Silk Polymer Models for Structure-Function Relationships David Kaplan, Tufts University, DMR 0402849

1
Silk Polymer Models for Structure-Function
Relationships David Kaplan, Tufts University,
DMR 0402849
Background Silk, a natural protein biopolymer
produced by silkworms and spiders, is formed into
fibers with remarkable mechanical properties.
Like synthetic polymers, silk can crystallize
(through beta sheet formation). Crystallization
spontaneously occurs during water removal in
naturally occurring silks. Water removal
directly impacts the mechanical properties and
the ability to form new high performance
materials from these proteins.
Objective To use calorimetry (heat flow) and
thermo- gravimetry (weight loss) to determine the
total water content in silk. This will allow us
to better understand both the natural silk fiber
formation process as well as to elucidate new
approaches outside the organisms in order to form
new materials from this protein.
Figure Top Depicts the weight lost by silk
films during heating at different rates. The
weight decreases, from room temperature to 165?C,
due to water removal, followed by degradation at
higher temperatures. Bottom Depicts heat flow
vs. temperature. Cycles 1-6 By successively
heating to higher temperatures water is steadily
removed from silk. The glass transition process
of dry silk can be seen at 178?C after all water
has been removed.
Data from Hu, X. Kaplan, D. Cebe, P.
Thermichimica Acta, in press 7/2007.
2
Silk Polymer Models for Structure-Function
Relationships David Kaplan, Tufts University,
DMR 0402849
Educational Aspects Profs. Kaplan and Cebe
provide research opportunities and
mentoring for undergraduate and graduate
students.
a. Graduate student Xiao Hus poster on
crystallinity determination in silk was one of
those nominated for best poster at the Fall 2006
Materials Research Society b. Undergraduate
members of the Tufts Society of Physics Students
enjoy pizza after Prof. Cebe (second from right)
presented a seminar on topics in biophysics c.
Prof. G. Georgiev (left), Assumption College,
with Tufts graduate students at the 2007 American
Physical Society March Meeting poster session. d.
Prof. Jon Garlick of
d
Tufts Medical School shows artificial skin tissue
to undergraduate interns who visited his lab on
Career Day.