Selective recognition of fluoride and acetate by a newly designed ruthenium framework: experimental and theoretical investigations

An effective anion sensor, [Ru(II)(bpy)(2)(H(2)L(-))](+) (1(+)), based on a redox and photoactive {Ru(II)(bpy)(2)} moiety and a new ligand (H(3)L = 5-(1H-benzo[d]imidazol-2-yl)-1H-imidazole-4-carboxylic acid), has been developed for selective recognition of fluoride (F(-)) and acetate (OAc(-)) ions. Crystal structures of the free ligand, H(3)L and [1](ClO(4)) reveal the existence of strong intramolecular and intermolecular hydrogen bonding interactions. The structure of [1](ClO(4)) shows that the benzimidazole N-H of H(2)L(-) is hydrogen bonded with the pendant carboxylate oxygen while the imidazole N-H remains free for possible hydrogen bonding interaction with the anions. The potential anion sensing features of 1(+) have been studied by different experimental and theoretical (DFT) investigations using a wide variety of anions, such as F(-), Cl(-), Br(-), I(-), HSO(4)(-), H(2)PO(4)(-), OAc(-) and SCN(-). Cyclic voltammetry and differential pulse voltammetry established that 1(+) is an excellent electrochemical sensor for the selective recognition of F(-) and OAc(-) anions. 1(+) is also found to be a selective colorimetric sensor for F(-) or OAc(-) anions where the MLCT band of the receptor at 498 nm is red shifted to 538 nm in the presence of one equivalent of F(-) or OAc(-) with a distinct change in colour from reddish-orange to pink. The binding constant between 1(+) and F(-) or OAc(-) has been determined to be logK = 7.61 or 7.88, respectively, based on spectrophotometric titration in CH(3)CN. The quenching of the emission band of 1(+) at 716 nm (λ(ex) = 440 nm, Φ = 0.01 at 298 K in CH(3)CN) in the presence of one equivalent of F(-) or OAc(-), as well as two distinct lifetimes of the quenched and unquenched forms of the receptor 1(+), makes it also a suitable fluorescence-based sensor. All the above experiments, in combination with (1)H NMR, suggest the formation of a 1:1 adduct between the receptor (1(+)) and the anion (F(-) or OAc(-)). The formation of 1:1 adduct {[1(+)·F(-)] or [1(+)·OAc(-)]} has been further evidenced by in situ ESI-MS(+) in CH(3)CN. Though the receptor, 1(+), is comprised of two N-H protons associated with the coordinated H(2)L(-) ligand, only the free imidazole N-H proton participates in the hydrogen bonding interactions with the incoming anions, while the intramolecularly hydrogen bonded benzimidazole N-H proton remains intact as evidenced by the crystal structure of the final product (1). The hydrogen bond mediated anion sensing mechanism, over the direct deprotonation pathway, in 1(+) has been further justified by a DFT study and subsequent NBO analysis.     

Synthesis and Structural Characterization of New Divanada‐ and Diniobaboranes Containing Chalcogen Atoms

The reaction of [Cp_nMCl_4?x] (M=V: n=2, x=2; M=Nb: n=1, x=0; Cp=η⁵‐C₅H₅) with LiBH₄ ? THF followed by thermolysis in the presence of dichalcogenide ligands E₂R₂ (E=S, Te; R=2,6‐(tBu)₂‐C₆H₂OH, Ph) and 2‐mercaptobenzothiazole (C₇H₅NS₂) yielded dimetallaheteroboranes [{CpV(μ‐TePh)}₂(μ₃‐Te)BH ? thf] ( 1 ), [(CpV)₂(BH₃S)₂] ( 2 ), [(CpNb)₂B₄H₁₀S] ( 3 ), [(CpNb)₂B₄H₁₁S(tBu)₂C₆H₂OH] ( 4 ), and [(CpNb)₂B₄H₁₁TePh] ( 5 ). In cluster 1 , the V₂BTe atoms define a tetrahedral framework in which the boron atom is linked to a THF molecule. Compound 2 can be described as a dimetallathiaborane that is built from two edge‐fused V₂BS tetrahedron clusters. Cluster 3 can be considered as an edge‐fused cluster in which a trigonal‐bipyramidal unit (Nb₂B₂S) has been fused with a tetrahedral core (Nb₂B₂) by means of a common Nb₂ edge. In addition, thermolysis of an in‐situ‐generated intermediate that was produced from the reaction of [Cp₂VCl₂] and LiBH₄ ? THF with excess BH₃ ? THF yielded oxavanadaborane [(CpV)₂B₃H₈(μ₃‐OEt)] ( 6 ) and divanadaborane cluster [(CpV)₂B₅H₁₁] ( 7 ). Cluster 7 exhibits a nido geometry with C_2v symmetry and it is isostructural with [(Cp*M)₂B₅H_9+n] (M=Cr, Mo, and W, n=0; M=Ta, n=2; Cp*=η⁵‐C₅Me₅). All of these new compounds have been characterized by ¹H NMR, ¹¹B NMR, and ¹³C NMR spectroscopy and elemental analysis and the structural types were established unequivocally by crystallographic analysis of compounds  1 – 4 , 6 , and 7 .     

Synthesis of functionalized and fused furans and pyrans from the Morita–Baylis–Hillman acetates of nitroalkenes

The Morita–Baylis–Hillman (MBH) acetates derived from nitroalkenes and ethyl glyoxylate have been transformed in one pot at room temperature to highly fused and functionalized furans and pyrans in good to excellent yield. The reaction involves a cascade Michael–oxa-Michael addition of β-dicarbonyl compounds to the MBH acetates in the presence of an amine base such as DABCO. An unusual switching of selectivity in the oxa-Michael addition from 5-exo-trig to 6-endo-trig was observed when the β-dicarbonyl compound was changed from acyclic or six-membered ring cyclic to five-membered ring cyclic system.     

Synthesis and studies of covalently linked meso-furyl boron-dipyrromethene-ferrocene conjugates

Four meso-furyl BODIPY-ferrocene conjugates 1–4 in which one or more ferrocene groups were connected directly to BODIPY core or meso-furyl group were synthesized by coupling of appropriate bromo meso-furyl BODIPYs with α-ethynylferrocene under mild Pd(0) coupling conditions. The compounds were characterized by HR-MS mass, NMR, absorption, electrochemistry and fluorescence techniques. The absorption studies of compounds 1–4 showed charge transfer band in addition to BODIPY absorption bands indicating that the BODIPY and ferrocene moieties interact within the conjugates. On the other hand, the charge transfer band is absent in meso-phenyl BODIPY-ferrocene conjugate due to the orthogonal arrangement of ferrocene appended meso-phenyl group with BODIPY core which prevents the interaction between the two moieties. The electrochemical studies showed strong oxidation due to ferrocene moiety and reduction due to meso-furyl BODIPY unit. The compounds 3 and 4 which contain two and three ferrocenyl groups respectively were oxidized at the same potential with two and three electrons involved in the redox process. The compounds 1–4 are weakly fluorescent due to electron transfer from ferrocene unit to BODIPY unit. However, the fluorescence can be restored by oxidizing the ferrocene to ferrocenium ion which prevents the electron transfer between the two moieties. The computational studies support the experimental results.     

Peptide peak intensities enhanced by cysteine modifiers and MALDI TOF MS

Two cysteine‐specific modifiers we reported previously, N‐ethyl maleimide (NEM) and iodoacetanilide (IAA), have been applied to the labeling of cysteine residues of peptides for the purpose of examining the enhancement of ionization efficiencies in combination with matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI TOF MS). The peak intensities of the peptides as a result of modification with these modifiers were compared with the peak intensities of peptides modified with a commercially available cysteine‐specific modifier, iodoacetamide (IA). Our experiments show significant enhancement in the peak intensities of three cysteine‐containing synthetic peptides modified with IAA compared to those modified with IA. The results showed a 4.5–6‐fold increase as a result of modification with IAA compared to modification with IA. Furthermore, it was found that IAA modification also significantly enhanced the peak intensities of many peptides of a commercially available proteins, bovine serum albumin (BSA), compared to those modified with IA. This significant enhancement helped identify a greater number of peptides of these proteins, leading to a higher sequence coverage with greater confidence scores in identification of proteins with the use of IAA. Copyright © 2012 John Wiley & Sons, Ltd.     

Production and Purification of Pectinase from Bacillus subtilis 15A-B92 and Its Biotechnological Applications

Enzymes that degrade pectin are called pectinases. Pectinases of microbial origin are used in juice clarification as the process is cost-effective. This study screened a pectinase-producing bacterium isolated from soil and identified as Bacillus subtilis 15A B-92 based on the 16S rRNA molecular technique. The purified pectinase from the isolate showed 99.6 U/mg specific activity and 11.6-fold purity. The molecular weight of the purified bacterial pectinase was 14.41 ± 1 kD. Optimum pectinase activity was found at pH 4.5 and 50 °C, and the enzyme was 100% stable for 3.5 h in these conditions. No enzymatic inhibition or activation effect was seen with Fe²⁺, Ca²⁺, or Mg²⁺. However, a slight inhibition was seen with Cu²⁺, Mn²⁺, and Zn²⁺. Tween 20 and 80 slightly inhibited the pectinase, whereas iodoacetic acid (IAA), ethylenediaminetetraacetate (EDTA), urea, and sodium dodecyl sulfate (SDS) showed potent inhibition. The bacterial pectinase degraded citrus pectin (100%); however, it was inactive in the presence of galactose. With citrus pectin as the substrate, the Km and Vmax were calculated as 1.72 mg/mL and 1609 U/g, respectively. The high affinity of pectinase for its substrate makes the process cost-effective when utilized in food industries. The obtained pectinase was able to clarify orange and apple juices, justifying its application in the food industry.     

Farnesol Protects against Cardiotoxicity Caused by Doxorubicin-Induced Stress,Inflammation, and Cell Death: An In Vivo Study in Wistar Rats

Doxorubicin (DOXO) is an antineoplastic drug that is used extensively in managing multiple cancer types. However, DOXO-induced cardiotoxicity is a limiting factor for its widespread use and considerably affects patients’ quality of life. Farnesol (FSN) is a sesquiterpene with antioxidant, anti-inflammatory, and anti-tumor properties. Thus, the current study explored the cardioprotective effect of FSN against DOXO-induced cardiotoxicity. In this study, male Wistar rats were randomly divided into five groups (n = 7) and treated for 14 days. Group I (Control): normal saline, p.o. daily for 14 days; Group II (TOXIC): DOXO 2.4 mg/kg, i.p, thrice weekly for 14 days; Group III: FSN 100 mg/kg, p.o. daily for 14 days + DOXO similar to Group II; Group IV: FSN 200 mg/kg, p.o. daily for 14 days + DOXO similar to Group II; Group V (Standard): nifedipine 10 mg/kg, p.o. daily for 14 days + DOXO similar to Group II. At the end of the study, animals were weighed, blood was collected, and heart-weight was measured. The cardiac tissue was used to estimate biochemical markers and for histopathological studies. The observed results revealed that the FSN-treated group rats showed decrease in heart weight and heart weight/body weight ratio, reversed the oxidative stress, cardiac-specific injury markers, proinflammatory and proapoptotic markers and histopathological aberrations towards normal, and showed cardioprotection. In summary, the FSN reduces cardiac injuries caused by DOXO via its antioxidant, anti-inflammatory, and anti-apoptotic potential. However, more detailed mechanism-based studies are needed to bring this drug into clinical use.     

Synthesis of 2-Aminopyrimidine Derivatives and Their Evaluation as β-Glucuronidase Inhibitors: In Vitro and In Silico Studies

Currently the discovery and development of potent β-glucuronidase inhibitors is an active area of research due to the observation that increased activity of this enzyme is associated with many pathological conditions, such as colon cancer, renal diseases, and infections of the urinary tract. In this study, twenty-seven 2-aminopyrimidine derivatives 1–27 were synthesized by fusion of 2-amino-4,6-dichloropyrimidine with a variety of amines in the presence of triethylamine without using any solvent and catalyst, in good to excellent yields. All synthesized compounds were characterized by EI-MS, HREI-MS and NMR spectroscopy. Compounds 1–27 were then evaluated for their β-glucuronidase inhibitory activity, and among them, compound 24 (IC₅₀ = 2.8 ± 0.10 µM) showed an activity much superior to standard D-saccharic acid 1,4-lactone (IC₅₀ = 45.75 ± 2.16 µM). To predict the binding mode of the substrate and β-glucuronidase, in silico study was performed. Conclusively, this study has identified a potent β-glucuronidase inhibitor that deserves to be further studied for the development of pharmaceutical products.     

Comparative study of 110mAg(I) removal from aqueous media by humic substances

Journal of Radioanalytical and Nuclear Chemistry - In this study, humic substances—dry cowdung powder and humic acid were used for the removal of precious metal ion Ag(I) from aqueous...     

pH‐Independent Recognition of the dG ⋅ dC Base Pair in Triplex DNA: 9‐Deazaguanine N7‐(2′‐Deoxyribonucleoside) and Halogenated Derivatives Replacing Protonated dC

Triplex-forming oligonucleotides (TFOs) containing 9-deazaguanine N⁷-(2′-deoxyribonucleoside) 1a and halogenated derivatives 1b,c were synthesized employing solid-phase oligonucleotide synthesis. For that purpose, the phosphoramidite building blocks 5a – c and 8a – c were synthesized. Multiple incorporations of 1a – c in place of dC were performed within TFOs, which involved the sequence of five consecutive 1a – c ⋅ dG ⋅ dC triplets as well as of three alternating 1a – c ⋅ dG ⋅ dC and dT ⋅ dA ⋅ dT triplets. These TFOs were designed to bind in a parallel orientation to the target duplex. Triplex forming properties of these oligonucleotides containing 1a – c in the presence of Na⁺ and Mg²⁺ were studied by UV/melting-curve analysis and confirmed by circular-dichroism (CD) spectroscopy. The oligonucleotides containing 1a in the place of dC formed stable triplexes at physiological pH in the case of sequence of five consecutive 1a ⋅ dG ⋅ dC triplets as well as three alternating 1a – c ⋅ dG ⋅ dC and dT ⋅ dA ⋅ dT triplets. The replacement of 1a by 9-halogenated derivatives 1b,c further enhanced the stability of DNA triplexes. Nucleosides 1a – c also stabilized duplex DNA.