CHCA-Modified Au Nanoparticles for Laser Desorption Ionization Mass Spectrometric Analysis

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CHCA-Modified Au Nanoparticles for Laser Desorption Ionization Mass Spectrometric Analysis of Peptides

Jicheng Duan, Matthew J. Linman, Chih-Yuan Chen and Quan Cheng*

Department of Chemistry

University of California

Riverside, California 92521

*Corresponding author: Quan Cheng, Tel: (951) 827-2702

Email: Fax: (951) 827-4713


Figure S1. UV-Vis absorption spectra for different reagent-capped AuNPs.


Figure S2. Comparison of fragment intensities from LDI-MS analysis of peptides with CHCA-terminated AuNPs under various conditions.


Figure S3. LDI-MS spectra for peptides obtained from samples containing 2 mM citric acid and 5% glycerol with (a) untreated, citrate-capped AuNPs, (b) cysteamine-capped AuNPs and (c) CHCA-terminated AuNPs. Au cluster ions were marked by asterisks.


Figure S4. Effect of citric acid concentration on LDI-MS analysis of the peptides.


Figure S5. Effect of glycerol content on LDI-MS analysis of the peptides.

Table S1. Comparison of LDI-MS analysis of peptides with CHCA-terminated AuNPs assisted with different acids and ammonium salts with and without glycerola
Additives / Ion intensity (´103 counts)
[M1+H]+ / [M1+Na]+ / [M1+K]+ / [M2+H]+ / [M2+Na]+ / [M2+K]+
without glycerol
0.1% TFA / 1.7 / 1.7 / 3.1 / 0.77 / 0.51 / -
2 mM HAcb / 3.9 / 1.6 / 1.4 / 0.69 / - / -
2 mM CAc / - / 3.7 / 27 / 0.69 / 1.1 / 2.8
2 mM NH4Ac / 1.5 / 2.0 / 2.2 / 0.69 / 0.58 / 0.29
2 mM NH4CA / 8.2 / 8.2 / 11 / 9.6 / 4.7 / 3.0
with 5% glycerol
0.1% TFA / 15 / 47 / 26 / 1.8 / 4.8 / 1.7
2 mM HAc / 6.2 / 28 / 35 / 1.8 / 4.0 / 3.6
2 mM CA / 20 / 18 / 20 / 9.8 / 3.5 / 1.8
2 mM NH4Ac / 13 / 30 / 23 / 1.0 / 2.6 / 1.6
2 mM NH4CA / 10 / 8.3 / 2.9 / 7.3 / 3.4 / 0.42
a: 1 mL sample solution on stainless steel plate, M1 and M2 are [Sar1, Thr8]-angiotensin II and neurotensin, respectively, 20 pmol each in sample spots. b: HAc is acetic acid; c: CA is citric acid .
Table S2. Effect of AuNP content in matrix on SALDI-MS analysis of peptides
Concentration of matrixa / Ion intensity (´103 counts)
[M1b +H]+ / [M1+Na]+ / [M1+K]+ / [M2 c+H]+ / [M2+Na]+ / [M2+K]+
AuNPs (nM)
1.6 / 9.1 / 1.6 / 0.37 / 6.5 / 0.69 / 0.62
3.8 / 25 / 5.0 / 2.1 / 16 / 2.6 / 1.6
7.6 / 27 / 5.5 / 2.2 / 16 / 3.4 / 1.4
15.4 / 33 / 8.3 / 4.1 / 18 / 4.4 / 2.2
24.5 / 45 / 18 / 5.8 / 22 / 6.8 / 2.1
CHCA (mM)
~50 / 19 / 6.9 / 1.9 / 14 / 6.5 / 2.5
a: 1 mL sample solution on stainless steel plate; b: M1 is [Sar1, Thr8]-angiotensin II (MW = 956.1), 20 pmol; c: M2 is neurotensin (MW = 1672), 20 pmol.
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