Enolate Stabilization by Anion-π Interactions: Deuterium Exchange in Malonate Dilactones on π-Acidic Surfaces.

Of central importance in chemistry and biology, enolate chemistry is an attractive topic to elaborate on possible contributions of anion-π interactions to catalysis. To demonstrate the existence of such contributions, experimental evidence for the stabilization of not only anions but also anionic intermediates and transition states on π-acidic aromatic surfaces is decisive. To tackle this challenge for enolate chemistry with maximal precision and minimal uncertainty, malonate dilactones are covalently positioned on the π-acidic surface of naphthalenediimides (NDIs).

Ring Tension Applied to Thiol-Mediated Cellular Uptake.

The objective of the study was to explore the potential of ring tension in cyclic disulfides for thiol-mediated cellular uptake. Fluorescent probes that cannot enter cells were equipped with cyclic disulfides of gradually increasing ring tension. As demonstrated by flow cytometry experiments, uptake into HeLa Kyoto cells increased with increasing tension.

Supramolecular ssDNA templated porphyrin and metalloporphyrin nanoassemblies with tunable helicity.

Free-base and nickel porphyrin-diaminopurine conjugates were formed by hydrogen-bond directed assembly on single-stranded oligothymidine templates of different lengths into helical multiporphyrin nanoassemblies with highly modular structural and chiroptical properties. Large red-shifts of the Soret band in the UV/Vis spectroscopy confirmed strong electronic coupling among assembled porphyrin-diaminopurine units. Slow annealing rates yielded preferentially right-handed nanostructures, whereas fast annealing yielded left-handed nanostructures.

Formation and helicity control of ssDNA templated porphyrin nanoassemblies.

We report the formation of left- (M-helix) and right-handed (P-helix) nanoassemblies of a porphyrin-diaminopurine conjugate (Por-DAP) templated by a single stranded oligodeoxythymidine (dT40) via directional hydrogen bonding. The supramolecular helicity can be controlled by the ionic strength, Por-DAP : dT40 ratio, and annealing rate.

Highly sensitive and selective spectroscopic detection of mercury(II) in water by using pyridylporphyrin-DNA conjugates.

Single-labeled pyridylporphyrin-DNA conjugates are reported as highly sensitive and selective spectroscopic sensors for mercury(II) ions in water. The effects of chemical structure (thymine versus adenine), number of nucleotides (monomer versus octamer), and porphyrin metalation (Zn versus free base) on the sensitivity and selectivity of mercury(II) detection are explored. The results indicated that pyridylporphyrin rather than the nucleobase plays a crucial role in mercury(II) sensing, because porphyrin conjugates with both adenosine and thymidine exhibited excellent mercury(II) detection.

Porphyrin-DNA conjugates: porphyrin induced adenine-guanine homoduplex stabilization and interduplex assemblies.

DNA has found widespread uses as a nanosized scaffold for assembly of patterned multichomophoric nanostructures. Herein we report the synthesis, self-assembly, stability, and spectroscopic studies of short alternating non-self-complementary DNA sequences 5'-(dGdA)(4) and 5'-(dAdG)(4) with non-charged tetraarylporphyrins covalently linked to the 5' position of deoxyadenosine or deoxyguanosine via a phosphate or amide linker. The linker, the metal in the porphyrin coordination center, and the neighboring nucleobase have very distinct effects on the duplex formation of porphyrin-deoxyguanosine-deoxyadenosine oligodeoxynucleotides.

Chiroptical detection of condensed nickel(II)-Z-DNA in the presence of the B-DNA via porphyrin exciton coupled circular dichroism.

Here, we report a highly sensitive and specific chiroptical detection method of condensed left-handed Z-DNA in the presence of canonical right-handed B-DNA. The selective formation of a left-handed cytosine-guanine oligonucleotide (CG ODN) in the presence of a right-handed adenine-thymine oligonucleotide (AT ODN) was induced by millimolar concentrations of NiCl(2) and confirmed by electronic circular dichroism. The nickel(II) induced B- to Z-DNA transition of the CG ODN was accompanied by the concurrent condensation of the Ni(II)-Z-DNA, as confirmed by resonance light scattering, transmission spectroscopy, and centrifugation.