jet-ftir studies of model peptide systems corey a. rice and martin a. suhm institut für...
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Jet-FTIR Studies of Jet-FTIR Studies of Model Peptide SystemsModel Peptide Systems
Corey A. Rice and Martin A. Suhm
Institut für Physikalische ChemieUniversität Göttingen
Tammannstr. 6D-37077 Göttingen, Germany
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman
OutlineOutline
MotivationMotivation Experimental SetupExperimental Setup Model compoundsModel compounds
Formamide, N-Methylformamide and Formamide, N-Methylformamide and
N-MethylacetamideN-Methylacetamide
Protected GlycineProtected Glycine Conclusions and OutlookConclusions and Outlook AcknowledgementsAcknowledgements
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman
The Peptide BondThe Peptide Bond
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman
NCR
HR
O
MotivationMotivation
Pioneers of Peptide models in the gas phasePioneers of Peptide models in the gas phase Simons, Meijer, Gerhards, Zwier, Pratt, etc.Simons, Meijer, Gerhards, Zwier, Pratt, etc.
The structure of proteins is determined through The structure of proteins is determined through hydrogen bonding motifs (i.e. hydrogen bonding motifs (i.e. -helix, -helix, -sheet -sheet structures, etc.)structures, etc.)
Through N-HThrough N-H......O=C interactionsO=C interactions Secondary, Tertiary and higher-order structures are Secondary, Tertiary and higher-order structures are
extremely hard to determineextremely hard to determine A false Primary structure can lead to a false overall A false Primary structure can lead to a false overall
structure, which leads to many known diseasesstructure, which leads to many known diseases Observe the aggregation of small model systemsObserve the aggregation of small model systems Aggregation patterns can be determinedAggregation patterns can be determined Large aggregates hard to get into the gas phaseLarge aggregates hard to get into the gas phase
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman
Experimental IdeaExperimental Idea
Solvent-free studiesSolvent-free studies Through adiabatic expansion Through adiabatic expansion
conditionsconditions TTRR ~ 5 – 20 K ~ 5 – 20 K molecular collisionsmolecular collisions
molecular interactions (i.e. hydrogen bonds)molecular interactions (i.e. hydrogen bonds)
Direct Absorption Infrared Direct Absorption Infrared SpectroscopySpectroscopy
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman
Experimental SetupExperimental Setup
filet: fine but lengthy600 x 0.2 mm2
substance
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman
New Experimental SetupNew Experimental Setuppoppet-controlled, resistively-heated nozzle
(popcorn-jet)
Sub
stan
ceE
xpa
nsi
on
Magnetic Valve
Check Valves
5 x 1 mm2
h (IR)
2
1 check valve cracking pressure1. 70 mbar2. 680 mbar
175 ms pulse length
p0 = 1.5 – 2.0 bar
pb ~ 10-6 bar
Variable Temp. 298 –
500 K
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman
moderate heatingmoderate heating
NH(a)NH(s)
Free
NH
D
Nozzle
Temp.
328 K
298 K
FormamideNozzle Dim./m
m
5 x 1
600 x 0.2
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman
Model Compounds: N-H stretch Model Compounds: N-H stretch regionregion
Nozzle
Temp.
298 K
318 K
298 K
Nozzle Dim./m
m
600 x 0.2
5 x 1
600 x 0.2
N-Methylformamide
N-Methylacetamide
Formamide
M
MD T(?)
D
DNH(s)
NH(a)
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman
C=O of FormamidesC=O of Formamides
Formamide
N-Methylformamide
Nozzle
Temp.
318 K
328 K
Nozzle Dim./m
m
5 x 1
5 x 1
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman
Acetylglycine ethyl ester Acetylglycine ethyl ester N-H stretchN-H stretch
stick spectrum of Ac-Phe-OMea
MD
a Gerhards, M.; Unterberg, C. PCCP, 2002, 4, 1760-1765.
Nozzle Temp. 363 K
p0 / bar 2.0}
2 x C=O
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman
Acetylglycine ethyl ester Acetylglycine ethyl ester
Amide I
stick spectrum of Ac-Phe-OMeaa Gerhards, M.; Unterberg, C.; Gerlach, A. PCCP, 2002, 4, 5563-5565.
Nozzle Temp. 363 K
p0 / bar 2.0
D
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman
Conclusions and OutlookConclusions and Outlook
New Experimental SetupNew Experimental Setup Model compounds to small protected Model compounds to small protected
peptidepeptide Aggregation patterns are differentAggregation patterns are different
In the future, different protected In the future, different protected peptides without a UV-chromophore peptides without a UV-chromophore in the gas phasein the gas phase High-level High-level ab initioab initio calculations calculations
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman
AcknowledgementsAcknowledgements
Prof. Dr. Martin SuhmProf. Dr. Martin Suhm Everyone in the Suhm GroupEveryone in the Suhm Group GRK 782 (www.pcgg.de) funded GRK 782 (www.pcgg.de) funded
through the DFGthrough the DFG
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman
Thank YOU for your attention!
61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman