TY - JOUR
T1 - Studies on phosphatidylglycerol with triple quadrupole tandem mass spectrometry with electrospray ionization
T2 - Fragmentation processes and structural characterization
AU - Hsu, Fong Fu
AU - Turk, John
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.
PY - 2001
Y1 - 2001
N2 - Negative-ion low-energy collisionally activated dissociation (CAD) tandem mass spectrometry of electrospray-produced ions permits structural characterization of phosphatidylglycerol (PG). The major ions that identify the structures arise from neutral loss of free fatty acid substituents ([M - H - RxCO2H]-) and neutral loss of the fatty acids as ketenes ([M - H - RxCH = C = O]-), followed by consecutive loss of the glycerol head group. The abundances of the ions arising from neutral loss of the sn-2 substutient as a free fatty acid ([M - H - R2CO2H]-) or as a ketene ([M - H - R2CH = C = O]-) are greater than those of the product ions from the analogous losses at sn-1. Nucleophilic attack of the anionic phosphate site on the C-1 or the C-2 of the glycerol to which the carboxylates attached expels the sn-1 (R1CO2-) or the sn-2 (R2CO2-) carboxylate anion, resulting in a greater abundance of R2COO- than R1COO-. These features permit assignments of fatty acid substituents and their position in the glycerol backbone. The results are also consistent with our earlier findings that pathways leading to those losses at sn-2 are sterically more favorable than those at sn-1. Fragment ions at m/z 227, 209 and 171 reflect the glycerol polar head group and identify the various PG molecules. Both charge-remote fragmentation (CRF) and charge-drive fragmentation (CDF) processes are the major pathways for the formation of [M - H - RxCOOH]- ions. The CRF process involves participation of the hydrogen atoms on the glycerol backbone, whereas the CDF process involves participation of the exchangeable hydrogen atoms of the glycerol head group. The proposed fragmentation pathways are supported by CAD tandem mass spectrometry of the analogous precursor ions arising from the H-D exchange experiment, and further confirmed by source CAD in combination with tandem mass spectrometry.
AB - Negative-ion low-energy collisionally activated dissociation (CAD) tandem mass spectrometry of electrospray-produced ions permits structural characterization of phosphatidylglycerol (PG). The major ions that identify the structures arise from neutral loss of free fatty acid substituents ([M - H - RxCO2H]-) and neutral loss of the fatty acids as ketenes ([M - H - RxCH = C = O]-), followed by consecutive loss of the glycerol head group. The abundances of the ions arising from neutral loss of the sn-2 substutient as a free fatty acid ([M - H - R2CO2H]-) or as a ketene ([M - H - R2CH = C = O]-) are greater than those of the product ions from the analogous losses at sn-1. Nucleophilic attack of the anionic phosphate site on the C-1 or the C-2 of the glycerol to which the carboxylates attached expels the sn-1 (R1CO2-) or the sn-2 (R2CO2-) carboxylate anion, resulting in a greater abundance of R2COO- than R1COO-. These features permit assignments of fatty acid substituents and their position in the glycerol backbone. The results are also consistent with our earlier findings that pathways leading to those losses at sn-2 are sterically more favorable than those at sn-1. Fragment ions at m/z 227, 209 and 171 reflect the glycerol polar head group and identify the various PG molecules. Both charge-remote fragmentation (CRF) and charge-drive fragmentation (CDF) processes are the major pathways for the formation of [M - H - RxCOOH]- ions. The CRF process involves participation of the hydrogen atoms on the glycerol backbone, whereas the CDF process involves participation of the exchangeable hydrogen atoms of the glycerol head group. The proposed fragmentation pathways are supported by CAD tandem mass spectrometry of the analogous precursor ions arising from the H-D exchange experiment, and further confirmed by source CAD in combination with tandem mass spectrometry.
UR - http://www.scopus.com/inward/record.url?scp=0035561115&partnerID=8YFLogxK
U2 - 10.1016/S1044-0305(01)00285-9
DO - 10.1016/S1044-0305(01)00285-9
M3 - Article
AN - SCOPUS:0035561115
SN - 1044-0305
VL - 12
SP - 1036
EP - 1043
JO - Journal of the American Society for Mass Spectrometry
JF - Journal of the American Society for Mass Spectrometry
IS - 9
ER -