Mode of action of N,N′-diphenylurea: The isolation and identification of the cytokinins in the transfer RNA from tobacco callus grown in the presence of N,N′-diphenylurea

Summary The tRNA from cytokinin-dependent tobacco callus (Nicotiana tabacum) grown on mineral medium containing N,N-diphenylurea as the source of cytokinin was found to contain 3 cytokinin-active ribonucleosides. The 2 ribonucleosides present in the largest amounts were identified conclusively by their chromatographic properties, ultra-violet and low-resolution mass spectra as the naturally-occurring cytokinins 6-(4-hydroxy-3-methyl-cis-2-butenylamino)-9--D-ribofuranosylpurine and 6-(3-methyl-2-butenylamino)-9--ribofuranosylpurine. A third ribonucleoside, present in smaller amounts, was identified as another naturally-occurring cytokinin 6-(4-hydroxy-3-methyl-2-butenylamino)-2-methylthio-9--D-ribofuranosylpurine on the basis of its chromatographic behaviour. No evidence was found to associate the mode of action of the non-purine cytokinin, N,N-diphenylurea, with tRNA.Abbreviation DPU N,N-diphenylurea     

The Structure of “N1, N6-Carbonyladenosine”

Abstract

Re-interpretation of the available data led to structural assignment of the title N¹, N⁶carbonyladenosine (1b) as N⁶,N⁶-carbonyldiadenosine (4b).     

Synthesis of hydroxydiamines and triamines via reductive cleavage of N–N bond in substituted pyrazolidines

Aliphatic polyamines, being a versatile class of organic compounds, are widely used in many fields of medicine and organic chemistry. However, the general approach to the synthesis of chiral aliphatic polyamines has been still undeveloped. Here, we describe a new method for the synthesis of chiral trifunctional amino compounds, namely hydroxydiamines and triamines. The initial compounds, namely substituted hydroxy- or aminopyrazolidines and pyrazolines, are readily available using convenient stereoselective methods developed earlier by us. The proposed method allows synthesizing of chiral diaminoalcohols and triamines, which are the analogs of a well-known anti-TB drug, namely ethambutol, and cannot be obtained alternatively. The key step of the synthesis is N-N bond cleavage in substituted hydroxy- or aminopyrazolidines and pyrazolines with borane-tetrahydrofuran complex; other known methods for N-N bond cleavage turned out to be ineffective. The main advantage of the proposed method is the retention of a certain configuration of stereocenters in the course of the reaction. Six new chiral diasteomerically pure substituted hydroxydiamines and triamines and the enantiomerically pure triamine with four chiral centers were synthesized and characterized using NMR, IR and mass spectroscopy, as well as elemental analysis.     

Chemistry of the N′-Oxides of Nicotine and Myosmine

Nicotine-N′-oxide (II) was purified to give a crystalline form which has m.p. 170~171°C, and . The reaction of nicotine-N′-oxide with acetic anhydride afforded a good yield of 1′-(3-pyridyl)-4′-(N′-acetylmethylamino)-l′-propanone (V) which was hydrolyzed to give pseudoöxynicotine (III). Nicotine-N′-oxide (II) either with acetyl chloride or with benzoyl chloride, under similar conditions, furnished pseudoöxynicotine (III) without giving the corresponding acyl compound as an intermediate. 2′-Methyl-6′-(3-pyridyl)-tetrahydro-l′,2′-oxazine (XII) rearranged from nicotine-N′-oxide reacted neither with acetic anhydride nor acetyl chloride. Reduction of the oxime (IV) of pseudoöxynicotine dihydrochloride gave dl-l′-amino-l′-(3-pyridyl)-4′-methyl-aminobutane (VII) as a main product. The hydrazone (VIII) of pseudoöxynicotine dihydrochloride subjected to a modification of the Wolf-Kischner reaction, was reduced to yield dihydrometanicotine (IX). The pyrolysis of N′-methylmyosmine (IV) gave N′-methylnicotinamide (XI) and nicotyrine (X) in low yields. The presence of N′-methylmyosmine in the autoxidation mixture of nicotine was also established. Oxidation of nornicotine (XIV) with hydrogen peroxide furnished myosmine-N′-oxide (XV) whose identity was established by its chemical and physical properties. This oxide, on pyrolysis, gave nornicotyrine (XVII) and myosmine (XVI).     

Cytokinin-like activity of N′-substituted N-phenylureas

We have synthesized 14 N-phenylurea derivatives, differing in theheterocyclic portion linked in N-position, and tested theircytokinin-like activity. Three different bioassays were used: the chlorophylllevel determination test, the bioassay for the expression of hormone-inducedchimeric Pg5-GUS gene and the tomato regeneration test, in which1,2-benzisoxazole-3-acetic acid (BOAA) was utilized as auxin. Thecytokinin-likeactivity showed by three of these compounds in the regeneration assay seems tobe related to their different heterocyclic nature. Results obtained indicatethat the N-phenyl-N-1,3,4-thiadiazol-2-ylurea (compound 4), an isomer ofN-phenyl-N-1,2,3-thiadiazol-5-ylurea (thidiazuron, TDZ), in the absenceof auxin induces shoot regeneration in the 34,2% of the explantscultured; theN-phenyl-N-(3-chloro-1,2-benzisothiazol-7-yl) urea (compound 10),structurally different from TDZ, in the absence of auxin induces shootregeneration in the 25,9% of explants, significantly lower than that ofTDZ (68,8%). N-phenyl-N-benzothiazol-6-ylurea (compound 13),structurally different from TDZ, in the absence of auxin induces the99,5% of shoot regeneration, significantly different from that of theother substances. The addition of auxin in the cotyledon regeneration assayreduces the differences. The compound 13 could be considered a new phenylureaderivative with a highly specific cytokinin-like activity.     

Novel Types of N6,2′-Cyclonucleosides

Abstract

Upon oxidation followed by treatment with hydroxylamine, the 3′,5′-diblocked uridine 1 gave the expected oxime 2 together with the N⁶,2′.cyclonucleoside 3 formed by nucleophilic attack of hydroxylamine at both C-6 and C-2′ positions. Reduction of 2 took place predominantly from the α face and the major D-arabino compound obtained gave the cyclonucleosides, 7 via Michael type addition. The structures of the novel cyclonucleosides, particularly their configuration at C-6 were established by X-ray diffraction.     

Direct modulatory effect of hexasodium N,N,N′,N′-ethylenediamine-tetramethylenephosphonate on bone cell function in vitro

The phosphonate hexasodium N,N,N′,N′-ethylenediamine-tetramethylenephosphonate (EDITEMP · Na₆) reduced alkaline phosphatase (Alp) activity and cAMP response to parathyroid hormone (PTH) in primary cultures of foetal rat calvaria cells in a dose-dependent manner, while not affecting culture DNA content. EDITEMP · Na₆ also inhibited the mineralization of three-dimensional bone nodules formed in vitro, but not the number of nodules formed. Bone cell culture DNA content was also reduced by EDITEMP · Na₆ but at concentrations in excess of those needed to modulate osteoblastic cell function. Withdrawal of EDITEMP · Na₆ led to slow but complete recovery of Alp activity. At EDITEMP · Na₆ concentrations of 25 μM and higher, recovery of Alp activity appeared to be independent of protein and/or DNA synthesis. Cell culture acid phosphatase (Acp) activity was not affected by EDITEMP · Na₆. The results indicate that EDITEMP · Na₆ has a direct inhibitory effect on (mature) osteoblastic cell function. In the presence of bone tissue this inhibition also occurred, although not at a relatively low dose level.     

N,N,N′,N′-tetramethyl-p-phenylenediamine initiates the appearance of a well-resolved I peak in the kinetics of chlorophyll fluorescence rise in isolated thylakoids

Addition of N,N,N′,N′-tetramethyl-p-phenylendiamine (TMPD) to thylakoid membranes isolated from pea leaves initiates the appearance of peak I in the polyphasic rise of chlorophyll (Chl) fluorescence observed during strong illumination, making it similar to that observed in leaves or intact chloroplasts. This effect depends on TMPD concentration and incubation period of isolated thylakoids with TMPD. The resolution of I-peak in the presence of weak concentrations of TMPD which reduced the overlap between I- and P-peaks, resulted from a decreased reduction of both fast and slow plastoquinone (PQ) pools of the granal and stromal thylakoids, respectively, as TMPD effectively accepts electrons from reduced PQ. High concentrations of TMPD markedly decreased the J–I–P phase of fluorescence rise and greatly retarded the I–P step rise. Accumulation of oxidized TMPD in the thylakoid lumen accelerated the re-oxidation of the acceptor side of Photosystem II (PSII) as illustrated by a two-fold increase in the magnitude of the fast component and complete suppression of the middle component of the variable Chl fluorescence (F_v) decay in the dark. Evidently, exogenous addition of high concentrations of TMPD prevented the light-induced reduction of the slow PQ pool.     

Antimicrobial efficacy of some N,N’-Dialkyl-N,N’-dimethyl-1, 6-hexanediamine dioxides

A total of 17 N,N'-dialkyl-N,N'-dimethyl-1,6-hexanediamine dioxides were tested for activity against three microorganisms. A relationship was found between the length of the alkyl substituent and antimicrobial activity.     

Exploration of secondary and tertiary pharmacophores in unsymmetrical N,N′-diaryl urea inhibitors of soluble epoxide hydrolase

The impact of various secondary and tertiary pharmacophores on in vitro potency of soluble epoxide hydrolase (sEH) inhibitors based on the unsymmetrical urea scaffold 1 is discussed. N,N′-Diaryl urea inhibitors of soluble epoxide hydrolase exhibit subtle variations in inhibitory potency depending on the secondary pharmacophore but tolerate considerable structural variation in the second linker/tertiary pharmacophore fragment.     

Gene Regulation in N Mutants of Bacteriophage λ

Mutants (N(-)nin) of bacteriophage lambda in which the N gene product is not required for growth on wild-type Escherichia coli do not plate on recA bacterial mutants. Secondary mutants, selected for growth on recA, lie within the immunity region to the right of gene cI and appear identical to the cro mutants of Eisen et al. In an N(+) phage, a cro mutation causes enhanced and prolonged production of lambda exonuclease. N(-)cro phages make no detectable exonuclease, but show an increased rate of specific excision from lysogens and are excluded by P2 prophage. These properties, together with the ability to plate on recA, suggest that N(-)cro phages express genes to the left of N at a rate that is very low but higher than that for N(-)cro(+) phages. N(-)nin phages can integrate at the normal site on the bacterial chromosome, but specific excision from lysogens is immeasurably low.     

Measurement of the apparent diffusion coefficient of N‐butane in soil

Measurements of in‐soil diffusion coefficients and the application of an appropriate diffusional model can allow for a more accurate prediction of soil gas concentrations and movement to locate subterranean contamination of volatile materials. The present study was undertaken to measure and evaluate the “apparent in‐soil diffusion coefficient”; for n‐butane through soil columns under non‐steady‐state conditions. The term “apparent in‐soil diffusion coefficient”; refers to a numerical coefficient that primarily describes the movement of the material by diffusion but also contains effects due to other mechanisms (e.g., adsorption and solubility).

Six test columns were evaluated at three soil porosity levels ranging from 0.30 to 0.43 and at two column temperature conditions, nominally 18°C and 7°C. Soil columns measured 25.4 cm in diameter by 84 cm in height and contained a moist sand/silt/clay mixture. The numerical range for the apparent in‐soil diffusion coefficients for n‐butane was 0.447 × 10^‐3cm²/s to 0.561 × 10^‐3cm²/s. The lower coefficient values were associated with lower soil porosity levels and cooler column conditions.     

Interactions of Bovine Brain Tubulin with Pyridostigmine Bromide and N,N′-Diethyl-m-Toluamide

Pyridostigmine bromide (PB), an inhibitor of acetylcholinesterase, has been used as a prophylactic for nerve gas poisoning. N,N-diethyl-m-toluamide (DEET) is the active ingredient in most insect repellents and is thought to interact synergistically with PB. Since PB can inhibit the binding of organophosphates to tubulin and since organophosphates inhibit microtubule assembly, we decided to examine the effects of PB and DEET on microtubule assembly as well as their interactions with tubulin, the subunit protein of microtubules. We found that PB binds to tubulin with an apparent K _d of about 60 M. PB also inhibits microtubule assembly in vitro, although at higher concentrations PB induces formation of tubulin aggregates of high absorbance. Like PB, DEET is a weak inhibitor of microtubule assembly and also induces formation of tubulin aggregates. Many tubulin ligands stabilize the conformation of tubulin as measured by exposure of sulfhydryl groups and hydrophobic areas and stabilization of colchicine binding. PB appears to have very little effect on tubulin conformation, and DEET appears to have no effect. Neither compound interferes with colchicine binding to tubulin. Our results raise the possibility that PB and DEET may exert some of their effects in vivo by interfering with microtubule assembly or function, although high intracellular levels of these compounds would be required.     

The role of N efflux and root abscission in determining plant δ 15 N

Plant and Soil - We investigated the relationship between plant δ15N and rates of nitrate supply in wheat (Triticum aestivum; L. cv. SST015) and how this relates to N efflux and root...     

N,N′-Dinitrosopiperazine-Mediated AGR2 Is Involved in Metastasis of Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) has a high metastatic character in the clinic, but its mechanism is not clear. As a carcinogen with organ specificity for the nasopharyngeal epithelium, N,N′-Dinitrosopiperazine (DNP) is involved in NPC metastasis. Herein, our data revealed that anterior gradient 2 (AGR2) was overexpressed in human NPC tissues, particularly in cervical lymph node metastatic NPC (LMNPC). High AGR2 expression was associated with NPC metastasis. Importantly, DNP induced AGR2 expression, and increased cell motility and invasion in the NPC cell line 6–10B. However, DNP-mediated cell motility and invasion was dramatically decreased when transfected with siRNA-AGR2. Further, AGR2 directly regulated cathepsin (CTS) B and D by binding them in vitro. These results indicate that DNP induces AGR2 expression, regulates CTSB and CTSD, increases cell motility and invasion, and promotes NPC tumor metastasis. Therefore, DNP-mediated AGR2 expression may be an important factor in prolific NPC metastasis.     

Production of N,N′-diacetylchitobiose from chitin using temperature-sensitive chitinolytic enzyme preparations of Aeromonas sp. GJ-18

Summary N,N′-diacetylchitobiose was produced from chitin as a major hydrolytic product by controlling the ratio of β-N-acetylglucosaminidase to N,N′-diacetylchitobiohydrolase activities in the crude enzyme preparation of Aeromonas sp. GJ-18. When the enzyme preparation was preincubated at 50 °C, β-N-acetylglucosaminidase was nearly inactivated, while the N,N′-diacetylchitobiohydrolase was still active. Thus, the composition of chitin oligosaccharides depended on the preincubation temperature of the crude enzyme preparations. Typically, after 7 days of incubation with the substrate chitin, 78.9 and 56.6% of N,N′-diacetylchitobiose yields were obtained from swollen α-chitin and powdered β-chitin, respectively, with enzyme preparations that had been pretreated at 50 °C for 60 min.