Year: 2009
Type: article
Abstract: Quantifying and controlling the orientation of surface-bound macromolecules is crucial to a wide range of processes in areas as diverse as biology, materials science, and nanotechnology. Methods capable of directing orientation, as well as an understanding of the underlying physical mechanisms are, however, lacking. In this paper, we describe experiments in which the conformations of structurally well-defined polymers anchored to fluid lipid membranes were probed using Fluorescence Interference Contrast Microscopy (FLIC), an optical technique that provides topographic information with few-nanometer precision. The novel rodlike polymers mimic the architecture of mucin glycoproteins and feature a phospholipid tail for membrane incorporation and a fluorescent optical probe for FLIC imaging situated at the opposite termini of the densely glycosylated polymeric backbones. We find that the orientation of the rigid, approximately 30 nm long glycopolymers depends profoundly on the properties of the optical reporter. Molecules terminated with Alexa Fluor 488 projected away from the lipid bilayer by 11 +/- 1 nm, consistent with entropy-dominated sampling of the membrane-proximal space. Molecules terminated with Texas Red lie flat at the membrane (height, 0 +/- 2 nm), implying that interactions between Texas Red and the bilayer dominate the polymers' free energy. These results demonstrate the design of macromolecules with specific orientational preferences, as well as nanometer-scale measurement of their orientation. Importantly, they reveal that seemingly minute changes in molecular structure, in this case fluorophores that comprise only 2% of the total molecular weight, can significantly alter the molecule's presentation to the surrounding environment.
DOI: 10.1021/ja903114g
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
Funders: National Science Foundation, Howard Hughes Medical Institute, U.S. Department of Energy, Alfred P. Sloan Foundation, National Institutes of Health, Office of Science, U.S. Public Health Service, National Institute of General Medical Sciences, Division of Chemistry, Basic Energy Sciences, Lawrence Berkeley National Laboratory
Awards: G1079818582, G1143651532, G1206721254, G1286236842, G1286251239, G1398330795, G1614572836, G1643223109, G1863003419, G193590374, G2787076192, G301008592, G3083819904, G3444594369, G382641700, G419881185, G4501827968, G498139845, G5004724115, G5094606986, G650090426, G6652958823, REU Site: Interdisciplinary Research Experience for Undergraduates in Chemistry and Physics at the University of Oregon, G7354628648, G7444770027, Chemical Cell Surface Engineering, G8099852790, G969889393
OpenAlex ID: W1999182279