title: NMR-based molecular ruler for determining the depth of intercalants within the lipid bilayer Part I. Discovering the guidelines.
abstract: The development of "molecular rulers" would allow one to quantitatively locate intercalants within the liposomal bilayer. To this end, we have attempted to correlate the 13C NMR chemical shift of a polarizable "reporter" carbon (e.g., carbonyl) of the intercalant-with the ET30 polarity it experiences, and with its Angstrom distance from the interface. This requires families of molecules with the same two "reporter carbons" separated by a fixed distance, residing at various depths/polarities within the bilayer. The families studied included 4,4-dialkylcyclohexa-2,5-dienones 1, benzenediacetic esters 15, benzenedipropionic esters 17, 4-alkoxybenzaldehydes 19 and methyl 4-alkoxybenzoates 22. These compounds possessed the following characteristics: (1) a planar backbone; (2) polar/hydrophilic "head" groups; (3) modular hydrophobic tails; (4) large changes in the 13C NMR chemical shift (Deltadelta) of the reporter atoms with solvent polarity. These studies revealed a fifth requirement, namely: (5) the reporter carbons must not be strongly conjugated, lest it reflect the charge build-up at another site within the conjugated system.
authors.affiliation: Ethel and David Resnick Chair in Active Oxygen Chemistry, Bar-Ilan University, Ramat Gan 52900, Israel.
authors.forename: Yael
authors.initials: Y
authors.lastname: Cohen
authors.forename: Efrat
authors.initials: E
authors.lastname: Bodner
authors.forename: Michal
authors.initials: M
authors.lastname: Richman
authors.forename: Michal
authors.initials: M
authors.lastname: Afri
authors.forename: Aryeh A
authors.initials: AA
authors.lastname: Frimer
mesh_terms: D001547:Benzaldehydes / Q000032:analysis / Q000737:chemistry; D001565:Benzoates / Q000032:analysis / Q000138:chemical synthesis / Q000737:chemistry; D053138:Cyclohexenes / Q000032:analysis / Q000138:chemical synthesis / Q000737:chemistry; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D004952:Esters / Q000032:analysis / Q000138:chemical synthesis / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods* / Q000592:standards*
chemical_list: D001547:Benzaldehydes; D001565:Benzoates; D053138:Cyclohexenes; D004952:Esters; D008051:Lipid Bilayers; D008081:Liposomes; C507608:cyclohexadienone; C032175:benzaldehyde; D004134:Dimyristoylphosphatidylcholine