Rotational invariance in the M(atrix) formulation of type IIB theory

The matrix model formulation of M-theory can be generalized by compactification to ten-dimensional type II string theory, formulated in the infinite momentum frame. Both the type IIA and IIB string theories can be formulated in this way. In the M-theory and type IIA cases, the transverse rotational invariance is manifest, but in the IIB case, one of the transverse dimensions materializes in a completely different way from the other seven. The full O(8) rotational symmetry then follows in a surprising way from the electric-magnetic duality of supersymmetric Yang-Mills field theory.     

Combinatorial mutasynthesis of flavonoid analogues from acrylic acids in microorganisms

Flavonoids are plant secondary metabolites often used as nutraceutical supplements, but a growing number of unnatural flavonoids are being investigated as therapeutic agents. Cultures of Saccharomyces cerevisiae expressing recombinant flavonoid enzymes, including 4-coumaroyl:CoA ligase (4CL), chalcone synthase (CHS), chalcone isomerase (CHI), and flavanone 3beta-hydroxylase (FHT), produced novel flavanones and dihydroflavonols when fed with a number of aromatic acrylic acids. The flavonoid network also exhibited broad substrate specificity by converting muconic acid into a unique polypropanoid.     

Limitations of the "tethering" strategy for the detection of a weak noncovalent interaction

The success of applying the tethering strategy in a synthetic molecular system strongly depends on the experimental conditions and is related to the strength of the noncovalent interaction and the competition between the 'captured' and unbound ligand for the recognition site.     

Proof of principle of a generalized fuzzy Hough transform approach to peak alignment of one-dimensional <Superscript>1</Superscript>H NMR data

In metabolic profiling, multivariate data analysis techniques are used to interpret one-dimensional (1D) ¹H NMR data. Multivariate data analysis techniques require that peaks are characterised by the same variables in every spectrum. This location constraint is essential for correct comparison of the intensities of several NMR spectra. However, variations in physicochemical factors can cause the locations of the peaks to shift. The location prerequisite may thus not be met, and so, to solve this problem, alignment methods have been developed. However, current state-of-the-art algorithms for data alignment cannot resolve the inherent problems encountered when analysing NMR data of biological origin, because they are unable to align peaks when the spatial order of the peaks changes—a commonly occurring phenomenon. In this paper a new algorithm is proposed, based on the Hough transform operating on an image representation of the NMR dataset that is capable of correctly aligning peaks when existing methods fail. The proposed algorithm was compared with current state-of-the-art algorithms operating on a selected plasma dataset to demonstrate its potential. A urine dataset was also processed using the algorithm as a further demonstration. The method is capable of successfully aligning the plasma data but further development is needed to address more challenging applications, for example urine data. Figure Traces of NMR peaks visualizing the Generalized Fuzzy Hough Transform (GFHT) method for elucidating peak correspondence between samples. The spectra are sorted according to one shift sensitive peak and reveals that other peaks exhibit a similar shift pattern. This pattern(s) can now be searched for using the GFHT. The red and black spectra in the figure are the most shifting spectra (top and bottom), by following the GFHT traces peak correspondence is easily established although peaks change spatial location Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Protein refolding assisted by periodic mesoporous organosilicas

Herein we report a new strategy for protein refolding by taking advantage of the unique surface and pore characteristics of ethylene-bridged periodic mesoporous organosilica (PMO), which can effectively entrap unfolded proteins and assist refolding by controlled release into the refolding buffer. Hen egg white lysozyme was used as a model protein to demonstrate the new method of protein refolding. Through loading of denatured proteins inside uniform mesoporous channels tailored to accommodate individual protein, protein aggregation was minimized, and the folding rate was increased. Poly(ethyleneglycol) (PEG)-triggered continuous release of entrapped denatured lysozyme allowed high-yield refolding with high cumulative protein concentrations. The new method enhances the oxidative refolding of lysozyme (e.g., over 80% refolding yield at about 0.6 mg/mL).     

Synthesis of all low-energy stereoisomers of the tris(pyrrolidinoindoline) alkaloid hodgkinsine and preliminary assessment of their antinociceptive activity

The previously unknown stereoisomers 3, 4, ent-1, and ent-4 of the tris(pyrrolidinoindoline) alkaloids hodgkinsine (1) and hodgkinsine B (2) were prepared by stereocontrolled total synthesis. In each synthesis, a catalyst-controlled intramolecular Heck reaction was the key step in appending a third cis-pyrrolidinoindoline ring to a hexacyclic chimonanthine precursor. Results of the preliminary evaluation of these hodgkinsine stereoisomers in the tail flick and capsaicin pain models are reported.     

Curvature and torsion of material lines in chaotic flows

The deformation of a material line as it evolves in a chaotic flow is considered. Of particular interest are the curvature and torsion as a function of arclength or material coordinate along the line and their near singular behavior that develops as the deformation proceeds. Recent work [Thiffeault 2004. Physica D 198, 169–181] has established an interesting connection between local line stretch and curvature for regions of high curvature. The present effort confirms this connection and develops a similar relation between torsion and curvature for regions of high absolute torsion. In addition it is shown that certain properties of the strain tensor play a key role in the location and structure of the near singular behavior in curvature.     

Biaxial deformation of dough using the bubble inflation technique. II. Numerical modelling

In Part I the bubble inflation test was used to measure the stress-strain relationship of dough. A large disagreement was found between the stress-strain curve based on experimental data and the curve derived from Bloksma's analytical model. In Part II, a numerical simulation of the bubble inflation test is performed using Finite Element Analysis, in order to obtain further information regarding the accuracy of the analytical predictions. A hyperelastic model is assumed for the dough, with a strain energy potential described by the compressible form of the Mooney-Rivlin model. Four cases were investigated, corresponding to various combinations of material parameters of the Mooney-Rivlin model. The numerical results reinforce the conclusions drawn in Part I of the study, specifically that Bloksma's analysis of the bubble inflation could lead to large errors in the stress-strain curve. It was further concluded that the accuracy of the analysis was dependent on the material properties. For a neo-Hookeian material, the analysis leads to accurate results. This is because, for this material, all the assumptions made in the analysis regarding the bubble shape, the material's incompressibility and the bubble wall thickness distribution are accurate.