Room-temperature phosphorescence of anilinonaphthalenesulfonate “fluorescence probe” compounds

2,6-anilinonaphthalenesulfonate (2,6-ANS) and 2,6-toluidinonaphthalenesulfonate (2,6-TNS) exhibit room-temperature phosphorescence when absorbed on filter paper, but the corresponding 1,8-isomers (1,8-ANS and 1,8-TNS) do not. The phosphorescence of the 2,6-isomers and nonphosphorescence of the 1,8-isomers is also found to hold in rigid glass at 77 K. No phosphorescence was detectable from N-phenyl-1-napthylamine at room temperature or 77 K, indicating that intramolecular hydrogen bonding in the 1,8-isomers isomers is not an essential feature inhibiting phosphorescence. Very effective heavy-atom enhancement of the phosphorescences of 2,6-ANS and 2,6-TNS by sodium iodide is observed.     

DNA damage by fasicularin

Fasicularin is a structurally novel thiocyanate-containing alkaloid isolated from the ascidian Nephteis fasicularis. Early biological experiments suggested that this compound's cytotoxic properties may stem from its ability to damage cellular DNA. Sequence gel analysis reveals that treatment of a 5'-32P-labeled DNA duplex with fasicularin in pH 7.0 buffer causes strand cleavage selectively at guanine residues. Further experiments indicate that production of these base-labile lesions in DNA involves alkylation of guanine residues by a fasicularin-derived aziridinium ion. This work reveals fasicularin as the first natural product found to generate a DNA-alkylating aziridinium ion via a mechanism analogous to the clinically used anticancer drugs mechlorethamine, melphalan, and chlorambucil.     

Measurement and standardisation of food colour

Summary Techniques for the measurement of colour are required widely by the food industry. Where such measurements are used only locally then few problems arise from non standard measurement methods or calibrations. If however, such measurements are to be used as quality criteria or to meet specifications set by an exterior customer, problems can result from disagreement over colour measurements. There is a clear need for standardisation to improve the transferability of measurements. A good example of this problem and its solution is seen in the tomato industry. Further studies on other colours have shown the limits within which a calibrant is useful.     

A thickness independent radiochromic film dosimetry system

A new radiochromic thin film dosimeter has been developed for use in radiation processing. The dosimeter's properties are similar to those of the commercially available FWT-60-00 Radiochromic Detectors with three key differences: 1) a lower sensitivity allows reading the optical density at the peak of the absorbtion spectrum (ca. 600 nm) for absorbed doses to over 50 kGy, 2) a radiation-insensitive dye additive allows for automatic thickness correction, and 3) another additive extends to higher doses the agreement between gamma and E-beam calibrations. The dosimeter is analyzed for its sensitivity, temperature and humidity dependencies, stability, reproducibility, and agreement of gamma and E-beam calibrations.     

N- and P-channel transport behavior in thin film transistors based on tricyanovinyl-capped oligothiophenes

We report the structural and electrical characterization of thin films of organic semiconductor molecules consisting of an oligothiophene core capped with electron-withdrawing tricyanovinyl (TCV) groups. X-ray diffraction and atomic force microscopy of evaporated films of three different TCV-capped oligothiophenes showed that the films were highly crystalline. Electrical transport was measured in thin film transistors employing silver source and drain contacts and channel probes to correct for contact resistance. Three compounds exhibited n-channel (electron) conduction consistent with cyclic voltametry data that indicated they undergo facile reduction. Maximum electron mobilities were 0.02 cm2/V.s with an on/off current ratio of 10(6). A fourth end-capped molecule, TCV-6T-TCV, which had six thiophene rings, exhibited both p- and n-channel transport. Overall, these results confirm that substitution of oligothiophene cores with electron-withdrawing groups is a useful strategy to achieve electron-transporting materials.     

Calorimetrically measurable enthalpic isotope effect

Calorimetric techniques have revealed that the enthalpy of reaction with water is more exothermic by about 2.2 kcal/mol, for the perdeuteriated naphthalene anion radical (K+C10D8*-(s) + H2O(liq) --> 1/2C10D8H2(s) + 1/2C10D8(s) + KOH(aq)) than it is for the perprotiated system. These results, when coupled with the known enthalpy of electron transfer between naphthalene and its perdeuteriated analogue imply that the heat of hydrogenation of naphthalene decreases by about 1.8 kcal/mol upon perdeuteriation of the naphthalene.     

Fast volumetric spatial-spectral MR imaging of hyperpolarized C-labeled compounds using multiple echo 3D bSSFP

Purpose

The goal of this work was to develop a fast 3D chemical shift imaging technique for the noninvasive measurement of hyperpolarized ¹³C-labeled substrates and metabolic products at low concentration.

Materials and Methods

Multiple echo 3D balanced steady state magnetic resonance imaging (ME-3DbSSFP) was performed in vitro on a syringe containing hyperpolarized [1,3,3-2H3; 1-¹³C]2-hydroxyethylpropionate (HEP) adjacent to a ¹³C-enriched acetate phantom, and in vivo on a rat before and after intravenous injection of hyperpolarized HEP at 1.5 T. Chemical shift images of the hyperpolarized HEP were derived from the multiple echo data by Fourier transformation along the echoes on a voxel by voxel basis for each slice of the 3D data set.

Results

ME-3DbSSFP imaging was able to provide chemical shift images of hyperpolarized HEP in vitro, and in a rat with isotropic 7-mm spatial resolution, 93 Hz spectral resolution and 16-s temporal resolution for a period greater than 45 s.

Conclusion

Multiple echo 3D bSSFP imaging can provide chemical shift images of hyperpolarized ¹³C-labeled compounds in vivo with relatively high spatial resolution and moderate spectral resolution. The increased signal-to-noise ratio of this 3D technique will enable the detection of hyperpolarized ¹³C-labeled metabolites at lower concentrations as compared to a 2D technique.