Observation of exclusive B --> D(*)K(*-) decays

We report the first observation of the exclusive decays B-->D((*))K(*-), using 9.66 x 10(6) BB pairs collected at the Upsilon(4S) with the CLEO detector. We measure the following branching fractions: B(B--->D(0)K(*-)) = (6.1+/-1.6+/-1.7)x10(-4), B(B(0)-->D(+)K(*-)) = (3.7+/-1.5+/-1.0)x10(-4), B(B(0)-->D(*+)K(*-)) = (3.8+/-1.3+/-0.8)x10(-4), and B(B--->D(*0)K(*-)) = (7.7+/-2.2+/-2.6)x10(-4). The B-->D(*)K(*-) branching ratios are the averages of those corresponding to the 00 and 11 helicity states. The errors shown are statistical and systematic, respectively.     

Observation of B --> phiK and B --> phiK*

We have studied two-body charmless hadronic decays of B mesons into the final states straight phiK and phiK(*). Using 9.7 million B&Bmacr; pairs collected with the CLEO II detector, we observe the decays B- --> phiK- and B0--> phiK(*0) with the following branching fractions: B(B--->phiK-) = (5.5(+2.1)(-1.8)+/-0.6)x10(-6) and B(B0--> phiK(*0)) = (11.5(+4.5+1.8)(-3.7-1.7))x10(-6). We also see evidence for the decays B0-->phiK0 and B---> phiK(*-). However, since the statistical significance is not overwhelming for these modes, we determine upper limits of <12.3x10(-6) and <22.5x10(-6) ( 90% confidence level), respectively.     

Identification and reduction of ion suppression effects on pharmacokinetic parameters by polyethylene glycol 400

Ion suppression in mass spectrometry has been described recently in detail and should always be considered during analysis by liquid chromatography/tandem mass spectrometry (LC/MS/MS) in a drug metabolism and pharmacokinetics (DMPK) environment. At best, ion suppression leads to decreased sensitivity but at worst could lead to incorrectly determined pharmacokinetic (PK) parameters. Our investigations centred on polyethylene glycol (PEG 400), an excipient often used in pre-clinical dosing vehicles. PEG was also found to be present in large quantities in the blood collection tubes used for pre-clinical PK studies. Ion suppression was observed for many analytes, either due to the use of PEG in the dosing vehicle or in blood collection tubes. The elimination of large ion suppression effects was attained by simple chromatographic gradient changes and the use of alternative blood collection tubes. The effect of the above was to increase the detected plasma concentration levels, which resulted in a change in key PK parameters.     

Substoichiometric neutron-activation determination of gallium: extraction from HCl with tri-n-octylphosphine oxide in cyclohexane

A highly precise method for the determination of traces of gallium by neutron activation is described. Conditions for the extraction of gallium are reported and general requirements for substoichiometric isolation of cations from HCl with neutral donors are discussed. The mean of determinations of gallium at concentrations of 40 ng ml in a solution prepared by dissolving a standard reference aluminium alloy was 213.9 +/- 1.3 ng. The relative standard deviation and the total error of the method (based on the SRM value) were 0.7 and 10.5% respectively.     

Low-temperature single-crystal Raman and neutron-diffraction study of the hydrogenous ammonium copper(II) Tutton salt and the deuterated analogue in the metastable state

Low-temperature (15 K) single-crystal neutron-diffraction structures and Raman spectra of the salts (NX4)2[Cu(OX2)6](SO4)2, where X=H or D, are reported. This study is concerned with the origin of the structural phase change that is known to occur upon deuteration. Data for the deuterated salt were measured in the metastable state, achieved by application of 500 bar of hydrostatic pressure at approximately 303 K followed by cooling to 281 K and the subsequent release of pressure. This allows for the direct comparison between the hydrogenous and deuterated salts, in the same modification, at ambient pressure and low temperature. The Raman spectra provide no intimation of any significant change in the intermolecular bonding. Furthermore, structural differences are few, the largest being for the long Cu-O bond, which is 2.2834(5) and 2.2802(4) A for the hydrogenous and the deuterated salts, respectively. Calorimetric data for the deuterated salt are also presented, providing an estimate of 0.17(2) kJ/mol for the enthalpy difference between the two structural forms at 295.8(5) K. The structural data suggest that substitution of hydrogen for deuterium gives rise to changes in the hydrogen-bonding interactions that result in a slightly reduced force field about the copper(II) center. The small structural differences suggest different relative stabilities for the hydrogenous and deuterated salts, which may be sufficient to stabilize the hydrogenous salt in the anomalous structural form.     

Measurement of the decay constant f(Ds+) using D(s+)-->l+ nu

We measure the decay constant f(Ds+) using the D(s+)-->l+ nu channel, where the l+ designates either a mu+ or a tau+, when the tau+ -->pi+ nu. Using both measurements we find f(Ds+)=274+/-13+/-7 MeV. Combining with our previous determination of f(D+), we compute the ratio f(Ds+)/f(D+)=1.23+/-0.11+/-0.04. We compare with theoretical estimates.     

A refined He-LiF(001) potential from selective adsorption resonances measured with high-resolution helium spin-echo spectroscopy

The authors have developed a new experimental approach for measuring gas-surface selective adsorption resonances with much higher energy resolution and over a wider range of kinematic conditions than has previously been possible. The technique involves using a 3He spin-echo spectrometer as a Fourier transform helium atom scattering apparatus. The authors applied the technique to the He-LiF(001) system. They developed a new empirical potential for the He-LiF(001) system by analyzing and refining the best existing potentials in the light of the new data set. Following an initial free-particle model analysis, the authors used exact close coupling scattering calculations to compare the existing potentials with the new experimental data set. Systematic differences are observed between the two. The existing potentials are modified by simple transformations to give a refined potential that is consistent with and fully reproduces the experimental data. Their technique represents a new approach for developing very high precision empirical potentials in order to test first principles theory.     

Application of design-of-experiments procedures to optimize efficiently pretreatment of lipase for use in a nonaqueous reaction

A variety of different pretreatments can improve the performance of enzymes in nonpolar reaction media. These pretreatments have primarily been studied in isolation; however, interactions between some pairs of pretreatments are known to exist. The presence of these interactions complicates the design of an optimum multifactor pretreatment. Modern design-of-experiments techniques allow the simultaneous optimization of two or more variables. To improve the performance of lipase in a model reaction, we used a technique called the method of steepest ascent to optimize three variables simultaneously: pretreatment pH and sodium phosphate concentration, and the concentration of acetic acid (one of the reactants) in the reaction mixture. In only 26 experimental runs, this optimization process determined a combination of variable settings that yielded a reaction product approx 180 times faster than achieved with untreated enzyme. Evidence is presented to demonstrate that locating this optimum with single-factor experiments would be inefficient. This article demonstrates the efficiency of the method of steepest ascent particularly for evaluation of enzymatic reaction conditions exhibiting significant interactions.