted transport along DNA molecules, in the presence of disorder Title-affiliation Georgios Triberis 1, Constantinos Simserides1,2,0, Vasileios Karavolas 1

  2. outline - Experiments (3 slides) - System Characteristics (3 slides) - Model (… slides)

  3. Interpretation Low-T: ionic conduction (counterions) but cannot account for high-T λ phage DNA Experiment 1 (no contacts – resonant cavity σ = σ(T) at high / low T High-T: carrier excitations across single-particle gaps or T-driven hopping Alternatively phonon-assisted polaron hopping

  4. Interpretation a small polaron hoppingmodel poly(dA)-poly(dT), poly(dG)-poly(dC) Experiment 2 I-V(T) i.e. G = G(T) at high / low T poly(dA)–poly(dT): hopping distance ~ 16.8 Å(5 base pairs) poly(dG)–poly(dC): hopping distance ~ 25 Å(7 base pairs!) Interpret Tran et al? not quite convincing other possible mechanisms? I ~ b V fitting parameter b (with unclear T-dependence)

  5. Interpretation: activated Arrhenius law + constant or variable range hopping + constant native wet-spun calf thymus Li-DNA Experiment 3 σ = σ(T) at high T

  6. … we have to take into accountthe system characteristics

  7. base pair separation ~ 3.4 Å helix step ~ 34 Å DNA double helix (1) deoxyribose nucleic acid two helices = two polynucleotide strands nucleotide = phosphate + sugar+ base (A, T, C, G)  4 nucleotides 4 bases Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Minor groove ~ 1.2 nm Major groove ~ 2.2 nm base pairs: Cytosine <3 Η bonds> Guanine Αdenine <2 Η bonds> Τhymine

  8. Vibrating (phonons) Vibrating (phonons) site j site i (2) deoxyribose nucleic acid H bond length ~ 2.9Å “random”(non-periodic) base sequence (disorder one) base pair separation (i,i+1) ~ 3.4 Å (helix step ~ 34 Å)

  9. (3) deoxyribose nucleic acid diameter ~ 20 Å base end to end separation ~ 10.7 Å Phosphate has a negative charge Phosphate attracts counterions e.g. K+, Na+, etc H bond length ~ 2.9 Å (disorder two)

  10. Polaron 2. Electron (linear interaction) 1, 2 comparable magnitude εi(0) 1. Phonon (parabolic … + nearest neighbors) 3. Polaron formation (Eb(i)) - Ai xi MCM (Molecular Crystal Model) 1D ordered all i equivalent T. Holstein, Ann. Phys. NY 8(1959) 343 GMCM (Generalized Molecular Crystal Model) 3D disordered G. P. Triberis and L. R. Friedman, J. Phys. C: Solid State Phys. 14 (1981) 4631 high-T G. P. Triberis, J. Non-Cryst. Solids 74 (1985) 1 low-T

  11. i) GMCM ii) Percolation UnSuccessful low-T (all experiments above) ionic conductivity? sth else? What is the character of our system? What must the model take into account? (2) It is plausible that the carriers are small (wavefunction extent) polarons (phonon + electron). Phonon (parabola + nearest neighbors). • Molecular wire (quasi one dimensional character). Each base pair can be considered as a molecular site. (3) Disorder (random base sequence, counterions) • multi-phonon assisted polaron hopping few-phonon assisted hopping analytical expressions for σ=σ(Τ) rm = rm(T) Successful high-T (all experiments above) fitting σ = σ(T) reasonable rm = rm(T)

  12. Wij0h depends on Ei and Ej Wij0ℓ depends on Ei or Ej transport problem transformed to equivalent network of impedances V. Ambegaokar, B. I. Halperin and J. S. Langer, Phys. Rev. B 4 (1971)2612 percolation condition high-T ≠ percolation condition low-T conductivity high-T ≠ conductivity low-T equilibrium transition probability equilibrium occupation probability intrinsic transition rate The analytical expressions high-T (multi-phonon-assisted) ≠ low-T (few-phonon-assisted)

  13. Conductivity high-T low-T

  14. G. P. Triberis, C. Simseridesand V. C. Karavolas, J. Phys.: Condens. Matter 17 (2005) 2681–2690 High-TTran et al

  15. G. P. Triberis, C. Simseridesand V. C. Karavolas, J. Phys.: Condens. Matter 17 (2005) 2681–2690 High-T Yoo et al

  16. Percolation conditionhigh-Tlow-T max hopping distance max site energy max hopping distance max site energy r (spatial dimension) = 1 ε (number of energies) = 1 r (spatial dimension) = 1 ε (number of energies) = 2

  17. ε = number of energies in the percolation condition r = spatial dimensions Conductivity “Law” 3Dhigh-TT-2/5Triberis and Friedman 3D low-TT−1/4Mott 2D low-TT−1/3 Pollak 1Dhigh-TT−2/3 here 1D low-TT−1/2 here and inaccordance with variable range hopping for localized states Pollak, Lee, Serota et al

  18. Synopsis - Conclusion

  19. AcknowledgmentsFrank Angenstein(Leibniz Institute for Neurobiology, Magdeburg, Germany)Georgia Thodi(DUTh, Molecular Biology and Genetics Department, Alexandroupolis, Greece) End.Thank you.

  20. Bibliography – Sources Theory + Experiments 1. G. P. Triberis, C. Simseridesand V. C. Karavolas, J. Phys.: Condens. Matter 17 (2005) 2681–2690 “Small polaron hopping transport along DNA molecules” 2. P. Tran, B. Alavi and G. Gruner,Phys. Rev. Lett. 85 (2000) 564 3. K. H. Yoo et al, Phys. Rev. Lett. 87 (2001) 198102 * 4. Z. Kutnjak et al, Phys. Rev. Lett. 90 (2003) 098101 5. H. Bottger and V. V. Bryksin (1985) Hopping Conduction in Solids (Berlin: Akademie-Verlag) p.73[a small polaron hopping model] * 6. Ch. Adessi and M. P. Anantram, Appl. Phys. Lett. 82 (2003) 2353 [counterion-induced disorder] 7. W. Zhang, O. Govorov and S. E. Ulloa, Phys. Rev. B 66 (2002) 060303 [Polarons with a twist] 8. Z. G. Yu and X. Song, Phys. Rev. Lett. (2001)86 6018 [variable range hopping ** + T-dependent localization length] 9. N. F. Mott and E. A. Davis (1971) Electronic Processes in Non-Crystalline Solids (Oxford: Oxford University Press) p. 216 ** 10. S. S. Alexandre et al, Phys. Rev. Lett. 91 (2003) 108105 [ab initio poly(dC)–poly(dG)] [evidence for small polaron formation] 11. T. Holstein, Ann. Phys. NY 8(1959) 343 [Molecular Crystal Model] 12. G. P. Triberis and L. R. Friedman, J. Phys. C: Solid State Phys. 14 (1981) 4631 [Generalized MCM] disordered high-T 13. G. P. Triberis, J. Non-Cryst. Solids 74 (1985) 1 [Generalized MCM] disorderedlow-T 14. V. Ambegaokar, B. I. Halperin and J. S. Langer, Phys. Rev. B 4 (1971)2612 [equivalent network of impedances] 15. M. Pollak, 1978 The Metal–Non-Metal Transitions in Disordered Systems,ed L R Friedman andD P Tunstall (Edinburgh) p 138, 139 [percolation condition]

  21. Bibliography –Sources Theory + Experiments 16. G. P. Triberis, Semiconductors 7 (1993) 471 [review on amorphous materials] 17. D. Emin, Adv. Phys.24 (1975)305 [microscopic velocity operator] 18. We use α−1 = 2 Å, within the range of values usually used for DNA and similar structures J. A. Reedijk et al, Phys. Rev. Lett. 83 (1999) 3904 Z. G. Yu and X. Song, Phys. Rev. Lett. (2001)86 6018 19. P. A. Lee, Phys. Rev. Lett. 53 (1984) 2042 ; R. A. Serota, R. K. Kalia and P. A. Lee, Phys. Rev. B 33 (1986) 8441, and Pollak (15.) [T−1/2, variable range hopping** between localized states] See also Z. G. Yu and X. Song, Phys. Rev. Lett. (2001)86 6018 20. G. P. Triberis, Semiconductors7 (1993)471 [brief review application to amorphous 3D] Some illustrations used in this talk were processed after copying from: 1. National Human Genome Research Institute (http://www.genome.gov/). All of the illustrations in the Talking Glossary of Genetics are freely available and may be used without special permission. 2. Wikipedia the free-content encyclopedia (http://en.wikipedia.org/).

  22. Mechanisms proposed for strong σ=σ(T) at high-T unistep superexchange and multistep hopping [16, 17] [16] Jortner J 1998 Proc. Natl Acad. Sci. USA 95 12759 [17] Ratner M 1999 Nature 397 480 and references cited therein carrier excitations across single-particle gaps [18] [18] Tran P, Alavi B and Gruner G 2000 Phys. Rev. Lett. 85 564 bandlike electronic transport [19] [19] Cuniberti G et al 2002 Phys. Rev. B 65 241314 variable range hopping [20] [20] Yu Z G and Song X 2001 Phys. Rev. Lett. 86 6018 small polaron transport [21–26] [21] Sartor V, Henderson P T and Schuster G B 1999 J. Am. Chem. Soc. 121 11027 [22] Bruinsma R et al 2000 Phys. Rev. Lett. 85 4393 [23] Conwell E M and Rakhmanova S V 2000 Proc. Natl Acad. Sci. USA 97 4556 [24] Rakhmanova S V and Conwell E M 2001 J. Phys. Chem. 105 2056 [25] Schuster G B 2000 Acc. Chem. Res. 33 253 [26] Henderson P T et al 1999 Proc. Natl Acad. Sci. USA 96 8353 It is plausible that when an electron or a hole is injected into a deformable macromolecule such as DNA, it will induce local distortions of the structure as the latter adjusts to the excess charge and lowers the system energy [27]; in other words a ‘polaronic’ distortion will be formed. [27] Komineas S, Kalosakas G and Bishop A R 2002 Phys. Rev. E 65 061905

  23. 8. Z. G. Yu and X. Song, Phys. Rev. Lett. (2001)86 6018 **9. N. F. Mott and E. A. Davis (1971) Electronic Processes in Non-Crystalline Solids (Oxford: Oxford University Press) p. 216 ** Yu and Song to interpret exp1 by Tran et al proposed variable range hopping (Mott and Davis) + a 1D disordered system - possible small polaron character of the carriers - multiphonon-assisted at high-T Conclusion: T↓ nearest neighbor hopping to variable range hoppingof electrons between localized states T-dependent localization length (due to thermal structural fluctuations) without invoking ionic conduction probability for a hop from an occupied site to a vacant site P ~ exp[- 2αR – W/kBT] R distance between sites α-1 localization length W the energy difference between sites Mott (variable range hopping): competition between the two terms in the exponential Indeed in DNA: two competing mechanisms (unistep superexchange and multistep hopping) For details see my notes.