Self-assembled monolayers from a designed combinatorial library of de novo beta-sheet proteins.
A variety of naturally occurring biomaterials owe their unusual structural and mechanical properties to layers of beta-sheet proteins laminated between layers of inorganic mineral. To explore the possibility of fabricating novel two-dimensional protein layers, we studied the self-assembly properties of de novo proteins from a designed combinatorial library. Each protein in the library has a distinct 63 amino acid sequence, yet they all share an identical binary pattern of polar and nonpolar residues, which was designed to favor the formation of six-stranded amphiphilic beta-sheets. Characterization of proteins isolated from the library demonstrates that (i) they self assemble into monolayers at an air/water interface; (ii) the monolayers are dominated by beta-sheet secondary structure, as shown by both circular dichroism and infrared spectroscopies; and (iii) the measured areas (500- 600 A(2)) of individual protein molecules in the monolayers match those expected for proteins folded into amphiphilic beta-sheets. The finding that similar structures are formed by distinctly different protein sequences suggests that assembly into beta-sheet monolayers can be encoded by binary patterning of polar and nonpolar amino acids. Moreover, because the designed binary pattern is compatible with a wide variety of different sequences, it may be possible to fabricate beta-sheet monolayers by using combinations of side chains that are explicitly designed to favor particular applications of novel biomaterials.
Department of Chemistry, Princeton University, Princeton, NJ 08544-1009, USA.
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Hecht
D000388:Air; D000595:Amino Acid Sequence; D008956:Models, Chemical; D008958:Models, Molecular; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D015202:Protein Engineering; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D014867:Water / Q000737:chemistry
D010455:Peptides; D014867:Water