TEMPERATURE-DEPENDENT FORMATION OF A CONJUGATE BETWEEN TRIS(HYDROXYMETHYL)AMINOMETHANE BUFFER AND THE MALONDIALDEHYDE-DNA ADDUCT PYRIMIDOPURINONE

The stability of the major adduct formed between the endogenous produc t malondialdehyde (MDA) and deoxyguanosine, a pyrimidopurinone termed M(1)G-dR, was tested under a variety of conditions required for nuclei c acid manipulation. M(1)G-dR was found to be stable at neutral pH and 37 degrees C but to be unstable when stored at -20 degrees C in the p resence of Tris buffers. A new product with a characteristic absorptio n band at 350 nm was identified by H-1-NMR as an enamino-imine compris ed of one molecule of Tris, one molecule of MDA, and deoxyguanosine. T he formation of the conjugate was observed on reaction of Tris with M( 1)G-dR or its ring-opened derivative N-2-(3-oxo-1-propenyl)deoxyguanos ine. The Tris-M(1)G-dR conjugate was unstable in aqueous solutions at room temperature, undergoing hydrolysis. However, the Tris conjugate o f M(1)G base remained stable at room temperature in organic solvent. T he isolation and properties of a conjugate between M(1)G-dR and Tris s uggest that cross-links may form by reaction of MDA with DNA but they are likely to be unstable to hydrolysis.