Metabolomics on integrated circuit

We have demonstrated a chip-based diagnostics tool for the quantification of metabolites, using specific enzymes, to study enzyme kinetics and calculate the Michaelis-Menten constant. An array of 256×256 ion-sensitive field effect transistors (ISFETs) fabricated in a complementary metal oxide semiconductor (CMOS) process is used for this prototype. We have used hexokinase enzyme reaction on the ISFET CMOS chip with glucose concentration in the physiological range of 0.05 mM – 231 mM and successfully studied the enzyme kinetics of hexokinase in detail. This will promote future research towards multiplexing enzyme-based metabolite quantification on a single chip, ultimately opening a pathway towards a personal metabolome machine

Concentration and mass dependence of transport coefficients and correlation functions in binary mixtures with high mass-asymmetry

Correlation functions and transport coefficients of self-diffusion and shear viscosity of a binary Lennard-Jones mixture with components differing only in their particle mass are studied up to high values of the mass ratio $\mu$, including the limiting case $\mu=\infty$, for different mole fractions $x$. Within a large range of $x$ and $\mu$ the product of the diffusion coefficient of the heavy species $D_{2}$ and the total shear viscosity of the mixture $\eta_{m}$ is found to remain constant, obeying a generalized Stokes-Einstein relation. At high liquid density, large mass ratios lead to a pronounced cage effect that is observable in the mean square displacement, the velocity autocorrelation function and the van Hove correlation function

Synthesis and biodistribution of immunoconjugates of a human IgM and polymeric drug carriers

The synthesis and purification of radiolabelled immunoconjugates, composed of a human IgM monoclonal antibody directed against an intracellular tumour-associated antigen and either poly (alpha-L-glutamic acid) (PGA) or poly[N5-(2-hydroxyethyl)-L-glutamine] (PHEG) is described. Coupling of polymers to the antibody was performed through disulfide bond formation involving a single thiol group at the C-terminus of the polymer chain and 2-pyridyldisulfide groups introduced onto the antibody. The antibody was iodinated with 131I before conjugation. The polymers contained tyrosinamide in a low degree of substitution and were radiolabelled with 125I. 125I-labelled PGA and PHEG were found to be stable for at least 3 days in murine and human plasma. The biodistribution in mice of the doubly labelled immunoconjugates was studied and was compared with the pharmacokinetics of the individual components.\ud \ud PHEG showed a relatively slow blood clearance, the half-life being approximately 10 h with low uptake in liver, kidneys and spleen. PGA was rapidly cleared from the circulation and was significantly taken up in liver, kidneys and spleen. The biodistribution of both immunoconjugates was indistinguishable from that of the IgM proper, with plasma half-lives of approximately 6 h, indicating that the pharmacokinetic properties of the immunoconjugates are largely determined by the antibody part

A high-order finite volume method for Maxwell's equations in heterogeneous and time-varying media

We develop a finite volume method for Maxwell's equations in materials whose electromagnetic properties vary in space and time. We investigate both conservative and non-conservative numerical formulations. High-order methods accurately resolve fine structures that develop due to the varying material properties. Numerical examples demonstrate the effectiveness of the proposed method in handling temporal variation and its efficiency relative to traditional 2nd-order FDTD.Comment: 15 pages, 8 figure

Transport properties of dense dissipitive hard-sphere fluids for arbitrary energy loss models

The revised Enskog approximation for a fluid of hard spheres which lose energy upon collision is discussed for the case that the energy is lost from the normal component of the velocity at collision but is otherwise arbitrary. Granular fluids with a velocity-dependent coefficient of restitution are an important special case covered by this model. A normal solution to the Enskog equation is developed using the Chapman-Enskog expansion. The lowest order solution describes the general homogeneous cooling state and a generating function formalism is introduced for the determination of the distribution function. The first order solution, evaluated in the lowest Sonine approximation, provides estimates for the transport coefficients for the Navier-Stokes hydrodynamic description. All calculations are performed in an arbitrary number of dimensions.Comment: 27 pages + 1 figur

Structural role of the tyrosine residues of cytochrome c

The tertiary structures of horse, tuna, Neurospora crassa, horse [Hse65,Leu67]- and horse [Hse65,Leu74]-cytochromes c were studied with high-resolution 1H n.m.r. spectroscopy. The amino acid sequences of these proteins differ at position 46, which is occupied by phenylalanine in the horse proteins but by tyrosine in the remaining two, and at positions 67, 74 and 97, which are all occupied by tyrosine residues in horse and tuna cytochrome c but in the other proteins are substituted by phenylalanine or leucine, though there is only one such substitution per protein. The various aromatic-amino-acid substitutions do not seriously affect the protein structure

Sound-propagation gap in fluid mixtures

We discuss the behavior of the extended sound modes of a dense binary hard-sphere mixture. In a dense simple hard-sphere fluid the Enskog theory predicts a gap in the sound propagation at large wave vectors. In a binary mixture the gap is only present for low concentrations of one of the two species. At intermediate concentrations sound modes are always propagating. This behavior is not affected by the mass difference of the two species, but it only depends on the packing fractions. The gap is absent when the packing fractions are comparable and the mixture structurally resembles a metallic glass.Comment: Published; withdrawn since ordering in archive gives misleading impression of new publicatio

Reply to the Comment by B. Andresen

All the comments made by Andresen's comments are replied and are shown not to be pertinent. The original discussions [ABE S., Europhys. Lett. 90 (2010) 50004] about the absence of nonextensive statistical mechanics with q-entropies for classical continuous systems are reinforced.Comment: 5 pages. This is Reply to B. Andresen's Comment on the paper entitled "Essential discreteness in generalized thermostatistics with non-logarithmic entropy", Europhys. Lett. 90 (2010) 5000

Escort mean values and the characterization of power-law-decaying probability densities

Escort mean values (or $q$-moments) constitute useful theoretical tools for describing basic features of some probability densities such as those which asymptotically decay like {\it power laws}. They naturally appear in the study of many complex dynamical systems, particularly those obeying nonextensive statistical mechanics, a current generalization of the Boltzmann-Gibbs theory. They recover standard mean values (or moments) for $q=1$. Here we discuss the characterization of a (non-negative) probability density by a suitable set of all its escort mean values together with the set of all associated normalizing quantities, provided that all of them converge. This opens the door to a natural extension of the well known characterization, for the $q=1$ instance, of a distribution in terms of the standard moments, provided that {\it all} of them have {\it finite} values. This question would be specially relevant in connection with probability densities having {\it divergent} values for all nonvanishing standard moments higher than a given one (e.g., probability densities asymptotically decaying as power-laws), for which the standard approach is not applicable. The Cauchy-Lorentz distribution, whose second and higher even order moments diverge, constitutes a simple illustration of the interest of this investigation. In this context, we also address some mathematical subtleties with the aim of clarifying some aspects of an interesting non-linear generalization of the Fourier Transform, namely, the so-called $q$-Fourier Transform.Comment: 20 pages (2 Appendices have been added

Essay: Making the most of recent advances in freshwater mussel propagation and restoration

Propagating and releasing freshwater mussels (Unionida) into the wild can contribute substantially to conservation and perhaps ecosystem restoration, but poorly conceived projects can waste money and public good will, and harm mussel populations and ecosystems. Moving from vague, emotional reactions about mussel restoration to more rigorous discussions and analyses can help focus efforts to where they do the most good. We suggest that: (i) projects to restore mussels for conservation goals to sites where known environmental problems have been eliminated or mitigated have good prospects for success; (ii) projects to restore mussels for conservation goals to sites where known environmental problems have not been eliminated or mitigated have poor prospects for success; (iii) projects to restore mussels for conservation goals to sites in the common situation in which the status of environmental problems is unknown have unknown prospects for success, but may be valuable as scientific experiments, if project performance is monitored properly; (iv) the value of population augmentation as a conservation tool is uncertain, and needs better theoretical and empirical analysis; (v) assisted migration of mussels as a conservation tool is controversial, and should be discussed thoroughly before we reach crises in which it is rejected or carried out carelessly; (vi) projects to restore ecosystem services face more stringent criteria for success than conservation projects, and some such projects being discussed seem unlikely to succeed. Monitoring data on how restoration projects perform typically are inadequately collected, reported, disseminated, and used to improve practice. This could be improved by setting up a clearinghouse to collect, hold, and disseminate data; providing training to restorationists; and opening conversations between restorationists and data managers and statisticians.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149722/1/csp253.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149722/2/csp253_am.pd