Interaction of iron(II)-heme and artemisinin with a peptide mimic of Plasmodium falciparum HRP-II.

The interaction of heme or heme-artemisinin adducts (heme-art) with different peptides mimicking repeat sequences of the Histidine-Rich-Protein-II of Plasmodium falciparum (PfHRP-II) was investigated. The pseudo-first order rate constants of the coordination of heme or heme-art onto a histidine rich peptide, used as a mimic of PfHRP-II putative heme binding sequence, are of the same order of magnitude, namely 42 and 14 s(-1), respectively. Despite the intrinsic reactivity of the carbonyl at C10 of heme-art toward a hydroxyl function, a peptide containing a serine or threonine residue does not readily react with heme-art adducts.

Comprehensive investigation of the non-covalent binding of MRI contrast agents with human serum albumin.

Three techniques, electrospray mass spectrometry, ultrafiltration, and proton relaxometry, are compared in the context of the quantitative analysis of non-covalent binding between human serum albumin (HSA) and MRI contrast agents. The study of the affinity by proton relaxometry reveals the association constant and the number of interaction sites assuming that all sites are identical and independent. Ultrafiltration was adapted for the study of paramagnetic complexes.

From phage display to magnetophage, a new tool for magnetic resonance molecular imaging.

Phage display, an extremely promising technology in the context of molecular imaging, allows for the selection of peptides interacting with virtually any target from a heterogeneous mixture of bacteriophages. In this work, we propose the concept of magnetophages, obtained by covalent coupling of ultrasmall particles of iron oxide (USPIO) to the proteins of the phage wall. To validate magnetophages as a magnetic resonance imaging contrast agent (MRI), we have used as a prototype the clone E3 because of its specific affinity for phosphatidylserine, a marker of apoptosis.

Hybrid gadolinium oxide nanoparticles: multimodal contrast agents for in vivo imaging.

Luminescent hybrid nanoparticles with a paramagnetic Gd2O3 core were applied as contrast agents for both in vivo fluorescence and magnetic resonance imaging. These hybrid particles were obtained by encapsulating Gd2O3 cores within a polysiloxane shell which carries organic fluorophores and carboxylated PEG covalently tethered to the inorganic network. Longitudinal proton relaxivities of these particles are higher than the positive contrast agents like Gd-DOTA which are commonly used for clinical magnetic resonance imaging.

Comparative study of the physicochemical properties of six clinical low molecular weight gadolinium contrast agents.

This paper compares the physicochemical properties of six low molecular weight clinical complexes of gadolinium studied under identical experimental conditions. Magnevist, Dotarem, Omniscan, ProHance, MultiHance and Gadovist were investigated by oxygen-17 relaxometry at different temperatures and by proton relaxometry at various magnetic fields, temperatures and media [pure water, zinc(II)-containing aqueous solutions and HSA-containing solutions]. Osmolality, viscosity and stability versus transmetallation by zinc(II) ions were added for a more comprehensive description.

Specific E-selectin targeting with a superparamagnetic MRI contrast agent.

Targeting of the endothelial inflammatory adhesion molecule E-selectin by magnetic resonance imaging (MRI) was performed with a superparamagnetic contrast agent in the context of in vitro and in vivo models of inflammation. The specific contrast agent was obtained by grafting a synthetic mimetic of sialyl Lewis(x) (sLe(x)), a natural ligand of E-selectin expressed on leukocytes, on the dextran coating of ultrasmall particles of iron oxide (USPIO). This new contrast agent, called USPIO-g-sLe(x), was tested, in vitro, on cultured human umbilical vein endothelial cells (HUVECs) stimulated to express inflammatory adhesion molecules, and in vivo, on a mouse model of hepatitis.

Pharmacokinetic and in vivo evaluation of a self-assembled gadolinium(III)-iron(II) contrast agent with high relaxivity.

A high-molecular weight tetrametallic supramolecular complex [(Ln-DTPA-phen)3Fe]- (Ln = Gd, Eu, La) has been obtained upon self-assembly around one iron(II) ion of three 1,10-phenantroline-based molecules substituted in 5'-position with the polyaminocarboxylate diethylenetriamine-N,N,N',N',N'-pentaacetate, DTPA-phen(4-). The ICP-MS measurements indicated that the lanthanide:iron ratio is 3:1. Photoluminescence spectra of [Eu-DTPA-phen](-) and of [(Eu-DTPA-phen)3Fe]- are nearly identical, implying that the first coordination sphere of the lanthanide(III) ion has not been changed upon coordination of phenantroline unit to iron(II) ion.

Studying the signaling role of 2-oxoglutaric acid using analogs that mimic the ketone and ketal forms of 2-oxoglutaric acid.

2-Oxoglutaric acid (2-OG), a Krebs cycle intermediate, is a signaling molecule in many organisms. To determine which form of 2-OG, the ketone or the ketal form, is responsible for its signaling function, we have synthesized and characterized various 2-OG analogs. Only 2-methylenepentanedioic acid (2-MPA), which resembles closely the ketone form of 2-OG, is able to elicit cell responses in the cyanobacterium Anabaena by inducing nitrogen-fixing cells called heterocysts.

A dual lanthanide probe suitable for optical (Tb3+ luminescence) and magnetic resonance imaging (Gd3+ relaxometry).

A new polyaminocarboxylate ligand derived from N,C-pyrazolylpyridine was synthesized. The luminescence and relaxometry properties of its Tb(3+) and Gd(3+) chelates were investigated in aqueous solutions. The Tb(3+) chelate is strongly luminescent having remarkable lifetime and quantum yield (tau=1.

A new peptidic vector for molecular imaging of apoptosis, identified by phage display technology.

Phosphatidylserine (PS) exposure on the cell surface is an early marker of apoptosis. To select PS binding peptides as vectors of contrast agents to image apoptosis, a phage library has been exposed to perfused mouse livers. Phages not retained on control livers during the first perfusions were used for selections on apoptotic livers in a second series of perfusions.

Heterocyst differentiation and pattern formation in cyanobacteria: a chorus of signals.

Heterocyst differentiation in filamentous cyanobacteria provides an excellent prokaryotic model for studying multicellular behaviour and pattern formation. In Anabaena sp. strain PCC 7120, for example, 5-10% of the cells along each filament are induced, when deprived of combined nitrogen, to differentiate into heterocysts.

Bimodal system (luminophore and paramagnetic contrastophore) derived from Ln(III) complexes based on a bipyridine-containing macrocyclic ligand.

The synthesis of a new 15-membered polyaza-macrocyclic ligand L3H3, which is based on a 2,2'-bipyridine moiety and a diethylenetriaminetriacetic acid core, is reported. The lanthanide chelates of this octadentate ligand were programmed for bimodal probes, luminescent agents (Sm, Eu, Tb, Dy), and magnetic resonance imaging agents (Gd3+). The neutral 1:1 complexes with these Ln3+ ions were prepared and studied in aqueous solution by luminescence and NMR techniques.

Relaxometric study of copper [15]metallacrown-5 gadolinium complexes derived from alpha-aminohydroxamic acids.

Proton nuclear magnetic relaxation dispersion (NMRD) profiles were recorded between 0.24 mT and 1.4 T for lanthanum(III)- and gadolinium(III)-containing [15]metallacrown-5 complexes derived from alpha-aminohydroxamic acids and with copper(II) as the ring metal.

Paramagnetic liposomes containing amphiphilic bisamide derivatives of Gd-DTPA with aromatic side chain groups as possible contrast agents for magnetic resonance imaging.

Three amphiphilic DTPA bisamide derivatives containing long-chain phenylalanine esters (with 14, 16 and 18 carbon atoms in the alkyl chain) were synthesized and their corresponding gadolinium(III) complexes were prepared. The attempts to form paramagnetic micelles carrying the gadolinium(III) complexes yielded unstable or polydisperse micelles implying that the presence of the bulky aromatic side groups in the amphiphilic Gd-DTPA bisamide complexes results in an inefficient packing of the paramagnetic complex into micelles. All complexes were efficiently incorporated into liposomes consisting of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), yielding stable and monodisperse paramagnetic liposomes.

Postamputation pain and sensory changes in treatment-naive patients: characteristics and responses to treatment with tramadol, amitriptyline, and placebo.

Background: Pain after amputation is common but difficult to treat, and few controlled treatment studies exist.

Methods: In the current study, 94 treatment-naive posttraumatic limb amputees with phantom pain (intensity: mean visual analog scale score [0-100], 40 [95% confidence interval, 38-41]) were randomly assigned to receive individually titrated doses of tramadol, placebo (double-blind comparison), or amitriptyline (open comparison) for 1 month. Nonresponders were crossed over to the alternative active treatment.

Nonmetabolizable analogue of 2-oxoglutarate elicits heterocyst differentiation under repressive conditions in Anabaena sp. PCC 7120.

In response to combined nitrogen starvation in the growth medium, the filamentous cyanobacterium Anabaena sp. PCC 7120 is able to develop a particular cell type, called a heterocyst, specialized in molecular nitrogen fixation. Heterocysts are regularly intercalated among vegetative cells and represent 5-10% of all cells along each filament.

C-MALISA (cellular magnetic-linked immunosorbent assay), a new application of cellular ELISA for MRI.

A modified cellular ELISA (enzyme-linked immunosorbent assay), named cellular magnetic-linked immunosorbent assay (C-MALISA), has been developed as an application of magnetic resonance imaging (MRI) for in vitro clinical diagnosis. To validate the method, three contrast agents targeted to integrins were synthesized by grafting to USPIO (ultrasmall particles of iron oxide): (a) the CS1 (connecting segment-1) fragment of fibronectin (FN) (USPIO-g-FN); (b) the peptide GRGD (USPIO-g-GRGD); (c) a non-peptidic RGD mimetic (USPIO-g-mimRGD). Jurkat cells and rat mononuclear cells were stimulated to activate their integrins.

Magnetic resonance imaging of inflammation with a specific selectin-targeted contrast agent.

E-selectin-targeted contrast enhancement of blood vessels in inflamed tissues was investigated with a new contrast agent, Gd-DTPA-B(sLe(x))A, which was recently obtained by grafting a synthetic mimetic of sialyl-Lewis(x), an E-selectin ligand, onto Gd-DTPA. The pharmacokinetics, biodistribution, and potential to image inflammation by MRI of this E-selectin-targeted contrast agent were evaluated. The inhibition (by 15-34%) produced by Gd-DTPA-B(sLe(x))A on Sialyl Le(x)-PAA-biotin binding to E-selectin confirmed the specific interaction of the new contrast agent with this adhesion molecule.

Synthesis, characterization, and pharmacokinetic evaluation of a potential MRI contrast agent containing two paramagnetic centers with albumin binding affinity.

A dinuclear gadolinium(III) complex of an amphiphilic chelating ligand, containing two diethylenetriamine-N,N,N',N'',N''-pentaacetate (DTPA) moieties bridged by a bisindole derivative with three methoxy groups, has been synthesized and evaluated as a potential magnetic resonance imaging (MRI) contrast agent. Nuclear magnetic relaxation dispersion (NMRD) measurements indicate that at 20 MHz and 37 degrees C the dinuclear gadolinium(III) complex has a much higher relaxivity than [Gd(DTPA)] (6.8 vs 3.

Heme alkylation by artesunic acid and trioxaquine DU1301, two antimalarial trioxanes.

The sesquiterpene Artemisinin, an antimalarial drug that is effective against multidrug-resistant Plasmodium falciparum strains, contains a 1,2,4-trioxane, and the endoperoxide function plays a key role in its biological activity. However, its poor solubility means that hemisynthetic derivatives, such as artesunic acid, are preferred for drugs. The reductive activation of the peroxide function of artemisinin by iron(II)-heme produces heme derivatives that are alkylated at meso positions by a C-centered radical derived from artemisinin.

Cell-type specific modification of PII is involved in the regulation of nitrogen metabolism in the cyanobacterium Anabaena PCC 7120.

In the heterocystous cyanobacterium Anabaena PCC 7120, the modification state of the signalling PII protein is regulated according to the nitrogen regime of the cells, as already observed in some unicellular cyanobacteria. However, during the adaptation to diazotrophic growth conditions, PII is phosphorylated in vegetative cells while unphosphorylated in heterocysts. Isolation of mutants affected on PII modification state and analysis of their phenotypes allow us to show the implication of PII in the regulation of molecular nitrogen assimilation and more specifically, the requirement of unmodified state of PII in the formation of polar nodules of cyanophycin in heterocysts.

Investigation of non-covalent interactions between paramagnetic complexes and human serum albumin by electrospray mass spectrometry.

Stable gadolinium(III) chelates are nowadays routinely used as contrast agents for magnetic resonance imaging (MRI). Their non-covalent binding to human serum albumin (HSA) has shown to improve their efficacy. Non-covalent interactions lead to complex formation that can be quantified by several techniques that are mostly tedious and time-consuming.

MR molecular imaging of early endothelial activation in focal ischemia.

Focal ischemia followed by reperfusion initiates a harmful P- and E-selectin-mediated recruitment of leukocytes in brain microvasculature. In this study, we tested whether a novel magnetic resonance (MR) contrast agent (Gd-DTPA-sLe(x) A), which is designed to bind to activated endothelium could be detected by MR imaging (MRI) in a focal stroke mouse model. MRIs (9.

MRI detection of early endothelial activation in brain inflammation.

MRI is an increasingly important clinical tool, but it is clear that conventional imaging fails to identify the full extent of lesion load in certain conditions, such as multiple sclerosis. The aim of this study was to determine whether a novel contrast agent (Gd-DTPA-B(sLeX)A, which contains an sLeX mimetic moiety that enables it to bind to the adhesion molecule E-selectin) can be used to identify endothelial activation in the brain. Microinjection of the proinflammatory cytokines IL-1beta or TNF-alpha into the striatum of Wistar rats rapidly induces focal adhesion molecule expression on the endothelium in the absence of MRI-visible changes.