DNA-BINDING AND HYBRIDIZATION ON GOLD AND DERIVATIZED SURFACES

The binding of various single-and double-stranded DNAs onto gold and d erivatized gold surfaces, and their hybridization with complementary D NA species, have been investigated using a quartz crystal microbalance (QCM) and surface plasmon resonance (SPR). The DNA species employed w ere a 21-mer oligonucleotide (Mbo21), several double-stranded plasmid DNAs (7.2 kilobases) modified by incorporation of alpha-phosphothio-nu cleotides into the ends of the linearized plasmid DNA (pPS-S-x, where x represents the number of alpha-phosphothio-nucleotides), and a 30-me r oligonucleotide having a mercaptohexyl group at the 5'-phosphate end (BS1-SH). Both QCM and SPR data reveal that unmodified DNA does not s pontaneously adsorb onto underivatized gold surfaces from aqueous solu tions. Modification of the gold surface through the attachment of an i onizable thiol compound, 2-dimethylaminoethanethiol hydrochloride (DMA ET), allows DNA to adsorb through electrostatic interactions. SPR meas urements confirm the presence of Mbo21 DNA on the DMAET-modified gold surface. Immobilized Mbo21, however, does not undergo hybridization. Q CM and SPR data suggest that pPS-S-4, pPS-S-50, and BSI-SH DNA all ass ume a flat orientation on gold. No hybridization of single-stranded DN A to gold-immobilized pPS-(4), and pPS-S-50, could be detected. In con trast, 30-mer DNA. binding from solution to the complement BS1-SH immo bilized on gold reveals hybridization of the DNA strands. (C) 1997 Pub lished by Elsevier Science S.A.