Research Project
We are currently studying peptide interactions with semiconductor surfaces. In particular, we are interested in polar semiconductor materials because anion-polar and cation-polar crystalline faces have very different chemical nature, as well as surface charge. Because both amino acid side chain charge and surface charge contribute to peptide-semiconductor adhesion, polar semiconductors are interesting materials to study.
GaN is an example of one such semiconductor material. Epitaxial GaN is most commonly grown Ga-terminated, in the (0001) direction on c-plane sapphire. However, in recent years, interest in alternative substrates and growth planes has increased. Controllable, high quality epitaxial GaN material is now also available in N-terminated (000-1), semi-polar, and non-polar directions. Ga-terminated surfaces induce positive surface charge; where as N-terminated surfaces induce negative surface charge, therefore a comparison of the peptide sequences which adhere to these respective surfaces may give further insight into peptide-semiconductor adhesion mechanisms. Furthermore, peptide sequences which are able to selectively attach to N-face GaN or Ga-face GaN can be used to non-destructively detect and quantify inversion domains within epitaxially grown material. Such peptide sequences may also be useful in making metal contacts to undercut or membrane structures.
Peptide sequences which selectively adhere to a specific crystallographic semiconductor plane are found using a combinatorial phage display library technique known as biopanning. The selection process begins with a library of M13 phage in which the pIII minor protein coat has been genetically modified to include a random peptide oligomer. The library has a complexity of about 2 million clones. In the initial round of biopanning, the intended semiconductor target is incubated with the library and subsequently washed. The phage that are still bound to the target after washing are eluted and amplified. The eluate, enriched in phage with sequences that bind to the target material is used for the next binding-amplication round. The evolutionary process is repeated 3-5 times to determine a set of phage wihich clearly bind to the target material.