On the geometry of elementary flux modes.

Elementary flux modes (EFMs) play a prominent role in the constraint-based analysis of metabolic networks. They correspond to minimal functional units of the metabolic network at steady-state and as such have been studied for almost 30 years. The set of all EFMs in a metabolic network tends to be very large and may have exponential size in the number of reactions.

Capturing air-water interface biofilms for microscopy and molecular analysis.

Described here is a simple and versatile technique for capturing small samples of the thin biofilm that is located at the meniscus of almost every air-water interface (AWI), an electrostatically distinct aquatic domain/habitat. The method uses a microscope slide (and other supporting surfaces) coated in the lab with a collodion membrane, which has a strong affinity for the upper surface of the AWI biofilm. The structural integrity of the biofilm is maintained during the capture process, and components of the biofilm are effectively separated from the subtending liquid.

Silica-polypeptide composite particles: controlling shell growth.

A method is presented for preparing core-shell silica-polypeptide composite particles with variable and controllable shell growth. The procedure is demonstrated using poly(carbobenzoxy-L-lysine) and poly(benzyl-L-glutamate); after deprotection, these can lead to the most common basic and acidic homopolypeptides, poly(L-lysine) and poly(L-glutamic acid). Control over shell thickness is made possible by sequential addition of N-carboxyanhydride peptide monomer to surfaces that have been functionalized with an amino initiator combined with a surface passivation agent.

Coalescence phenomena in 1D silver nanostructures.

Different coalescence processes on 1D silver nanostructures synthesized by a PVP assisted reaction in ethylene glycol at 160 °C were studied experimentally and theoretically. Analysis by TEM and HRTEM shows different defects found on the body of these materials, suggesting that they were induced by previous coalescence processes in the synthesis stage. TEM observations showed that irradiation with the electron beam eliminates the boundaries formed near the edges of the structures, suggesting that this process can be carried out by the application of other means of energy (i.

Temperature sensitivity and cell division defects in an Escherichia coli strain with mutations in yghB and yqjA, encoding related and conserved inner membrane proteins.

Ludox density gradients were used to enrich for Escherichia coli mutants with conditional growth defects and alterations in membrane composition. A temperature-sensitive mutant named Lud135 was isolated with mutations in two related, nonessential genes: yghB and yqjA. yghB harbors a single missense mutation (G203D) and yqjA contains a nonsense mutation (W92TGA) in Lud135.