C-terminal processing of yeast Spt7 occurs in the absence of functional SAGA complex

Background  

Spt7 is an integral component of the multi-subunit SAGA complex that is required for the expression of ~10% of yeast genes. Two forms of Spt7 have been identified, the second of which is truncated at its C-terminus and found in the SAGA-like (SLIK) complex.     

The Banach–Mazur Distance to the Cube in Low Dimensions

We show that the Banach–Mazur distance from any centrally symmetric convex body in ? ⁿ to the n-dimensional cube is at most

$\sqrt{n^2-2n+2+\frac{2}{\sqrt{n+2}-1}},$

which improves previously known estimates for “small” n≥3. (For large n, asymptotically better bounds are known; in the asymmetric case, exact bounds are known.) The proof of our estimate uses an idea of Lassak and the existence of two nearly orthogonal contact points in John’s decomposition of the identity. Our estimate on such contact points is closely connected to a well-known estimate of Gerzon on equiangular systems of lines.

     

Evaluation of femtosecond LIBS for spectrochemical microanalysis of aluminium alloys

The analytical performance of femtosecond laser-induced breakdown spectroscopy (LIBS) for elemental microanalysis of aluminium alloys and for mapping precipitate distribution on the sample surface has been studied in detail. A Ti–sapphire laser system producing pulses of 130 fs at 800 nm was used to generate the laser-induced plasma. Multi-element microanalysis of commercially available aluminium alloys was performed in air at atmospheric pressure. Crater characteristics such as diameter and crater morphology were characterized by optical and scanning-electron microscopy. Scaling of plasma emission and limit of detection as a function of laser pulse energy was also investigated. Current experimental results are presented and are compared with previous nanosecond microLIBS measurements.     

Inkjet application, chromatography, and mass spectrometry of sugars on nanostructured thin films

Ultrathin-layer chromatography (UTLC) potentially offers faster analysis, reduced solvent and sample volumes, and lower costs. One novel technique for producing UTLC plates has been glancing angle deposition (GLAD), a physical vapor deposition technique capable of aligning macropores to produce interesting separation properties. To date, however, GLAD-UTLC plates have been restricted to model dye systems, rather than realistic analytes. This study demonstrates the transfer of high-performance thin-layer chromatography (HPTLC) sugar analysis methods to GLAD-UTLC plates using the office chromatography framework. A consumer inkjet printer was used to apply very sharp low volume (3–30 nL) bands of water-soluble analytes (lactose, sucrose, and fructose). Analytic performance measurements extrapolated the limits of detection to be 3–5 ng/zone, which was experimentally proven down to 60–70 ng/band, depending on the sugar. This qualitative analysis of sugars in a commercially available chocolate sample is the first reported application of GLAD-UTLC to food samples. The potential utility of GLAD-UTLC is further exemplified by successful coupling with electrospray ionization mass spectrometry for the first time to characterize underivatized sugars.

Morphological modification of nanostructured ultrathin-layer chromatography stationary phases

Ultrathin-layer chromatography (UTLC) provides the high sensitivities and rapid separations over short distances desirable in many analytical applications. The dependence of these performance benefits on UTLC layer microstructure motivates continued stationary phase engineering efforts. A new method of modifying the elution behaviours of nanostructured thin film UTLC stationary phases is investigated in this report. Macroporous normal phase silica thin films ～5 μm thick were fabricated using glancing angle deposition (GLAD). Reactive ion etching (RIE) and a subsequent annealing treatment modified stationary phase morphology to tune migration velocity, analyte retention, and overall separation performance. Combining this technique with a RIE shadow mask enabled fabrication of adjacent concentration and separation zones with markedly different elution properties. Although produced using an entirely new approach, GLAD UTLC concentration zone media behaved in a manner consistent with traditional thin-layer chromatography (TLC) and high-performance TLC (HPTLC) concentration zone plates. In particular, these new media focused large volume, low concentration dye mixture spots into narrow bands to achieve high-quality separations. The described approach to modifying the morphology and resultant elution behaviours of nanostructured stationary phases expands the capabilities of the GLAD UTLC technique.     

Analyte migration in anisotropic nanostructured ultrathin-layer chromatography media

We investigate the performance of highly anisotropic nanostructured thin film ultrathin-layer chromatography (UTLC) media with porosity and architecture engineered using the glancing-angle deposition (GLAD) process. Our anisotropic structures resemble nanoblades, producing channel-like features that partially decouple analyte migration from development direction, offering new separation behaviours. Here we study GLAD-UTLC plate performance in terms of migration distance, plate number, retention factor and a figure of merit specific to GLAD-UTLC, track deviation angle. Migration distances increase with porosity by a factor of two for all feature orientations (up to a maximum of 22 mm) over the range of porosities considered in this study. Plate numbers approaching 1100 are observed for GLAD-UTLC plates when the nanoblade features are aligned with the development direction. We present a theoretical model describing mobile phase flow in anisotropic GLAD-UTLC media, and find good agreement with experimental results. Our plates provide channel features that reduce transverse spot broadening while providing the wide pores required for rapid migration and high separation performance. These improvements may enable a greater number of parallel separations on miniaturized GLAD-UTLC plate formats. Their small sizes should also make them compatible with the Office Chromatography concept in which office peripherals (inkjet printers and flatbed scanners) replace conventional TLC instruments. Equipped with a better understanding of the unique GLAD-UTLC elution behaviours, we expect to further improve performance in the future.     

Determination of lead in water using laser ablation–laser induced fluorescence

The detection sensitivity of laser-induced breakdown spectroscopy (LIBS) is improved by coupling it with a laser-induced fluorescence method. A waterjet sample containing 500 ppm of Pb as an analyte was ablated by a 266 nm, frequency-quadrupled Q-switchedNd:YAG laser at an energy of ~ 260 μJ. After a short delay the resulting plume was re-excited with a 283.306 nm, nanosecond pulse dye laser at energies ranging from 45 to 100 nJ. The limit of detection (LOD) of lead in water was determined both by the single-pulse LIBS technique and Laser Ablation coupled with Laser-Induced Fluorecence (LA–LIF) method. It was found to be 75 ppm in the case of single-pulse LIBS and 4.3 ppm for LA–LIF. When the resonant pulse was detuned from the transition wavelength the LA–LIF signal disappeared demonstrating the resonant selectivity of this technique.