Products of cytochrome P450(BioI) (CYP107H1)-catalyzed oxidation of fatty acids

[reaction: see text] Oxidation of tetradecanoic and hexadecanoic acids by cytochrome P450(BioI) (CYP107H1) produces mainly the 11-, 12-, and 13-hydroxy C(14) fatty acids and the 11- to 15-hydroxy C(16) fatty acids, respectively. In contrast to previous reports, terminal hydroxylation is not observed. The enantiospecificity of fatty acid hydroxylation by P450(BioI) was also determined, and the enzyme was shown to be moderately selective for production of the (R)-alcohols.     

Diagnostic prospects and preclinical development of optical technologies using gold nanostructure contrast agents to boost endogenous tissue contrast

Numerous developments in optical biomedical imaging research utilizing gold nanostructures as contrast agents have advanced beyond basic research towards demonstrating potential as diagnostic tools; some of which are translating into clinical applications. Recent advances in optics, lasers and detection instrumentation along with the extensive, yet developing, knowledge-base in tailoring the optical properties of gold nanostructures has significantly improved the prospect of near-infrared (NIR) optical detection technologies. Of particular interest are optical coherence tomography (OCT), photoacoustic imaging (PAI), multispectral optoacoustic tomography (MSOT), Raman spectroscopy (RS) and surface enhanced spatially offset Raman spectroscopy (SESORS), due to their respective advancements. Here we discuss recent technological developments, as well as provide a prediction of their potential to impact on clinical diagnostics. A brief summary of each techniques'' capability to distinguish abnormal (disease sites) from normal tissues, using endogenous signals alone is presented. We then elaborate on the use of exogenous gold nanostructures as contrast agents providing enhanced performance in the above-mentioned techniques. Finally, we consider the potential of these approaches to further catalyse advances in pre-clinical and clinical optical diagnostic technologies.

Optical biomedical imaging research utilising gold nanostructures as contrast agents has advanced beyond basic science, demonstrating potential in various optical diagnostic tools; some of which are currently translating into clinical applications.     

Excess proton solvation and delocalization in a hydrophilic pocket of the proton conducting polymer membrane nafion

Solvation properties of the hydrated excess proton are studied in a hydrophilic pocket of Nafion 117 through a series of molecular dynamics simulations. The multistate empirical valence bond (MS-EVB) methodology, which enables the delocalization of the excess proton through the Grotthuss hopping mechanism, was employed for one of the excess protons in the simulation cell. Simulations were performed such that "classical" nondissociable hydronium cations and a single excess proton treated with the MS-EVB methodology were at a concentration ratio of 39:1. Two degrees of hydration of the Nafion polymer electrolyte membrane were simulated, each displaying the same marked difference between the solvation structures of the classical versus MS-EVB treated (Grotthuss shuttling) excess proton species. These differences are attributed to the solvent dynamics needed to transfer the cation between the solvent separated and contact pair positions about the sulfonic acid counterion. The results demonstrate that it is generally impossible to describe the low pH conditions in the hydrophilic domains of Nafion without the explicit treatment of Grotthuss delocalization in the underlying molecular dynamics model for the excess protons.     

Conversion of Light into Electricity with Trinuclear Ruthenium Complexes Adsorbed on Textured TiO2 Films

A series of CN-bridged trinuclear Ru complexes of the general structure [RuL₂(μ-(CN)Ru(CN)L₂′)₂] where L is 2,2′-bipyridine-4,4′-dicarboxylic acid and L′ is 2,2′-bipyridine ( 1 )2,2′-bipyridine-4,4′-dicarboxylic acid ( 2 ), 4,4′-dimethyl-2,2′-bipyridine ( 3 ), 4,4′-diphenyl-2,2′-bipyridine ( 4 ), 1,10-phenanthroline ( 5 ), and bathophenanthrolinedisulfonic acid ( 6 ) have been synthesized, and their spectral and electrochemical properties investigated. The two carboxylic functions on the 2,2′-bipyridine ligand L serve as interlocking groups through which the dye is attached at the surface of TiO₂ films having a specific surface texture. The role of these interlocking groups is to provide strong electronic coupling between the π* orbital of the 2,2′-bipyridine and the 3d-wave-function manifold of the conduction band of the TiO₂, allowing the charge injection to proceed at quantum yields close to 100 %. The charge injection and recombination dynamics have been studied with colloidal TiO₂, using laser photolysis technique in conjunction with time-resolved optical spectroscopy. Photocurrent action spectra obtained from photo-electrochemical experiments with these trinuclear complexes cover a very broad range in the visible, making them attractive candidates for solar light harvesting. Monochromatic incident photon-to-current conversion efficiencies are strikingly high exceeding 80% in some cases. Performance characteristics of regenerative cells operating with these trinuclear complexes and ethanolic triiodide/iodide redox electrolyte have been investigated. Optimal results were obtained with complex 1 which gave a fill factor of 75 % and a power conversion efficiency of 11.3% at 520 nm.     

Design and characterization of programmable DNA nanotubes

DNA self-assembly provides a programmable bottom-up approach for the synthesis of complex structures from nanoscale components. Although nanotubes are a fundamental form encountered in tile-based DNA self-assembly, the factors governing tube structure remain poorly understood. Here we report and characterize a new type of nanotube made from DNA double-crossover molecules (DAE-E tiles). Unmodified tubes range from 7 to 20 nm in diameter (4 to 10 tiles in circumference), grow as long as 50 microm with a persistence length of approximately 4 microm, and can be programmed to display a variety of patterns. A survey of modifications (1) confirms the importance of sticky-end stacking, (2) confirms the identity of the inside and outside faces of the tubes, and (3) identifies features of the tiles that profoundly affect the size and morphology of the tubes. Supported by these results, nanotube structure is explained by a simple model based on the geometry and energetics of B-form DNA.     

An analogue system displaying all the important processes of the catalytic cycles involving monooxomolybdenum(VI) and desoxomolybdenum(IV) centers

The mononuclear monooxomolybdenum(VI) complex hydrotris(3,5-dimethyl-1-pyrazolyl)borato(bis-4-ethoxyphenolato)oxomoylybdenum(VI) cation, [LMoVIO(p-OC6H4-OC2H5)2]+, where L- = hydrotris(3,5-dimethyl-1-pyrazolyl)borate, has been synthesized by chemical and electrochemical oxidation from the corresponding neutral oxomolybdenum(V) species, LMoVO(p-OC6H4-OC2H5)2. The molybdenum(VI) species has been characterized by NMR, IR, and resonance Raman spectroscopies, mass spectrometry, and electronic spectroscopy. Acetonitrile solutions of cationic [LMoVIO(p-OC6H4-OC2H5)2]+ react with tertiary phosphines (PR3) to generate phosphineoxide-bound adducts, [LMoIV(OPR3)(p-OC6H4-OC2H5)2]+, which subsequently generate the cationic desoxo species, [LMoIV(p-OC6H4-OC2H5)2]+ and OPR3. In the presence of water and an oxidizing agent the desoxo species generates the monooxomolybdenum(V), LMoVO(p-OC6H4-OC2H5)2, and completes the catalytic cycle. The oxygen atom transfer reaction has been probed by isotope-labeling experiments, vibrational spectroscopies, and mass spectrometry. This study describes an analogue complex that can exhibit all important processes of the catalytic cycle involving monooxomolybdenum(VI) and desoxomolybdenum(IV) centers.     

Solid-phase synthesis of 1-substituted tetrahydroisoquinoline derivatives employing BOC-protected tetrahydroisoquinoline carboxylic acids

Compounds containing the tetrahydroisoquinoline ring system were prepared using solid-supported ester derivatives on a nucleophile-sensitive resin, starting from the corresponding BOC-protected amino acids. The key heterocyclic intermediates were obtained from the Pictet-Spengler reaction between ethyl glyoxylate or methyl 4-formylbenzoate and dopamine or 3-hydroxyphenethylamine. After the resulting amino esters were converted to the BOC derivatives, the phenolic hydroxyl groups were alkylated with a series of alkyl halides to afford the corresponding ethers. Ester hydrolysis afforded the BOC-protected tetrahydroisoquinoline carboxylic acid scaffolds, which were then attached to (4-hydroxyphenyl)sulfide resin (Marshall linker) as the corresponding ester. The BOC group was removed under acidic conditions, and the resulting support-bound amine hydrochlorides were converted to the corresponding amides using a set of carboxylic acids. The support-bound amides were liberated with amines to produce the desired tetrahydroisoquinoline carboxamides. Optimization of the resin loading conditions is described in addition to the identification of impurities observed during the development of the optimum conditions for solid-phase synthesis.     

Water penetration in nylon 6,6: Absorption,desorption, and exchange studied by NMR microscopy

The uptake of water by nylon 6,6 [42DB Adipure (trade name of Dupont Canada Inc.)] at 100°C has been monitored by a combination of one-dimensional proton NMR spectroscopy, relaxation time (T₁ and T₂) measurements and proton microscopic NMR imaging techniques. The relaxation times of the water absorbed into the nylon matrix are very short at room temperature, (T₂ < 1 ms and T₁ ≈ 1 s) indicating that the water is located in a highly restricted environment and suggesting that strong interactions exist between the absorbed water and the polymer. The diffusion profiles measured at room temperature indicate that the diffusion of water into nylon 6,6 at 100°C is Case I Fickian diffusion. The spatial dependence of the T₂ relaxation time constant and its variation with the water content was also examined. The results reveal that both T₂ and T₂^* decrease toward the center of the sample in samples that have a concentration gradient of sorbed water. In fully saturated samples, no spatial dependence was observed. The overall values of T₂ and T₂^* are also observed to increase as a function of exposure time. An evaluation of the desorption process at room temperature and at 100°C was performed. A continuous, exponentially decreasing solvent profile was observed for the desorption process which again indicates Case I Fickian kinetics. The exchange process of external bulk and atmospheric water with deuterium oxide (D₂O) saturated nylon rods has also been studied using the microscopic imaging technique. © 1993 John Wiley & Sons, Inc.     

Structural and spectroscopic characterization of a cationic aquanitrato copper(II) complex with the tetradentate Schiff-base ligand N,N′-bis[1–(2–pyridyl)ethylidene]ethane-1,2–diamine

Cu(NO3)2·3H2O reacts with 1 equiv. of the tetradentate Schiff base N,N-bis[1–(2–pyridyl)ethylidene]ethane-1,2–diamine (LA) in refluxing acetone to yield the [CuLA(ONO2)(H2O)](NO3) complex in ca. 80% yield. The structure of this salt has been determined by single-crystal X-ray crystallography. The copper is six-coordinated with the LA ligand in the equatorial plane and weakly bonded aqua and nitrato ligands above and below this plane. The complex cation is hydrogen-bonded to the nitrate counter-ion. The complex was also characterized by elemental analyses, molar conductivity, room-temperature magnetic susceptibility and spectroscopic (i.r., far-i.r., u.v.–vis, e.s.r.) studies. The data are discussed in terms of the nature of bonding and the known structure.