Phage display screening of a surface-immobilized adenine derivative led to the identification of a heptameric peptide with selectivity for adenine as demonstrated through quartz crystal microbalance (QCM) studies. The peptide demonstrated a concentration dependent affinity for an adeninyl moiety decorated surface (KD of 968 ± 53.3 μM), which highlights the power of piezoelectric sensing in the study of weak interactions. 

The focus of this thesis has been to examine two new concepts involving the interaction of biological agents with synthetic material surfaces.

The feasibility of deploying phage display techniques for the screening of materials in non-biological media was examined in two studies. Firstly, the utility of a phage library based on the M13 phage was used to identify peptides with affinity for α-chymotrypsin in media containing significant amounts of an organic solvent, acetonitrile. The selected peptides were demonstrated to inhibit enzyme autolysis. The influence of immobilization to the substrate used in the screening studies, Eupergit®, on the function of this enzyme in organic solvents was examined; enhanced enzyme resilience to organic solvents was demonstrated. Secondly, phage display screening for cyclic heptapeptide motifs selective for adenine was undertaken using an adenine derivatized glass surfaces as a target. A peptide with affinity for adenine was identified and quartz crystal microbalance studies demonstrated selectivity for the adeninyl moiety.

Finally, the influence of oseltamivir molecularly imprinted polymer particles on the capacity of avian influenza A virus H1N1 to replicate in Madin-Darby Canine Kidney cells was investigated. The polymer matrix was shown to demonstrate a general though small suppression of virus replication.

The expression of peptides on phage coat proteins via genetic engineering was first achieved in 1985 [1] and was followed by the construction of phage display combinatorial libraries in 1990 [2].  Phage display combinatorial libraries have been used not only to find peptides that interact with various biomolecules such as receptors, antibodies, enzyme active sites, and protein surfaces, but also to find peptides with affinity for metals and plastics and with function in non-biological environments [3].

In this study, we have challenged a cyclic heptamer phage display library with surfaces adenine functionalised surfaces with the aim of identifying peptide motifs selective for adenine. The synthesis and characterisation of surfaces, and results from phage display screening shall be presented.

[1] Smith, G.P. Science (1985) 228, 1315-1317.

[2] Scott, J.K.; Smith, G.P. Science (1990) 249, 386-390.

[3] Olofsson, L.; Söderberg, P.; Ankarloo, J.; Nicholls, I.A. J. Mol. Recognit. (2008) 19, 18-25.

Here we report the first application of phage display screening in low dielectric media. Two series of phage clones with affinity for α-chymotrypsin (CT) were selected from a Ph.D.^TM-C7C library, using either a buffer or acetonitrile in buffer (50%, v/v). The affinity of lysates, individual clones or selected cyclic peptides for the enzyme was studied by examining their influence on CT activity. Peptides displayed on phage selected in buffer provided significant protection from enzyme autolysis resulting in marked increase in CT activity (>100%). Phage selected in ACN provided some, albeit weak, protection from the detrimental influence on CT from ACN. In conclusion, the results demonstrate the potential for the application of phage display screening protocols to targets in media of low dielectricity.