Magnetically aligned phospholipid bilayers with large q ratios stabilize magnetic alignment with high order in the gel and L(alpha) phases

The magnetic alignment behavior ofbicelles (magnetically alignable phospholipid bilayered membranes) as a function of the q ratio (1,2-dihexanoyl-sn-glycerol phosphatidylcholine/1,2-dimyristoyl-sn-glycerol phosphatidylcholine mole ratio) and temperature was studied by spin-labeled X-band electron paramagnetic resonance (EPR) spectroscopy and solid-state 2H and 31P NMR spectroscopy. Well-aligned bicelle samples were obtained at 45 degrees C for q ratios between 2.5 and 9.5 in both the EPR and NMR spectroscopic studies. The molecular order of the system, S(mol), increased as the q ratio increased and as the temperature decreased. For higher q ratios (> or = 5.5), bicelles maintained magnetic alignment when cooled below the main phase transition temperature (approximately 30 degrees C when in the presence of lanthanide cations), which is the first time, to our knowledge, that bicelles were magnetically aligned in the gel phase. For the 9.5 q ratio sample at 25 degrees C, S(mol) was calculated to be 0.83 (from 2H NMR spectra, utilizing the isotopic label perdeuterated 1,2-dimyristoyl-sn-glycerol phosphatidylcholine) and 0.911 (from EPR spectra utilizing the spin probe 3beta-doxyl-5alpha-cholestane). The molecular ordering of the high q ratio bicelles is comparable to literature values of S(mol) for both multilamellar vesicles and macroscopically aligned phospholipid bilayers on glass plates. The order parameter S(bicelle) revealed that the greatest degree of bicelle alignment was found at higher temperatures and larger q ratios (S(bicelle) = -0.92 for q ratio 8.5 at 50 degrees C).     

Speciation of Arsenic Compounds in the Urine of Rats Orally Exposed to Dimethylarsinic Acid Ion Chromatography with ICP–MS as an Element-Selective Detector

A combined ion chromatography (IC) with inductively coupled plasma mass spectrometry (ICP—MS) system as an element-selective detector has been used for the determination of arsenic compounds. Seven arsenic compounds were separated by cation-exchange chromatography. Subsequently, the separated arsenic compounds were directly introduced into the ICP—MS and were detected at m/z =75. Detection limits for the seven arsenic compounds ranged from 0.8 to 3.8 μg As/l. The IC–ICP–MS system was applied to the determination of arsenic compounds in the urine of dimethylarsinic acid (DMAA)-exposed rats. DMAA was the most abundant arsenic compound detected. Arsenous acid, monomethylarsonic acid and trimethylarsine oxide were also detected.     

Gold nano-popcorn-based targeted diagnosis, nanotherapy treatment, and in situ monitoring of photothermal therapy response of prostate cancer cells using surface-enhanced Raman spectroscopy

Prostate cancer is the second leading cause of cancer-related death among the American male population, and the cost of treating prostate cancer patients is about $10 billion/year in the United States. Current treatments are mostly ineffective against advanced-stage prostate cancer and are often associated with severe side effects. Driven by these factors, we report a multifunctional, nanotechnology-driven, gold nano-popcorn-based surface-enhanced Raman scattering (SERS) assay for targeted sensing, nanotherapy treatment, and in situ monitoring of photothermal nanotherapy response during the therapy process. Our experimental data show that, in the presence of LNCaP human prostate cancer cells, multifunctional popcorn-shaped gold nanoparticles form several hot spots and provide a significant enhancement of the Raman signal intensity by several orders of magnitude (2.5 × 10(9)). As a result, it can recognize human prostate cancer cells at the 50-cells level. Our results indicate that the localized heating that occurs during near-infrared irradiation can cause irreparable cellular damage to the prostate cancer cells. Our in situ time-dependent results demonstrate for the first time that, by monitoring SERS intensity changes, one can monitor photothermal nanotherapy response during the therapy process. Possible mechanisms and operating principles of our SERS assay are discussed. Ultimately, this nanotechnology-driven assay could have enormous potential applications in rapid, on-site targeted sensing, nanotherapy treatment, and monitoring of the nanotherapy process, which are critical to providing effective treatment of cancer.     

Role of balanced charge carrier transport in low band gap polymer:Fullerene bulk heterojunction solar cells

Lowering of the optical band gap of conjugated polymers in bulk heterojunction solar cells not only leads to an increased absorption but also to an increase of the optimal active layer thickness due to interference effects at longer wavelengths. The increased carrier densities due to the enhanced absorption and thicker active layers make low band gap solar cells more sensitive to formation of space charges and recombination. By systematically red shifting the optical parameters of poly[2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐p‐phenylenevinylene] and 6,6‐phenyl C₆₁‐butyric acid methyl ester, we simulate the effect of a reduced band gap on the solar cell efficiencies. We show that especially the fill factor of low band gap cells is very sensitive to the balance of the charge transport. For a low band gap cell with an active layer thickness of 250 nm, the fill factor of 50% for balanced transport is reduced to less than 40% by an imbalance of only one order of magnitude. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

An investigation of FeCoCrO4 by Mossbauer spectroscopy

The spinel FeCoCrO₄ has been studied between 4.2 and 538°K. Characteristic Mossbauer spectra of paramagnetic, magnetic and electronic relaxation types have been observed. The Mossbauer parameters for Fe³⁺ ions situated at tetrahedral (A) and octahedral (B) sites have been calculated. The cation distribution in magnetic and paramagnetic phases is found to be approximately Fe_0.5³⁺Co_0.5²⁺[Co_0.5²⁺Fe_0.5³⁺Cr³⁺]O₄. The Neel temperature been determined by the temperature scanning method to be 310±5°K.     

High field magnetization of europium-graphite intercalation compound C6Eu

The whole magnetization curve of the first stage compound C₆Eu has been measured by using pulsed fields up to 400 kG below 40 K. For H ⊥ c, c being the crystal c-axis, four regions are observed in the magnetization curve; I) the initial magnetization region with an apparent moment of ～ 0.6micro_B per Eu ion (H < 12 kG), II) the intermediate region with nearly constant moment of 2.2 – 2.7 micro_B, which corresponds to $\text{1}\text{3}$ the full moment of Eu²⁺ ion (22 < H < 82 kG), III) the region of a linear field dependence (82 < H < 205 kG), and IV) the saturation region above 205 kG, where the saturation moment is found as 6.2 micro_B. For H//c, the magnetization increases monotonically and approaches to a saturation value corresponding to 6 micro_B above 240 kG.     

Shape amphiphiles: mixing rods and disks in liquid crystals

Mixtures of rodlike and disklike liquid crystals suffer from phase separation. However, such mixtures can be homogenized if a molecule is added which comprises a rod- and a disklike fragment linked together covalently. We have termed such a molecule a shape amphiphile and believe that this represents a new class of amphiphilicity.     

Synthesis of some newer 5-(5-aryl-2H-tetrazol-2-ylmethyl)-4-substituted-s-triazole-3-thiols as possible antiinflammatory agents

Several 1-(5-aryl-2H-tetrazol-2-ylacetyl)-4-substituted thiosemicarbazides and 5-(5-aryl-2H-tetrazol-2-yl-methyl)-4-substituted-s-triazole-3-thiols were synthesized as possible antiinflammatory agents. These compounds were characterized by their elemental, infrared and nuclear magnetic resonance analysis.     

Site-selective photocycloadditions of 2-pyrones with electron-poor olefins and the derivation from the cycloadducts

Photosensitized cycloaddition of 4,6-dimethyl-2-pyrone ( 1 ) with methacrylonitrile ( 3b ) afforded two types of [2 + 2]cycloadducts, 4b and 6b , across the C₅-C₆ and C₃-C₄ double bonds in 1 , respectively. Photosensitized reactions of 1 with dimethyl maleate and dimethyl cyclobutene-1,2-dicarboxylate gave [2 + 2]cycload-ducts 4d, 4e across the C₅-C₆ double bond, in addition to [4 + 2]cycloadduct 9d or bicyclo[4.2.0]octadiene 10e . The photoreactions of methyl 2-pyrone-5-carboxylate ( 2 ) with 3b and 2-chloroacrylonitrile ( 3c ) gave [4 + 2]cycloadducts 5b, 5c in addition to [2 + 2]cycloadducts 11b and 11c across the C₅-C₆ double bond in 2 . The photocycloaddition mechanism was explained from results calculated by means of PM3-CI method. Namely, the site- and/or regio-selective products, 4, 5, 8, 9 and 10 were thought to come from the same site-selective radical intermediates in the case of electron-poor olefins. Pyrolysis and/or hydrolysis of the cycload-ducts 4e, 5b, 5c gave 5,6-dihydro-2-pyrone 12 or benzene derivatives.     

Separation of phytosterol oxidation products by combination of different polarity gas chromatography capillary columns

The number of characterized phytosterol oxidation products (POPs) from both ring- and side-chain structures has increased during recent decades, resulting in difficulties in the separation of POPs on different gas chromatography (GC) capillary columns. The main objective of this study was to separate a mixture of 29 purified and characterized oxidation products from sito-, campe- and stigmasterol using GC capillary columns with different polarity. For the first time in the area of POPs analysis, the separation efficiency of the combination of two capillary GC columns with different polarities was investigated. A non-polar 5% phenyl coated (DB5-MS) and a mid-polar 35% phenyl coated (DB35-MS) column was combined with a pressfit connector. The main improvement was enhanced base line separation for many of the analyzed POPs, compared with the separations achieved using the individual columns. However, three pairs of POPs co-eluted: 24-hydroxysitosterol/campesterol-5beta,6beta-epoxide, stigmasterol-5beta,6beta-epoxide/campesterol-5alpha,6alpha-epoxide and stigmasterol-5alpha,6alpha-epoxide/campestanetriol.