The human telomere sequence, (TTAGGG)4, in the absence and presence of cosolutes: a spectroscopic investigation.

Historically, biophysical studies of nucleic acids have been carried out under near ideal conditions, i.e., low buffer concentration (e.g., 10 mM phosphate), pH 7, low ionic strength (e.g., 100 mM) and, for optical studies, low concentrations of DNA (e.g., 1×10⁻6 M). Although valuable structural and thermodynamic data have come out of these studies, the conditions, for the most, part, are inadequate to simulate realistic cellular conditions. The increasing interest in studying biomolecules under more cellular-like conditions prompted us to investigate the effect of osmotic stress on the structural and thermodynamic properties of DNA oligomers containing the human telomere sequence (TTAGGG). Here, we report the characterization of (TTAGGG)4 in potassium phosphate buffer with increasing percent PEG (polyethylene glycol) or acetonitrile. In general, the presence of these cosolutes induces a conformational change from a unimolecular hybrid structure to a multimolecular parallel stranded structure. Hence, the structural change is accompanied with a change in the molecularity of quadruplex formation.

Efficient syntheses of macrocycles ranging from 22-28 atoms through spontaneous dimerization to yield bis-hydrazones.

Acid treatment of a triazine displaying both a tethered acetal and BOC-protected hydrazine group leads to spontaneous condensation to yield macrocyclic dimers in excellent yields and purity. The bis-triazinyl hydrazones that form are characterized by 1H-NMR, 13C-NMR, 1H-COSY spectroscopy, X-ray diffraction, and mass spectrometry. By varying the length of the tether-the condensation product of an amino acid and amino acetal-rings comprising 22-28 atoms can be accessed. Glycine and ß-alanine were used for the amino acid. The amino acetal comprised 2, 3 or 4 carbon atoms in the backbone. High-performance liquid chromatography (HPLC) was employed to assess purity as well as to fingerprint the six homodimeric products. By combining the protected monomers and subjecting them to acid, mixtures of homodimers and heterodimers are obtained. When all six protected monomers are combined, at least 14 of the 21 theoretical dimeric products are observed by HPLC. Single crystal X-ray diffraction and solution NMR studies reveal the diversity of shapes available to these molecules.

Protective Effects of 17ß-Estradiol on Benzo(e) pyrene[B(e)P]-induced Toxicity in ARPE-19 cells.

PURPOSE: The aim of this study was to examine the effect of 17ß-estradiol on Benzo(e)pyrene [B(e)P]-induced toxicity in ARPE-19 cells. METHODS: We pretreated ARPE-19 cells with 20 nM and 40 nM 17ß-estradiol for 6 hours, followed by addition of 300 µM B(e)P for additional 24 hours. Cell viability was measured using Trypan blue dye-exclusion assay. JC-1 assay was performed to measure mitochondrial membrane potential (ΔΨm). For a quantitative estimation of cell death, apoptotic markers such as caspase-3/7, caspase-9, and caspase-12 were measured. RESULTS: Our results demonstrated that when treated with B(e)P, the viability and ΔΨm of ARPE-19 cells declined by 25% and 63%, respectively (P < 0.05). However, pretreating with 17ß-estradiol increased the viability of ARPE-19 cells by 21% (20 nM) and 10% (40 nM) (P < 0.05). Furthermore, the significantly reduced ΔΨm in ßE+B(e)P treated cells ARPE-19 cells was restored by pre-treatment with 17ß-estradiol- ΔΨm was increased by 177% (20 nM) and 158% (40 nM) (P < 0.05). We further observed a significant up-regulation in the activity of Caspases-3/7, -9, and -12 in B(e)P-treated ARPE-19 cells. However, 17ß-estradiol treatment significantly reduced the activity of all apoptotic markers (P < 0.05). CONCLUSION: In conclusion, our results demonstrate that 17ß-estradiol protects ARPE-19 cells against B(e)P-induced toxicity by decreasing apoptosis, preventing cell death, and restoring mitochondrial membrane potential.