Complex Formation of Large-ring Cyclodextrins with Iodine in Aqueous Solution as Revealed by Isothermal Titration Calorimetry

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1 Netsu Sokutei Complex Formation of Large-ring Cyclodextrins with Iodine in Aqueous Solution as Revealed by Isothermal Titration Calorimetry Shinichi Kitamura and Kazuya Nakatani (Received January 25, 2001; Accepted February 4, 2001) Complex formation of large-ring cyclodextrins (CDs) having DP21-32 with iodine in aqueous KI solution was studied by isothermal titration calorimetry (ITC). When the individual CD is shown, the term CD n is used, where n represents the degree of polymerization. For CDs in the DP range of 21-32, the curves obtained for the titration of the CDs with iodine can be analyzed by a model assuming 1:2 complex formation with identical interacting sites. For the case of two identical interacting sites, the binding constants K 1 and K 2 (K 1 K 2), defined relative to the progress of saturation, lie in the range 0.7 to M 1 and 3.0 to M 1, respectively. The values of H 2 and T S 2 lie in the range 34.9 to kj mol 1 and 15.5 to kj mol 1, respectively. The largest values for T S 2 obtained for a CD 26 can, in part, be attributed to a large decrease in conformational flexibility of the CD which occurs during complex formation. Based on ITC data, conformational changes in CD 26 which are induced as the results of the formation of a CD-iodine inclusion complex are discussed in terms of the recently reported crystal structure of CD α - α -CDβ -β -CDγ - γ -CD 1) 9 2) 1996 D-disproportionating enzyme or 4-α -glucanotransferase, EC α -D- 3) The Japan Society of Calorimetry and Thermal Analysis. 123

2 CD ITC; Isothermal Titration Calorimeter CD 4) α -CDβ -CDγ - CD CD CD CD 6α -CDCD 7β - CDCD 8γ -CDCD 21CD 32 CD120CD 120 ITC ITC K H CD 400 rpm µm I mmki200 mm CD 200 mm µ µl 35 ITC Data Analysis In OrlginTM n M X n nm t HV 0 Q 2 [ ( ) ] X t 1 X t 1 2 4X t 1 1 (1) nm t nkm t nm t nkm t nm t Q K n V 0 M t CDK t X t H M X Fig.1 K a K c K 1K b K d K 2 K 1K 2 i MX im i F i 1 K 1[X ] K 1K 2[X ] F 2 0 F 1 F 2 (2) P P P P 1 K 1[X]K 1K 2[X] 2 I 3 P X t [X]M t (F 1 2F 2) (3) Q M tv 0{F 1 H 1 F 2( H 1 H 2)} (4) K 1K 2 (2)(3) (4) H 1 H 2 Fig.2609 µm CD µ1 25Fig.3 Fig µm CD 2630 µm CD µ

3 I 3 t / min K a K c I 3 I 3 K b K d I 3 I 3 Fig.1 Model for the complex formation of CD 21 to CD 32 with I 3. CD CD 1 CD 0.1 µj S 1 CD CD 6CD 7 CD 8 A Table 1 CD 8 CD 8 CD 6CD 7 1 CD 6 CD CD 6 CD 7 K 2 CD 6 CD 7 - H CD 6 CD 7 2 Fig.3 CD 26Fig.2 CD 6 CD 26 CD 21 CD 32CD CD 6CD 7 A CD 21CD 32 kj / mol of injectant µj / s Fig.2 Molar Ratio Experimental data for titrations of 10 µl aliquots of 4.78 mm I 2 containing 200 mm KI into a mm aqueous solution of CD 6 containing 200 mm KI solution at 20. 4) 25 Injections of the iodine solution were made at 4.5 min intervals. : data points obtained by integration of the injection peaks, and the titration curve (solid line) obtained by fitting the data points. 2 BFig.1 K 1K 2 H 1 H 2 K 1 K M 1 CD K 1 K kj mol 1 H 1 H 2 CD 24CD 26 Fig.5CD 21CD 32K 1 K 2 K 1 K 2 CD CD 24K 2 CD 21CD 232 CD 24 CD 25 K 2 CD 26 K 2 CD

4 t / min t / min µj / s µj / s kj / mol of injectant kj / mol of injectant Molar Ratio Molar Ratio Fig.3 Experimental data for titrations 7 µl aliquots of 5.38 mm I 2 containing 200 mm KI into a mm aqueous solution of CD 26 containing 200 mm KI solution at 20. 4) 35 Injections of the iodine solution were made at 4.5 min intervals. : data points obtained by integration of the injection peaks, and the titration curve (solid line) obtained by fitting the data points. Fig.4 Experimental data for titrations 7 µl aliquots of 5.38 mm I 2 containing 200 mm KI into a mm aqueous solution of CD 120 containing 200 mm KI solution at Injections of the iodine solution were made at 4.5 min intervals. : data points obtained by integration of the injection peaks, and the titration curve (solid line) obtained by fitting the data points. Table 1 Thermodynamic parameters obtained for CD 6 andcd 7 with iodine systems. CD n K H G T S mm 1 kj mol 1 kj mol 1 kj mol 1 CD a CD a The error is the estimated uncertainty of each value. Fig.6 G 2 RT lnk 2 G 2 H 2 T S 2 G 2 H 2 T S 2 H 2 T S 2 G 2 G 2 compensation effectcd 6 CD 7 5) 6) CD S CD 126

5 Binding constant(10 3 M 1 ) Fig.5 Thermodynamic Parameters (K J mol 1 ) Fig.6 Degree of polymerization DP dependences of K 1() and K 2() at 20 for CD Degree of polymerization DP dependence of G 2( ), H 2( ) and T S 2() at 20 for CD S H CD 26 CD 26X Fig.7 7) 6 1-helix2 8, X Fig7 2,8) CD 9 CD 20 n ) CD 120 A Fig.4K M 1 Fig.7 Solution 2,8) and crystal 7) structures of CD 26. H 65.3 kj mol 1 n ) CD Sodium dodecyl sulfate sodium myristoyl sulfate CD 1) Cyclodextrins, ed. By V. T. D'souza and K. B. Lipkowitz, Chem. Rev., 98 (1998). 2) S. Kitamura, "Cyclic oligosaccharides and polysaccharides" in: Cyclic polymers, 2nd edition, J. A. Semlyen, Ed., Kluwer Academic Publishers, Dordrecht, Chapter 4 (2000). 3) T. Takaha, M. Yanase, H. Takata, S. Okada, and S. M. Smith, J. Biol. Chem. 271, 2902 (1996). 4) S. Kitamura, K. Nakatani, T. Takaha, and S. Okada, Macromol. Rapid Commun. 20, (1999). 5) M. V. Rekharsky and Y. Inoue, Chem. Rev. 98, 1875 (1998). 6) D. R. Bundle and B. W. Sigurskjold, Method in Enzymology 247, 288 (1994). 7) K. Gessler, I. Uson, T. Takaha, N. Krauss, S. M. Smith, S. Okada, G. M. Sheldrick, and W. Saenger, Proc. Natl. Acad. Sci. USA 96, 4246 (1999). 8) S. Kitamura, H. Isuda, J. Shimada, T. Takada, T. Takaha, S. Okada, M. Mimura, and K. Kajiwara, 127

6 Carbohydr. Res. 304, 303 (1997). 9) S. Kitamura, K. Nakatani, K. Imamura, and T. Takaha, Abstract of 20th International Carbohydrate symposium, A-192 (2000). 10) K. Takahashi and S. Ono, J. Biochem. 72, 1041 (1972) CD 21CD CD 6 CD CD 21 CD CD 24CD 26 Shinichi Kitamura, Dept. of Biological Resource Chemistry, Kyoto Prefectural Univ., TEL , FAX , skita@kpu.ac.jp Kazuya Nakatani, San-Ei Gen F. F. I., Inc., TEL , FAX , kazuu@ma9. seikyou.ne.jp XIV RUSSIAN CONFERENCE ON CHEMICAL THERMODYNAMICS with International Participation 1-5 July 2002, in St. Petersburg Topics thermochemistry of organic and inorganic substances, advanced materials thermodynamics of liquid solutions, melts and solid solutions phase equilibria thermodynamics of surface and interface phenomena thermodynamics of polymer systems, liquid crystalline, self-assembling and biological systems experimental methods and equipment standardization and systematization of thermodynamic data teaching of chemical thermodynamics Dates and Deadlines: 1 July 2001 Deadline for the Registration Form receiving 1 February 2002 Deadline for submission of the Abstract March 2002 Second Announcement The address of the Organizing Committee: RCCT2002 Div. of Physical Chemistry, Department of Chemistry, St. Petersburg State University Universitetsky pr. 2, Petrodvorets, St. Petersburg, Russia Phone: 7(812) FAX: 7 (812) rcct2002@nonel.pu.ru 128

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