Polystyrene resins with immobilized polyamines: Preparation,characterization, and ability to bind Cu(II) ions

Three polyamine ligands, ethylenediamine (EDA), diethylenetriamine (DTA), and triethylenetetramine (TETA), were bound to three chloromethylated “popcorn” polystyrene resins (16, 50, and 100% phenyl ring substitution) with the use of pyridine as the reaction medium. The rate of chloride displacement decreased with increasing molecular weight of the amine and higher degree of resin chloromethylation, while the extent of multiple attachments to the polymer matrix increased. The additional crosslinking, a result of multiple attachments, caused the polyamine resins to swell to a lesser extent in pyridine and water. The ability of the insoluble polyamine–polystyrene resins to chelate Cu²⁺ ions from dilute solutions (200 ppm) was determined at pH 5. With EDA resins the capacity for Cu²⁺ increased with increasing amount of the bound polyamine, with DTA it remained unchanged, while with TETA it was found to decrease.     

Understanding the factors controlling the photo-oxidation of natural DNA by enantiomerically pure intercalating ruthenium polypyridyl complexes through TA/TRIR studies with polydeoxynucleotides and mixed sequence oligodeoxynucleotides

Ruthenium polypyridyl complexes which can sensitise the photo-oxidation of nucleic acids and other biological molecules show potential for photo-therapeutic applications. In this article a combination of transient visible absorption (TrA) and time-resolved infra-red (TRIR) spectroscopy are used to compare the photo-oxidation of guanine by the enantiomers of [Ru(TAP)₂(dppz)]²⁺ in both polymeric {poly(dG-dC), poly(dA-dT) and natural DNA} and small mixed-sequence duplex-forming oligodeoxynucleotides. The products of electron transfer are readily monitored by the appearance of a characteristic TRIR band centred at ca. 1700 cm⁻¹ for the guanine radical cation and a band centered at ca. 515 nm in the TrA for the reduced ruthenium complex. It is found that efficient electron transfer requires that the complex be intercalated at a G-C base-pair containing site. Significantly, changes in the nucleobase vibrations of the TRIR spectra induced by the bound excited state before electron transfer takes place are used to identify preferred intercalation sites in mixed-sequence oligodeoxynucleotides and natural DNA. Interestingly, with natural DNA, while it is found that quenching is inefficient in the picosecond range, a slower electron transfer process occurs, which is not found with the mixed-sequence duplex-forming oligodeoxynucleotides studied.

Efficient electron transfer requires the complex to be intercalated at a G-C base-pair. Identification of preferred intercalation sites is achieved by TRIR monitoring of the nucleobase vibrations before electron transfer.     

Investigation of the behavior of arenediazonium salts with olefins in BmimPF6

The palladium-catalyzed reactions of olefins with arenediazonium salts in ionic liquids were investigated. For methyl acrylate and methyl acrylonitrile, normal Heck cross-coupling products are obtained in good yields. However, highly selective dimerization products are formed in excellent yields for styrenes. The catalyst system can be recycled.     

A convenient synthesis of cis and trans 4-tert-butoxycarbonyl-substituted cyclohexylglycine

A novel synthesis of cis and trans substituted 4-tert-butoxycarbonyl cyclohexylglycines via asymmetric aminohydroxylation of vinyl styrene followed by reduction of the aromatic ring and subsequent oxidation is reported.     

13C-NMR relaxation studies of alkali metal cryptate complexes

The ¹³C spin-lattice relaxation times (T₁'s) of cryptands [2.1.1], [2.2.1] and [2.2.2] as well as those of the corresponding cryptate complexes with Li⁺, Na⁺, and K⁺ in CDCl₃ and CH₃OH:D₂O (90:10) were measured and the results are interpreted in terms of molecular compression and desolvation effects.     

STRUCTURE OF DYE AGGREGATES AND THE MECHANISM(S) OF PHOTOSENSITIZATION OF AgBr*,†

Abstract— This paper reports the present conclusions of an extended investigation on photo-sensitization of silver bromide. A general molecular packing structure for dye aggregates on the AgBr (111) surface is proposed. This structure, along with the observed spectral absorption displacements of small aggregates, is used to elucidate the phenomena of antisensitization and supersensitization. Supersensitization is seen as a partitioning of large dye aggregates into small aggregates by a deliberately added second component or by gaps between the aggregates. This partitioning isolates antisensitizing dye in a small fraction of the aggregates and minimizes its effect. The smallest aggregates are least likely to contain an antisensitizer, and show the highest quantum efficiency for photoconductivity and photographic action. Photoconductivity measurements establish that supersensitization occurs before the electron appears in the AgBr phase.
The question of direct electron injection vs. energy transfer as mechanisms for AgBr photosensitization is examined in terms of radiationless transfer to surface Ag₂S on AgBr. The absorption of surface Ag₂S is shown to be adequate for acceptance of Förster transfer from the dye, and surface Ag₂S is known to be photographically active. However, this mechanism is inefficient, and inadequate to account for observed high efficiency infrared sensitization. Direct electron injection is seen as the more probable mechanism for efficient dye sensitization of AgBr.     

Detection and assessment of citrus tristeza virus antigens by computer-aided scanning densitometry

Citrus tristeza virus (CTV) extracted from Etrog citron (C.medica L.) was immunoprecipitated. The immunoprecipitate was fractionated by SDS-PAGE and western blotted onto nitrocellulose. The CTV antigens were determined by immunoblot analysis using rabbit anti-CTV IgG, and the protein-band pattern exhibited on the nitrocellulose was assessed by soft-laser scanning densitometry. The densitometric tracing revealed the presence of bands that were not visible to the naked eye. Using the superimposition mode of the instrument, it was also revealed that the protein-band patterns of different CTV samples were not identical. Computer-aided soft-laser scanning densitometry proved to be a powerful approach in the detection and assessment of protein bands revealed on nitrocellulose immunoblots, which we were previously unable to do employing conventional methods.     

On the relocation of the amino functionality to the ethyl side chain in aminoglutethimide: Synthesis and aromatase-inhibitory activity of 3-(2′-N,N-diethyl-amino)ethyl-3-phenylpiperidine-2,6-dione

Aminoglutethimide [3-(4-aminophenyl)-3-ethylpiperidine-2,6-dione] has been used clinically in the treatment of metastatic breast carcinoma. Inhibition of tumor growth is due to interference with estrogen biosynthesis. However, its action is not specific and its metabolism gives rise to toxic and non-inhibitory metabolites. We sought to explore the impact of relocating the amino group in aminoglutethimide to the ethyl side chain. To that end, we now report the synthesis and aromatase-inhibitory activity of 3-(2′-N,N-diethylamino)ethyl-3-phenylpiperidine-2,6-dione 5. The introduction of the amino functionality on the ethyl group is accomplished via reductive animation of aldehyde 8, prepared in three steps from benzyl cyanide. The synthetic route presented can be used for the preparation of related derivatives of aminoglutethimide.     

Accurate determination of pyridine-poly(amidoamine) dendrimer absolute binding constants with the OPLS-AA force field and direct integration of radial distribution functions

OPLS-AA force field and direct integration of intermolecular radial distribution functions (RDF) were employed to calculate absolute binding constants of pyridine molecules to amino group (NH2) and amide group hydrogen atoms in and first generation poly(amidoamine) dendrimers in chloroform. The average errors in the absolute and relative association constants, as predicted with the calculations, are 14.1% and 10.8%, respectively, which translate into ca. 0.08 and 0.06 kcal/mol errors in the absolute and relative binding free energies. We believe that this level of accuracy proves the applicability of the OPLS-AA, force field, in combination with the direct RDF integration, to reproducing and predicting absolute intermolecular association constants of low magnitudes (ca. 0.2-2.0 range).     

Preparation and properties of some α-aza-amino-acid derivatives,their possible use in peptide synthesis

Some derivatives of azaglycine and azaphenylalanine are described. Esters of acetyl- and benzoyl-aza-amino-acids rapidly cyclise to stable oxadiazolones and it is concluded that similar derivatives would be unsuitable for aza-peptide synthesis. t-Butyloxycarbonyl-azaglycine azide was too unreactive for use in peptide synthesis. Benzoyl-azaglycylphenylalanine ethyl ester and acetyl-azaphenylalanylphenylalanine ethyl ester were prepared by coupling benzoyl hydrazide and N-acetyl-N'-benzylhydrazide respectively with 2,4-dinitrophenyloxycarbonyl-phenylalanine ethyl ester.