High-efficiency liquid chromatography–mass spectrometry separations with 50 mm, 250 mm,and 1 m long polymer-based monolithic capillary columns for the characterization of complex proteolytic digests

In this study, high-efficiency LC–MS/MS separations of complex proteolytic digests are demonstrated using 50 mm, 250 mm, and 1 m long poly(styrene-co-divinylbenzene) monolithic capillary columns. The chromatographic performance of the 50 and 250 mm monoliths was compared at the same gradient steepness for gradient durations between 5 and 150 min. The maximum peak capacity of 400 obtained with a 50 mm column, increased to 485 when using the 250 mm long column and scaling the gradient duration according column length. With a 5-fold increase in column length only a 20% increase in peak capacity was observed, which could be explained by the larger macropore size of the 250 mm long monolith. When taking into account the total analysis time, including the dwell time, gradient time and column equilibration time, the 50 mm long monolith yielded better peptide separations than the 250 mm long monolithic column for gradient times below 80 min (n_c = 370). For more demanding separation the 250 mm long monolith provided the highest peak production rate and consequently higher sequence coverage. For the analysis of a proteolytic digest of Escherichia coli proteins a monolithic capillary column of 1 m in length was used, yielding a peak capacity of 1038 when applying a 600 min gradient.     

Interactions and two-phase coexistence in nonionic micellar solutions as determined by static light scattering

We suggest semi-phenomenological approaches for the pair interaction potential in aqueous C(m)E(n) solutions. These expressions are non-linear least squares fitted to static light scattering data from solutions of C(m)E4 and C(m)E8 surfactants in the long wavelength limit. From the resulting interaction parameters we calculate the location of the liquid/liquid two phase coexistence curves, which are in very good agreement with experimental data reported by others.     

A Survey of One-Dimensional Random Polymers

In the last decade there has been an enormous progress in the mathematical understanding of one-dimensional polymer measures, which are path measures that suppress self-intersections. We are currently in the situation that many interesting questions have either been answered, or that essential new ideas are needed. In this survey paper, we discuss the most relevant results, open questions, and heuristics.     

A versatile approach towards regioselective platinated DNA sequences

Undesired N(7) platination of 2'-deoxyguanosine residues at predetermined sites in an oligodeoxynucleotide (ODN) sequence is prevented by applying the sterically demanding diphenylcarbamoyl (DPC) as an O(6)-protecting group. The presence of a base-labile oxalyl linker between the immobilized 3'-nucleotide and controlled pore glass (CPG) allows cleavage of the protected ODN from the support and leaves DPC protection unaffected. This method provides an ODN with specifically blocked guanine-N(7) sites for platination. In the hexanucleotides prepared in this study, 5'-GGBGGT-3'(for B=T, C and A), a platinum GG adduct is introduced at G4,G5. These site-specific platinated hexamers were isolated in a yield of 65 %, and were fully characterized by using reversed-phase HPLC (high performance liquid chromotography), LCMS (liquid chromatography-mass spectrometry), MALDI-TOF MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry), PAGE (polyacrylamide gel electrophoresis) and Maxam-Gilbert sequencing analysis.     

The diatropic sigma ring currents of [pi2s + pi2s + pi2s] pericyclic transition states

Ab initio current-density maps for the (4n + 2)-electron transition states of two thermally allowed [pi2s + pi2s + pi2s] trimerisations, of ethyne to benzene (1), and of ethene to cyclohexane (2), show that both support sigma diatropic ring currents, dominated by four-electron sigma --> sigma* virtual excitation of HOMO electrons.     

Automated Solid‐Phase Synthesis and Structural Investigation of β‐Peptidosulfonamides and β‐Peptidosulfonamide/β‐Peptide Hybrids: β‐Peptidosulfonamide and β‐Peptide Foldamers are Two of a Different Kind

Fmoc‐protected β‐aminoethane sulfonylchlorides can be employed for efficient automated solid phase synthesis of β‐peptidosulfonamides and β‐peptidosulfonamide/β‐peptide hybrids containing one or more β‐peptidosulfonamide residues. Thus, Fmoc‐protected β‐aminoethane sulfonylchlorides 5a – c led to the hexa‐β‐peptidosulfonamide 9 and the nona‐β‐peptidosulfonamide 10 . In addition, the β‐peptidosulfonamide/β‐peptide hybrids 13 and 16 , consisting of six and nine β‐residues, respectively, and containing a single β‐peptidosulfonamide unit in the middle, as well as the peptidosulfonamide/β‐peptide hybrid 15 with nine β‐residues, including an N‐terminal β‐peptidosulfonamide residue, were synthesized by automated solid‐phase synthesis. Both CD and NMR spectroscopic measurements did not indicate any helical secondary structure for 9 and 10 . As was shown by CD‐measurements, the β‐peptidosulfonamide residue in the hybrids 13, 15 , and 16 acts as a ‘helix breaker', especially when located in the middle of the hybrid chain ( 13 and 16 ), but, although to a lesser extent, also at the N‐terminus.     

Eine einfache statische Methode zur Messung von Partialdrucken binärer Flüssigkeitsgemische

Zusammenfassung Zur Messung von Dampf-Flüssigkeits-Gleichgewichten läßt sich die dynamische Methode nicht immer vorbehaltlos anwenden. Es wurde deshalb eine einfache statisch arbeitende Apparatur entwickelt. Ihre Handhabung erfordert nur geringe Mehrarbeit gegenüber der dynamischen Meßmethode, ist aber wesentlich einfacher als die der bisher üblichen statischen Apparaturen. Der zeitliche Aufwand ist mit dem dynamischer Messungen vergleichbar.Die Meßmethode wurde an dem gut bekannten System Benzol-Cyclohexan geprüft. Die Prüfung ergab Überein-stimmung mit Messungen anderer Autoren. Die Gleichgewichtswerte sind thermodynamisch konsistent. Weiter wurden die Gleichgewichtswerte des Systems Benzol-Anilin bei 119,3°C gemessen. Auch hier sind die Werte thermodynamisch widerspruchsfrei. Die Apparatur eignet sich besonders für Systeme, bei denen die dynamische Meßmethode versagt.Mit 6 Abbildungen.Herrn Prof. Dr.L. Ebert zum 60. Geburtstag gewidmet.