Metal Clusters,, Metalloporphyrins
p p y
and Gas Phase Redox Chemistry:
Applications of FTMS
•Introduction to FTMS
•Two peptide problems
•Distinguishing isomers: primary structure problem
•Secondary structure of HPTH
•Dynamics and mechanism of transition metal redox reactions
•A useful gas phase dehydrogenation reaction
•A selective oxidation of CO by O2
•Equilibrium in charge transfer reactions: Theory and Experiment
•Flavin
Flavin semiquinones
•Halogenated iron porphyrins
•IR spectra of gas phase anionic metal clusters
TRAPPING PLATE
O
O
HN
H
N
N
OH
O
H
NH
OH
O
O
RGD
O
NH2
NH
-H2O
H
O
O
N
H
O
O
H2O
OH
NH
O
HN
O
O
NH
N
NH
NH2
O
O
ISOPEPTIDE
Scheme 1
O
OH
O
O
HN
H
N
N
O
O
m/z 354
from RGD
OH
O
O
HN
H
N
N
+
O
C
H2O
O
m/z 336
O
HN
H
N
N
O
m/z 308
+
CO
C
O
Scheme 5
Total Δm = 46.0032 (measured) vs. 46.0036
calculated)
O
HN
NH
N
O
HO
O
O
m/z 354
from isopeptide
O
HN
NH
N
+
O
C
m/z 336
H2 O
O
O
O
HN
NH
N
O
m/z 308
+
C
O
Scheme 6
CO
Synthetic hPTH (1-31)
1
2
3
4
5
6
7
H – ala – val – ser – glu – ile – gln – leu – nle
30
8
9
29
10
28
11
27
12
26
13
25
14
24
15
- his – asn – leu – gly – lys – lys – leu – asn
23
16
22
17
21
18
20
19
19
18
20
21
17
16
22
23
– ser – asp – glu – arg – val – glu - trp – leu
15
14
24
25
13
26
12
27
11
28
10
29
9
8
30
– arg – lys – leu - leu – gln – asp – val – NH2
7
6
5
4
3
2
1
Conlon, et al., JACS 122, 3007(2000)
Conlon, et al., Bioorg. Med Chem. 10, 731(2002)
SORI CID
SORI-CID
• Charge state of interest was isolated (+4)
• SF6 was introduced through a computer
controlled
t ll d pulsed
l d valve
l ((reservoir
i P ~ 13
mbar)
• Collision excitation was 500 Hz offresonance
SORI CID
SORI-CID
3.8e+6
7.7e+7
4+
B20
A
m
2.6e+6
p
l
i
t
B30
A
u
5.2e+7
m
d
1.3e+6
e
p
B7
l
i
t
0.e+0
0
e+0
741
u
d
e
742
743
m/z
744
746
2.6e+7
B20
B25
Z29
B22
0.e+0
500
750
1000
m/z
1250
1500
SORI CID
SORI-CID
1
0.9
08
0.8
Normalized relativ
ve intensity
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Bond # (From N-te rminus)
19
20
21
22
23
24
25
26
27
28
29
30
Electron Capture Dissociation
(ECD)
• Sample is irradiated with low energy
energy, high
current electrons (10 eV)
• A cooling gas (Ar or SF6) is introduced
through a computer controlled pulsed
valve during the irradiation step
• ECD is a neutralization reaction
ECD Mechanism
Major Products
O
H
H
R C N CHR'
O
H2
R C N CHR'
O
R
+
C + NH2CHR'
a
y
or
O H
H
R C N CHR'
OH
H
R C N CHR'
OH
R C NH + CHR'
c
z
Why ECD?
• Neutral H radical is highly energetic and
highly reactive
– Can
C b
break
k hi
higher
h energy b
bonds
d th
than SORI
SORICID
– Can cleave disulfide bonds and post
posttranslational modifications
– Does not denature peptide
peptide. Cleavage local to
protonation site.
ECD (SF6 Cooling Gas)
9.1e+5
4.e+7
C25
4+
6.e+5
A
m
p
l
i
2.7e+7
A
t
u
m
d
e
p
3.e+5
l
Z12
C24
i
Z25
t
u
d
e
1.3e+7
0.e+0
1380
1418
1457
m/z
1496
1535
3+
C9
0.e+0
600
950
Z22
1300
m/z
C25
1650
2000
ECD (SF6 Cooling Gas)
Normalized reelative intensiity
N
1
0.9
0.8
0.7
0.6
05
0.5
0.4
0.3
0.2
0.1
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
B d # (F
Bond
(From N-terminus)
N
i )
Synthetic hPTH (1-31)
(1 31)
1
2
3
4
5
6
7
H – ala – val – ser – glu – ile – gln – leu – nle
30
8
9
29
10
H+
28
11
27
12
26
13
25
14
24
15
- his – asn – leu – gly – lys – lys – leu – asn
23
16
22
17
21
18
20
19
19
18
20
21
17
16
22
23
– ser – asp – glu – arg – val – glu - trp – leu
15
14
24
25
13
26
12
27
11
28
10
29
9
8
30
– arg – lys – leu - leu – gln – asp – val – NH2
7
6
5
4
3
2
1
Peptide Bond #9
O
9
H
N
H
C
C
CH2
13
H
N
H
C
CH2
CH2
N
NH
His
CH2
CH2
HNH2
Lys
O
C
• Helical structure
can di-solvate
proton.
• His-9 may
delocalize the
radical.
N. R. for M=Fe
M Fe
Ekeberg, Lin, Sohlberg, Chen, Ridge, et al., Organomet. 18, 40(1999)
Criteria for an Ideal Charging Agent for
Polyolefins:
• Chemical modification inside the mass
spectrometer
• Functionality in the hydrocarbon not
required
• The predominant product characteristic
of the original hydrocarbon (distribution)
• Minimal fragmentation
+
+
+
Charging
Agent
Hydrocarbon
Adduct
Current Approach - Chain-end
Derivatization
• Organic species (e.g. PR3) covalently attached to the
polymer forming an organic salt
• Labile endgroup necessary for derivatization
– e.g. polyethylene – presence of vinyl group
• Aggressive reaction conditions necessary for saturated
polyolefin
p
y
derivatization
• Several days required for synthesis, sample work-up,
and characterization
Current Approach - Atomic Transition
Metal Ion (M+) Chemistry
On
M+
Product
+
Fragments
Energetic!!!
+
Hydrocarbon
No Reaction
Off
MS interpretation very complicated
Ligated TM chemistry allows better control of the
ion-molecule reaction.
Higher MW Hydrocarbons Show
Similar Double
Dehydrogenation Reactivity
m/z 626
F’
m/z
Inten
nsity (Arb. U
Units)
C-60
Intensity (Arb. Units)
Intensity (Arrb. Units)
C-36
C-44
m/z 738
m/z 962
F’
m/z
/
F’
F′ - C5H6 loss
l
ffrom Adduct
Add t – 2H2
m/z
Inten
nsity (Arb. U
Units)
Comparison with Past
Work
LDI-TOF MS (Chen & Li, 2000)
F
Inte
ensity (Arb. Units)
200
Adduct
F
FF
FF
287
374
m/z
/
462
• reaction
ti off C-28
C 28 with
ith C
Co+
produces adduct ion as
well as extensive
fragmentation
550
FTMS(Byrd, Guttman, Ridge 2003)
• reaction with CpCo•+
shows
h
minimal
i i l
fragmentation
Adduct - 2H2
F′
200
287
374
m/z
462
F′ - C5H6 loss
l
ffrom Adduct
Add t –2H
2H2
550
Oxidation of Metal Monocarbonyl
y Cations
M(CO)+ + O2 Æ MO+ + CO2 (1)
observed only for M = Fe
not observed for M = Cr, Mn, Co, Ni
Thermochemistryy of O2 Oxidation of CO Ligand
g
(Kcal/mol)
M
D(M+-CO)
D(M+-O)
ΔH(1)
[state]
[state]
C
Cr
21 4 [6Σ+]
21.4
85 8 [4Σ-]
85.8
-72.4
72 4
Mn
22.1 [5Π]
68.0 [5Π]
-52.3
Fe
31.3 [4Σ-]
80.0 [6Σ+]
-56.7
C
Co
41 [3Δ]
41.5
74.9
4 9 [5Δ]
-41.1
41 1
Ni
41.7 [2Σ+]
63.2 [4Σ-]
-29.6
Reaction of FeCO+ w/ O2; Xfer Method, 2.1x10^-7 Torr
1.2
Relative Ion Inte
ensity
1
FeO+
Fe(CO)+
0.8
m/z 72
0.6
m/z 84
m/z 88
0.4
F (O2)+
Fe(O
0.2
0
0
0.5
1
1.5
2
Tim e (s)
2.5
3
3.5
Fe(CO)
F
(CO)+ + O2 Æ products
d t
0
0
0.5
1
F O+
FeO
1.5
2
2.5
Ln Re
elative Ion Inten
nsity
-0.5
-1
m/z 84
-1.5
-2
Fe(O2)+
-2.5
Time (s)
The Effect of Exciting Fe(CO)+
0
0
0.5
1
1.5
2
2.5
Ln
n Relative Ion Intensity
-0.5
-1
-1.5
m/z 84
Begin excite pulse
Excite Pulse
-2
-2.5
Time (s)
Potential Energy Surface
for Fe(CO)+ + O2
4FeCO+
+ 3O2 (0)
6Fe(O )+
2
+ CO (+7)
6Fe(O) +
2
+ CO (+5)
T. S.
4Fe(CO)(O )+
2
6FeO+
+ CO2 (-57)
Potential Energy Surface
for Cr(CO)+ + O2
6CrCO+
6Cr(O )+
2
+ CO (+11)
2Cr(O) +
2
+ CO (-34)
+ 3O2 (0)
T. S.
6Cr(CO)(O
C (CO)(O2)+
4CrO+
+ CO2 (-72)
1.0
0.9
Relative Abundance
e
0.8
Lumiflavin-
0.7
0.6
0.5
0.4
0.3
Naphthaquinone
N
hth
i
0.2
0
0.1
0.0
0
10
20
30
40
50
60
70
Reaction Time (sec.)
Variation with time of lumiflavin anion and 1
1,4
4 naphthoquinone
anion in a mixture of the neutrals
80
Flavin in Various Oxidation States
R
R
N
N
O
N
-PA(Fl)
NH
N
A. Oxidized (Fl)
R
N
-
O
A. Protonated Oxidized (Fl)
R
N
O
NH
N
H
O
-EA(Fl)
N
N
.
O
N
-PA(Fl
PA(Fl-)
NH
N
H
O
N
O
NH
.
O
B. Red Semiquinone
(Radical Anion, Fl-)
C. Blue Semiquinone
(Radical, FlH)
R
N
H
N
O
NH
N
H
O
D. Fully Reduced (FlH2)
IP(FlH)
Measured and Computed Properties of Redox Forms of Lumiflavin
Property B3-LYP/6-31G(d)a,b
B3-LYP/6-31+G**a,c
Experimental
FTMS
(Electrochemistry)
EA(Fl)
1.54 eV
(B3 LYP/6 311++G(d)
(B3-LYP/6-311++G(d)
2.00 eV)
1.96 eV
1.86 ± 0.06 eV
PA(Fl)
221 kcal mol⁻1
(B3-LYP/6-311++G(d)
215kcal mol-1)
PA(Fl⁻)
332 kcal mol⁻1
322 kcal mol-1
332 ± 3.2 kcal
mol⁻1
D(Fl H)
D(Fl-H)
54 8 kkcall moll⁻11
54.8
54 2 kkcall moll⁻11
54.2
59.77 ± 2.2
59
2 2 kcal
k l
⁻1
mol
(60.6 ± 2.4 kcal
mol-1)
IP(FlH)
6.38 eV
225.5 ± 2.2 kcal
mol⁻1
a) Theoretical numbers correspond to 0 K.
b) Present Results
c) Hadad, et al. JACS 124, 7226(2002)
d) Experimental measurements at 298 K.
e) Anderson, Biochem. Biophys. Acta 722, 158(1983).
6.40 ± 0.10 eV
Iron Tetraphenyl-porphyrin Series
X
X
X, Y, Z
Y
Y
N
X
Z
X
N
N
Fe
X
X
N
Y
Y
X
X
Symbol used in
this work
X = H,
H Y=
C6H5, No Z
FeTPP
X = H, Y =
C6H5, Z = Cl
FeTPPCl
X = H, Y =
C6F5, No Z
FeTPPF20
X = H, Y =
C6F5, Z = Cl
FeTPPF20Cl
X = Cl, Y =
C6F5, No Z
FeTPPF20Cl8
X = Cl, Y =
C6F5, Z = Cl
FeTPPF20Cl9
Fluoroalkyl Series
X
X
Y
Y
N
X
Z
X
N
N
Fe
X
X
N
Y
Y
X
X
X, Y, Z
Symbol used
in this work
X = Y = H,
No Z
FeP
X = Y = H,
Z=Cl
FePCl
X = H, Y = CF3,
Z = Cl
FeP(CF3)4Cl
X=H
H, Y = C3F7, Z
= Cl
FeP(C
(C3F7)4Cl
Octaethyl Series
X
X
X Y
X,
Y, Z
Y
Y
N
X
N
FeOEPCl
X
X = C2H5,
Y = H,
Z = Cl
X = C2H5,
Y = NO2,
Z = Cl
FeOEP(NO2)4Cl
N
X
N
Y
Y
X
FeOEP
X
X = C2H5,
Y = H,
No Z
Z
Fe
X
Symbol
y
used in
this work
Electron Affinity Ladder
C
Compound
d
EA (eV)
TCNE
[3.17]
Fe(OEP)(NO2)4Cl
2.93
F4-BQ
[2 70]
[2.70]
Fe(OEP)(NO2)2Cl
2.54
Fe(OEP)(O)Cl
2.53
2,6-Cl2BQ
[2.48]
NO2
[2.29]
Fe(OEP)Cl
2.07
4 NO2NB
4-NO
[2.00]
BQ
[1.91]
NPQ
[1.81]
Fe(OEP)
1.68
3-NO2NB
[1.65]
An Iron (II) Porphyrin (FeTPPF20) with C4v Symmetry
Dmol program, geometry optimized, BPW functionals, DNP basis set with “frozen” core
potentials
Dmol program, geometry optimized, BPW functionals, DNP basis set with “frozen” core
potentials
Distances for Spin Unrestricted C4v
4 Fluoroalkyl Series
Molecule
Charge
Fe-N (Å)
Fe-Cl (Å)
Fe-N4 plane (Å)
FeP(CF3)4Cl
Neutral
2.0064
2.1727
0.1333
Anion
2 0022
2.0022
2 2538
2.2538
0 0685
0.0685
Neutral
2.0121
2.1714
0.1603
Anion
2.0088
2.2447
0.0978
N t l
Neutral
2 0121
2.0121
2 1672
2.1672
0 1823
0.1823
Anion
2.0102
2.2376
0.1163
FeP(C2F5)4Cl
F P(C3F7)4Cl
FeP(C
Bond Lengths from X-ray Diffraction for Tetraphenyl Series [Present Results]
[M l l
[Molecule
F N (Å)
Fe-N
F Cl (Å)
Fe-Cl
F N4 l
Fe-N4plane
(Å)
FeTPP
1.972(4)[i], [1.9846a]
N/A
FeTPPCl
2.049(9)[ii], [1.9902a]
2.192(12)[ii][, [2.1812a]
0.383(5)[ii], [0.2200a]
FeTPPF20Cl
2.062(8)[iii], [1.9962a]
2.199(2)[iii], [2.1675a]
0.449(3)[iii], [0.1906a]
a: Present spin unrestricted results for C4v structures.
[i].
JJ.P.
P Collman,
Collman JJ. L
L. Hoard
Hoard, N
N. Kim
Kim, G
G. Lang
Lang, C
C. A
A. Reed
Reed, J.
J Am.
Am Chem
Chem. Soc
Soc., 1975,
1975 97,
97 2676.
2676
[ii]. J. L. Hoard, G. H. Cohen, M. D. Glick, J. Am. Chem. Soc., 1967, 89, 1992.
[iii]. B. Song, D. C. Swenson, H. M. Goff, Acta Crys. Sect C., Volume 54, Part 11 (November 1998), cif-access
(metal-organic compounds). IUC9800058.
Electron Affinities(eV)
M l l
Molecule
Electron
El
t
Affinity
Affi it
(DFT)
Electron
El
t
Affinity
Affi it
(Exp)
FeOEP
1.7557
1.68±0.03
FeTPP
2 134
2.134
1 87±0 03
1.87±0.03
FeOEPCl
2.2724
2.07±0.03
FeTPPCl
2.4704
2.15±0.15
FeTPPF20
2 9887
2.9887
2 15±0 15
2.15±0.15
FeTPPF20Cl
3.3162
3.14±0.03
FeP(CF3)4Cl
3.363
3.16±0.03
F P(C3F7)4Cl
FeP(C
3 5151
3.5151
3 30±0 03
3.30±0.03
EAs of C4v Iron Porphyrins
4
y = 1.0064x
1 0064x + 0.1922
0 1922
R2 = 0.9884
DFT EA ((eV)
3.5
3
2.5
D t
Data
2
Fitted line
1.5
1
0.5
0
0
1
2
3
Experimental EA (eV)
4
IR Spectra of Gas Phase Ions
• Absorption spectroscopy inaccessible
• Multiphoton IR photodissociation possible
• IRMPD spectrum
t
reflects
fl t absorption
b
ti
spectrum
• Candidate ions: Mn(CO)m+/-,
Mn(CO)m(alkane)+, Mn(CO)m(O2)+/-, etc.
• Requires tunable IR laser
Free Electron Laser for Infrared eXperiments "FELIX"
Undulator
FEL-2
5 - 30μm
injector
Linac 1
Linac 2
15-25 MeV
25-45 MeV
Undulator
FEL-1
16 - 250μ m
spectrometer
magnet
OTR
Principles of FTICR-MS
-charged particles trapped by strong, homogeneous magnetic field B (Lorentz force)
- particles orbit magnetic field with frequency dependent only on m/z (for fixed B)
- trapped particles are confined axially by small static voltage to trapping plates (T)
- applying RF to excite plates (E) at cyclotron frequency bunches ions and expands their
orbital radii, improving dynamic range Æ also used to eject unwanted ions
- current induced by moving ions is detected (D) and amplified in time domain, then
Fourier Transformed to obtain frequencies of trapped ions
Cyclotron frequency
f ~ Bz/m
B /
Anionic Metal Carbonyl Clustering Reactions
s\doug\My Documents\FTICR files from FOM\030825-007_Fe2CO8-_PV_p=1e6_8avg_FEL
4.5e+0
A
m
3.e+0
p
l
FELIX
off
54Fe56Fe(CO) 8
i
t
u
1.5e+0
d
e
0.e+0
354705
359822
364939
Frequency (Hz)
370056
375173
doug\My Documents\FTICR files from FOM\030825-013_Fe2CO8-_PV_p=1e6_10avg_FEL
4.3e+0
A
m
2.9e+0
p
l
i
FELIX o
on
4.76μm
t
u
1.4e+0
d
e
0.e+0
0
e+0
354910
359976
365042
Frequency (Hz)
370107
375173
doug\My Documents\FTICR files from FOM\030825-008_Fe2CO8-_PV_p=1e6_10avg_FEL
3.2e+0
A
m
2.1e+0
p
l
i
FELIX on
5.12μm
t
u
d
1.1e+0
e
0.e+0
354880
56Fe (CO) 2
7
359963
365046
Frequency (Hz)
370129
375212
1.00
0.95
0.90
-
m1008 [Fe8(CO)20 ?]
1.0
0.9
0.8
0.7
SORI up to higher masses
0.6
1.00
0.95
0.90
0.85
• In each case, a large percentage (40100%) of the ion population is
transferred into the target mass channel
• Spectra show a blue shift with
increasing size, converging to a value
around 2000 cm-1
• Structure in spectrum also disappears
with increasing size -- indication of
transition from organometallic
complexes to metal-cluster-adsorbate
systems?
0.80
-
m896 [Fe7(CO)18 ?]
1.00
0.95
Norrmalized dep
pletion
• By adding additional frequencies to
the SORI excitation pulse, larger and
larger cluster can be synthesized
-
m952 [Fe9(CO)16 ?]
0.90
0.85
-
Fe5(CO)14
1.00
0.95
0.90
-
Fe4(CO)13
0.85
1.00
0.95
0.90
0.85
-
Fe4(CO)12
1.0
0.9
0.8
0.7
1.0
0.9
0.8
0.7
0
-
Fe3(CO)10
-
Fe2(CO)8
1.0
0.9
0.8
0.7
-
Fe2(CO)7
1.00
0.95
0.90
0.85
-
Fe(CO)4
1600 1650 1700 1750 1800 1850 1900 1950 2000 2050 2100 2150
-1
Wavenumber (cm )
-
Relativ
ve absorpttion cross s
section (arrb. units)
Fe2(CO)8 cluster IRMPD spectrum
E t vs. Calc.
Expt.
C l (B3LYP / LACVP+* w// 0.965
0 965 scaling
li factor)
f t )
Expt. (0
( ddB))
-1
Calc. w/ 12 cm
Gaussian conv.
1650
1700
1750
1800
1850
1900
1950
-1
Wavenumber (cm )
2000
2050
2100
2150
IR spectrum of anionic Fe2(CO)7 cluster
IRMPD (0 dB)
B3LYP/LACVP+*
(scaled by 0.965)
(convoluted
-1
w/12
/12 cm gaussian)
i )
1800
1825
1850
1875
1900
1925
1950
-1
Wavenumber (cm )
1975
2000
2025
2050
Acknowledgments
Delaware
Scott Robinson
David Finneran
Richard Ochran
Jim Witkoski
NHFML & FOM (Utrecht)
David Moore
John Eyler
Michelle Byrd
O
Ounan
Chen
Ch
Charles Guttman
Steve Bennett
L i Ji
Lei
Jin
Tianlan Zhang
University of Oslo
Einaar Uggerud
gg
Dag Ekeberg
Karl Sohlberg
Hung-Yu Lin
Robert McKean
Stephen Conlon
Sun Company
Ji L
Jim
Lyons
Paul Ellis
Tilak Wijesekera
Funds
NSF
Fred Arnold
Henglong Chen
Runzhi Zhao
NIST
Nganha Luu
Jennifer Sterner
Rhone-Poulenc Rorer
Bruker Instruments
Gary Kruppa
Sun
RPR
NIST
Acknowledgements
Delaware
Delaware (contd)
Rhone-Poulenc Rorer
Scott Robinson
Robin Kinser
Runzhi Zhao
David Finneran
g Yu Lin
Hung
Robert McKean
HeeYeon Park
Yi Lin
Steve Conlon
Richard Ochran
Ying Pan
Tom Bailey
Barbara Larsen
Sun Company
Nganha Luu
Fred Strobel
Jim Lyons
Ounan Chen
John Wronka
Paul Ellis
Steve Bennett
Gary Kruppa
Jennifer Sterner
Thuy Nguyen
NHFML & FOM
Lei Jin
Art Smith
John Eyler
Fred Arnold
Rob Freas
David Moore
Tianlan Zhang
Gary Weddle
Henglong Chen
Dana Chattalier
Tom Dietz
John Allison
ESI of (KAA)10
Products of reaction of +9 charge state ion
with di-n-butyl ether
Methods
• SORI-CID
SORI CID and ECD were performed on a
All samples were dissolved to 5 μM in
50:50 MeOH:water,
MeOH:water 1% acetic acid
• Bruker Apex 4.7T instrument
• IRMPD experiments were performed on a
Bruker Apex 3T instrument
SORI CID
SORI-CID
• Cleavage observed at 25 of 30 backbone
positions
• Produced 7 a, 19 b, 5 c, 2 x, 13 y, and 16
z ions
• No cleavage observed within the lactam
bridge
ECD (Ar Cooling Gas)
3.9e+5
2.3e+7
4+
Z22
Y22
C12
A
2.6e+5
m
p
A
l
1.5e+7
m
i
t
p
u
l
d
e
1.3e+5
i
5+
t
u
d
e
7.6e+6
0.e+0
1290
Y29
0.e+0
600
850
1298
1307
m/z
1316
132
3+
C9
1100
m/z
1350
1600
ECD (Ar Cooling Gas)
1
0.9
08
0.8
Normalized relativ
ve intensity
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Bond # (From N-terminus)
19
20
21
22
23
24
25
26
27
28
29
30
ECD (Ar Cooling Gas)
• Cleavage observed at 16 of 30 backbone
positions
• Produced mostly c and z ions (1 a,
13 c, 1 x, 7 z)
1 b,
• No cleavage observed within the lactam
bridge
ECD: A Non-selective
Technique?
1
0.9
0.8
No rmalized relative intensity
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Bond # (From N-te rminus)
• ECD w/ Ar: Cleavage between His-9 and Asn10 accounted for 29.8% of the total normalized
ion abundance
• ECD w/ SF6: Cleavage after His-9 = 29.4%
Major Products
O
R
C
H
H
N
O
CH R'
R
C
H2
N
CH R'
O
R
+
C + NH 2 CH R'
a
O
R
C
H
H
N
OH
CH R'
R
C
H
N
y
OH
CH R'
R
C
c
NH
+
• Peptide Bond #9
– Only site where reverse products (a, y., c., z) are
observed
– Is there an explanation in the structure?
CHR'
z
ECD (SF6) Cooling Gas
• Cleavage observed at 21 of 30 backbone
positions
• Produced 2 a, 14 c, 1 x, 4 y, 13 z
• N
No cleavage
l
observed
b
d within
ithi th
the llactam
t
bridge
Polyolefin Mass
Spectrometry - Importance
• Polyethylene (PE) & polypropylene (PP)
•Large production volume and fast growth
•New metallocene catalysts produce new polyolefin
types
• NIST provides saturated polyolefin standards
• Central Challenge in PE/PP mass spectrometry
•Polymer functionality for cationization absent
•Masses over ~ 2000 u cannot be determined
¾Creating
an intact, gas-phase macromolecular ion
New Approach -η5-Cyclopentadienylcobalt
p •+)
Ion ((CpCo
CpCo•+ ion shows favorable
reactivity toward low mass
alkanes.
alkanes
•+
CpCo
+ CnH2n+2
- mH2
CpCoCnH2n-2m+2 •+
n = 2-6, m = 1, 2
• predominant dehydrogenation
product
d t
• little fragmentation in MS
Müller & Goll ’73, Jacobson & Freiser ’85, & Ekeberg,
Ridge, et al. ‘99
Double Dehydrogenation
Dominates All Three Reactions
Rela
ative Inttensity
1
Rela
ative Intens
sity
C-20
25 %
Rela
ative Inte
ensity
C-15
15 %
1
0.8
0.8
0
8
0.6
0.6
0.4
0.4
02
0.2
0.2
0
0 0.5 1 1.5 2 2.5
Time (s)
- CpCo•+ loss
0
0
1
2
1
0.8
0.6
0.4
02
0.2
0
3
Time (s)
C-28
40 %
0 1 2 3 4 5
Time (s)
- CpCoCnH(2n-2)•+ formation
- other products
Byrd, Ridge & Guttman, J. Am. Chem. Soc. Mass Spectrom. 2003, 14, 51-57.
Structures of Flavins
H+
Photolysis
Isoalloxaziine ring
6
7
pH<7
8
9
H+ or OH-
pH>9
N
N
O
O
N 5
10 N
CH2
(CH2O)3 CH2O
P
OH
O
1N
4
3
HN
2
O
Lumichrome
Lumiflavin
Riboflavin (vitamin B2)
Riboflavin-5-monophosphate (FMN)
Flavin-adenine-dinucleotide
l i d i di l id (FAD)
(
)
O
P
O
H2
C
O
N
OH
HO
OH
NH2
N
Distances for Spin Unrestricted C4v Tetraphenyl Series
Molecule
Charge
Fe-N (Å)
Fe-Cl (Å)
Fe-N4 plane (Å)
FeTPP
Neutral
1.9846
N/A
0.0093
Anion
1.9856
N/A
0.0040
Neutral
1.9902
2.1816
0.2200
Anion
1.9868
2.2496
0.1300
Neutral
1.9914
N/A
0.0116
Anion
1.9889
N/A
0.0109
N t l
Neutral
1 9962
1.9962
2 1675
2.1675
0 1906
0.1906
Anion
1.9945
2.2400
0.1239
FeTPPCl
FeTPPF20
F TPPF20Cl
FeTPPF
Di t
Distances
for
f Spin
S i Unrestricted
U
t i t d C4v Octaethyl
O t th l Series
S i
Molecule
Charge
Fe-N (Å)
Fe-Cl (Å)
Fe-N4 plane (Å)
FeOEP
Neutral
1.9906
N/A
0.0008
Anion
1.9898
N/A
0.0007
Neutral
1.9893
2.2271
0.1593
Anion
1.9898
2.264
0.1241
Neutral
2.0377
2.1695
0.2061
Anion
2.0326
2.2403
0.1064
FeOEPCl
FeOEP(NO2)4Cl
IR M P D s p e c tra o f a n io n ic iro n c a rb o n y l c lu s te rs
-
F e 5(C O )14 (m 6 7 2 )
-
F e 4(C O )13 (m 5 8 8 )
-
F e 4(C O )13 (m 5 6 0 )
-
F e 3(C O )10 (m 4 4 8 )
-
F e 2(C O )8 (m 3 3 6 )
-
F e 2(C O )7 (m 3 0 8 )
1750
1800
1850
1900
1950
2000
W a v e n u m b e r (c m
-1
2050
)
2100
2150
Theoretical spectrum
p
from
Schaefer’s calculations for
D2h unbridged structure.
Frequencies lowered by
46 cm-1.
1750 1800
1850 1900
1950
2000
Frequency (cm-1)
2050
2100
2150
Theoretical spectrum from
Schaefer’s calculations for
tetrabridged structure.
Average lowered by 40
cm-1and range expanded
10% about average.
average
Imported from Excel plot
1750 1800
1850 1900
1950
2000
Frequency
(cm-1)
2050
2100
2150
Theoretical spectrum from
Schaefer’s calculations for
a dibridged C2h structure.
Average lowered by 57
cm-1. Imported from
Excel plot
1750 1800
1850 1900
1950
Frequency
2000
(cm-1)
2050
2100
2150
Fe2(CO)8- anion
spectrum
1750 1800
Theoretical spectrum from
Schaefer’s calculations for
dibridged C2v structure.
Average lowered by 60
cm-1 and range
g expanded
p
by 10%. Imported from
Excel plot
1850 1900
1950
2000
Frequency (cm-1)
2050
2100
2150
Fe2(CO)7- anion spectrum
Fe2(CO)7 neutral harmonic
frequencies (lowered by 52
cm-1 and expanded by 10%
about the average) and
intensities from DFT
calculations for triply bridged
structure in ref. 1.
1750 1800 1850 1900 1950 2000 2050 2100 2150
F
Frequency
(cm
( -11)
Fe2((CO))7 neutral tribridged
g C2v
structure optimized using DFT
from ref. 1.
1. Xie, Schaefer and King, JACS, 122, 8746(2000)
Fe2(CO)7- anion spectrum
Fe2(CO)7 neutral harmonic
frequencies (lowered by 52
cm-1 and expanded by 10%
about the average) and
intensities from DFT
calculations for singly bridged
structure in ref. 1.
1750
1800
1850 1900
1950
2000 2050
2100
2150
Frequency (cm-1)
Fe2(CO)7 neutral
monobridged
b id d C2v
structure optimized
using DFT from ref. 1.
1. Xie, Schaefer and King, JACS, 122, 8746(2000)
Fe2(CO)7- anion spectrum
Fe2(CO)7 neutral harmonic
frequencies (lowered by 62
cm-1 and expanded by 10%
about the average) and
intensities from DFT
calculations for
unsymmetrically doubly
bridged structure in ref. 1.
1750
1800
1850 1900
1950
2000 2050
2100
2150
Frequency (cm-1)
Fe2(CO)7 neutral asymmetrically
dib id d Cs structure
dibridged
t t
optimized
ti i d
using DFT from ref. 1.
1. Xie, Schaefer and King, JACS, 122, 8746(2000)
“The goddammed mass spectrometer is broken again!”
(title by Frank Field)
Electron Capture Dissociation
of Human Parathyroid
Hormone
A comparison with common
g
techniques and
fragmentation
selective cleavage at histidine
Human Parathyroid Hormone
(hPTH)
• 84 amino acid protein that regulates
calcium levels in blood
• Mild to moderate hyperthyroidism results
in increased bone density
• Treatment
T t
t with
ith the
th amino
i portion
ti off hPTH
(amino acids 1-34) promotes bone
f
formation
ti
F e (C O )4
-
E x p . v s . C a lc .
(u n s c a le d fre q u e n c ie s )
IR M P
F it to
F itte d
F itte d
B 3L Y
1800
1825
1850
1875
1900
1925
1950
1975
W a v e n u m b e r (c m
-1
2000
D w /2 0 d B
E x p t.
p e a k @ 1 8 5 8 .4
p e a k @ 1 8 4 9 .4
P / L A C V P (* * )(+ + )
2025
2050
2075
2100
)
Notes:
The calculated curve was generated by convoluting the stick spectrum with a 12 cm-1
gaussian lineshape. The fitted widths for the two peaks in the experimental spectrum are ~15
15 and
~10 cm-1 . Forcing them to be 12 cm-1 does not significantly alter the fit, other than to make the
areas of the peaks more similar.
The calculated frequencies are unscaled, but the “optimal” factor is ~0.97, which I find
quite reasonable, particularly since the basis set used an ECP (effective core potential). Also, this
scaling makes the splittings more similar (9 cm-1 and 12 cm-1 for the expt. and calc, repsectively.)