Synthesis of a novel 18β-glycyrrhetinic acid derivative

A novel compound, biotinylated 18β-glycyrrhetinic acid (BGA), was synthesized. It is a compound of 18β-glycyrrhetinic acid linked with biotin. Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 266–267, May–June, 2006. An erratum to this article is available at .     

石墨炉原子吸收光谱法间接测量尿样中氨基多糖含量

本文采用阿利新蓝（ＡｌｃｉａｎＢｌｕｅ）与尿样中氨基多糖（以下称ＧＡＧ）在ｐＨ＝５．８的醋酸钠溶液中，发生沉淀反应生成ＧＡＧ铜复合物。离心分离沉淀物，以石墨炉原子吸收光谱测定沉淀物中铜含量，间接计算ＧＡＧ含量。本文对尿样加入染液浓度，沉淀反应平衡时间；沉淀物的洗涤剂、洗涤次数等进行了探讨，确定了最佳实验条件，实测了６０例健康人尿中ＧＡＧ含量，与文献报导值一致。     

Development of an enzyme-linked immunosorbent assay (ELISA)-like fluorescence assay to investigate the interactions of glycosaminoglycans to cells

Sulfated glycosaminoglycans were labeled with biotin to study their interaction with cells in culture. Thus, heparin, heparan sulfate, chondroitin 4-sulfate, chondroitin 6-sulfate and dermatan sulfate were labeled using biotin-hydrazide, under different conditions. The structural characteristics of the biotinylated products were determined by chemical (molar ratios of hexosamine, uronic acid, sulfate and biotin) and enzymatic methods (susceptibility to degradation by chondroitinases and heparitinases). The binding of biotinylated glycosaminoglycans was investigated both in endothelial and smooth muscle cells in culture, using a novel time resolved fluorometric method based on interaction of europium-labeled streptavidin with the biotin covalently linked to the compounds. The interactions of glycosaminoglycans were saturable and number of binding sites could be obtained for each individual compound. The apparent dissociation constant varied among the different glycosaminoglycans and between the two cell lines. The interactions of the biotinylated glycosaminoglycans with the cells were also evaluated using confocal microscopy. We propose a convenient and reliable method for the preparation of biotinylated glycosaminoglycans, as well as a sensitive non-competitive fluorescence-based assay for studies of the interactions and binding of these compounds to cells in culture.     

Synthesis of N~(11)-anchoring biotinylated artemisinin derivatives and their preliminary biological assessment

Unique endoperoxide moiety of artemisinin and its derivatives has been considered the functionality exhibiting highly potent antimalarial and anticancer activities.To investigate the mechanisms of their biological actions,development of suitable molecular probes including biotinylated derivatives is of extreme significance.The synthesis and preliminary biological assessment of four new biotinylated artemisinin derivatives have been reported in this work.     

Solvothermal synthesis and luminescence properties of Tb-doped gadolinium aluminum garnet

Different concentrations of Tb³⁺ ion-doped gadolinium aluminum garnet (GAG) nanophosphors have been synthesized by solvothermal reaction method and sintered at 1300 °C. The XRD patterns confirm that the GAG phosphors sintered at 1300 °C have a garnet structure with single cubic phase. The calculated crystallite size is about 92 nm. The SEM images of the phosphors show the spherical morphology agglomerated with many small particles. The luminescence properties of these phosphors have been carried out by the emission and excitation spectra along with lifetime measurements. The excitation spectra of GAG:Tb³⁺ phosphors consist of three broad bands due to the 4f⁸→4f⁷5d¹ transition and some sharp peaks due to the 4f⁸→4f⁸ transition. The emission spectra of the phosphors reveal two colors, such as blue due to ⁵D₃→⁷F_J transitions and green due to the ⁵D₄→⁷F_J transitions. The dynamics of the phosphors have been investigated by decay curves and the cross-relaxation process and is observed at 0.5 mol% Tb³⁺ concentration.     

Biotinyl-Glucose-6-Phosphate Dehydrogenase Preparation,Kinetics, and Modulation by Avidin

The kinetics of free glucose-6-phosphate dehydrogenase (G-6-PDH), biotinylated G-6-PDH, and biotinylated G-6-PDH complexed with avidin were investigated. The kinetics of the free enzyme were consistent with a sequential rather than a ping-pong mechanism. The kinetics of the biotinylated enzyme were similar to that of the free enzyme, but the kinetic constants were different; theK _m value for NADP was halved, whereas theK _m for G-6-P decreased only slightly. In the presence of avidin, theK _m of biotinylated G-6-PDH for G-6-P nearly doubled whereas theK _m for NADP did not change significantly. Avidin complexed with biotinylated G-6-PDH inhibited the enzyme from acting. Based upon these reactions, it was possible to devise assays for either free biotin or free avidin using biotinylated G-6-PDH as the indicator enzyme. Concentrations of biotin between 40 and 60 mg/mL, or of 25–95 Μg/mL of avidin could be measured within 2 min through the use of biotinylated G-6-PDH.     

Performance of Impedimetric Biosensors Based on Anodically Formed Ti/TiO2 Electrodes

The advantages and limitations of impedimetric sensors based on Ti/TiO₂ architectures are described. Titanium dioxide (titania) was potentiostatically formed onto titanium electrodes of 2 mm diameter, at 10 and 30 V in 1 M H₂SO₄. The thickness of the titania layers was ellipsometrically determined to be 30 and 86 nm respectively and they are highly insulating with charge‐transfer resistances in the MΩ range, as they were measured with electrochemical impedance spectroscopy under specific experimental conditions. Low voltage anodization (<10 V) results to amorphous TiO₂, whereas at higher applied voltages (>25 V), anatase is the predominant form. SEM images are indicative of quite smooth, compact coatings without any severe cracks.     

Designs of Enterobacteriaceae Lac Z Gene DNA Gold Screen Printed Biosensors

This paper describes specific electrochemical enterobacteriaceae lac Z gene DNA sensors based on immobilization of a thiolated 25 base single stranded probe onto disposable screen printed gold electrodes (gold SPEs). Two configurations have been evaluated. In the first one, the capture probe was attached to the electrode surface through its ? SH moiety, while mercaptohexanol (MCH) was used as spacer for the displacement of nonspecifically adsorbed oligonucleotide molecules. The hybridization event between the probe and target DNA sequences was detected at ?0.20 V by square‐wave voltammetry (SWV), using methylene blue (MB) as electrochemical indicator. The second genosensor configuration involved modification of gold high temperature SPEs with a 3,3′‐dithiodipropionic acid di(N‐succinimidyl ester) (DTSP) self‐assembled monolayer (SAM). Moreover, 2‐aminoethanol was used as blocking agent, and further modification with avidin allowed binding of the biotinylated enterobacteriaceae lac Z gene DNA probe. An enzyme amplified detection scheme was applied, based on the coupling of streptavidin‐peroxidase to the biotinylated complementary target, after the hybridization process, and immobilization of tetrathiafulvalene (TTF) as redox mediator atop the modified electrode. The amperometric response obtained at ?0.15 V after the addition of hydrogen peroxide was used to detect the hybridization process. Experimental variables concerning sensors composition and electrochemical transduction were evaluated in both cases. A better precision and reproducibility in the fabrication process, as well as a higher sensitivity were achieved using the biotinylated probe‐based sensor configuration. A limit of detection of 0.002 ng/μL was obtained without any preconcentration step.     

From Polymer to Size‐Defined Oligomers: A Step Economy Process for the Efficient and Stereocontrolled Construction of Chondroitin Oligosaccharides and Biotinylated Conjugates Thereof: Part 1

Controlled acid hydrolysis of polymeric chondroitin sulfate of bovine origin afforded in good yield a basic disaccharide fragment that was used for the first time as a starting material for the expeditious preparation of a set of building blocks that in turn act as versatile synthons for the efficient and stereocontrolled construction of a collection of size‐defined chondroitin oligomers (from di‐ to octasaccharides). This step economy process allows their preparation as reducing species, fitted with a fluorophore, or as biotinylated conjugates; all useful tools for the preparation of microarrays, or as probes for the study of the biosynthesis of chondroitin sulfate.     

Design and Synthesis of Biotinylated Troglitazone as an Active Affinity Probe

A biotin‐tagged analogue of troglitazone was designed, synthesized and applied to affinity chromatography to pulldown EGFR from 293T cell lysates overexpressing EGFR, a membrane protein assumed to be troglitazone's direct binding target by previous work. The results indicate the feasibility of the biotinylated probe as a vigorous tool to clarify the molecular mechanisms for troglitazone's antitumor activities.