Rearrangements of haloalkynol derivatives of glucofuranose

Bromoalkynol derivatives of diacetone glucose undergo rearrangements to dihaloenol ethers contained in furo[3,4-b]furan cores when treated with halonium-producing reagents. [reaction: see text]     

Ultrasonic determination of the temperature dependence of the electron mean free path in cesium single crystal

The ultrasonic attenuation of high frequency longitudinal waves has been measured in transverse and oblique magnetic fields to determine the temperature dependence of the phonon-limited mean free path in cesium single crystals. Below 2.5°K, the mean free path varies as T^4.8. The results are compared with electrical resistivity measurements in cesium.     

Use of two-dimensional liquid fractionation for separation of proteins from cell lysates without the presence of methionine oxidation

A novel two-dimensional (2D) chromatographic method is developed to separate proteins from malignant breast cancer whole cell lysates. Protein mixtures are first separated according to their pIby chromatofocusing followed by an orthogonal non-porous reversed-phase separation. An important advantage of this 2D chromatographic method is that, unlike gel-based methods, it does not result in methionine oxidation. The lack of methionine oxidation during separation is demonstrated by the analysis of protein tryptic digests using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) MS. Our novel 2D chromatographic method used in combination with on-target light-induced methionine oxidation provides a means for studying methionine-containing peptides. Methionine residues in peptide sequences are partially oxidized with light exposure. Neither the location nor the modification of methionine in the peptide sequence affects the oxidation. As a result, multiple peaks are observed in MALDI-TOF-MS spectra after light exposure. Sequence information derived from light-induced methionine can be applied to enhance the database search results obtained through peptide mass fingerprinting.     

Discrimination and identification of vowels by young, hearing-impaired adults

This study examined the effects of mild-to-moderate sensorineural hearing loss on vowel perception abilities of young, hearing-impaired (YHI) adults. Stimuli were presented at a low conversational level with a flat frequency response (approximately 60 dB SPL), and in two gain conditions: (a) high level gain with a flat frequency response (95 dB SPL), and (b) frequency-specific gain shaped according to each listener's hearing loss (designed to simulate the frequency response provided by a linear hearing aid to an input signal of 60 dB SPL). Listeners discriminated changes in the vowels /I e E inverted-v ae/ when F1 or F2 varied, and later categorized the vowels. YHI listeners performed better in the two gain conditions than in the conversational level condition. Performances in the two gain conditions were similar, suggesting that upward spread of masking was not seen at these signal levels for these tasks. Results were compared with those from a group of elderly, hearing-impaired (EHI) listeners, reported in Coughlin, Kewley-Port, and Humes [J. Acoust. Soc. Am. 104, 3597-3607 (1998)]. Comparisons revealed no significant differences between the EHI and YHI groups, suggesting that hearing impairment, not age, is the primary contributor to decreased vowel perception in these listeners.     

Allyl transfer to aldehydes and ketones by Brønsted acid activation of allyl and crotyl 1,3,2-dioxazaborolidines

Alkyl dioxazaborolidines are air-stable and often crystalline organoboranes. A variety of Br?nsted acids activate allyl dioxazaborolidines to generate reactive allyl-transfer reagents in situ. These reagents add to aldehydes and ketones to generate the corresponding alcohols in good yields under mild conditions. The E- and Z-crotyl reagents react diastereoselectively with aldehydes and ketones to produce anti and syn adducts, respectively, a result consistent with a cyclic transition state (type I mechanism).     

Glycoproteomic characterization of carriers of the CD15/Lewis<Superscript>x</Superscript> epitope on Hodgkin's Reed-Sternberg cells

Background  

The Lewis^x trisaccharide, also referred to as the CD15 antigen, is a diagnostic marker used to distinguish Hodgkin's lymphoma from other lymphocytic cancers. However, the role of such fucosylated structures remains poorly understood, in part because carriers of Lewis^x structures on Hodgkin's Reed-Sternberg cells have not been identified.     

Surface reactions and the effects of oxygen on Pb atomization in graphite furnace atomic absorption spectrometry

Summary Previous papers have shown a pronounced shift in appearance temperatures of Pb as a result of O₂ in the system. This paper briefly summarizes the surface chemistry occurring on graphite as a result of exposure to O₂. Chemisorbed oxygen and an altered surface are suggested as the cause for the pulse shift of the Pb absorbance signal. A significant shift with an oxygenated surface but no gas phase O₂ present supports this conclusion. Time and spatially resolved absorbance traces suggest multiple release processes and readsorption of Pb on the surface. Pb/O₂ gas phase reactions do not appear to significantly alter the atomization efficiency and cannot explain the observed shifts. Similarly, O₂/Pb _x O _y(s) reactions cannot account for the first shot back and may play only a secondary role in the presence of O₂ in the gas phase. It was also observed that a significant (> 30%) amount of Pb remained on the surface after the solution was deposited and withdrawn 10 s later. This is attributed to binding of Pb to surface functionalities before the sample is desolvated.

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Oberflächenreaktionen und Wirkungen von Sauerstoff auf die Blei-Atomisierung in der Graphitofen-AAS

Zusammenfassung Vorangegangene Untersuchungen haben eine deutliche Verschiebung der Erscheinungstemperatur von Blei unter dem Einfluß von Sauerstoff im System gezeigt. In dieser Arbeit werden die Oberflächenreaktionen am Graphit unter Sauerstoffeinwirkung zusammenfassend diskutiert. Als Ursachen für die Pulsverschiebung des Bleisignals wurden der chemisorbierte Sauerstoff sowie Veränderungen der Oberfläche gefunden. Eine signifikante Verschiebung bei oxygenierter Oberfläche aber ohne gasförmigen Sauerstoff unterstützt diesen Schluß. Zeitlich und räumlich aufgelöste Absorptionsspuren deuten auf multiple Freisetzungsprozesse und Re-adsorption von Blei an der Oberfläche. Pb/O₂-Reaktionen in der Gasphase scheinen die Atomisierungswirkung nicht signifikant zu beeinflussen und können die beobachteten Verschiebungen nicht erklären. Ebenso können auch die O₂/Pb _x O _y(s)-Reaktionen nicht den first shot back erklären und spielen vielleicht nur eine sekundäre Rolle in Gegenwart von O₂ in der Gasphase. Es wurde ebenfalls beobachtet, daß ein beträchtlicher Anteil des Bleis (> 30%) an der Oberfläche zurückblieb, wenn die Lösung eingebracht und nach 10 s wieder entfernt wurde. Dies wird der Bindung von Blei an Oberflächenfunktionen vor der Desolvatation der Probe zugeschrieben.

     

Chemically stable films for combinatorial fluorosensor arrays

Sensor arrays are useful for many purposes. Our interests include quasi-distributed intrinsic fiber optic arrays, those distributed along the length of an optical fiber. We have demonstrated an optical time-of-flight approach to distinguishing the fluorescence output of such arrays, as well as a synthesis of combinatorial libraries that takes advantage of a support of linear morphology to make numerous compounds in a simple manner without information loss in the synthesis. To unite these research areas, we needed an optical fiber cladding material that meets demanding synthetic and optical requirements. We have chosen the Meldal SPOCC polymer support as the best candidate for such a material and report here our initial results with this material.     

Amphiphilic pentablock copolymers and their blends with PDMS for antibiofouling coatings

Well‐defined amphiphilic pentablock copolymers Siy‐(EGx‐FAz)₂ composed of polysiloxane (Si), polyethylene glycol (EG), and perfluorohexylethyl polyacrylate (FA) blocks are synthesized by ATRP of FA monomer starting from a difunctional bromo‐terminated macroinitiator. Diblock copolymers EGx‐FAz are also synthesized as model systems. The block copolymers are used, either alone or blended with a PDMS matrix in varied loadings, to prepare antibiofouling coatings. Angle‐resolved XPS and contact angle measurements show that the coating surface is highly enriched in fluorine content but undergoes reconstruction after contact with water. Protein adsorption experiments with human serum albumin and calf serum highlight that diblock copolymers resist protein adhesion better than do pentablock copolymers. Blending of the pentablock copolymer with PDMS results in increased protein adsorption. By contrast, the PDMS‐matrix coatings show high removal percentages of sporelings of the green fouling alga Ulva linza. © 2015 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 2015 , 53, 1213–1225