University of Wisconsin-Madison NSEC: Templated Synthesis and Assembly at the Nanoscale

1. Thrust 2: Sequence-Dependent Interactions of Single β-Peptide - Nanorods that Display Well-Defined Three-Dimensional Chemical Nanopatterns J. Mondal, B.J. Sung, A. Yethiraj University of Wisconsin-MadisonNSEC: Templated Synthesis and Assembly at the Nanoscale three-dimensions (Figure 1). Single-molecule force measurements with hydrophobic surfaces through aqueousbuffer (triethanolamine buffer, pH 7.2) revealed that the GA and iso-GA nanorods give rise to qualitatively different adhesion force histograms, consistent with the presence of a hydrophobic domain the on one face of GA nanorod that gives rise to strong hydrophobic interactions and the absence of a comparable domain on the iso-GA nanorod (Figure 1). The results show how β-peptide nanorods can be used to study intermolecular interactions that arise from precisely defined chemical nanopatterns. Such studies and conclusions are difficult with oligo-a-peptides because of their conformational flexibility. Results from this study provide fundamental insights into the mechanisms through which changes in chemical patterns presented by organic nanoscopic objects can dramatically affect their assembly behavior. Biological systems commonly use nanoscopic patterns of chemical functional groups to encode intermolecular interactions that direct assembly of functional structures. While it is now possible to anticipate assembled structures that arise from interactions encoded by simple chemical patterns, such as those defined by oligonucleotide sequences or lipids (e.g., fatty acids), for modestly more complex systems it is not yet possible to design nanoscale chemical patterns that direct formation of specific assemblies. The development of such a capability requires a better understanding of the intermolecular interactions that result from these nanoscale patterns. As a step toward acquiring this understanding, researchers in Thrust 2 of the UW-Madison NSEC have used single-molecule force spectroscopy to characterize the intermolecular interactions of a class of oligomers formed from non-natural β-amino acids, termed “β-peptides”. The β-peptides are unusual in enabling the design of organic nanorods that present predictable, stable, and precisely defined nanoscopic patterns of chemical functionality in three dimensions. In the study reported in this highlight, the β-peptide nanorods were designed to be either globally amphiphilic (GA), i.e., display a global segregation of hydrophobic and cationic chemical functional groups, or non-globally amphiphilic(iso-GA), i.e., display a more uniform distribution of hydrophobic and cationic chemical functional groups in NSF Award Number 0832760 PI: Paul Nealey University of Wisconsin – Madison