Kinetic and Thermodynamic Studies on the Binding of 125I –Anti CA 15-3 Antibody to the Isolated CA 15-3 from Human Breast Tumor  Homogenate

H.N.Al-Rubae, Salwa; A.  AL-Mudhaffar, Sami; K. Muslih, Raad

	Kinetic and Thermodynamic Studies on the Binding of 125I –Anti CA 15-3 Antibody to the Isolated CA 15-3 from Human Breast Tumor Homogenate
AL-TAQANI
Article 1, Volume 23, Issue 5, 2010, Pages 145-168
Authors
Salwa H.N.Al-Rubae; Sami A. AL-Mudhaffar; Raad K. Muslih
Abstract
This research include, the studies of kinetic and thermodynamic parameter associated with the binding of 125I-anti CA15-3 antibody to isolated CA15-3 from benign (Fibroadenoma) and malignant breast tumors tissues (IDC) were investigated. It was shown that the reaction in all studied cases follow pseudo-first order reaction kinetics. The maximum binding (Bmax) of isolated CA15-3 in benigen tissue homogenates was 10.48x10-3 mg.mL-1 after 90 minutes incubation at 37oC, while the (Bmax) of isolated CA15-3 in malignant tissue homogenates was 13.38x10-3 mg.mL-1. The (Bmax) was decreased with increasing temperature. The values of affinity constant (Ka) were dependent on the temperature, Ka increased from 14.18 mg-1.mL at 5oC to 31.65 mg-1.mL at 45oC in benigen tissue homogenates , while Ka was increased from 13.87 mg-1.mL at 5oC to 23.81 mg-1.mL at 45oC in malignant tissue homogenates. The association constant K+1 increased with temperature in (Fibroadenoma). On the other hand, K+1 was independent of temperatures in (IDC). Time course, scatchard, Van’t Hoff and Arrhenius plots led to theoretical determination of thermodynamic parameters of both the standared state (i.e., ΔHo, ΔGo, ΔSo ) and transition state (i.e., Ea, ΔH, ΔG, ΔS*) for the formation of (125I-antiCA15-3 antibody /CA15-3) complex. The thermodynamic data shown that the binding reaction is an entropically driven reaction and suggest an involvement of hydrophobic forces in the stabilization of complexes.

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