Multiple and Variable Binding of Pharmacologically Active Bis(maltolato)oxidovanadium(IV) to Lysozyme

The interaction with proteins of metal-based drugs plays a crucial role in their transport, mechanism, and activity. For an active MLn complex, where L is the organic carrier, various binding modes (covalent and non-covalent, single or multiple) may occur and several metal moieties (M, ML, ML2, etc.) may interact with proteins. In this study, we have evaluated the interaction of [VIVO­(malt)2] (bis­(maltolato)­oxidovanadium­(IV) or BMOV, where malt = maltolato, i.e., the common name for 3-hydroxy-2-methyl-4H-pyran-4-onato) with the model protein hen egg white lysozyme (HEWL) by electrospray ionization mass spectrometry, electron paramagnetic resonance, and X-ray crystallography. The multiple binding of different V-containing isomers and enantiomers to different sites of HEWL is observed. The data indicate both non-covalent binding of cis-[VO­(malt)2(H2O)] and [VO­(malt)­(H2O)3]+ and covalent binding of [VO­(H2O)3–4]2+ and cis-[VO­(malt)2] and other V-containing fragments to the side chains of Glu35, Asp48, Asn65, Asp87, and Asp119 and to the C-terminal carboxylate. Our results suggest that the multiple and variable interactions of potential VIVOL2 drugs with proteins can help to better understand their solution chemistry and contribute to define the molecular basis of the mechanism of action of these intriguing molecules

Effect of Equatorial Ligand Substitution on the Reactivity with Proteins of Paddlewheel Diruthenium Complexes: Structural Studies

The paddlewheel [Ru2Cl(O2CCH3)4] complex was previously reported to react with the model protein hen egg white lysozyme (HEWL), forming adducts with two diruthenium moieties bound to Asp101 and Asp119 side chains upon the release of one acetate. To study the effect of the equatorial ligands on the reactivity with proteins of diruthenium compounds, X-ray structures of the adducts formed when HEWL reacts with [Ru2Cl(D-p-FPhF)(O2CCH3)3] [D-p-FPhF = N,N′-bis(4-fluorophenyl)formamidinate] under different conditions were solved. [Ru2Cl(D-p-FPhF)(O2CCH3)3] is bonded through their equatorial positions to the Asp side chains. Protein binding occurs cis or trans to D-p-FPhF. Lys or Arg side chains or even main-chain carbonyl groups can coordinate to the diruthenium core at the axial site. Data help to understand the reactivity of paddlewheel diruthenium complexes with proteins, providing useful information for the design of new artificial diruthenium-containing metalloenzymes with potential applications in the fields of catalysis, biomedicine, and biotechnology

Inside out <i>Porphyridium cruentum</i>: Beyond the Conventional Biorefinery Concept

Here, an unprecedented biorefinery approach has been designed to recover high-added value bioproducts starting from the culture ofPorphyridium cruentum. This unicellular marine red alga can secrete and accumulate high-value compounds that can find applications in a wide variety of industrial fields. 300 ± 67 mg/L of exopolysaccharides were obtained from cell culture medium; phycoerythrin was efficiently extracted (40% of total extract) and isolated by single chromatography, with a purity grade that allowed the crystal structure determination at 1.60 Å; a twofold increase in β-carotene yield was obtained from the residual biomass; the final residual biomass was found to be enriched in saturated fatty acids. Thus, for the first time, a complete exploitation ofP. cruentumculture was set up