Search results for "Polyamines"

Hormonal regulation of S-adenosylmethionine synthase transcripts in pea ovaries

1996

Two cDNA clones coding for S-adenosyl-L-methionine synthase (SAMs, EC 2.5.1.6) have been isolated from a cDNA library of gibberellic acid-treated unpollinated pea ovaries. Both cDNAs were sequenced showing a high degree of identity but coding for different SAMs polypeptides. The presence of two SAMs genes in pea was further confirmed by Southern analysis. Expression of the SAMs genes in the pea plant was found at different levels in vegetative and reproductive tissues. We characterized the expression levels of SAMs genes during the development or senescence of pea ovaries. Northern analysis showed that transcription of SAMs genes in parthenocarpic fruits was upregulated by auxins in the sam…

RGD-mimic polyamidoamine-montmorillonite composites with tunable stiffness as scaffolds for bone tissue-engineering applications

2017

This paper reports on the development of montmorillonite (MMT)-reinforced hydrogels, based on a peptidomimetic polyamidoamine carrying guanidine pendants (AGMA1), as substrates for the osteo-induction of osteoblast precursor cells. AGMA1 hydrogels of various degrees of crosslinking responded favourably to MMT reinforcement, giving rise to composite hydrogels with shear storage modulus G', when fully swollen in water, up to 200 kPa, i.e. 20 times higher than the virgin hydrogels and of the same order or higher than other hydrogel-based composites proposed for orthopaedic applications. This significant improvement was ascribed to the effective interpenetration between the polymer matrix and t…

New Insight to the Chemistry of Polyaza[n]paracyclophanes. A 15N NMR Study

2001

Development and in vitro Evaluation of Antigen-Loaded Poly(amidoamine) Nanoparticles for Respiratory Epithelium Applications

2013

A poly(amidoamine) with disulfide linkages in the main chain and 4-hydroxybutyl and ω-carboxy-PEG groups (9:1 ratio) as side chains was prepared by Michael addition polymerization of cystamine bisacrylamide with 4-hydroxybutylamine and ω-carboxy-PEG-amine. To develop therapeutic protein formulations for improved delivery of antigen via the intranasal route, nanoparticles were prepared from this polymer by self-assembly with p24 or ovalbumin as the model proteins and CpG as the adjuvant. The nanoparticles incorporated the antigens and adjuvant from the feed solution with high efficiency (∼90 %) and have sizes of 112 and 169 nm, respectively, with low positive surface charge (∼+2 mV). Formula…

o-Phthalaldehyde–N-acetylcysteine polyamine derivatives: formation and stability in solution and in C18 supports

2001

A comparative study of different derivatization procedures has been performed in order to improve the stability of the reaction products o-phthalaldehyde-N-acetylcysteine (OPA-NAC) polyamines. Procedures such as solution derivatization, solution derivatization followed by retention on a packing support, derivatization on different packing supports and on-column derivatization, have been optimized and compared. The degradation rate constant (k) of the derivative was dependent on the procedure used and on the analyte. For the spermine (the most unstable isoindol tested) k was 8 +/- 2 x 10(-2) min(-1) in solution versus 7.7 +/- 1.1 x 10(-4) min(-1) on the (C18) solid support. The results obtai…

Polyfunctional recognition of pyridinedicarboxylate anions with macrocyclic polyamine receptors containing heteroaromatic groups.

2008

The interaction of the biologically relevant anions deriving from the six pyridinedicarboxylic acids (H2PDC) with two macrocyclic receptors containing a pentamine chain and a bipyridine (1) or a phenanthroline (2) moiety, as well as with the aliphatic analogue [21]aneN7 (3), was studied by means of spectroscopic methods (UV-vis, NMR) and potentiometric titrations affording the stability constants of the adducts formed. All three receptors form stable complexes with the substrates thanks to the formation of several salt bridges and hydrogen bond contacts, as observed in the crystal structure of the H8[3(2,6-PDC)4] x H2O x 0.5 EtOH solid compound. Additional pi-stacking interactions between t…

Toward a Rational Design of Polyamine-Based Zinc-Chelating Agents for Cancer Therapies.

2020

In vitro viability assays against a representative panel of human cancer cell lines revealed that polyamines L1a and L5a displayed remarkable activity with IC50 values in the micromolar range. Preliminary research indicated that both compounds promoted G1 cell cycle arrest followed by cellular senescence and apoptosis. The induction of apoptotic cell death involved loss of mitochondrial outer membrane permeability and activation of caspases 3/7. Interestingly, L1a and L5a failed to activate cellular DNA damage response. The high intracellular zinc-chelating capacity of both compounds, deduced from the metal-specific Zinquin assay and ZnL2+ stability constant values in solution, strongly sup…

Electrochemistry of copper complexes with macrocyclic polyamines containing pyrazole units.

2006

The voltammetric behaviour of bi- and mono-nuclear complexes formed in solution by Cu(2+) with three polyazacyclophanes containing pyrazole units in aqueous solution is described. Cyclic and square wave voltammetric responses at glassy carbon electrodes indicate that the reduction of copper-macrocycle complexes in solution takes place in two successive one-electron per Cu transfer processes coupled with preorganization and protonation reactions that mimic the behaviour of superoxide dismutase. The electrochemistry of ternary Cu(2+)-receptor-dopamine complexes exhibits significant differences with respect to the protection of the neurotransmitter from post-electron transfer cyclization react…

Polyamines Impair Immunity to Helicobacter pylori by Inhibiting L-Arginine Uptake Required for Nitric Oxide Production

2010

International audience; BACKGROUND & AIMS: Helicobacter pylori-induced immune responses fail to eradicate the bacterium. Nitric oxide (NO) can kill H pylori. However, translation of inducible NO synthase (iNOS) and NO generation by H pylori-stimulated macrophages is inhibited by the polyamine spermine derived from ornithine decarboxylase (ODC), and is dependent on availability of the iNOS substrate L-arginine (L-Arg). We determined if spermine inhibits iNOS-mediated immunity by reducing L-Arg uptake into macrophages. METHODS: Levels of the inducible cationic amino acid transporter (CAT) 2, ODC, and iNOS were measured in macrophages and H pylori gastritis tissues. L-Arg uptake, iNOS expressi…

Cu2+and AMP complexation of enlarged tripodal polyamines

2006

The synthesis, characterization, Cu2+ coordination and interaction with AMP of three tripodal polyamines are reported. The polyamines are based on the structure of the tetraamine (tren) which has been enlarged with three propylamino functionalities (TAL), with a further anthrylmethyl fragment at one of its terminal primary nitrogens (ATAL) or with naphthylmethyl fragments at its three ends (N3TAL). The protonation constants of all three polyamines show that at pH 6, all six primary and secondary nitrogen atoms in the arms are protonated. The interaction with Cu2+ and AMP (adenosine-5′-monophosphate) has been studied by potentiometric, UV-Vis, ESI-MS spectroscopy and NMR techniques. pH-Metri…