Isolation of the 9-fluorenylmethyl chloroformate derivative in the determination of sulphamethazine

Derivatisation of amine-containing analytes with 9-fluorenylmethyl chloroformate (FMOC) to form fluorescent adducts requires a large excess of FMOC. This excess hydrolyses to form FMOC-OH, which is also fluorescent. Solvent extraction has been investigated as a means of isolating the sulphamethazine (SMZ) adduct (FMOC-SMZ) from the hydrolysis product in order to perform rapid spectrophotometric or spectrofluorimetric assays. However, even under the most favourable pH conditions possible, FMOC-OH was not totally removed. Attempts to enhance the separation by reaction of FMOC-OH with 1-ethoxy-4-dichloro-S-triazinylnaphthalene (EDTN) or by acetylation were also unsuccessful. On the other hand, reaction of FMOC with mixed substrates, followed by two pentane extractions to remove the excess FMOC and direct injection into an HPLC provides the desired separations on a reversed phase column (RPLC) with methanol-modified, (pH 3.5) phosphate buffers. FMOC-SMZ is readily separated from FMOC-OH under all elution conditions, from the FMOC-amino acids (under gradient conditions or isocratically up to 75% methanol), and from other FMOC-sulphonamides and FMOC-dihydrofolate reductase inhibitors (isocratically up to 70% methanol). Hence conversion to the FMOC derivatives permits SMZ to be separated from all of the potential interferants tested by isocratic elution with 70% methanol in RPLC. Analysis for the amino acid derivatives of FMOC may be done without interference from SMZ in samples.     

Laser-Induced Fluorescence Imaging and Spectroscopy of GFP Transgenic Plants

Green fluorescent protein (GFP) and other fluorescent protein bioreporters can be used to monitor transgenes in plants. GFP is a valuable marker for transgene presence and expression, but remote sensing instrumentation for stand-off detection has lagged behind fluorescent protein marker biotechnology. However, both biology and photonics are needed for the monitoring technology to be fully realized. In this paper, we describe laser-induced fluorescence imaging and laser-induced fluorescence spectroscopy of GFP-transgenic plants in ambient light towards the application of remote sensing of transgenic plants producing GFP.     

Nuclei in the terminal parts of the r-process path

Half-life calculations for various decay processes have been made for neutron-rich elements with $\text{Z ≧ 90}$ and with neutron numbers between the β-stability line and the neutron-drip line. The calculations are based on the modified oscillator model. The results, which are highly dependent on the size of the N = 184 neutron gap predicted by the model, appear not to permit the population of the superheavy region through the r-process, in contradiction to the results of a recent investigation by Schramm and Fowler.     

Quantum scattering in one-dimensional systems satisfying the minimal length uncertainty relation

In quantum gravity theories, when the scattering energy is comparable to the Planck energy the Heisenberg uncertainty principle breaks down and is replaced by the minimal length uncertainty relation. In this paper, the consequences of the minimal length uncertainty relation on one-dimensional quantum scattering are studied using an approach involving a recently proposed second-order differential equation. An exact analytical expression for the tunneling probability through a locally-periodic rectangular potential barrier system is obtained. Results show that the existence of a non-zero minimal length uncertainty tends to shift the resonant tunneling energies to the positive direction. Scattering through a locally-periodic potential composed of double-rectangular potential barriers shows that the first band of resonant tunneling energies widens for minimal length cases when the double-rectangular potential barrier is symmetric but narrows down when the double-rectangular potential barrier is asymmetric. A numerical solution which exploits the use of Wronskians is used to calculate the transmission probabilities through the Pöschl–Teller well, Gaussian barrier, and double-Gaussian barrier. Results show that the probability of passage through the Pöschl–Teller well and Gaussian barrier is smaller in the minimal length cases compared to the non-minimal length case. For the double-Gaussian barrier, the probability of passage for energies that are more positive than the resonant tunneling energy is larger in the minimal length cases compared to the non-minimal length case. The approach is exact and applicable to many types of scattering potential.     

An experimental estimate of the relative aromaticity of the cyclooctatetraene dianion by fusion to dimethyldihydropyrene

The synthesis of the cyclooctatetraene dianion (COT(2-)) fused at the [e]-position of trans-10b,10c-dimethyl-10b,10c-dihydropyrene (DHP) is described, and by comparison of (1)H NMR properties and NICSAv to the analogous benzene fused DHP, the relative aromaticity of the dianion is found to be at least as great as that of benzene, and substantially larger than that of the cyclopentadienide anion.     

Phase behavior, microstructure transition, and antiradical activity of sucrose laurate/propylene glycol/the essential oil of Melaleuca alternifolia/water microemulsions

Nonionic sucrose ester microemulsions composed of sucrose laurate (SL), propylene glycol (PG) and water were prepared with the essential oil of Melaleuca alternifolia, commonly known as tea tree oil (TTO), as oil phase to investigate the phase behavior, microstructure, and antiradical activity. The pseudo-ternary phase diagrams were constructed to elucidate the phase behavior of the microemulsion formations at different weight ratios of surfactant and cosurfactant (S_m = SL/PG) of 1:1, 2:1, and 3:1. The extension of the microemulsion zone was found to be strongly dependent on the S_m ratios. The single phase microemulsion domain, especially o/w microemulsion region increased when S_m ratio is increased from 1:1 to 3:1 and no liquid crystalline structure was observed for all formulations studied. Microstructural aspects were studied by electrical conductivity and pulsed gradient spin echo (PGSE) NMR measurements along water titration line L28 (R_o = 2:8). The results from these combined techniques were in good agreement in regard to the microstructure transition points. The microstructural inversion of w/o to bicontinuous microemulsions occurred at 30 wt.% water while the transition from bicontinuous to o/w structure occurred at 55 wt.% water. The physical stability on storage temperature and time was examined by dynamic light scattering after the centrifuge test and freeze–thaw cycles. The droplet size was kept almost the same without any phase separation, providing less temperature-sensitivity up to 70 °C and good stability for 3 months at room temperature. The chemical profile and radical scavenging activity of TTO in o/w microemulsions was evaluated by means of gas chromatography–mass spectroscopy (GC–MS) and 2,2′-diphenyl-1-picrylhydrazyl free radical (DPPH) scavenging method, respectively. The major abundant constituents of crude TTO, monoterpene alcohols (terpinen-4-ol (41.65%), α-terpineol (3.18%)) and hydrocarbons (γ-terpinene (22.95%), α-terpinene (10.16%)) were identified and the composition percentage of each constituent was calculated form the GC peak areas by normalization method. The DPPH scavenging activity of TTO microemulsion was lower than pure TTO because the SL surfactant may obstruct the interaction between the TTO and DPPH, reducing the number of effective collisions.     

Synthesis of diatropic highly benzannelated annulenes.

The first examples of annelated cis-dihydropyrenes, 16, 18, 19, together with a number of highly annelated trans-dihydropyrenes, 2 - 4 and, 17, are described. All are diatropic and indicate that higher annelation does not remove the delocalisation in a macrocyclic ring.