Abstract
The couple Calix[4]arene-1,3-O-diphosphorous acid (C4diP) and zinc ions (Zn2+) acts as a synergistic DNA binder. Silicon NanoTweezer (SNT) measurements show an increase in the mechanical stiffness of DNA bundles by a factor of >150, at Zn2+ to C4diP ratios above 8, as compared to Zinc alone whereas C4diP alone decreases the stiffness of DNA. Electroanalytical measurements using 3D printed devices demonstrate a progression of events in the assembly of C4diP on DNA promoted by zinc ions. A mechanism at the molecular level can be deduced in which C4diP initially coordinates to DNA by phosphate-phosphate hydrogen bonds or in the presence of Zn2+ by Zn2+ bridging coordination of the phosphate groups. Then, at high ratios of Zn2+ to C4diP, interdigitated dimerization of C4diP is followed by cross coordination of DNA strands through Zn2+/C4diP inter-strand interaction. The sum of these interactions leads to strong stiffening of the DNA bundles and increased inter-strand binding.
Highlights
DNA is one of the key bio-polymers in life, encoding the information required to build organisms
In a separate experiment using only one bundle, when C4diP has been injected after Zn2+, a dramatic increase of DNA stiffness to 33.5 N m−1 and DNA viscous losses of 5.65 × 10−5 N s m−1 has been observed
Injection of histidine reverses the effect,. This complexation is in agreement with the observation, using Electrospray/Mass Spectrometry (ES/MS), of a triple complex C4diP/Zn2+/Histidine complex by Perret[14]
Summary
DNA is one of the key bio-polymers in life, encoding the information required to build organisms. Artificial DNA binders present a great interest in the biomedical field[4] They can be used in various ways, such as the transportation of DNA through the cell membrane in transfection or gene therapy[5] for blocking a specific DNA sequence to avoid the transcription of a specific gene[6] or arresting DNA replication in cancer treatment[7]. Cationic calix[n]arene derivatives have been reported to be efficient DNA binders[10] Such derivatives present several drawbacks in biology, including toxicity due to the destabilization of cellular membranes possessing negative potential or non-specific electrostatic aggregation by negatively charged DNA11. Claude Bernard Lyon 1, CNRS, CPE Lyon, ICBMS UMR 5246, 43 Boulevard du 11 Novembre 1918, F-69622, Lyon, France. Correspondence and requests for materials should be addressed to A.W.C
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