Towards rational design of peptides for selective interaction with inorganic materials

Abstract

Utilizing molecular recognition and self-assembly, material-specific biomolecules have shown great promise for engineering and ordering materials at the nanoscale. These molecules, inspired from natural biomineralization systems, are now commonly selected against non-natural inorganic materials through biopanning random combinatorial peptide libraries. Unfortunately, the challenge of studying the biological inorganic interface has slowed the understanding of interactions principles, and hence limited the number of downstream applications. This work focuses on the facile study of the peptide-inorganic interface using Yeast Surface Display. The general approach is to use combinatorial selection to suggest interaction principles followed by rational design to refine understanding. In this pursuit, two material groups-II-VI semiconductors and synthetic sapphire (metal oxides)-are chosen as inorganic targets due to their technological relevance and ease of study. First, yeast surface display (YSD) was established as a broadly applicable method for studying peptide-material interactions by screening a human scFv YSD library against cadmium sulfide (CdS), a II-VI semiconductor. The presence of multiple histidine residues was found to be necessary for mediating cell binding to CdS. As a follow-up, a systematic screen with yeast displayed rationally designed peptides was performed on a panel of II-VI semiconductors and gold. Cell binding results indicated that peptide interaction was mediated by a limited number of amino acids that were influenced by locally situated residues. Interpretation of the results facilitated design of new peptides with desired material specificities. Next, the nature of peptide/metal oxide binding interface was interrogated using sapphire crystalline faces as model surfaces.

(cont.) Biopanning a random peptide YSD library and subsequent characterization of the identified binding partners revealed the importance of multiple basic amino acids in the binding event. Study of rationally designed basic peptides revealed a preference for those amino acids to be spaced in such a manner that maximized simultaneous interaction with the surface. Fusing peptides to maltose binding protein (MBP) allowed for quantitative affinity measurement with the best peptides having low nanomolar equilibrium dissociation constants. Finally, peptides were demonstrated as facile affinity tags for protein immobilization in micro-patterning and biosensor assays.