The electron affinities of deprotonated adenine, guanine, cytosine, uracil, and thymine

Electron attachment rates and gas phase acidities for the canonical tautomers of the nucleobases and electron affinities for thymine, deprotonated thymine, and cytosine are reported The latter are from a new analysis of published photoelectron spectra. The values for deprotonated thymine are (all in eV) keto-N1-H, 3.327(5); enol-N3-H, 3.250(5), enol-C2OH, 3.120(5) enol-N1-H, 3.013(5), and enol-C4OH,3.123(5). The values for deprotonated cytosine, keto-N1-H, 3.184(5); trans-NH-H, 3.008(5); cis-NH-H, 3.039(5); and enol-N1-H, 2.750(5) and enol-O-H, 2.950(5). The gas phase acidities from these values are obtained from these values using experimental or theoretical calculations of bond dissociation energies. Kinetic and thermodynamic properties for thermal electron attachment to thymine are obtained from mass spectrometric data. We report an activation energy of 0.60 eV and electron affinity of thymine, 1.0(1) eV.     

The Electron Affinities of Deprotonated Adenine,Guanine, Cytosine,Uracil, and Thymine

Electron attachment rates and gas phase acidities for the canonical tautomers of the nucleobases and electron affinities for thymine, deprotonated thymine, and cytosine are reported The latter are from a new analysis of published photoelectron spectra. The values for deprotonated thymine are (all in eV) keto-N1-H, 3.327(5); enol-N3-H, 3.250(5), enol-C2OH, 3.120(5) enol-N1-H, 3.013(5), and enol-C4OH,3.123(5). The values for deprotonated cytosine, keto-N1-H, 3.184(5); trans-NH-H, 3.008(5); cis-NH-H, 3.039(5); and enol-N1-H, 2.750(5) and enol-O-H, 2.950(5). The gas phase acidities from these values are obtained from these values using experimental or theoretical calculations of bond dissociation energies. Kinetic and thermodynamic properties for thermal electron attachment to thymine are obtained from mass spectrometric data. We report an activation energy of 0.60 eV and electron affinity of thymine, 1.0(1) eV.     

Chemoenzymatic synthesis of 2-azidoethyl-ganglio-oligosaccharides GD3, GT3, GM2, GD2, GT2, GM1, and GD1a

We have synthesized several ganglio-oligosaccharide structures using glycosyltransferases from Campylobacter jejuni. The enzymes, alpha-(2-->3/8)-sialyltransferase (Cst-II), beta-(1-->4)-N-acetylgalactosaminyltransferase (CgtA), and beta-(1-->3)-galactosyltransferase (CgtB), were produced in large-scale fermentation from Escherichia coli and further characterized based on their acceptor specificities. 2-Azidoethyl-glycosides corresponding to the oligosaccharides of GD3 (alpha-D-Neup5Ac-(2-->8)-alpha-D-Neup5Ac-(2-->3)-beta-D-Galp-(1-->4)-beta-D-Glcp-), GT3 (alpha-D-Neup5Ac-(2-->8)-alpha-D-Neup5Ac-(2-->8)-alpha-D-Neup5Ac-(2-->3)-beta-D-Galp-(1-->4)-beta-D-Glcp-), GM2 (beta-D-GalpNAc-(1-->4)-[alpha-D-Neup5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-Glcp-), GD2 (beta-D-GalpNAc-(1-->4)-[alpha-D-Neup5Ac-(2-->8)-alpha-D-Neup5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-Glcp-), GT2 (beta-D-GalpNAc-(1-->4)-[alpha-D-Neup5Ac-(2-->8)-alpha-D-Neup5Ac-(2-->8)-alpha-D-Neup5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-Glcp-), and GM1 (beta-D-Galp-(1-->3)-beta-D-GalpNAc-(1-->4)-[alpha-D-Neup5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-Glcp-) were synthesized in high yields (gram-scale). In addition, a mammalian alpha-(2-->3)-sialyltransferase (ST3Gal I) was used to sialylate GM1 and generate GD1a (alpha-D-Neup5Ac-(2-->3)-beta-D-Galp-(1-->3)-beta-D-GalpNAc-(1-->4)-[alpha-D-Neup5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-Glcp-) oligosaccharide. We also cloned and expressed a rat UDP-N-acetylglucosamine-4'epimerase (GalNAcE) in E. coli AD202 cells for cost saving in situ conversion of less expensive UDP-GlcNAc to UDP-GalNAc.     

Mechanisms of the vasorelaxant effect of 1, 5-dihydroxy-2, 3-dimethoxy-xanthone, an active metabolite of 1-hydroxy-2, 3, 5-trimethoxy-xanthone isolated from a Tibetan herb, Halenia elliptica, on rat coronary artery

1, 5-Dihydroxy-2, 3-dimethoxy-xanthone (HM-5) is one of the naturally-occurring xanthones of a Tibetan medicinal herb Halenia elliptica. Recently, it has been shown that HM-5 is one of the phase I metabolites of 1-hydroxy-2, 3, 5-trimethoxy-xanthone (HM-1), the major active component of H. elliptica with potent vasorelaxant actions. This study investigated the vasorelaxant effect of HM-5 and its mechanism(s). HM-5 (0.35-21.9 microM) produced a concentration-dependent relaxation in rat coronary artery rings pre-contracted with 1 microM 5-hydroxytryptamine (5-HT), with an EC(50) of 4.40+/-1.08 microM. Unlike HM-1, the effect of HM-5 was endothelial-independent such that removal of the endothelium did not affect its vasodilator potency. Nitric oxide synthase (NOS) inhibitor N(omega)-nitro-l-arginine methyl ester (l-NAME, 100 microM), the soluble guanylate cyclase inhibitor 1H-[1,2,4] oxadiazolo [4,3-alpha] quinoxalin-1-one (ODQ, 10 microM) did not affect the vasodilatory effects of HM-5, thus confirming the non-involvement of endothelium related mechanisms. In endothelium-denuded coronary artery rings, the vasorelaxant effect of HM-5 was inhibited by a potassium channel blocker, TEA (10 mM), and 4-aminopyridine (4-AP, a K(v) blocker; 1 mM) but not by other K+ channel blockers such as iberiotoxin (100 nM), barium chloride (100 microM) and glibenclamide (10 microM). The involvement of Ca2+ channel was studied in artery rings pre-incubated with Ca2+-free buffer (intact endothelium or endothelium-denuded) and primed with 1 microM 5-HT or 60 mM KCl prior to the addition of CaCl2 to elicit contraction. In the 5-HT-primed preparations, HM-5 (34.7 microM) significantly inhibited the CaCl(2)-induced vasoconstriction (89.9% inhibition in intact endothelium artery rings; 83.3% inhibition in endothelium-denuded rings). In the KCl-primed preparations, HM-5 (34.7 microM) produced a 34% inhibition in endothelium-denuded rings. The same concentration of HM-5 inhibited (by 62.3%) the contractile response to 10 microM phorbol 12, 13-diacetate (PDA), a protein kinase C activator, in Ca2+-free solutions. Taken together, this study showed that the mechanisms of the vasorelaxant effects of HM-5 were distinctly different from those of its parent drug HM-1. The vasorelaxant effect of HM-5 was mediated through opening of potassium channel (4-AP) and altering intracellular calcium by partial inhibition of Ca2+ influx through L-type voltage-operated Ca2+ channels and intracellular Ca2+ stores.     

Synthesis and biological evaluation of some 5-nitro- and 5-amino derivatives of 2'-deoxycytidine, 2',3'-dideoxyuridine, and 2',3'-dideoxycytidine

In this article, we describe the synthesis of 5-nitro-1-(2-deoxy-alpha-D-erythro-pentofuranosyl)cytosine (4alpha), 5-nitro-1-(2-deoxy-beta-D-erythro-pentofuranosyl)cytosine (4beta), 5-amino-1-(2-deoxy-alpha-D-erythro-pentofuranosyl)cytosine (5alpha), 5-nitro-1-(2-deoxy-beta-D-erythro-pentofuranosyl)cytosine (5beta), 5-nitro-1-(2,3-dideoxy-beta-D-ribofuranosyl)uracil (6beta), 5-amino-1-(2,3-dideoxy-alpha,beta-D-ribofuranosyl)uracil (7), 5-nitro-1-(2,3-dideoxy-alpha,beta-D-ribofuranosyl)cytosine (8) and 5-amino-1-(2,3-dideoxy-beta-D-ribofuranosyl)cytosine (9beta). The prepared compounds were tested for their activity against HIV and HBV viruses, but they did not show significant activity.     

A method for concurrent measurement of picomole quantities of acetylcholine, choline, dopamine, norepinephrine, serotonin, 5-hydroxytryptophan, 5-hydroxyindoleacetic acid, tryptophan, tyrosine, glycine, aspartate, glutamate, alanine, and gamma-aminobutyric acid in single tissue samples from different areas of rat central nervous system.

A rapid and sensitive method for separation and concurrent assay of 14 compounds at the picomole level in individual rat brain parts is described. The putative amino acid neurotransmitters (aspartate, γ-aminobutyric acid, glutamate, and glycine) are extracted from a 20–30 mg portion of the tissue with 5% TCA and assayed as their respective DNP-amino acid methyl ester derivatives by glc. Four other putative neurotransmitters (acetylcholine, dopamine, norepinephrine, and serotonin) and some of their precursors and metabolites (choline, tryptophan, 5-hydroxytryptophan, 5-hydroxyindoleacetic acid, and tyrosine) are extracted in 1n formic acid-acetone (v/v:15/85) from the remaining tissue. The lipids are removed with a heptane-chloroform (v/v:8/1) wash and the aqueous phase is dried at 37°C under N₂. The dried extract is dissolved in water (pH 4). With one portion of this solution, acetylcholine and choline are assayed using a radioenzymatic method whereas with the rest, dopamine, norepinephrine, serotonin, 5-hydroxyindoleacetic acid, 5-hydroxytryptophan, tryptophan, and tyrosine are separated with three ion exchange resins arranged in tandem. These compounds are assayed fluorometrically with modified microadaptations of previously reported methods.     

The Expression of Cdk5, p35, p39, and Cdk5 Kinase Activity in Developing, Adult, and Aged Rat Brains

The expression of cyclin-dependent kinase 5 (Cdk5) and its regulatory subunits, p35 and p39, was investigated in rat brain from embryonic day 12 (E12) to postnatal 18 months (18M). The Cdk5 protein levels increased from E12 to postnatal day 7 (P7) and remained at this level until 18M. The Cdk5 kinase activity and the levels of both p35 mRNA and protein were low at E12, became prominent at E18-P14 but then decreased in the adult and aged rat brains of 3M to 18M. In comparison, the expression pattern of p39 appeared to have an inverse relationship to that of Cdk5 and p35. In regional distribution studies, p35 protein levels and Cdk5 kinase activity were significantly higher in the cerebral cortex and hippocampus, but lower in the cerebellum and striatum. These results suggested that Cdk5, p35 and p39 might have region-specific and developmental stage-specific functions in rat brain.     

磷酸二酯酶5（PDE5）在人增生前列腺移行带中的表达及分布

目的:探讨磷酸二酯酶5在人前列腺移行带组织中的表达与分布。方法:应用免疫组化SP法,选择前列腺增生患者34例,检测PDE5表达及分布。结果:34例标本中PDE5均呈阳性表达。PDE5在前列腺移行带的腺组织上皮普遍呈中等表达,间质部分弱表达。结论:PDE5在人增生前列腺组织中分布,但分布不均,表明不同PDE5可能行使不同的功能。     

Total synthesis of (+)-macrosphelides A,C, E,F, and G based on enzymatic function

The total synthesis of (+)-macrosphelide A (1) (18.5% overall yield in 11 steps), (+)-macrosphelide C (2) (25% overall yield in 9 steps), (+)-macrosphelide E (3) (23.9% overall yield in 11 steps), (+)-macrosphelide F (4) (20% overall yield in 9 steps), and (+)-macrosphelide G (5) (22% overall yield in 9 steps) was achieved from a chemoenzymatic reaction product (4R,5S)-4-benzyloxy-5-hydroxy-2(E)-hexenoate 10.     

Studies towards the large scale chemical synthesis of the precursors of ribonucleosides-3',4',5',5'-2H4 and -2',3',4',5',5'-2H5

A summary delineating the large scale synthetic studies to prepare labeled precursors of ribonucleosides-3',4',5',5'-2H4 and -2',3',4',5',5'-2H5 from D-glucose is presented. The recycling of deuterium-labeled by-products has been devised to give a high overall yield of the intermediates and an expedient protocol has been elaborated for the conversion of 3-O-benzyl-alpha,beta-D-allofuranose-3,4-d2 6 to 1-O-methyl-3-O-benzyl-2-O-t-butyldimethylsilyl-alpha,beta-D-ribofuranose-3,4,5,5'-d4 16 (precursor of ribonucleosides-3',4',5',5'-2H4) or to 1-O-methyl-3,5-di-O-benzyl-alpha,beta-D-ribofuranose-3,4,5,5'-d4 18 (precursor of ribonucleosides-3',4',5',5'-2H4).     

Regioselective synthesis of 1I,1II,5I,5II,6I,6I,6II,6II-2H8-cellobiose

Partially deuteriated 1,5,6,6-(2)H(4)-d-glucose and 1(I),1(II),5(I),5(II),6(I),6(I),6(II),6(II)-(2)H(8)-d-cellobiose were synthesized in high yields and on a large scale from d-glucose. (2)H enrichment at C-5 and C-6 of each glucopyranosyl unit in excess of 85% and 90%, respectively, was realized by (1)H-(2)H exchange in (2)H(2)O containing deuteriated Raney Ni. Nucleophilic addition of LiAlD(4) to 5,6,6-(2)H(3)-2,3,4,6-tetra-O-benzyl-d-gluconolactone led to a 98% (2)H enrichment at C-1. Deuteriated cellobiose is of interest as building block for the synthesis of a model compound of cellulose I.     

Novel, flexible, and conformationally defined analogs of gepirone: synthesis and 5-HT1A, 5-HT2A, and D2 receptor activity

Novel, flexible arylpiperazine gepirone analogs (1a-3a) with a mixed 5-HT1A/5-HT2A receptor profile, low D2 receptor affinity, and agonistic (2a) or partial agonistic (1a, 3a) activity toward 5-HT1A receptor sites were synthesized. Their conformationally restricted counterparts (1b-3b) were selective 5-HT1A ligands (over 5-HT2A and D2 receptors), which turned out to be agonists (2b, 3b), or partial agonist (1b) of 5-HT1A receptors.     

Simultaneous Determination of 3,4-Dihydroxyphenylalanine, 5-Hydroxytryptophan, Dopamine, 4-Hydroxy-3-Methoxyphenylalanine, Norepinephrine, 3,4-Dihydroxyphenylacetic Acid, Homovanillic Acid, Serotonin, and 5-Hydroxyindoleacetic Acid in Rat Cerebrospinal Fluid and Brain by High-Performance Liquid Chromatography with Electrochemical Detection

A method using reversed-phase ion-pair high-performance liquid chromatography with electrochemical detection for the simultaneous determination of tryptophan (TRP), 3,4-dihydroxyphenylalanine (DOPA), and their metabolites in whole brain, small-brain parts, and cerebrospinal fluid of rats has been developed. The sample preparation requires only homogenization in perchloric acid and centrifugation before injection onto the column. With a LiChrosorb RP-18 (10 micrometer) column and a mobile phase consisting of a phosphate (NaH2PO4, 0.1 M)-methanol mixture with octylsulfonate (2.6 x 10(-3) M) at pH 3.35 and 26 degrees C, the separation of DOPA, dopamine, norepinephrine, 3,4-dihydroxyphenylacetic acid, homovanillic acid, 4-hydroxy-3-methoxyphenylalanine, TRP, 5-hydroxytryptophan (5-HTP), serotonin, and 5-hydroxyindoleacetic acid was achieved. The method has been applied to study the effect of alpha-monofluoromethyldopa alone and in combination with L-DOPA or L-5-HTP, on the catechol and 5-OH indole levels in brain and CSF of the rat.     

Aldose reductase inhibitors: flavonoids, alkaloids, acetophenones, benzophenones, and spirohydantoins of chroman

The inhibitory activity of various compounds, including 12 flavonoids, 10 alkaloids, 15 benzophenones, 5 acetophenones, and 7 spirohydantoins of chroman, was tested on rabbit lens aldose reductase, an enzyme involved in complications of diabetes. Almost all compounds tested were found to inhibit the enzyme at low concentrations (10(-5) M). The most potent inhibitor was 2R,4S-6-chloro-2-methylspiro(chroman-4,4'-imidazo-lidine+ ++)-2',5'-dione with an I50 value of 4.7 x 10(-8) M; other spirohydantoins showed similar potency. Polyhydroxybenzophenones were also potent inhibitors with an I50 value of about 10(-7) M. The possible structure-inhibitory activity relationships of the compounds tested are discussed.     

Synthesis of 3 alpha,6 beta,7 alpha,12 beta- and 3 alpha,6 beta,7 beta,12 beta-tetrahydroxy-5 beta-cholanoic acids.

Chemical synthesis of 3 alpha,6 beta,7 alpha,12 beta- and 3 alpha,6 beta,7 beta,12 beta-tetrahydroxy-5 beta-cholan-24-oic acids is described. 3 alpha,12 beta-Dihydroxy-5 beta-chol-6-en-24-oic acid used as the starting material in the synthesis was prepared via oxidation of 3 alpha,12 alpha-dihydroxy-5 beta-chol-6-en-24-oic acid 3-hemisuccinate at C-12 followed by reduction with potassium/tertiary amyl alcohol. alpha-Epoxidation of the ester diacetate of 3 alpha,12 beta-dihydroxy-5 beta-chol-6-en-24-oic acid with m-chloroperbenzoic acid followed by cleavage of the epoxide with acetic acid and alkaline hydrolysis yielded 3 alpha,6 beta,7 alpha,12 beta-tetrahydroxy-5 beta-cholan-24-oic acid (overall yield 25%). N-Methylmorpholine-N-oxide-catalyzed osmium tetroxide oxidation of the ester diacetate of 3 alpha,12 beta-dihydroxy-5 beta-chol-6-en-24-oic acid followed by alkaline hydrolysis yielded 3 alpha,6 beta,7 beta,12 beta-tetrahydroxy-5 beta-cholan-24-oic acid (overall yield 33%). The structures of the synthesized bile acids were confirmed from their proto nuclear magnetic resonance and mass spectral fragmentation patterns.