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The methods of conductance and capacitance relaxation were used to monitor hybridization of short sequences of DNA on the surface of lipid membranes (s-BLM) supported on thin platinum or gold layers covered by 1-dodecanethiol. The 15-mer-5H -hexadecyl-deoxythymidylic modi®ed by palmitic acid (C 16 pdT 15 ) was used as a DNA sensor that was incorporated into the BLM by the C 16 chain. The interaction of C 16 pdT 15 with s-BLM resulted in decrease membrane capacitance and conductance. The DNA hybridization on s-BLM surface resulted in an increase of s-BLM conductance, however, interaction of s-BLM modi®ed by C 16 pdT 15 with noncomplementary oligonucleotide did not change membrane conductance. The capacitance relaxation following symmetrical voltage jumps allowed us to study the dynamics of the reorientation dipole moments of the membrane. The unmodi®ed s-BLM were characterized by two relaxation components: fast t 1 20.3 AE 0.2 ms and slow t 2 590.3AE 175 ms. Modi®cation of the lipid layer by C 16 pdT 15 resulted in a decrease of amplitude of the slower component below detectable limit, while hybridization resulted in recovery of two relaxation times. Similar behavior was characterized for the free standing BLM. The changes of relaxation times might be due to the in¯uence of the hybridization process on the two-dimensional architecture of the phospholipid layer, for example on the size of the lipid clusters.

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