[2]Rotaxanes comprising a macrocylic Hamilton receptor obtained using active template synthesis: synthesis and guest complexation

<p>A macrocyclic ring comprising multiple hydrogen-bonding sites as well as metal-chelating sites is shown to play the role of ligand in active templated, copper-catalysed [2]rotaxane formation via Huisgen and Glaser reactions. The crystallographic structure and copper ion binding studies are provided for the free macrocycle, along with molecular modelling, barbital, N,N′-trimethyleneurea and copper (I) binding information for the new rotaxanes.</p

Macrocyclic Metal Complex–DNA Conjugates for Electrochemical Sensing of Single Nucleobase Changes in DNA

The direct incorporation of macrocyclic cyclidene complexes into DNA via automated synthesis results in a new family of metal-functionalized DNA derivatives that readily demonstrate their utility through the ability of one redox-active copper­(II)-containing strand to distinguish electrochemically between all four canonical DNA nucleobases at a single site within a target sequence of DNA

Reversible Photocapture of a [2]Rotaxane Harnessing a Barbiturate Template

Photoirradiation of a hydrogen-bonded molecular complex comprising acyclic components, namely, a stoppered thread (<b>1</b>) with a central barbiturate motif and an optimized doubly anthracene-terminated acyclic Hamilton-like receptor (<b>2b</b>), leads to an interlocked architecture, which was isolated and fully characterized. The sole isolated interlocked photoproduct (Φ = 0.06) is a [2]­rotaxane, with the dimerized anthracenes assuming a head-to-tail geometry, as evidenced by NMR spectroscopy and consistent with molecular modeling (PM6). A different behavior was observed on irradiating homologous molecular complexes <b>1</b>⊂<b>2a</b>, <b>1</b>⊂<b>2b</b>, and <b>1</b>⊂<b>2c</b>, where the spacers of <b>2a</b>, <b>2b</b>, and <b>2c</b> incorporated 3, 6, and 9 methylene units, respectively. While no evidence of interlocked structure formation was observed following irradiation of <b>1</b>⊂<b>2a</b>, a kinetically labile rotaxane was obtained on irradiating the complex <b>1</b>⊂<b>2c</b>, and ring slippage was revealed. A more stable [2]­rotaxane was formed on irradiating <b>1</b>⊂<b>2b</b>, whose capture is found to be fully reversible upon heating, thereby resetting the system, with some fatigue (38%) after four irradiation–thermal reversion cycles

Remote Photoregulated Ring Gliding in a [2]Rotaxane via a Molecular Effector

A molecular barbiturate messenger, which is reversibly released/captured by a photoswitchable artificial molecular receptor, is shown to act as an effector to control ring gliding on a distant hydrogen-bonding [2]­rotaxane. Thus, light-driven chemical communication governing the operation of a remote molecular machine is demonstrated using an information-rich neutral molecule

Photocontrolled Binding and Binding-Controlled Photochromism within Anthracene-Modified DNA

Modified DNA strands undergo a reversible light-induced reaction involving the intramolecular photodimerization of two appended anthracene tags. The photodimers exhibit markedly different binding behavior toward a complementary strand that depends on the number of bases between the modified positions. By preforming the duplex, photochromism can be suppressed, illustrating dual-mode gated behavior

Electroporation and Microinjection Successfully Deliver Single-Stranded and Duplex DNA into Live Cells as Detected by FRET Measurements

<div><p>Förster resonance energy transfer (FRET) technology relies on the close proximity of two compatible fluorophores for energy transfer. Tagged (Cy3 and Cy5) complementary DNA strands forming a stable duplex and a doubly-tagged single strand were shown to demonstrate FRET outside of a cellular environment. FRET was also observed after transfecting these DNA strands into fixed and live cells using methods such as microinjection and electroporation, but not when using lipid based transfection reagents, unless in the presence of the endosomal acidification inhibitor bafilomycin. Avoiding the endocytosis pathway is essential for efficient delivery of intact DNA probes into cells.</p></div

Single Site Discrimination of Cytosine, 5‑Methylcytosine, and 5‑Hydroxymethylcytosine in Target DNA Using Anthracene-Tagged Fluorescent Probes

The ability to discriminate between epigenetic variants in DNA is a necessary tool if we are to increase our understanding of the roles that they play in various biological processes and medical conditions. Herein, it is demonstrated how a simple two-step fluorescent probe assay can be used to differentiate all three major epigenetic variants of cytosine at a single locus site in a target strand of DNA

Schematic of Cy3 and Cy5 tagged DNA.

<p>a) Complementary DNA strands are individually tagged with Cy3 and Cy5 fluorophores (<b>S1</b> and <b>S2</b> respectively). When in close enough proximity the Cy3 can donate energy to Cy5 through FRET. In this case, FRET can only occur when the two complementary strands form a duplex. b) Single strand DNA can be tagged at either end with Cy3 and Cy5 (<b>S3</b>). FRET can occur as long as the single strand remains intact.</p

Fixed cell confocal microscopy images.

<p>Left: Cy3 and Cy5 tagged DNA duplex (<b>S1:S2</b>) added to fixed/permeabilised cells and imaged using confocal microscopy. Images A/E represents the Cy3 channel; B/F the Cy5 channel; C/G the bright field channel and D/H an overlay of all the channels. Images A–D are excited with the 543 nm laser. Images E–H are excited with both the 543 and 633 nm lasers. Right: Intracellular fluorescence intensity from images A/B and E/F. Data are expressed as mean ± s.e.m from at least ten cells (p<0.001).</p

Tagged oligonucleotides synthesized.

<p>Tagged oligonucleotides synthesized.</p