BE.342/442 Tuesday, December 6, 2005
Topic: Research in Biomaterials
Take-home midterms will be returned on Thursday.
Evaluation forms will be filled out today.
The last 2 lectures will be dedicated to graduate student presentations.
Term papers (grads) or review articles (undergrads) are due December 23
as a hard copy
delivered to Prof. Zhang’s office in person or by interdepartmental mail.
Research groups involved in biomaterials
Google these people—they’ll give you great ideas for research, and for your final projects!
, Princeton University – graduated from MIT in 1985, and now works on
combinatorial protein design, selection, and evolution.
With over 10
possible sequences for a protein of 100 residues, how can we select
proteins for desired properties? Many large proteins form into a globular shape in
solution, so that the hydrophobic groups can aggregate in the center. The middle position
in the 3-nucleic-acid codons has high correlation to the amino acid identity (whereas the
third position is usually involved in wobble). This allows a single mutation at the second
position to change the encoded amino acid.
Michael Hecht designed alpha helices with amino acid sequences that follow a pattern in
the primary structre: polar, nonpolar, p, p, n, n, p, p, n, p, p, n, n, p. This virtually
guarantees self-assembly into a coiled-coil structure. Hecht incorporated 6 polar residues
(Glu, Gln, Asp, Asn, Lys, or His) and 5 nonpolar residues (Met, Leu, Ile, Val, or Phe) and
selected 50 of the 5x10
possible proteins that display solubility, alpha-helical character,
stability to unfolding, cooperative thermal denaturation, and high charge in enthalpy.
The protein design considered structure and function, including: globular folded
structures, fibers (amyloid structures in nature, or biomaterials), and binding/activity. For
example, proteins were selected for their ability to bind air, pattern on surfaces, etc.