Crystallization of Arthrobacter sp. strain 1C N-(1-D-carboxyethyl)-L-norvaline dehydrogenase and its complex with NAD+

The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres.     

A characterization of polyhedral market games

The class of games without side payments obtainable from markets having finitely many commodities and continuous concave utility functions is considered. It is first shown that each of these so-called market games is totally balanced, for a reasonable generalization of the idea of a balanced side payment game. It is then shown that among polyhedral games (i.e., games for which each (V(S) is a polyhedron), this property characterizes the market games.     

A simple proof that every matroid is an intersection of fundamental transversal matroids

We give a new proof of a theorem of Bondy and Welsh. Our proof is simpler than previous ones in that it makes no use of Hall's theorem on the existence of a transversal of a family of sets.     

The solution to a matroid problem of Knuth

In this note we answer a question posed by Knuth in his recent paper “Random matroids”.     

Challenges in small screening laboratories: implementing an on-demand laboratory information management system

The Miami Project to Cure Paralysis, part of the University of Miami Miller School of Medicine, includes a laboratory devoted to High Content Analysis (HCA) of neurons. The goal of the laboratory is to uncover signaling pathways, genes, compounds, or drugs that can be used to promote nerve growth. HCA permits the quantification of neuronal morphology, including the lengths and numbers of axons. HCA of various libraries on primary neurons requires a team-based approach, a variety of process steps and complex manipulations of cells and libraries to obtain meaningful results. HCA itself produces vast amounts of information including images, well-based data and cell-based phenotypic measures. Documenting and integrating the experimental workflows, library data and extensive experimental results is challenging. For academic laboratories generating large data sets from experiments involving thousands of perturbagens, a Laboratory Information Management System (LIMS) is the data tracking solution of choice. With both productivity and efficiency as driving rationales, the Miami Project has equipped its HCA laboratory with an On Demand or Software As A Service (SaaS) LIMS to ensure the quality of its experiments and workflows. The article discusses how the system was selected and integrated into the laboratory. The advantages of a SaaS based LIMS over a client-server based system are described.     

Kuratowski's and Wagner's theorems for matroids

In an earlier paper we proved the following theorem, which provides a strengthening of Tutte's well-known characterization of regular (totally unimodular) matroids: A binary matroid is regular if it does not have the Fano matroid or its dual as a series-minor (parallel-minor). In this paper we prove two theorems (Theorems 5.1 and 6.1) which provide the same kind of strengthening for Tutte's characterization of the graphic matroids (i.e., bond-matroids). One interesting aspect of these theorems is the introduction of the matroids of “type R”. It turns out that these matroids are, in at least two different senses, the smallest regular matroids which are neither graphic nor cographic (Theorems 6.2 and 6.3).