infrared multiple photon dissociation (irmpd) spectroscopy of b 7 ions from model acetylated...
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INFRARED MULTIPLE PHOTON DISSOCIATION (IRMPD) SPECTROSCOPY OF
b7 IONS FROM MODEL ACETYLATED PEPTIDES
Ahmet E. Atik and Talat YalcinDepartment of Chemistry, Faculty of Science, Izmir Institute of Technology, Urla-Izmir, Turkey
Oscar Hernandez and Philippe Maître Laboratoire de Chimie Physique, Université Paris Sud, UMR8000 CNRS, Faculté des Sciences,Bât. 350, 91405 Orsay Cedex, France
Ozgur Birer Department of Chemistry, Faculty of Science, Koc University, Istanbul, Turkey
TAC Light Sources (SR&FEL) International Users’ Meeting October 5-7, 2013
Direct absorption measurements and obtaining IR spectra of trapped ions challenging due to their extremly low densities (< 108 cm-3)
IRMPD Spectroscopy of ions overcome this sensitivity problem
Why IRMPD Spectroscopy for Trapped Ions
IRMPD Spectroscopy of Trapped Ions
structural information location of charge (proton) presence (or absence) of chemical moieties symmetry secondary structure of proteins hydrogen bonding interactions
Vibrational spectrum offers:
Infrared Multiple Photon Dissociation (IRMPD) Spectroscopy
trapped ions are irradiated
a photon is absorbed (wavelength of laser =trapped ion’s vibr. mode)
intramolecular vibrational redistribution (IVR)
internal energy of the ion increases fragment by unimolecular dissociation
Nick C. Polfer, Chem. Soc. Rev., 40, 2211-2221, 2011
IRMPD Spectra of mass-selected Ions
Nomenclature of Peptide Fragment Ions
Under low-energy CID conditions, protonated peptides typically fragment via cleavage at amide bonds to give N-terminal b-ions and a-ions and
C-terminal y-ions 1, 2
[1] Roepstorff, P.; Fohlmann, J. Biomed. Mass Spectrom. 1984, 11, 601.[2] Biemann, K. Biomed. Environ. Mass Spectrom. 1988, 16, 99.
b2+ y2
+a2+
7
oxazolone Diketopiperazine
b2 ?
b2 ?
b2 ?
acylium
H+ H+H+
bn+ (n = 2 - 4) ions protonated oxazolone structure 3, 4
[3] Yalcin, T.; Khouw, C., Csizmadia, I. G.; Peterson, M. R.; Harrison, A. G. J. Am. Soc. Mass Spectrom. 1995, 6, 1165.[4] Yalcin, T.; Csizmadia, I. G.; Peterson, M. R.; Harrison, A. G. J. Am. Soc. Mass Spectrom. 1996, 7, 233.
- H2O
via nucleophilic attack from a backbone carbonyl oxygen to a carbonyl carbon
An Oxazolone Structure
b2
b3
V.H. Wysocki et al., JACS, 130, 17644-17645, 2008
B. Paizs, et al., JACS, 129, 5887- 5897, 2007
Macrocyclization of b Ions
YAGFLVoxa
AGFLVYoxa
GFLVYAoxa
FLVYAGoxa
LVYAGFoxa
VYAGFLoxa
internal amino acid eliminations (non-direct sequence b ions) were appeared
Macrocyclization of b Ions
head-to-tail cyclization 5-7
YAGFLVoxa
AGFLVYoxa
GFLVYAoxa
FLVYAGoxa
LVYAGFoxa
VYAGFLoxa
Ring opening
[5] Harrison, A. G.; Young, A. B.; Bleiholder, C.; Suhai, S.; Paizs, B. J. Am. Chem. Soc. 2006, 128,10364. [6] Jia, C.; Qi, W.; He, Z. J. Am. Soc. Mass Spectrom. 2007, 18, 663. [7] Bleiholder, C.; Osburn, S.; Williams, T. D.; Suhai, S.; Van Stipdonk, M.; Harrison, A. G.; Paizs, B. J. Am. Chem. Soc. 130, 2008, 17774.
YAGFLVoxa
bn+ ions (n= 5, 6, 7 …)
M. Tirado and N. C. Polfer, Angew. Chem. Ed., 51, 6436-6438, 2012
N-terminal acetylation blocks the cyclization reaction and eliminates non-direct sequence fragment ions 7, 8
Macrocyclization of b Ions
[7] Bleiholder, C.; Osburn, S.; Williams, T. D.; Suhai, S.; Van Stipdonk, M.; Harrison, A. G.; Paizs, B. J. Am. Chem. Soc. 2008, 130, 17774.[8] Harrison, A. G. J. Am. Soc. Mass Spectrom. 2009, 20, 2248.
M. Tirado and N. C. Polfer, Angew. Chem. Ed., 51, 6436-6438, 2012
Side-to-Tail Macrocyclization of b Ions
Ac-KYAGFLVoxa
IRMPD SPECTROSCOPY OF b7 IONS FROM MODEL ACETYLATED
PEPTIDESAim : to differentiate the macrocyclic structures of b7 ions that are formed
either by “head-to-tail” or “side-to-tail” pathway
to form a regular macrocyclic structure (head-to-tail cyclization), N-terminal amine group must attack to the oxazolone’s carbonyl carbon
the lysine side chain amine group may also attack to form macrocyclic structure in N-terminal acetylated peptides (side-to-tail cyclization)
IRMPD SPECTROSCOPY OF b7 IONS FROM MODEL ACETYLATED
PEPTIDESComparison of IRMPD spectra of b7 ions derived from :
KYAGFLV-NH2 (no acetylation),
KAcYAGFLVG (lysine side-chain is acetylated, ε-amine),
Ac-KYAGFLVG (N-terminal is acetylated, α-amine)
characteristic macrocyclic absorption bands over 1000-2000 cm-1 range???
As a control experiment, Ac-KAcYAGFLVG (doubly acetylated) peptide was
used for obtaining IRMPD spectrum which needs to contain a characteristic band over 1800 cm-1 due to the N-protonated oxazolone structure
Experimental
KYAGFLV-NH2 : no acetylation KAcYAGFLVG : side-chain is acetylated Ac-KYAGFLVG : N-terminal is acetylated Ac-KAcYAGFLVG : both N-terminal and side-chain are acetylated
Y : Tyrosine A : Alanine G : Glycine
• the synthetic model peptides were obtained from GL Biochem Ltd. (Shanghai, China)
• dissolved in a MeOH to give a conc. of 10−4 M
F : Phenylalanine L : Leucine V : Valine
K : Lysine Ac : Acetyl Group
Experimental For the FEL experiments: IRMPD spectroscopy experiments were performed
at the Centre Laser Infrarouge d’Orsay (CLIO) FEL facility at the University of Paris-Sud XI in Orsay, France
FT-ICR MS with a 7 Tesla magnet (Apex Qe, Bruker Daltonics; Billerica, MA, USA)
Paul-type ion-trap (QIT) MS (Esquire 3000+, Bruker Daltonics; Bremen, Germany)
For the mass spectra and breakdown graphs:
LTQ XL linear ion-trap MS (Thermo Finnigan, San Jose, CA, USA) equipped with an ESI source was used
Q-TRAP, Applied Biosystems / MDS Sciex, Concord, Canada) equipped with a turbo ion spray source
Centre Laser Infrarouge d’Orsay (CLIO)
Figure 2. Layout of the CLIO FEL (reprinted from http://clio.lcp.u-psud.fr/)
Centre Laser Infrarouge d’Orsay (CLIO)
Energy : 8 to 50 MeV
Peak current : 100 A
Macro-pulse : length 10 μs, repetition rate: 6.25-25 Hz
Micro-pulse : length 10 ps FWHM, pulse spacing 16 ns
Emittance (rms) : 40 pi mm mrad
Spectral range : 3 to 150 microns (for different e- energies)
Max. average power : 1 W @ 16ns/25Hz
Max. peak power : 100 MW in 1ps
Laser pulse length : 0.5 to 6 ps (adjustable)
Table 1. Main characteristics of the CLIO facility
ResultsComparison of “head-to-tail” and “side-to-tail” Macrocyclization Chemistry of b7 Ions
KYAGFLVoxa
Scheme 2
Results
Scheme 3
Comparison of “head-to-tail” and “side-to-tail” Macrocyclization Chemistry of b7 Ions
Ac-KYAGFLVoxaK(Ac)YAGFLVoxa
ResultsComparison of “head-to-tail” and “side-to-tail” Macrocyclization Chemistry of b7 Ions
non-direct sequence b ions (internal amino acid losses) were appeared with different relative
intensities in each mass spectra
to clarify the gas-phase macrocyclic structure of each b7 ion, the IRMPD spectra were
recorded in the mid-IR range 1000-2000 cm-1
Figure 3
ResultsComparison of “head-to-tail” and “side-to-tail” Macrocyclization Chemistry of b7 Ions
two main experimental bands
~1510 cm-1 ~1675 cm-1
N-H bending (amide II)
C=O stretching (amide I)
No bands over 1800-1900 cm-1 absence of oxazolone structure
N-terminal amine (α-amine) is more nucleophilic than lysine side-chain amine (ε-amine) group
Figure 4
ResultsComparison of “head-to-tail” and “side-to-tail” Macrocyclization Chemistry of b7 Ions
1614 cm-1
A
A
B
B
CC
Figure 5
ResultsComparison of “head-to-tail” and “side-to-tail” Macrocyclization Chemistry of b7 Ions
the breakdwon graphs were constructed for internal amino acids eliminations from b7 ions
eliminations are ~ 4 % eliminations are ~ 6 %
Figure 6
ResultsAc-K(Ac)YAGFLVG (Doubly Acetylated Model Octapeptide)
no macrocyclization
An oxazolone band needs to be appeared in the IRMPD
spectrum of b7
Figure 7
only direct sequence b ions
Results
Figure 8
ResultsAc-K(Ac)YAGFLVG (Doubly Acetylated Model Octapeptide)
breakdown graph of b7 ion was constructed in order to see the cascade b ion series
b7 b6 b5 b4 b3 b2 b1
Figure 9
Figure 10
ResultsAc-K(Ac)YAGFLVG (Doubly Acetylated Model Octapeptide)
The b1 ion is dissociated to form product ions at m/z 185, 171, 126 and 84 either consecutive or competitive pathway??
Figure 11
ResultsAc-K(Ac)YAGFLVG (Doubly Acetylated Model Octapeptide)
ResultsAc-K(Ac)YAGFLVG (Doubly Acetylated Model Octapeptide)
m/z 185 and 126 have the same profile (competitive fragmentation pathway)
Figure 12
Scheme 5
Conclusion 1
small band at 1614 cm-1 might be a signature for the “side-to-tail” cyclization of b7 ion of Ac-KYAGFLVG
N-terminal amine (α-amine) is more nucleophilic than lysine side-chain amine (ε-amine) group (confirmed by IRMPD
stable b1 ion (oxazolone) in the fragmentation of b7 ion of Ac-K(Ac)YAGFLVG (confirmed by both its IRMPD and mass spectrum individually)
Conclusion 2
protein-peptide non-covalent complex
Chirality recognition
structural characterization
differentiate isomeric mixture of peptides/proteins
structure of neutral elimination in gas phase can be determined
Mass Spectrometry systems:
•FT-ICR •Ion Trap
THANKS FOR YOUR ATTENTION …
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