Using Hydrated Reversed Micelles to Evaluate the Dimensions of Polymer-Protein Adducts

E. M. Sorokina¹, E. V. Zhavoronkova², N. V. Efremova¹, I. N. Topchieva^2*, and B. I. Kurganov¹

¹Bach Institute of Biochemistry, Russian Academy of Sciences, Leninskii pr. 33, Moscow, 117071 Russia; fax: (095) 954-2732; E-mail: inbio@glas.apc.org

²School of Chemistry, Lomonosov Moscow State University, Moscow, 119899 Russia; fax: (095) 939-0174

^* To whom correspondence should be addressed.

Received July 22, 1998; Revision received December 29, 1998

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Hydrolysis of N-trans-cynnamoylimidazole catalyzed by conjugates and complexes of alpha-chymotrypsin (ChT) with poly(ethylene glycol) (PEG) of different molecular mass (from 300 to 5000 daltons) was studied in the system of the hydrated reversed micelles of aerosol OT (AOT) in octane at 25°C. The plot of the deacylation constant k₃ for PEG--ChT conjugates and complexes versus the degree of hydration of reversed micelles (w₀ = [H₂O]/[AOT]) was studied. These plots are bell-shaped with maxima shifted to higher degrees of micelle hydration compared to the corresponding value of the shift for ChT. As for PEG--ChT conjugates, the value of the shift of w₀ increases with increasing of molecular mass of the attached PEG and/or with the number of polymer chains per ChT molecule. Another picture was observed for PEG--ChT complexes for which the position of the maximum on k₃ versusw₀ curves was practically the same for all compounds. The values of the thickness of the polymer layer for PEG--ChT conjugates and complexes were calculated. Thus, polymer chains in conjugates placed in hydrated micelles are highly packed, whereas in the case of complexes they form a flat layer on the surface of the protein.

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KEY WORDS:alpha-chymotrypsin, poly(ethylene glycol), polymer--protein complexes and conjugates, high pressure, aerosol OT, reversed micelles

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