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Keywords:

  • monoclonal antibody;
  • DNA duplex interactions

Abstract

We have reexamined the van't Hoff plots and delineation of thermodynamic data of the monoclonal antibodies of Jel 274 and Jel 241 binding to DNA duplex at high ionic strength using fluorescein-labeled oligonucleotide titration with increasing concentrations of the antibody as reported by Tanha and Lee (Nucleic Acid Res, 1997, 25, 1442). To compare the thermodynamic parameters from data over the experimental temperature range of 277–312.5 K, the binding constant from van't Hoff plots is used to evaluate ΔGo(T) from 0 to 400 K using our general linear T3 model, ΔGo(T) = α +βT2T3. The limited information provided by the van't Hoff plots and their extensions is not sufficient to describe the variations in the Gibbs free energy change as a function of temperature and other thermodynamic functions observed in these and other biological interactions. Rather, it is necessary to determine a number of thermodynamic parameters, including the heat of reaction, (Th), (Tm), and (TCp), and the thermal set point, (TS), all of which can be precisely assessed using our general linear T3 model. To date, no experimental measurement offers this degree of accuracy. In evaluating the thermodynamic parameters in the binding interaction of monoclonal IgG Jel 241–d[AT]20DNA duplex, it is apparent that at a high NaCl concentration, the range of the compensatory temperatures, (Th) = 155 K and (Tm) = 450 K, is much broader than observed in any other sample, whereas the thermal set points, (TS) = 330 K, is 20–30 K higher. The inherent chemical bond energy ΔHo(T0) is much lower in this sample. The values of thermal agitation energy (heat capacity integrals) are of similar magnitude for all the samples tested. It appears that increasing the NaCl concentration to 130 mM will greatly enhance the binding interaction between the monoclonal antibody and DNA duplex. It is not clear, however, from the limited data available, whether the binding interaction is sequence specific, although logic would suggest it is. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009