Current trend in synthesis, Post-Synthetic modifications and biological applications of Nanometal-Organic frameworks (NMOFs)

Since the early reports of MOFs and their interesting properties, research involving these materials has grown wide in scope and applications. Various synthetic approaches have ensued in view of obtaining materials with optimised properties, the extensive scope of application spanning from energy, gas sorption, catalysis biological applications has meant exponentially evolved over the years. The far‐reaching synthetic and PSM approaches and porosity control possibilities have continued to serve as a motivation for research on these materials. With respect to the biological applications, MOFs have shown promise as good candidates in applications involving drug delivery, BioMOFs, sensing, imaging amongst others. Despite being a while away from successful entry into the market, observed results in sensing, drug delivery, and imaging put these materials on the spot light as candidates poised to usher in a revolution in biology. In this regard, this review article focuses current approaches in synthesis, post functionalization and biological applications of these materials with particular attention on drug delivery, imaging, sensing and BioMOFs

Insight into the Bind-Lock Mechanism of the Yeast Mitochondrial ATP Synthase Inhibitory Peptide

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The binding mechanism of the yeast F1-ATPase inhibitory peptide. Role of catalytic intermediates and enzyme turnover.

International audienceThe mechanism of inhibition of yeast mitochondrial F(1)-ATPase by its natural regulatory peptide, IF1, was investigated by correlating the rate of inhibition by IF1 with the nucleotide occupancy of the catalytic sites. Nucleotide occupancy of the catalytic sites was probed by fluorescence quenching of a tryptophan, which was engineered in the catalytic site (beta-Y345W). Fluorescence quenching of a beta-Trp(345) indicates that the binding of MgADP to F(1) can be described as 3 binding sites with dissociation constants of K(d)(1) = 10 +/- 2 nm, K(d2) = 0.22 +/- 0.03 microm, and K(d3) = 16.3 +/- 0.2 microm. In addition, the ATPase activity of the beta-Trp(345) enzyme followed simple Michaelis-Menten kinetics with a corresponding K(m) of 55 microm. Values for the K(d) for MgATP were estimated and indicate that the K(m) (55 microm) for ATP hydrolysis corresponds to filling the third catalytic site on F(1). IF1 binds very slowly to F(1)-ATPase depleted of nucleotides and under unisite conditions. The rate of inhibition by IF1 increased with increasing concentration of MgATP to about 50 mum, but decreased thereafter. The rate of inhibition was half-maximal at 5 microm MgATP, which is 10-fold lower than the K(m) for ATPase. The variations of the rate of IF1 binding are related to changes in the conformation of the IF1 binding site during the catalytic reaction cycle of ATP hydrolysis. A model is proposed that suggests that IF1 binds rapidly, but loosely to F(1) with two or three catalytic sites filled, and is then locked in the enzyme during catalytic hydrolysis of ATP.The mechanism of inhibition of yeast mitochondrial F(1)-ATPase by its natural regulatory peptide, IF1, was investigated by correlating the rate of inhibition by IF1 with the nucleotide occupancy of the catalytic sites. Nucleotide occupancy of the catalytic sites was probed by fluorescence quenching of a tryptophan, which was engineered in the catalytic site (beta-Y345W). Fluorescence quenching of a beta-Trp(345) indicates that the binding of MgADP to F(1) can be described as 3 binding sites with dissociation constants of K(d)(1) = 10 +/- 2 nm, K(d2) = 0.22 +/- 0.03 microm, and K(d3) = 16.3 +/- 0.2 microm. In addition, the ATPase activity of the beta-Trp(345) enzyme followed simple Michaelis-Menten kinetics with a corresponding K(m) of 55 microm. Values for the K(d) for MgATP were estimated and indicate that the K(m) (55 microm) for ATP hydrolysis corresponds to filling the third catalytic site on F(1). IF1 binds very slowly to F(1)-ATPase depleted of nucleotides and under unisite conditions. The rate of inhibition by IF1 increased with increasing concentration of MgATP to about 50 mum, but decreased thereafter. The rate of inhibition was half-maximal at 5 microm MgATP, which is 10-fold lower than the K(m) for ATPase. The variations of the rate of IF1 binding are related to changes in the conformation of the IF1 binding site during the catalytic reaction cycle of ATP hydrolysis. A model is proposed that suggests that IF1 binds rapidly, but loosely to F(1) with two or three catalytic sites filled, and is then locked in the enzyme during catalytic hydrolysis of ATP

Fluorescence as a tool to understand changes in photosynthetic electron flow regulation

International audienceThe physiological state of a chloroplast is stronglyinfluenced by both biotic and abiotic conditions.Unfavourable growth conditions lead to photosyntheticstress. Chlorophyll a fluorescence is a widelyused probe of photosynthetic activity (specificallyPSII), and therefore stress which specifically targetsthe electron transport pathway and associated alternativeelectron cycling pathways. By manipulating theprocesses that control photosynthesis, affecting thechlorophyll a fluorescence, yields detailed insight intothe biochemicalpathways. Light that is captured by achlorophyll molecule can be utilised in three competingprocesses; electron transport, energy dissipation(via heat) and chlorophyll a fluorescence emission.Electrons produced by water-splitting are not alwaysused in carbon fixation; if the incident irradiancegeneratesmore electrons than the dark reactionscan use in carbon fixation, damage will occur to the photosynthetic apparatus. If carbon fixation is inhibitedby temperature or reduced inorganic carbon (Ci), ATPor NADPH availability, then the photosystem dynamicallyadjusts and uses alternate sinks for electrons, suchas molecular oxygen (water-water cycle or Mehler ascorbateperoxidase reaction). The process of stress acclimationleads to a number of photoprotective pathwaysand we describe how inhibitors can be used to identifythese particular processes. In this chapter, we describethe processes controlling electron transport as influencedby light-induced stress

A Metal–Organic Framework Based on a Tetra-Arylextended Calix[4]pyrrole Ligand: Structure Control through the Covalent Connectivity of the Linker

The preparation of isomeric metal–organic frameworks (MOFs) in which the network topology is controlled by the different covalent connectivities of the organic ligand is an important step forward in the design of new functional materials. In this context, macrocyclic organic ligands able to accommodate suitable guests in their own polar internal cavities are appealing candidates to act as multidentate linkers, which could potentially self-assemble into hierarchical porous structures. Taking this into account, here we report the first successful attempt to incorporate a tetraaryl-extended calix[4]­pyrrole derivative into a transition metal–organic framework (<b>calixMOF1</b>) by simply incorporating four terminal carboxylic functional groups at the upper rim of the macrocyclic scaffold. Remarkably, the structures of the metal organic framework and its transition-metal carboxylate clusters (secondary building units, SBU) are governed by the position of the carboxylic substituent in the functionalized <i>meso</i>-aryl units of the linker. Only the tetra-α-<i>meso</i>-arylextended tetracarboxylic calix[4]­pyrrole isomer <b>L1</b>, substituted in a single <i>meta</i>-position of their aryl rings, yields a two-dimensional MOF architecture assembled through complex Cu^II-carboxylate clusters (SBU). The clusters have higher nuclearity than the Cu^II₂-(O₂CR)₄ paddle wheels produced as SBUs during the assembly of the <i>para</i>-substituted counterpart <b>L2</b>. Remarkably, the length of the dialkylformamide used as solvent (DMF or DEF) in the synthesis of the Cu^II-organic materials derived from <b>L2</b> played a key role in the structure of the final solid material. The packing of discrete metal-mediated capsular dimers of <b>L2</b> switched to that of one-dimensional linear coordination polymers when the solvent’s alkyl chains were increased by a methylene unit. Finally, ligand <b>L3</b>, which featured a longer alkyl spacer between the <i>para</i>-substituted calix­[4]­pyrrole core and the terminal carboxylic groups than <b>L2</b>, self-assembled, exclusively, into discrete capsular coordination dimers also mediated by Cu^II paddle wheel units