Bio-bar-code-based DNA detection with PCR-like sensitivity

Novel two-component oligonucleotide-modified nanoparticle probes have been designed and used in a bio-bar-code assay with a 500 zeptomolar target DNA sensitivity limit.     

Emulsifier-free emulsion polymerization produces highly charged, monodisperse particles for near infrared photonic crystals

We have developed emulsifier-free, emulsion polymerization recipes for the synthesis of highly charged, monodisperse latex particles of diameters between 500 and 1100 nm. These latexes consist of poly[styrene-(co-2-hydroxyethyl methacrylate)] spherical particles whose surfaces are functionalized with sulfate and carboxylic acid groups. These highly charged, monodisperse particles readily self-assemble into robust, three-dimensionally ordered crystalline colloidal array photonic crystals that Bragg diffract light in the near infrared spectral region. By altering the particle number density, the diffraction wavelength can be tuned from approximately 1000 to approximately 4000 nm.     

Synthesis of substituted pyrrolo[2,3-e][1,3,4]thiadiazine 4,4-dioxides

A series of substituted pyrrolo[2,3-e][1,3,4]thiadiazine 4,4-dioxides is synthesized from 1-substituted-2-amino-3-cyanomethylsulfonyl-4,5-dimethylpyrroles.     

Fluorescence anisotropy imaging reveals localization of meso-tetrahydroxyphenyl chlorin in the nuclear envelope

We have measured the intrinsic fluorescence anisotropies of six photosensitizers in homogeneous solution, and we have imaged the anisotropies of these sensitizers in tumor cell monolayers using polarization-sensitive laser-scanning confocal microscopy. The intrinsic anisotropies are unremarkable and are within the approximate range of 0.2–0.27. In cells, however, very interesting behavior is exhibited by meso -tetrahydroxyphenyl chlorin (mTHPC). Polarization-sensitive images of mTHPC's fluorescence show a pronounced banding of alternating high and low anisotropy consistent with an ordering of the sensitizer in the nuclear envelope, indicating that this structure is a target of photodynamic damage with this sensitizer. None of the other sensitizers exhibits localization to the nuclear envelope. The frequency distributions of the intracellular anisotropies of the sensitizers exhibit variable peaks and widths. An unusual case is that of Photofrin, with a peak in its anisotropy frequency distribution of –0.12. The change from a positive intrinsic anisotropy in homogeneous solution to a negative value in cells suggests an environmentally induced change in the relative orientations of the absorption and emission dipole moments.     

Role of Hydrogen Peroxide in the Cytotoxic Effects of UVA/B Radiation on Mammalian Cells

Effects of selenium (Se) deficiency on the sensitivity of murine leukemia L1210 cells to broad band UVA/B radiation (310–400nm) have been investigated. Cells rendered glutathione peroxidase (GPX) deficient by shortterm (2–3week) growth in 1% serum/RPMI medium without added Se [LSe(-) cells] were found to be much less resistant to clonally assessed UVA/B lethality than Se-supplemented controls [LSe(+) cells]. By contrast, long-term (>20 week) Se-deprived [L'Se(-)] cells whose catalase (CAT) activity was elevated >100-fold were far more resistant to UVA/B than LSe(+) cells. Similar trends were observed for cells irradiated in 1% serum/RPMI or Hank's medium. Whereas the CAT inhibitor 3-amino-1,2,4-triazole had no effect on LSe(+) photosensitivity, it produced a large increase in L' Se(-) photosensitivity. These findings are consistent with H₂O₂ in-termediacy in photokilling and suggest that L1210 cells depend mainly on GPX for protection against this species but switch to overexpressed CAT after chronic Se deprivation. In agreement with this, steady-state H₂O₂ levels measured by H₂O₂ electrode during UVA/B exposure were higher in LSe(-) than LSe(+) suspensions but much lower (barely detectable) in L' Se(-) suspensions. Cytotoxic effects of UVA/B and variations thereof resulting from Se manipulation could be mimicked by treating cells with glucose oxidase in the presence of D-glucose, providing further support for H₂O₂ involvement. Whether UVA/B-generated H₂O₂ is directly cytotoxic or gives rise to a more damaging species such as hydroxyl radical (HO) is presently unknown.     

High charge-carrier mobility in an amorphous hexaazatrinaphthylene derivative

An isomeric mixture of a tris(pentafluorobenzyl ester) derivative of hexaazatrinaphthylene forms stable amorphous films with an effective charge-carrier mobility of 0.02 cm2/Vs, while the pure 2,8,15-isomer exhibits widely differing morphologies and carrier mobilities (0.001-0.07 cm2/Vs), depending critically on the processing conditions.