Title: MSMS Spectral Interpretation Linda Breci Chemistry Mass Spectrometry Facility University of Arizona
1MS/MS Spectral InterpretationLinda
BreciChemistry Mass Spectrometry
FacilityUniversity of Arizona MS Summer
Workshop
2MS/MS Spectral Interpretationsmall molecule
structureArpad SomogyiChemistry Mass
Spectrometry FacilityUniversity of Arizona MS
Summer Workshop
3Session Overview
- Ways to approach predicting fragment ion
formation - Fragmentation examples
- Peptides
- Fragmentation mechanism
- Sequence a peptide
- Flavonoids
- Fatty Acids
- Oligonucleotides
4MS/MS Fragmentation
- Few libraries, little software available for data
analysis - Why?
5We need useful information from MS/MS spectra
- Few libraries, little software available for data
analysis - Why?
For MS/MS you have at least one of each of these
- Analyze
- Q
- Q-trap
- linear-trap
- B sectors
- E sectors
- FTICR
- TOF
- Activate
- CID
- SID
- SORI
- IRMPD
- ECD
- BIRD
- Ionize
- EI
- CI
- ESI
- NSI
- MALDI
- FAB
6You put them together like this
ESI-CID-Q-trap ESI-SORI-FTICR
FAB-EBSector-SID-TOF NSI-CID-Q-trap
MALDI-TOF-CID-TOF NSI-Linear-trap-CID-FTICR
NSI-Q-trap-SID-TOF EI-CID-Q-trap
ESI-IRMPD-FTICR ESI-Q-CID-Q
MALDI-TOF-CID-TOF NSI-BIRD-FTICR
ESI-EBSector-CID-EBSector and onand on
7You put them together like this
ESI-CID-Q-trap ESI-SORI-FTICR
FAB-EBSector-SID-TOF NSI-CID-Q-trap
MALDI-TOF-CID-TOF NSI-Linear-trap-CID-FTICR
NSI-Q-trap-SID-TOF EI-CID-Q-trap
ESI-IRMPD-FTICR ESI-Q-CID-Q
MALDI-TOF-CID-TOF NSI-BIRD-FTICR
ESI-EBSector-CID-EBSector and onand on
And you buy them from different manufacturers
- Different source designs
- Example ESI capillary temperature
- Different analyzer designs
- Example Gas pressure, length of ion path (D
timeframe)
8How ions will fragment must be considered from
fundamentals (rather than rules)
- Ways to approach predicting MS/MS fragment
formation - Literature
- Study methods and IDd spectra for your ion class
- Likely sites of protonation (or deprotonation)
- Find proton affinities or acid strengths
- Mobility of protons
- Consider the likelihood of multiple cleavage
sites - Consider multiple gas-phase configurations
- Likely leaving groups
9Types of ions formed
- EI (hard ionization)
- M Radical ion
- A lot of fragmentation occurs upon ionization
- CI, FAB, ESI, APCI, MALDI (soft ionization)
- MH Protonated ion
- M-H- Deprotonated ion
- MNa and other metal cations
10EI is not an MS/MS method
- Discussed Day 4
- Libraries of EI spectra are useful
- NIST/EPA/NIH Mass Spectral Library with Search
http//webbook.nist.gov/chemistry/ - Libraries are not always helpful, tutorials
available - http//www.chem.arizona.edu/massspec/
112 Categories of fragments from protonated or
deprotonated molecules (CI, FAB, ESI, APCI,
MALDI)
- Charge Remote
- Fragmentation reactions uninfluenced by charge
- High energy process
- Charge remote references provided
- Charge Directed
- Bond cleavage occurs with involvement of charge
- Low energy
- Most informative for many molecules
12How ions will fragment must be considered from
fundamentals (rather than rules)
- Literature
- Study methods and IDd spectra for your ion class
- Likely sites of protonation (or deprotonation)
- Find proton affinities or acid strengths
- Mobility of protons
- Consider the likelihood of multiple cleavage
sites - Consider multiple gas-phase configurations
- Likely leaving groups
13How ions will fragment must be considered from
fundamentals (rather than rules)
- Literature
- Study methods and IDd spectra for your ion class
- Likely sites of protonation (or deprotonation)
- Find proton affinities or acid strengths
- Mobility of protons
- Consider the likelihood of multiple cleavage
sites - Consider multiple gas-phase configurations
- Likely leaving groups
14Fragmentation is a multi-step process
Step 1 Create Ions (add 1 or more protons)
ELECTROSPRAY
15Fragmentation is a multi-step process
Step 1 Create Ions (add 1 or more protons)
ELECTROSPRAY
Step 2 Add energy (activation)
SID
CID
16Fragmentation is a multi-step process
Step 3 Charge Directed Cleavage
Neutral Fragment ion
What are the likely sites of proton location?
17Model possible sites of proton location(or loss
of H) in Serine
M H ? MH DHrxn -PA (M) M ? M
- H- H DHrxn DHacid (M)
18Model possible sites of proton location(or loss
of H) in Serine
Model with CH3NH2 (methyl amine)
M H ? MH DHrxn -PA (M) M ? M
- H- H DHrxn DHacid (M)
19Model possible sites of proton location(or loss
of H) in Serine
Model with CH3NH2 (methyl amine)
M H ? MH DHrxn -PA (M) M ? M
- H- H DHrxn DHacid (M)
Ref NIST
20Model possible sites of proton location(or loss
of H) in Serine
Model with CH3COOH (acetic acid)
Model with CH3NH2 (methyl amine)
M H ? MH DHrxn -PA (M) M ? M
- H- H DHrxn DHacid (M)
Ref NIST
21Model possible sites of proton location(or loss
of H) in Serine
Model with CH3COOH (acetic acid)
Model with CH3NH2 (methyl amine)
Model with CH3OH (methanol)
M H ? MH DHrxn -PA (M) M ? M
- H- H DHrxn DHacid (M)
Ref NIST
22Model possible sites of proton location(or loss
of H) in Serine
Model with CH3COOH (acetic acid)
Model with CH3NH2 (methyl amine)
Model with CH3OH (methanol)
Sites of Likely protonation NH2 gt COOH gt
OH deprotonation COOH gt OH gt NH2
M H ? MH DHrxn -PA (M) M ? M
- H- H DHrxn DHacid (M)
Ref NIST
23How ions will fragment must be considered from
fundamentals (rather than rules)
- Literature
- Study methods and IDd spectra for your ion class
- Likely sites of protonation (or deprotonation)
- Find proton affinities or acid strengths
- Mobility of protons
- Consider the likelihood of multiple cleavage
sites - Consider multiple gas-phase configurations
- Likely leaving groups
24Proton mobility
- Intramolecular proton transfer influences
- number of site-directed fragmentations
- amount of energy required for fragmentation
- Intramolecular proton transfer affected by
- site basicity
- gas-phase configuration
- Examples that follow
- Spectra of increasingly basic peptides
- Overview chart demonstrating proton mobility (or
lack of) - Spectra of peptide conformers
25Compare Gas Phase Basicity Arg (R) 240.6
kcal/mol Lys (K) 227.3 kcal/mol His
(H) 227.3 kcal/mol
50 eV (SID)
40 eV (SID)
40 eV (SID)
Ref Gu, 1999
26Pairwise bond cleavage between amino acids
(Xxx-Zzz)
27Peptides with more basic Arg (R) vs. Lys (K)
.............R 1
.............K
28Prediction based on model peptides Selective
Cleavage at Asp-Xxx will depend on number of
Mobile Protons
Huang, Wysocki, Tabb, Yates Int. J. Mass
Spectrom. 219, (1), 233-244, 2002
29Peptides with basic Arg (R) 1 proton vs. 2
protons 1 .............R
2
30Gas-phase conformation influences MS-MS spectra
observed
Ala-Ala-Pro-Ala-Ala Most Natural occurring amino
acids have L configuration at the chiral center
(stereospecific biosynthesis)
31Calculated structure of AAPAA HMany sites
of possible interaction
No solvent in the gas phase!
32Gas-phase confirmation can influence MS-MS
spectra observedPeptides containing proline
stereoisomers fragment differently
All L-amino acids except central residue AVDPLG
All L-amino acids
33Gas-phase confirmation can influence MS-MS
spectra observedPeptides containing proline
stereoisomers fragment differently
All L-amino acids except central residue AVDPLG
All L-amino acids
34Gas-phase confirmation can influence MS-MS
spectra observedPeptides containing proline
stereoisomers fragment differently
All L-amino acids except central residue AVDPLG
All L-amino acids
35Statistical analysis of cleavage at the Xxx-Pro
bond
Breci, Tabb, Yates, Wysocki, (2003)
Analytical Chem. 751963-1971
36Statistical analysis of cleavage at the Xxx-Pro
bond
Asp, His Selective cleavage residues Val, Ile,
Leu Bulky aliphatic side chains
Breci, Tabb, Yates, Wysocki, (2003)
Analytical Chem. 751963-1971
37How ions will fragment must be considered from
fundamentals (rather than rules)
- Literature
- Study methods and IDd spectra for your ion class
- Likely sites of protonation (or deprotonation)
- Find proton affinities or acid strengths
- Mobility of protons
- Consider the likelihood of multiple cleavage
sites - Consider multiple gas-phase configurations
- Likely leaving groups
38Likely Leaving Groups
- Bond cleavage is dependent on various factors
including - Leaving Groups
- Neighboring group participation reactions
- Intermediates (ion-neutral complex)
- For MH ions the leaving group is a neutral
- lower methyl cation affinity is one measure of
likelihood - Compilations available in the literature
- Related to proton affinity
39Ref Bartmess, 1989
(kcal/mol)
40Proton Affinity vs. Methyl Cation Affinity
Ref Bartmess, 1989
41Some fragmentation studies basics
- Few examples from literature
- Cannot talk about all classes of compounds
- These examples suggest problem solving approaches
- Examples
- Peptides
- Fragmentation mechanism
- Sequence a peptide
- Flavonoids
- Fatty Acids
- Oligonucleotides
42Peptides
- Product ion spectra contain many types of
fragment ions - charge directed
- charge remote
- internal fragments
- immonium ions
- Important for sequencing
- amino acid determined from D mass between peaks
in spectrum - y ions series
- b ions series
- immonium ions (identify amino acids in the
peptide) - a ions (confirm b ion after a loss of CO, 28
amu) - Presented here
- peptide fragment ions
- a mechanism for fragment ion formation
- a peptide to sequence
43Peptide fragment ions
c2
Peptide bond fragment ions
b2
a2
z2
y2
x2
Internal immonium ion
Amino acid immonium ion
44Protonation occurs at amide oxygen or nitrogen
Ref Yalcin, 1996
45Protonation occurs at amide oxygen or nitrogen
Ref Wysocki, 2000
46A mechanism of peptide fragmentation
(1) D positive charge
(2) Nucleophilic attack
Ref Wysocki, 2000
47A mechanism of peptide fragmentation
(1) D positive charge
(2) Nucleophilic attack
(3) cyclic intermediate
Ref Wysocki, 2000
48A logical mechanism of peptide fragmentation
(3) cyclic intermediate
(4) Rearrangement
Ref Wysocki, 2000
49A logical mechanism of peptide fragmentation
b oxazolone ion
neutral
Ref Wysocki, 2000
50A logical mechanism of peptide fragmentation
oxazolone neutral (or other structure)
y ion
Ref Wysocki, 2000
51Peptide fragment ions
c2
Peptide bond fragment ions
b2
a2
z2
y2
x2
Internal immonium ion
Amino acid immonium ion
52Peptide Sequencing
71 u.
115 u.
Ala
Asp
53LEARNING CHECKPeptide Sequencing Exercise
54Ion Current over 60 min
MS/MS
MS
55Peptide precursor ions observed by MS
calculation of MH 571.2 m/z measured x
2 1,142.4 M2H - 1.0 1,141.4 MH
M 2H2 m/z 571.2
MH m/z 1141.3
56895.25
MS-MS of 571.2
57Peptide Sequencing
71 u.
115 u.
Ala
Asp
58895.25
59895.25
60895.25
61895.25
F Phe
62895.25
F Phe
G Gly
63895.25
F Phe
G Gly
T Thr
64895.25
F Phe
G Gly
T Thr
D Asp
65895.25
F Phe
G Gly
T Thr
D Asp
M Met
66895.25
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
67895.25
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
68895.25
Build the peptide selected peptide
1141.4 Estimate the number of amino acids
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
69895.25
__ __ __ __ __ __ __ __ __ __
Possibly 10 amino acids Consider a y-ion series
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
70895.25
__ __ __ __ __ __ __ __ __ __
1141
1141.4 selected MH
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
71895.25
__ __ __ __ __ __ __ __ __ __
1141
1042
1141.4 selected MH 1042.6 Largest fragment
observed
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
72895.25
__ __ __ __ __ __ __ __ __ __
1141
1042
1141.4 selected MH 1042.6 Largest fragment
observed 98.8 difference Is there an amino
acid with that mass?
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
73895.25
V
__ __ __ __ __ __ __ __ __ __
1141
1042
99 Valine The missing amino acid What is the
next mass observed?
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
74895.25
V
__ __ __ __ __ __ __ __ __ __
1141
895
1042
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
75895.25
V F
__ __ __ __ __ __ __ __ __ __
1141
895
1042
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
76895.25
V F G
__ __ __ __ __ __ __ __ __ __
1141
895
1042
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
77895.25
V F G T
__ __ __ __ __ __ __ __ __ __
1141
895
1042
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
78895.25
V F G T D
__ __ __ __ __ __ __ __ __ __
1141
895
1042
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
79895.25
V F G T D M
__ __ __ __ __ __ __ __ __ __
1141
895
1042
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
80895.25
V F G T D M D
__ __ __ __ __ __ __ __ __ __
1141
895
1042
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
81895.25
V F G T D M D N
__ __ __ __ __ __ __ __ __ __
1141
895
1042
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
82895.25
V F G T D M D N
__ __ __ __ __ __ __ __ __ __
1141
895
1042
262
If this is a y-ion series 262 smallest ion in
the series what does it represent?
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
83895.25
V F G T D M D N
__ __ __ __ __ __ __ __ __ __
1141
895
1042
262
All amino acids in table are peptide bond to
peptide bond
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
84895.25
V F G T D M D N
__ __ __ __ __ __ __ __ __ __
1141
895
1042
262
Were missing one N-terminal hydrogen
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
H
85895.25
V F G T D M D N
__ __ __ __ __ __ __ __ __ __
1141
895
1042
262
Were missing one C-terminal OH Group
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
OH
H
86895.25
V F G T D M D N
__ __ __ __ __ __ __ __ __ __
1141
895
1042
262
And the ionizing proton Total 19
amu
y series ions
H
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
OH
H
87895.25
V F G T D M D N
__ __ __ __ __ __ __ __ __ __
1141
895
1042
262
262 smallest identified fragment - 19 mass of
H OH H 243 mass of missing amino acids
What amino acids?
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
88895.25
V F G T D M D N
__ __ __ __ __ __ __ __ __ __
Hint Tryptic!
1141
895
1042
262
262 smallest identified fragment - 19 mass of
H OH H 243 mass of missing amino acids
What amino acids?
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
89895.25
V F G T D M D N
__ __ __ __ __ __ __ __ __ __
1141
895
1042
262
87 Serine 156 Arginine 243 19 mass of
H OH H 262
115 Aspartic Acid 128 Lysine 243 19 mass
of H OH H 262
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
90895.25
V F G T D M D N S R
__ __ __ __ __ __ __ __ __ __
1141
895
1042
262
87 Serine 156 Arginine 243 19 mass of
H OH H 262
y series ions
F Phe
G Gly
T Thr
D Asp
M Met
D Asp
N Asn
91Some fragmentation studies basics
- Few examples from literature
- Cannot talk about all classes of compounds
- These examples suggest problem solving approaches
- Examples
- Peptides
- Fragmentation mechanism
- Sequence a peptide
- Flavonoids
- Fatty Acids
- Oligonucleotides
92Flavonoids
- Common secondary plant metabolite
- Including flavonoid aglycones, O-glycosides,
C-glycosides (arrows) - Need reliable methodology for analysis
Ref Cuyckens 2004
93Flavonoids
- Group classification, chalcone aglycones, etc.
Ref Cuyckens 2004
94Flavonoids
- Group classification, chalcone aglycones, etc.
- Reported structures
300
250
400
19
350
450
Ref Cuyckens 2004
95Ion nomenclature for flavonoid glycosides(apigeni
n 7-O-rutinoside illustrated)
nomenclature suggested by Ma, 1997 and Domon,1988
96Ion nomenclature for flavonoid glycosides(apigeni
n 7-O-rutinoside illustrated)
A and B ions (retro-Diels-Alder reactions) are
most diagnostic - provide number and type of
substituents in A B ring
97Low-energy CID (Fab-Magnetic sector-Quadrupole)
flavonol typical 0,2A 0,2A-CO 1,4A2H 1,3B-2H
flavone typical 1,3B 0,4B 0,4B-H2O
kempferol
luteolin
Ref Ma, 1997
98Low-energy CID (Fab-Magnetic sector-Quadrupole)
luteolin (flavone)
kempferol (flavonol)
99Low-energy CID (Fab-Magnetic sector-Quadrupole)
luteolin (flavone)
kempferol (flavonol)
100Some fragmentation studies basics
- Few examples from literature
- Cannot talk about all classes of compounds
- These examples suggest problem solving approaches
- Examples
- Peptides
- Fragmentation mechanism
- Sequence a peptide
- Flavonoids
- Fatty Acids
- Oligonucleotides
101Fatty Acids
- Fragments formed by cleavage at alkyl bond can
occur by charge remote fragmentation (generally
at higher energies) - High Energy Sector (KeV)
- Low Energy QQQ, Qtrap, FTICR
- Intermediate Energy Sector hybrids, TOF/TOF
(collision gas, i.e. Xe) - Homolytic bond-fragmentation mechanism (C--C ?
C- -C radicals) - 1,4-H2 elimination mechanism (Jensen, Tomer,
Gross, 1985) - X O- or OLi2
Ref Jensen, 1985
102Fatty Acids
- H-atom cleavage CRF mechanism (Claeys Van den
Heuvel, 1994) - X OLi2 or OBuLi
Ref Claeys, 1994
103Stearic acid (ESI-Sector-OATOF, 400eV collision,
Xe)
Ref Griffiths, 2003
104Oleic acid (ESI-Sector-OATOF, 400eV collision,
Xe)
Ref Griffiths, 2003
105docosahexaenoic acid ANSA derivative (Sector,
400eV collision, Xe)
Gaps due to double bond
Ref Griffiths, 2003
106docosahexaenoic acid ANSA derivative (QQQ, 30 eV
collision, Ar)
Gaps due to double bond
Ref Griffiths, 2003
107Some fragmentation studies basics
- Few examples from literature
- Cannot talk about all classes of compounds
- These examples suggest problem solving approaches
- Examples
- Peptides
- Fragmentation mechanism
- Sequence a peptide
- Flavonoids
- Fatty Acids
- Oligonucleotides
108Oligonucleotides
- McLuckey Nomenclature for multiply charged anions
- Gentle collisional activation base loss
- Moderate conditions consecutive fragmentations
Ref McLuckey, 1993
109Comparison of activation methodsCAD (CID) vs.
IRMPD (Quadrupole Ion trap)
Parent-3
- IRMPD
- Low mass observed
- PO3-1
- base anions
- Complete coverage
Ref Keller, 2004
110Comparison of activation methodsCAD (CID) vs.
IRMPD (Quadrupole Ion trap)
- CAD
- Loss of base
- provides little info
- leads to backbone
- cleavages
- Complete coverage
Parent-3
- IRMPD
- Low mass observed
- PO3-1
- base anions
- Complete coverage
Ref Keller, 2004
111Comparison of activation methodsCAD (CID) vs.
IRMPD (Quadrupole Ion trap)
- CAD
- Loss of base
- provides little info
- leads to backbone
- cleavages
- Complete coverage
Parent-3
- IRMPD
- Low mass observed
- PO3-1
- base anions
- Complete coverage
Ref Keller, 2004
112Steps for interpretation of oligonucleotide mass
spectra for determination of sequence
Ref Ni, 1996
113Steps for interpretation of oligonucleotide mass
spectra for determination of sequence
Ref Ni, 1996
114Comments on steps to interpretation
Ref Ni, 1996
115Suggested Reading List References
- General MS/MS
- NIST Chemistry WebBook http//webbook.nist.gov/c
hemistry/ - Rossi, D.T., Sinz, M.W., Mass Spectrometry in
Drug Discovery, 2002, Marcel Dekker, Inc., New
York, NY. - Bartmess, J.E., Gas-Phase Equilibrium Affinity
Scales and Chemical Ionization Mass-Spectrometry,
Mass Spec. Reviews,1989, 8297-343. (Affinity
Tables) - McCloskey, J.A., Ed., Tandem Mass Spectrometry,
Methods in Enzymology, 1990, Vol 193, Academic
Press, N.Y. - Peptides
- Gu, C., Somogyi, A., Wysocki, V.H.,
Medzihradszky, K.F., Fragmentation of protonated
oligopeptides XLDVLQ (XL, H, K or R) by surface
induced dissociation additional evidence for the
mobile proton model., Analytica Chem. Acta,
1999, 397247-256 - Yalcin, T., Csizmadia, I.G., Peterson, M.R.,
Harrison, The Structure and Fragmentation of Bn
(n 3) Ions in Peptide Spectra., A.G., J. Am.
Soc. Mass Spectrom., 1996, 6, 1164-1174. - Wysocki, V.H., Tsaprailis, G., Smith, L., Breci,
L., Mobile and localized protons a framework for
understanding peptide dissociation, J. Mass
Spectrom., 2000, 35, 1399-1406. - Flavonoids
- Cuyckens, F., Claeys, M., Mass spectrometry in
the structural analysis of flavonoids, J. Mass
Spectrom. 2004 39 115. - Ma, Y.L., Li, Q.M., Van den Heuvel, H., Claeys,
M., Characterization of flavone and flavonol
aglycones by collision-induced dissociation
tandem mass spectrometry, RCMS, 1997, 11 1357.
116Suggested Reading List References (2)
- Domon, B., Costello, C.E., A systematic
nomenclature for carbohydrate fragmentations in
FAB-MS/MS spectra of glycoconjugates. Glycoconj.
J., 1988, 5397. - Fatty Acids Charge Remote
- Griffiths, W., Tandem mass spectrometry in the
study of fatty acids, bile acids, and steroids,
Mass Spec. Reviews, 2003, 22, 81-152. - Jensen, N.J., Tomer, K.B., Gross, M.L., Gas phase
ion decomposition occurring remote to a charge
site, J.Am.Chem.Soc., 1985, 1071863-1868. - Claeys M., Van den Heuvel, H., Radical processes
in remote charge fragmentations of lithium
cationized long-chain alkenyl and alkadienyl
salicylic acids, Biol. Mass Spec., 1994,
2320-26. - Gross, M.L., Charge-remote fragmentations
method, mechanism and applications, Int.J.Mass
Spec.Ion Process., 1992, 118 137-165. - Wysocki, V.H., Ross, M.M., Charge-remote
fragmentation of gas-phase ions mechanistic and
energetic considerations in the dissociation of
long-chain functionalized alkanes and alkenes,
Int.J.Mass Spec.Ion Process, 1991, 179-211. - Oligonucleotides
- McLuckey, S.A., Habibi-Goudarzi, S.,
Decompositions of multiply Charged
Oligonucleotide Anions, J.Am.Chem.Soc., 1993,
11512085-12095. - Keller, K.M., Brodbelt, J.S., Collisionally
activated dissociation and infrared multiphoton
dissociation of oligonucleotides in a quadrupole
ion trap, Anal.Chem., 2004, 326200-210. - Ni, J.S., Pomerantz, S.C., Rozenski, J., Zhang,
Y.H., McCloskey, J.A., Interpretation of
oligonucleotide mass spectra for determination of
sequence using electrospray ionization and tandem
mass spectrometry, Anal.Chem., 1996,
681989-1999.