New thiazinediones and other components from Xanthium strumarium

Two new thiazinediones along with five known compounds were isolated from the fruits of Xanthium strumarium L. The structures of the two new compounds were determined to be 7-hydroxymethyl-8,8-dimethyl-4,8-dihydrobenzol[1,4]thiazine-3,5-dione-11-O-β-D-glucopyranoside (1) and 2-hydroxy-7-hydroxymethyl-8,8-dimethyl-4,8-dihydrobenzol[1,4]thiazine-3,5-dione-11-O-β-D-glucopyranoside (2). The five known compounds were identified as xanthiazone (3), chlorogenic acid (4), ferulic acid (5), formononetin (6), and ononin (7), respectively. Published in Khimiya Prirodnykh Soedinenii, No. 5, pp. 456–458, September–October, 2006.     

The involvement of LHCII-associated polyamines in the response of the photosynthetic apparatus to low temperature

The influence of low temperature on the structure and function of the photosynthetic apparatus was investigated in Phaseolus vulgaris L. Ten-day-old plants (grown at 26 degrees C) have been exposed to low temperature (6 degrees C) for 52 h and, then, transferred to the initial temperature (26 degrees C) for additional 30 h. Biochemical and physico-chemical measurements performed in the low temperature-treated plants showed that the response of the photosynthetic apparatus to low temperature is affected by the changes occurring in the pattern of LHCII-associated putrescine (Put) and spermine (Spm) which adjust the size of LHCII. The decrease of Put/Spm ratio, mainly due to the reduction in the quantity of LHCII-associated Put led to an increase of the LHCII, especially of the oligomeric forms. These alterations in the structure of the photosynthetic apparatus combined with the reduction in the photosynthetic electron transfer rate resulted in the inactivation of active reaction centers and the increase of dissipated energy which diminished the photosynthetic efficiency and the maximal photosynthetic rate. The transfer of plants at 26 degrees C after the low temperature treatment showed that, structurally and functionally, the photosynthetic mechanism recovered quite fast to the initial condition.     

Affinity and nuclease activity of macrocyclic polyamines and their CuII complexes

The stability constants of Cu(II) complexes that consist of either an oxaaza macrocycle with two triamine moieties linked by dioxa chains, or two macrocyclic ligands with a polyamine chain which are connecting the 2 and 9 positions of phenanthroline, have been determined by means of potentiometric measurements. The results are compared to those reported for other ligands with a similar molecular architecture. Of the complexes that contain phenanthroline in their macrocycle, the Cu(II) ion of the complex with the smallest and most rigid macrocycle (L3) has an unsaturated coordination sphere, while in the complex with the largest macrocycle (L5) the Cu(II) ion is coordinatively almost saturated. These results are corroborated by the crystal structure of the [CuL5](ClO4)2 complex. The affinity of the ligands and the complexes towards nucleic acids was studied by measuring the changes in the melting temperature, which showed that the affinity of the macrocyclic ligands towards double-stranded DNA or RNA is generally smaller than that of their linear analogues that bear a similar charge, with a strong preference for polyA-polyU, a model for RNA. However, the complexes of two of the changed macrocyclic ligands which contain a phenanthroline unit (L4, L5) showed a distinctly larger increase in their melting temperature deltaTm with DNA (polydA-polydT), which is reversed again in favor of RNA upon metallation to the dinuclear copper complex with L5. Experiments with supercoiled plasmid DNA showed a particularly effective cleavage with a mononuclear Cu(II) complex that contains a phenanthroline unit (L6). Related ligands showed less activity towards DNA, but not so towards the biocidic bis(p-nitrophenyl)phosphate (BNPP). In both cases (with DNA and BNPP) the activity seemed to increase with decrease of coordinative saturation of the Cu(II) ion, with the exception of one particular ligand (L6). Experiments with radical scavengers in the DNA experiments showed some decrease in cleavage, which indicates the participation of redox processes.     

Synthesis of polyamines with pendant cyanoimidazole units and their electrochemical properties

The 2-(1-methyl-4,5-dicyanoimidazolyl) group was attached to poly(diallylamine) and polyethylenimine, affording polymers containing an electron-withdrawing pendant group. The key to their preparation is high reactivity of 1-methyl-2-fluoro-4,5-dicyanoimidazole (1) toward nucleophilic aromatic substitution (NAS) reactions with aliphatic amines. Cyclic voltammograms of these polymers show reduction waves at −2.6 to −2.7 V vs. Ag/Ag⁺ but no reoxidation waves, unlike those of monomeric and oligomeric model compounds, which are quasi-reversible. The cyclic voltammetry studies of oligomeric model compounds with different alkyl spacers show that the degree of quasi-reversibility decreases as dicyanoimidazoles are crowded together in a molecule, suggesting that a certain degree of chemical reaction occurs between reduced dicyanoimidazole groups. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2619–2629, 1998     

The structure of protonated diamines and polyamines

The reduced mobilities in air, at 200C, of six isomeric C₇H₁₈N₂ protonated diamines, two triamines (caldine and spermidine), and two tetramines (thermine and spermine) were measured by ion mobility spectrometric (IMS) techniques. The results indicated that all these polyamines undergo proton-induced cyclization, with the proton forming a bridge between two amino groups. It appears as if the favored configuration of the protonated polyamines involves a six- or seven-membered ring rather than a bridge between the terminal amino groups. It is believed that in the tetramines the cyclic structure is formed between the two central, more basic, secondary amine sites.     

Pyromellitamide aggregates and their response to anion stimuli

The N,N',N',N'-1,2,4,5-tetra(ethylhexanoate) pyromellitamide is found to be capable of both intermolecular aggregation and binding to small anions. It is synthesized by aminolysis of pyromellitic anhydride with ethanolamine, followed by a reaction with hexanoyl chloride. The single-crystal X-ray structure of the pyromellitamide shows that it forms one-dimensional columnar stacks through an intermolecular hydrogen-bonding network. It also forms self-assembled gels in nonpolar solvents, presumably by a hydrogen-bonding network similar to the solid-state structure as shown by IR and XRD studies. Aggregation by intermolecular hydrogen bonding of the pyromellitamide is also observed by NMR and IR in solution. Fitting of NMR dilution data for pyromellitamide in d6-acetone to a cooperative aggregation model gave KE=232 M-1 and positive cooperativity of aggregation (rho=0.22). The pyromellitamide binds to a range of small anions with the binding strength decreasing in the order chloride>acetate>bromide>nitrate approximately iodide. The data indicate that the pyromellitamide binds two anions and that it displays negative cooperativity. The intermolecular aggregation of the pyromellitamide can also be altered using small anion stimuli; anion addition to preformed self-assembled pyromellitamide gels causes their collapse. The kinetics of anion-induced gel collapse are qualitatively correlated to the binding affinities of the same anions in solution. The cooperative anion binding properties and the sensitivity of the self-assembled gels formed by pyromellitamide toward anions could be useful in the development of sensors and switching/releasing devices.     

Fluorescent diazapyrenium films and their response to dopamine

Experimental protocols for the preparation of 2,7-diazapyrenium films on glass, quartz, and silica in one or two steps have been developed. The one-step procedures involve the adsorption of preformed 2,7-diazapyrenium dications with trimethoxysilane appendages to the hydroxylated substrates. The two-step procedures consist in the formation of interfacial polysiloxanes with pendent chloromethyl groups and their subsequent coupling to monoalkylated 2,7-diazapyrene derivatives. For the modification of the glass slides, the silane building blocks have been copolymerized with Si(OEt)4. The transmission absorption spectra of the coated glass and quartz slides all reveal the characteristic bands of the 2,7-diazapyrenium chromophores. Combustion analyses confirm the adsorption of the 2,7-diazapyrenium dications on the silica particles. A comparison of the surface coverages of all films indicates that the one-step procedures are significantly more efficient than their two-step counterparts. Furthermore, the copolymerization of the silane building blocks with Si(OEt)4 translates into an increase in 2,7-diazapyrenium surface coverage of approximately 1 order of magnitude. The emission and excitation spectra of all modified substrates reveal the characteristic bands of the 2,7-diazapyrenium fluorophores. The fluorescence quantum yield, however, decreases as the surface coverage increases. Presumably, interactions between adjacent fluorophores encourage nonradiative deactivation pathways. With the exception of the glass slides modified in two steps, all films respond to the presence of dopamine, in aqueous environments at neutral pH, with pronounced decreases in emission intensity. The association of the 2,7-diazapyrenium acceptors and dopamine donors at the solid/liquid interface is responsible for fluorescence quenching. The glass slides and silica particles modified in one step are the most sensitive substrates and respond to sub-millimolar concentrations of dopamine with large changes in emission intensity. Furthermore, their fluorescence is not affected by relatively large concentrations of ascorbic acid, which is the main interferent in conventional dopamine detection protocols. Thus, these results demonstrate that the supramolecular association of 2,7-diazapyrenium dications and pi-electron rich substrates can be reproduced successfully at solid/liquid interfaces and suggest that the unique properties of 2,7-diazapyrenium films might lead to dopamine-sensing schemes based on fluorescence measurements.     

Urinary polyamines and N-acetylated polyamines in four patients with Alzheimer's disease as their N-ethoxycarbonyl-N-pentafluoropropionyl derivatives by gas chromatography-mass spectrometry in selected ion monitoring mode

Simultaneous determination of putrescine, cadaverine, spermidine, spermine, N¹-acetylputrescine, N¹-acetylcadaverine, N¹-acetylspermidine, N⁸-acetylspermidine and N¹-acetylspermine in aqueous samples was achieved as their N-ethoxycarbonyl-N-pentafluoropropionyl derivatives by gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode. The overall GC-SIM-MS method was linear (r ≥ 0.9987), repetitive (% relative standard deviation = 1.3-6.4), and accurate (% relative error = −2.1-8.6). As compared to normal subjects, the levels of putrescine, N¹-acetylspermine and spermine were significantly elevated while the levels of N¹-acetylputrescine, N¹-acetylcadaverine and N¹-acetylspermidine were markedly reduced in all four Alzheimer's disease (AD) patients. When star symbol plotting was applied to the normalized levels of nine polyamines relative to the corresponding normal mean values, each star pattern of the AD patients was deformed, thus being readily distinguishable from the nonagon shape of the normal group average.     

Polyampholytes from chloromethylated diphenyl oxide-formaldehyde oligomer,polyamines, and pyridinecarboxylic acids and their nitriles

Conclusions The optimum conditions were found for the synthesis of some new polyampholytes from a chloromethylated diphenyl oxide-formaldehyde oligomer, polyamines, and either pyridinecarboxylic acids or their nitriles, and their properties were studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1652–1654, July, 1978.     

The assembly state between magnetic nanosensors and their targets orchestrates their magnetic relaxation response

The target-induced clustering of magnetic nanoparticles is typically used for the identification of clinically relevant targets and events. A decrease in the water proton transverse NMR relaxation time, or T(2), is observed upon clustering, allowing the sensitive and accurate detection of target molecules. We have discovered a new mechanistically unique nanoparticle-target interaction resulting in a T(2) increase and demonstrate herein that this increase, and its associated r(2) relaxivity decrease, are also observed upon the interaction of the nanoparticles with ligands or molecular entities. Small molecules, proteins, and a 15-bp nucleic acid sequence were chemically conjugated to polyacrylic-acid-coated iron oxide nanoparticles, and all decreased the original nanoparticle r(2) value. Further experiments established that the r(2) decrease was inversely proportional to the number of ligands bound to the nanoparticle and the molecular weight of the bound ligand. Additional experiments revealed that the T(2)-increasing mechanism was kinetically faster than the conventional clustering mechanism. Most importantly, under conditions that result in T(2) increases, as little as 5.3 fmol of Bacillus anthracis plasmid DNA (pX01 and pX02), 8 pmol of the cholera toxin B subunit (Ctb), and even a few cancer cells in blood were detected. Transition from the binding to the clustering mechanism was observed in the carbohydrate-, Ctb-, and DNA-sensing systems, simply by increasing the target concentration significantly above the nanoparticle concentration, or using Ctb in its pentameric form as opposed to its monomer. Collectively, these results demonstrate that the molecular architectures resulting from the interaction between magnetic nanosensors and their targets directly govern water proton NMR relaxation. We attribute the observed T(2) increases to the bound target molecules partially obstructing the diffusion of solvent water molecules through the superparamagnetic iron oxide nanoparticles' outer relaxation spheres. Finally, we anticipate that this novel interaction can be incorporated into new clinical and field detection applications, due to its faster kinetics relative to the conventional nanoparticle-clustering assays.     

Improvement of the analysis of dansylated derivatives of polyamines and their conjugates by high-performance liquid chromatography.

The paper described a method for improving the hydrolysis of conjugated polyamines in PH fraction, isolated from the lichen Evernia prunastri, as well as the optimization of dansylation procedure of these polyamines on the basis of the pH value to which derivatization is achieved. Dansylated polyamines have been later separated by high-performance liquid chromatography (HPLC) using a gradient elution. Hydrolysis of conjugates requires acid treatment at room temperature rather than at 110 degrees C, as usually described. Dansylation is improved at high pH values, whereas removal of phenolics (mainly evernic acid), from the conjugates requires low pH values.     

Mechanisms of pulse response and differential response of bacteriorhodopsin and their relations

Bacteriorhodopsin (BR) films are oriented and deposited on indium tin oxide conductive glass by using electrophoretic sedimentation and Langmuir-Blodgett methods to construct sandwich-type photocells, respectively. The pulse response photoelectric signal of the BR photocell under pulsed laser and the differential response photoelectric signal under irradiation of interval light are measured. The origins of these two types of photoelectric responses and their correlations are analyzed. The pulse response signal initiates from the ultrafast charge separation of the retinal and the proton translocation followed by the deprotonation and reprotonation of the Schiff base and its surrounding amino acids. This is a quick response and is the preceding reaction of the differential response. The differential response signal is caused by the charging and discharging of the continuous proton current of the BR light-driven proton pump at light-on and light-off, which is a slow process. The differential response is related to not only the construction of the BR photocell but also the coupling mode of measurement. To observe the differential response signal, the BR photocell must have large enough B3 and B3' components in its pulse response as well as an alternative coupling mode to measure it.     

Xanthane sesquiterpenoids from the roots and flowers of Xanthium cavanillesii

The sesquiterpene lactones xanthanodiene, 4-epi-xanthanol, 4-epi-isoxanthanol, and 4-epi-xanthinin, as well as the xanthanolide derivative 4-oxo-bedfordia acid were isolated from the chloroform extracts of roots and flowers of Xanthium cavanillesii Schouw. The identities of these compounds were corroborated through comparison of their spectroscopic data, including IR, MS, and ¹H and ¹³C NMR assignments, with literature reports. In addition, the structural characterization of 4-oxo-bedfordia acid was revisited and a comprehensive spectroscopic study of the compound is presented. This is to our knowledge the first phytochemical investigation of the roots of X. cavanillesii, and of flowers in the whole Xanthium genus.     

Synthesis of N-substituted cyclic triglycines and their response to metal ions

N,N^′,N^″-Trisubstituted-cyclo-triglycines were synthesized. The major conformation of these compounds has C₃ symmetry, and the carbonyl groups and substituents on the nitrogen are inclined in the same direction. Their response to various metal ions was estimated by constructing ion-selective electrodes. Two of them responded selectively to Ca²⁺ over other cations, demonstrating that N,N^′,N^″-trisubstituted-cyclo-triglycines provide a new scaffold to act as host molecules.     

Quantitation of polyamines in cultured cells and tissue homogenates by reversed-phase high-performance liquid chromatography of their benzoyl derivatives

A rapid and simple method, originally described by Redmond and Tseng [J. Chromatogr., 170 (1979) 479] was applied to the analysis of di- and polyamines in cultured human tumour cells and human tumour xenografts. Optimization of the procedures and evaluation of the characteristic features of the assay are described. The (modified) procedure employs precolumn derivatization with benzoyl chloride, extraction of the derivatives by chloroform, separation by reversed-phase high-performance liquid chromatography under isocratic conditions and detection by ultraviolet absorbance measurement at 229 nm. The complete analysis was accomplished within 10 min per sample. The detection limit was ca. 1 pmol. The intra- and inter-assay coefficients of variation were 2.5-4.4% and 3.4-13.1%, respectively. The presence of well known inhibitors of polyamine biosynthesis, such as DL-alpha-difluoromethylornithine and methylglyoxal bis(guanylhydrazone), did not interfere with the assay, and disturbance by cyclohexylamine could be avoided by changing the polarity of the mobile phase. The method proved to be very suitable because it is rapid, simple, requires a minimum of sample pretreatment, and still provides sufficient sensitivity to quantitate polyamines in relatively small amounts of cells (10(5) cells) or tumour tissues (less than 1 mg), even after treatment with inhibitors of polyamine biosynthesis.     

Determination of di-and polyamines by high-performance liquid chromatographic separation of their 5-dimethylaminonaphthalene-1-sulfonyl derivatives

Using a Lichrosorb RP-8 reversed-phase column and a methanol--water gradient elution program, it is possible to separate within 40 min and to determine routinely in picomole quantities the natural di- and polyamines. The precision of the method is comparable to the thin-layer chromatographic procedures, the separations are most efficient, and the method can be fully automated. A modified gradient enables the repeated assay of spermidine and spermine within 20 min. The method is suited for polyamine analyses in tissues and body fluids.     

Micellar electrokinetic chromatography of polyamines and monoacetylpolyamines

A selective procedure for qualitative and quantitative analysis of ten polyamines by micellar electrokinetic chromatography (MEKC) was developed. Benzoylated polyamines and acetylpolyamines in micellar phase of SDS (10 mM) were separated at 25 degrees C by 20 mM borate buffer pH 8.5, containing 8% ethanol, with an applied voltage of 25 kV (5 microA) and then detected at 198 nm. The experimental factors and operational parameters were optimized by performing analysis at different surfactant concentrations, pH, voltage and temperature with and without ethanol. The repeatibility of migration times and peak heights is a peculiarity of the method here described.     

Chemical properties of polyamines with relevance to the biomineralization of silica

Polyamines mimicking substances which occur naturally in biosilicas have been synthesized and show an accelerating effect on silica condensation, which depends on the chemical nature, the architecture (linear or branched), and the degree of polymerization.     

Chelation of carbocations by polyethers and polyamines

Chelates formed by carbocations and cyclic polyethers and polyamines are studied with semiempirical and ab initio MO methods.