title: Real-time monitoring of formaldehyde-induced DNA-lysozyme cross-linking with piezoelectric quartz crystal impedance analysis.
abstract: A novel method for monitoring, in real time, the formaldehyde (FA)-induced DNA-protein cross-linking process with the piezoelectric quartz crystal impedance (PQCI) technique is proposed. The method was used to monitor FA-induced DNA-lysozyme cross-link formation. Lysozyme was directly immobilized on the silver electrode surface of a piezoelectric quartz crystal by adsorption. The lysozyme-coated piezoelectric sensor was in contact with FA and DNA solutions. The time courses of the resonant frequency and equivalent circuit parameters of the sensor during the cross-linking were simultaneously obtained and are discussed in detail. On the basis of the feature of the multi-dimensional information provided by the PQCI technique, it was concluded that the observed frequency decrease could be mainly ascribed to the mass increase resulting from the cross-linking. According to the frequency decrease with time, the kinetics of the cross-linking process were quantitatively studied. A piezoelectric response model for the cross-linking was theoretically derived. Fitting the experimental data to the model, the kinetic parameters, such as the binding and dissociation rate constants (k(1) and k(-1)) and the cross-linking equilibrium constant (Ka), were determined. At 37 degrees C, the k(1), k(-1) and Ka values obtained were 7.0 (+/-0.1) x 10(-5) (microg ml(-1))(-1) s(-1), 6.6 (+/-0.1) x 10(-3) s(-1) and 1.06 (+/-0.02) x 10(-2) (microg ml(-1))(-1), respectively.
authors.affiliation: College of Chemistry and Chemical Engineering, Hunan University, Changsha, China. youanmao@cmmail.com
authors.forename: Y
authors.initials: Y
authors.lastname: Mao
authors.forename: W
authors.initials: W
authors.lastname: Wei
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: S
authors.initials: S
authors.lastname: Zhang
authors.forename: X
authors.initials: X
authors.lastname: Rao
mesh_terms: D004247:DNA / Q000187:drug effects / Q000378:metabolism*; D017097:Electric Impedance; D005557:Formaldehyde / Q000494:pharmacology*; D006801:Humans; D008956:Models, Chemical; D009113:Muramidase / Q000378:metabolism*
chemical_list: D005557:Formaldehyde; D004247:DNA; D009113:Muramidase