TY - JOUR
T1 - Characterization of mycolic acids from the pathogen Rhodococcus equi by tandem mass spectrometry with electrospray ionization
AU - Hsu, Fong Fu
AU - Soehl, Kristina
AU - Turk, John
AU - Haas, Albert
N1 - Funding Information:
This research was supported by US Public Health Service Grants P41-RR-00954, R37-DK-34388, P60-DK-20579, P01-HL-57278, and P30-DK56341 as well as by Deutsche Forschungsgemeinschaft (SFB 670).
PY - 2011/2/1
Y1 - 2011/2/1
N2 - We describe a simple tandem mass spectrometric approach toward structural characterization of mycolic acids, the long-chain α-alkyl-β-hydroxy fatty acids unique to mycobacteria and related taxa. On collisionally activated dissociation in a linear ion trap or tandem quadrupole mass spectrometer, the [M-H]- ions of mycolic acid generated by electrospray ionization undergo dissociation to eliminate the meroaldehyde residue, leading to formation of carboxylate anions containing α-alkyl chains. The structural information from these fragment ions affords structural assignment of the mycolic acids, including the lengths of the meromycolate chain and the α-branch. This study revealed that the mycolic acids isolated from pathogenic Rhodococcus equi 103 contained a series of homologous ions having C30 to C50 chain with 0-2 double bonds. The α-branch ranged from C10 to C18 with 0 to 1 double bond, in which 16:0 and 14:0 are the most prominent, whereas the meromycolate chain ranged from C14 to C34 with 0 to 2 double bonds. The major molecular species consisted of more than 3 isomers that differ by the lengths of the α-branch or meromycolate chain, and up to 10 isobaric isomers were identified for some minor ions. We also employed tandem quadrupole mass spectrometry with precursor ion and neutral loss scans for profiling mycolic acid with specific structure in mixtures. The tandem spectra obtained from precursor ion scans of m/z 255 (16:0-carboxylate anion) and m/z 227 (14:0-carboxylate anion) may provide a simple specific means for classification of Rhodococci species, whereas tandem spectra from neutral loss of meroaldehyde residue scans provided a simple approach to reveal the mycolic acid molecules with specific meromycolate chain in mixtures.
AB - We describe a simple tandem mass spectrometric approach toward structural characterization of mycolic acids, the long-chain α-alkyl-β-hydroxy fatty acids unique to mycobacteria and related taxa. On collisionally activated dissociation in a linear ion trap or tandem quadrupole mass spectrometer, the [M-H]- ions of mycolic acid generated by electrospray ionization undergo dissociation to eliminate the meroaldehyde residue, leading to formation of carboxylate anions containing α-alkyl chains. The structural information from these fragment ions affords structural assignment of the mycolic acids, including the lengths of the meromycolate chain and the α-branch. This study revealed that the mycolic acids isolated from pathogenic Rhodococcus equi 103 contained a series of homologous ions having C30 to C50 chain with 0-2 double bonds. The α-branch ranged from C10 to C18 with 0 to 1 double bond, in which 16:0 and 14:0 are the most prominent, whereas the meromycolate chain ranged from C14 to C34 with 0 to 2 double bonds. The major molecular species consisted of more than 3 isomers that differ by the lengths of the α-branch or meromycolate chain, and up to 10 isobaric isomers were identified for some minor ions. We also employed tandem quadrupole mass spectrometry with precursor ion and neutral loss scans for profiling mycolic acid with specific structure in mixtures. The tandem spectra obtained from precursor ion scans of m/z 255 (16:0-carboxylate anion) and m/z 227 (14:0-carboxylate anion) may provide a simple specific means for classification of Rhodococci species, whereas tandem spectra from neutral loss of meroaldehyde residue scans provided a simple approach to reveal the mycolic acid molecules with specific meromycolate chain in mixtures.
KW - Electrospray ionization
KW - Mycolic acids
KW - Rhodococcus equi
KW - Rhodococcus rhodnii
KW - Rhodococcus terrace
KW - Tandem mass spectrometry
KW - α-Alkyl-β-hydroxy fatty acids
UR - http://www.scopus.com/inward/record.url?scp=78650288400&partnerID=8YFLogxK
U2 - 10.1016/j.ab.2010.10.006
DO - 10.1016/j.ab.2010.10.006
M3 - Article
C2 - 20946862
AN - SCOPUS:78650288400
SN - 0003-2697
VL - 409
SP - 112
EP - 122
JO - Analytical Biochemistry
JF - Analytical Biochemistry
IS - 1
ER -