DOSE-RESPONSE OF CHRONIC ULTRAVIOLET EXPOSURE ON EPIDERMAL FORWARD SCATTERING-ABSORPTION IN SK-1 HAIRLESS MOUSE SKIN

This work provides a dose-response model of UV-induced epidermal-stratum corneum thickening induced by irradiation at wavelength lambda. This model assumes that photobiochemical reaction(s) can give rise to hyperplasia in a manner which is predictable from a simple photochemical kinetic scheme. In this work, we derive an equation which predicts an approximately linear relationship between the logarithm of the increase in optical skin thickening measured at 320 nm (delta OD320) and total cumulative dose (DT) seen by the target cells in or near the basal layer. For each excitation wavelength lambda, the slope R(lambda) of the log delta OD320 vs DT plot is proportional to epsilon(lambda) phi rx, where epsilon(lambda) is the extinction coefficient for the target chromophore at excitation wavelength, and phi rx is the quantum yield for the photochemical reaction(s) leading to hyperplasia. Our data previously obtained from irradiation of SK-1 hairless mice with "monochromatic" UV wavebands at 280, 290, 300, 307 and 313 nm (Menter et al., 1988, Photochem. Photobiol. 47, 225-260.) and data from Sterenborg and van der Leun at 254 and 313 nm (1988, Photodermatology 5, 71-82) are in good agreement with this model, except for 254 and 280 nm excitation, which are greatly attenuated by epidermis-stratum corneum. For excitation at the latter wavelengths, "dark" regressive processes successfully compete with the "light" reaction(s) which lead to (pre)cancerous lesion. This difficulty notwithstanding, the "intrinsic" action spectrum for hyperplasia derived from these measurements indicates that the target chromophore preferentially absorbs in the UV-C region.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pathogen detection using engineered bacteriophages

Bacteriophages, or phages, are bacterial viruses that can infect a broad or narrow range of host organisms. Knowing the host range of a phage allows it to be exploited in targeting various pathogens. Applying phages for the identification of microorganisms related to food and waterborne pathogens and pathogens of clinical significance to humans and animals has a long history, and there has to some extent been a recent revival in these applications as phages have become more extensively integrated into novel detection, identification, and monitoring technologies. Biotechnological and genetic engineering strategies applied to phages are responsible for some of these new methods, but even natural unmodified phages are widely applicable when paired with appropriate innovative detector platforms. This review highlights the use of phages as pathogen detector interfaces to provide the reader with an up-to-date inventory of phage-based biodetection strategies.     

Isobaric vapor–liquid equilibria for the quaternary reactive system: Ethanol + water + ethyl lactate + lactic acid at 101.33 kPa

Isobaric vapor–liquid equilibrium (VLE) data of the reactive quaternary system ethanol (1) + water (2) + ethyl lactate (3) + lactic acid (4) have been determined experimentally. Additionally, the reaction equilibrium constant was calculated for each VLE experimental data. The experimental VLE data were correlated using the UNIQUAC equation to describe the chemical and phase equilibria simultaneously. For some of the non-reactive binary systems, UNIQUAC binary interaction parameters were obtained from the literature. The rest of the binary UNIQUAC parameters were obtained by correlating the experimental quaternary VLE data obtained in this work. A maximum pressure azeotrope at high water concentration for the binary reactive system ethyl lactate + water has been calculated.     

Evolutionary divergence of sedoheptulose 7-phosphate cyclases leads to several distinct cyclic products

Sedoheptulose 7-phosphate cyclases are enzymes that utilize the pentose phosphate pathway intermediate, sedoheptulose 7-phosphate, to generate cyclic precursors of many bioactive natural products, such as the antidiabetic drug acarbose, the crop protectant validamycin, and the natural sunscreens mycosporine-like amino acids. These proteins are phylogenetically related to the dehydroquinate (DHQ) synthases from the shikimate pathway and are part of the more recently recognized superfamily of sugar phosphate cyclases, which includes DHQ synthases, aminoDHQ synthases, and 2-deoxy-scyllo-inosose synthases. Through genome mining and biochemical studies, we identified yet another subset of DHQS-like proteins in the actinomycete Actinosynnema mirum and the myxobacterium Stigmatella aurantiaca DW4/3-1. These enzymes catalyze the conversion of sedoheptulose 7-phosphate to 2-epi-valiolone, which is predicted to be an alternative precursor for aminocyclitol biosynthesis. Comparative bioinformatics and biochemical analyses of these proteins with 2-epi-5-epi-valiolone synthases (EEVS) and desmethyl-4-deoxygadusol synthases (DDGS) provided further insights into their genetic diversity, conserved amino acid sequences, and plausible catalytic mechanisms. The results further highlight the uniquely diverse DHQS-like sugar phosphate cyclases, which may provide new tools for chemoenzymatic, stereospecific synthesis of various cyclic molecules.     

Interaction proteomics of synapse protein complexes

The brain integrates complex types of information, and executes a wide range of physiological and behavioral processes. Trillions of tiny organelles, the synapses, are central to neuronal communication and information processing in the brain. Synaptic transmission involves an intricate network of synaptic proteins that forms the molecular machinery underlying transmitter release, activation, and modulation of transmitter receptors and signal transduction cascades. These processes are dynamically regulated and underlie neuroplasticity, crucial to learning and memory formation. In recent years, interaction proteomics has increasingly been used to elucidate the constituents of synaptic protein complexes. Unlike classic hypothesis-based assays, interaction proteomics detects both known and novel interactors without bias. In this trend article, we focus on the technical aspects of recent proteomics to identify synapse protein complexes, and the complementary methods used to verify the protein–protein interaction. Moreover, we discuss the experimental feasibility of performing global analysis of the synapse protein interactome.     

A new application of imprinted polymers: Speciation of organotin compounds

Molecular imprinting technology has been employed for the first time to prepare a specifically affinity chromatographic stationary phase for speciation purposes. Tributyltin has been chosen as the template molecule and the non-covalent approach has been applied. Three different polymerization methods have been evaluated: (i) a composite material, (ii) a polymer prepared via-Iniferter grafting; (iii) an emulsion polymer. Columns packed with different polymers have been evaluated by liquid chromatography (LC) coupled to inductively coupled plasma mass spectrometry (ICP-MS). The chromatographic conditions as well as the analytical characteristics of the developed method are discussed in this paper. Our findings have shown formation of specific cavities in the grafted Iniferter as well as in the emulsion polymers with the latter achieving resolution of four organotin compounds. Detection limits are similar to those obtained with commercial, but not specific, stationary phases (6 pg for monobutyltin, MBT; 10 pg for both tributyltin, TBT, and triphenyltin, TPhT; and 20 pg for dibutyltin, DBT). The main advantage of this proposed stationary phase is that good recovery is obtained for all species, including MBT. Baseline resolution for TBT and TPhT has also been obtained. The high selectivity of this column prevents matrix interferences. The method has been validated by analyzing two biota reference materials (ERM-CE477 mussel tissue and T-38 oyster tissue).     

Synthetic,Mechanistic, and Theoretical Studies on the Generation of Iridium Hydride Alkylidene and Iridium Hydride Alkene Isomers

Experimental and theoretical studies on equilibria between iridium hydride alkylidene structures, [(Tp^Me2)Ir(H){?C(CH₂R)ArO }] (Tp^Me2=hydrotris(3,5‐dimethylpyrazolyl)borate; R=H, Me; Ar=substituted C₆H₄ group), and their corresponding hydride olefin isomers, [(Tp^Me2)Ir(H){R(H)C? C(H)OAr}], have been carried out. Compounds of these types are obtained either by reaction of the unsaturated fragment [(Tp^Me2)Ir(C₆H₅)₂] with o‐C₆H₄(OH)CH₂R, or with the substituted anisoles 2,6‐Me₂C₆H₃OMe, 2,4,6‐Me₃C₆H₂OMe, and 4‐Br‐2,6‐Me₂C₆H₂OMe. The reactions with the substituted anisoles require not only multiple C? H bond activation but also cleavage of the Me? OAr bond and the reversible formation of a C? C bond (as revealed by ¹³C labeling studies). Equilibria between the two tautomeric structures of these complexes were achieved by prolonged heating at temperatures between 100 and 140 °C, with interconversion of isomeric complexes requiring inversion of the metal configuration, as well as the expected migratory insertion and hydrogen‐elimination reactions. This proposal is supported by a detailed computational exploration of the mechanism at the quantum mechanics (QM) level in the real system. For all compounds investigated, the equilibria favor the alkylidene structure over the olefinic isomer by a factor of between approximately 1 and 25. Calculations demonstrate that the main reason for this preference is the strong Ir–carbene interactions in the carbene isomers, rather than steric destabilization of the olefinic tautomers.