Hydrolytic Activity of α-Mannosidase against Deoxy Derivatives of p-Nitrophenyl α-d-Mannopyranoside

Deoxy derivatives of p-nitrophenyl (PNP) α-d-mannopyranoside, PNP 2-deoxy-α-d-arabino-hexopyranoside, 3-deoxy-α-d-arabino-hexopyranoside, 4-deoxy-α-d-lyxo-hexopyranoside, and α-d-rhamnopyranoside, were synthesized and hydrolytic activities of jack bean and almond α-mannosidases against them were investigated. These α-mannosidases scarcely acted on the 2-, 3-, and 4-deoxy derivatives, while the 6-deoxy one was hydrolyzed by the enzymes as fast as PNP α-d-mannopyranoside, which is a common substrate for α-mannosidase. These results indicate that the hydroxyl groups at C-2, 3, and 4 of the mannopyranoside are necessary to be recognized as a substrate by these enzymes, while that at C-6 does not have so a crucial role in substrate discrimination. Values of K_m and V_max of the enzymes on the hydrolysis of PNP α-d-rhamnopyranoside were obtained from kinetic studies.     

Synthesis of N-Acetylmuramyl-L-Alanyl-D-Isoglutamine Aryl β-Glycosides

Synthesis of N-acetylmuramyl-L-alanyl-D-isoglutamine phenyl and (2-naphthyl) -glycosides, novel muramyl dipeptide derivatives with phenolic aglycons, was reported. The starting N-acetylglucosamine aryl glycosides were obtained by glycosylation of phenols with peracetylated -glucosaminyl chloride under the conditions of phase-transfer catalysis and used for the synthesis of 4,6-O-isopropylidene-N-acetylmyramic acid aryl -glycosides. Condensation of these derivatives with a dipeptide and subsequent deprotection resulted in the intended glycopeptides.     

Preparation of New Derivatives from α-Dihydro Grayanotoxin-II

Rhodojaponin-III and 10,14-epoxy-10-deoxy grayanotoxin-III were derived from grayanotoxin-I and -III, respectively. Preparation of 13 new derivatives from α-dihydro grayanotoxin-II was discussed. Some of them showed higher physiological activity than that of natural grayanotoxins.     

Synthesis of N-Acetylglucosamine Aryl β-Glycosides Catalyzed by Crown Compounds

Glycosylation of various phenols with -D-glucosaminyl chloride peracetate in a solid phase–liquid system catalyzed by crown compounds was studied. The highest yields of aryl -glycosides were observed at room temperature in acetonitrile using anhydrous potassium carbonate as a base. The optimum phenol–glycosyl donor–base–crown ether ratio was 1 : 1 : 1 : 0.2.     

Synthesis of β-Diketone DNA Derivatives for Affinity Modification of Proteins

Russian Journal of Bioorganic Chemistry - Diketone DNA derivatives have been proposed to modify the guanidine group of Arg in proteins. The β-diketo group at the C2' atom of the sugar...     

Preparation and immunological characterization of β-lactoglobulin-amylose conjugate

β-Lactoglobulin (BLG), a major allergen of cow's milk, was conjugated with the N-hydroxysuccinimide ester of the amylose-glycylglycine adduct (AG-ONSu) to reduce its immunogenicity, and the biochemical and immunological properties of the resulting conjugate (AG-BLG) were studied. The conjugate was prepared by modifying BLG with AG-ONSu, and was purified in a Sephadex G-100 column. The analytical data for AG-BLG indicated that 10.5 moles of AG-ONSu, with a mean molecular weight of 2,800, was covalently attached to the amino groups of the BLG molecule. Conjugation with AG-ONSu greatly decreased the reactivity of BLG with anti-BLG polyclonal antibodies owing to its shielding action for epitopes on the protein's surface. These findings suggest that AG-ONSu can be used advantageously to suppress the hypersensitivity mediated by IgG antibodies in milk allergy.     

Preparation and Physicochemical Characterization of Amoxicillin β-cyclodextrin Complexes

Amoxicillin (AMOX), a penicillin A, belongs to the β-lactam family It is usually the drug of choice within the class because it is better absorbed, following oral administration, than other β-lactam antibiotics. Its β-lactamase degradation might be prevented by using a molecular [AMOX:β-CD] complex. The aim of this work was to prepare complexes using two methods and then characterize interactions between AMOX and the native β-CD. The extent of complexation in solution has been evaluated by high-performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR), and 2D rotating-frame Overhauser enhancement spectroscopy (2D ROESY). Mass changes (TG), calorimetric effects (DSC), and mass spectrometry (MS) were determined on the same sample under identical conditions using the Skimmer coupling system. Skimmer and infrared spectroscopy (FT-IR) were used to characterize the solid state of the binary system. Complexation of AMOX with β-CD was proven by FT-IR, NMR, DSC, and HPLC. The 2D ROESY spectra did not show any dipolar proton interaction of the AMOX with cyclodextrin. The 1:1 stoichiometry of the complex was obtained by HPLC. The stability constant for AMOX with β-CD was determined to be 1,878 M⁻¹. In the [AMOX:β-CD] complex, the phenyl group is included inside the β-CD, and the ionized carboxyl group on the penam ring forms hydrogen bonds with the secondary hydroxyl groups of another β-CD to keep the complex stable. Preparation methods allowed exactly the same complex.     

Analgesic Effects of β-Phenylethylamine and Various Methylated Derivatives in Mice

Administration of β-phenylethylamine (PEA), the simplest endogenous neuroamine, and various methylated PEA derivatives including α-methyl PEA (amphetamine, AMP) elicits analgesia in mice. Five or 20 min after intraperitoneal PEA injection of as little as 6 mg/kg resulted in an increased latency response time (from 2.4 ± 0.4 to 8.5 ± 2.3 or 7.0 ± 3.0 s, respectively) to the thermal stimulus (hot-plate test), which reached statistical significance at the 15 mg/kg (20 min; 13.1 ± 0.4 s) or 25 mg/kg dose (5 min; 15.3 ± 4.1 s). This PEA effect, was dose-dependent (albeit non-linear: 6, 12, 15, 25, 50 and 100 mg/kg), reached the cut-off time of 45 s at the upper PEA dose (5 min), and it was consistently enhanced by pretreatment with the monoamine oxidase inhibitor pargyline (P). Methylated PEA derivatives (15 and 100 mg/kg dose) produced various degrees of analgesia (in decreasing order p-Me PEA > PEA > N,N-diMe PEA > N-Me PEA) which, likewise to PEA itself, were consistently increased by P and declined over time (mice tested 5, 20 and 60 min after amine injection); small but statistically significant o- and β-Me PEA antinociceptive effects (5 min) were observed only at the higher dose (in the presence of P for β-Me PEA). A small analgesic effect was observed after the administration of AMP (5 or 10 mg/kg) which failed, even after P, to reach statistically significance. Independent of the amine and concentration tested, individual compound’s antinociceptive properties were reliably increased by P (exception of AMP), decreased by reserpine (R) or haloperidol (H), and remained essentially unchanged after naloxone (N) administration suggesting the involvement of catecholamines, but not opioid peptides, in their observed analgesic effects. Injection of P + N produced results similar to those seen after P alone. Under the experimental conditions described neither P, R, H or N had any effects by themselves. These findings suggest additional understanding of the mechanism of action responsible for the analgesic effects of these amines would be of interest, leading further to controlled studies on their alleged usefulness as weight reducing agents and sport performance enhancers.     

A Simple Method for Preparation of 18α-Glycyrrhetinic Acid and Its Derivatives

Treatment of 18-glycyrrhizic acid with a methanolic solution of HCl resulted in 1 : 1 mixture of methyl esters of 18- and 18-glycyrrhetinic acids. Benzoylation of the mixture led to methyl esters of 3-benzoyl-18-glycyrrhetinic acid and 3-benzoyl-18-glycyrrhetinic acid, which were separated by chromatography on silica gel. 18-Glycyrrhetinic acid was prepared by alkaline hydrolysis of methyl 3-benzoyl-18-glycyrrhetinate and was further used for the syntheses of 3-keto-18-glycyrrhetinic acid and methyl esters of 18-glycyrrhetinic acid and 3-keto-18-glycyrrhetinic acid.     

Preparation of salidroside with n-butyl β-D-glucoside as the glycone donor via a two-step enzymatic synthesis catalyzed by immobilized β-glucosidase from bitter almonds

β-Glucosidase from bitter almonds was immobilized on epoxy group-functionalized beads for catalyzing salidroside synthesis in a two-step process with n-butyl-β-D-glucoside (BG) as the glucosyl donor. The formation of salidroside ((0.59?±?0.02) M) at a yield of 39.04%±1.25% was accomplished in 8?h by the transglucosylation of immobilized β-glucosidase at pH 8.0 and 50?°C when the ratio of BG to tyrosol was 1:2 (mol/mol). A study on the influence of different glycosyl acceptors demonstrated that the yield of the glucosylation reaction of phenylmethanol and cyclohexanol was higher than that of either phenol or cyclohexanol. This may account for the selectivity of the immobilized enzyme towards the alcoholic hydroxyl group of tyrosol in the salidroside synthesis reaction. A study on the synthesis of BG via the reverse hydrolysis of immobilized β-glucosidase showed that a yield of 78.04%±2.2% BG can be obtained with a product concentration of (0.23?±?0.015) M.     

Preparation of β-nitroalanine using the Easton three-component coupling method

Summary. A simple one-step preparation of β-nitroalanine has been developed using the Easton three-component coupling method. To date one limitation of this method has been that use of nitromethane as the nitroalkane component does not yield β-nitroalanine. We report that use of the dipotassium salt of nitroacetic acid in the Easton three-component coupling gives β-nitroalanine in high yield, presumably via facile decarboxylation of a β-nitroaspartate intermediate.     

Synthesis and Biological Evaluation of β-D-Pentofuranonucleoside Derivatives of 2-Azidoadenine and 6-Azidopurines

Abstract

β-D-pentofuranonucleoside derivatives of 2-azidoadenine and 6-azidopurines have been synthesized. The azido-tetrazolo tautomerism observed on such nucleoside analogues has been studied. The compounds were tested for their activity against HIV and HBV but they did not show significant antiviral effect.     

Preparation of pure populations of covalently stabilized amyloid β-protein oligomers of specific sizes

Evidence suggests that amyloid β-protein (Aβ) oligomers may be seminal pathogenic agents in Alzheimer's disease (AD). If so, developing oligomer-targeted therapeutics requires an understanding of oligomer structure. This has been difficult due to the instability of these non-covalently associated Aβ assemblies. We previously used rapid, zero-length, in situ chemical cross-linking to stabilize oligomers of Aβ40. These enabled us to isolate pure, stable populations of dimers, trimers, and tetramers and to determine their structure-activity relationships. However, equivalent methods applied to Aβ42 did not produce stable oligomers. We report here that the use of an Aβ42 homologue, [F10, Y42]Aβ42, coupled with sequential denaturation/dissociation and gel electrophoresis procedures, provides the means to produce highly pure, stable populations of oligomers of sizes ranging from dimer through dodecamer that are suitable for structure-activity relationship determination.     

Chemical Conversion of Some Ribonucleosides into the Corresponding β-D-Arabinofuranosyl Derivatives1

Abstract

Five 3′,5′-di-O-acylribonucleosides were converted into the corresponding β-D-arabinofuranosyl derivatives through DMSO-oxidation followed by NaBH₄-reduction and deacylation with NaOMe-MeOH.     

Synthesis of Optically Active β-Amino-γ-butyrolactone Derivatives from Aspartic Acid

(3S, 4R)-3-Methoxycarbonylamino-4-phenyl-4-butanolide (4a) was prepared from l-aspartic acid by stereoselective reduction of ethyl (*S)-3-methoxycarbonylamino-4-oxo-4-phenylbutyrate (3a).     

Preparation of a glycosynthase from the β-glycosidase of the Archaeon Pyrococcus horikoshii

The β-glycosidase from the hyperthermophilic Archaeon Pyrococcus horikoshii (Phoβ-gly) is a monomeric enzyme with wide substrate specificity belonging to family 1 of glycoside hydrolases classification. Inspection of the three-dimensional structure of the enzyme, recently resolved, showed that Phoβ-gly is membrane bound and that the residues putatively involved in the catalytic activity are Glu155 and Glu324 working as the general acid/base and the nucleophile of the reaction, respectively. We show here that mutation of the latter completely eliminated the activity of the enzyme and that it could be reactivated in the presence of sodium formate. Analysis of the products obtained in the presence of sodium formate buffer pH 4.0 at 75°C showed that the Glu324Gly mutant acts as a hyperthermophilic glycosynthase.     

β-TrCP Inhibition Reduces Prostate Cancer Cell Growth via Upregulation of the Aryl Hydrocarbon Receptor

Background

Prostate cancer is a common and heterogeneous disease, where androgen receptor (AR) signaling plays a pivotal role in development and progression. The initial treatment for advanced prostate cancer is suppression of androgen signaling. Later on, essentially all patients develop an androgen independent stage which does not respond to anti hormonal treatment. Thus, alternative strategies targeting novel molecular mechanisms are required. β-TrCP is an E3 ligase that targets various substrates essential for many aspects of tumorigenesis.

Methodology/Principal Findings

Here we show that β-TrCP depletion suppresses prostate cancer and identify a relevant growth control mechanism. shRNA targeted against β-TrCP reduced prostate cancer cell growth and cooperated with androgen ablation in vitro and in vivo. We found that β-TrCP inhibition leads to upregulation of the aryl hydrocarbon receptor (AhR) mediating the therapeutic effect. This phenomenon could be ligand independent, as the AhR ligand 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) did not alter prostate cancer cell growth. We detected high AhR expression and activation in basal cells and atrophic epithelial cells of human cancer bearing prostates. AhR expression and activation is also significantly higher in tumor cells compared to benign glandular epithelium.

Conclusions/Significance

Together these observations suggest that AhR activation may be a cancer counteracting mechanism in the prostate. We maintain that combining β-TrCP inhibition with androgen ablation could benefit advanced prostate cancer patients.     

Preparation and conformational analysis of C-glycosyl β- and β/β-peptides

Ten C-glycosyl β²- and β/β²-peptides with three to eight amino acid residues have been prepared. Solution and solid-phase peptide syntheses were employed to assemble β²-amino acids in which C-glycosylic substituents are attached to the C-2 position of β-amino acids. Conformational analysis of the C-glycosyl β²-peptides using NMR and CD spectra indicates that the tripeptide can form a helical secondary structure. Besides, helix directions of the C-glycosyl β/β²-peptides are governed by the configuration at the α-carbon of the peptide backbone that originates from the stereocenter of the C-glycosyl β²-amino acids.     

Preparation and characterization of biotinylated probes for the β-interferon receptor

• 1.1. Recently we described the isolation of the β-interferon receptor [Zhang et al. (1986) J. biol. Chem. 261, 8017–8021]. A highly purified product was obtained but in low quantities.
• 2.2. The use ofbiotinylated β-interferon as a ligand represents an alternate approach to receptor isolation.
• 3.3. We have prepared and characterized the derivatives N-(biotinyl)- and N-(biotinyl-ϵ-aminocaproyl)-recombinant human [Ser¹⁷-interferon β (B- and BC-recHulFNβ).
• 4.4. Biotin incorporation does not result in any loss of antiviral activity, demonstrating the recognition of the derivative by the cell receptor.
• 5.5. The biotinylated recHuIFNβ binds specifically and reversibly to succinoylavidin or guanidine thiocyanate-stripped succinoylavidin linked to a Sepharose matrix.
• 6.6. Comparison of the competition curves obtained with [¹⁴C]biotin and [³H]biotinyl recHuIFN, in the presence of increasing concentrations of biotin suggests that the IFN moiety of the derivative has little effect on the affinity of biotin for avidin.
• 7.7. Biotinylated recHuIFNβ derivatives represent useful probes for the β-IFN receptor.