Tuning the Properties of Rigidified Acyclic DEDPA Derivatives for Application in PET Using Copper-64.

We present a detailed investigation of the coordination chemistry toward [Cu/Cu]copper of a series of HDEDPA derivatives (HDEDPA = 6,6'-((ethane-1,2-diylbis(azanediyl))bis(methylene))dipicolinic acid) containing cyclohexyl (HCHXDEDPA), cyclopentyl (HCpDEDPA) or cyclobutyl (HCBuDEDPA) spacers. Furthermore, we also developed a strategy that allowed the synthesis of a HCBuDEDPA analogue containing an additional NHBoc group at the cyclobutyl ring, which can be used for conjugation to targeting units. The X-ray structures of the Cu(II) complexes evidence distorted octahedral coordination around the metal ion in all cases.

Endeavor toward Redox-Responsive Transition Metal Contrast Agents Based on the Cross-Bridge Cyclam Platform.

We present the synthesis and characterization of a series of Mn(III), Co(III), and Ni(II) complexes with cross-bridge cyclam derivatives (CB-cyclam = 1,4,8,11-tetraazabicyclo[6.6.2]hexadecane) containing acetamide or acetic acid pendant arms.

On the dissociation pathways of copper complexes relevant as PET imaging agents.

Several bifunctional chelators have been synthesized in the last years for the development of new Cu-based PET agents for in vivo imaging. When designing a metal-based PET probe, it is important to achieve high stability and kinetic inertness once the radioisotope is coordinated. Different competitive assays are commonly used to evaluate the possible dissociation mechanisms that may induce Cu(II) release in the body.

Gold Nanoparticles as Colorimetric Sensors for the Detection of DNA Bases and Related Compounds.

Results regarding interaction of colloidal gold solutions with nucleobases, including uracil (U), as well as its sulfur derivatives, 2-thiouracil (2TU) and 4-thiouracil (4TU), cytosine (C), adenine (A), and guanine (G), as well as urea and thiourea (TU), are reported. Anionic stabilized citrate gold nanoparticles (AuNPs) were synthesized by reducing the tetrachloroaurate (III) trihydrate with trisodium citrate. The surface plasmon resonance (SPR) band was used in the characterization of synthesized AuNPs, as well as transmission electron microscope (TEM) imaging, which was used in the characterization of dispersed and aggregated gold nanoparticles.

A pentadentate member of the picolinate family for Mn(ii) complexation and an amphiphilic derivative.

We report a pentadentate ligand containing a 2,2'-azanediyldiacetic acid moiety functionalized with a picolinate group at the nitrogen atom (H3paada), as well as a lipophylic derivative functionalized with a dodecyloxy group at position 4 of the pyridyl ring (H3C12Opaada). The protonation constants of the paada3- ligand and the stability constant of the Mn(ii) complex were determined using a combination of potentiometric and spectrophotometric titrations (25 °C, 0.15 M NaCl).

Interaction of gold nanoparticles mediated by captopril and S-nitrosocaptopril: the effect of manganese ions in mild acid medium.

We report herein results regarding reactivity and assembly of citrate-capped gold nanoparticles (AuNPs) mediated by captopril (cap) and S-nitrosocaptopril (NOcap), two angiotensin converting enzyme inhibitors and antihypertensive agents. The results were compared with that of cysteine (Cys), a thiol-containing amino acid found in plasma. The interparticle interactions were characterized by monitoring the evolution of the surface plasmon resonance band using the spectrophotometric method.

A further study of acetylacetone nitrosation.

The nitrosation of acetylacetone (AcAc) has been revised in an aqueous acid medium of perchloric acid and buffers of mono-, di-, or tri-chloroacetic acid. The results show that in the presence of buffers, under conditions of [nit] ≪ [AcAc] (nit = sodium nitrite) the reaction cannot be studied by UV-Vis spectroscopy, contrary to the recently published paper by García-Rio et al. (J.

Optimization of production of chlamydospores of the nematode-trapping fungus Duddingtonia flagrans in solid culture media.

The large-scale production of nematophagous fungi as agents of biological control is one of the main challenges to be commercially used. In order to improve growth of microorganism in a culture medium, the addition of growth inducer is common. At the moment, the action of their addition in the mycelia growth and sporulation rate of nematophagous fungi is not known.

S-nitrosocaptopril formation in aqueous acid and basic medium. A vasodilator and angiotensin converting enzyme inhibitor.

The reaction of S-nitrosocaptopril (NOcap) formation was studied in both aqueous acid and basic medium. Captopril (cap) reacts rapidly with nitrous acid in strong acid medium to give the stable--in the timescale of the experiments--NOcap. The kinetic study of the reaction involving the use of stopped-flow, shows that at low sodium nitrite (nit) concentration, the reaction is first-order in both [nit], [H(+)], and is strongly catalysed by Cl(-) or Br(-) (= X(-)): rate = (k(3) + k(4)[X(-)])[H(+)][nit][cap].

Iron(III) complexation by Vanchrobactin, a siderophore of the bacterial fish pathogen Vibrio anguillarum.

The bacterial fish pathogen Vibrio anguillarum serotype O2 strain RV22 produces the mono catecholate siderophore Vanchrobactin (Vb) under conditions of iron deficiency. Vb contains two potential bidentate coordination sites: catecholate and salicylate groups. The iron(III) coordination properties of Vb is investigated in aqueous solutions using spectrophotometric and potentiometric methods.

Exploring the effect of supramolecular structures of micelles and cyclodextrins on fluorescence emission of local anesthetics.

Benzocaine (ethyl 4-aminobenzoate, 4) and its derivatives ethyl 2-aminobenzoate, 2, and ethyl 3-aminobenzoate, 3, were found to form association complexes with supramolecular structures of micelles and cyclodextrins (CDs). The fluorescence emission of 2, 3 or 4 dissolved in the pseudo-micellar phase or included into α-, β-, or γ-CD cavity increases dramatically with respect to that observed in only water. High percentages of organic solvents like dioxane, acetonitrile, DMSO in the aqueous solution lead to a similar effect.

Inclusion complexation of novocaine by beta-cyclodextrin in aqueous solutions.

The formation of inclusion complexes between beta-cyclodextrin (beta-CD) and the local anesthetic 2-(diethylamino)ethyl-p-amino-benzoate (novocaine) in aqueous solutions under different acidity conditions, using steady-state fluorescence or UV-vis spectroscopies, electrical conductivity, or the kinetic study of both the nitrosation reaction of the primary amine group in a mild acid medium and the hydrolysis of the ester function under an alkaline medium, has been studied. The inclusion complex formation between neutral or protonated novocaine and beta-CD of 1:1 stoichiometry was observed; however, the magnitude of the binding constants depends on the nature of both the guest and the host, and the higher-affinity guest-host was found under conditions when both the novocaine and the beta-CD were neutral molecules.

Nitrosation of 2-acetylcyclohexanone. 2. Reaction in water in the absence and presence of cyclodextrins.

The kinetic study of the nitrosation of the enol of 2-acetylcyclohexanone (ACHE) has been performed in aqueous acid media in the absence and presence of alpha- and beta-cyclodextrin. The reaction is first-order with respect to both reactants concentration: [nitrite] and [ACHE]; but, unexpectly, the dependence of both [H(+)] or [X(-)] (X(-) = Cl(-), Br(-), or SCN(-)) is not simple first-order. The experimental findings have been explained on the basis of a reaction mechanism that considers the formation of a chelate-nitrosyl complex intermediate in steady-state.

Tautomerization of 2-acetylcyclohexanone. 1. Characterization of keto-enol/enolate equilibria and reaction rates in water.

The keto-enol tautomerism of 2-acetylcyclohexanone (ACHE) was studied in water under different experimental conditions. By contrast with other previously studied beta-diketones, the keto-enol interconversion in the ACHE system is a slow process. Under equilibrium conditions, the analysis of the absorbance readings of ACHE aqueous solutions yielded more than 40% of enol content at 25 degrees C; nevertheless, in aprotic solvents such as dioxane, ACHE is almost completely enolized.