Paper‐Based Electrical Respiration Sensor

Current methods of monitoring breathing require cumbersome, inconvenient, and often expensive devices; this requirement sets practical limitations on the frequency and duration of measurements. This article describes a paper‐based moisture sensor that uses the hygroscopic character of paper (i.e. the ability of paper to adsorb water reversibly from the surrounding environment) to measure patterns and rate of respiration by converting the changes in humidity caused by cycles of inhalation and exhalation to electrical signals. The changing level of humidity that occurs in a cycle causes a corresponding change in the ionic conductivity of the sensor, which can be measured electrically. By combining the paper sensor with conventional electronics, data concerning respiration can be transmitted to a nearby smartphone or tablet computer for post‐processing, and subsequently to a cloud server. This means of sensing provides a new, practical method of recording and analyzing patterns of breathing.     

Transparent Aluminium Oxide Coatings of Polymer Brushes

A novel method for the preparation of transparent Al₂O₃ coatings of polymers is presented. An environmental‐friendly sol–gel method is employed, which implies mild conditions and low costs. A thermoresponsive brush is chosen as a model surface. X‐ray photoelectron spectroscopy is used to characterize the samples during the conversion of the precursor Al(OH)₃ into oxide and to prove the mildness of the protocol. The study evidences a relation between lateral homogeneity of alumina and the wettability of the polymer surface by the precursor solution, while morphology and elasticity are dominated by the polymer properties. The study of the swelling behavior of the underneath brush reveals the absence of water uptake, proving the impermeability of the alumina layer. The broad chemical and structural variety of polymers, combined with the robustness of transparent alumina films, makes these composites promising as biomedical implants, protective sheets and components for electric and optical devices.     

Identification of the Key Enzyme of Roseoflavin Biosynthesis

The bacteria Streptomyces davawensis and Streptomyces cinnabarinus produce roseoflavin, the only known natural riboflavin (vitamin B₂) analogue with antibiotic activity. Roseoflavin can be considered a natural antimetabolite and has been postulated to be biosynthesized from riboflavin via the key intermediate 8‐demethyl‐8‐aminoriboflavin (AF). The required site‐specific substitution of one of the methyl groups on the dimethylbenzene ring of riboflavin by an amino group (to give AF) is challenging. The pathway from riboflavin to AF has remained elusive, and the corresponding enzyme/s was/were unknown. Herein, we show by systematic gene deletion, heterologous gene expression, and biochemical studies that the enzyme specified by the gene BN159_7989 from S. davawensis is able to carry out a whole set of chemical reactions starting from riboflavin‐5′‐phosphate to give the final product 8‐demethyl‐8‐aminoriboflavin‐5′‐phosphate (AFP).     

Apoptosis mechanisms related to the increased sensitivity of Jurkat T-cells vs A431 epidermoid cells to photodynamic therapy with the phthalocyanine Pc 4

To examine the clinical applicability of Pc 4, a promising second-generation photosensitizer, for the photodynamic treatment of lymphocyte-mediated skin diseases, we studied the A431 and Jurkat cell lines, commonly used as surrogates for human keratinocyte-derived carcinomas and lymphocytes, respectively. As revealed by ethyl acetate extraction and absorption spectrophotometry, uptake of Pc 4 into the two cell lines was linear with Pc 4 concentration and similar on a per cell basis but greater in Jurkat cells on a per mass basis. Flow cytometry showed that uptake was linear at low doses; variations in the dose-response for uptake measured by fluorescence supported differential aggregation of Pc 4 in the two cell types. As detected by confocal microscopy, Pc 4 localized to mitochondria and endoplasmic reticulum in both cell lines. Jurkat cells were much more sensitive to the lethal effects of phthalocyanine photodynamic therapy (Pc 4-PDT) than were A431 cells, as measured by a tetrazolium dye reduction assay, and more readily underwent morphological apoptosis. In a search for molecular factors to explain the greater photosensitivity of Jurkat cells, the fate of important Bcl-2 family members was monitored. Jurkat cells were more sensitive to the induction of immediate photodamage to Bcl-2, but the difference was insufficient to account fully for their greater sensitivity. The antiapoptotic protein Mcl-1 was extensively cleaved in a dose- and caspase-dependent manner in Jurkat, but not in A431, cells exposed to Pc 4-PDT. Thus, the greater killing by Pc 4-PDT in Jurkat compared with A431 cells correlated with greater Bcl-2 photodamage and more strongly to the more extensive Mcl-1 degradation. Pc 4-PDT may offer therapeutic advantages in targeting inflammatory cells over normal keratinocytes in the treatment of T-cell-mediated skin diseases, such as cutaneous lymphomas, dermatitis, lichenoid tissue reactions and psoriasis, and it will be instructive to evaluate the role of Bcl-2 family proteins, especially Mcl-1, in the therapeutic response.     

Alkali metal reductions of organic molecules: why mediated electron transfer from lithium is faster than direct reduction

Lithium metal reductions are widely employed in organic synthesis, where it is common to employ a "mediator" to speed up the electron transfer kinetics. We present experimental data for the electrode kinetics of the reduction of the most common mediator, 4,4'-di-tert-butyl-1,1'-biphenyl (DBB) in tetrahydrofuran (THF) over a range of temperatures. Using corresponding data for the oxidation of lithium we present quantitative estimates of the kinetic advantage for the use of DBB as a mediator in lithium reductions, over, in particular, direct reduction using lithium metal.     

An improved relaxed complex scheme for receptor flexibility in computer-aided drug design

The interactions among associating (macro)molecules are dynamic, which adds to the complexity of molecular recognition. While ligand flexibility is well accounted for in computational drug design, the effective inclusion of receptor flexibility remains an important challenge. The relaxed complex scheme (RCS) is a promising computational methodology that combines the advantages of docking algorithms with dynamic structural information provided by molecular dynamics (MD) simulations, therefore explicitly accounting for the flexibility of both the receptor and the docked ligands. Here, we briefly review the RCS and discuss new extensions and improvements of this methodology in the context of ligand binding to two example targets: kinetoplastid RNA editing ligase 1 and the W191G cavity mutant of cytochrome c peroxidase. The RCS improvements include its extension to virtual screening, more rigorous characterization of local and global binding effects, and methods to improve its computational efficiency by reducing the receptor ensemble to a representative set of configurations. The choice of receptor ensemble, its influence on the predictive power of RCS, and the current limitations for an accurate treatment of the solvent contributions are also briefly discussed. Finally, we outline potential methodological improvements that we anticipate will assist future development. Rommie E. Amaro and Riccardo Baron contributed equally to this work.     

Determination of underivatized amino acid delta(13)C by liquid chromatography/isotope ratio mass spectrometry for nutritional studies: the effect of dietary non-essential amino acid profile on the isotopic signature of individual amino acids in fish

This study provides data for the effect of dietary non-essential amino acid composition on the delta(13)C values of individual amino acids in rainbow trout (Oncorhynchus mykiss) using liquid chromatography coupled to isotope ratio mass spectrometry (LC/IRMS). In this experiment, trout were reared either on a control diet or on three experimental diets, differing in the composition of non-essential/conditionally essential amino acids, for a period of 6 weeks. The control diet was a commercial trout starter feed with fish meal as the main protein source. The experimental diets contained no protein, only synthetic amino acids. Diet 1 resembled the composition of fish meal in both essential and non-essential amino acids, Diet 2 had all essential amino acids, but cysteine, glycine, proline and tyrosine were replaced by the corresponding amounts of their precursors, and in Diet 3 all non-essential amino acids were replaced by glutamate. LC/IRMS was used for the determination of delta(13)C values of individual amino acids from diets and tissues without derivatization. Diet affected the delta(13)C of individual amino acids in fish. For fish on Diets 1-3 amino acid delta(13)C values showed a similar trend: phenylalanine showed very little change from diet to body tissue. Arginine, lysine, tyrosine and proline showed strong depletion from diet to body tissue and glycine, alanine, aspartate and serine all showed variable but strong enrichment in (13)C. Improvements are necessary before all amino acid delta(13)C values can be determined; however, this study demonstrates that measuring amino acid isotopic signatures by LC/IRMS is a promising new technique for nutritional physiologists.     

Natural wax constituents of a supercritical fluid CO<Subscript>2</Subscript> extract from quince (<Emphasis Type="Italic">Cydonia oblonga</Emphasis> Mill.) pomace

The chemical constituents of a lipophilic extract from quince (Cydonia oblonga Mill.), obtained by supercritical fluid CO₂ extraction of the dried fruit pomace were investigated. Solvent partition of quince wax with n-hexane or acetone yielded an insoluble (crystalline) and a soluble (oily) fraction. Both fractions were analyzed separately using gas chromatography/mass spectrometry (GC/MS). The insoluble fraction consisted of saturated n-aldehydes, n-alcohols and free n-alkanoic acids of carbon chain lengths between 22 and 32, with carbon chain lengths of 26 and 28 dominating. Also odd-numbered unbranched hydrocarbons, mainly C27, C29 and C31, were detected particularly in the acetone-insoluble fraction (total, 15.8%). By means of vacuum liquid chromatography, triterpenoic acids were separated from the hexane-insoluble matter and identified as a mixture of ursolic, oleanolic and betulinic acids. The major constituents of the hexane-soluble fraction were glycerides of linoleic [Δ^9,12, 18:2] and oleic [Δ⁹, 18:1] acids, accompanied by free linoleic, oleic and palmitic acids (C16). Moreover β-sitosterol, Δ⁵-avenasterol as well as trace amounts of other sterols were assigned. Finally the carotenoids phytoene and phytofluene were identified and quantified by UV/vis and high-performance liquid chromatography/MS techniques, yielding 1.0 and 0.3% of the quince wax, respectively. It is anticipated that the complex of lipid constituents from quince wax may exert interesting biological activities, the elucidation of which awaits further studies. Figure Quince fruits and some of their fruit wax constituents. Clockwise (starting at one o’clock): structure formulas of Δ5-avenasterol, linoleic acid, oleanolic acid, and phytofluen. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Complex DNA binding kinetics resolved by combined circular dichroism and luminescence analysis

We recently reported that ruthenium complexes, with general structure [mu-bidppz(bipy)4Ru2](4+) (B) or [mu-bidppz(phen)4Ru2](4+) (P) (bidppz=11,11'-bi(dipyrido[3,2- a:2',3'-c]phenazinyl)), show extreme kinetic selectivity for long AT tracts over mixed-sequence calf thymus DNA (ct-DNA), a selectivity that also varies markedly with the size (between B and P) and sense of chirality of the complex. Earlier studies, exploiting the great increase in luminescence intensity when the compound intercalates, have yielded complex kinetics indicating the presence of both first- and second-order processes. Even with a homogeneous DNA sequence, such as poly(dAdT)2, the luminescence kinetics generally requires more than a single exponential for a satisfactory fit. We here reveal that at least part of the complexity is a result of the extreme sensitivity of the effective quantum yield of the complexes, so that the luminescence trajectories also reflect subtle variations in the environment and binding geometry that the complex is sampling on its path to its final binding site. By monitoring the rearrangement process using circular dichroism (CD), we show that threading of both enantiomers of B and P into poly(dAdT)2 is effectively a monoexponential process, as expected if the compounds are not affecting each other during the intercalation process. Thus, the complex luminescence trajectories may be explained by slow relaxations in the binding geometry (DNA conformation) and associated changes in the environment of the entering complexes. To further disentangle the intriguing features of the threading intercalation kinetics, and how they may depend on the flexibility and size of the ruthenium complexes, we have also designed and studied two new ruthenium complexes, [mu-dtpf(phen)4Ru2](4+) (F) (dtpf=4,5,9,12,16,17,21,25-octaaza-23 H-ditriphenyleno[2,3-b:2,3-h]fluorene), in which the bridging ligand is made totally rigid, and [mu-bidppz([12]aneS4) 2Ru2](4+) (S), which has less bulky, nonaromatic ancillary ligands. The threading of F into poly(dAdT)2, also found to be a monoexponential process, is about 3 times slower than for P, indicating that the flexibility of the bridging ligand is an important factor for the intercalation rate. Surprisingly, in contrast to all other compounds, S requires two exponentials to fit its binding kinetics as monitored by CD. Also surprisingly, in view of the smaller steric bulk, even the fastest phase is roughly 2 times slower for S than for B and P. Thus, not only the size of the ancillary ligand but also other properties that can influence the energy landscape of the threading path are rate-determining factors. With mixed-sequence ct-DNA, threading of B and that of P are both multiphasic processes when monitored with CD as well as with luminescence. The rate constants for threading into ct-DNA show much larger variations between complexes than for poly(dAdT)2, confirming earlier results based on luminescence data.