AbstractsBiology & Animal Science

Diamond-like carbon binding peptides evolutionary selection, characterization, and engineering

by Bartosz Gabryelczyk

Institution: University of Helsinki
Department: Department of Biosciences, Division of Biochemistry and Biotechnology; VTT Technical Research Centre of Finland
Year: 2015
Keywords: biotechnology
Record ID: 1130138
Full text PDF: http://hdl.handle.net/10138/153473


The possibility of controlling interactions at interfaces and surfaces of solid materials is highly interesting for a wide range of materials-related nanotechnological applications, for example, colloidal systems, adhesives, biosensors, biomimetic composite and biomedical materials. In Nature, many proteins and peptides possess the ability to recognize, specifically bind, and modify the surfaces of solid materials through sophisticated mechanism of molecular recognition. These properties have been developed during evolution via successive cycles of random mutations and selection. The natural evolution processes can be mimicked in the laboratory scale with the use of a directed evolution approach, for instance, based on the selection of short material-specific peptides from the combinatorial libraries displayed on the surface of bacteriophages or bacterial cells. Selected from billions of different variants, material-specific peptides can be studied by experimental and computational methods to define their sequence, structure, and binding properties. Subsequently, they can be engineered in order to improve their binding affinity and tailor their function for practical applications. The studies presented in this thesis show how phage display was used to identify peptides binding to diamond-like carbon (DLC). DLC is an amorphous form of carbon, with chemical and physical properties resembling natural diamond. It is used as a coating material in many industrial and biomedical applications. Peptides binding to DLC were selected form a combinatorial phage display library. Their binding and molecular basis of the function were investigated in different molecular contexts (when displayed on the phage surface, forming fusion proteins, or present in free soluble form), using multiple independent methods. It was also demonstrated that the peptides can be used in nanotechnological applications, i.e., as a self-assembling coating on the DLC surface, and for controlling properties of a colloidal form of DLC. Besides finding and characterizing peptides binding to DLC, the thesis also highlights different challenges of the directed evolution techniques, for example, selection of target unrelated peptides during biopanning, and the necessity of multiple independent ways of analyzing the functionality of selected peptides. Materiaalien pintoihin ja partikkeleihin spesifisesti sitoutuvat biologiset molekyylit ovat kiinnostavia erilaisten sovellusten ja uusien materiaalien kehittämisessä. Esimerkkejä tällaisista sovelluksista ovat biosensorit, jotka pystyvät tunnistamaan haitallisia kemikaaleja, bio-yhteensopivissa olosuhteissa toimivat biokatalyytit tai kudosimplantteina käytettävät biomateriaalit. Luonnossa monet organismit kuten bakteerit, homeet, nilviäiset ja hyönteiset tuottavat biomakromolekyylejä (useimmiten proteiineja), jotka pystyvät tunnistamaan ja sitoutumaan erilaisiin materiaalipintoihin. Materiaalien ja biomolekyylien väliset vuorovaikutukset ovat kehittyneet evoluution saatossa, jolloin myös olosuhteisiin nähden…