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Fig. 3 SDS-PAGE gel of streptavidin (lane A) and the streptavidin–
pNIPAAm complex (lane B) compared to the molecular weight marker.
1
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1
(3.7 biotins per streptavidin). This result demonstrates that steric
hindrance does not inhibit binding of the polymer to streptavidin.
In conclusion, we have described a new strategy to synthesize
a-functional pNIPAAm. The use of a biotin-functionalized
initiator for ATRP allowed for the preparation of low poly-
dispersity, biotinylated pNIPAAm in one step in good yield. The
polymer chain did not hinder interaction of the biotin with
the protein, and the pNIPAAm readily bound to streptavidin. The
resulting streptavidin–pNIPAAm conjugate should be useful in a
variety of applications.
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This work was supported by the NSF (CHE-0416359). CEB
thanks the CNSI for an Undergraduate Research Fellowship. TL
thanks the NSF-funded Center for Scalable and Integrated
Nanomanufacturing (DMI-0327077) for an Undergraduate
Summer Research Internship. Prof. Thomas Ward, U. de
Neuch aˆ tel, is acknowledged for kindly donating recombinant
streptavidin.
(e) G. Masci, L. Giacomelli and V. Crescenzi, Macromol. Rapid
Commun., 2004, 25, 559; (f) Y. Xia, X. Yin, N. A. D. Burke and
H. D. H. St o¨ ver, Macromolecules, 2005, 38, 5937 (published after
submission of this paper).
17 These conditions were chosen because higher conversions were achieved
with higher catalyst to initiator ratios, as is also reported in the
16b,c
literature.
2
A small amount of CuCl was added because the
Notes and references
addition of Cu(II) is known to reduce termination events and therefore
improve control over the polymerization (see ref. 16a and references
therein).
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18 G. T. Hermanson, Bioconjugate Techniques, Academic Press, New
York, 1996.
20, 1.
4
704 | Chem. Commun., 2005, 4702–4704
This journal is ß The Royal Society of Chemistry 2005