Analysis of the selenium species distribution in cow blood by size exclusion liquid chromatography–inductively coupled plasma collision cell mass spectrometry (SEC–ICPccMS)

A method for performing rapid semiquantitative screening of the distribution of Se species in the blood of cows fed with a diet enriched in selenized yeast was optimized. The method was based on direct injection of a blood sample onto a high resolution size exclusion chromatographic column and fractionation of the selenium species. Selenium was detected on-line by ICP-MS with a collision cell. The concentrations of selenized haemoglobin and free selenomethionine were estimated using the chromatogram. The method was applied to a study involving 15 control and 15 treated dairy cows at four different supplementation time points. The increase in the selenomethionine and selenized haemoglobin was a linear function of the total selenium concentration. A threshold value of 600 ng ml(-1) of total Se was established beyond which selenomethionine could not be incorporated into the protein. No inorganic selenium was found to be present. The total selenium in cow blood correlated well with that in milk. The selenium supplementation did not change the protein distribution profiles for other essential elements (Cu, Fe, Mn, Zn).     

Can we predict the conformational preference of amides?

To what extent, if any, is the conformation of secondary amides revealed by theory? This question has now been addressed by computational methods using calculations at the B3LYP/6-31G level of theory and (1)H NMR spectroscopy. Both gas-phase and solvent studies predict a Z-anti conformation to be the lowest in energy for an evaluated series of acetamides. Moreover, Z-anti conformations may also be inferred from the chemical shifts of the N-CH alpha protons determined by NMR spectroscopy. Thus, a proton situated anti to the N-H proton consistently appears approximately 0.8 ppm further downfield than a proton situated gauche to the N-H proton. This finding, which could only be derived by using the DFT calculations of conformational preference as a guide to interpret the NMR data, might prove to be useful as a simple and convenient methodology for establishing amide conformation experimentally.     

The Geometry of Convex Transitive Banach Spaces

Throughout this paper, X will denote a Banach space, S=S(X)and B=B(X) will be the unit sphere and the closed unit ballof X, respectively, and G=G(X) will stand for the group of allsurjective linear isometries on X. Unless explicitly statedotherwise, all Banach spaces will be assumed to be real. Nevertheless,by passing to real structures, the results remain true for complexspaces. 1991 Mathematics Subject Classification 46B04, 46B10,46B22.     

Internal energy content of n-butylbenzene, bromobenzene, iodobenzene and aniline molecular ions generated by two-photon ionization at 266 nm. A photodissociation study

A technique to investigate photodissociation kinetics on a nanosecond time scale has been devised for molecular ions generated by multiphoton ionization (MPI) using mass-analyzed ion kinetic energy spectrometry. The branching ratio or rate constant has been determined for the photodissociation of the n-butylbenzene, bromobenzene, iodobenzene, and aniline molecular ions generated by MPI at 266 nm. The ion internal energies have been estimated by comparing the measured kinetic data with the previous energy dependence data. The analysis has shown that only those molecular ions generated by two-photon ionization contribute to the photodissociation signals. Around half of the available energy has been found to remain as molecular ion internal energy in the two-photon ionization process. Copyright 1999 John Wiley & Sons, Ltd.     

New chiral building blocks of β-peptoid analogs

The synthesis of chiral functionalized β-amino esters via the hydride reductive amination of chiral allenes was explored. These compounds can be regarded as β-peptoids building blocks bearing a chiral side chain at the nitrogen and at the same time retaining the β-amino acid side chain. β-Enamino esters were obtained from the nucleophilic addition of α-amino esters (l-Ala, d-Ala, l-Phe, l-Leu, l-Trp and d-Trp methyl esters) to 2,3-allenoates bearing a chiral auxiliary, which determines the stereochemistry outcome of the subsequent reduction reaction. It was also demonstrated that in the reduction of β-enamino esters derived from l-Pro and d-Pro methyl esters the chirality of the new chiral center is controlled by the α-amino ester moiety.     

Stable doubly charged positive molecular ions formed by direct attachment of alpha particles to HCN and HNC

The existence of [HeNCH](2+) and [HeCNH](2+) is examined by reliable high-level ab initio methods. It is shown that both species are metastable with respect to the proton loss process, but the activation barriers are high enough to accommodate several resonant states. Their estimated lifetimes are practically infinite for v<3, implying that the attachment of alpha particles to HNC and HCN yields kinetically stable dications. This could be an important factor in the cyanide chemistry in interstellar and comet environments.     

Prime Non-Commutative JB*-Algebras

We prove that if A is a prime non-commutative JB*-algebra whichis neither quadratic nor commutative, then there exist a primeC*-algebra B and a real number with < 1 such that A =B as involutive Banach spaces, and the product of A is relatedto that of B (denoted by , say) by means of the equality xy= xy+(1 – )yx. 2000 Mathematics Subject Classification46K70, 46L70.