Synthesis of polypyrrole within the cell wall of yeast by redox-cycling of [Fe(CN)6]3−/[Fe(CN)6]4−

Yeast cells are often used as a model system in various experiments. Moreover, due to their high metabolic activity, yeast cells have a potential to be applied as elements in the design of biofuel cells and biosensors. However a wider application of yeast cells in electrochemical systems is limited due to high electric resistance of their cell wall. In order to reduce this problem we have polymerized conducting polymer polypyrrole (Ppy) directly in the cell wall and/or within periplasmic membrane. In this research the formation of Ppy was induced by [Fe(CN)₆]³⁻ions, which were generated from K₄[Fe(CN)₆], which was initially added to polymerization solution. The redox process was catalyzed by oxido-reductases, which are present in the plasma membrane of yeast cells. The formation of Ppy was confirmed by spectrophotometry and atomic force microscopy. It was confirmed that the conducting polymer polypyrrole was formed within periplasmic space and/or within the cell wall of yeast cells, which were incubated in solution containing pyrrole, glucose and [Fe(CN)₆]⁴⁻. After 24 h drying at room temperature we have observed that Ppy-modified yeast cell walls retained their initial spherical form. In contrast to Ppy-modified cells, the walls of unmodified yeast have wrinkled after 24 h drying. The viability of yeast cells in the presence of different pyrrole concentrations has been evaluated.     

Conformational Studies of Dextran [α-(1⇒6)-D-Glucan]

Abstract

A theoretical conformational study of dextran, a (l?6)-linked α-D-glucan polysaccharide, has been made to allow an explicit comparison with earlier results on pustulan, the corresponding (1 ?6)-linked β-D-glucan. The nonbonded, torsional and hydrogen bond contributions to potential energy were calculated as a function of rotational angles φ, ψ, and ω The (φ, ψ, ω)-space of the disaccharide and of helices contain many local energy minima with very small energy differences. A comparison of (1?6)-α-D-glucans with (1?6)-β-D-glucans indicates significant differences in conformational behavior. Specifically, our results shed light on the fact that dextran does not gel, whereas pustulan does. The difference in tendency to gel may be related to the fact that dextran has no particularly favored conformations with structural regularity whereas pustulan does.     

Characterization of hemoglobin Burke [β107 (G9) Gly→Arg]

Hb Burke [107 (G9) GlyArg] was discovered in a young woman with hemolytic anemia. A substitution in this position has not been previously reported either in the human -chain or in any of the animal -chains so far sequenced. The abnormal hemoglobin shows heat instability and a lowered oxygen affinity. The substitution of a large charged arginine residue for the small glycine residue in the G helix next to a heme contact (Leu-106) may be responsible for these effects. Hb Burke is compared with five other hemoglobins having Gly-Arg substitutions in other parts of the molecule.This work was supported in part by U.S. Public Health Service Grants AM-17850 and AM-18006.     

The conversion of 4-hydroxypyrazolo-[3,4-d]pyrimidine (allopurinol) into 4,6-dihydroxypyrazolo[3,4-d]pyrimidine (oxipurinol) in vivo in the absence of xanthine–oxygen oxidoreductase

1. A patient with congenital deficiency of xanthine oxidase (EC 1.2.3.2) (xanthinuria) excreted the xanthine isomer 4,6-dihydroxypyrazolo[3,4-d]pyrimidine (oxipurinol) in his urine when the hypoxanthine isomer 4-hydroxypyrazolo[3,4-d]pyrimidine (allopurinol) was given by mouth. 2. The identity of the oxipurinol that the patient excreted was established by mass spectrometry. 3. The mass spectra and infrared spectra of allopurinol, oxipurinol, hypoxanthine and xanthine are compared. 4. A mechanism for the fragmentation of these compounds that occurs during their mass-spectrometric investigation is proposed. 5. A possible metabolic pathway for the oxidation of allopurinol to oxipurinol in the absence of xanthine oxidase is discussed.     

Computational investigation of the geometric structures of [(CN)5PtTl(CN)n]n− (n=0, 1, 2 or 3)

[(CN)₅PtTl(CN)_n]ⁿ⁻ (n=0–3, complexes I–IV) have been studied computationally using quasi-relativistic gradient-corrected density functional theory. Good agreement is obtained with previous EXAFS and Raman data for complexes II–IV, but calculations significantly overestimate the PtTl bond length and underestimate ν(PtTl) for complex I. The addition of co-ordinating water molecules to the thallium atom in complexes I–III has little effect on complexes II and III, but significantly shortens the PtTl bond in complex I, bringing it into excellent agreement with experiment. The bond length shortening is traced to intramolecular hydrogen bonding. The total molecular bonding energies of hydrated I and I′ (in which the axial ligands on the thallium and platinum atoms are interchanged) are found to be very similar to one another, suggesting that complex I might exist as a mixture of isomers in solution.     

Synthesis of (S)-(—)-Vertinolide

(S)-(?)-Vertinolide 1 was synthesized via the tetronic acid derivative 6 from (S)-(?)-tetrahydro-2-methyl-5-oxo-2-furancarboxylic acid 3. (±)-Vertinolide was also synthesized from (±)-3.     

Syntheses of (±)-Epoformin (Desoxyepoxydon) and (±)-Epiepoformin (Desoxyepiepoxydon)

Boron is an essential nutrient for plants, but it is toxic in excess. Transgenic rice plants expressing an Arabidopsis thaliana borate efflux transporter gene, AtBOR4, at a low level exhibited increased tolerance to excess boron. Those lines with high levels of expression exhibited reduced growth. These findings suggest a potential of the borate transporter BOR4 for the generation of high-boron tolerant rice.     

Synthesis of (±)-licarin-B

The synthesis of (±)-licarin-B, a neolignan of Licaria aritu Ducke (Lauraceae), was achieved by pyrolysis of 3-hydroxy-3-piperonyl-1-propyl-2-methoxy-4-(E)-propenylphenyl ethers.     

Synthesis of (–)-Muricatacin

The synthesis of (–)-muricatacin starting from 1-bromododecane and 2-pentyn-l-ol is described. 2-Pentadecyn-1-ol (4), which was prepared from 1-bromododecane (2) and 2-pentyn-1-ol (3), was converted to epoxy alcohol 6 through a two-step reaction sequence, 6 being successively submitted to tosylation, iodination, chain extension with tert-butyl lithioacetate, and acid-catalyzed cyclization to give (–)-muricatacin (1a). Recrystallization afforded optically pure 1a.     

Structural diversity of neutral bis-(β-iminoaldehyde) complexes of nickel(II)

Series of Ni^II and Cu^II complexes with dianionic [N₂O₂] ligands were synthesized and characterised applying spectroscopic and X-ray diffraction techniques. The ligands were obtained by 1:2 condensation of ethylene- and propylenediamine with malonic aldehyde derivatives (R² = H, R¹ = H or OCH₃). Although the molecular formulae of the complexes are quite similar, the X-ray investigations have proved a significant structural diversity in the solid state. Among others, we found some simple nearly planar molecules stacked in the crystal lattice with electron density of six-membered rings delocalised over the chelate rings as well as some very complex polymeric or nickel acetate bridged trinuclear complexes. The coordination of the nickel ion by surrounding oxygen and nitrogen atoms is square-planar in the simplest case and octahedral in the most complex one. Small topological differences in similar molecules generate completely different crystal structures.From magnetic studies, a small, negative value of J obtained confirms the occurrence of weak antiferromagnetic interactions between the Ni^II ions in polymeric chain of the propylenediamine dialdehyde substituted derivative.     

Synthesis of (±)-Homosarkomycin and (±)-Rosaprostol

(±)-Homosarkomycin (2) and (±)-rosaprostol (3) were synthesized from (±)-methyl 2-oxo-bicyclo[3.1.0]hexane-1-carboxylate (1) by using the nucleophilic ring opening reaction on the double-activated cyclopropane ring as the key step.     

Synthesis of (±)-Lamprolobine and (±)-Epilamprolobine

(±)-Lamprolobine, the (+)-enatiomer of which was isolated from the leaves of Lamprolobium fruticosum, and (±)-epilamprolobine were synthesized from δ-valerolactam.     

Synthesis of (±)-Hydroxytremetone

(±)Hydroxytremetone (III) has been synthesized from 2-(α-hydoxyisopropyl)-6-hydroxycoumaran (V b) via its O-acetate V c by dehydration with phosphorus tribromide in pyridine solution, followed by acylation with a mixture of trifluoroacetic anhydride and acetic acid. Isohydroxytremetone (IX b) was also synthesized.     

Dose Responsiveness and Variation Among Inbred Strains of Mice in Production of Interferon After Treatment with Poly (I)· Poly (C) [Poly-d-Lysine] Complexes

Poly-d-lysine forms a stochiometric complex with poly(I) . poly(C) which has a higher T(m) (83 C in 0.15 m NaCl) than the uncomplexed double-stranded polyribo-nucleotide (63 C). The complex was superior to poly(I) . poly(C) alone as an interferon inducer in vivo. Significant serum interferon titers were attained in Swiss mice during a 24-hr period after intraperitoneal injection of 10 to 300 mug of poly(I) . poly(C) [1.0 poly-d-lysine] complex, at concentrations of 100 to 1,000 mug/ml. The serum interferon responses (average and maximum titers) of a series of inbred strains of mice to a single intraperitoneal injection of 100 mug of complex decreased in the order: Swiss > DBA/2 > C3H > BALB/c > CF-1 > AKR, C57Bl/6, NZB > SJL > NZW and varied by a factor of approximately 100 from the most to the least responsive.     

Synthesis of (±)-Xanthoxins

The enzymatic properties of P2-2 enzyme were determined by using cells of M. radiodurans. The enzyme was: most active at 60°C incubation temperature, stable at 40°C in neutral buffer, and inactivated by heating at 80°C for 15min. Maximal lytic activity occurred at pH 8.5 in Tris-HCl buffer. The range of enzyme stability was between pH 5.5 and 8. Bivalent metal ions, p-chloromercuribenzoate and monoiodo acetate inhibited lytic activity. The molecular weight was estimated to be 16,000 daltons by gel filtration on Sephadex G-75. The enzymatic digestion of peptidoglycans from the cell walls of M. radiodurans and M. lysodeikticus liberated free amino groups, but neither reducing groups nor N-acetylhexosamine, indicating that the enzyme was an endopeptidase. From analysis of the N-terminal amino acids of the digests, it is suggested that the P2-2 enzyme cleaves the peptide bond at the carboxyl group of D-alanine in peptidoglycan.     

The reaction of papain with Ellman''s reagent [5,5′-dithiobis-(2-nitrobenzoate) dianion]

1. The report by Robyt et al. (1971) that the 2-nitro-5-mercaptobenzoate dianion (Nbs(2-)) produced by reaction of papain with the 5,5'-dithiobis-(2-nitrobenzoate) dianion (Nbs(2) (2-); Ellman's reagent) cleaves the three disulphide bonds in papain is shown to be incorrect. 2. When partially active papain containing approx. 0.4 mol of thiol/mol of protein is incubated with excess of Nbs(2) (2-) at pH8, Nbs(2) (2-) reacts with the protein in an amount stoicheiometric with the cysteinyl thiol group of papain to produce Nbs(2-) in an amount stoicheiometric with the original papain cysteinyl thiol group, and the catalytically inactive mixed disulphide, papain-Nbs(-). 3. Papain catalyses the hydrolysis of Nbs(2) (2-) at pH10.5 probably by nucleophilic catalysis involving the enzyme's thiol group. 4. These results cast very serious doubts on the claim by Robyt et al. (1971) to have established a new general method for the determination of cystinyl disulphide residues in proteins.     

The crystal and molecular structures of dichlorobis (5,7-diphenyl-1,2,4-triazolo[1,5-α]pyrimidine)zinc(II) (1) and dichlorobis(5,7-diphenyl-1,2,4-triazolo[1,5-α]pyrimidine)cobalt(II) (2)

The synthesis and structural studies of the new ligand 5,7-diphenyl-1,2,4-triazolo[1,5-α]pyrimidine (dptp), which can be considered as an analog of purine, and its complexes are described. Complexes were characterised by spectral measurements (IR, NMR, UV-Vis). In addition X-ray structural analysis was performed. Crystals of [Zn(C₁₇H₁₂N₄)₂Cl₂] (1) revealed the following parameters: M_r = 680.9; monoclinic for 2188 observed reflections. [Co(C₁₇H₁₂N₄)₂Cl₂] (2); M_r = 674.4; monoclinic for 1630 observed reflections.     

Discovery of novel 5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyridine derivatives as γ-secretase modulators (Part 2)

γ-Secretase modulators (GSMs), which lower pathogenic amyloid beta (Aβ) without affecting the production of total Aβ or Notch signal, have emerged as a potential therapeutic agent for Alzheimer’s disease (AD). A novel series of 5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyridine derivatives was discovered and characterized as GSMs. Optimization of substituents at the 8-position of the core scaffold using ligand-lipophilicity efficiency (LLE) as a drug-likeness guideline led to identification of various types of high-LLE GSMs. Phenoxy compound (R)-17 exhibited especially high LLE as well as potent in vivo Aβ₄₂-lowering effect by single administration. Furthermore, multiple oral administration of (R)-17 significantly reduced soluble and insoluble brain Aβ₄₂, and ameliorated cognitive deficit in novel object recognition test (NORT) using Tg2576 mice as an AD model.     

Biological function of modified nucleotides T_(54) and ψ_(55) of yeast tRNA~(Ala)

The 3' half molecule of yeast tRNAAla (nucleotides 36-75) was hybridized with a DNA fragment (5'GGAATCGAACC 3') and the hybrid was then digested with E. coli RNase H (from Boehringer). The enzyme can specifically cleave the 3' half molecule at the 3' side of nucleotide ψ55, thus a fragment C36-ψ55 was prepared. The 3'-terminal T or Tψ of this fragment was removed by one or two cycles of periodate oxidation and $-elimination. The products were fragments C36-T54 and C36-G53. Three yeast tRNAAla fragments C56-A76, U55-A76 (with ψ55 replaced by U), U54-A76 (with T54ψ55 replaced by UU) were synthesized and ligated with three prepared fragments (C36-ψ55 C36-T54 and C36-G53) respectively by T4 RNA ligase. The products were further ligated with the 5' half molecule (nu-cleotides 1-35). Using this method, one reconstituted yeast tRNAAla (tRNAr) and two yeast tRNAAla analogs: (i) tRNAa with U55 instead of ψ55; (ii) tRNAb with U54U55 instead of T54ψ55 were synthesized. The charging and incorporation activi     

Thieno[2,3-b]pyridines—A new class of multidrug resistance (MDR) modulators

To identify new potent multidrug resistance modulators, we have synthesized a series of novel thieno[2,3-b]pyridines and furo[2,3-b]pyridines, and examined their stucture–activity relationships. All synthesized compounds were tested to determine BCRP1, P-gp, and MRP1 inhibitor activity, and most potent MDR modulators were also screened for their toxicity, cytotoxicity and Ca²⁺ channel antagonist activity. Among these compounds, thieno[2,3-b]pyridine (6r) was found to exhibit a potent P-gp inhibitory action with EC₅₀ = 0.3 ± 0.2 μM, MRP1 inhibitory action with EC₅₀ = 1.1 ± 0.1 μM and BCRP1 inhibitory action with EC₅₀ = 0.2 ± 0.05 μM and may represent suitable candidate for further pharmacological studies.