Strong positive cooperativity in binding to the A3T3 repeat by Hoechst 33258 derivatives attaching the quinoline units at the end of a branched linker.

Hoechst 33258 derivatives with additional interacting moieties attached at the ends of branched linkers were synthesized, and their DNA binding properties were investigated with regard to the A3T3 repeat by measuring fluorescence spectra. The binding property of the ligand was investigated by fluorescence titration, and the titration data were analyzed using the McGhee-von Hippel method. Ligand 6Q with the quinolin-6-yloxyacetyl group and Ligand IQ with isoquinolin-6-yloxyacetyl group at the ends of the branched linkers exhibit highly positive cooperativity for the DNA having 5 A3T3 sites with 3 base-insertions between them with sequence selectivity. The strategy developed in this study may be generally applicable for designing ligands for repetitive DNA sequences.

Visualization of phosphatidylcholine (16:0/16:0) in type II alveolar epithelial cells in the human lung using imaging mass spectrometry.

Imaging mass spectrometry (MS) is an emerging technique that can detect numerous biomolecular distributions in a non-targeting manner. In the present study, we applied a mass imaging modality, mass microscopy, to human lung tissue and identified several molecules including surfactant constituents in a specific structure of the lung alveoli. Four peaks were identified using imaging MS, and the ion at m/z 772.5, in particular, was localized at some spots in the alveolar walls. Using an MS/MS analysis, the ion was identified as phosphatidylcholine (PC)(16:0/16:0), which is the main component of lung surfactant. In a larger magnification of the lung specimen, PC (16:0/16:0) was distributed in a mottled fashion in a section of the lung. Importantly, the distribution of PC (16:0/16:0) was identical to that of anti-SLC34A2 antibody immunoreactivity, which is known to be a specific marker of type II alveolar epithelial cells, in the same section. Our experience suggests that imaging MS has excellent potential in human pathology research.

Binding of two bis-bipyridine minor groove binders to a DNA template in the presence of Cu2+ ions.

Some diseases are associated with abnormally extended regions of triplet repeats. These repeating regions are an attractive target for both diagnostic and therapeutic goals. In an attempt to approach to this goal, we have focused on establishment of an allosteric binding mechanism, in which the binding of the ligand promotes the next ligand binding. In the previous study, we already reported that the ligand having the bipyridine unit for binding with Cu(2+) and the Hoechst33258 for binding to A(3)T(3) site displayed Cu(2+)- mediated assembly on the DNA with two A(3)T(3) sites. In this study, we synthesized the new ligands containing two bipyridine units attached to Hoechst33258 by different length linkers. It was expected that the bipyridine-Cu(2+) complexation would enhance assembly of a number of the ligand on the DNA sequence with repeating regions. UV spectroscopy has been used to demonstrate the binding of these ligands to a DNA template mediated by the complexation of Cu(2+) ions.

Recognition of DNA with assembly of minor groove binders mediated by metal complexation.

Genome-targeting molecules would have broad application as probes in genomic study. We recently developed the ligands (Bpy-H) connecting the Hoechst33258 skeleton for DNA binding and 2,2'-bipyridine for Cu(2+) complexation. It was shown that L-Bpy-H with a long linker exhibited Cu(2+)-mediated assembly on the DNA template having two A(3)T(3) sites in a ratio of 1:2:1 DNA-ligand-Cu(2+). Binding selectivity depends on the distance between the two A(3)T(3) sites of DNA. In contrast, S-Bpy-H having a short linker tended to form 1:2:2 DNA-ligand-Cu(2+) complex.