Double hydrophilic block copolymers with switchable secondary structure as additives for crystallization control

The synthesis and folding behavior of two different series of double hydrophilic block copolymers based on polyethyleneglycol and short acidic polypeptide blocks are described. The employment of those species in the crystallization of CaCO₃ and BaSO₄ shows that in contrast to the expectations from biomineral examples, a random conformation of the peptide is more advantageous in mineralization control than an -helical arrangement of the same chain, which is contradictory to the epitaxial adsorption model in biomineralization. Otherwise, the peptide block copolymers support formation of superstructures similar to those already reported, e.g. well-defined spherical, prolate, and dumbbell morphologies are found.     

Eine breit anwendbare Synthese fluoreszierender kondensierter α-Pyrone

In a two step procedure and in usually good yield an -pyrone ring can be annelated to (enolized) cyclic -dicarbonyl compounds like 4-hydroxy-2-pyrones, 4-hydroxycoumarins, 4-hydroxy-2-quinolones and more complex malonylheterocycles, but also to -naphthole.In a first step the combined action of triethyl orthoformate and arylamines upon the dicarbonyl system affords the anilinomethylene derivativesB in usually high yields.B is reacted with an active methylene nitrile (like alkyl cyano-acetates) and one equivalent of a strong base (like sodium methoxide or potassium hydroxide) in a polar aprotic solvent (like dimethylformamide). Subsequent acidification with dilute aqueous acid gives the corresponding -pyroneD with yields from 18 to 84%.The reaction sequence is broadly applicable, which is demonstrated by the synthesis of a series of known (3, 7, 16, 31) and novel (10, 19, 22, 25, 28, 34) heterocyclic systems. Most of them exhibit strong fluorescence in the visible with emission maxima between 450 and 510 nm.

208. Mitt.:H. Wittmann undF. Günzl, Z. Naturforsch.33b, 1540 (1978).     

Thalliumverbindungen als Katalysatoren für Umesterungen mit Glycidol und für Esteraustauschreaktionen mit Glycidylacetat

Thallium compounds as catalysts for transesterifications and ester exchange reactions The transesterification of di-, tri- and tetracarboxylic alkyl esters with 2,3-epoxy-propanol was investigated in the presence of various metal compounds as catalysts. It was found that only thallium compounds catalyse the reactions under mild conditions without decomposition of 2,3-epoxypropanol. Many thallium compounds also proved to be very good catalysts for the reactions of 2,3-epoxypropanol with alkoxysilanes and the ester exchange reactions of di-, tri- and tetracarboxylic alkyl esters with 2,3-epoxypropyl-acetate.     

Bindungsenergien von Phosphor–Stickstoff-Bindungen

The enthalpies of formation of P? N compounds with three-, four-and five-coordinated phosphorus have been determined by combustion calorimetry. From these data, using the energy values for atomisation, the P? N bond energies have been estimated to be 69 Kcal/Mole for P₄(NCH₃)₆ with three-coordinated P, and 79 Kcal/Mole for [PhNHP(O)NPh]₂ with tetrahedral phosphorus. For the compound C₂H₆Cl₆N₂P₂, in which the phosphorus is in a trigonal-bipyramidal hybrid function, the axial P? N bond energy is estimated to be 69 Kcal/Mole, and the equatorial one 77.5 Kcal/Mole.     

Interpretation of mass spectrometry data for high-throughput proteomics

Recent developments in proteomics have revealed a bottleneck in bioinformatics: high-quality interpretation of acquired MS data. The ability to generate thousands of MS spectra per day, and the demand for this, makes manual methods inadequate for analysis and underlines the need to transfer the advanced capabilities of an expert human user into sophisticated MS interpretation algorithms. The identification rate in current high-throughput proteomics studies is not only a matter of instrumentation. We present software for high-throughput PMF identification, which enables robust and confident protein identification at higher rates. This has been achieved by automated calibration, peak rejection, and use of a meta search approach which employs various PMF search engines. The automatic calibration consists of a dynamic, spectral information-dependent algorithm, which combines various known calibration methods and iteratively establishes an optimised calibration. The peak rejection algorithm filters signals that are unrelated to the analysed protein by use of automatically generated and dataset-dependent exclusion lists. In the "meta search" several known PMF search engines are triggered and their results are merged by use of a meta score. The significance of the meta score was assessed by simulation of PMF identification with 10,000 artificial spectra resembling a data situation close to the measured dataset. By means of this simulation the meta score is linked to expectation values as a statistical measure. The presented software is part of the proteome database ProteinScape which links the information derived from MS data to other relevant proteomics data. We demonstrate the performance of the presented system with MS data from 1891 PMF spectra. As a result of automatic calibration and peak rejection the identification rate increased from 6% to 44%.Abbreviations 2-DE Two-dimensional gel electrophoresis - MALDI Matrix-assisted laser desorption ionisation - PMF Peptide mass fingerprinting - MS Mass spectrometry - TOF Time of flight     

Heterobi‐ and ‐trinuclear Complexes with an Amino(ethynyl)carbene as Bridging Ligand

The sequential reaction of the amino(trimethylsilyl)carbene complex [(CO)₅W=C(NH₂)C≡CSiMe₃] ( 1 ) with nBuLi and [I‐Fe(CO)₂Cp] affords the C(carbene)‐N bridged heterobinuclear complex [(CO)₅W=C{NHFe(CO)₂Cp}C≡CSiMe₃] ( 2 ). Desilylation of 1 is achieved by treatment with KF in THF/MeOH. From the reaction of the resulting complex [(CO)₅W=C(NH₂)C≡CH] ( 3 ) with nBuLi and [I‐Fe(CO)₂Cp] two binuclear WFe compounds in a ratio of approximately 1:1 are obtained: the C(carbene)‐C≡C bridged complex 4 and the C(carbene)‐N bridged complex 5 . Repetition of the deprotonation/metallation sequence yields the trinuclear WFe₂ complex 6 . One Fe(CO)₂Cp fragment in 6 is bonded to the amino group and the other one to the terminal carbon atom of the ethynyl substituent. The analogous reaction of 3 with nBuLi and [Br‐Ni(PMe₂Ph)₂Mes] gives a ca. 1:1 mixture of two heterobinuclear complexes ( 7 and 8 ). Complex 7 is bridged by the C(carbene)‐C≡C and complex 8 by the C(carbene)‐N fragment. Subsequent reaction of 7 with BuLi and [Br‐Ni(PMe₂Ph)₂Mes] finally affords the trinuclear WNi₂ complex 9 related to 6 . The solid‐state structure of 2 is established by an X‐ray diffraction analysis. The spectroscopic data of the bi‐ and trinuclear complexes indicate electronic communication between the metal centers through the bridging group.