Protein « photos » with ultrafast lasers
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Transcript of Protein « photos » with ultrafast lasers
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Protein « photos » with ultrafast lasersProtein « photos » with ultrafast lasers
Goran ZgrablicGoran ZgrablicInstitut de Physique de la Matière CondenséeInstitut de Physique de la Matière Condensée
Université de LausanneUniversité de Lausanne
Summer School of Science, Višnjan Observatory, 27th july 2003
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Long organic molecules
which interact in
biological reactions
Proteins: Nano-machines of living cell
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3D Protein STRUCTURE:
Protein folding still an unresolved problem
…but to know structure is not enough!
Methods:-X-ray diffraction-NMR (Nuclear Magnetic Resonance) -electron microscopy
“If you want to understand function, study structure”(Francis Crick)
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Protein DYNAMICS: the importance of the motion
Molecular interactions:-Hydrophobic-Van der Waals-Electrostatic-Hydrogen bonds
Forces:weak – comparable to thermal motionsMovements: 1 Å (0.1 nm)
Aquaporine in the lipid membrane of the cell
Time window 0.2 ns
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Water and protein: a perfect couple
Interactions with environment:Water is essential to biological activity of proteins
Molecular dynamics simulations byB.L. de Groot and H. Grubmüller: Science 294, 2353-2357 (2001))
AquaporineA protein which selectively
passes the water molecules into the cell (red blood cells, kidney, lung,
brain, eye)
Time window 2 ns
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“If you want to understand function, study structure”(Francis Crick)
Function= sequence of events over time,
characterised by structural modifications“If you want to understand function, study
time-dependent structures”
Time resolution
Spatial resolution
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Conclusion:
Biomolecular structure and dynamics work together to define function
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Question:
What do we need to make a movie of the molecules in chemical reaction?
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[Fe+III Fe+II(CN)6][Fe+II(CN)6]Fe+III
+
A B AB
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400 500 600 700 800
ab
sorp
tio
n
wavelength / nm
INFRAREDUV
SPECTROSCOPY
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The color (absorption) distinguishes reactants
from product
SPECTROSCOPY Measuring absorption in time we see progress of
chemical reaction
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Time resolution 0.1 s
with shutter camera
Cats are very good physicists!
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Question:
What do we need to make a movie of the molecules in chemical reaction?
-> LIGHT PULSE
…but, how short?
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The The fundamentalfundamental time scale in time scale in Condensed Matter, Chemistry Condensed Matter, Chemistry and Biologyand Biology
Speed of sound: Speed of sound: 300 m/s-1000m/s => 0.3-1.0 Å in 100 fs300 m/s-1000m/s => 0.3-1.0 Å in 100 fs
•
1fs = 0.00 000 000 000 000 1s = 10-15 s1fs / 1s <=> 1s / 32 million years!
Time scale of half-oscillations:
H2; e = 4155 cm-1 —> 7.6 fs
I2; e = 120 cm-1 —> 270 fs
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Ultrafast molecular motionUltrafast molecular motion involved in biological functioninvolved in biological function
Vibrations 20 … 500 fs Torsions 200 fs … 5 psElectron transfer 20 fs … 100 psResonance energy transfer 100 fs…100 ps
Protein folding
10-15 10-12 10-9 10-6 10-3 1 sec
Protein Synthesis
Helix motion
Intermol. charge transferP-P interaction
Intra-molecular motion
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Question:
What do we need to make a movie of the molecules in chemical reaction?
-> LIGHT PULSE of few femtoseconds
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Femtosecond laser pulsesFemtosecond laser pulses
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…but, somebody has
to push the poor cat!
Let’s Use some light
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So, we need two fs pulses:
PUMP pulse – photoexcites all the molecules at the same time and starts the chemical reaction
PROBE pulse – measures the absorption change after time we want
t0 = 0 fs
t1 = 100 fst2 = 200 fst3 = 300 fs…
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„ „ Femtosecond photography “Femtosecond photography “
Nobel prize in Chemistry 1999:Prof. A. Zewail
“ Femtochemistry “
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Schémas von SelmaSchémas von Selma Pulsbreite NOPA’sPulsbreite NOPA’s
-80 -60 -40 -20 0 20 40 60 80
0,0
0,2
0,4
0,6
0,8
1,0
1,2Autocorrelation 640nmPulse width 18.5 fs
Sig
nal (
arb.
uni
ts)
Time(ps)time delay [fs]
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distance entre les atomes
éner
gie
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0 1 2 3
1
2
3
delay pump - probe / picoseconds
t = 300 fs
Vibration of an isolated molecule
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Femtosecond light activated Femtosecond light activated processes in biologyprocesses in biology
some examplessome examples
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CHROMOPHORES:CHROMOPHORES:
Molecules that react Molecules that react upon the exposure to upon the exposure to light can be used as light can be used as model systems for the model systems for the study of these ultrafast study of these ultrafast processes processes
Our research focuses on proteins, which can bind CHROMOPHORES (light-sensitive molecules)
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Understand molecular physics behind the function
Photosensory proteins
Vision
Photo-taxis
Plant growth
Phytochrome - induction of flowering, chloroplast development, leaf senescence and leaf abscission.
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Hemoglobin: dissociation/binding of OHemoglobin: dissociation/binding of O22, CO,..., CO,...
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Bacteriorhodopsin: converts light into «food» ATP
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Rhodopsin: Rhodopsin: a photosensory protein in eyea photosensory protein in eye
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From L. Stryer, Biochemistry
Rhodopsin and the retinal moleculeRhodopsin and the retinal molecule
Retinal chromophore
Cis-trans isomerisationNobel 1961: G. Wald, R.Granit, H.K. Hartline
11-cis all-trans
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Femtoseconds and proteins ?Femtoseconds and proteins ?
11-cis all-trans
400 500 600
0.0
0.2
0.4
0.6495 nm
Abs
orpt
ion
(arb
.uni
ts)
Wavelength (nm)400 500 600
0.0
0.2
0.4
0.6548 nm
Abs
orpt
ion
(arb
.uni
ts)
Wavelength (nm)
200 fs
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The protein environment controls The protein environment controls at which bond the chromophore will turnat which bond the chromophore will turn
Response to photo-induced charge transfer on chromophore
Protein = has some charges and they can move around
Light can stretch electron cloud when we excite chromophore
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Amino acid measures Amino acid measures the induced electric field...the induced electric field...
+ -
……by changing its color from by changing its color from blue to greenblue to green
0
aL
0
ret44444444444444
ret44444444444444
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Environment (water) can make a chemical Environment (water) can make a chemical reaction possible, or make it fasterreaction possible, or make it faster
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Dynamic Stokes shift – solvent responseProtonated Schiff base in MeOH
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Methanol12x10
3
10
8
6
4
2
0
inten
sity
(a. u
.)
700650600550500wavelength [nm]
375 fs 450fs 550fs 725fs 1025fs 1625fs 2725fs
Spectrum changes in time Spectrum changes in time -> water is turning around the molecule-> water is turning around the molecule
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Photosynthesis
From http://www.ks.uiuc.edu/Overview/gallery/structure.shtml
Electron transfer in reaction center
Non-radiative energy transfer (Förster)
cytoplasm
periplasm h
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Life is made of…
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Swiss National Science FoundationRoche Research Foundation “Fondation Herbette” LausanneUni Lausanne
In collaboration with
M. Sheves (Weizmann Institute)
E. Landau (U Texas, Galveston)
J. Heberle & G. Büldt (FZ Jülich)
M. Chergui and his groupM. Chergui and his groupIPMC - Uni Lausanne