On the correlation between electronic intramolecular delocalization and Au-S bonding strength of ruthenium tetraammine SAMs

Trans-[Ru(L)(NH3)4(L’)](PF6)n type complexes, where L = 4-cyanopyridine (CNpy), NCS-, CN-, and L’ = CNpy, 1,4-dithiane (1,4-dt), 4-mercaptopyridine (pyS) and thionicotinamide (tna), were synthesized and characterized. SAMs on gold of the complexes containing sulfur were studied by reductive desorption and SERS spectroscopy. Depending on the nature of L’, the withdrawing capability of the CNpy ligand is strong enough to partially oxidize the ruthenium atom and, as a consequence, delocalize the s electronic density from the trans located ligand. The reductive desorption results showed that the stability of the SAMs is directly related to this effect

[Fe(CN)5(isoniazid)]3−: an iron isoniazid complex with redox behavior implicated in tuberculosis therapy

Tuberculosis has re-emerged as a worldwide threat, which has motivated the development of new drugs. The antituberculosis complex Na3[Fe(CN)5(isoniazid)] (IQG607) in particular is of interest on account of its ability to overcome resistance. IQG607 has the potential for redox-mediated-activation, in which an acylpyridine (isonicotinoyl) radical could be generated without assistance from the mycobacterial KatG enzyme. Here, we have investigated the reactivity of IQG607 toward hydrogen peroxide and superoxide, well-known intracellular oxidizing agents that could play a key role in the redox-mediated-activation of this compound. HPLC, NMR and electronic spectroscopy studies showed a very fast oxidation rate for bound isoniazid, over 460-fold faster than free isoniazid oxidation. A series of EPR spin traps were used for detection of isonicotinoyl and derived radicals bound to iron. This is the first report for an isonicotinoyl radical bound to a metal complex, supported by 14N and 1H hyperfine splittings for the POBN and PBN trapped radicals. POBN and PBN exhibited average hyperfine coupling constants of aN = 15.6, aH = 2.8 and aN = 15.4, aH = 4.7, respectively, which are in close agreement to the isonicotinoyl radical. Radical generation is thought to play a major role in the mechanism of action of isoniazid and this work provides strong evidence for its production within IQG607, which, along with biological and chemical oxidation data, support a redox-mediated activation mechanism. More generally the concept of redox activation of metallo prodrugs could be applied more widely for the design of therapeutic agents with novel mechanisms of action

The inhibition of 5-enolpyruvylshikimate-3-phosphate synthase as a model for development of novel antimicrobials

EPSP synthase (EPSPS) is an essential enzyme in the shikimate pathway, transferring the enolpyruvyl group of phosphoenolpyruvate to shikimate-3-phosphate to form 5-enolpyruvyl-3-shikimate phosphate and inorganic phosphate. This enzyme is composed of two domains, which are formed by three copies of βαβαββ-folding units; in between there are two crossover chain segments hinging the nearly topologically symmetrical domains together and allowing conformational changes necessary for substrate conversion. The reaction is ordered with shikimate-3-phosphate binding first, followed by phosphoenolpyruvate, and then by the subsequent release of phosphate and EPSP. N-[phosphomethyl]glycine (glyphosate) is the commercial inhibitor of this enzyme. Apparently, the binding of shikimate-3-phosphate is necessary for glyphosate binding, since it induces the closure of the two domains to form the active site in the interdomain cleft. However, it is somehow controversial whether binding of shikimate-3-phosphate alone is enough to induce the complete conversion to the closed state. The phosphoenolpyruvate binding site seems to be located mainly on the C-terminal domain, while the binding site of shikimate-3-phosphate is located primarily in the N-terminal domain residues. However, recent results demonstrate that the active site of the enzyme undergoes structural changes upon inhibitor binding on a scale that cannot be predicted by conventional computational methods. Studies of molecular docking based on the interaction of known EPSPS structures with (R)- phosphonate TI analogue reveal that more experimental data on the structure and dynamics of various EPSPS-ligand complexes are needed to more effectively apply structure-based drug design of this enzyme in the future. © 2007 Bentham Science Publishers Ltd

Construction of Mycobacterium tuberculosis cdd knockout and evaluation of invasion and growth in macrophages

<div><p>Cytidine deaminase (MtCDA), encoded by cdd gene (Rv3315c), is the only enzyme identified in nucleotide biosynthesis pathway of Mycobacterium tuberculosis that is able to recycle cytidine and deoxycytidine. An M. tuberculosis knockout strain for cdd gene was obtained by allelic replacement. Evaluation of mRNA expression validated cdd deletion and showed the absence of polar effect. MudPIT LC-MS/MS data indicated thymidine phosphorylase expression was decreased in knockout and complemented strains. The cdd disruption does not affect M. tuberculosis growth both in Mid- dlebrook 7H9 and in RAW 264.7 cells, which indicates that cdd is not important for macrophage invasion and virulence.</p></div

IQG-607 inhibits <i>L</i>. <i>braziliensis</i> promastigotes proliferation.

<p>Cell viability of <i>L</i>. <i>braziliensis</i> LTCP 18483 (A, B), LTCP 20195 (C, D) and LTCP 19512 (E, F) strains, isolated from lesions of patients presenting cutaneous, mucosal and disseminated forms of leishmaniasis, respectively, in the presence of AMB or IQG-607, after 72 h of incubation. Data is represented by mean±SD; One-way ANOVA followed by Bonferroni’s post-test were used in the statistical analyses, *<i>P</i><0.05, **<i>P</i><0.01 and ***<i>P</i><0.001.</p

Cytotoxic activity of IQG-607 against cell lines.

<p>HepG2 (A), Vero (B) e HaCat (C) cells were treated with IQG-607 for 72 h and cell viability was assessed by neutral red uptake assay. DNA damage index (D) were measured by alkaline comet assay in HepG2 cell after 24 h of IQG-607 (1 mM) or MMS (0.1 mM; positive control) exposure. Data is represented by mean±SD. One-way ANOVA followed by Bonferroni’s post-test were used in the statistical analyses, *<i>P</i><0.05, **<i>P</i><0.01 and ***<i>P</i><0.001.</p

IQG-607 decreases the infection of macrophages by <i>L</i>. <i>braziliensis</i> amastigotes.

<p>Macrophages were infected with <i>L</i>. <i>braziliensis</i> (strains LTCP 18483 (A, B), LTCP 20195 (C, D) and LTCP 19512 (E, F) for 48 h in the presence or not of AMB and IQG-607. Percentage of infected macrophages and the number of parasites inside 100 cells are represented by median. One-way ANOVA followed by Bonferroni’s post-test were used in the statistical analyses, **<i>P</i><0.01 and ***<i>P</i><0.001.</p