Comparison of the ELP and multicanonical methods in simulation of the heptapeptide deltorphin

To investigate the performance of the energy landscape paving (ELP) procedure for peptides, we apply it here to deltorphin, a linear heptapeptide with bulky side chains (H-Tyr¹-D-Met²-Phe³-His⁴-Leu⁵-Met⁶-Asp⁷-NH₂) and compare the results with the Multicanonical method (MUCA) in regard of finding the low-energy structures. Deltorphin is modeled in vacuum by the potential energy function ECEPP. Received 23 July 2002 / Received in final form 18 September 2002 Published online 31 December 2002     

Unitary quantum groups,quantum projective spaces andq-oscillators

We discuss the parametrization of quantum groups in terms of independent operators. We find that this consideration leads to the parametrization ofSU _q(2) in terms of aq-oscillator plus a commuting phase. The commuting phase is naturally identified with the subgroupU(1) and the remaining cosetSU _q(2)/U(1)=CP _q(1) consists of aq-oscillator. For unitary quantum groupsSU _q (n), the analogous construction results in the quantum projective spaceSU _q(n+1)/U _q (n)=CP _q (n) being identified with then-dimensionalq-oscillator. This yields a nonlinear action of the quantum groupSU _q(n+1) on then-dimensionalq-oscillator.     

Simultaneous square-wave voltammetric determination of riboflavin and folic acid in pharmaceutical preparations

The square-wave voltammetric (SWV) behaviour of riboflavin and folic acid was studied at a static mercury drop electrode by square wave voltammetry. In 0.05M KCl (pH 5.89) a cathodic scan gave peaks at — 0.56 and — 0.87 V vs. Ag/AgCl for riboflavin and folic acid, respectively. The reduction peak currents are linearly dependent on the concentration of vitamins. Both vitamins can be simultaneously determined from the same voltammogram. The method proposed for the determination of riboflavin and folic acid in multivitamin tablets is very simple, rapid and does not involve time-consuming separation steps. The average contents of riboflavin and folic acid were found to be 14.8 ± 1.26% and 1.46 ± 2.66%, for tablet A and 9.86 ±1.40% and 1.47 ± 2.0% for tablet B, respectively.     

Synthesis, FT-Raman, FT-IR, NMR spectroscopic characterization and antimicrobial activity of new mixed aza-oxo-thia macrocyclic compounds

Series of new mixed aza-oxo-thia macrocyclic ligands {2,6,12,16-tetraaza-1,7,11,17-tetraoxo-9,19-dithia-[(4′-methyl-5′,4,3′)(14′-methyl-15′,14,13′)]ditriazine}cyclocosane (L ₁ ); {2,6,13,17-teraaza-1,7,12,18-tetraoxo-9,10,20,21-tetrathia-[(4′-methyl-5′,4,3′)(15′-methyl-14′,16′,15)]di-triazine}cyclodocosane (L ₂ ); {2,6,14,18-tetraaza-1,7,13,19-tetraoxo-10,22-dithia-[(4′-methyl-5′,3′,4)(16′-methyl-15′,17′,16)]ditriazine}cyclotetracosane (L ₃ ) and {2,6,15,19-tetraaza-1,7,14,12-tetraoxo-10,11,23,24-tetrathia-[(4′-methyl-5′,4,3′)(17′-methyl-8′,17,16′)]ditriazine}cyclohexa-cosane (L ₄ ) were synthesized. The structural features of the compounds have been studied by elemental analyses, Mass, FT-Raman, FT-IR, ¹H and ¹³C NMR spectroscopy. The antimicrobial activities of the ligands were evaluated using disk diffusion method in dimethyl sulfoxide as well as the minimal inhibitory concentration (MIC) dilution method, against 9 bacteria. The obtained results from disk diffusion method were assessed in side-by-side comparison with those of Penicillin-g, Ampicillin, Cefotaxime, Vancomycin, Oflaxacin, and Tetracyclin, well-known antibacterial agents. The results from dilution procedure were compared with Gentamycin as antibacterial and Nystatin as antifungal. The antifungal activities are reported on five yeast cultures namely Candida albicans, Kluyveromyces fragilis, Rhodotorula rubra, Debaryomyces hansenii, and Hanseniaspora guilliermondii, and the results are referenced with Nystatin, Ketaconazole, and Clotrimazole, commercial antifungal agents. In most cases, the compounds show strong antifungal activity in the comparison tests.     

Thermodynamic properties of a relativistic fermi system with a bose condensate at finite temperature

We investigate a procedure for obtaining the thermodynamical potential at finite temperature and density for a relativistic system of fermions in the presence of condensed bosons. After we have considered the formalism based on a relativistic form of the Landau theory of quantum liquids, we analyze a model with the Yukawa interaction between the spinor and the pseudoscalar fields. Finally we discuss our results in relationship to some known cases of condensation in high energy physics.     

A new and convenient synthesis of substituted benzobarrelenes

Bromination of 3-bromo-6,7-benzobicyclo [3.2.1] octa-2,6-diene at ?50°C gave anti-tribromo adduct (5) in essentially quantitative yield. The double dehydrobromination of (5) was achieved using potassium tert.- butoxide to give 2-bromo-benzobarrelene (7). Reaction of (7) with n-BuLi and subsequent quenching with CH₃I, CO₂, and dimethylformamide afforded the corresponding substituted benzobarrelenes in high yield.     

Anderson localization for one- and quasi-one-dimensional systems

We prove almost-sure exponential localization of all the eigenfunctions and nondegeneracy of the spectrum for random discrete Schrödinger operators on one- and quasi-one-dimensional lattices. This paper provides a much simpler proof of these results than previous approaches and extends to a much wider class of systems; we remark in particular that the singular continuous spectrum observed in some quasiperiodic systems disappears under arbitrarily small local perturbations of the potential. Our results allow us to prove that, e.g., for strong disorder, the smallest positive Lyapunov exponent of some products of random matrices does not vanish as the size of the matrices increases to infinity.