IGEM:IMPERIAL/2008/Prototype/Biomaterials

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Biomaterials

We aim to synthesize two types of biomaterials, elastin and EAK16-II 3D scaffolds.


Elastin

Elastin is a polymeric extracellular matrix protein found in tissues that require the abitlity to extend as well as posses elastic recoil. Examples of elastin containing tissues include arteries, lungs, ligaments and skin. The precursor for elastin is a soluble protein called tropoelastin, consisting of alternating hydrophobic regions and crosslinking domains with distinct exons coding each domain.

Under appropriate conditions of temperature and ionic strength, elastin undergoes a self-aggregation process called coacervation. This is where the protein separates from the solution as a second phase and is usually induced by an increase in temperature.

Unlike most proteins, which undergo denaturation when the temperature of the solution increases, elastin polypeptides become more ordered through coacervation. The temperature at which coacervation occurs is dependent on the relative proportions of hydrophobic and hydrophilic residues in the synthetic polypeptides as well as the ionic strength, pH and protein concentration of the solution.

Construct EP20-24-24 for human elastin polypeptide

Hydrophobic interactions and cross-linkages between adjacent EP chains

Dependence of coacervation on temperature and peptide concentration for EP20-24-24


EAK16-II

EAK16-II is a self-assembling peptide which forms stable β-sheet structures in water and exists naturally as a region in zuotin, a yeast protein. The amino acid sequence for EAK16-II is AEAEAKAKAEAEAKAK and has an estimated molecular mass of 1615.8. When examined under SEM, a well-ordered nanofibre structure is formed by the association of the EAK16-II proteins and these nanofibres can futher aggregate to form a membranous 3D scaffold.

The alternating positive and negative charges (--++--++) are responsible for creating an electrostatic attraction between adjacent peptides and self-assembly is triggered when the proteins are exposed to physiological media or salt solution.

Molecular structure of EAK16-II peptide


How B. subtilis can be used in producing material


References
  1. Bellingham CM, Woodhouse KA, Robson P, Rothstein SJ, and Keeley FW. Self-aggregation characteristics of recombinantly expressed human elastin polypeptides. Biochim Biophys Acta. 2001 Nov 26;1550(1):6-19. DOI:10.1016/s0167-4838(01)00262-x | PubMed ID:11738083 | HubMed [Elastin]
  2. Keeley FW, Bellingham CM, and Woodhouse KA. Elastin as a self-organizing biomaterial: use of recombinantly expressed human elastin polypeptides as a model for investigations of structure and self-assembly of elastin. Philos Trans R Soc Lond B Biol Sci. 2002 Feb 28;357(1418):185-9. DOI:10.1098/rstb.2001.1027 | PubMed ID:11911775 | HubMed [Elastin]
  3. Zhang S, Gelain F, and Zhao X. Designer self-assembling peptide nanofiber scaffolds for 3D tissue cell cultures. Semin Cancer Biol. 2005 Oct;15(5):413-20. DOI:10.1016/j.semcancer.2005.05.007 | PubMed ID:16061392 | HubMed [EAK16-II]
  4. Ling Lin Fu, Zi Rong Xu, Wei Fen Li, Jiang Bing Shuai, Ping Lu, and Chun Xia Hu. Protein secretion pathways in Bacillus subtilis: implication for optimization of heterologous protein secretion. Biotechnol Adv. 2007 Jan-Feb;25(1):1-12. DOI:10.1016/j.biotechadv.2006.08.002 | PubMed ID:16997527 | HubMed [ProteinSecretion]
  5. Tjalsma H, Bolhuis A, Jongbloed JD, Bron S, and van Dijl JM. Signal peptide-dependent protein transport in Bacillus subtilis: a genome-based survey of the secretome. Microbiol Mol Biol Rev. 2000 Sep;64(3):515-47. DOI:10.1128/MMBR.64.3.515-547.2000 | PubMed ID:10974125 | HubMed [Proteomics]
All Medline abstracts: PubMed | HubMed

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