TY - JOUR
T1 - Modeling and Experiment Reveal Structure and Nanomechanics across the Inverse Temperature Transition in B. mori Silk-Elastin-like Protein Polymers
AU - Tarakanova, Anna
AU - Huang, Wenwen
AU - Qin, Zhao
AU - Kaplan, David L.
AU - Buehler, Markus J.
N1 - Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/11/13
Y1 - 2017/11/13
N2 - Silk and elastin are exemplary protein materials that exhibit exceptional material properties. Silk is uniquely strong, surpassing engineering materials such as Kevlar and steel, while elastin has exquisite flexibility and can reversibly fold into a more structured form at high temperatures when many other proteins would unfold and denature. This phenomenon in elastin is termed the inverse temperature transition. It is a reversible, controllable process that motivates applications in drug delivery, shape change materials, and biomimetic devices. Silk-elastinlike protein polymers (SELPs), which combine repeating B. mori silk and elastin blocks, have been introduced as biologically inspired materials that combine the distinctive properties of the component parts to achieve strong and extensible, tunable biomaterials. Here, we considered a single SELP sequence to examine temperature transition effects at the molecular scale. SELP molecular models were created using Replica Exchange Molecular Dynamics, an accelerated sampling method, and confirmed in experiment by comparing secondary structure distributions. A molecular collapse of the SELP molecule was observed with increased temperature in both molecular simulation and experiment. Temperature-specific differences were observed in the mechanical properties and the unfolding pathways of the polypeptide. Using the Bell-Evans model, we analyzed the free energy landscape associated with molecular unfolding at temperatures below and above the transition temperature range (Tt) of the polypeptide. We found that at physiological pulling rates, the energy barrier to unfold SELPs was counterintuitively higher above Tt. Our findings offer a foundational perspective on the molecular scale mechanisms of temperature-induced phase transition in SELPs, and suggest a novel approach to combine simulation and experiment to study materials for multifunctional biomimetic applications.
AB - Silk and elastin are exemplary protein materials that exhibit exceptional material properties. Silk is uniquely strong, surpassing engineering materials such as Kevlar and steel, while elastin has exquisite flexibility and can reversibly fold into a more structured form at high temperatures when many other proteins would unfold and denature. This phenomenon in elastin is termed the inverse temperature transition. It is a reversible, controllable process that motivates applications in drug delivery, shape change materials, and biomimetic devices. Silk-elastinlike protein polymers (SELPs), which combine repeating B. mori silk and elastin blocks, have been introduced as biologically inspired materials that combine the distinctive properties of the component parts to achieve strong and extensible, tunable biomaterials. Here, we considered a single SELP sequence to examine temperature transition effects at the molecular scale. SELP molecular models were created using Replica Exchange Molecular Dynamics, an accelerated sampling method, and confirmed in experiment by comparing secondary structure distributions. A molecular collapse of the SELP molecule was observed with increased temperature in both molecular simulation and experiment. Temperature-specific differences were observed in the mechanical properties and the unfolding pathways of the polypeptide. Using the Bell-Evans model, we analyzed the free energy landscape associated with molecular unfolding at temperatures below and above the transition temperature range (Tt) of the polypeptide. We found that at physiological pulling rates, the energy barrier to unfold SELPs was counterintuitively higher above Tt. Our findings offer a foundational perspective on the molecular scale mechanisms of temperature-induced phase transition in SELPs, and suggest a novel approach to combine simulation and experiment to study materials for multifunctional biomimetic applications.
KW - B. mori silk
KW - Bell-Evans model
KW - elastin
KW - inverse temperature transition
KW - protein polymers
KW - silk-elastinlike protein polymers (SELPs)
KW - steered molecular dynamics (SMD)
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U2 - 10.1021/acsbiomaterials.6b00688
DO - 10.1021/acsbiomaterials.6b00688
M3 - Article
AN - SCOPUS:85034103966
SN - 2373-9878
VL - 3
SP - 2889
EP - 2899
JO - ACS Biomaterials Science and Engineering
JF - ACS Biomaterials Science and Engineering
IS - 11
ER -