Aluminum binding to phosphatidylcholine lipid bilayer membranes: 27Al and 31P NMR spectroscopic studies.
27Al and 31P nuclear magnetic resonance (NMR) spectroscopies were used to investigate aluminum interactions at pH 3.4 with model membranes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). A solution state 27Al NMR difference assay was developed to quantify aluminum binding to POPC multilamellar vesicles (MLVs). Corresponding one-dimensional (1D) fast magic angle spinning (MAS) 31P NMR spectra showed that aluminum induced the appearance of two new isotropic resonances for POPC shifted to -6.4 ppm and -9.6 ppm upfield relative to, and in slow exchange with, the control resonance at -0.6 ppm. Correlation of the (27)Al and (31)P NMR binding data revealed a 1:2 aluminum:phospholipid stoichiometry in the aluminum-bound complex at -9.6 ppm and a 1:1 aluminum:phospholipid stoichiometry in that at -6.4 ppm. Slow MAS 31P NMR spectra demonstrated shifts in the anisotropic chemical shift tensor components of the aluminum-bound POPC consistent with a close coordination of aluminum with phosphorus. A model of the aluminum-bis-phospholipid complex is proposed on the basis of these findings.
MacKinnon
Neil
N
Department of Chemical and Physical Sciences, University of Toronto at Mississauga, 3359 Mississauga Road, Mississauga, Ont., Canada L5L 1C6.
Crowell
Kevin J
KJ
Udit
Andrew K
AK
Macdonald
Peter M
PM
D000535:Aluminum / Q000737:chemistry*; D001665:Binding Sites; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008567:Membranes, Artificial; D008956:Models, Chemical; D008958:Models, Molecular; D010713:Phosphatidylcholines / Q000737:chemistry*; D010761:Phosphorus Radioisotopes
D008051:Lipid Bilayers; D008081:Liposomes; D046911:Macromolecular Substances; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D010761:Phosphorus Radioisotopes; D000535:Aluminum; C028694:1-palmitoyl-2-oleoylphosphatidylcholine