Two-Dimensional Center-of-Mass Diffusion of Lipid-Tethered Poly(2-methyl-2-oxazoline) at the Air–Water Interface Studied at the Single Molecule Level

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• 作者：Karin L&#xfc ; dtke ; Rainer Jordan ; Nathan Furr ; Sumit Garg ; Kelsey Forsythe ; Christoph A. Naumann
• 刊名：Langmuir
• 出版年：2008
• 出版时间：May 20, 2008
• 年：2008
• 卷：24
• 期：10
• 页码：5580 - 5584
• 全文大小：114K
• 年卷期：v.24,no.10(May 20, 2008)
• ISSN：1520-5827

文摘

The two-dimensional (2D) center-of-mass diffusion, D, of end-tethered poly(2-methyl-2-oxazoline) (PMOx) lipopolymer chains was studied in a Langmuir monolayer at the air–water interface using wide-field single molecule fluorescence microscopy. In this case, tethering and stabilization of hydrophilic PMOx chains at the air–water interface is accomplished via end-tethering to lipid molecules forming a hydrophobic anchor. To explore the influence of molecular weight, M_n, and surface concentration, c_s, on lateral mobility, two different PMOx chain lengths of n = 30 and 50 (n, number of monomer units) were analyzed over a wide range of c_s. Using multiparticle tracking analysis of TRITC-labeled PMOx lipopolymers, we found two regimes of lipopolymer lateral mobility. At low c_s, D is independent of surface concentration but increases with decreasing n. Here diffusion properties are well described by the Rouse model. In contrast, at more elevated c_s, the data do not follow Rouse scaling but are in good agreement with a free area−area model of diffusion. The current study provides for the first time experimental insight into the 2D center-of-mass diffusion of end-tethered polymers at the air–water interface. The obtained results will be of importance for the understanding of diffusion processes in polymer-tethered phospholipid bilayers mimicking biomembranes at low and high tethering concentrations.