Plasmophore sensitized imaging of ammonia release from biological tissues using optodes

A plasmophore sensitized optode was developed for imaging ammonia (NH(3)) concentrations in muscle tissues. The developed ammonia sensor and an equivalent non plasmophore version of the sensor were tested side by side to compare their limit of detection, dynamic range, reversibility and overall imaging quality. Bio-degradation patterns of ammonia release from lean porcine skeletal muscle were studied over a period of 11 days. We demonstrate that ammonia concentrations ranging from 10nM can be quantified reversibly with an optical resolution of 127 μm in a sample area of 25 mm × 35 mm. The plasmophore ammonia optode showed improved reversibility, less false pixels and a 2 nM ammonia detection limit compared to 200 nM for the non-plasmophore sensor. Main principles of the sensing mechanism include ammonia transfer over a gas permeable film, ammonia protonation, nonactin facilitated merocyanine-ammonium coextraction and plasmophore enhancement. The vast signal improvement is suggested to rely on solvatochroism, nanoparticle scattering and plasmonic interactions that are utilized constructively in a fluorescence ratio. In addition to fundamental medicinal and biological research applications in tissue physiology, reversible ammonia quantification will be possible for a majority of demanding imaging and non imaging applications such as monitoring of low ammonia background concentrations in air and non-invasive medicinal diagnosis through medical breath or saliva analysis. The nanoparticle doped sensor constitutes a highly competitive technique for ammonia sensing in complex matrixes and the general sensing scheme offers new possibilities for the development of artificial optical noses and tongues.     

Monitoring allostery in D2O: a necessary control in studies using hydrogen/deuterium exchange to characterize allosteric regulation

There is currently a renewed focus aimed at understanding allosteric mechanisms at atomic resolution. This current interest seeks to understand how both changes in protein conformations and changes in protein dynamics contribute to relaying an allosteric signal between two ligand binding sites on a protein (e.g., active and allosteric sites). Both nuclear magnetic resonance (NMR), by monitoring protein dynamics directly, and hydrogen/deuterium exchange, by monitoring solvent accessibility of backbone amides, offer insights into protein dynamics. Unfortunately, many allosteric proteins exceed the size limitations of standard NMR techniques. Although hydrogen/deuterium exchange as detected by mass spectrometry (H/DX-MS) offers an alternative evaluation method, any application of hydrogen/deuterium exchange requires that the property being measured functions in both H₂O and D₂O. Due to the promising future H/DX-MS has in the evaluation of allosteric mechanisms in large proteins, we demonstrate an evaluation of allosteric regulation in D₂O. Exemplified using phenylalanine inhibition of rabbit muscle pyruvate kinase, we find that binding of the inhibitor is greatly reduced in D₂O, but the effector continues to elicit an allosteric response.     

Algebras of Symmetric Holomorphic Functions on lp

The authors study the algebra of uniformly continuous holomorphicsymmetric functions on the ball of l_p, investigating in particularthe spectrum of such algebras. To do so, they examine the algebraof symmetric polynomials on l_p-spaces, as well as finitely generatedsymmetric algebras of holomorphic functions. Such symmetricpolynomials determine the points in l_p up to a permutation.     

Left–right and dynamic correlation

Within density functional theory, it is natural to separate the correlation energy into two parts: left–right correlation and dynamic correlation. Left–right correlation arises from the exchange part of functionals, and dynamic correlation arises from the correlation part of functionals. We examine the nature of these correlation energies as molecules are distorted. We observe that such a natural separation is not possible using the methods of quantum chemistry. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Convex vector lattices and l-algebras

For A an Archimedean Riesz space (=vector lattice) with distinguished positive weak unit e_A, we have the Yosida representation  as a Riesz space in D(X_A), the lattice of extended real valued functions on the space of e_A-maximal ideas. This note is about those A for which  is a convex subset of D(X_A); we call such A “convex”.Convex Riesz spaces arise from the general issue of embedding as a Riesz ideal, from consideration of uniform- and order-completeness, and from some problems involving comparison of maximal ideal spaces (which we won't discuss here; see [10]).The main results here are: (2.4) A is convex iff A is contained as a Riesz ideal in a uniformly complete Φ-algebra B with identity e_A. (3.1) Any A has a convex reflection (i.e., embeds into a convex B with a universal mapping property for Riesz homomorphisms; moreover, the embedding is epic and large).     

The Bishop-Phelps-Bollobás theorem for operators

We prove the Bishop-Phelps-Bollobás theorem for operators from an arbitrary Banach space X into a Banach space Y whenever the range space has property β of Lindenstrauss. We also characterize those Banach spaces Y for which the Bishop-Phelps-Bollobás theorem holds for operators from ?₁ into Y. Several examples of classes of such spaces are provided. For instance, the Bishop-Phelps-Bollobás theorem holds when the range space is finite-dimensional, an L₁(μ)-space for a σ-finite measure μ, a C(K)-space for a compact Hausdorff space K, or a uniformly convex Banach space.     

Uniform factorization for compact sets of operators

We prove a factorization result for relatively compact subsets of compact operators using the Bartle and Graves Selection Theorem, a characterization of relatively compact subsets of tensor products due to Grothendieck, and results of Figiel and Johnson on factorization of compact operators. A further proof, essentially based on the Banach-Dieudonné Theorem, is included. Our methods enable us to give an easier proof of a result of W.H. Graves and W.M. Ruess.