Spatio-temporal patterns driven by autocatalytic internal reaction noise

The influence that intrinsic local density fluctuations can have on solutions of mean-field reaction-diffusion models is investigated numerically by means of the spatial patterns arising from two species that react and diffuse in the presence of strong internal reaction noise. The dynamics of the Gray-Scott (GS) model with constant external source is first cast in terms of a continuum field theory representing the corresponding master equation. We then derive a Langevin description of the field theory and use these stochastic differential equations in our simulations. The nature of the multiplicative noise is specified exactly without recourse to assumptions and turns out to be of the same order as the reaction itself, and thus cannot be treated as a small perturbation. Many of the complex patterns obtained in the absence of noise for the GS model are completely obliterated by these strong internal fluctuations, but we find novel spatial patterns induced by this reaction noise in regions of parameter space that otherwise correspond to homogeneous solutions when fluctuations are not included.Comment: 12 pages, 18 figure

Dynamic Renormalization Group and Noise Induced Transitions in a Reaction Diffusion Model

We investigate how additive weak noise (correlated as well as uncorrelated) modifies the parameters of the Gray-Scott (GS) reaction diffusion system by performing numerical simulations and applying a Renormalization Group (RG) analysis in the neighborhood of the spatial scale where biochemical reactions take place. One can obtain the same sequence of spatial-temporal patterns by means of two equivalent routes: (i) by increasing only the noise intensity and keeping all other model parameters fixed, or (ii) keeping the noise fixed, and adjusting certain model parameters to their running scale-dependent values as predicted by the RG. This explicit demonstration validates the dynamic RG transformation for finite scales in a two-dimensional stochastic model and provides further physical insight into the coarse-graining analysis proposed by this scheme. Through several study cases we explore the role of noise and its temporal correlation in self-organization and propose a way to drive the system into a new desired state in a controlled way.Comment: 8 pages, 21 figure

Complex noise in diffusion-limited reactions of replicating and competing species

We derive exact Langevin-type equations governing quasispecies dynamics. The inherent multiplicative noise has both real and imaginary parts. The numerical simulation of the underlying complex stochastic partial differential equations is carried out employing the Cholesky decomposition for the noise covariance matrix. This noise produces unavoidable spatio-temporal density fluctuations about the mean field value. In two dimensions, the fluctuations are suppressed only when the diffusion time scale is much smaller than the amplification time scale for the master species.Comment: 10 pages, 2 composite figure

Procedimiento para la producción de sacarosa sintasa recombinante, su uso en la fabricación de kits de determinación de sacarosa, método de producción de ADPglucosa y método de obtención de plantas transgénicas cuyas hojas y órganos de reserva acumulen alto contenido en ADPglucosa y almidón

Procedimiento para la producción de sacarosa sintasa recombinante, su uso en la fabricación de kits de determinación de sacarosa, método de producción de ADPglucosa y método de obtención de plantas transgénicas cuyas hojas y órganos de reserva acumulen alto contenido en ADPglucosa y almidón.Peer reviewedUniversidad Pública de Navarra, Consejo Superior de Investigaciones Científicas (España)T3 Traducción de patente europe

Procedimiento para la producción de sacarosa sintasa recombinante su uso en la fabricación de kits de determinación de sacarosa producción de adpglucosa y obtención de plantas transgénicas cuyas hojas y órganos de reserva acumulen alto contenido en adpglucosa y almidón

Fecha de presentación internacional: 27.01.2005. - Titulares: Consejo Superior de Investigaciones Científicas (CSIC). - Universidad Pública de Navarra[EN] The invention relates to a method for the efficient production of large quantities of soluble recombinant sucrose synthase (SS) in the active form thereof, with the expression of the gene that codes for SS in a strain of Escherichia coli. The expression vector used enables the recombinant SS thus produced to have a histidine tail which facilitates the rapid purification thereof. In addition, the invention relates to sequences of mutated versions of the SS gene, which code for SS isoforms that are suitable for the production of ADPG. The invention also relates to an efficient method for the production of ADPG and UDPG, using the wild and mutated versions of recombinant SS. The invention further relates to the use of SS for the production of sucrose determination test devices. Finally, the invention relates to a method of obtaining transgenic plants which overexpress the SS gene, either constituently or in the reserve organs or leaves thereof, and which have a high concentration (both in the leaves and in the reserve tissues) of sucrose, ADPG, G6P and starch owing to the high ADPG-synthesising activity of SS.[ES] Se describe un procedimiento de producción eficiente de grandes cantidades SS recombinante soluble en su forma activa, mediante expresión del gen que codifica para la SS en una cepa de Escherichia coli. El vector de expresión utilizado permite que la SS recombinante producida posea una cola de histidinas que facilita su purificación de manera rápida. Asimismo se describen secuencias de versiones mutadas del gen de la SS que codifican para isoformas de la SS adecuadas para la producción de ADPG. Haciendo uso de las versiones "silvestre" y "mutada" de SS recombinante, se describe un método eficiente de producción de ADPG y UDPG. También se describe la utilización de la SS para la producción de dispositivos de ensayo de determinación de sacarosa. Por último se describe la obtención de plantas transgénicas que sobre-expresan el gen de la SS, bien constitutivamente, bien en hojas u órganos de reserva, y que poseen un contenido alto (tanto en hojas como en tejidos de reserva) en sacarosa, ADPG, G6P y almidón como resultado de la alta actividad sintetizadora de ADPG de la SS.Peer reviewe

Occurrence of more than one important source of ADPglucose linked to glycogen biosynthesis in Escherichia coli and Salmonella

AbstractTo explore the possible occurrence of sources, other than GlgC, of ADPglucose linked to bacterial glycogen biosynthesis we characterized Escherichia coli and Salmonella ΔglgCAP deletion mutants lacking the whole glycogen biosynthetic machinery. These mutants displayed the expected glycogen-less phenotype but accumulated ADPglucose. Importantly, ΔglgCAP cells expressing the glycogen synthase encoding glgA gene accumulated glycogen. Protein chromatographic separation of crude extracts of ΔglgCAP mutants and subsequent activity measurement analyses revealed that these cells possess various proteins catalyzing the conversion of glucose-1-phosphate into ADPglucose. Collectively these findings show that enterobacteria possess more than one important source of ADPglucose linked to glycogen biosynthesis