title: Lateral distribution of a poly(ethylene glycol)-grafted phospholipid in phosphocholine monolayers studied by epifluorescence microscopy.
abstract: Mixed monolayers of distearoylphosphatidylcholine (DSPC) and a poly(ethylene glycol)-(PEG)-grafted distearoylphosphatidylethanolamine with a PEG molecular weight of 2000, DSPE-PEG2000, spread on phosphate-buffered saline (PBS) were used as models of bio-non-fouling membrane-mimetic surfaces in order to visualize the lateral distribution of PEG2000-phospholipid in the host phospholipid matrix. Epifluorescence microscopy (EFM) was used to locate DSPE-PEG2000 molecules in the DSPC matrix by detecting the fluorescence from a fluorescein fluorophore attached to the distal end of the PEG2000 chain. Comparative analysis of surface pressure-area isotherms and EFM images revealed that DSPE-PEG2000 mixes nonideally with DSPC in monolayers on a PBS subphase. A transition from a phase-separated monolayer to a homogeneous mixture was observed with increasing surface pressure and PEG content. The effect of nonideal mixing behavior of DSPE-PEG2000 on its lateral distribution in the DSPC matrix was interpreted in terms of excluded volume interactions between the PEG2000 chains and a mismatch in the tilt of aliphatic chains on DSPC and DSPE-PEG2000 molecules.
authors.affiliation: Department of Chemistry, York University, Toronto, Ontario, Canada M3J 1P3.
authors.forename: Kanwal
authors.initials: K
authors.lastname: Tanwir
authors.forename: Valeria
authors.initials: V
authors.lastname: Tsoukanova
mesh_terms: D002021:Buffers; D008855:Microscopy, Electron, Scanning; D008856:Microscopy, Fluorescence; D015394:Molecular Structure; D010710:Phosphates / Q000737:chemistry; D010713:Phosphatidylcholines / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D011312:Pressure; D013499:Surface Properties
chemical_list: D002021:Buffers; D010710:Phosphates; D010713:Phosphatidylcholines; D010743:Phospholipids; D011092:Polyethylene Glycols; C010942:1,2-distearoyllecithin