me 330.804: mass spectrometry in an “omics” world...• records an entire mass spectrum • best...

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ME 330.804: Mass Spectrometry in an “Omics” World

Lecture 2WED 24 OCT, 2012R CotterMass Analysis and MS/MS

MAMS bioaerosolmass spectrometer

1ME 330.804: MS2012Mass Spectrometry in an “Omics” World http://www.hopkinsmedicine.org/mams/

MALDI is generally used on a time-of-flight MS

1948 Cameron and Eggers: velocitron

1953 Wolff and Stephens: constant momentum TOF

1955 Katzenstein & Friedland:drawout pulse

1955 Wiley and McLaren:time-lag focusingcommercialized by Bendix

Early milestones

Wiley, W.C.; McLaren, I.H., Time-of-Flight Spectrometer with Improved Resolution, Rev. Sci. Instr. 26 (1955) 1150-1157


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160

180

200

220

240

0S 10uS 20uS 30uS

Substance P, 1348 Da

Methionine enkephalin-Arg-Gly Leu 900 Da

Peptide sequencing standard, 1639 Da

Parathyroid hormone 28-48, 2148 Da

Beta-melanocyte, 2660 Da

Hepatitus B virus pre-S region 120-145, 3008 Da

Diabetes-associated peptide 8-37, 3200 Da

ACTH 7-38, 3659 Da

ACTH 1-39, 4541 Da

Pancreatic polypeptide, 4182 Da

Biocytin beta-endorphin, 3819 Da

160

180

200

220

240

0S 10uS 20uS 30uS

Substance P, 1348 Da

Methionine enkephalin-Arg-Gly Leu 900 Da

Peptide sequencing standard, 1639 Da

Parathyroid hormone 28-48, 2148 Da

Beta-melanocyte, 2660 Da

Hepatitus B virus pre-S region 120-145, 3008 Da

Diabetes-associated peptide 8-37, 3200 Da

ACTH 7-38, 3659 Da

ACTH 1-39, 4541 Da

Pancreatic polypeptide, 4182 Da

Biocytin beta-endorphin, 3819 Da

DeV

mt

2/1

2

A simple “linear” time-of-flight mass spectrometer

A time-of-flight mass spectrum of a mixture of peptides

The time-of-flight mass spectrometer


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02/1

0

2/12/1

02/1

0

2/1

2

22t

eEsU

DmUeEsU

eE

mt

time in ion source time in flight tube

initial kineticenergy distribution

distribution of initial position inthe source

turn-around time distribution in

time of ion formation

The real time-of-flight equation


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How is the effect of an initial kinetic energy distribution improved?

(a) low laser power

(b) high accelerating voltage

(c) reflectron

Ions formed with different initial kinetic energies

20 2

1mvUeV

The ion will leave the source with a larger kinetic energy

a higher velocity, and a shorter flight time, causing lower mass resolution.


6

How is the effect of an initial spatial distribution improved?

(a) thin sample

(b) detector at D = 2s

(c) dual stage extraction to move the space-focus plane

Ions are formed in different locations

Ions leave the source with energies eEs’ dependent upon their location

where s’ = s-∆s

]'2['2

2/1

DseEs

mt


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Wiley, W.C.; McLaren, I.H., Rev. Sci. Instrument. 26 (1955) 1150-1157.

Ions differing in initial position in the source, initial kinetic energies and different directions of their initial velocities are focused in the Wiley-McLaren TOF mass spectrometer.

Time-lag focusing

E0

s0 s1

E1

Drawout pulsePushout pulse

1

2

3

4


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Whittal, R.M.; Li, L., Anal. Chem. 67 (1995) 1950-1954Brown, R.S.; Lennon, J.J., Anal Chem. 67 (1995) 1998-2003.Vestal, M.L.; Juhasz, P.; Martin, S.A, Rapid Commun. Mass Spectrom. 9 (1995) 1044-1050.

U0

U1

U2

U0

U1

U2

20 kV (constant)

18 kV (constant)

Ground (constant) Ground (constant)

2 kV pulse20 kV

18 kV

20 kVNegative pulse

0 V

delay delay

timetime

ABI, Kratos and others Bruker and others

Delayed extraction and MALDI

Time-lag focusing and “delayed extraction”


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t = m

2eV [ L + L + 4d]

1/ 2

1 2

Reflectrons correct for the effects of kinetic energy spread after the ions have left the source

Single-stage reflectron

Dual-stage reflectron

Mamyrin, B. A.; Karataev, V. I.; Shmikk, D. V.; Zagulin, V. A, Mass reflectron. New nonmagnetic time-of-flight high-resolution mass spectrometer. ZhurnalEksperimental'noi i TeoreticheskoiFiziki (1973) 64, 82-89.


10

0

10

20

30

40

50

60

70

80

90

100

%Int.

5731 5732 5733 5734 5735 5736 5737 5738 5739 5740 5741

Mass/Charge

1[c]

573

5.6

4

573

4.6

3

573

6.6

3

57

33.6

5

573

7.6

4

573

2.5

6

573

8.6

3

57

31.4

3

57

39.7

2

Insulin B-chain using delayed extraction/time-lag focusing on a linear instrument (no reflectron)

Bovine insulin using delayed extraction/time-lag focusing on a reflectron instrument

Delayed extraction on linear and reflectron TOFs


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What does it do?

• improves mass resolution: ions are extracted at right angles to the initial velocity (kinetic energy) distribution

• improves duty cycle: ions are stored between pulsed extraction cycles

Dawson, J.H.J.; Guilhaus M., Rapid Commun. Mass Spectrom. 3 (1989) 155.

Dodenov, A.F.; Chernushevich, I.V/; Laiko, V.V., in Time-of-Flight Mass Spectrometry, in Cotter, R.J., Ed,; ACS Symposium Series 549, Washington DC (1994) pp. 108-123.

Orthogonal acceleration mass spectrometers

To drift region

Pushout pulse

EI source Focusing lenses

x

y

z


oa-TOF with an ion guide and reflectron

Commercial orthogonal acceleration TOFs can have mass resolutions up to 60,000


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What’s out there? JEOL, USA

AccuTOF™ DART® Direct Analysis in Real Time Time-of-Flight Mass Spectrometer

AccuTOF™ LC Liquid Chromatograph Time-of-Flight Mass Spectrometer


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Bahr, U.; Karas, M., Rapid Commun. Mass Spectrom. 13 (1999) 1052-1058.

Orthogonal acceleration and mass accuracy


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http://www.chem.vt.edu/chem‐ed/ms/quadrupo.html

Quadrupole mass spectrometers

http://huygensgcms.gsfc.nasa.gov/MS_Analyzer_1.htm


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http://www.waters.com/WatersDivision/ContentD.asp?watersit=EGOO-66MNYR&WT.svl=1#quads

dc voltage: Urf voltage: V0cos(t)

If U/V0 = 0.167, ions of m/z are transmitted (have stable trajectories) when:

m/z = 0.136V0/r02f2

where f is 1MHz

rf-only mode transmits all ions and is used for:• collision chamber• quadrupole injection into a trap or oaTOF (ion guide)

How it works: the stability diagram


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Mass filter

• passes a single mass at any time; throws all other masses away

• best example is a quadrupole

• can be used as a mass spectrometer by scanning

• high duty cycle for monitoring single ions; low duty cycle for acquiring a mass spectrum

Mass spectrometer

• records an entire mass spectrum

• best duty cycle is a mass analyzer with the multiplex recording advantage, i.e records all ions of all masses

• best examples are the TOF, ion trap and FTMS

The quadrupole is a mass filter. How does that differ from a mass spectrometer?


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S D

DC and RF voltages set to pass a single mass

RF-only mode to pass all masses; used as a collision chamber

DC and RF voltages scanned to record all masses in succession

Because both mass analyzers are mass filters, the duty cycle for scanned spectra is low

The quadrupole is a mass filter. To record a mass spectrum it must be scanned

The triple quadrupole: a tandem MS


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MS1 Activation Region

MS2S D

vacuum system

Tandem mass spectrometers have…

a mass analyzer (MS1) that separates ions by mass and selects ions of a single mass …. mass filter

an activation region for fragmenting mass-selected ions … generally by collision-induced dissociation

a mass analyzer (MS2) for recording the mass spectrum of the fragments of the selected mass …. mass spectrometer

Tandem mass spectrometers


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S D

Triple quadrupole mass spectrometers

dc

volt

age

dc

volt

age

dc

volt

age

time time time

Normal (product ion) scan

Multiple reaction monitoring (MRM)

dc

volt

age

dc

volt

age

dc

volt

age

time time time


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Q1 is an RF-only quadrupole filter that collimates ions from high pressure source.

Q3 is an RF-only quadrupole filter used as a collision chamber.

Collisions are low energy.

Q2 is a quadrupole mass filter that selects the precursor mass

The TOF makes it possible to analyze product ions with higher m/z than their precursors

Electrospray ionization on a QTOF


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What are the advantages?

• MS1 is a mass filter for selection of a single precursor from a continuous beam; MS2 is a multiplex recorder. Optimal configuration for product ion MS/MS spectra.

• better mass accuracy from the TOF than a third quadrupole on a triple quadrupole mass spectrometer

What are the disadvantages?

• storage/extraction has limited duty cycle

• low energy collisions in q3; not as effective for some post-translational modifications

Why use a quadrupole/TOF?


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ABI 5600 TripleTOF

Resolution, MS High MassUp to 40,000 (FWHM) at m/z 956 using a 10 ms accumulation time.Resolution MS/MS Low MassUp to 25,000 (FWHM) at ~100 m/z using a 10 ms accumulation time.Resolution MS/MS, High mass Up to 30,000 (FWHM) on a fragment ion from [Glu]-Fibrinopeptide B above precursor m/z using a 10 ms accumulation time.

What’s out there?


What’s out there?

Waters Synapt G2-S

“Step-wise” ion funnelETDMSE


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Collision energy is derived from the relative energy between the ion and the target gas (in the center-of-mass frame) and is related to the kinetic energy in the laboratory frame

Low energy CID uses multiple collisions, raises the internal energy slowly until the weakest bond breaks.

Low energy CID is not particularly favorable for determining post-translational modifications, especially phosphorylation or glycosylation.

High energy CID is usually carried out on a tandem time-of-flight (TOF/TOF) mass spectrometer

High vs. low energy CID

LABMn

nrel E

mm

mE

ELAB is 10-60 eV

ELAB is 1-20 keV


ion source

mass selection gate

retarding lens

collision cell

2nd source pulsed extraction

ion source

mass selection gate

collision cell “lift” cell

ion source mass selection gate

collision cell

a

b

c

20 keV1 keV

19-20 keV

8 keV

15-23 keV

20 keV

0-20 keV

0-8 keV

ion source

mass selection gate

retarding lens

collision cell

2nd source pulsed extraction

ion source

mass selection gate

collision cell “lift” cell


collision cell


collision cell

a

b

c

20 keV1 keV

19-20 keV

8 keV

15-23 keV

20 keV

0-20 keV

0-8 keV

Applied Biosystems

Bruker Daltonics

Shimadzu AXIMA TOF2

Tandem time-of-flights available commercially

Curved-field reflectron


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ultrafleXtreme™

1 Hz-1 kHz rep rate laserR= 40,000

What’s out there?

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Bruker DaltonicsABI Sciex

5800 TOF/TOF

1 kHz rep rate laserMS/MS Resolution (Precursor Glu1-Fib)175.1195 RES > 2800684.3469 RES > 45001056.4750 RES > 55001441.6348 RES > 6500


What’s out there?

Shimadzu (Kratos)AXIMA TOF2

Collision energy: 20 keVR (linear mode): 5,000R (reflectron mode): 20,00


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Unimolecular, low and high energy collisions

Courtesy of G

uenter Allm

aier, Martina

Marchetti-D

eschmann and E

rnst Pittenauer


High energy CID increases side chain fragmentation

Courtesy of G

uenter Allm

aier, Martina

Marchetti-D

eschmann and E

rnst Pittenauer


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ring electrode

endcap electrode

endcap electrode

supplemental RF voltage

fundamental RF voltage (1.1 MHz)

signal out

electron filament –70V

gas or volatile sample in

helium bath gas in

vacuum chamber

Scan amplitude to obtain all mass spectra

• resonance ejection mode mass scan

• high amplitude RF for ion ejection, isolation or selection

• low amplitude RFfor ion activation

Quadrupole ion trap: “tandem in time”


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20

20

20 )2(

8

zrm

eVqz

20

20

20 )2(

16

zrm

eUaz

zqzr

V

z

m20

20

20 )2(

8

Mathieu parameters:

Mass selective instability mode:if dc voltage on the endcaps is zero, then scan along the az line (by varying the rf voltage); ion ejection occurs at the stability boundary when az = 0.908

The mass ejected is then given by:

Where z is the number of charges and 0 is the angular drive frequency(0/2 = 1.1 MHz)

Williams, J.D.; Cox, K.A.; Schwartz, J.C.; Cooks, R.G., in Practical Aspects of Ion Trap Mass Spectrometry, Volume II, Cairns, T., Ed., CRC Press, Boca Raton (1995), pp. 3-50


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ring electrode

endcap electrode

endcap electrode

fundamental RF voltage (1.1 MHz)

signal out

The “mass-selective instability” mode

mass scan

ion trapping

ion cooling

ionization


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Mass

Inte

nsit

y

220

4

rq

eVm

z

z0

r0

)(

)(

RFVq

DCUa

z

z

matrixscience.org

How do ion traps work?


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Resonance ejection mode:

A supplementary rf voltage is applied to the endcaps

The fundamental rf voltage on the ring electrode is scanned

Ions are ejected “through a hole in the stability region”

Extension of mass range through axial modulation

Supplementary rf = 69.9 kHzqeject = 0.182m/z = (0.91/0.182) x 650 = 5 x 650 = 3,250

Supplementary rf = 35.2 kHzqeject = 0.091m/z = (0.91/0.091) x 650 = 10 x 650 = 6,500


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ring electrode

endcap electrode

endcap electrode


The “resonance ejection” mode

mass scan

ionizationfundamental RF voltage (1.1 MHz)

signal out



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I-III. trapping cycle: fundamental (1.1 MHz) RF voltage on ring electrode

IV. mass isolation cycle (MS1): resonant ejection of all but selected ion, using high amplitude supplementary RF on ring electrode

V. excitation cycle (low energy CID): low amplitude supplementary RF voltage on endcaps

VI. mass analysis cycle (MS2):resonance ejection mode, high amplitude supplementary RF voltage on endcaps while scanning the amplitude of the fundamental RF voltage on the ring electrode

The trap as a tandem instrument


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Isolation and excitation can be carried out by scanning the resonant frequency or by a stored-waveform inverse Fourier transform (SWIFT) pulse.

Doroshenko, V.M.; Cotter, R.J., Rapid Commun. Mass Spectrom, 10 (1996) 65-73.

Mass isolation


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Capillary needle (3KV)

N2

Differentially pumped regions

Increasing vacuum

Capillary interface

Quadrupole, hexapole or octopole ion guides

Finnigan (Thermo) LCQ DUO/DECA; Bruker Esquire 4000/6000; Agilent LC/MSD 3D ion traps

Electrospray ionization and quadrupole ion trap

ESI is an atmospheric method, so that ions have to be transmitted into the vacuum and the trap


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Quadrupoles or hexapoles

Pulsed UV or IR laser

XY sample stage (3KV)

Extended capillary

Moyer, S. C. and Cotter, R.J., Atmospheric Pressure MALDI, Anal. Chem. 74 (2002) 468A–476A.

Mass Technologies AP MALDI source

Atmospheric pressure MALDI (APMALDI)

The capillary interface and RF-only multipole ion guides enable the use of any atmospheric pressure source


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800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 m/z0

100

Re

lativ

e A

bund

ance

1420.4

1274.1

1079.5

2117.3

1296.6787.1

2101.1

[M+Na]+

[M+Na]+

[M+Na]+

MAN6

A1F

M3N2F

800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 m/z0

100

Re

lativ

e A

bund

ance

1420.4

1274.1

1079.5

2117.3

1296.6787.1

2101.1

800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 m/z0

100

Re

lativ

e A

bund

ance

1420.4

1274.1

1079.5

2117.3

1296.6787.1

2101.1

[M+Na]+

[M+Na]+

[M+Na]+

MAN6

A1F

M3N2F

650 700 750 800 850 900 950 1000 1050 m/z0

100

Rel

ativ

e A

bund

ance

1061.4

933.3712.2

1062.3

978.4

979.5

714.4 917.4 1063.5980.4

916.2 969.2 1049.7730.0 1077.5686.7 1009.6899.9832.1 959.3629.1 772.0 801.8

MS/MS 1079Da

M3N2F -Fuc

-Fuc

-GlcNAc

-GlcNAc

650 700 750 800 850 900 950 1000 1050 m/z0

100

Rel

ativ

e A

bund

ance

1061.4

933.3712.2

1062.3

978.4

979.5

714.4 917.4 1063.5980.4

916.2 969.2 1049.7730.0 1077.5686.7 1009.6899.9832.1 959.3629.1 772.0 801.8

650 700 750 800 850 900 950 1000 1050 m/z0

100

Rel

ativ

e A

bund

ance

1061.4

933.3712.2

1062.3

978.4

979.5

714.4 917.4 1063.5980.4

916.2 969.2 1049.7730.0 1077.5686.7 1009.6899.9832.1 959.3629.1 772.0 801.8

MS/MS 1079Da

M3N2F -Fuc

-Fuc

-GlcNAc

-GlcNAc

MS/MS 1079Da

M3N2F -Fuc

-Fuc

-GlcNAc

-GlcNAc

650 700 750 800 850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400 m/z0

100

Re

lativ

e A

bun

danc

e

1198.5

1401.4

1318.41216.5

995.2 1036.51257.4

1095.5875.3 1115.3 1321.3723.1 833.2772.2 1157.3

MS/MS 1420Da

MAN6-Man

-Man-Man

-GlcNAc-GlcNAc

-GlcNAc-Man

650 700 750 800 850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400 m/z0

100

Re

lativ

e A

bun

danc

e

1198.5

1401.4

1318.41216.5

995.2 1036.51257.4

1095.5875.3 1115.3 1321.3723.1 833.2772.2 1157.3

650 700 750 800 850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400 m/z0

100

Re

lativ

e A

bun

danc

e

1198.5

1401.4

1318.41216.5

995.2 1036.51257.4

1095.5875.3 1115.3 1321.3723.1 833.2772.2 1157.3

MS/MS 1420Da

MAN6-Man

-Man-Man

-GlcNAc-GlcNAc

-GlcNAc-Man

AP/IRIS MS spectrum of 3-oligosaccharide mixture (8 pmol of each oligosaccharide)

Taranenko N.I., Atmospheric Pressure Infrared Ionization from Solutions (AP/IRIS), Proceedings of the 51st ASMS Conference on Mass Spectrometry and Allied Topics, Montreal, 2003.

Atmospheric pressure MALDI on an ion trap: examples of MS, MS/MS and MSn


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B. A. Collings, W. R. Stott and F. A. Londry, Resonant excitation in a low-pressure linear ion trap, J. Am. Soc. Mass Spectrom. 14 (2003) 622-634

Linear ion traps: the LTQ and the Q-trap

The Q-trap (MDS Sciex or Agilent) can be used as the third quadrupole in a triple quad (for MRM experiments) or as an ion trap for full scanned MSn spectra.

Axial ejection of ions


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Figure 1. Schematic portrayal of the experimental apparatus based on the ion path of a triple quadrupole mass spectrometer. Q3 can be operated as either an RF/DC quadrupole or a linear ion trap with mass selective axial ejection.

Figure 2. Generic scan function used for filling and scanning the Q3 linear ion trap mass spectrometer.

James W. Hager *, J. C. Yves Le Blanc, Product ion scanning using a Q-q-Qlinear ion trap (Q TRAPTM) mass spectrometer, Rapid Commun. Mass Spectrom. 17 (2003) 1056-1064

The Q-trap


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Linear ion traps: the Thermo LTQ

A major advantage of linear (2D) ion traps is that they can hold more ions than quadrupole (3D) ion traps.

This improves dynamic range, and reduces charge repulsion and shielding effects on mass resolution


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Linear ion traps: the Thermo LTQ

The LTQ loads ions axially,

but ejects or scans them out radially.

This becomes important for the addition of electron transfer dissociation (ETD), an orbitrap or an FTMS, all of which utilize axial movement of ions


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60 m3/hr 300 L/s 400 L/sec 210 L/sec 210 L/sec

Actively Shielded7 Tesla Magnet

Cold ECD< 2 eV

IRMPD Laser

15 L/s

ESI source

Transfer capillary and skimmer

Octapole ion guide

Quadrupole lenses

Octapole ion transfer lens

Linear ion trap

The Fourier-transform mass spectrometer


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In an ion cyclotron resonance (ICR) mass spectrometer, ions are confined in crossed electric and magnetic fields, where their resonant frequency depends upon the mass: ω = qB/m

Fourier transform mass spectrometry

210 L/sec 210 L/sec


Ions → Figure 1: Illustration of the Lorentz force (F=qvxB) as it acts on a positive ion (left) and a negative ion (right), in the presence of a constant magnetic field [ B].


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In the FTMS ions confined in an ICR cell are excited by a pulse representing a range of frequencies

8 MHz 100 kHz

RF frequency sweep

1. RF signal is applied to a set of excitation plates

2. Amplitude of ion oscillation increasesMagnetic field B

time

ω



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Only those frequencies that are absorbed resonantly will be returned as image currents

3. Image currents are detected on a pair of receiver plates

4. The transient decreases as the ions return to the center

5. The time-domain signal is Fourier transformed to a frequency domain mass spectrum

time

frequency (mass)

FFT



50

The FTMS provides very high mass resolution


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Mass selection: ions are ejected from the FTMS using high amplitude RF signal; mass selection is accomplished with a “notched” frequency sweep

8 MHz 100 kHz

RF frequency sweep

time

Excitation: low energy CID can be accomplished using low-level RF excitation

SORI: sustained off-resonance irradiation

MS/MS and MSn on the FTMS

Other excitation methods can also be used: infrared multi-photon dissociation (IRMPD) and electron capture dissociation (ECD)


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Cold ECD (< 2 eV)electron source

IRMPD Laser

IRMPD and ECD can be used on an FTMS

210 L/sec 210 L/sec


Ions →

IR laser radiation and/or thermal electrons are usually introduced opposite the ion introduction:


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Glycosylation sites:

Top Panel, Conventional CAD MS/MS results in no information about the location of O-GlcNAc.

Bottom Panel, ECD FTMS readily allows for site mapping O-GlcNAc.

ECD and post-translational modifications


• ECD produces mainly c and z-series ion

• ECD requires multiply-charged ions

How does ECD work?

1. Molecular ions are formed and trapped in the ICR cell2. One multiply-charged +ve ion species is mass selected3. Thermal electrons are focused into the ICR cell


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60 m3/hr 300 L/s 400 L/sec 210 L/sec 210 L/sec

Cold ECD< 2 eV

IRMPD Laser

15 L/s

ESI source


Octapole ion guide

Quadrupole lenses

Octapole ion transfer lens

Linear ion trap

The LTQ FTMS: low energy CID, ECD and IRMPD


ThermoFinnigan LTQ FTMS


The “orbitrap” mass analyzer

Figure 1. Cutaway view of the Orbitrap mass analyzer. Ions are injected into the Orbitrap at the point indicated by the red arrow. The ions are injected with a velocity perpendicular to the long axis of the Orbitrap (the z-axis). Injection at a point displaced from z = 0 gives the ions potential energy in the z-direction. Ion injection at this point on the z-potential is analogous to pulling back a pendulum bob and then releasing it to oscillate.

Hu Qizhi; Noll Robert J; Li Hongyan; Makarov Alexander; Hardman Mark; Graham Cooks R, The Orbitrap: a new mass spectrometer, J. Mass Spectrom 40 (2005) 430-43.

• invented by Alexander Makarov

• a purely electrostatic trap with no magnetic fields or RF electric fields

• image current detection and FT

• no MS/MS in the orbitrap


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The LTQ/orbitrap

1. mass selection for MSn‐1 stages takes place in the LTQ

3. the C‐trap focuses a linear ion beam to a point in the trap

2. Final product ions are ejected axially

4. The MSn spectrum is read out in high resolution on the orbitrap


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Figure 3. (a) Typical transient acquired to record the mass spectrum of bovine insulin. The transient acquired is equivalent to the free induction decay of FT NMR experiments. Top shows an expanded portion of the transient.

Hu Qizhi; Noll Robert J; Li Hongyan; Makarov Alexander; Hardman Mark; Cooks, R Graham, The Orbitrap: a new mass spectrometer, J. Mass Spectrom 40 (2005) 430-43.

The orbitrap is also an FTMS!

The image current signal is obtained in the time domain and is then converted by Fourier transform to the frequency domain and into a mass spectrum.


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ETD does not use free electrons but employs radical anions such as anthracene or azobenzene:

Electron transfer dissociation (ETD)

http://en.wikipedia.org/wiki/Electron_transfer_dissociation

60 m3/hr 300 L/s 400 L/sec15 L/s

ESI source


Octapole ion guide

Quadrupole lenses

Linear ion trap

Anions can be brought into the trap through the same or opposite side as the positive (sample) ion source


Ion activation in the LTQ/orbitrap configuration

ETD negative ion source

• Electron transfer dissociation (ETD)

• Collision induced dissociation (CID)

Ion activation and dissociation takes place in the LTQ


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Ion activation in the LTQ/orbitrap configuration: CID, higher energy CID (HCD) and ETD

Diagram of the Thermo LTQ Orbitrap VELOS with HCD collision cell

HCD collision cell provides higher energy collisions than the quadrupole cell. Advantage for iTRAQ global quantitation analyses


me 330.804: mass spectrometry in an “omics” world...• records an entire mass spectrum • best...

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