REMPI and Double Resonance Spectroscopy of L -β-Homotryptophan in Gas Phase Hae Jun Jung, Jung Jin...
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Transcript of REMPI and Double Resonance Spectroscopy of L -β-Homotryptophan in Gas Phase Hae Jun Jung, Jung Jin...
REMPI and Double Resonance Spectroscopy of
L-β-Homotryptophan in Gas Phase
Hae Jun Jung, Jung Jin Kim, and Hyuk KANGAjou University, Suwon 443-749, Korea
69th International Symposium on Molecular Spectroscopy
Submicroscopic Histology
• Section the active part• Use a natural chromophore or stain it• Freeze it• Illuminate it with laser in a vacuum chamber• Directly observe the active conformations• Directly observe the active molecular interaction
How to Distinguish Conformers w/ UV
Conformer A
Conformer B
S0
S1
hνA0-0 hνB0-0hνA0-0 < hνB0-0
0.319 kcal mol-1 (B3LYP/6-31G**)
cis-meta-aminophenol
trans-meta-aminophenol
S1
S0
hνburn
c-3AP
t-3AP
UV-UV Double ResonanceUV-UV Hole Burning
hνprobe
Mass-Resolved Conformer-Specific UV Spectrum
L-β-homotryptophan
L-tryptophan
E. E. Baquero, W. H. James, III, S. H. Choi, S. H. Gellman, and T. S. Zwier, J. Am. Chem. Soc., 130, 4784 (2008).
more flexible or easier to fold?
β-Amino acids
L. C. Snoek, R. T. Kroemer, M. R. Hockridge and J. P. Simons, Phys. Chem. Chem. Phys., 3, 1819 (2001).
Conformers of tryptophan
Experimental and Computational
• Thermal oven / laser desorption• Supersonic expansion• Frequency doubled pulsed dye laser• Resonance-Enhanced
Multiphoton Ionization(REMPI)
• TOF MS, MCP, DSO, PC
• Conformational search – Macromodel with Amber force field
• Geometry optimization – Gaussian09 at M05-2X/6-31G**
LinearTOF
MCP
DiffusionPump
DiffusionPump
TurboPump
IG
NY-61 Nd:YAGLaser (532nm)
ND-60 TunableDye Laser Autotracker(BBO)
PVSkimmer
SC
DM
34800 34900 35000 35100 35200
Sig
na
l (A
.U)
Wavenumber (cm-1)
REMPI spectrum of laser-desorbed Trp
T. R. Rizzo, Y. D. Park, L. A. Peteanu, and D. H. Levy, J. Chem. Phys. 84, 2534 (1986).
Levy’s group
Ours
REMPI spectrum of Trp and Trp-HCl
R-NH3+ + Cl-
R-NH2 + HCl
R-NH3+·Cl-
34860 34880 34900 34920
Sig
nal (
A.U
.)
Wavenumber (cm-1)
Trp Trp HCl
22 24 26 28 30 32 34-0.18
-0.16
-0.14
-0.12
-0.10
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
Mas
s S
igna
l (m
V)
Flight time (us)
Trp Trp HCl
34600 34700 34800 34900 35000 35100 35200 35300 35400
Ion S
ignal (A
.U.)
Wavenumber (cm-1)
34750 34800 34850 34900 34950 35000 35050
Ion
Sig
nal (
A.U
.)
Wavenumber (cm-1)
REMPI spectrum of L-β-homotryptophan*
*HCl salt
34600 34700 34800 34900 35000 35100 35200 35300 35400
34600 34700 34800 34900 35000 35100 35200 35300 35400
Ion S
ignal (A
.U.)
Wavenumber (cm-1)
L-β-Homotryptophan and L-tryptophan
*HCl salt
UV-UV HB spectra of L-β-hTrp
34800 34850 34900 34950 35000 35050
Sig
nal (
A.U
.)
Wavenumber / cm-1
H.B. at 34980 cm-1
H.B. at 34950 cm-1
REMPI
*
*
0
1
2
3
4
5
6
Re
lativ
e e
ne
rgy
(kJ/
mo
l)
0.0 kJ/mol
3.66 kJ/mol
0.86 kJ/mol
3.64 kJ/mol(23% at 300 K)
4.76 kJ/mol
0.22 kJ/mol 0.28 kJ/mol
2.10 kJ/mol
5.66 kJ/mol(10% at 300K)
2.59 kJ/mol
1.82 kJ/mol(48% at 300 K)
2.61 kJ/mol2.80 kJ/mol
4.36 kJ/mol
5.16 kJ/mol
Stable conformers of L-β-homotryptophan
M05-2X/6-31G**
Issues
• Short progression– Lower Franck-Condon activity than Trp?– Faster non-radiative process?
• Less conformers observed– Signal intensity ≠ population– Low barriers between conformers
• Conformer-specific non-radiative process?
L-β-homotryptophanL-tryptophan
Conformer-specific IC
M. Mališ, Y. Loquais, E. Gloaguen, C. Jouvet, V. Brenner, M. Mons, I. Ljubić and N. Došlić, Phys. Chem. Chem. Phys. 16, 2285 (2014).
Published in: Momir Mališ; Yohan Loquais; Eric Gloaguen; Himansu S. Biswal; François Piuzzi; Benjamin Tardivel; Valérie Brenner; Michel Broquier; Christophe Jouvet; Michel Mons; Nađa Došlić; Ivan Ljubić; J. Am. Chem. Soc. 2012, 134, 20340-20351.DOI: 10.1021/ja3054942Copyright © 2012 American Chemical Society
Acknowledgements
• Hae Jun Jung• Jung Jin Kim