Structural elucidation of biologically active neomycin N‐octyl derivatives in a regioisomeric mixture by means of liquid chromatography/ion trap time‐of‐flight mass spectrometry

Structural elucidation of six regioisomers of mono‐N‐octyl derivatized neomycin is achieved using MSⁿ (up to n = 4) on an ion trap time‐of‐flight (IT‐TOF) instrument equipped with electrospray ionization. The mixture of six derivatized neomycin analogues was generated by reductive amination in a shotgun synthetic approach. In parallel to the liquid chromatography/mass spectrometry (LC/MS) detection, the antibacterial activity of the neomycin regioisomers was tested by post‐column addition of buffer and bacterial inocula, subsequent microfractionation of the resulting mixture, incubation, and finally a chemiluminescence‐based bioactivity measurement based on the production of bacterial ATP. The MS‐based high‐resolution screening approach described can be applied in medicinal chemistry to help in designing and producing new antibiotic substances, which is particularly challenging due to the high functionality of most antibiotic substances, therefore requiring advanced (hyphenated) separation and detection techniques for compound mixtures. Copyright © 2010 John Wiley & Sons, Ltd.     

Neue Wege zu Polysilanen

Summary Disilane derivatives undergo disproportionation reactions to polysilanes. Investigated were 1,2-dimethyldisilane and 1,2-dimethyltetrachlorodisilane with catalysts like NH₄Cl, AgCN, and Nacyanamide. In case of 1,2-dimethyldisilane, with more than catalytic amounts of NH₄Cl, a nitrogen containing polysilane is formed. Two new compoundsMeSiH(NCO)₂ andMe ₂Si₂(NCO)₄ were synthesized and characterized. The last one leads to a polymer at heating. Additionally an electrochemical formation of polydimethylsilane is described.

     

Error linear complexity measures for multisequences

Complexity measures for sequences over finite fields, such as the linear complexity and the k-error linear complexity, play an important role in cryptology. Recent developments in stream ciphers point towards an interest in word-based stream ciphers, which require the study of the complexity of multisequences. We introduce various options for error linear complexity measures for multisequences. For finite multisequences as well as for periodic multisequences with prime period, we present formulas for the number of multisequences with given error linear complexity for several cases, and we present lower bounds for the expected error linear complexity.     

High-performance liquid chromatographic analysis of p-nitrophenol and its conjugates in biological samples

p-Nitrophenol (pNP) and its conjugated metabolites, generated in a perfused rat liver preparation, are readily separated and quantitated in serum perfusate and bile samples using a reverse-phase high-performance liquid chromatographic method. Serum perfusate samples can be analyzed following protein precipitation with acetonitrile: following protein precipitation with 1.5 M perchloric acid (1 part to 2 parts serum) there was degradation of pNP sulfate to pNP when samples were stored at room temperature. pNP can also be analyzed in blood perfusate samples following extraction with a number of organic solvents including ethyl acetate or isobutanol-methylene chloride (4:1, v/v). Rat liver perfusions at a constant input concentration of 40 microM demonstrated a high hepatic extraction ratio of pNP (mean of 0.90) due to the formation of the sulfate and glucuronide conjugates; no pNP glucoside was detected in perfusate or bile samples.     

Transient dynamical behavior and phase transitions in magnetic systems

It was recently suggested that transient dynamical properties were of some use to predict equilibrium critical properties of 2D and 3D models of statistical mechanics on the lattice. We investigate such dynamical properties for three related models with competitive interactions, namely the ANNNI model, the brickwork model, and the BNNNI model. In spite of known differences in their equilibrium phase diagrams, our simulations display similar transient dynamical behaviors for all three models. The reliability of this method for probing equilibrium properties seems therefore questionable even for rather simple magnetic models without any structural disorder.On leave from Centre de Physique Théorique, Ecole Polytechnique, 91128, Palaiseau Cedex, France.     

Some Notes on the Linear Complexity of Sidel’nikov-Lempel-Cohn-Eastman Sequences

We continue the study of the linear complexity of binary sequences, independently introduced by Sidel’nikov and Lempel, Cohn, and Eastman. These investigations were originated by Helleseth and Yang and extended by Kyureghyan and Pott. We determine the exact linear complexity of several families of these sequences using well-known results on cyclotomic numbers. Moreover, we prove a general lower bound on the linear complexity profile for all of these sequences.