Raphael Enoque Ferraz de Paiva

Synthesis, spectroscopic characterization, DFT studies, and initial antibacterial assays in vitro of a new palladium(II) complex with tryptophan

A new palladium(II) complex with the amino acid L-tryptophan (Pd-TRP) was synthesized in aqueous solution and characterized by chemical and spectroscopic methods. Elemental, ESI-QTOF mass spectrometric, and thermal analyses of the solid compound permitted proposing the [Pd(C11H11N2O2)2] · 2H2O composition. Infrared, Raman, and UV-Vis spectroscopic data indicate the coordination of the ligand to Pd(II) through monodentate oxygen of carboxylate and through nitrogen of the amino group. The 1H and 13C NMR spectroscopic data confirm coordination through the carboxylate, while 15N NMR data confirm coordination of nitrogen of NH2. Density functional theory studies confirmed nitrogen and oxygen coordination to palladium(II) as a minimum of the potential energy surface with calculations of the hessians showing no imaginary frequencies. Biological studies were performed to provide information concerning the antibacterial activities of the compound. The Pd-TRP complex was shown to be active against Gram-positive and Gram-negative pathogenic bacterial strains.

A binuclear silver complex with l -buthionine sulfoximine: synthesis, spectroscopic characterization, DFT studies and antibacterial assays

A binuclear silver(I) complex with the amino acid L-buthionine sulfoximine (BSO) of composition Ag2C8H16N2O3S was synthesized and characterized by chemical and spectroscopic measurements, and DFT (density functional theory) studies. Solid-state 13C nuclear magnetic resonance (SSNMR) and infrared vibrational spectroscopy (IR) analyses indicate the coordination of the nitrogen and carboxylate groups of the amino acid moiety to one of the silver atoms, while coordination to the second silver atom occurs through the nitrogen of the sulfoximine group. ESI-QTOF-MS measurements show the maintenance of the binuclear structure in solution. DFT studies confirm the proposed structure as a minimum of the potential energy surface (PES) with calculations of the hessians showing no imaginary frequencies. Raman spectroscopic measurements of the [Ag2(BSO)] complex led to the assignments of the Ag–N bonds. Biological assays of BSO and [Ag2(BSO)] were performed by the well-diffusion method over Staphyloccocus aureus (Gram-positive), Escherichia coli and Pseudomonas aeruginosa (Gram-negative) bacterial strains. The ligand was inactive under the tested concentration (100 μg mL−1). The [Ag2(BSO)] complex was active against the Gram-negative and Gram-positive bacteria tested, with MIC values of 3.125 μg mL−1.

A new platinum complex with tryptophan: Synthesis, structural characterization, DFT studies and biological assays in vitro over human tumorigenic cells

A new platinum(II) complex with the amino acid L-tryptophan (trp), named Pt-trp, was synthesized and characterized. Elemental, thermogravimetric and ESI-QTOF mass spectrometric analyses led to the composition [Pt(C11H11N2O2)2]⋅6H2O. Infrared spectroscopic data indicate the coordination of trp to Pt(II) through the oxygen of the carboxylate group and also through the nitrogen atom of the amino group. The (13)C CP/MAS NMR spectroscopic data confirm coordination through the oxygen atom of the carboxylate group, while the (15)N CP/MAS NMR data confirm coordination of the nitrogen of the NH2 group to the metal. Density functional theory (DFT) studies were applied to evaluate the cis and trans coordination modes of trp to platinum(II). The trans isomer was shown to be energetically more stable than the cis one. The Pt-trp complex was evaluated as a cytotoxic agent against SK-Mel 103 (human melanoma) and Panc-1 (human pancreatic carcinoma) cell lines. The complex was shown to be cytotoxic over the considered cells.

Diversity in Gold Finger Structure Elucidated by Traveling‐Wave Ion Mobility Mass Spectrometry

Traveling wave ion mobility (TWIM) mass spectrometry (MS) is a powerful method for the structural and conformational analysis of proteins and peptides, enabling the differentiation of isomeric peptides (or proteins) that have the same sequence but are modified at different residues. In this study, the TWIM-MS technique was used to separate isomeric AuI metallopeptide ions that were formed by ZnII displacement from the parent zinc fingers (ZFs). The synthetic gold finger peptides were derived from the C-terminus of the HIV nucleocapsid p7 protein (NCp7-F2) and finger 3 of the Sp1 transcription factor (Sp1-F3). TWIM-MS enabled the acquisition of distinct product ion spectra for each isomer, clearly indicating the binding sites for the major conformers in the presence of multiple coordination possibilities. Collision cross-section measurements showed that the aurated peptide has a slightly more compact structure than the parent zinc compound NCp7-F2, which showed only one conformation.

Chemical, spectroscopic characterization, DFT studies and antibacterial activities in vitro of a new gold(I) complex with rimantadine

A novel gold(I) complex with rimantadine (RTD) was obtained and structurally characterized by a set of chemical and spectroscopic analysis. 1H, 13C and 15N nuclear magnetic resonance (NMR) and infrared (IR) spectroscopic measurements suggest coordination of the ligand to Au(I) through the N atom of the ethanamine group. Theoretical (DFT) calculations confirmed the IR assignments and permit proposing an optimized geometry for the complex. The gold(I)-rimantadine complex (Au-RTD) is soluble in methanol, ethanol, dimethylsulfoxide, acetone and acetonitrile. The preliminary kinetic studies based on UV-vis spectroscopic measurements indicate the stability of the compound in solution. Antibacterial activities of the complex were evaluated by an antibiogram assay. The Au-RTD complex showed an effective in vitro antibacterial activity against the Pseudomonas aeruginosa, Escherichia coli (Gram-negative), and Staphylococcus aureus (Gram-positive) bacterial strains.

Gold‐Catalyzed C–S Aryl‐Group Transfer in Zinc Finger Proteins

Reaction of the Au-C N chelate [Au(bnpy)Cl2 ] with the full-length zinc finger (ZnF; ZnCys3 His) of HIV nucleocapsid protein NCp7 results in C-S aryl transfer from the AuIII organometallic species to a cysteine of the ZnF. The reaction is general and occurs even for finger 3 of the transcription factor Sp1, containing a ZnCys2 His2 coordination sphere. This reaction is the first demonstration of group transfer from a coordination compound to biologically important zinc fingers, and is especially noteworthy for the ZnCys2 His2 transcription factors. The work expands the corpus of organometallic species which can efficiently modify biomolecules through C-atom transfer. The electronic features of the gold compound leading to this unexpected reaction were explored by X-ray absorption spectroscopy.

Crystal structure and cytotoxic activities of a bis(pyrrolyl-imine) gold(III) complex

Abstract A gold(III) complex with N,N′-ethylenebis(pyrrol-2-yl-methyleneamine) (H2pyren) was synthesized and characterized by physicochemical and spectroscopic measurements. Density functional theory (DFT) studies and cytotoxic assays were performed. Infrared, mass spectrometry, and 1H, 13C, and {15N,1H} nuclear magnetic resonance analyses indicate that pyren is deprotonated and gold(III) is four coordinate in a square planar environment, with the pyrrole and imine nitrogens as donors. The structure was confirmed by powder X-ray diffraction and confirmed as a minimum of the potential energy surface by DFT. Cytotoxic activity of [Au(pyren)]+ was active against three tumorigenic cell lines with IC50 values of 35 μM. Interaction studies with CT-DNA by fluorescence and competition with ethidium bromide (EB) showed a quenching of the emission band of DNA with a Stern–Volmer quenching constant value of (3.0 ± 0.1) × 104 M−1 and a decrease in fluorescence quenching of EB-DNA system, respectively, confirming that DNA is a possible target for the complex via an intercalative binding, which was confirmed by DNA conformational changes observed with circular dichroism spectroscopy.

N,N′,N′′ versus N,N′,O imine-containing coordination motifs: ligand-directed synthesis of mononuclear and binuclear CuII compounds

It is shown that tridentate imine ligands can control the nuclearity of copper(II) complexes based on the donor atoms present in the ligand. While the N,N′,N′′-donating imine ligand led to a mononuclear compound, the N,N′,O-donating imine ligand produced a binuclear metal complex.