Synthesis and Stereostructure of 3-Amino-5- and -6-hydroxybicyclo[2.2.1]heptane-2-carboxylic Acid Diastereomers

Summary. All-endo-3-amino-5-hydroxybicyclo[2.2.1]heptane-2-carboxylic acid and two epimers of 3-amino-6-hydroxybicyclo[2.2.1]heptane-2-carboxylic acid were prepared via 1,3-oxazine or γ-lactone intermediates by the stereoselective functionalization of endo-3-aminobicyclo[2.2.1]hept-5-ene-2-carboxylic acid derivatives. Their structures were proved by IR and NMR spectroscopy, with the use of HMQC, HMBC, DEPT, and DIFFNOE techniques.     

The copper(II) adduct of the unstructured region of the amyloidogenic fragment derived from the human prion protein is redox-active at physiological pH

Prion diseases are caused by the misfolding and aggregation of the prion protein (PrP). Herein we provide evidence that the CuII adduct of the unstructured amyloidogenic fragment of the human PrP (PrP(91-126)) is redox active under physiological conditions. We have identified that the relevant high-affinity CuII binding region of PrP(91-126) is contained between residues 106 and 114. Both [CuII(PrP(91-126))] and [CuII(PrP(106-114))] have CuII Kd values of approximately 90 microM. Furthermore, the smaller PrP fragment PrP(106-114) coordinates CuII producing an electronic absorption spectrum nearly identical with [CuII(PrP(91-126))] (lambda max approximately 610 nm (epsilon approximately 125 M-1 cm-1)) suggesting a similar coordination environment for CuII. Cu K-edge X-ray absorption spectroscopy (XAS) reveals a nearly identical CuN(N/O)2S coordination environment for these two metallopeptides (2N/O at approximately 1.97 A; 1S at approximately 2.30 A; 1 imidazole N at approximately 1.95 A). Both display quasireversible CuII/CuI redox couples at approximately -350 mV vs Ag/AgCl. ESI-MS indicates that both peptides will coordinate CuI. However, XAS indicates differential coordination environments between [CuI(PrP(91-126))] and [CuI(PrP(106-114))]. These data indicate that [CuI(PrP(91-126))] contains Cu in a four coordinate (N/O)2S2 environment with similar (N/O)-Cu bond distances (Cu-(N/O) r = 2.048(4) A), while [CuI(PrP(106-114))] contains Cu in a four coordinate (N/O)2S2 environment with differential (N/O)-Cu bond distances (Cu-(N/O) r1 = 2.057(6) A; r2 = 2.159(3) A). Despite the differential coordination environments both Cu-metallopeptides will catalytically reduce O2 to O2*- at comparable rates.     

Method Validation for Determination of Thallium by Inductively Coupled Plasma Mass Spectrometry and Monitoring of Various Foods in South Korea

Thallium (Tl) is a rare element and one of the most harmful metals. This study validated an analytical method for determining Tl in foods by inductively coupled plasma mass spectrometry (ICP-MS) based on food matrices and calories. For six representative foods, the method’s correlation coefficient (R²) was above 0.999, and the method limit of detection (MLOD) was 0.0070–0.0498 μg kg⁻¹, with accuracy ranging from 82.06% to 119.81% and precision within 10%. We investigated 304 various foods in the South Korean market, including agricultural, fishery, livestock, and processed foods. Tl above the MLOD level was detected in 148 samples and was less than 10 μg kg⁻¹ in 98% of the samples. Comparing the Tl concentrations among food groups revealed that fisheries and animal products had higher Tl contents than cereals and vegetables. Tl exposure via food intake did not exceed the health guidance level.     

Chemiluminescence sequential injection immunoassay for vitellogenin using magnetic microbeads

A rapid and sensitive immunoassay for the determination of carp vitellogenin (Vg) is described. The method involves a sequential injection analysis (SIA) system equipped with a chemiluminescence detector and a samarium-cobalt magnet. An anti-Vg monoclonal antibody, immobilized on magnetic beads, was used as a solid support for the immunoassay. The introduction, trapping and release of the magnetic beads in the flow cell were controlled by a samarium-cobalt magnet and the flow of the carrier solution. The immunoassay was based on a sandwich immunoreaction of anti-Vg monoclonal antibody (primary antibody) on the magnetic beads, Vg, and the anti-Vg antibody labeled with horseradish peroxidase (HRP) (secondary antibody), and was based on a subsequent chemiluminescence reaction of HRP with hydrogen peroxide and p-iodophenol, in a luminol solution. The magnetic beads to which the primary antibody was immobilized were prepared by coupling the primary antibody with the magnetic beads after an agarose-layer on the surface of the magnetic beads was epoxidized. The primary antibody-immobilized magnetic beads were introduced, and trapped in the flow cell equipped with the samarium-cobalt magnet, a Vg sample solution, an HRP-labeled secondary antibody solution and the luminol solution were sequentially introduced into the flow cell based on an SIA programmed sequence. Chemiluminescence emission was monitored by means of a photomultiplier located at the upper side of the flow cell. The optimal incubation times both for the first and second immunoreactions were determined to be 20 min. A concave calibration curve was obtained between Vg concentration and chemiluminescence intensity when various concentrations of standard Vg samples (2–100 ng mL⁻¹) were applied to the SIA system under optimal conditions. In spite of a narrow working range, the lower detection limit of the immunoassay was about 2 ng mL⁻¹.     

Calorimetric examination of palmar connective tissue in Dupuytren’s disease

Dupuytren’s disease is a hand deformity in which the connective tissue of the subcutaneous palmar fascia contracts and toughens over time, eventually forming a thick cord that pulls one or more fingers into a bent position. The reason why this tissue becomes thickened is not precisely described yet. The aim of this study was to characterize the altered metabolism in palmar connective tissue that promotes disease progression. Normal and diseased palmar fascial complexes were acquired during live surgery and the investigation was performed in a relatively short period of time compared to the earlier reports. Similar sample environment was provided for the normal and degenerative samples. The thermal properties of samples were determined by differential scanning calorimetry. Before the examination all water from the surface was removed. Samples were heated from 0 to 80 °C. The heating rate was 0.3 K min^?1. Conventional aluminum alloy vessels were used with 40 μL sample volume. All samples showed a clear denaturation peak on the calorimetric curve. Change in the enthalpy was observed in normal palmar aponeurosis at ?1431.85 kJ kg^?1 (SD = 371.58). In the affected sample ?1508.70 kJ kg^?1 (SD = 245.66) was measured. Our results showed clear evidence that complex deviations from the normal matrix composition during the late stage of degeneration correlated significantly with changes in thermal properties.     

Ring transformations of β-lactam-condensed 1,3-benzothiazines to isoquinoline and thiazole derivatives by sulfur extrusion and addition sequences

The ring transformations of dichloro-β-lactam-fused 2-aryl-1,3-benzothiazines with sodium methoxide were investigated. With 2 equiv of base, the dichloro-β-lactam derivatives underwent rearrangement and dihydro-1,4-benzothiazepines, 3,4-substituted isoquinolines and substituted thiazole disulfides were isolated. A possible reaction mechanism is proposed for the simultaneous formation of the novel products. The formation of isoquinoline and thiazole derivatives can be explained by sulfur extrusion and addition sequences.     

Cycloaddition reactions of 1,3-benzothiazines—I. : Reactions of 2-phenyl-4-H and 4-phenyl-2H-1,3-benzothiazine derivatives with substituted acetyl chlorides

6,7-Dimethoxy-2-phenyl-4$\text{H}$-1,3-benzothiazine (1) and 6,7-dimethoxy-4-phenyl-2$\text{H}$-1,3-benzothiazine (2) react with substituted acetyl chlorides to give linearly, and new angularly condensed β-lactam derivatives (4,5). Heating of the latter compounds with hydrogen chloride in anhydrous ethanol leads to the formation of the corresponding 4$\text{H}$- and 2$\text{H}$-1,3-benzothiazinium chloride, respectively. The configurations of these compounds (the mutual positions of the substituents relative to the β-lactam ring) were determined by ¹H and ¹³C studies, also making use of the aromatic solvent-induced shifts.     

Optimization of hydrothermal growth ZnO Nanorods for enhancement of light extraction from GaN blue LEDs

In this study, we report on the enhancement in the light extraction efficiency of GaN blue LEDs topped with ZnO nanorods. The ZnO nanorods were grown by a two-step hydrothermal synthesis with pre-coated ZnO nanoparticles under optimized condition to give the appropriate size and quality, giving an increase in the light output efficiency of 66%. This improvement is attributed to the optimal rod size and spacing with improved thermal dissipation as compared to light extraction from plain GaN surface. During the ZnO growth on the LEDs, 0.55 M of NH₃ was added and the ZnO sample was later annealed at 475 °C in N₂ ambient, to drive out interstitial oxygen atoms from the tetrahedral unstable site. As a result, a high ratio of UV to orange defect band emission was achieved. The two-step growth of ZnO nanorods on GaN LEDs was effective in generating array of ZnO nanorods which serve as reflector to enhance light extraction from LEDs.