DNA as a special biological molecular exhibits many advantages in designing addressable DNA logic gates, data storage and processing, which was based on the straightforward sequence-specific hybridization and the ability to specifically capture certain target molecules (e.g.protein, small molecules and metal ions).With the increased investigations it becomes highly important to protect information against illegal invasion at the molecular level.Although the unconventional molecular keypad lock provides a new approach for information protection and attracts increasing interest, the system with reset function is less developed.Under this situation, an electrochemically transduced keypad lock system with reset function could pave a new way for such a development.In this report, DNA containing PW17 was selected and self-assembled on the gold electrode.In the presence of 10 μmol/L Pb²⁺, Pb²⁺ induced the self-assembled DNA transformed into Pb²⁺-stabilized G-quadruplex.The formed Pb²⁺-stabilized G-quadruplex was investigated by differential pulse voltammetry, and a reduction peak at -0.365 V vs.Ag/AgCl was observed, which was due to the reduction of Pb²⁺existed in G-quadruplex.Based on the strong chelated interaction between Pb²⁺ and EDTA, EDTA could capture Pb²⁺from Pb²⁺-stabilized G-quadruplex to form Pb²⁺-EDTA, with G-quadruplex transforming into free DNA.Through alternatively applying Pb²⁺and EDTA, the reciprocal transformations between free DNA and Pb²⁺-stabilized G-quadruplex were achieved.Based on the results, with Pb²⁺and EDTA as inputs and self-assembled DNA on the gold electrode as work unit, an electrochemical DNA keypad lock was fabricated.The keypad lock was "ON" when subsequently inputting EDTA and Pb²⁺, and also it could be reset through applying 5 mmol/L EDTA.In contrast, the keypad lock was "OFF" when subsequently inputting Pb²⁺ and EDTA, and also it could be reset through applying 10 μmol/L Pb²⁺.Thus, the designed electrochemical keypad lock could be reset at least five times without signal lost.Based on the results, the keypad lock exhibited excellent resettable ability.

Key words: Pb²⁺, G-Quadruplex, electrochemistry, keypad lock