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Towards a molecular movie: Transient 2D-IR spectroscopy Peter Hamm Physikalisch Chemisches Institut, Universität Zürich. Biosystems are Dynamical. Aquaporin-1 . B.L. de Groot and H. Grubmüller, Science 294, 2353-2357 (2001) http://www.mpibpc.gwdg.de/abteilungen/071/bgroot/gallery.html.

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Towards a molecular movie: Transient 2D-IR spectroscopy

Peter Hamm

Physikalisch Chemisches Institut, Universität Zürich


Biosystems are Dynamical

Aquaporin-1

B.L. de Groot and H. Grubmüller, Science 294, 2353-2357 (2001)

http://www.mpibpc.gwdg.de/abteilungen/071/bgroot/gallery.html


Structure Sensitive Methods

Scattering Methods

(x-ray, electrons, neutrons)

2D-NMR

+ highest structure

resolution power

- works best in crystals

+ works best in solution

+ high structure resolution

power

- intrinsic time resolution

very poor (1-100 ms)

+ intrinsic time resolution

unlimited

Time Resolved

Scattering Methods

2D-IR

+intrinsic time resolution

fast (1 ps)

- structure resolution power

low but non-zero


Coupled Vibrational States

Linear Coupling:

Site Basis

Exciton Basis


Linear Spectroscopy

O

O

C

O

C

N

C

N

C

C

H

H

N

C

H

H

H

H

Frequency

O

H

O

R1

R3

C

C

N

C

C

N

C

N

C

R2

O

H

H

Frequency

Strong coupling,

homogeneous

Weak coupling,

heterogeneous

R2

R3

R1


2D-IR Spectroscopy: Setup

tp=100 fs

Dw=200 cm-1

E=1 µJ

Delay

Spectrometer +

232 Element MCT

Detector Array

Fabry Perot

Filter

Sample


2D-IR Spectroscopy

|2

|2‘

|1

|1‘

|0

|0‘


2D-IR Spectroscopy

|20

|11‘

|02‘

|10

|01‘

|00‘


2D-IR Spectroscopy: Equilibrium

  • Conformation and distribution of conformations

     Ultrafast equilibrium fluctuations

Probe Frequency [cm-1]

Woutersen et al. J. Phys. Chem. B, 104, 11316-11320 (2000)

Woutersen et al., PNAS 98, 11254-11258 (2001)

Woutersen et al. J. Chem. Phys.117, 6833-6840 (2002)



Photocleavable Peptide

?

hn

C. Kolano, K. Gomann, W. Sander, Eur. J. Org. Chem.2004, 20, 4167-4176.


Photocleavable Peptide: IR spectrum

Boc-Cys-Pro-Aib-Cys-OMe





Transient 2D Spectroscopy: Setup

IR Probe

Fabry Perot

Filter

IR Pump

Spectrometer +

232 Element MCT

Detector Array

Delay

UV Switch

Delay

Sample

Flow-Cell


Transient 2D-IR Spectra

3-100 ps

1 ps

t

UVpump

IRpump

IRprobe

3 ps

25 ps

100 ps


Nonequilibrium MD Simulations

1 ns

Equilibrium Simulation (NVT): 120 ns

Bondbreaking:

Remove S-S Bond

Non-Equilibrium Simulation (NVE): 600 ps

  • MD Package: Gromacs; Gromos Force Field 43a1

  • Starting geometry: Based on low-resolution x-ray structure

  • Solvent box: Acetonitrile (1048 molecules)



MD Simulations: Average

6.1 Å

3.0 Å

+s

-s


Transient 2D-IR Spectra

Equilibrium 2D

Transient 2D

100 ps

C. Kolano, Nature 2006 in press


Transient 2D-IR Spectra

Equilibrium 2D

Transient 2D

100 ps


Transient 2D-IR Spectra

Equilibrium 2D

Transient 2D

100 ps



Conclusion

Transient 2D-IR spectroscopy combines picosecond time resolution with microscopic structural information

Transient 2D-IR reveals new insight into

fast structural dynamics of peptides, that cannot be obtained otherwise.

 An ultrafast molecular movie of the 3D-

structure conceivable (in connection with isotope labeling)


Outlook: Isotope Labelling

a-Helix Folding

13C=O

13C=18O

13C=O

13C=18O

hn


Acknowledgement

  • University Zürich University Munich

  • - Dr. Christoph Kolano - Prof. Wolfgang Zinth

  • Dr. Jens Bredenbeck

  • Dr. Jan Helbing University Bochum

  • Mariusz Kozinski - Dr. Christoph Kolano

  • Valentina Cervetto - Prof. Wolfram Sander

  • Harald Bregy

  • Ellen Backus Max Planck Institut, Martinsried

  • Virgiliu Botan - Dr. Christian Renner

  • - Prof. Luis Moroder

  • Max Born Institut, Berlin

  • Dr. Sander Woutersen University of Toronto

  • Prof. Thomas Elsaesser- Prof. Andrew Woolley

  • University FrankfurtFinancial Support

  • Prof. Josef Wachtveitl - Universität Zürich

  • Prof. Gerhards Stock - Swiss Science Foundation

  • - Deutsche Forschungsgemeinschaft


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