Supplementary Material s88

Supplementary Material

Expansion Cooling in the Matrix Plume is Under-Recognized in MALDI Mass Spectrometry

Yong Jin Baea, Jeong Hee Moonb, and Myung Soo Kima,[*]

aDepartment of Chemistry, Seoul National University, Seoul 151-742, Korea

bMedical Proteomics Research Center, KRIBB, Daejeon 305-806, Korea

1. Influence of laser pulse energy and delay time on YISD and YPSD in UV-MALDI

of Y6 with SA

Figure S1. Laser pulse energy dependence of (a) YISD and (b) YPSD in UV-MALDI of Y6 with SA. Abscissa is the relative pulse energy, i.e., pulse energy divided by the threshold value (1.1 μJ/pulse).

Figure S2. (a) YISD and (b) YPSD measured as a function of delay time (±20 ns accuracy) in UV-MALDI of Y6 with SA. Laser energy was 1.65 μJ/pulse.

2. Influence of laser pulse energy and delay time on YISD in IR-MALDI of Y6 with glycerol.

Figure S3. Relative abundance (YISD) of y5 vs. (a) laser pulse energy and (b) delay time in IR-MALDI. Laser pulse energy used in (b) corresponds to 1.5 times the threshold.

3. Estimation of the temperatures of [Y6 + H]+ in early and late plumes – SA as an

example

Figure S4. (a) Total dissociation rate constant, k(E), of [Y6 + H]+ calculated with (E0, ΔS‡) of (0.60 eV, -28.4 eu) determined previously [S1, S2]. Threshold rate constants and energies for ISD and PSD are marked. Internal energy distributions in early (– – –) and late (·····) SA plumes are shown in the bottom. The effective temperature in each case was determined by equating the area below the threshold energy with the survival probability. The ordinates in the left and right are those for k(E) and energy distribution, respectively. (b) Calculations with (E0, ΔS‡) of (0.90 eV, -14.2 eu). k(E) thus obtained is incompatible with the photodissociation rate constants measured previously. The method to calculate k(E) and internal energy distribution is in ref. S3.

References

S1. Moon, J. H.; Yoon, S. H.; Kim. M. S. Temperature of Peptide Ions Generated by Matrix-Assisted Laser Desorption Ionization and Their Dissociation Kinetic Parameters. J. Phys. Chem. B 2009, 113, 2071-2076.

S2. Yoon, S. H.; Moon, J. H.; Kim, M. S. Time-Resolved Photodissociation Study of Singly Protonated Peptides with a Histidine Residue Generated by Matrix-Assisted Laser Desorption Ionization: Dissociation Rate Constant and Internal Temperature. J. Am. Soc. Mass Spectrom. 2009, 20, 1522-1529.

S3. Moon, J. H.; Oh, J. Y.; Kim, M. S. A Systematic and Efficient Method to Estimate the Vibrational Frequencies of Linear Peptide and Protein Ions with Any Amino Acid Sequence for the Calculation of Rice-Ramsperger-Kassel-Marcus Rate Constant. J. Am. Soc. Mass Spectrom. 2006, 17, 1749-1757.

S6

[*] Correspondence to: Prof. Myung Soo Kim, Department of Chemistry, Seoul National University, Seoul 151-742, Korea. E-mail address: