The conjugacy problem for groups of alternating prime tame links is polynomial-time

An alternating projection of a prime link can to used to produce a group presentation (of the link group under free product with the infinite cyclic group) with some useful peculiarities, including small cancellation conditions. In this presentation, conjugacy diagrams are shown to have the form of a tiling of squares in the Euclidean plane in one of a limited number of shapes. An argument based on the shape of the link projection is used to show that the tiling requires no more square tiles than a linear function of word length (with constant multiple based on the number of link crossings). It follows that the computation time for testing conjugacy of two group elements (previously known to be no worse than exponential) is bounded by a cubic polynomial. This bounds complexity in the original link group.

     

Absolute Configuration of Multifidene and Viridiene,the Sperm Releasing and Attracting Pheromones of Brown Algae

The absolute configurations of the two algal pheromones multifidene 1 and viridiene 2 were determined as (+)-(3S, 4S)-3-[(Z)-1-butenyl]-4-vinylcyclopentene and (+)-(3R, 4S)-3-[(1Z)-1, 3-butadienyl]-4-vinylcyclopentene, respectively. The strategy involves enzyme-initiated asymmetric synthesis of the ring-saturated pheromone analogues (+)- 8a and (?)- 8b and their subsequent catalytic hydrogenation to the chiral cycloalkanes 9a and 9b , only the letter of which is also obtained from the two natural messengers (+)- 1 or (+)- 2 . Biological activity assays proved these enantiomers of 1 or 2 to be the characteristic pheromones for male gametes of the seaweeds Syringoderma, Cutleria multifida and Chorda tomentosa.     

Identification of proteinaceous binding media of easel paintings by gas chromatography of the amino acid derivatives after catalytic hydrolysis by a protonated cation exchanger

Summary A procedure for the hydrolysis of proteins, based on catalysis by the protonated form of a strong cation exchanger, was established for proteinaceous binding media (e.g. casein, egg, animal collagene) used for objects of art. The experimental parameters for the hydrolysis (temperature, time) were optimized, as well as the conditions for sorption and desorption of the amino acids on the cation exchanger. The results for the identification of proteins by the gas chromatographic pattern of the amino acid derivatives, after hydrolysis by the ion exchanger and by hydrochloric acid were compared. The former method proved to be more efficient due to the mild conditions, avoiding the formation of humins in the presence of carbohydrates, and reducing the dissolution of pigments. The method was applied to identify the proteinaceous vehicles of samples from priming and paint layers of easel and wall paintings from the 16th and 18th century.     

7-Deazaguanosine: Synthesis of an oligorbonucleotide building block and disaggregation of the U-G-G-G-G-U G4 structure by the modified base

Building blocks derived from 7-deazaguanosine (c⁷G, 1 ) were prepared for solid-phase oligoribonucleotide synthesis. Compound 1 was converted into the isobutyurl derivative 2b and the (dimethylamino)methylidene compound 3 (Scheme 1). After tritylation (→ 4a , b ), silylation was studied with regard to regioselectivity. It was found that the triisopropylsilyl group in combination with the (dimethylamino)methylidene residue gave the highest 2′ -selectivity (→ 5e ). The 2′ -O -silyl derivative 5e was reacted with PCl₃ affording the 3′ -phosphonate 7 which was used in solid-phase oligoribonucleotide synthesis. Oligonucleotides derived from U-G-G-G-G-U with an increasing number of c⁷G residues instead of G were synthesized. Aggregation was studied by polyacrylamidegel electrophoresis and CD Spectroscopy. Disaggregation of the G₄-structure of U-G-G-G-G-U was observed when c⁷G replaced G, demonstrating that guanine N(7) participates in the aggregation process.     

Orientierungsverhalten von segmentierten Polyurethanen in Abhängigkeit von der Folienpräparation und dem Zeitpunkt der Orientierungsbestimmung

Zusammenfassung Bei der Drehung von entmischten Block-Copolymeren treten kontinuums- und molekularmechanische Dremomente an den Domänen der härteren Phase auf. Dies führt im Fall der segmentierten Polyurethane zu einer anfänglichen Negativorientierung der Hartsegmente, die als Hinweis auf eine stark anisotrope Domänenform zu verstehen ist, wobei die Hartsegmente in Richtung der kurzen Domänenachse liegen. Hiervon ausgehend werden in der vorliegenden Arbeit Zusammenhänge zwischen der Probenpräparation (ca. 6m dicke Folien) und der Negativorientierung erarbeitet, um so ein Kriterium für die von Fall zu Fall unterschiedliche Domänenmorphologie zu gewinnen. Gleichzeitig ergeben sich Hinweise auf unterschiedliche Relaxationsmechanismen, die sich überlagern und so teilweise eine Erhöhung, teilweise eine Erniedrigung der Orientierung bedingen.Herrn Prof. Dr. F. H. Müller gewidmet.     

Multi-parameter investigation of tandem mass spectrometry in a linear ion trap using response surface modelling

The feasibility of experimental design in combination with subsequent response surface modelling was illustrated for the prediction and interpretation of tandem mass spectrometric (MS/MS) fragmentation data using a linear quadrupole ion trap under various experimental conditions. The instrumental parameters included were (i) the pressure of the collision gas, (ii) the collision energy, (iii) the fill time of the linear ion trap and (iv) the scan rate. The spectral intensity and width of five fragment ions of the doubly charged neuro-active peptide bombesin were used for evaluation, and all experiments were performed so as to resemble the results obtained from a liquid chromatographic peak. The reported results show how fairly simple mathematical tools can be utilized successfully to describe fundamental mechanisms associated with multiple collisional activation and collision-induced dissociation processes without an extensively controlled experimental environment. Most beneficial, using the suggested approach, is the ability to study interaction (synergistic) effects between various parameters. As was realized from the results, many interaction effects are indeed significant. For example, the effect on the signal intensity of different collision gas pressure settings is strongly dependent on the settings of the other parameters. The described approach can easily be adopted for optimization purposes of any MS/MS experiment.