Bis-triazolyl diguanosine derivatives as synthetic transmembrane ion channels

In nature, ion channels facilitate the transport of ions across biological membranes. The development of artificial ion channels that can mimic the fundamental functions of the natural ones

would be of great importance to biological research. Artificial ion channels based on nucleoside derivatives are expected to be biocompatible with functions that can be controlled by the

presence or absence of biologically relevant molecules. This protocol describes the detailed procedures for the synthesis and ion-channel activity of four diguanosine derivatives, each made

up of two guanosine moieties separated by a covalent linker (e.g., PEG). The procedure describes the preparation of guanosine azide and guanosine alkine building blocks, as well as the

preparation of four distinct synthetic linkers each containing either two alkynes or two azides. The diguanosine derivatives are synthesized using a 'one-pot' modular synthetic approach

based on Cu(I)-catalyzed azide and alkyne cycloaddition. The ion-channel activity of these diguanosine derivatives for the transportation of ions across a phospholipid bilayer is

investigated using voltage-clamp experiment. By using the PEG-containing diguanosine as an example, we describe how to determine the ion-channel activity in the presence of different metal

ions (e.g., Na+, K+ and Cs+) and the inhibition of the ion-channel activity using the nucleobase cytosine. The approximate time frame for the synthesis of the PEG dinucleoside is 3 d, and

that for the experiments to evaluate its ability to transport K+ ion across a phospholipid bilayer is ∼8–10 h.

This work was supported by the Board of Research in Nuclear Sciences (BNRS), Department of Atomic Energy (DAE) and Department of Biotechnology (DBT) India. The DFG (SFB 803, project A01) is

gratefully acknowledged. Y.P.K. and R.N.D. thank Council of Scientific and Industrial Research (CSIR), India, and R.N.D. thanks the Deutscher Akademischer Austauschdienst (DAAD) Exchange

Programme for a research fellowship.

Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, India

Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India

Institute of Organic and Biomolecular Chemistry, Georg-August-University Göttingen, Göttingen, Germany

J.D. and C.S. designed the experiments; Y.P.K. synthesized the compounds; R.N.D. and O.M.S. carried out the voltage-clamp experiments; and J.D. wrote the paper with the input from all the

authors.

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