Synthesis of gentianine N-oxide by enzymatic hydrolysis of swertiamarin in the presence of hydroxylamine and reaction pathway to gentianine and gentianol

Gentianine is a metabolite of gentiopicroside and swertiamarin. Several biological activities have been reported for gentianine, such as antiinflammatory and antidiabetic activity, and hypotensive effect. Gentiopicroside is found in 0.9–9.8% content in Gentian root or Gentian scabra root, and Swertiamarin is contained in Swertia herb in 2–10%. These natural products can be potential starting materials for the synthesis of gentianine. This study describes the β-glucosidase-catalyzed hydrolysis of gentiopicroside and swertiamarin in the presence of hydroxylamine to afford gentianine N-oxide, which can be a synthetic precursor of gentianine derivatives. Enzymatic hydrolysis of swertiamarin selectively afforded gentianine N-oxide in 81% yield, whereas gentiopicroside afforded gentianine N-oxide and gentianol N-oxide. Plausible reaction pathways leading to gentianine, gentianol, and their N-oxides were also investigated.     

Reaction of13N produced by recoil deuterons in pile-irradiated acetic acid-d4 and malonic acid-d4

The reaction of¹³N to form¹³N-labelled compounds was studied in acetic acid-d₄ as a function of the halogenoacetic acid concentration and in malonic acid-d₄ as a function of the intermolecular distance of target malonic acid-d₄ at 195 and 295±6 K. In both deuterated carboxylic acids,¹³N atoms were found in several forms in the order of radiochemical yields,¹³NH₃>H¹³NO₃>[¹³N]aminoacid>HC¹³N. The yield of [¹³N]glycine formed in acetic acid-d₄ were markedly enhanced by iodoacetic acid and slightly by chloroacetic acid. In malonic acid-d₄, the yield of¹³NH₃ was directly proportional to the cubic root of the molar ratio, {D₂O/CD₂ (COOD)₂}, while the yields of H¹³N₃, [¹³N]aminomalonic acid and HC¹³N were inversely proportional to the cubic root of the molar ratio. The mechanism of the formation of the¹³N-compounds are discussed.     

A novel enhancement assay for immunochromatographic test strips using gold nanoparticles

The immunochromatographic assay is a well-known and convenient diagnostic system. In this report, the development of a novel enhancement assay for the test strips is described. Additionally, this highly sensitive immunochromatographic assay was applied to detect human chorionic gonadotropin hormone (HCG) as the model case. The primary antibody-conjugated gold nanoparticles were used as the enhancer of the standard method. The primary antibodies were immobilized within a defined detection zone (test line) on the diagnostic nitrocellulose membrane. The secondary antibodies were conjugated with colloidal gold nanoparticles. In combination with an effective sample pretreatment, the gold-conjugated antibodies and the primary antibodies formed a sandwich complex with the target protein. Within the test line, the sandwich complex was immobilized, and furthermore, concentrated by the enhancer resulting in a localized surface plasmon resonance (LSPR) phenomenon and a distinct red color on the test line. The intensity of color of the red test line (signal intensity), which correlated directly with the concentration of the target protein in the standard or spiked samples, was assessed visually and by computer image analysis using a three-determination analysis. Under optimum conditions, the limit of detection (LOD) for HCG assay was 1 pg/mL. When using human serum, 10 pg/mL of HCG could be detected. We have also spiked total prostate-specific antigen (TPSA) in female serum. The LOD for TPSA was determined as 0.2 ng/mL. With this method, the quantitative determination of the target protein could be completed in less than 15 min. Our novel immunochromatographic strips using the enhancing method based on LSPR of gold nanoparticles are useful as a rapid and simple screening method for the detection of important analytes for medical applications, environmental monitoring, food control, and biosecurity.      

Tilting Theoretical Approach to Moduli Spaces Over Preprojective Algebras

We apply tilting theory over preprojective algebras Λ to the study of moduli spaces of Λ-modules. We define the categories of semistable modules and give equivalences, so-called reflection functors, between them by using tilting modules over Λ. Moreover we prove that the equivalence induces an isomorphism of K-schemes between moduli spaces. In particular, we study the case when the moduli spaces are related to Kleinian singularities, and generalize some results of Crawley-Boevey (Am J Math 122:1027–1037, 2000).     

Focused simulated annealing search: An application to job shop scheduling

This paper presents a simulated annealing search procedure developed to solve job shop scheduling problems simultaneously subject to tardiness and inventory costs. The procedure is shown to significantly increase schedule quality compared to multiple combinations of dispatch rules and release policies, though at the expense of intense computational efforts. A meta-heuristic procedure is developed that aims at increasing the efficiency of simulated annealing by dynamically inflating the costs associated with major inefficiencies in the current solution. Three different variations of this procedure are considered. One of these variations is shown to yield significant reductions in computation time, especially on problems where search is more likely to get trapped in local minima. We analyze why this variation of the meta-heuristic is more effective than the others.     

Maltopentaose-Forming Amylase-Mediated p-Nitrophenyl α-Maltohexaoside formation in an Aqueous-Organic Solvent System :A Substrate for Human Amylase in Serum

ABSTRACT

A maltopentaose-forming amylase [EC 3.2.1.1] from Bacillus licheniformis effectively produced p-nitrophenyl α-maltohexaoside (3) through a transglycosylation reaction from maltohexaose as a donor and p-nitrophenyl α-glucoside (1) as an acceptor in an aqueous solution containing hydrophilic organic solvents. The enzyme specifically transferred from maltohexaose to the 4-position of 1. The yield of 3 depended on the kind of donor, concentration of solvent, pH, and temperature. By the addition of solvents such as dimethyl sulfoxide and 1-butanol, respectively, effects of acceleration on transferase activity of the enzyme and improvement of acceptor solubility were achieved, and resulted in a great increase in the formation of 3.     

Simple method for the introduction of iodo-label on (3-trifluoromethyl) phenyldiazirine for photoaffinity labeling

A simple and mild method was developed for the introduction of iodo-label on (3-trifluoromethyl) phenyldiazirine (TPD) aromatic ring in the presence of three membered diazirine ring. An iodination protocol, I₂-BTI in CH₃CN, was found to be effective even though affinity ligands are pre-installed.     

Gold Nanoparticle‐Based Redox Signal Enhancement for Sensitive Detection of Human Chorionic Gonadotropin Hormone

A sensitive immunosensor for the detection of pregnancy marker, human chorionic gonadotropin hormone (hCG), was developed using the direct electrical detection of Au nanoparticles. We utilized disposable screen‐printed carbon strips (SPCSs) for the development of our immunosensor, which provided cost‐effective tests with the required antigen sample volume as small as 2 μL. After the recognition reaction between the surface‐immobilized primary antibody and hCG, the captured antigen was sandwiched with a secondary antibody that was labeled with Au nanoparticles. Au nanoparticles were exposed to a preoxidation process at 1.2 V for 40 s, which was subsequently followed with a reduction scan on the same surface using differential pulse voltammetry (DPV). We could observe Au nanoparticle‐labeled antigen‐antibody complexes immobilized on the surface of SPCS using scanning electron microscopy (SEM). Additionally, the number of Au nanoparticles on the immunosensor was determined using SEM images, and showed a linear relationship with the current intensity obtained from the DPV measurements with a detection limit of 36 pg/mL hCG (612 fM, 3.6×10^?4 IU/mL). Our immunosensor system, a combination of the screen‐printing technology with Au nanoparticles provides a promising biosensor for various applications in life sciences.     

Rapid analysis of methylated xanthines in teas by an improved high-performance liquid chromatographic method using a polyvinylpolypyrroridone pre-column.

We have developed a new high-performance liquid chromatography (HPLC) method for the analysis of methylated xanthines in tea by removing polyphenols using a polyvinylpolypyrroridone (PVPP) pre-column. The PVPP pre-column was connected with the upstream of analytical column to remove catechins in tea extract. Using this pre-column, caffeine and theobromine in tea, which belong to methylated xanthines, could be rapidly determined in less than 10 min with an isocratic solvent system. RSDs of standard solutions of caffeine and theobromine were about 0.3 and 0.3% for the retention time, and were about 1.6 and 2.5% for the peak area. The quantitation curves of caffeine and theobromine were linear from 5 to over 1000 ng.