Macrocyclic Antibiotics as Separation Agents

Macrocyclic antibiotics having ring structures with at least 10 members act as separation agents in crystallization, precipitation, filtration, electrophoresis and chromatography. The macrocyclic antibiotics include ansamacrolides, macrolides, marocyclic peptides, polyenes and derivatives thereof. The process has been found to be especially advantageous for separation of optical isomers by electrophoresis and chromatography

Evidence For Multiple Retention Mechanisms. Cyclodextrin Stationary Phases For The Gas-solid Chromatographic Separation Of Light Hydrocarbons

Cyclodextrin, bonded to silica gel and used as a gas-solid chromatographic (GSC) stationary phase provides a practical and efficient means for separating a wide variety of volatile C1-C7 hydrocarbons at ambient to elevated temperatures. Conditioning the columns at high temperature (300°C) for several hours increased efficiency and resolution. The adsorption of these light hydrocarbons involves multiple retention mechanismns. For unsaturated hydrocarbons, the cyclodextrin GSC column can act as a polar stationary phase analogous to silica gel. However, for saturated hydrocarbons, it acts as a non-polar phase. Evaluation of the columns and an analogous silica gel column with hydrocarbon standards is reported. Capacity factors and chromatograms are presented for compounds analyzed on these GSC stationary phases. © 1993

Use of a Macrocyclic Antibiotic, Rifamycin B, and Indirect Detection for the Resolution of Racemic Amino Alcohols by CE

Ansamycins are a very specific class of macrocyclic antibiotics of which the rifamycins are among the better-known members. Rifamycins bind to and inhibit DNA polymerase. Rifamycin B (the most easily obtained ansamycin) is negatively charged and is shown to associate with and enantioselectively resolve several chiral amino alcohols including terbutaline, isoproterenol, bamethan, metaproterenoi, synephrine, metanephrine, salbutamol, epinephrine, norphenylephrine, ephedrine, ψ-ephedrine, octopamine, norepinephrine, normetanephrine, metoprolol, alprenolol, atenolol, and oxprenolol. A description of the structure and properties of rifamycins, in general, and rifamycin B, in particular, is given. The complexation and chiral recognition of the aforementioned racemic compounds by rifamycin B is afforded by multiple interactions of which charge-charge, hydrogen-bonding, and hydrophobic inclusion interactions most likely dominate in hydroorganic solvents. The effect of various experimental factors on enantiomeric resolution is discussed in terms of optimizing the CE separations. Since most chiral antibiotic macrocycles are ionizable, somewhat flexible, and contain hydrophobic and hydrophilic moieties, they tend to be significantly affected by variations in the solution environment. © 1994, American Chemical Society. All rights reserved

A Step Towards A Computing Grid For The LHC Experiments: ATLAS Data Challenge 1

The ATLAS Collaboration at CERN is preparing for the data taking and analysis at the LHC that will start in 2007. Therefore, a series of Data Challenges was started in 2002 whose goals are the validation of the Computing Model, of the complete software suite, of the data model, and to ensure the correctness of the technical choices to be made for the final offline computing environment. A major feature of the first Data Challenge (DC1) was the preparation and the deployment of the software required for the production of large event samples as a worldwide distributed activity. It should be noted that it was not an option to "run the complete production at CERN" even if we had wanted to; the resources were not available at CERN to carry out the production on a reasonable time-scale. The great challenge of organising and carrying out this large-scale production at a significant number of sites around the world had therefore to be faced. However, the benefits of this are manifold: apart from realising the required computing resources, this exercise created worldwide momentum for ATLAS computing as a whole. This report describes in detail the main steps carried out in DC1 and what has been learned form them as a step towards a computing Grid for the LHC experiments