TY - JOUR
T1 - Effects of systematic variation of amino acid sequence on the mechanical properties of a self-assembling, oligopeptide biomaterial
AU - Caplan, Michael R.
AU - Schwartzfarb, Elissa M.
AU - Zhang, Shuguang
AU - Kamm, Roger D.
AU - Lauffenburger, Douglas A.
N1 - Funding Information:
WethankDavMidni,eAalarGrinzonskid,anydJohnKisdayiforhepfulldsisc-u sons,iand Ada Au for help in preparing Ž gures. Alos, we are indebtetodGahret McKinleanyd the stuents indhis laboroary fortgenerouy asollinglwus use of ther i rheomeeantrd for hp inedelvopingethel protocol. This work was supported by a grant from the Naitoal InniuttesofsHteta(GhMl55781). The WhaikFout ndeairton provided a graduae ftlewoshipl for M. R. C.
PY - 2002
Y1 - 2002
N2 - In order to elucidate design principles for biocompatible materials that can be created by in situ transformation from self-assembling oligopeptides, we investigate a class of oligopeptides that can self-assemble in salt solutions to form three-dimensional matrices. This class of peptides possesses a repeated sequence of amino acid residues with the type: hydrophobic/negatively-charged/hydrophobic/positively-charged. We systematically vary three chief aspects of this sequence type: (1) the hydrophobic side chains; (2) the charged side chains; and (3) the number of repeats. Each of these has been previously shown to influence the self-assembly properties of these materials. Employing a rheometric assay we measure the shear modulus of gels created from variants of each of these aspects. First, we observe order-of-magnitude changes in shear moduli when we vary oligopeptide length, with biphasic dependence on length. This result may be due to competition between, in short oligopeptides, additional repeats either increasing the diameter of the filaments or increasing the area of interaction between individual molecules and, in large oligopeptides, additional repeats allowing the oligopeptides to fold back upon themselves and decrease their effective length. Second, no statistically significant difference is observed among the hydrophobic variants, suggesting that hydrophobicity and steric overlap are unlikely to play a significant role in filament mechanical properties. Finally, in variation of the charged side chains we observe a small difference in the shear moduli that, if significant, may mean that decreasing the energetic penalty for dehydrating the charged side chains can lead to a stiffer matrix. Overall, we demonstrate that it is possible to achieve order-of-magnitude changes in shear modulus by simple variations of oligopeptide length, while the residue substitutions affect only self-assembly properties. Thus, diverse aspects of these molecules can be designed rationally to yield desirable materials properties of different types.
AB - In order to elucidate design principles for biocompatible materials that can be created by in situ transformation from self-assembling oligopeptides, we investigate a class of oligopeptides that can self-assemble in salt solutions to form three-dimensional matrices. This class of peptides possesses a repeated sequence of amino acid residues with the type: hydrophobic/negatively-charged/hydrophobic/positively-charged. We systematically vary three chief aspects of this sequence type: (1) the hydrophobic side chains; (2) the charged side chains; and (3) the number of repeats. Each of these has been previously shown to influence the self-assembly properties of these materials. Employing a rheometric assay we measure the shear modulus of gels created from variants of each of these aspects. First, we observe order-of-magnitude changes in shear moduli when we vary oligopeptide length, with biphasic dependence on length. This result may be due to competition between, in short oligopeptides, additional repeats either increasing the diameter of the filaments or increasing the area of interaction between individual molecules and, in large oligopeptides, additional repeats allowing the oligopeptides to fold back upon themselves and decrease their effective length. Second, no statistically significant difference is observed among the hydrophobic variants, suggesting that hydrophobicity and steric overlap are unlikely to play a significant role in filament mechanical properties. Finally, in variation of the charged side chains we observe a small difference in the shear moduli that, if significant, may mean that decreasing the energetic penalty for dehydrating the charged side chains can lead to a stiffer matrix. Overall, we demonstrate that it is possible to achieve order-of-magnitude changes in shear modulus by simple variations of oligopeptide length, while the residue substitutions affect only self-assembly properties. Thus, diverse aspects of these molecules can be designed rationally to yield desirable materials properties of different types.
KW - Protein engineering
KW - Rational design
KW - Shear modulus
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U2 - 10.1163/156856202320176493
DO - 10.1163/156856202320176493
M3 - Article
C2 - 12102591
AN - SCOPUS:1842845084
SN - 0920-5063
VL - 13
SP - 225
EP - 236
JO - Journal of Biomaterials Science, Polymer Edition
JF - Journal of Biomaterials Science, Polymer Edition
IS - 3
ER -