An improved HPLC method for the investigation of L‐selenomethionine metabolism in rat gut contents

Selenomethionine (SeMet) is a widely used nutritional supplement that has potential benefit for people living in selenium‐deficient areas. Previous research has shown that selenium administered as SeMet undergoes significant enterohepatic recycling which may involve the gut microflora. In order to investigate this we have developed a simple method for the quantitation of l ‐SeMet in rat gut content suspensions prepared from jejunum, ileum, caecum and colon. After incubation of l ‐SeMet with gut content suspensions, samples were deproteinized with sulfosalicylic acid and derivatized with o‐phthaldialdehyde (OPA) and N‐acetyl‐l ‐cysteine (NAC). Mass spectrometry confirmed the formation of a 1:1:1 derivative of l ‐SeMet with OPA and NAC. Samples were analysed by reversed‐phase high‐performance liquid chromatography with fluorescence detection. The assay was linear in the concentration range 0.5–100 µg/mL (r² = 0.9992) with a limit of detection of 0.025 µg/mL (signal‐to‐noise ratio of 5). Intra‐day and inter‐day accuracies were 91.1–92.8 and 91.7–95.5%, respectively with corresponding precisions as relative standard deviation of <5%. Incubation of l ‐SeMet with gut content suspensions from different parts of the rat intestine showed that l ‐SeMet metabolism occurs mainly in the caecum. Copyright © 2009 John Wiley & Sons, Ltd.     

Approximate estimate of the form of molecular vibrations

Detailed polarized absorption and emission spectra are presented for anthracene and some of its methyl and methoxy derivatives in rigid solution at 77°K. PPP-SCF calculations show that no new states are introduced below 5 eV by the substitution. The observed effects of chemical substitution on state ordering, polarizations, and oscillator strength correlate quite well with the predictions of the PPP-SCF calculations. A vibrational analysis of the anthracene polarization spectra is carried out. In the near uv long-axis polarized absorption and fluorescence of anthracene, two vibronic origins are identified as a 1630 cm^?1b_1g molecular vibration and a weak 60 cm^?1b_g type of lattice vibration. All long-axis polarized structure in the near uv absorption can be assigned to Franck-Condon progressions built upon these vibronic origins in the ¹L_a band (which is electronically short-axis polarized). Differences in the spectral integrated transition intensity (oscillator strength) between the absorption and the emission reveal an additional long-axis component in the high energy region of the ¹L_a absorption which could be evidence for the hidden ¹L_b band in anthracene. However, there is no clear cut structural evidence for this state in the polarization spectrum. This hidden transition is made allowed by methoxy substitution. In the symmetric 2,3-dimethoxyanthracene, the ¹L_b band appears at 365 nm as a new transition. In 2-methoxyanthracene the ¹L_a and the ¹L_b are strongly mixed. The anomalous short-axis polarization of the ¹L_b band, predicted by the theory for 2-methoxyanthracene, is confirmed by the polarization data. Methoxy substitution also reveals new weak bands, located between the ¹L_b and ¹B_b bands, of B_1g and A_1g parentage, which are successfully predicted by the PPP-SCF calculations.     

The heI photoelectron spectra of the halogen azides,XN3(X = Cl and Br) and the halogen isocyanates,XNCO(X = Cl,Br and I)

High yield routes to the unstable halogen azides and isocyanates have permitted vacuum ultraviolet photoelectron spectra to be obtained for the chlorine and bromine azides, and the chlorine, bromine and iodine isocyanates. The results are compared with ab initio and semi-empirical calculations, leading to a reassignment of the photoelectron spectra of the parent acids, HN₃ and HNCO in the high energy region. The halogen azide and isocyanate photoelectron spectra provide an interesting investigation into how the orbitals of a linear pseudohalide grouping are perturbed by an off-azis halogen atom. A photoelectron spectrum for the unknown molecule FNCO is predicted.     

The photoelectron spectrum of ethylene sulphide

The He I photoelectron spectrum of ethylene sulphide is reported. There are six ionization potentials below 21 eV, the first, corresponding to ionization from a predominantly sulphur 3p orbital, occurring at 9.05 eV. The orbital types and symmetries have been assigned on the basis of semi-empirical calculations. The results indicate that in this highly strained cyclic compound sulphur d-orbital participation may be important.     

Determination of sampling constants for selenium in biological reference materials by neutron activation

Summary A cyclic instrumental neutron activation analysis method has been used to calculate sampling constants and to evaluate homogeneity for Se in five biological reference and certified reference materials, namely NRC lobster hepatopancreas (RM TORT-1), IAEA horse kidney (RM-H8), and NIST bovine liver (SRM-1577a), oyster tissue (SRM-1566) and mixed diet (RM-8431). The between-weight-range heterogeneity has been observed to be no greater than the within-weight-range heterogeneity. The subsampling standard deviation (S _s) has been found to be less than the measurement standard deviation (S _m) for H-8 (>5 mg sample) and TORT-1 (>50 mg). For 1577a, S _s is almost equal to S _m; while S _s is 2–3 times higher than S _m for the other two materials. The sampling constants varied between 0.04 and 3.0 g for four materials while the mixed diet had a value of 31 g.     

Generalized conjugate directions for unconstrained function minimization

The theory of unconstrained optimization has led to the development of a large class of iterative methods that reduce to conjugate direction methods when they are applied to quadratic functions. The purpose of this paper is to give a generalization of conjugate directions to nonquadratic functions.     

An I = 1 enhancement at a mass of 1550 MeV in the (Λπ) and (Σπ)-systems

Evidence is presented for an I = 1 enhancement observed in the reactions K^?p→Λ(Σ)K⁰₁K^±π^? at $\text{4.2}\text{GeV}\text{c}$ inciden momentum. The mass and width of the proposed new Y¹ are, respectively, (1553 ± 7) MeV) and (80 ± 30) MeV. A decay branching ratio $\text{Σπ}\text{(Σπ + Λπ)}\text{= (35 ± 12)\%}$ is also obtained.     

The ν2 + ν4 band of 12CF4

From a high-resolution diode laser spectrum of cooled ¹²CF₄, line assignments in ν₂ + ν₄ at 1066.4 cm^?1 have been made for tetrahedral subspecies to J = 20, and in many cases to higher J. Spectroscopic constants have been obtained from a least-squares fit of the Hamiltonian, and the relative intensities of the assigned lines have been calculated. The ground- and excited-state rotational constants, Coriolis constant, and splitting of the F₁ and F₂ vibrational substates have the values a.The CF bond length in the ground vibrational state is thus $\text{r}{}_0\text{= 1.31752 ± 0.00007}\text{A}\text{?}$. The analysis of a combination band such as this provides a method of obtaining ground-state spectroscopic constants of spherical-top molecules directly from the infrared spectrum, without the necessity of measuring weak “forbidden” transitions. The assignments allow accurate predictions of the frequencies emitted by the CO₂-pumped CF₄ laser.     

Electron scattering by atoms at intermediate energies II. Theoretical and experimental data for light atoms

Experimental data for the scattering of electrons by selected light atoms at intermediate energies have been collected and compared with the predictions of the theoretical models discussed in part I. The data discussed include elastic scattering and discrete excitation but ionization is not covered. The target atoms include H, He; the alkali metals; the alkaline earths; C, N, O and the rare gases from Ne to Xe, together with certain positive ions isoelectronic with these neutral atoms.