Solid-phase capture and release of arginine peptides by selective tagging and boronate affinity chromatography

A method for the selection of arginine-containing peptides from a mixture by a solid phase capture and release technique is presented. The method is based on the covalent modification of the guanidine group of arginine with 2,3-butanedione and phenylboronic acid under alkaline conditions. Using polymeric materials with immobilised phenylboronic acid the arginine-peptides can be captured on a solid support while arginine-free peptides are not covalently bound and can be washed away. Finally, the arginine-peptides can be cleaved again from the boronic acid beads due to the reversibility of the reaction. The recovered peptides are then analysed by liquid chromatography-tandem mass spectrometry. The method was optimised with model peptides with regard to the non-specific binding of arginine-free peptides and quantitative cleavage of the label after the selection step. Using an adequate protocol, the applicability towards more complex samples was successfully tested with a tryptic digest of a mixture of three standard proteins.     

Das Verhalten von Mono- und Diorganylphosphansulfiden gegenüber Metallcarbonylsystemen. VIII [1]; Die Kristall- und Molekülstruktur von Pentacarbonyl(dimethylmercaptophosphan)-chrom

Inhaltsübersicht. Die S-verknüpfte Verbindung (OC)₃CrSPH(CH₃)₂ isomerisiert sich oberhalb 25°C zu dem Mercaptophosphan-Komplex (OC)₅CrP(CH₃)₂SH. Dieser kristallisiert monoklin in der Raumgruppe P2₁/c mit den Citterkonstanten a = 6,882, b = 13,290, c = 13,224 Å, β = 91,60° und vier Molekeln in der Elementarzelle. In der Kristallstruktur (R = 0,085) sind die Chromatome pseudooktaedrisch koordiniert von fünf CO-Gruppen und dem Mercaptophosphanliganden (Cr—P = 2,344 Å). The Behaviour of Mono- and Diorganylphosphane Sulphides towards Metal Carbonyl Systems. VIII. Crystal and Molecular Structure of Pentacarbonyl(dimethylmereaptophosphane) chromium Abstract. The S-linked compound (OC)₅CrSPH(CH₃)₂ isomerizes to the mercaptophosphane complex (OC)₅CrP(CH₃)₂SH above 25°C. The latter crystallizes monoclinic in the space group P2₁/c with the lattice constants a = 6.882, b = 13.290, c = 13.224 Å, β = 91.60° and four molecules per unit cell. In the crystal structure (R = 0.085) the chromium atoms are pseudooctahedrally coordinated by five CO groups and the mercaptophosphane ligand (Cr—P) = 2.344 Å).     

An efficient step size control for continuation methods

In solving a nonlinear equation by the use of a continuation method one of the crucial problems is the choice of the step sizes. We present a model for the total computational cost of a standard numerical continuation process and solve the problem of optimal step size control for this model. Using the theoretical results as a basis, we develop an adaptive step size algorithm for Newton's method. This procedure is computationally inexpensive and it gives quite satisfactory results compared to some other numerical experiments found in the literature.     

Absorptionsquerschnitte und Transmissionskoeffizienten für Protonen und Neutronen nach dem optischen Modell

T _l -values and absorption cross sections for protons and neutrons are calculated with optical potentials, which have been fitted to experimental scattering data. Values are given forZ=10, 20, 30, 50, 70, 90, and energies between 0.1 und 25 MeV. For protons we used the local optical potential ofPerey and for neutrons the nonlocal optical potential ofPerey andBuck. The results are compared with those of other optical potentials. In addition it is shown, that the spin-orbit-interaction leads toT _{l j} -values which sometimes differ appreciably depending whetherj equalsl+1/2 orl?1/2.