Dorso-ventral limb polarity and origin of the ridge: On the fringe of independence?

Molecular and developmental studies of limb pattern formation have recently gained widespread attention. The fact that vertebrate limbs are amenable to both genetic and embryological manipulations has established this model system as a valuable paradigm for studying vertebrate development. Limb buds are polarised along all three major axes and the establishment of the dorso-ventral (DV) polarity is dependent upon cues localised in the trunk, where a DV ectodermal interface is produced by confrontation of dorsal and ventral identities. By analogy to Drosophila imaginal disc development, this interface has been proposed to determine and position an ectodermal organising centre, the Apical Ectodermal Ridge (AER), controlling limb bud outgrowth. Recent fate mapping studies⁽¹⁾ and studies of genes regulating DV limb polarity^(2-6), AER formation^(7,8) and differentiation⁽⁹⁾ suggest, however, that DV patterning and AER induction, though coordinately regulated during limb bud outgrowth, may early on be more dissociated than expected.     

Bioproduction of lauryl lactone and 4-vinyl guaiacol as value-added chemicals in two-phase biotransformation systems

Recombinant Escherichia coli whole-cell biocatalysts harboring either a Baeyer–Villiger monooxygenase or ferulic acid decarboxylase were employed in organic-aqueous two-phase bioreactor systems. The feasibility of the bioproduction of water-insoluble products, viz., lauryl lactone from cyclododecanone and 4-vinyl guaiacol from ferulic acid were examined. Using hexadecane as the organic phase, 10∼16 g of lauryl lactone were produced in a 3-l bioreactor that operated in a semicontinuous mode compared to 2.4 g of product in a batch mode. For the decarboxylation of ferulic acid, a new recombinant biocatalyst, ferulic acid decarboxylase derived from Bacillus pumilus, was constructed. Selected solvents as well as other parameters for in situ recovery of vinyl guaiacol were investigated. Up to 13.8 g vinyl guaiacol (purity of 98.4%) were obtained from 25 g of ferulic acid in a 2-l working volume bioreactor by using octane as organic phase. These selected examples highlight the superiority of the two-phase biotransformations systems over the conventional batch mode.     

Development of a novel expression,ZIMAX/KZI,for determination of the counter-anion effect on the antimicrobial activity of tetrabutylammonium salts

Due to the increasing number of strains of drug-resistant bacteria, the development of new antibiotics has become increasingly important. The antibacterial properties of quaternary amines and their derivatives on both Gram-positive and Gram-negative bacteria are well known. However, an encompassing study with specific emphasis on the role of the counter-anion has not been reported in the literature. By monitoring the Zone of Inhibition of various concentrations of tetrabutylammonium (TBA) salts, we observed that the counter anion plays a significant role in activity. We developed a novel method of reporting activity using zone of inhibition tests (ZI_MAX/K_ZI) and found it to be strongly correlated with the minimum inhibitory concentration (MIC).     

A Parallel Algorithm for Nonequilibrium Molecular Dynamics Simulation of Shear Flow on Distributed Memory Machines

Abstract

An algorithm is described which allows Nonequilibrium Molecular Dynamics (NEMD) simulations of a fluid undergoing planar Couette flow (shear flow) to be carried out on a distributed memory parallel processor using a (spatial) domain decomposition technique. Unlike previous algorithms, this algorithm uses a co-moving, or Lagrangian, simulation box. Also, the shape of the simulation box changes throughout the course of the simulation. The algorithm, which can be used for two or three dimensional systems, has been tested on a Fujitsu AP1000 Parallel computer with 128 processors.     

Life is a Self-Organizing Machine Driven by the Informational Cycle of Brillouin

Acquiring information is indisputably energy-consuming and conversely, the availability of information permits greater efficiency. Strangely, the scientific community long remained reluctant to establish a physical equivalence between the abstract notion of information and sensible thermodynamics. However, certain physicists such as Szilard and Brillouin proposed: (i) to give to information the status of a genuine thermodynamic entity (k _B T ln2 joules/bit) and (ii) to link the capacity of storing information inferred from correlated systems, to that of indefinitely increasing organization. This positive feedback coupled to the self-templating molecular potential could provide a universal basis for the spontaneous rise of highly organized structures, typified by the emergence of life from a prebiotic chemical soup. Once established, this mechanism ensures the longevity and robustness of life envisioned as a general system, by allowing it to accumulate and optimize microstate-reducing recipes, thereby giving rise to strong nonlinearity, decisional capacity and multistability. Mechanisms possibly involved in priming this cycle are proposed.