Sequence-specific activation of the DNA sensor cGAS by Y-form DNA structures as found in primary HIV-1 cDNA.

Cytosolic DNA that emerges during infection with a retrovirus or DNA virus triggers antiviral type I interferon responses. So far, only double-stranded DNA (dsDNA) over 40 base pairs (bp) in length has been considered immunostimulatory. Here we found that unpaired DNA nucleotides flanking short base-paired DNA stretches, as in stem-loop structures of single-stranded DNA (ssDNA) derived from human immunodeficiency virus type 1 (HIV-1), activated the type I interferon-inducing DNA sensor cGAS in a sequence-dependent manner.

Pseudo-complementary PNA actuators as reversible switches in dynamic DNA nanotechnology.

The structural reorganization of nanoscale DNA architectures is a fundamental aspect in dynamic DNA nanotechnology. Commonly, DNA nanoarchitectures are reorganized by means of toehold-expanded DNA sequences in a strand exchange process. Here we describe an unprecedented, toehold-free switching process that relies on pseudo-complementary peptide nucleic acid (pcPNA) by using a mechanism that involves double-strand invasion.

Reversible light switch for macrocycle mobility in a DNA rotaxane.

A recent trend in DNA nanotechnology consists of the assembly of architectures with dynamic properties that can be regulated by employing external stimuli. Reversible processes are important for implementing molecular motion into DNA architectures as they allow for the regeneration of the original state. Here we describe two different approaches for the reversible switching of a double-stranded DNA rotaxane architecture from a stationary pseudorotaxane mode into a state with movable components.

Input-dependent induction of oligonucleotide structural motifs for performing molecular logic.

The K(+)-H(+)-triggered structural conversion of multiple nucleic acid helices involving duplexes, triplexes, G-quadruplexes, and i-motifs is studied by gel electrophoresis, circular dichroism, and thermal denaturation. We employ the structural interconversions for perfoming molecular logic operations, as verified by fluorimetry and colorimetry. Short G-rich and C-rich cDNA and RNA single strands are hybridized to produce four A-form and B-form duplexes.

A trifluoromethylphenyl diazirine-based SecinH3 photoaffinity probe.

The synthesis of a trifluoromethylphenyl diazirine photoaffinity probe of the cytohesin inhibitor SecinH3 is described. The probe exhibits improved labelling efficiency over a benzophenone-based probe and thus is more suitable for photoaffinity labelling in complex biological samples.

Assembly of dsDNA nanocircles into dimeric and oligomeric aggregates.

The assembly of double-stranded (ds) DNA nanocircles both by hybridization with branched oligodeoxynucleotides (ODNs) and by intercalation was analyzed by atomic force microscopy (AFM). Branched ODNs ligated to single-stranded (ss) gap regions of dsDNA nanocircles led to defined, dumbbell-shaped architectures. ODNs containing an aromatic intercalator yielded oligomeric aggregates.

A double-stranded DNA rotaxane.

Mechanically interlocked molecules such as rotaxanes and catenanes have potential as components of molecular machinery. Rotaxanes consist of a dumb-bell-shaped molecule encircled by a macrocycle that can move unhindered along the axle, trapped by bulky stoppers. Previously, rotaxanes have been made from a variety of molecules, but not from DNA.

Photocleavable initiator nucleotide substrates for an aldolase ribozyme.

We have previously reported the in vitro selection of a ribozyme that catalyzes an aldol reaction between a levulinic amide aldol donor and a benzaldehyde substrate. The selection scheme involved the priming of the RNA library with a levulinic amide aldol donor group that was introduced via transcription priming in the presence of a modified guanosine mononucleotide derivative. Here we provide a detailed description of the synthesis of the ribozyme substrates and the substrate oligonucleotides used for its isolation and characterization.