Electron transfer of plurimodified DNA SAMs.
An STM-based current-voltage (I/V) investigation of deoxyribonucleic acid (DNA) 18 base pair (bp) oligonucleotide monolayers on gold is presented. Three bases of each of the immobilized and complementary strands were modified with either iodine or phenylethylene moieties. The oligonucleotides were immobilized on template stripped gold (tsg) surfaces and characterized by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). AFM imaging showed that monolayers of the expected height were formed. A comparative study of normal, halogenated, and phenyl-modified DNA was made with the STM in tunneling spectroscopy (TS) mode. I/V spectroscopic measurements in the range +/-250 mV on both single- and double-stranded (ds) DNA monolayers (modified and unmodified) showed that for negative substrate bias (U(sub)) electron transfer is more efficient through a phenyl-modified monolayer than through normal or halogenated DNA. This effect was particularly clear below a threshold bias of -100 mV. For positive U(sub), unmodified ds DNA was found to conduct slightly better than the modified strands. This is presumably caused by greater order in the unmodified versus modified DNA monolayers. Modifications on the immobilized (thiolated) strand seem to improve electron transport through the DNA monolayer more than modifications on the complementary (not surface-bound) strand.
Rospigliosi
Alessandro
A
Department of Chemical Engineering, University of Cambridge, Pembroke Street, New Museum Site, Cambridge, United Kingdom. alessandro@rospigliosi.com
Ehlich
Rudolf
R
Hoerber
Heinrich
H
Middelberg
Anton
A
Moggridge
Geoff
G
D004247:DNA / Q000737:chemistry*; D004553:Electric Conductivity; D004563:Electrochemistry; D004583:Electrons; D006046:Gold / Q000737:chemistry*; D007455:Iodine / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D017348:Microscopy, Electron, Scanning Transmission; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D013499:Surface Properties
D009838:Oligodeoxyribonucleotides; D006046:Gold; D004247:DNA; D007455:Iodine