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Article

Detection of In Situ Derivatized Peptides in Microbial Biofilms by Laser Desorption 7.87 eV Postionizaton Mass Spectrometry

Supporting Info

Praneeth D. Edirisinghe,^† Jerry F. Moore,^‡ Kelly A. Skinner-Nemec,^§ Carl Lindberg,^§ Carol S. Giometti,^§ Igor V. Veryovkin, Jerry E. Hunt, Michael J. Pellin, and Luke Hanley*^†

Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607-7061, Materials Science, Chemistry, and Biological Sciences Divisions, Argonne National Laboratory, Argonne, Illinois 60439, and MassThink, Naperville, Illinois 60565-3123

Anal. Chem., 2007, 79 (2), pp 508–514

DOI: 10.1021/ac0615605

Publication Date (Web): December 9, 2006

†

University of Illinois at Chicago.

‡

MassThink.

Biological Sciences Divisions, Argonne National Laboratory.

Materials Science, Argonne National Laboratory.

Chemistry, Argonne National Laboratory.

Corresponding author. E-mail: lhanley@uic.edu.

Abstract

A novel analytical method based on laser desorption postionization mass spectrometry (LDPI-MS) was developed to investigate the competence and sporulation factora pentapeptide of amino acid sequence ERGMTwithin intact Bacillus subtilis biofilms. Derivatization of the neat ERGMT peptide with quinoline- and anthracene-based tags was separately used to lower the peptide ionization potential and permit direct ionization by 7.87-eV vacuum ultraviolet radiation. The techniques of mass shifting and selective ionization of the derivatized peptide were combined here to permit detection of ERGMT peptide within intact biofilms by LDPI-MS, without any prior extraction or chromatographic separation. Finally, imaging MS specific to the derivatized peptide was demonstrated on an intact biofilm using LDPI-MS. The presence of ERGMT in the biofilms was verified by bulk extraction/LC−MS. However, MALDI imaging MS analyses were unable to detect ERGMT within intact biofilms.