Investigation of anion binding to neutral lipid membranes using sup 2 H NMR

Journal Article · Tue Feb 04 00:00:00 EST 1992 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00119a018· OSTI ID:5616284

Rydall, J R; Macdonald, P M ^[1]

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1. Univ. of Toronto, Ontario (Canada)

The binding of aqueous anions (ClO{sub 4}{sup {minus}}, SCN{sup {minus}}, I{sup {minus}}, and NO{sub 3}{sup {minus}}) to lipid bilayer membranes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) was investigated using deuterium ({sup 2}H) and phosphorus-31 ({sup 31}P) nuclear magnetic resonance (NMR) spectroscopy. The ability of these anions to influence the {sup 2}H NMR quadrupole splittings of POPC, specifically labeled at the {alpha} or {beta} position of the choline head group, increased in the order NO{sub 3}{sup {minus}} << I{sup {minus}} < SCN{sup {minus}} < ClO{sub 4}{sup {minus}}. Calibration of the {sup 2}H NMR quadrupole splittings with the amount of membrane-bound anion permitted binding isotherms to be generated for perchlorate, thiocyanate, and iodide, up to concentrations of 100 mM. The binding isotherms were analyzed by considering electrostatic contributions, according to the Gouy-Chapman theory, as well as chemical equilibrium contributions. For neutral POPC membranes, the authors obtained ion association constants of 32, 80, and 115 M{sup {minus}1} for iodide, thiocyanate, and perchlorate, respectively. These values increase in the order expected for a Hofmeister series of anions. The authors conclude that the factor determining whether a particular anion will bind to lipid bilayers is the ease with which that anion loses its hydration shell. A comparison of the calibrated sensitivity of the {sup 2}H NMR quadrupole splitting to these and other ligands indicated that, in addition to charge, two factors dictate the level of the {sup 2}H NMR response: first, whether the ligand is cationic or anionic; and second, whether the ligand is predominantly hydrophobic or hydrophilic in nature. Both of these factors can be seen to arise from the details of the choline-tilt' model of the {sup 2}H NMR response to surface charges.

• OSTI ID: 5616284
• Journal Information: Biochemistry; (United States), Vol. 31:4; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
MEMBRANES
MOLECULAR STRUCTURE
PHOSPHOLIPIDS
NUCLEAR MAGNETIC RESONANCE
ANIONS
DEUTERIUM COMPOUNDS
LIGANDS
PHOSPHORUS 31
CHARGED PARTICLES
ESTERS
HYDROGEN COMPOUNDS
IONS
ISOTOPES
LIGHT NUCLEI
LIPIDS
MAGNETIC RESONANCE
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHORUS ISOTOPES
RESONANCE
STABLE ISOTOPES
550601* - Medicine- Unsealed Radionuclides in Diagnostics