Application of 2,4,5-tris(2-pyridyl)imidazole as ‘turn-off’ fluorescence sensor for Cu(II) and Hg(II) ions and in vitro cell imaging

The 2,4,5-tris(2-pyridyl)imidazole ( L ) molecule has been evaluated as a probe for dual sensing of Hg²⁺ and Cu²⁺ ions in EtOH/HEPES buffer medium (5 mM, pH = 7.34, 1:1, v/v). Probe L shows a good sensitive and selective turn-off response in the presence of both Hg²⁺ and Cu²⁺ ions, which is comprehensible under long UV light. The probe can detect Cu²⁺ ion in the pH range 3–11 and Hg²⁺ ion in pH 6–8. The limit of detection for Cu²⁺ (0.77 μM) is well under the allowable limit prescribed by the United States Environmental Protection Agency. Two metal (Cu²⁺/Hg²⁺) ions are needed per L for complete fluorescence quenching. The probe shows marked reversibility on treatment with Na₂EDTA, making the protocol more economical for practical purposes. Paper strip coated with the L solution of EtOH can detect the presence of Cu²⁺ and Hg²⁺ ions in the sample using visible quenching of the fluorescence intensity. Density functional theory–time-dependent density functional theory (DFT–TDDFT) calculations support experimental observations, and d-orbitals of Cu²⁺/Hg²⁺ provide a nonradiative decay pathway. Cell imaging study using HDF and MDA-MB-231 cells also supported the viability of L in detecting Cu²⁺ and Hg²⁺ ions in living cells.     

Growth and Endogenous Cytokinins in Tobacco Callus as Affected by N-(2-chloro-4-pyridyl)-N′-phenylurea

The effect of N-(2-chloro-4-pyridyl)-N-phenylurea (4PU-30) on the growth and content of endogenous cytokinins of adenine type in tobacco (Nicotiana tabacum L.) callus was investigated. Biomass accumulation in calli grown on Murashige and Skoog (MS) medium with 4PU-30 was higher than that on MS medium with kinetin. The obvious presence of isopentenyladenine type cytokinins and traces of zeatin type cytokinins supposes modification in the endogenous cytokinin metabolism of the tobacco callus grown on 4PU-30.     

Synthesis, structure and characterization of new complexes [Fe2(μ-OMe)2(PAP)(X)4] (PAP= 1,4-di(2-pyridyl)aminophthalazine, X=Cl, OAc) and their oxidation catalysis

Two dinuclear iron(III) complexes with tetradentate N-donor ligand 1,4-di(2^′-pyridyl)aminophthalazine (PAP), [Fe₂(μ-OMe)₂(PAP)Cl₄] (2) and [Fe₂(μ-OMe)₂(PAP)(OAc)₄] (3) were prepared and characterized. Single crystal X-ray molecular structure of [Fe₂(μ-OMe)₂(PAP)Cl₄] · 2MeOH have been elucidated. The six-coordinate iron atoms are in distorted octahedral environment bridged by the oxygen atoms of two methoxy groups and the PAP ligand. The Mössbauer spectra of both complexes show one quadrupole doublet and the isomer shift and quadrupole splitting values indicate the presence of octahedral high-spin Fe^III ions. Complex 2 showed catalytic activity for alkane oxidation with hydrogen peroxide.     

New assembled Fe-trans-1,2-bis(4-pyridyl)ethylene-NCS(NCSe) complexes - hydrogen bonded and π-π interacted structure and grid structure enclathrating ligand

Reaction of FeSO₄ · 7H₂O with trans-1,2-bis(4-pyridyl)ethylene (tvp) and NaNCS in the mixed solvent of water and ethanol gave rise to the formation of different coordination polymers. One (Fe(tvp)₂(NCS)₂(H₂O)₂) is hydrogen bonded and π-π interacted structure, while the other ([Fe(tvp)₂(NCS)₂][0.5(tvp · 2EtOH)]) is 2D grid structure, which enclathrates tvp · 2EtOH. This enclathrated tvp · 2EtOH interacts with the two 2D grid sheets to form 3D structure. The same reaction was carried out with KNCSe instead of NaNCS (Fe(tvp)₂(NCSe)₂(H₂O)₂). ⁵⁷Fe Mössbauer spectra revealed that all the present assembled complexes are in the Fe^II high-spin state. The dissociation behavior of enclathrated molecule and ligand was investigated by TG, and the resultant electronic state of iron atom was studied by ⁵⁷Fe Mössbauer spectroscopy.     

Mono- and binuclear copper(II) complexes containing di(2-pyridyl)sulfide (DPS) as chelating ligand: Spectroscopic characterization and crystal structures of [Cu(DPS)(H2O)Cl2] · H2O and [{Cu(DPS)Cl}2μ-(Cl)2]

The complexes [Cu(DPS)(H₂O)Cl₂] · H₂O (1a) and [{Cu(DPS)Cl}₂μ-(Cl)₂] (1b) where DPS = Di(2-pyridyl)sulfide have been synthesized and characterized using elemental analysis, thermal analysis (TG/DSC), vibrational and electronic spectroscopies as well as electron paramagnetic resonance (EPR). Additionally, the crystal and molecular structures of both compounds have been determined by X-ray diffraction techniques.     

Expansion during early apple fruit development induced by auxin and N-(2-chloro-4-pyridyl)-N′-phenylurea: Effect on cell wall hemicellulose

Expansion in apple fruit (Malus domestica Borkh. cv. Braeburn) during early development was induced by injecting 2,4-dichlorophenoxyacetic acid (2,4-D) through the calyx of the fruit and by dipping the apples in N-(2-chloro-4-pyridyl)-N-phenylurea (CPPU). Cell wall composition was analysed, focusing on the hemicellulose fraction containing xyloglucan, a polysaccharide believed to play an important role in cell expansion. Changes were observed in the yields of the cell wall fractions of the fruit treated with either 2,4-D or CPPU, although the monosaccharide composition of the fractions exhibited few differences. There was no decrease in the molecular weight of the xyloglucan from treated fruit. These results are discussed in terms of current cell wall expansion mechanisms.     

β-Glucosidase 2 (GBA2) Activity and Imino Sugar Pharmacology

β-Glucosidase 2 (GBA2) is an enzyme that cleaves the membrane lipid glucosylceramide into glucose and ceramide. The GBA2 gene is mutated in genetic neurological diseases (hereditary spastic paraplegia and cerebellar ataxia). Pharmacologically, GBA2 is reversibly inhibited by alkylated imino sugars that are in clinical use or are being developed for this purpose. We have addressed the ambiguity surrounding one of the defining characteristics of GBA2, which is its sensitivity to inhibition by conduritol B epoxide (CBE). We found that CBE inhibited GBA2, in vitro and in live cells, in a time-dependent fashion, which is typical for mechanism-based enzyme inactivators. Compared with the well characterized impact of CBE on the lysosomal glucosylceramide-degrading enzyme (glucocerebrosidase, GBA), CBE inactivated GBA2 less efficiently, due to a lower affinity for this enzyme (higher K_I) and a lower rate of enzyme inactivation (k_inact). In contrast to CBE, N-butyldeoxygalactonojirimycin exclusively inhibited GBA2. Accordingly, we propose to redefine GBA2 activity as the β-glucosidase that is sensitive to inhibition by N-butyldeoxygalactonojirimycin. Revised as such, GBA2 activity 1) was optimal at pH 5.5–6.0; 2) accounted for a much higher proportion of detergent-independent membrane-associated β-glucosidase activity; 3) was more variable among mouse tissues and neuroblastoma and monocyte cell lines; and 4) was more sensitive to inhibition by N-butyldeoxynojirimycin (miglustat, Zavesca®), in comparison with earlier studies. Our evaluation of GBA2 makes it possible to assess its activity more accurately, which will be helpful in analyzing its physiological roles and involvement in disease and in the pharmacological profiling of monosaccharide mimetics.     

2-Picolinic acid and benzoic acid from di-2-pyridyl ketone and acetophenone: A case of two copper catalysed Baeyer-Villiger rearrangements?

The synthesis and crystal structure elucidation of two novel polymeric copper(II) complexes has led us to propose a mechanism for the formation of 2-picolinic acid (pic) from di-2-pyridyl ketone (dpk) and benzoic acid from acetophenone. During studies into the interaction of copper ions with the dpk-acetophenone system, two complexes Na₂(NCS)₂(H₂O)[Cu(pic)₂] (1) and Na₂(H₂O)₂[Cu(pic)₂(NCS)₂] (2) which contain pic coordinated to copper were isolated. The occurrence of (1) and (2) has led us to consider the Baeyer-Villiger rearrangement as a possible mechanism for the formation of (1) and (2).     

Preparation of (±)-2-(2,3-2H2)Jasmonic Acid and Its Methyl Ester,Methyl (±)-2-(2,3-2H2)Jasmonate

For use as the internal standards in a quantitative analysis of natural jasmonic acid (JA) and methyl jasmonate (JAMe) by gas chromatography-mass spectrometry-selected ion monitoring, (±)-2-(2,3–²H₂)JA and its methyl ester, (±)-2-(2,3–²H₂)JAMe, were efficiently prepared from 2-(2–pentyl)-2-cyclopentenone through catalytic semi-deuteriogenation of acetylenic intermediates with deuterium gas in pyridine.     

9-(2-Deoxy-ß-D-xylofuranosyl)adenine and 1-(2-Deoxy-ß-D-xylofuranosyl)thymine: Phosphorylation and Stability

Abstract

Phosphorylation of 1-(2-deoxy-β-D-xylofuranosyl)thymine (1) or 9-(2-deoxy-β-D-xylofuranosyl)adenine (3) with phosphoryl chloride gives the cyclic 3′,5′-phosphates (2 and 4a) but not the 5′-monophosphates 8a or 8b. The latter are obtained by phosphorylation of the 3′-0-benzoylated 2′-deoxy-β-D-xylonucleosides (7a, b) and subsequent base-catalyzed removal of the benzoyl groups. Compound 3, as the parent dA, depurinates in acidic medium, a reaction which is facilitated in the case of the N⁶-benzoyl derivative 9b and reduced after the introduction of an amidine protecting group. N-Glycosylic bond hydrolysis of 2′-deoxy-β-D-xylofuranosyl nucleosides is enhanced by a factor of two compared to 2′-deoxy-β-D-ribofuranosyl nucleosides.     

Synthesis of (2′S)-1-(2-C-Azidomethyl-2-deoxy and 2-C-Cyanomethyl-2-deoxy-β-D-arabinofuranosyl)cytosines

Abstract

2′-C-Cyanomethyl-2′-deoxy-arabinosylcytosine 3 and 2′-C-azidomethyl-2′-deoxy-arabinosylcytosine 4 were synthesized from uridine. The antineoplastic activities of these compounds were evaluated.     

Stereoselective Synthesis of 1- and 2-O-α-d-Cellotriosyl-3-deoxy-2(R)- and 2(S)-glycerols Related to Rhynchosporoside

The stereoselective synthesis of 1- and 2-O-α-d-cellotriosyl-3-deoxy-2(R)- and 2(S)-glycerols, which determined the structure of rhynchosporoside produced by Rhynchosporium secalis, and their phytotoxicity toward the host plant (Hordeum vulgare) are described in detail.     

5-(2-Pyrrolidinyl)oxazolidinones and 2-(2-pyrrolidinyl)benzodioxanes: Synthesis of all the stereoisomers and α4β2 nicotinic affinity

The four stereoisomers of 2-oxazolidinone 5-substituted with 1-methyl-2-pyrrolidinyl (1), of 1,4-benzodioxane 2-substituted with the same residue (2) and of the nor-methyl analogue of this latter (2a) were synthesized as candidate nicotinoids. Of the 12 compounds, two N-methylated pyrrolidinyl-benzodioxane stereoisomers, namely those with the same relative configuration at the pyrrolidine stereocentre as (S)-nicotine, bind at α4β2 nicotinic acetylcholine receptor with submicromolar affinity. Consistently with the biological data, docking analysis enlightens significant differences in binding site interactions not only between 1 and 2, but also between 2 and 2a and between the stereoisomers of 2 accounting for the critical role played, in the case of the pyrrolidinyl-benzodioxanes, by the chirality of both the stereolabile and stereostable stereogenic atoms, namely the protonated tertiary nitrogen and the two asymmetric carbons.     

Physicochemical and biological properties of 2-O-α-D-galactosyl-cyclomaltohexaose (α-cyclodexterin) and -cyclomaltoheptaose (β-cyclodextrin)

The physicochemical and biological properties of the new branched cyclomaltooligosaccharides (cyclodextrins; CDs), 2-O-α-D-galactosyl-cyclomaltohexaose (2-O-α-D-galactosyl-α-cyclodextrin, 2-Gal-αCD) and 2-O-α-D-galactosyl-cyclomaltoheptaose (2-O-α-D-galactosyl-β-cyclodextrin, 2-Gal-βCD), were investigated. The formation of inclusion complexes of 2-Gal-CDs with various kinds of guest compounds (clofibrate, cholesterol, cholecalciferol, digitoxin, digitoxigenin, and prostaglandin A(1)) was examined by a solubility method, and the results were compared with those of non-branched CDs and other 6-O-glycosyl-CDs such as 6-O-α-D-galactosyl-CDs, 6-O-α-D-glucosyl-CDs, and 6-O-α-maltosyl-CDs. The inclusion abilities of 2-Gal-αCD for clofibrate and prostaglandin A(1), and 2-Gal-βCD for clofibrate, cholecalciferol, cholesterol, and digitoxigenin were markedly weaker than those of non-branched CD and other 6-O-glycosyl-CDs in each series, probably because of a steric hindrance caused by the α-(1→2)-galactoside linkage. The hemolytic activities of 2-Gal-CDs on human erythrocytes were the lowest among each CD series, and the compounds showed negligible cytotoxicity towards Caco-2 cells up to at least 100mM.     

Combination of Azidothymidine (AZT) and (E)-5-(2-Bromovinyl)-2′-deoxyuridine (BVDU) Inhibits the Replication of Herpes Simplex Virus Type 1 (HSV-1) and Type 2 (HSV-2) and Varicella Zoster Virus (VZV) Strains That Are Deficient in the Expression of the Viral Thymidine Kinase (tk)

Abstract

Combinations of high concentrations of AZT with BVDU, acyclovir (ACV) or ganciclovir (GCV) show antagonism against TK⁺ HSV-1, but not TK⁺ VZV strains, in cell cultures. When BVDU and AZT were used in combination against TK^? HSV-1, TK^? HSV-2 and TK^? VZV strains, a pronounced inhibition of viral replication was observed. This potentiating effect was not seen if AZT was combined with ACV or GCV.     

Stereospecific Synthesis and Anti-HIV Activity of (Z)2′- and (E)3′-Deoxy-2′(3′)-C-(chloromethylene) Pyrimidine Nucleosides

Abstract

Reaction of 1-[2,5(and 3,5)-di-O-trityl-β-D-erythro-pentofuran-3 (and 2)-ulosyl]uracil derivatives 5 and 6 with (chloromethyl)triphenylphosphorane resulted in the stereoselective formation of (E)-3′- and (Z)-2′-chloromethylene derivatives 7 (69%) and 8 (53%), respectively, deprotection of which gave 9 and 10. Transformation of the uracil nucleoside 7 into cytosine one followed by deprotection yielded 12. The latter was converted into the arabinoside 14. The fully deprotected chloromethylene nucleosides were tested for their activity against HIV-1 and HIV-2.     

Niemann–Pick C2 (NPC2) and intracellular cholesterol trafficking

Cholesterol is an important precursor for numerous biologically active molecules, and it plays a major role in membrane structure and function. Cholesterol can be endogenously synthesized or exogenously taken up via the endocytic vesicle system and subsequently delivered to post-endo/lysosomal sites including the plasma membrane and the endoplasmic reticulum. Niemann–Pick C (NPC) disease results in the accumulation of exogenously-derived cholesterol, as well as other lipids, in late endosomes and lysosomes (LE/LY). Identification of the two genes that underlie NPC disease, NPC1 and NPC2, has focused attention on the mechanisms by which lipids, in particular cholesterol, are transported out of the LE/LY compartment. This review discusses the role of the NPC2 protein in cholesterol transport, and the potential for concerted action of NPC1 and NPC2 in regulating normal intracellular cholesterol homeostasis.