MALDI demonstration

Frímann, Helgi, Long, Nanna

Sample preperation

The sample of interest and matrix are dissolved in a volatile solvent

The sample/matrix/solvent mixture is then spotted on a metal plate

When the solvent has evaporated you can put your plate in to the vacuum

Anchor chips have hydrophilic area surrounded by hydrophobic ring

Matrix Assisted Laser Desorption/ Ionization

Introduced by M. Karas and F. Hillenkamp in 1985 [1]

Mainly used for large molecules Soft ionization The vibrational energy added to the analyte

molecule is about 4eV [2] The ions formed are typically: [M+H]+, [M+Na]+,

[M+K]+, [M+NH4]+ or [M-H]-

Ionization mechanism is not fully understood

TOF mass spectrometer

A TOF MS is usually (always?) used with MALDI

Reflectron TOF MSMS Microchannel plate electron multiplier (10000

electrons for each ion) MALDI-TOF “records”: ~300.000 amu,

attomoles of material

P2+

Target Reflector Reflectorplate detector

Line

ar d

etec

tor

Drift region

Two stage fieldstrength

Optical lenses

Ion source(PIE)

P1+

PCISIS1

IS1

/ IS

2G

roun

d

IS1

IS1 / IS2 Acc

eler

atio

npo

tent

ials

Ground

P1+

P1+

Parents andfragments

1SRef

1

2

3

4

4x10

Inte

ns.

[a.u

.]

2SRef

0.50

0.75

1.00

1.25

1.50

1.75

2.004x10

Inte

ns.

[a.u

.]

3SRef

0.5

0.6

0.7

0.8

0.9

4x10

Inte

ns.

[a.u

.]

4SRef

0.50

0.75

1.00

1.25

1.50

1.75

4x10

Inte

ns.

[a.u

.]

5SRef

4000

5000

6000

7000

8000

Inte

ns.

[a.u

.]

fast

2

4

6

4x10

Inte

ns.

[a.u

.]

800 1000 1200 1400 1600 1800

m/z

Electron multiplier

Measurements

• The data we have is from the protein BSA (Bovine serum albumin)

• We took linear spectra in the demostration

• Got the data from the peak at 927amu in MSMS mode

NH2

NH

NH

NH

OH

R1

O R2

O R3

O R4

O

a1 b1 c1

x3 y3 z3

a3 b3 c3a2 b2 c2

x1 y1 z1x2 y2 z2

NH2

NH

NH

NH

OH

R1

O R2

O R3

O R4

O

a1 b1 c1a1 b1 c1

x3 y3 z3x3 y3 z3

a3 b3 c3a3 b3 c3a2 b2 c2a2 b2 c2

x1 y1 z1x1 y1 z1x2 y2 z2x2 y2 z2

References

• [1] Karas, M.; Bachmann, D.; Hillenkamp, F. (1985). "Influence of the Wavelength in High-Irradiance Ultraviolet Laser Desorption Mass Spectrometry of Organic Molecules".Anal Chem 57: 2935–9

• [2] I. Bald, J. Kopyra and E. Illenberger, Angewandte Chemie-International Edition 45 (29), 4851-4855 (2006).