Relative molecular mass information from aliphatic nitro compounds: A chemical ionization study

The mass spectra of a number of aliphatic nitro compounds have been studied using electron Ionization (EI) and a variety of chemical Ionization (CI) techniques in attempts to obtain relative molecular mass information. The use of positive ion ammonia chemical Ionization techniques gave very satisfactory results, providing abundant [M + NH4]⁺ ions, not only from both primary and secondary nitro compounds, but also from the much more labile tertiary nitro compounds. However, the use of methane and isobutane positive ion CI or EI conditions resulted in facile fragmentation with little relative molecular mass information being made available. Negative ion CI using methane, isobutane or ammonia as moderating gases all gave abundant [M ? 1]^? ions with primary and secondary nitro compounds but at much reduced sensitivity.     

RECOVERY OF Escherichia coli K-12 FROM NEAR-ULTRAVIOLET RADIATION-INDUCED MEMBRANE DAMAGE

Abstract A wild-type Escherichia coli K-12 strain was irradiated with broad-band near-ultraviolet radiation (from Black-Light Blue fluorescent lamps) and after holding at 37°C for various times in a complex recovery medium, was assessed for viability on either complex medium (YENB) or minimal medium containing a high inorganic salt content. A near-ultraviolet radiation fluence was used which reduced the surviving fraction to approximately 10% when assessing for viability on the complex medium plates. A near-ultraviolet radiation induced sensitivity to inorganic salt was observed which was largely recoverable by holding treated cells in a complex recovery medium. The majority of the recovery process occurred in the initial 2 h post-irradiation holding period. No inhibition of the recovery process was produced by adding chloramphenicol (40 μg/m l ) or penicillin G (11 units/m l ) to the recovery medium, indicating that neither protein synthesis nor cell wall synthesis, respectively, were required for recovery. However, by adding bacitracin, an antibiotic which acts in part by inhibiting membrane synthesis, to the recovery medium, an effect on recovery from salt sensitivity was observed. At the concentrations of bacitracin used (0.6 and 0.2 units/m l ), little or no effect was observed on unirradiated cells, but both concentrations decreased the amount of recovery of irradiated cells. These results demonstrate that recovery from near-ultraviolet radiation-induced salt sensitivity occurs, it is independent of cell growth and the effect of bacitracin suggests that membrane synthesis may be required for recovery.     

Can mono- or di-butyltin chlorides produce tributyltin chloride at elevated temperatures? Implications for applications in chemical vapour deposition

The thermolysis of the butyltin chlorides at 200-300 °C in the liquid phase has been investigated by ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopy. The stabilities follow the order: Bu₂SnCl₂ > Bu₃SnCl > BuSnCl₃. Only tributyltin chloride showed any evidence of redistribution, giving dibutyltin dichloride, together with metallic tin, butane, and but-1-ene, which would be formed by decomposition of tetrabutyltin. Dibutyltin dichloride decomposed to give mainly butane with no other apparent liquid organotin compound. Butyltin trichloride gave butane, some butene, and metallic tin, and showed no evidence of forming tributyltin chloride by the redistribution reaction, which would have environmental implications for its use in the CVD coating of glass.     

A Sequence-specific Alkali-labile Photolesion Mapping to Adenine in Single-stranded DNA

Abstract— Following UV irradiation at 254 nm and treatment with hot piperidine, single-stranded 49-mer and 12-mer oligodeoxyribonucleotides have been shown by gel-sequencing experiments to contain a prominent alkali-labile cleavage site that maps to adenine in the sequence element 5'-TTGATC-3'. This behavior is abolished by single base substitutions within the photoreactive tract and does not occur with duplex DNA. The distinctive properties of the photolesion are consistent with the formation of an abasic site through initial loss of a photomodified adenine base of unknown structure. The presence of an abasic site is supported by the observations that the alkaline cleavage fragments are terminally phosphorylated and that strand scission can also be effected by spermidine and the tripeptide Lys-Trp-Lys.     

Asymmetric synthesis of (1R,2S,3R)-gamma-methyl-cis-pentacin by a kinetic resolution protocol

The asymmetric synthesis of (1R,2S,3R)-3-methyl-2-amino-cyclopentane carboxylic acid has been achieved via kinetic resolution of racemic tert-butyl 3-methyl-cyclopentene-1-carboxylate with homochiral lithium (S)-N-benzyl-N-alpha-methylbenzylamide.     

Reactions of a carbene stabilised indium trihydride complex, [InH3{CN(Mes)C2H2N(Mes)}] Mes = mesityl,with transition metal complexes

The reactivity of the carbene stabilised indium trihydride complex, [InH₃(IMes)] IMes = 1,3-dimesitylimidazol-2-ylidene, toward a variety of transition metal complexes has been investigated. The study has shown that the InH₃ complex can act as a carbene and/or hydride transfer reagent to transition metal centres but does not yield heterobimetallic materials. Two new complexes, [Cp₂Ti(-Cl)₂Zn(IMes)Cl] and [CpNi(H)(IMes)], have resulted from this work, both of which have been spectroscopically and structurally characterised.