gold nanoparticles as an inorganic matrix for maldi - inside mines
TRANSCRIPT
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Gold Nanoparticles as an Inorganic Matrix for MALDI-TOF Mass Spectrometry of Low
Molecular Weight Polymers
Justin R. Engle and S. Kim R. Williams
Laboratory for Advance Separations TechnologiesDepartment of Chemistry and Geochemistry
Colorado School of MinesGolden, Colorado
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MALDI-TOF sample preparation
2,5-dihydroxybenzoic acid(DHB)
+
Deposition
OH
OHOH
O
MatrixAnalyte
Hn
Polystyrene (PS) 800
Mw 826
Mn 726
Polyethylene glycol (PEG) 700
HO
OHn Mw 700
Mn 645
Salt+
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MALDI-TOF schematic
Applied Biosystems. Perseptive Biosystems Voyager DE-STR. Version 5.1 2001.
Perseptive Biosystem Voyager DE-STR with delay extraction option
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Laser desorption/ionization process
•Matrix in higher concentration than analyte and salt
-Absorbs laser energy
-Transfers energy to analyte
•Multiple ionization processes at ablation site and in plume
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0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 0 1 5 0 00
2 0 0 0 0
Rel
ativ
e In
tens
ity U
nits
m / z
P S - A g +
e n d g r o u p s : t - b u ty l a n d H +
P S - K +
e n d g r o u p s : t - b u ty l a n d O H -
n = 71 0 4m /z
0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 0 1 5 0 00
7 0 0 0 0
DHB + PS 800 + AgTFAR
elat
ive
Inte
nsity
Uni
ts
m / z
P S - A g + ( n = 4 ,5 )e n d g r o u p s : t - b u t y l a n d H +
P S - A u + ( n = 3 ,4 )e n d g r o u p s : t - b u t y l a n d H +
P S - C u + ( n = 4 ,5 )e n d g r o u p s : t - b u t y l a n d H +
1 0 4m /z
Stainless Steel MALDI Plate
Gold MALDI Plate
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0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 0 1 5 0 00
6 0 0 0 0
Rel
ativ
e In
tens
ity U
nits
m / z
n = 1 6
4 4 m /z
P E G - N a +
e n d g r o u p s : O H - a n d H +
P E G - L i+
e n d g r o u p s : O H - a n d H +
P E G - A g +
e n d g r o u p s : O H - a n d H +
0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 0 1 5 0 00
3 0 0 0 0
m / z
P E G - N a +
e n d g r o u p s : O H - + H +
P E G - K +
e n d g r o u p s : O H - a n d H +
P E G - H +
e n d g r o u p s : O H - a n d H +
P E G - L i +
e n d g r o u p s : O H - a n d H +
P E G - A g +
e n d g r o u p s : O H - a n d H +
n = 1 4
4 4 m / z
Rel
ativ
e In
tens
ity U
nits
Stainless Steel MALDI Plate
Gold MALDI Plate
DHB + PEG 700 + NaTFA
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Traditional approach results• Complicated mass spectra below 1000 Da• Multiple unexplainable mass peaks
Result from fragmentation of organic matrix
• Incomplete mass series for PSPS on
Stainless Steel
PS on Gold
PEG on Stainless
Steel
PEG on Gold
Calc Mw 945 ± 65 692 ± 34 671 ± 25 646 ± 35
Calc Mn 862 ± 53 647 ± 25 631 ± 18 603 ± 28
Averages and deviation taken from at least 5 different spectra
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Objectives
• Replace organic matrix with gold nanoparticles (AuNP)
Reduce number of mass peaks below 1000 Da• Investigate difference in sample plates
Stainless steel and gold MALDI plates• Determine reproducibility• Calculate molecular weight averages
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Gold nanoparticlesUsed in numerous fields– Absorbs light below 400 nm (UV range) – Fluorescence of light energy after excitation
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
190 290 390 490 590 690 790
Wavelength (nm)
Abs
orba
nce
(uni
ts)
AuNP (d=10nm)AuNP (d=5.3nm)
337 nm
Absorption band:spherical gold nanoparticles
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Sample preparationAnalyte 5 mg/mLSalt 5 mg/mLAuNPs d=5.3 nm; d=10nm
from Corpuscular (Cold Spring, NY)
Mixed in 1:1:1 (v/v)PS-Ag+; PEG-Na+
0.5 μL spot volumes on either stainless steel or gold MALDI plates
Instrument settings:Acceleration voltage: 25,000 vDelay extraction time:100 ns Grid voltage: 96%Laser intensity: 1926 units
Software analysis:Data Explorer (PerSeptiveBiosystems, Farmington, MA)Polymerix (Sierra Analytics, Modesto, CA)
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AuNP assisted laser desorption/ionization
• AuNPs absorb laser energy, emit light energy to analyte and/or salt
• Fewer particle interactions
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Stainless steel and gold MALDI plates
0 250 500 750 10000
30000
Rel
ativ
e In
tens
ity U
nits
m/z
0 250 500 750 10000
30000
Rel
ativ
e In
tens
ity U
nits
m/z
Cleaned using tetrahydrofuran, 6M nitric acid, DI water, and acetone (in order)
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0 250 500 750 10000
35000
Rel
ativ
e In
tens
ity U
nits
m/z
Salts (Li+, Na+)
AuNPs on MALDI platesd=5.3nm on stainless steel plate
d =5.3nm on gold plate d =10nm on gold plate
0 250 500 750 10000
35000
Rel
ativ
e In
tens
ity U
nits
m/z
Salts (Li+, Na+, K+)
Au+
Au+2
d=10nm on stainless steel plate
0 250 500 750 10000
35000
Rel
ativ
e In
tens
ity U
nits
m/z
Salts (Li+, Na+)
Au+
0 250 500 750 10000
35000
Rel
ativ
e In
tens
ity U
nits
m/z
Salts (Li+, Na+)
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AuNPs, PS 800, AgTFAon Stainless Steel
0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 0 1 5 0 0 1 7 5 0 2 0 0 00
1 5 0 0 0
Rel
ativ
e In
tens
ity U
nits
m / z
A g +
A u +
n = 8 1 0 4 m / z
P S - A g +
E n d g r o u p s : H + a n d t - b u t y lAuNP (d=10nm)
0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 0 1 5 0 0 1 7 5 0 2 0 0 00
6 0 0 0 0
Rel
ativ
e In
tens
ity U
nits
m / z
A g +
P S - A g +
E n d G r o u p s : H + a n d t - b u t y l
P S - N a +
E n d G r o u p s : H + a n d t - b u t y l
n = 8
n = 7
1 0 4 m / z
AuNP (d=5.3nm)
Hn
Polystyrene
Hn
Polystyrene
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AuNPs, PS 800, AgTFAon gold plate
0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 0 1 5 0 0 1 7 5 0 2 0 0 00
3 2 5 0 0
Rel
ativ
e In
tens
ity U
nits
m /z
P S -A g +
E n d g r o u p s : H + a n d t - b u ty l
n = 81 0 4 m /z
0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 0 1 5 0 0 1 7 5 0 2 0 0 00
1 5 0 0 0
Rel
ativ
e In
tens
ity U
nits
m /z
P S - A g +
E n d g r o u p s : H + a n d t - b u ty l
A g +A g +
2
A g +3
n = 8 1 0 4 m /z
Hn
Polystyrene
Hn
Polystyrene
AuNP (d=10nm)
AuNP (d=5.3nm)
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AuNPs, PEG 700, NaTFAon stainless steel
0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 00
2 2 5 0 0
Rel
ativ
e In
tens
ity U
nits
m / z
n = 1 44 4 m /z
P E G - N a +
E n d g r o u p s : H + a n d O H -
P E G - K +
E n d g r o u p s : H + a n d O H -
P E G - L i+
E n d g r o p u s : H + a n d O H -
0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 00
5 0 0 0 0
Rel
ativ
e In
tens
ity U
nits
m / z
P E G - N a +
E n d g r o u p s : H + a n d O H -
P E G - K +
E n d g r o u p s : H + a n d O H -
P E G - L i+
E n d g r o p u s : H + a n d O H -
n = 1 4
4 4 m / zH O
OHn
Polyethylene glycol
H OOHn
Polyethylene glycol
AuNP (d=10nm)
AuNP (d=5.3nm)
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AuNPs, PEG 700, NaTFAon gold plate
0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 00
2 0 0 0 0
Rel
ativ
e In
tens
ity U
nits
m /z
n = 1 4 4 4 m /z
P E G - N a +
E n d g r o u p s : H + a n d O H -
P E G - K +
E n d g r o u p s : H + a n d O H -
P E G - L i +
E n d g r o p u s : H + a n d O H -
0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 00
2 0 0 0 0
Rel
ativ
e In
tens
ity U
nits
m / z
n = 1 4 4 4 m / z
P E G - N a +
E n d g r o u p s : H + a n d O H -
P E G - K +
E n d g r o u p s : H + a n d O H -
P E G - L i +
E n d g r o p u s : H + a n d O H -
H OOHn
Polyethylene glycol
H OOHn
Polyethylene glycol
AuNP (d=10nm)
AuNP (d=5.3nm)
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Reproducibility
0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 0 1 5 0 0 1 7 5 0 2 0 0 00
6 0 0 0 0
Rel
ativ
e In
tens
ity U
nits
0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 0 1 5 0 0 1 7 5 0 2 0 0 00
6 0 0 0 0
Rel
ativ
e In
tens
ity U
nits
0 2 5 0 5 0 0 7 5 0 1 0 0 0 1 2 5 0 1 5 0 0 1 7 5 0 2 0 0 00
6 0 0 0 0
Rel
ativ
e In
tens
ity U
nits
m / z
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Calculated molecular weightsPS
Mw = 826Mn = 726
AuNP(d=5nm)Stainless
Steel
AuNP(d=10nm)Stainless
Steel
AuNP(d=5nm)
Gold plate
AuNP(d=10nm)Gold plate
Mw 816 ± 6 835 ± 27 826 ± 8 791 ± 7
683 ± 3Mn 717 ± 2 725 ± 16 725 ± 6
PEGMw = 700Mn = 645
AuNP(d=5nm)Stainless
Steel
AuNP(d=10nm)Stainless
Steel
AuNP(d=5nm)
Gold plate
AuNP(d=10nm)Gold plate
Mw 608 ± 6 688 ± 46 684 ± 18 654 ± 28
609 ± 34 Mn 567 ± 6 638 ± 36 633 ± 16
Averages and deviation taken from at least 5 different spectra
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Conclusions
• AuNPs promoted desorption/ionization of low molecular weight polymers
• Limited background interference• Reproducible results• “Best” results obtained with specific mixtures
– Polystyrene• AuNP (d=10nm) on stainless steel plate• AuNP (d=5.3nm) on gold plate
– Polyethylene Glycol• AuNP (d=5.3nm) on gold plate
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Acknowledgments• NSF-CHE-0515521• Williams Group
– Dr. Dean Lee – Dr. Ilyong Park– Dr. Claudia Lohmann– J. Ray Runyon – Adam Goering