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Functional DNA architectures: Photoinduced dnatec09/presentations/2009_05... Part I. Nucleoside models for electron transfer in DNA Summary H O O N N HO OH O Py-dU hν e-k ET : 4.7

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Text of Functional DNA architectures: Photoinduced dnatec09/presentations/2009_05... Part I. Nucleoside...

  • Functional DNA architectures: Photoinduced electron transfer and

    switchable optical properties

    Hans-Achim Wagenknecht

  • Part I+II: Photoinduced charge transfer in DNA

  • Part I+II: Photoinduced charge transfer in DNA

    Hole transfer vs. electron transfer

    H.-A. Wagenknecht (Ed.), Charge Transfer in DNA, Wiley-VCH, 2005, 1. Angew. Chem. Int. Ed. 2003, 42, 2454; Curr. Org. Chem. 2004, 8, 251; Nat. Prod. Rep. 2006, 23, 973.

    Proposed to be more suitable for nano/biotechnology: • faster • more efficiently • less (or no) damage

    Oxidative hole transfer

    Reductive (excess) electron transfer

    X X Do

    X X X

    X X X Ac

    X X X X

    X X

    X X

    * +

    HOMO

    LUMO

    Do* B

    ET

    Hole injection

    X X Do

    X X X

    X X X Ac

    X X X X

    X X

    X X

    * -

    HOMO

    LUMO

    Do* B

    ET

    Electron injection

    • Superexchange • Hopping

  • O O

    N

    N

    O

    O

    H

    S

    N

    O

    O

    O N

    N

    O

    O

    H

    H3C

    O

    O

    O

    -2.3 V

    -2.0 V

    -1.8 V

    -2.15 V

    -1.80 V

    -1.10 V

    C, T

    C(H), T(H) ?

    - -

    H

    O

    O N

    H2N NH2

    N+

    -0.5 V

    H O

    O

    N

    NO

    O

    O

    N H

    OO -

    -2.1 V

    H

    O

    O N

    N N CH3

    + -1.0 V

    Part I+II: Photoinduced electron transfer in DNA

    Excited state potentials of electron donors

    H.-A. Wagenknecht (Ed.), Charge Transfer in DNA, Wiley-VCH, 2005, 1. Angew. Chem. Int. Ed. 2003, 42, 2454; Curr. Org. Chem. 2004, 8, 251; Nat. Prod. Rep. 2006, 23, 973.

    Electron hopping

    Electron tunneling

  • Part I. Nucleoside models for electron transfer in DNA

    Summary

    H

    O

    O

    N

    N HO

    OH

    O

    Py-dU

    hν e-

    kET : 4.7 ps pKa = 5.5

    O

    N

    N HO

    OH

    O

    Py-dC

    hν e-

    NH2

    kET : 40 ps pKa > 12

    Nucleoside model studies:

    • T is reduced faster

    • exhibits strong basicity•-dC

    Implication for DNA:

    is the major electron carrierdT -•

    Nicole Amann, Elke Mayer-Enthart In collaboration with Torsten Fiebig, Boston

    Synlett 2002, 687. Angew. Chem. Int. Ed. 2002, 41, 2978. Chem. Commun. 2003, 1878 . Synthesis 2003, 2335.

    ChemPhysChem 2004, 5, 706 Chem. Phys. Lett. 2005, 409, 277.

    Redox potentials:

    C and T as electron carriers in DNA

  • Part I. Reductive electron transfer in DNA

    Angew. Chem. Int. Ed. 2003, 42, 2454.

    Chem. Eur. J. 2005, 22, 1871.

    Angew. Chem. Int. Ed. 2005, 44, 1636.

    Proc. Natl. Acad. Sci. USA 2006, 103, 10192

    DNA studies

    Electron injection studies

    Chem. Eur. J. 2002, 8, 4877-4883.

    Eur. J. Org. Chem. 2003, 2498.

    Angew. Chem. Int. Ed. 2004, 43, 1845.

    -• 3' 5'

    5'

    3'

    X

    X A A

    dU T

    R

    X

    X

    X

    X

    X

    X

    C

    XG

    X

  • Part I. Reductive electron transfer in DNA

    Angew. Chem. Int. Ed. 2003, 42, 2454.

    Chem. Eur. J. 2005, 22, 1871.

    Angew. Chem. Int. Ed. 2005, 44, 1636.

    Proc. Natl. Acad. Sci. USA 2006, 103, 10192

    DNA studies

    Chemical electron acceptor

    X

    X X

    X

    dU XBr •- Br-

    X

    X X

    X

    dU X

    Strand break

    (HPLC analysis)

    ET

    Br-dU

    Br

    N

    N

    O

    O

    H

    O

    HO

    HO

  • Part I. Reductive electron transfer in pyrene-modified DNA

    Time-resolved spectroscopy

    Chem. Eur. J. 2002, 8, 4877. Angew. Chem. Int. Ed. 2005, 44, 1636.

    150 ps

    1500 ps

    Time-resolved transient absorption spectra

    0 500 1000 1500 0.0

    0.5

    1.0

    0 5 10 0.0

    0.5

    1.0

    Δ A

    485 nm 364 nm

    time (ps)

    dU

    Py

    A dU

    Br

    T T T

    * dU

    Py

    A dU Br

    T T T

    - +

    DNA-ET

    Fluorescence Recombination

    - Br

    Strand Cleavage

    Electron injection

    2 ps-1 dU

    Py

    A dU Br

    T T T

    - +several

    100 ps-1

    -

    Py-dU

    N

    N

    O

    O

    H

    HO

    HO

    O

    Nicole Amann Elke Mayer-Enthart, Peter Kaden

    A A A A

  • Part I. Reductive electron transfer in pyrene-modified DNA

    Influence of DNA dynamics

    Chem. Eur. J. 2002, 8, 4877. Angew. Chem. Int. Ed. 2005, 44, 1636.

    dU

    Py

    A dU

    Br

    T T T

    * dU

    Py

    A dU Br

    T T T

    - +

    DNA-ET

    Fluorescence Recombination

    - Br

    Strand Cleavage

    Electron injection

    2 ps-1 dU

    Py

    A dU Br

    T T T

    - +several

    100 ps-1

    -

    Nicole Amann Elke Mayer-Enthart, Peter Kaden

    • Electron injection is independent of conformational flexibility of DNA

    • ET occurs on a manifold of time constants due to DNA base dynamics

    Conformational contribution of the DNA („Conformational gating“)

    A A A A A A

  • Part I. Reductive electron transfer in phenothiazine-modified DNA

    Chemical experiments

    Chem. Eur. J. 2005, 11, 1871.

    3C

    2C

    1C

    3T

    2T

    1T

    A dU C

    T A G

    Ptz

    C

    G

    C

    G

    TdU

    A A

    Br

    5'3'

    3'5'

    -•

    A dU C

    T A G

    Ptz

    C

    Br

    AA

    dU T

    G 5'3'

    3'5'

    •-

    5' 3'

    3' 5'

    TA dU C dU

    T A G A A

    Ptz Br•-

    •- 5' 3'

    3' 5'

    A dU T

    T A A

    Ptz

    T

    A

    T

    A

    TdU

    A A

    Br

    -• 5' 3'

    3' 5'

    A dU T

    T A A

    Ptz

    T

    Br

    AA

    dU T

    A

    -• TA dU T dU

    T A A A A

    Ptz Br

    5'3'

    3'5'

    DNA base sequence and distance dependence

    0 10 20 30 40 50 60

    0

    20

    40

    60

    80

    100

    2C 3C

    1C 3T

    1T

    Pt z-

    D N

    A (%

    )

    Irradiation time (min)

    2T

    Clemens Wagner

  • Part I: Reductive electron transfer in DNA

    Mechanism of electron hopping

    Clemens Wagner

    PCETNo PCET

    • Each base pair can participate • Question of long range ET in G-C rich DNA?

    Chem. Eur. J. 2005, 11, 1871.

    dU

    dU

    T

    Pz

    Br

    - T

    T

    A A

    A A

    A

    dU

    dU

    T

    Pz

    Br

    - T

    T

    A A

    A A

    A

    (H) (-H)

    Efficient strand degradation

    dU

    dU

    C

    Pz

    Br

    - C

    C

    A G

    G G

    A

    -(-H)(H)

    dU

    dU

    C

    Pz

    Br

    C

    C

    A G

    G G

    A

    Less efficient strand degradation

  • Part I. Reductive electron transfer in phenothiazine-modified DNA

    Directionality

    3T

    A dU C

    T A G

    Ptz

    C

    Br

    AA

    dU T

    G 5'3'

    3'5'

    •- •- 5' 3'

    3' 5'

    A dU T

    T A A

    Ptz

    T

    A

    T

    A

    TdU

    A A

    Br

    Clemens Wagner

    5‘ 3‘

    3‘ 5‘

    2C

    0 10 20 30 40 50 60

    0.0

    0.2

    0.4

    0.6

    0.8

    1.0

    3T 2C

    St ra

    nd c

    le av

    ag e

    Time (min)

    3T

    2C

  • Part I. Reductive electron transfer in M-DNA

    Thio-dU-Ag(I) base pairs

    Janez Barbaric Based on metallated base pair by Simone Peters in the group of Elmar Weinhold, Aachen

  • Photochemistry of pyrene-modified DNA bases

    (Py•+ dU•-)*

    H

    O

    O

    N

    N HO

    OH

    O

    X = Py-dU

    1

    Eur. J. Org. Chem. 2008, 64. Nicole Amann Claudia Wanninger-Weiß

    LUMO

    Part I. Pyrene as an electron donor

    Py*-dU

    H

    O

    O

    N

    N HO

    OH

    O

    X = Py'dU

    2

  • Part I: Electron donor placement

    Functionalization of DNA

    H.-A. Wagenknecht (Ed.), Charge Transfer in DNA, Wiley-VCH, 2005, 1. Angew. Chem. Int. Ed. 2003, 42, 2454; Curr. Org. Chem. 2004, 8, 251; Nat. Prod. Rep. 2006, 23, 973.

    DNA base substitutionDNA base modification

  • Part I. Electron donor placement

    DNA Base substitution vs. base modification: Phenothiazine

    Clemens WagnerOrg. Biomol. Chem. 2008, 6, 48.

    DNA base substitution DNA base modification

    O N H

    N

    S

    O

    DNA

    DNA

    H

    O

    O

    N

    NO

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