The diastereoselective synthesis of methyl 5-deoxy-5-(dialkylphosphono)-5-(dialkylphosphorylamido)-2,3-O-isopropylidene-beta-D-ribofuranosides

A convenient method has been developed for the diastereoselective synthesis of methyl 5-deoxy-5-(dialkylphosphono)-5-(dialkylphosphorylamido)-2,3-O-isopropylidene-beta-d-ribofuranosides under mild conditions, namely the reaction of a dialkyl phosphoramidate with a dialkyl phosphite and methyl 2,3-O-isopropylidene-beta-d-ribo-pentodialdo-1,4-furanoside in acetyl chloride in a one-pot procedure.     

Oligodeoxyribonucleotides Covalently Linked via Nucleic Bases with 3′-5′ and 5′-5′ Polarities

Abstract

The solid-phase preparation of oligodeoxyribonucleotides covalently linked via nucleic bases with normal (3′-5′) or inverted (5′-5′) polarities is reported. The key-step of these syntheses is the preparation of the tethered dimers.     

Inhibition of adenylate kinase by P1-(lin-benzo-5'-adenosyl)-P4-(5'-adenosyl) tetraphosphate and P1-(lin-benzo-5'-adenosyl)-P5-(5'-adenosyl pentaphosphate.

P1-(lin-Benzo-5'-adenosyl)-P5-(5'-adenosyl) penraphosphate and P1-(lin-benzo-5'-adenosyl)-P4-(5'-adenosyl) tetraphosphate have been synthesized from lin-benzoadenosine 5'-monophosphoromorpholidate and adenosine 5'-tetraphosphate and adenosine 5'-triphosphate. These mixed dinucleoside polyphosphates are potent inhibitors of porcine muscle adenylate kinase, with association constants of 2 x 10(5) M-1 for the pentaphosphate and 2 x 10(6) M-1 for the tetraphosphate, respectively, as determined by kinetics and fluorescence experiments. The increase in fluorescence intensities and fluorescence lifetimes of both inhibitors upon binding to adenylate kinase results from a breaking of the intramolecular stacking interaction observed when these ligands are free in solution and implicates their binding to the enzyme in an "open" or "extended" form. These results and the dimensional requirements of these inhibitors are discussed in relation to our current knowledge of the active site of adenylate kinase and to the known inhibitors of adenylate kinase, P1,P5-bis(5'-adenosyl) pentaphosphate and P1,P4-bis-(5'-adenosyl) tetraphosphate.     

Functional analysis of 2-5A-dependent RNase and 2-5a using 2',5'-oligoadenylate-cellulose

2-5A is an intracellular effector that has been implicated in interferon action, hormonal regulation, and cell growth control. 2-5A action is mediated through its activation of 2-5A-dependent RNase (RNase L, RNase F). Affinity resins [2-5A-cellulose and core (2-5A)-cellulose] were chemically synthesized for purification and immobilization of 2-5A-dependent RNase from mouse L cells and rabbit reticulocyte lysates. The breakdown of poly(U)-[3'-32P]Cp to acid-soluble fragments was demonstrated using the 2-5A-dependent RNase:2-5A -cellulose complex; this activity was enhanced by adding (free) 2-5A. In contrast, RNase activity was measured from the 2-5A-dependent RNase:core (2-5A)-cellulose complex only after the addition of free 2-5A. The rabbit reticulocyte 2-5A-dependent RNase is activated only by tetramer or higher oligomers of 2-5A; therefore there was breakdown of poly(U)-[3'-32P]Cp using core (2-5A)-cellulose-bound reticulocyte 2-5A-dependent RNase after addition of tetramer 2-5A but there was no poly(U) degradation in the presence of trimer 2-5A. The absence of significant general nuclease in the assays was demonstrated by the resistance to breakdown of poly(C)-[3'-32P]Cp (not susceptible to 2-5A-dependent RNase). Moreover, core (2-5A)-cellulose was used to develop a sensitive (subnanomolar) assay for the detection of authentic 2-5A. 2-5A, or the material to be tested, was added to mouse L-cell 2-5A-dependent RNase:core (2-5A)-cellulose complex in the presence of poly(U)-[3'-32P]Cp. The concentration of 2-5A in the sample could be measured from the amount of poly(U) degradation. Several closely related analogs of 2-5A were tested and found to be completely inactive. The technology described herein may be applied to the study of the regulation of 2-5A-dependent RNase, the detection of 2-5A from cells and tissues, and other aspects of the 2-5A system.     

Phosphorylation of 2-5A core 5'-diphosphate to 2-5A in mouse L cell extracts

When added to extracts of mouse L cells containing ATP and an energy regenerating system, the 5'-diphosphate of 2-5A core, pp5'A2'p5'A2'p5'A, as well as a bromoadenylate analog, pp5' (br8A)2'p5'(br8A)2'p5'(br8A), can be phosphorylated to the corresponding 5'-triphosphate, ppp5'A2'p5'A2'p5'A and ppp5'(br8A)2'p5'(br8A)2'p5(br8A), respectively. The extent of this conversion was about 0.5% when the concentration of 5'-diphosphate was about 10(-4) M. Thus, although previous studies have shown that the 5'diphosphate, pp5'A2'p5'A2'p5'A, can activate the 2-5A-dependent endonuclease, this may be related to a phosphorylation reaction in the crude cell extracts employed in these studies and may not represent a true ability of such a 5'-diphosphate to activate directly the endonuclease.     

Effects of leucine5 - and methionine5 - βh - endorphin on behavior and electroencephalogram in cats

Intracerebroventricular administration of leu⁵ - and met⁵ - β_h - endorphin produces sequential behavioral changes characterized by restlessness, eye fixation, head tremor, and exaggerated orienting reaction to external auditory stimuli, accompanied by EEG alterations. These changes take place during three stages. Met⁵- produces an increase in amplitude and reactivity of the theta rhythm in the hippocampus. Leu⁵- produces a masking of the theta rhythm by the appearance of spiking activity. Leu⁵- produces a loss of reactivity to visual stimuli not observed with met⁵-. The exaggerated reaction to auditory stimuli accompanied by an increased response of the reticular formation indicates a sensitivity of some mesencephalic structures (concerned with the modulation of sensory input) to both endorphins. Naloxone blockade of the subcortical (limbic) activity prominent in Stage II reveals the persistence of the first seen Stage I characteristics. These reticular-neocortical effects persist also into stage III where they are seen intermixed with the limbic effects most prominent in Stage II. This suggests the presence of two endorphin-sensitive neural systems, only one of which is Naloxone reversible, and is that which in the cat covaries with the excited, hyperattentive state rather than the sedation and immobility phase seen in the rat. This dual system is compared to that described by Jacquet (13).     

Inhibition of terminal deoxynucleotidyltransferase by (E)-5-(2-bromovinyl)-2'-deoxyuridine 5'-triphosphate

(E)-5-(2-bromovinyl)-2'-deoxyuridine 5'-triphosphate (BVdUTP), known as a specific inhibitor of herpes simplex virus (type 1)-DNA polymerase, was found to be a potent inhibitor of the activity of terminal deoxynucleotidyltransferase (TdT) from calf thymus. BVdUTP was not an efficient substrate of TdT, but it inhibited the incorporation of normal deoxynucleotide substrates in competitive fashion at the nucleotide binding site of TdT molecule. The Ki value for BVdUTP (5 microM) was much less than the Km value for dGTP (83 microM), indicating stronger affinity of the inhibitor to TdT than that of the substrate. These results indicate the usefulness of BVdUTP as a potent inhibitor of TdT for elucidation of the reaction mechanism of this enzyme.     

(5Z)-4-bromo-5-(bromomethylene)-3-butyl-2(5H)-furanone reduces corrosion from Desulfotomaculum orientis

(5Z)-4-bromo-5-(bromomethylene)-3-butyl-2(5H)-furanone (furanone) from the red marine alga Delisea pulchra was found previously to inhibit the growth, swarming and biofilm formation of Gram-positive bacteria (Ren et al., 2002, Lett Appl Microbiol 34: 293-299). In the present study, the Gram-positive sulphate-reducing bacterium (SRB), Desulfotomaculum orientis, was used to study the inhibition of mild steel corrosion due to the addition of furanone. The weight loss from batch coupon experiments incubated with 40 microg x ml(-1) furanone was reduced fivefold compared with samples that lacked furanone. Analysis of the metal surface with environmental scanning electron microscopy further confirmed the protection afforded by the addition of furanone. In agreement with the corrosion inhibition, most probable number (MPN) analysis showed that 20 and 40 microg x ml(-1) furanone inhibited 58% and 96% of the D. orientis growth respectively. Hence, furanone has the potential to inhibit microbial-induced corrosion related to Gram-positive bacteria.     

Synthesis of P-Thioadenylyl (2′-5′) Adenosine and P-Thioadenylyl (2′-5′)-P-Thioadenylyl-(2′-5′)-Adenosine

Abstract

Dimer and trimer adenylates with 2′-5′ phosphorothioate linkages were synthesized via the phosphoramidite method using p-nitrophenyl-ethyl group for phosphate protection and followed by sulfur oxidation. The various diastereoisomers were separated and characterized.     

Synthesis and antileishmanial activity of 5-(5-nitroaryl)-2-substituted-thio-1,3,4-thiadiazoles

A series of novel 2-substituted-thio-1,3,4-thiadiazoles bearing a 5-nitroaryl moiety including nitrofuran, nitrothiophene or nitroimidazole at the 5-position and a bulky residue attached to the 2-position of the thiadiazole ring were synthesised as potential antileishmanial agents. The target compounds were evaluated against the promastigote form of Leishmania major using the tetrazolium bromide salt (MTT) colorimetric assay. All test compounds exhibited high activity against L. major promastigotes with 50% inhibitory concentrations (IC₅₀) ranging from 1.11 to 3.16 μM. The structure-activity relationship study indicated that the S-pendant group attached to the 2-position of the thiadiazole ring has a high flexibility for structural alteration therefore retaining good antileishmanial activity.     

5-脂氧合酶及其抑制剂

5-脂氧合酶（5-lipoxygenase, 5-LOX）是生物体内一种重要的双加氧酶.5-LOX是催化花生四烯酸（arachidonic acid,AA）生成白三烯类（leukotrienes, LTs）的关键酶. LTs是重要的炎症介质,并且在许多疾病中发挥着重要作用.近年来,很多学者致力于5 LOX的研究,从而为5-LOX抑制剂的研发提供理论依据.本文对5-LOX的分子结构、细胞内定位、表达与活性调控及其抑制剂的研究进展进行综述.     

5-(pyridinon-1-yl)indazoles and 5-(furopyridinon-5-yl)indazoles as MCH-1 antagonists

A new series of 5-(pyridinon-1-yl)indazoles with MCH-1 antagonist activity were synthesized. Potential cardiovascular risk for these compounds was assessed based upon their interaction with the hERG potassium channel in a mini-patch clamp assay. Selected compounds were studied in a 5-day diet-induced obese mouse model to evaluate their potential use as weight loss agents. Structural modification of the 5-(pyridinon-1-yl)indazoles to give 5-(furopyridinon-5-yl)indazoles provided compounds with enhanced pharmacokinetic properties and improved efficacy.     

致倦库蚊三个几丁质酶基因CqCht5-1,CqCht5-2和CqCht5-3的分析和表达

昆虫几丁质酶5作为昆虫代谢的关键酶类之一,进化上相对保守,在昆虫的生长发育中起到关键作用.致倦库蚊广布于中国南方大部分地区,是多种病原体的传播媒介.对致倦库蚊几丁质酶5基因(CqCht5)进行深入研究,将有利于新型生物类杀虫剂的开发和研制,进而有利于预防医学工作的进行.本研究通过生物信息学方法分析了致倦库蚊三个基因即C...     

(E)-5-(2-bromovinyl)-2'-deoxyuridine-5'-triphosphate as a DNA polymerase substrate.

Time course of incorporation and the effect of 5'-triphosphate of the selective antiherpetic agent (E)-5-(2-bromovinyl)-2'-deoxyuridine (bv5dUTP) on the incorporation of dTTP and dATP into template-primers of different structure were studied in E. coli DNA polymerase I Klenow fragment enzyme-catalyzed reactions. bv5dUTP could substitute for dTTP depending on the structure of template-primer. E.g. into calf thymus DNA incorporation of bv5dUMP was around 80% of that of dTMP at 30 minutes of incubation. The analog has also inhibited dTMP incorporation, net DNA synthesis, however, was hardly affected. The substrate properties of the analog were studied with [2-14C]-labelled bv5dUTP.     

Potent inhibitory effects of the 5'-triphosphates of (E)-5-(2-bromovinyl)-2'-deoxyuridine and (E)-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil on DNA polymerase gamma

(E)-5-(2-Bromovinyl)-2'-deoxyuridine 5'-triphosphate (BrVdUTP) and (E)-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil 5'-triphosphate (BrVarafUTP), which are known as specific inhibitors of herpes simplex viral (type 1 and 2) DNA polymerase, were found to be strong inhibitors of DNA polymerase gamma from human KB and murine myeloma cells. In fact BrVdUTP and BrVarafUTP were found to be stronger inhibitors of DNA polymerase gamma than of other DNA polymerases having viral (herpes simplex virus or retrovirus) origin or cellular (eukaryotic alpha and beta, or prokaryotic) origin. The mode of inhibition of DNA polymerase gamma by BrVdUTP and BrVarafUTP was competitive with respect to dTTP, the normal substrate. Whereas BrVdUTP was an efficient substrate for DNA polymerase gamma and other DNA polymerases that were examined, BrVarafUTP failed to serve as a substrate for DNA synthesis. Ki values for BrVdUTP (40 nM) and BrVarafUTP (7 nM) with DNA polymerase gamma, as determined with (rA)n.(dT) as the template.primer, were much smaller than the Km values for dTTP (0.16 microM and 0.71 microM for murine and human DNA polymerase gamma, respectively). Thus, the affinity of BrVdUTP or BrVarafUTP for DNA polymerase gamma was much stronger than that of dTTP.