Photosensitized formation of RNA-protein crosslinks in an insect egg (Smittia spec., Chironomidae, Diptera)

Abstract—Upon irradiation of Smittia eggs with ultraviolet light (UV), the extractability of RNA with phenol decreased. The strongest decrease was observed after irradiation at 295 nm wavelength. After trypsin treatment, RNA could be recovered to the same degree as from unirradiated eggs. The extractability of RNA from irradiated eggs was not enhanced by formamide. dimethyl sulfoxide. high salt concentration or heat treatment. The results suggest that the UV-mediated formation of RNA-protein crosslinks in Smittia eggs involves the action of a photosensitizer.     

High-resolution spectra of the 1(1,1) ← 0(0,0) rotational transition of water in argon and krypton matrices

The high-resolution spectra of H₂¹⁶O, H₂¹⁸O, HD¹⁶O, HD¹⁸O, D₂¹⁶O, and D₂¹⁸O isolated in argon and krypton matrices are reported in the 10–60 cm^?1 region. The high resolution is obtained by observing very dilute mixtures of water in the rare gases. No discrete absorbances attributable to pure argon or krypton are found in this region. In all cases the relative gas—matrix shifts of the isotopimers are consistent with the rotation—translation coupling model. The linewidths are found to correlate with rotation—translation coupling. The integrated intensity of the 1(1,1) — 0(0,0) transition of HDO exhibits a temperature dependence which does not deviate significantly from that expected from a Boltzmann distribution in rigid rotor energy levels.     

Synthesis of the Glycopeptide Partial Sequence A80–A84 of Human Fibroblast Interferon

The glycopentapeptide H-(GlcNAcβ1-)Asn-Glu-Thr-Ile-Val-OH ( 10 ) representing the partial sequence A⁸⁰–A⁸⁴ of human fibroblast interferon was synthesized using the newly developed allyl-ester protection of carboxy functions. The allyl esters, which are stable to acids and to bases, can be cleaved under very mild, neutral conditions using tris(triphenylphosphine)rhodium(I) chloride or tetrakis(triphenylphosphine)palladium(0) as a catalyst. This synthetic method opens up a preparative route to glycopeptide model structures of glycoproteins of high biological interest.     

Effect of instrument tuning on the detectabilityof biopolymers in electrospray ionization mass spectrometry

Electrospray ionization mass spectrometry of multiply charged biopolymer ions of different molecular size revealed a strong influence of tuning parameters on their detectability in quadrupole ion trap and triple quadrupole mass spectrometers. Hence, after optimizing the ion optical parameters with the signal of the 4- charge state of (dT)(24) (low charge state tuning), a tenfold increase in the signal-to-noise ratio for a mixture of oligodeoxythymidylic acids (n = 12-18) was obtained compared with the results achieved with tune parameters optimized with a synthetic 80-mer oligodeoxynucleotide. By contrast, a detection limit in the upper femtomole region could only be reached for a 104-mer oligodeoxynucleotide utilizing the 24- charge state of the 80-mer (high charge state tuning). The same effect was observed for proteins investigated in the positive ion mode using low and high charge states of cytochrome c and carbonic anhydrase, respectively, for instrument tuning. By comparing the settings for low and high charge state tuning, it became obvious that the most significant difference was observed in the potential applied to the heated metal capillary used to transfer ions from the atmospheric pressure to the vacuum region of the ion source. Taking advantage of the optimized tuning procedure, the molecular mass of a 61 base pair product of polymerase chain reaction was accurately determined by electrospray ionization mass spectrometry on-line interfaced to ion-pair reversed-phase high-performance liquid chromatography.     

Landfill Gas: From Rubbish to Resource

The prospects of using landfill gas (LFG) as a high-grade fuel in the immediate future, in view of environmental regulations, the Kyoto Protocols, and energy prices, are discussed. Adsorption cycles suggested in the late 1980s by Sircar and co-workers for treating LFG are reviewed: one produced CO₂-free methane and the other produced both CO₂-free methane and methane-free CO₂. Neither of those could be used to produce pipeline quality gas from LFG, due to contaminants such as nitrogen. Two new three-stage flowsheets are discussed as a means to separate pipeline-grade methane from LFG. One is a hybrid membrane—PSA system. The other is a TSA—PSA system. The third stage of both of these systems is crucial to obtaining pipeline quality gas, i.e., a PSA unit to extract the nitrogen and other light gases from methane. A novel PSA cycle is suggested and explained in terms of: a model by which the recovery, power requirements, and adsorbent bed size can be estimated.     

Tieftemperatur 13C-NMR.-Spektren von 13C-und 6Li-markierten Chlor-, Brom- und Jod-Lithium-Carbenoiden. Vorläufige Mitteilung

Low Temperature ¹³C-NMR. Spectra of ¹³C- and ⁶Li-Labelled Chloro-, Bromo-, and Iodo-lithiumcarbenoids The ¹³C-NMR. spectra of tetrahydrofuran solutions of 16 chloro-, bromo-, and iodo-⁶lithio- and -⁷lithio-carbenoids with ¹³C-labelled methane, ethane, ethylene, and cyclopropane C-skeletons have been measured at temperatures around ? 100° (for examples see Fig. 1 and 2). Invariably, the exchange of hydrogen or halogen by lithium causes deshielding (Δδ, see Table 1) of the ¹³C-signal by up to 289 and 434 ppm, respectively, and decrease of ¹J (¹H, ¹³C) and ¹J(¹³C,¹³C) couplings (see Table 2) with the C-atom of up to 104 and 30 Hz, respectively. The ¹J(⁶Li, ¹³C) and ¹J(⁷Li, ¹³C) coupling of ca. 17 and 45 Hz, respectively, obtained in ten cases (Table 1) is independant of the substitution pattern of the C-skeleton and of the particular halogen atom.     

Zum massenspektroskopischen Fragmentierungsverhalten von Arylalkylphosphonaten

Zusammenfassung Der Einfluß verschiedener Substituenten auf das Fragmentierungsverhalten von Arylalkylphosphonaten wird diskutiert. Während einige der beobachteten Zerfallsreaktionen analog zu den bei Carbonsäureestern gefundenen verlaufen (z. B.McLafferty-Umlagerung, doppelte Wasserstoffumlagerung bei Estern mit höheren Alkoholen), treten zusätzliche Umlagerungen auf, die für Ester der phosphorigen und der Phosphorsäure typisch zu sein scheinen (z. B. Eliminierung der Phosphor- und Sauerstoffatome unter Rekombination von Kohlenstoffresten).

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The influence of various substituents on the fragmentation behavior of aryl alkyl phosphonates is discussed. Several fragmentation reactions occur as observed with carbonic acid esters (e. g.,McLafferty rearrangement and double hydrogen transfer with esters of higher alcohols). In addition, rearrangements may take place which seem to be typical for esters of the phosphorous and phosphoric acid (e. g., expulsion of the phosphorus and oxygen atoms accompanied by recombination of carbon residues). *** DIRECT SUPPORT *** A3615112 00008

     

Investigation of the formation and properties of protective oxide layers on high purity chromium with SIMS imaging techniques

Spallation of the protective oxide layer formed during hot gas oxidation is the main reason for the corrosion of high purity powder metallurgically produced chromium[1]. To explain the formation and occasional spallation of the oxide layer a chromium sample subjected to two consecutive oxidation processes in¹⁶O and¹⁸O atmosphere at high temperature was characterised by 2D and 3D SIMS.The formation of the protective oxide can be described by the diffusion of chromium from the bulk to the surface and the reaction of the chromium atoms with the oxygen from the gaseous phase. The very low solubility of nitrogen in chromium oxide indicates its inability to diffuse through the growing oxide layer and explains the enrichment of nitrogen (same mechanism applies for chlorine) in the interface metal/oxide. The accumulation of trace elements within the interface during the oxidation process explains the reduced adhesion power of the passivation layer and its spallation.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

SIMS Investigations on the Distribution of Trace Elements in Modified Aluminium–Silicon–Magnesium Alloys

 Strontium modified aluminium–silicon cast alloys are well known for their outstanding mechanical properties as they combine excellent strength with good ductility that is due to a modification of brittle Si in the eutectic with traces of Sr (0.3–0.5 wt%). Although the level of Sr addition is very low, formation of ternary AlSiSr phases with deleterious effects on the ductility can take place. Consequently, there is a certain need of alternative modifying elements. Following the theory of Lu and Hellawell which predicts an optimal atomic size for good modification, Eu, which has an atomic radius close to that optimal size, was additionally used as a modifying element. This study presents SIMS (secondary ion mass spectrometer) investigations of the 3D-distributions of the main alloying and trace elements in Al–Si feedstock alloys for thixocasting modified with Sr and Eu, respectively. Received October 1, 2001; accepted May 21, 2002