title: Time-resolved molecular transport across living cell membranes.
abstract: It is shown that the nonlinear optical phenomenon known as second-harmonic generation can be used for label-free, time-resolved study of the transport of molecules through living cell membranes. The adsorption and transport of a 300-Da molecular-mass hydrophobic ion at the Escherichia coli membrane is observed. Remarkably, at low ion concentrations, the second-harmonic generation technique clearly exposes a multistep molecular transport process: Transport of the molecular ion across the outer and cytoplasmic membranes of the Gram-negative bacteria is recorded, in sequence, in time. Fitting of the data to a multiprocess kinematic model reveals that the transport of this hydrophobic ion through the outer membrane is much faster than through the cytoplasmic membrane, likely reflecting the effectiveness of ion transport porins. The observations illustrate an experimental means for studying the interactions of small molecules with cell membranes.
authors: Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors: Jia
authors: J
authors: Zeng
authors: Heather M
authors: HM
authors: Eckenrode
authors: Susan M
authors: SM
authors: Dounce
authors: Hai-Lung
authors: HL
authors: Dai
mesh_terms: D000327:Adsorption / Q000187:drug effects; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D004926:Escherichia coli / Q000166:cytology* / Q000187:drug effects; D007700:Kinetics; D016018:Least-Squares Analysis; D050296:Microbial Viability / Q000187:drug effects; D008954:Models, Biological; D017711:Nonlinear Dynamics; D012394:Rosaniline Dyes / Q000737:chemistry / Q000494:pharmacology; D013997:Time Factors
chemical_list: D012394:Rosaniline Dyes; C005095:malachite green