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61.
The preparation of a series of non-cyclic, uncharged ligands able to selectively complex alkali and alkaline earth metal cations is described. These molecules are designed to be used as carriers for cations through membranes. Some of the compounds show high Ca2+ and Na+ selectivity, respectively, in liquid membrane electrodes.  相似文献   
62.
An initial photophysical study of a tetra-solketal-substituted zinc phthalocyanine is reported; at low temperature this compound exhibits very strong aggregation, and a new red shifted emission peak is observed, lambda max approximately 750 nm, attributed to a fluorescent phthalocyanine dimer.  相似文献   
63.
Strategies are reported that combine in one step a predictable chemical-based protein digestion with mass spectrometry. Lysine residue amino groups in peptides and proteins are modified by reaction with a peroxycarbonate derived from p-nitrophenol, and tert-butyl hydroperoxide. The peroxycarbonate reacts with lysine residues in peptides and proteins, and the resulting lysine peroxycarbamates undergo homolytic fragmentation under conditions of low-energy collision-induced dissociation (CID). Observed fragmentation of the peptides involves apparent free radical processes including Hofmann-L?ffler-type rearrangements that lead to peptide chain fragmentation. Strategies for directed cleavage of peptides by free radical promoted processes are feasible, and such strategies may well simplify schemes for protein analysis.  相似文献   
64.
In the actinides bothi 13/2 protons andj 15/2 neutrons are close to the Fermi surface. At rapid rotation these high-j particles will unpair and align their orbital angular momentum along the axis of rotation giving rise tos-bands that cross the ground-state band. Coulomb excitation of the odd nuclei 237 93 Np (established up to the 45/2+ state) and 235 92 U (established up to the 51/2? state) provides specific information about these band crossings: From the saturating alignment of the odd high-j particle in both nuclei at intermediate rotational frequencies we find the aligned angular momentum of thei 13/2 protons-band to be 6.6? while the corresponding value for thej 15/2 neutrons-band is 5.5?. At more rapid rotation above ?ω=0.18 MeV we observe additional alignment in235U. This is ascribed to the interaction of the protons-band. From the gradual onset of the additional alignment we deduce that forZ=92 the protons-band interacts strongly with the ground-state band and from a comparison of the actual amount of alignment with the full value of 6.6? we estimate the crossing to occur around ?gw c p =0.25 MeV.  相似文献   
65.
A new ferrocenyl-N-heterocyclic carbene ligand precursor 1,1′-bis[(1-tert-butylimidazolium)-3-methyl]ferrocene dichloride has been synthesised and structurally characterised. The imidazolium salt was readily deprotonated in situ with KN(SiMe3)2 and reacted with [PdCl2 (cod)] to afford the structurally characterised palladium (II) complex trans-[PdCl2(CfcC)], where (cod) = 1,5-cyclooctadiene and (CfcC) = 1,1′-di-tert-butyl-3,3′-(1,1′-dimethyleneferrocenyl)-diimidazol-2-ylidene.  相似文献   
66.
The π-allyltricarbonyliron lactone complex (7), formed by reaction of E-1,2-epoxy-2-methyl-6,6-dimethoxyhex-3-ene(5) with co-ordinatively unsaturated iron carbonyl species, was reacted with benzylamine to give a lactam complex (8) by an SN'-like mechanism. This complex upon oxidation with Ce(IV) afforded cis-3-isopropenyl-4-[(2',2'-dim (9) which was chemically modified into trans-3-(1'-hydroxyethyl)-4-[(2',2-dimethoxy)ethyl] azetidin-2-one (13), a key intermediate previously used in the synthesis of the antibiotic thienamycin. Similar reaction with (S)-(-)--methylbenzylamine afforded a separable mixture of diastereoisomeric iron lactam complexes (16 and 17). These complexes could be individually converted to the corresponding optically active β-lactam derivatives (27 and 28) and, hence, are precursors for the synthesis of either natural (+)-thienamycin or unnatural (-)-thienamycin.  相似文献   
67.
Contact angle measurements with a large number of liquids on the semi-fluorinated acryl polymer EGC-1700 films are reported. The surface tension was determined to be gammasv=13.84 mJ/m2 from contact angles of octamethylcyclotetrasiloxane (OMCTS) and decamethylcyclopentasiloxane (DMCPS). Inertness of these two liquids makes them ideal for determination of surface tension of low-energy fluoropolymers. On the other hand, contact angles of many other liquids deviated somewhat from a smooth contact angle pattern that represents the EGC-1700 surface tension. It is argued that noninertness of the molecules of these liquids gives rise to specific interactions with the polymer film, causing the deviations. Furthermore, contact angles of a series of n-alkanes (n-hexane to n-hexadecane) showed systematic deviations from this curve, similar to the trend observed for n-alkanes/Teflon AF 1600 systems studied earlier. Adsorption of vapor of short-chain liquids onto the polymer film caused their contact angles to fall above the gammasv=13.84 mJ/m2 curve, and a parallel alignment of molecules of the long-chain n-alkanes in the vicinity of the solid was the explanation for the deviation of their contact angles below it. It is found that vapor adsorption effect is more significant in the case of Teflon AF 1600, while the alignment of liquid molecules close to the surface is more pronounced for EGC-1700.  相似文献   
68.
The glass transition of an irradiated, ultra-high molecular weight, linear polyethylene was investigated by means of the Perkin-Elmer DSC-2 differential scanning calorimeter. The experimental specific heat data were compared with those of the nonirradiated sample, obtained by DSC and adiabatic calorimetry.  相似文献   
69.
The title compound, Fc2(Ph)PS · I2, has been prepared and characterised in both the solid state and solution. Single crystal X-ray crystallography reveals that the adduct adopts a molecular charge-transfer structure in the solid state. Mössbauer spectroscopy confirms the presence of low spin Fe2+ but also indicates the presence of ca. 24% of an Fe3+ species. The electrochemistry of Fc2(Ph)PS · I2, Fc2(Ph)PS and Fc2(Ph)P has been studied using a combination of cyclic voltammetry and differential pulse voltammetry. The data for Fc2(Ph)PS · I2 show two redox processes, consistent with the sequential oxidation of the ferrocenyl groups to ferrocenium species.  相似文献   
70.
The hydroxylase component (MMOH) of soluble methane monooxygenase from Methylococcus capsulatus (Bath) was reduced to the diiron(II) form and then allowed to react with dioxygen to generate the diiron(IV) intermediate Q in the first phase of a double-mixing stopped-flow experiment. CD3NO2 was then introduced in the second phase of the experiment, which was carried out in D2O at 25 degrees C. The kinetics of the reaction of the substrate with Q were monitored by stopped-flow Fourier transform infrared spectroscopy, observing the disappearance of the asymmetric NO2 bending vibration at 1548 cm-1. The data were fit to a single-exponential function, which yielded a kobs of 0.45 +/- 0.07 s-1. This result is in quantitative agreement with a kobs of 0.39 +/- 0.01 s-1 obtained by observing the disappearance of Q by double-mixing stopped-flow optical spectroscopy at its absorption maximum of 420 nm. These results provide for the first time direct monitoring of the hydroxylation of a methane-derived substrate in the MMOH reaction pathway and demonstrate that Q decay occurs concomitantly with substrate consumption.  相似文献   
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