Application of an Optical Biosensor to Study the Interaction between Porphyrins and Wheat Germ Agglutinin

0Introduction Porphyrinderivativeshavebeenusedasphotosensitizersinphotodynamictherapy(PDT),anewapproachdevel opedforthetreatmentofcancer1].Cationwater solublepor phyrinsareofconsiderableinterestowingtotheirpossiblebio medicalapplications2].Inwhich,theinhibiteffectonthe growthmetabolismofE.coliandcancercellHL60ofmeso tetra(4N ethylacetatepyridyl)porphyrin(H2NEAE pp)and itsZn(Ⅱ)complexform(ZnNEAE pp)havebeenrecentlyin vestigated3,4].Toenhancetumor locationandanticancerac tivitiesofdr…

Application of an optical biosensor to study the interaction between porphyrins and wheat germ agglutinin

An optical biosensor with a stirred cuvette has been used to monitor the interaction of immobilized wheat germ agglutinin (WGA) with two water-soluble cationic porphyrins. The association constants (K _a) of the free base porphyrin and its Zn(II) complex form were 2.66 and 27.31×10⁵ L/mol at 20°C respectively. The interactions of the free base porphyrin were further investigated at temperatures between 15°C and 37°C. The thermodynamics parameters, changes in free energy, enthalpy and entropy, were −31.23, 22.92, 54.15 kJ/mol respectively. The heat capacity change was −355.53 J·mol⁻¹·K⁻¹. The binding was driven by entropic contribution, and showed strong enthalpy-entropy compensation. It was governed primarily by hydrophobic forces. Foundation item: Supported by the National Natural Science Foundation of China (30370366) Biography: QIN Yimin (1976-), female, Ph. D., research direction: applied biochemistry and molecular biology.