Preprocessing Strategies for Sparse Infrared Spectroscopy: A Case Study on Cartilage Diagnostics

The aim of the study was to optimize preprocessing of sparse infrared spectral data. The sparse data were obtained by reducing broadband Fourier transform infrared attenuated total reflectance spectra of bovine and human cartilage, as well as of simulated spectral data, comprising several thousand spectral variables into datasets comprising only seven spectral variables. Different preprocessing approaches were compared, including simple baseline correction and normalization procedures, and model-based preprocessing, such as multiplicative signal correction (MSC). The optimal preprocessing was selected based on the quality of classification models established by partial least squares discriminant analysis for discriminating healthy and damaged cartilage samples. The best results for the sparse data were obtained by preprocessing using a baseline offset correction at 1800 cm⁻¹, followed by peak normalization at 850 cm⁻¹ and preprocessing by MSC.     

Early Main Group Metal Catalysis: How Important is the Metal?

Organocalcium compounds have been reported as efficient catalysts for various alkene transformations. In contrast to transition metal catalysis, the alkenes are not activated by metal–alkene orbital interactions. Instead it is proposed that alkene activation proceeds through an electrostatic interaction with a Lewis acidic Ca²⁺. The role of the metal was evaluated by a study using the metal‐free catalysts: [Ph₂N^?][Me₄N⁺] and [Ph₃C^?][Me₄N⁺]. These “naked” amides and carbanions can act as catalysts in the conversion of activated double bonds (C?O and C?N) in the hydroamination of Ar? N?C?O and R? N?C?N? R (R=alkyl) by Ph₂NH. For the intramolecular hydroamination of unactivated C?C bonds in H₂C?CHCH₂CPh₂CH₂NH₂ the presence of a metal cation is crucial. A new type of hybrid catalyst consisting of a strong organic Schwesinger base and a simple metal salt can act as catalyst for the intramolecular alkene hydroamination. The influence of the cation in catalysis is further evaluated by a DFT study.     

Computational modeling of MR flow imaging by the lattice Boltzmann method and Bloch equation

In this work, a computational model of magnetic resonance (MR) flow imaging is proposed. The first model component provides fluid dynamics maps by applying the lattice Boltzmann method. The second one uses the flow maps and couples MR imaging (MRI) modeling with a new magnetization transport algorithm based on the Eulerian coordinate approach. MRI modeling is based on the discrete time solution of the Bloch equation by analytical local magnetization transformations (exponential scaling and rotations).     

Recognizing Knödel graphs

Knödel graphs form a class of bipartite incident-graph of circulant digraphs. This class has been extensively studied for the purpose of fast communications in networks, and it has deserved a lot of attention in this context. In this paper, we show that there exists an O(n log⁵ n)-time algorithm to recognize Knödel graphs of order 2n. The algorithm is based on a characterization of the cycles of length six in these graphs (bipartite incident-graphs of circulant digraphs always have cycles of length six). A consequence of our result is that the circulant digraphs whose chords are the power of two minus one can be recognized in O(n log⁵ n) time.     

INHIBITION OF OXYGEN EVOLUTION IN CHLOROPLAST PHOTOSYSTEM II BY THE PROTEIN-MODIFYING AGENT TETRANITROMETHANE

Abstract— The protein-modifying agent tetranitromethane (TNM) reacts with tyrosine residues and -SH groups. It was found to inhibit photo synthetic electron transport on the water splitting side of photosystem II (P. V. Sane and U. Johanningmeier, Z. Naturforsch. 35c, 293–297, 1979). In the present work the inhibition by TNM is studied in detail using photosystem II submembrane fractions. It is shown that the action of TNM with membrane-bound proteins could imply the modification of tyrosine residues. At concentrations below 30 μ M and with short incubation periods (<2 min), TNM produces the release of the extrinsic polypeptides involved in the stabilization of the water-splitting complex, this being correlated with inhibition of electron transport at a site prior to H₂O₂ electron donation even though the inhibition cannot be prevented by the addition of Cl or Ca²⁺, which are known cofactors for oxygen evolution. As the incubation period or the concentration of TNM is increased, photosynthetic pigments are bleached, starting with aggregates absorbing at relatively long wavelengths. The inhibition by low concentrations of TNM differs from the effect of most of the previously reported inhibitors acting at the oxygen-evolving complex of photosystem II.     

Enzyme‐Mediated Modification of Single‐Domain Antibodies for Imaging Modalities with Different Characteristics

Antibodies are currently the fastest‐growing class of therapeutics. Although naked antibodies have proven valuable as pharmaceutical agents, they have some limitations, such as low tissue penetration and a long circulatory half‐life. They have been conjugated to toxic payloads, PEGs, or radioisotopes to increase and optimize their therapeutic efficacy. Although nonspecific conjugation is suitable for most in vitro applications, it has become evident that site specifically modified antibodies may have advantages for in vivo applications. Herein we describe a novel approach in which the antibody fragment is tagged with two handles: one for the introduction of a fluorophore or ¹⁸F isotope, and the second for further modification of the fragment with a PEG moiety or a second antibody fragment to tune its circulatory half‐life or its avidity. Such constructs, which recognize Class II MHC products and CD11b, showed high avidity and specificity. They were used to image cancers and could detect small tumors.     

Infrared spectroscopy studies of structure and orientation in clay-reinforced polyamide-6 nanocomposites

Infrared (IR) spectroscopy was used to study the surface (by means of external reflection) and the bulk (by means of transmission measurements on microtomed slices) of specimens obtained by injection moulding of a commercial polyamide-6 clay-based nanocomposite material (NCH = nylon clay hybrid) at different mould temperatures and with different part geometries. Comparisons were made with equivalent non-reinforced polymer (PA-6). For the PA-6, the mould temperature influences the crystalline structure, with the γ phase predominating at 50°C and the α phase at 80°C. However, in the NCH material the ( phase is favoured, even at 80°C. In all cases the crystallinity increases on going from the surface to the core. The polymer chains are oriented in the flow direction, and the orientation is higher for parts with more elongated shapes. It does not vary greatly across the part thickness, except for a thin surface layer, where it is significantly higher. Both at the surface and in the bulk, the crystalline phase orientation is higher for the NCH than for the PA-6.     

Selected drugs in solid matrices: a review of environmental determination, occurrence and properties of principal substances

After intake, drugs absorbed by human or animal organisms are subject to metabolic reactions, such as hydroxylation, cleavage or glucuronation. However, a significant amount of the original or the metabolized substance leaves the organism via urine or feces. Thanks to improvements in analytical chemistry, many pharmaceutical compounds and endocrine disrupters are more easily detected in the surface-water and waste-water environmental compartments, at ppb concentrations.But what contaminates our solid environmental matrices? These substances can be eliminated by sorption or biodegradation but, at present, there is not enough data to allow evaluation of the behavior of the substances through the solid compartment, such as soil, sludge and bio-waste.This article provides an overview of the occurrence of pharmaceutical compounds in solid matrices on the basis of the quantities used, their physico-chemical properties and data from literature indicating the potential of the drug to persist in sediment, soil or sludge.     

FURTHER CHARACTERIZATION OF ANESTHETIC-TREATED PURPLE MEMBRANES

Abstract— The absorption maximum of bacteriorhodopsin is shifted from 568 nm to 480 nm when halogenated volatile anesthetics (enflurane; halothane) are added to purple membranes. Analysis of the rate of formation of this new species upon addition of the anesthetic and of the back-formation of native bacteriorhodopsin upon its removal indicate that in purple membranes, the dark-adapted chromophore is much less reactive than its light-adapted counterpart. Lipid-soluble molecules thus have a lower accessibility to the dark-adapted chromophore.
In addition, activity of the 480 nm bacteriorhodopsin was investigated. Flash and steady-state photolysis experiments reveal that this blue shifted chromophore has full photochemical activity. It has a meta-intermediate absorbing maximally at 380 nm. The photocycle ofBR–480 is mainly characterized by a slow decay of the "O" intermediate, enabling the direct observation of the branching reaction between the "M" intermediate and the parentBR–480 pigment.