transformations that can be used by everyone, such as the
one described, are needed to meet the ever-growing interest,
curiosity, and demand for these unique materials and their
properties.
This research was supported by BU and by the Advanced
Notes and references
1 P. Wasserscheid and T. Welton, Ionic Liquids in Synthesis,
Wiley-VCH, Weinheim, Germany, 2003.
2 J. H. Davis, Chem. Lett., 2004, 33, 1072–1077.
3 T. Ueki and M. Watanabe, Macromolecules, 2008, 41, 3739–3749.
4 P. Dominguez de Maria, Angew. Chem., Int. Ed., 2008, 47,
6960–6968.
5 Ionic Liquids as Green Solvents: Progress and Prospects,
R. D. Rogers and K. R. Seddon, American Chemical Society,
Washington, DC, 2003.
6 V. A. Cocalia, K. E. Gutowski and R. D. Rogers, Coord. Chem.
Rev., 2006, 250, 755–764.
7 C. J. Bradaric, A. Downard, C. Kennedy, A. J. Roberston and
Y. Zhou, Green Chem., 2003, 5, 143.
8 H. Chen, D. Kwait, Z. Gonen, B. Weslowski, D. Abdallah and
R. Weiss, Chem. Mater., 2002, 14, 4063–4072.
9 Cytec, Phosphonium-Based Ionic Liquids Scholarly References,
10 T. Payagala, J. Huang, Z. S. Breitbach, P. S. Sharma and
D. W. Armstrong, Chem. Mater., 2007, 19, 5848–5850.
11 M. Wathier and M. W. Grinstaff, J. Am. Chem. Soc., 2008, 130,
9648–9649.
12 H. C. Kolb, M. G. Finn and K. B. Sharpless, Angew. Chem., Int.
Ed., 2001, 40, 2004–2021.
Fig. 2 (top) MALDI traces of lysozyme and IL-modified lysozyme.
(bottom) Enzymatic activity of lysozyme, IL-modified lysozyme, and
denatured lysozyme. N = 3; avg Æ SD.
Finally, we evaluated the enzymatic activity of the
lysozyme(IL)7 using a well-characterized fluorescence-based
assay that involves Micrococcus lysodeikticus cell walls which
have been extensively modified with fluorescein such that the
fluorescence is quenched. Subsequent lysozyme cleavage of the
b-(1–4)-glucosidic linkages between N-acetylmuramic acid and
N-acetyl-D-glucosamine of the cell wall affords an increase in
fluorescence and thus a measure of enzymatic activity. As
shown in Fig. 2, an increase in fluorescence as a function of
enzyme concentration was observed for both lysozyme and IL
modified lysozyme but not for denatured lysozyme,
demonstrating that such ionic liquid modifications of protein
structure can retain enzymatic activity. Though the IL
modified lysozyme did show a decrease in activity, it was still
quite active despite this high degree of protein modification.
In summary, an IL reagent—an ionic liquid succinimidyl
activated ester—was synthesized in two steps from
commercially available materials in high yield. Using this
reagent, several ionic liquids were prepared in good to high
yields. The generality of this approach will facilitate the
preparation of new ionic liquid materials from small
molecules to macromolecules. The ionic liquids reported
herein highlight this point as the small molecule compounds
possess aromatic groups or amide linkages that are capable of
participating in hydrogen bonding or aromatic substitution
reactions. The protein study showed that an ionic liquid
modified lysozyme retained its structure and enzymatic
activity, and thus encourages the study of new biohybrid
compositions. Given the diversity of applications being
explored with current ionic liquids, additional synthetic
13 G. W. Anderson, J. E. Zimmerman and F. M. Callahan, J. Am.
Chem. Soc., 1963, 85, 3039.
14 G. W. Anderson, J. E. Zimmerman and F. M. Callahan, J. Am.
Chem. Soc., 1964, 86, 1839–1841.
15 S. B. Hanna and G. W. Cline, J. Am. Chem. Soc., 1987, 109,
3087–3091.
16 C. F. Meares, Perspectives in Bioconjugate Chemistry, ACS,
Washington, 1993.
17 A. Romero, A. Santos, J. Tojo and A. Rodriguez, J. Hazard.
Mater., 2008, 151, 268–273.
18 K. M. Docherty, S. Z. Hebbeler and C. F. Kulpa, Green Chem.,
2006, 8, 560–567.
19 V. Singh, S. Kaur, V. Sapehiyia, J. Singh and G. L. Kad, Catal.
Commun., 2005, 6, 57–60.
20 M. R. Imam, M. Peterca, U. Edlund, V. S. K. Balagurusamy and
V. Percec, J. Polym. Sci., Part A: Polym. Chem., 2009, 47,
4165–4193.
21 J. Gorke, F. Srienc and R. Kazlauskas, Biotechnol. Bioprocess Eng.,
2010, 15, 40–53.
22 S. V. Muginova, A. Z. Galimova, A. E. Polyakov and
T. N. Shekhovtsova, J. Anal. Chem., 2010, 65, 331–351.
23 M. Moniruzzaman, K. Nakashima, N. Kamiya and M. Goto,
Biochem. Eng. J., 2010, 48, 295–314.
24 F. van Rantwijk and R. A. Sheldon, Chem. Rev., 2007, 107,
2757–2785.
25 J. P. Mann, A. McCluskey and R. Atkin, Green Chem., 2009, 11,
785–792.
26 N. Byrne and C. A. Angell, J. Mol. Biol., 2008, 378, 707–714.
27 N. Byrne, L. M. Wang, J. P. Belieres and C. A. Angell, Chem.
Commun., 2007, 2714–2716.
28 C. Lange, G. Patili and R. Rudolph, Protein Sci., 2005, 14,
2693–2701.
29 C. A. Summers and R. A. I. Flowers, Protein Sci., 2000, 9,
2001–2001.
30 M. Bekhouche, B. Doumeche and L. J. Blum, J. Mol. Catal. B:
Enzym., 2010, 65, 73–78.
31 Z. Wang, D. Li and J. Jin, Spectrochim. Acta, Part A, 2008, 70,
866–870.
c
2130 Chem. Commun., 2011, 47, 2128–2130
This journal is The Royal Society of Chemistry 2011