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Fang P.-P.,CNRS PASTEUR Laboratory | Jutand A.,CNRS PASTEUR Laboratory | Tian Z.-Q.,Xiamen University | Amatore C.,CNRS PASTEUR Laboratory
Angewandte Chemie - International Edition | Year: 2011

Away from the surface: Novel nanoparticles (NPs) consisting of 16 nm Au cores surrounded by Pd shells of various thicknesses catalyze Suzuki-Miyaura cross-coupling reactions in water at room temperature. NPs having shells of two to five Pd monolayers thick exhibit the highest catalytic activity. Catalysis was attributed to the leaching of Pd species from the NPs through the synergistic action of the carbonate base and the arylboronic acid. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sterpone F.,CNRS PASTEUR Laboratory | Sterpone F.,French National Center for Scientific Research | Stirnemann G.,CNRS PASTEUR Laboratory | Stirnemann G.,Columbia University | Laage D.,CNRS PASTEUR Laboratory
Journal of the American Chemical Society | Year: 2012

Hydration shell dynamics plays a critical role in protein folding and biochemical activity and has thus been actively studied through a broad range of techniques. While all observations concur with a slowdown of water dynamics relative to the bulk, the magnitude and molecular origin of this retardation remain unclear. Via numerical simulations and theoretical modeling, we establish a molecular description of protein hydration dynamics and identify the key protein features that govern it. Through detailed microscopic mapping of the water reorientation and hydrogen-bond (HB) dynamics around lysozyme, we first determine that 80% of the hydration layer waters experience a moderate slowdown factor of ∼2-3, while the slower residual population is distributed along a power-law tail, in quantitative agreement with recent NMR results. We then establish that the water reorientation mechanism at the protein interface is dominated by large angular jumps similar to the bulk situation. A theoretical extended jump model is shown to provide the first rigorous determination of the two key contributions to the observed slowdown: a topological excluded-volume factor resulting from the local protein geometry, which governs the dynamics of the fastest 80% of the waters, and a free energetic factor arising from the water-protein HB strength, which is especially important for the remaining waters in confined sites at the protein interface. These simple local factors are shown to provide a nearly quantitative description of the hydration shell dynamics. © 2012 American Chemical Society.

Ferrer Flegeau E.,CNRS PASTEUR Laboratory | Bruneau C.,CNRS Chemistry Institute of Rennes | Dixneuf P.H.,CNRS Chemistry Institute of Rennes | Jutand A.,CNRS PASTEUR Laboratory
Journal of the American Chemical Society | Year: 2011

Kinetic data for the C - H bond activation of 2-phenylpyridine by Ru II(carboxylate)2(p-cymene) I (acetate) and I′ (pivalate) are available for the first time. They reveal an irreversible autocatalytic process catalyzed by the coproduct HOAc or HOPiv (acetonitrile, 27 °C). The overall reaction is indeed accelerated by the carboxylic acid coproduct and water. It is retarded by a base, in agreement with an autocatalytic process induced by HOAc or HOPiv that favors the dissociation of one carboxylate ligand from I and I′ and consequently the ensuing complexation of 2-phenylpyridine (2-PhPy). The C - H bond activation initially delivers Ru(O2CR)(o-C6H4-Py)(p-cymene) A or A′, containing one carboxylate ligand (OAc or OPiv, respectively). The overall reaction is accelerated by added acetates. Consequently, C - H bond activation (faster for acetate I than for pivalate I′) proceeds via an intermolecular deprotonation of the C - H bond of the ligated 2-PhPy by the acetate or pivalate anion released from I or I′, respectively. The 18e complexes A and A′ easily dissociate, by displacement of the carboxylate by the solvent (also favored by the carboxylic acid), to give the same cationic complex B+ {[Ru(o-C6H4-Py)(p-cymene)(MeCN)] +}. Complex B+ is reactive toward oxidative addition of phenyl iodide, leading to the diphenylated 2-pyridylbenzene. © 2011 American Chemical Society.

Lefevre G.,CNRS PASTEUR Laboratory | Lefevre G.,University of British Columbia | Jutand A.,CNRS PASTEUR Laboratory
Chemistry - A European Journal | Year: 2014

The mechanism of the reactions of aryl/heteroaryl halides with aryl Grignard reagents catalyzed by [FeIII(acac)3] (acac=acetylacetonate) has been investigated. It is shown that in the presence of excess PhMgBr, [FeIII(acac)3] affords two reduced complexes: [PhFeII(acac)(thf)n] (n=1 or 2) (characterized by 1H NMR and cyclic voltammetry) and [PhFeI(acac)(thf)] - (characterized by cyclic voltammetry, 1H NMR, EPR and DFT). Whereas [PhFeII(acac)(thf)n] does not react with any of the investigated aryl or heteroaryl halides, the FeI complex [PhFeI(acac)(thf)]- reacts with ArX (Ar=Ph, 4-tolyl; X=I, Br) through an inner-sphere monoelectronic reduction (promoted by halogen bonding) to afford the corresponding arene ArH together with the Grignard homocoupling product PhPh. In contrast, [PhFeI(acac)(thf)] - reacts with a heteroaryl chloride (2-chloropyridine) to afford the cross-coupling product (2-phenylpyridine) through an oxidative addition/reductive elimination sequence. The mechanism of the reaction of [PhFeI(acac)(thf)]- with the aryl and heteroaryl halides has been explored on the basis of DFT calculations. Iron(I) does the job: The reduction of [FeIII(acac)3] by PhMgBr gives [PhFe I(acac)(thf)]-, which reacts with ArX (Ar=Ph, 4-tol; X=I, Br) through an inner-sphere monoelectronic reduction promoted by halogen bonding to afford ArH and PhPh (see scheme; acac=acetylacetonate). In contrast, [PhFeI(acac)(thf)]- reacts with 2-chloropyridine to give the cross-coupling product (2-phenylpyridine) through a classical oxidative addition/reductive elimination sequence. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Amatore C.,CNRS PASTEUR Laboratory | Jutand A.,CNRS PASTEUR Laboratory | Leduc G.,CNRS PASTEUR Laboratory
Angewandte Chemie - International Edition | Year: 2012

Fluoride ions play three roles in the Suzuki-Miyaura reaction. They favor the reaction by formation of trans-[ArPdF(PPh 3) 2], which reacts with Ar B(OH) 2 in an unprecedented rate-determining transmetalation, and by promoting the reductive elimination from the trans-[ArPdAr (PPh 3) 2] intermediate. Conversely, F - disfavors the reaction by formation of unreactive anionic Ar B(OH) n-3F n - (n=1-3), leading to two antagonistic effects of F - in the transmetalation. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Laage D.,CNRS PASTEUR Laboratory | Stirnemann G.,CNRS PASTEUR Laboratory | Sterpone F.,CNRS PASTEUR Laboratory | Hynes J.T.,CNRS PASTEUR Laboratory | Hynes J.T.,University of Colorado at Boulder
Accounts of Chemical Research | Year: 2012

Liquid water is remarkably labile in reorganizing its hydrogen-bond (HB) network through the breaking and forming of HBs. This rapid restructuring, which occurs on the picosecond time scale, is critical not only for many of the pure liquid's special features but also for a range of aqueous media phenomena, including chemical reactions and protein activity. An essential part of the HB network reorganization is water molecule reorientation, which has long been described as Debye rotational diffusion characterized by very small angular displacements. Recent theoretical work, however, has presented a starkly contrasting picture: a sudden, large-amplitude jump mechanism, in which the reorienting water molecule rapidly exchanges HB partners in what amounts to an activated chemical reaction. In this Account, we first briefly review the jump mechanism and then discuss how it is supported by a series of experiments. These studies range from indirect indications to direct characterization of the jumps through pioneering two-dimensional infrared spectroscopy (2D-IR), the power of which accords it a special focus here.The scenarios in which experimental signatures of the jump mechanism are sought increase in complexity throughout the Account, beginning with pure water. Here 2D-IR in combination with theory can give a glimpse of the jumps, but the tell-tale markers are not pronounced. A more fruitful arena is provided by aqueous ionic solutions. The difference between water-water and water-anion HB strengths provides the experimental handle of differing OH stretch frequencies; in favorable cases, the kinetic exchange of a water between these two sites can be monitored. Sole observation of this exchange, however, is insufficient to establish the jump mechanism. Fortunately, 2D-IR with polarized pulses has demonstrated that HB exchange is accompanied by significant angular displacement, with an estimated jump angle similar to theoretical estimates.The Janus-like character of amphiphilic solutes, with their hydrophobic and hydrophilic faces, presents a special challenge for theory and experiment. Here a consensus on the 2D-IR interpretation has not yet been achieved; this lack of accord impedes the understanding of, for example, biochemical solutes and interfaces. We argue that the influence of hydrophobic groups on water jumps is only modest and well accounted for by an excluded volume effect in the HB exchange process. Conversely, hydrophilic groups have an important influence when their HB strength with water differs significantly from that of the water-water HB. The power of 2D-IR is argued to be accompanied by subtleties that can lead to just the opposite and, in our view, erroneous conclusion. We close with a prediction that a hydrophobic surface offers an arena in which the dynamics of "dangling" water OHs, bereft of a HB, could provide a 2D-IR confirmation of water jumps. © 2011 American Chemical Society.

Fogarty A.C.,CNRS PASTEUR Laboratory | Duboue-Dijon E.,CNRS PASTEUR Laboratory | Sterpone F.,University of Paris Pantheon Sorbonne | Hynes J.T.,CNRS PASTEUR Laboratory | And 2 more authors.
Chemical Society Reviews | Year: 2013

The dynamics of water molecules within the hydration shell surrounding a biomolecule can have a crucial influence on its biochemical function. Characterizing their properties and the extent to which they differ from those of bulk water have thus been long-standing questions. Following a tutorial approach, we review the recent advances in this field and the different approaches which have probed the dynamical perturbation experienced by water in the vicinity of proteins or DNA. We discuss the molecular factors causing this perturbation, and describe how they change with temperature. We finally present more biologically relevant cases beyond the dilute aqueous situation. A special focus is on the jump model for water reorientation and hydrogen bond rearrangement. © 2013 The Royal Society of Chemistry.

Amatore C.,CNRS PASTEUR Laboratory | Le Duc G.,CNRS PASTEUR Laboratory | Jutand A.,CNRS PASTEUR Laboratory
Chemistry - A European Journal | Year: 2013

In Suzuki-Miyaura reactions, anionic bases F- and OH- (used as is or generated from CO3 2- in water) play multiple antagonistic roles. Two are positive: 1) formation of trans-[Pd(Ar)F(L)2] or trans-[Pd(Ar)- (L)2(OH)] (L=PPh3) that react with Ar′B(OH)2 in the rate-determining step (rds) transmetallation and 2) catalysis of the reductive elimination from intermediate trans-[Pd(Ar)(Ar′)(L)2]. Two roles are negative: 1) formation of unreactive arylborates (or fluoroborates) and 2) complexation of the OH group of [Pd(Ar)(L)2(OH)] by the countercation of the base (Na+, Cs+, K+). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fogarty A.C.,CNRS PASTEUR Laboratory | Laage D.,CNRS PASTEUR Laboratory
Journal of Physical Chemistry B | Year: 2014

Protein hydration shell dynamics play an important role in biochemical processes including protein folding, enzyme function, and molecular recognition. We present here a comparison of the reorientation dynamics of individual water molecules within the hydration shell of a series of globular proteins: acetylcholinesterase, subtilisin Carlsberg, lysozyme, and ubiquitin. Molecular dynamics simulations and analytical models are used to access site-resolved information on hydration shell dynamics and to elucidate the molecular origins of the dynamical perturbation of hydration shell water relative to bulk water. We show that all four proteins have very similar hydration shell dynamics, despite their wide range of sizes and functions, and differing secondary structures. We demonstrate that this arises from the similar local surface topology and surface chemical composition of the four proteins, and that such local factors alone are sufficient to rationalize the hydration shell dynamics. We propose that these conclusions can be generalized to a wide range of globular proteins. We also show that protein conformational fluctuations induce a dynamical heterogeneity within the hydration layer. We finally address the effect of confinement on hydration shell dynamics via a site-resolved analysis and connect our results to experiments via the calculation of two-dimensional infrared spectra. © 2014 American Chemical Society.

Amatore C.,CNRS PASTEUR Laboratory | Jutand A.,CNRS PASTEUR Laboratory | Le Duc G.,CNRS PASTEUR Laboratory
Chemistry - A European Journal | Year: 2012

The mechanism of the reaction of trans-ArPdBrL 2 (Ar=p-Z-C 6H 4, Z=CN, H; L=PPh 3) with Ar'B(OH) 2 (Ar'=p-Z'-C 6H 4, Z'=H, CN, MeO), which is a key step in the Suzuki-Miyaura process, has been established in N,N-dimethylformamide (DMF) with two bases, acetate (nBu 4NOAc) or carbonate (Cs 2CO 3) and compared with that of hydroxide (nBu 4NOH), reported in our previous work. As anionic bases are inevitably introduced with a countercation M + (e.g., M +OH -), the role of cations in the transmetalation/reductive elimination has been first investigated. Cations M + (Na +, Cs +, K +) are not innocent since they induce an unexpected decelerating effect in the transmetalation via their complexation to the OH ligand in the reactive ArPd(OH)L 2, partly inhibiting its transmetalation with Ar'B(OH) 2. A decreasing reactivity order is observed when M + is associated with OH -: nBu 4N +> K +> Cs +> Na +. Acetates lead to the formation of trans-ArPd(OAc)L 2, which does not undergo transmetalation with Ar'B(OH) 2. This explains why acetates are not used as bases in Suzuki-Miyaura reactions that involve Ar'B(OH) 2. Carbonates (Cs 2CO 3) give rise to slower reactions than those performed from nBu 4NOH at the same concentration, even if the reactions are accelerated in the presence of water due to the generation of OH -. The mechanism of the reaction with carbonates is then similar to that established for nBu 4NOH, involving ArPd(OH)L 2 in the transmetalation with Ar'B(OH) 2. Due to the low concentration of OH - generated from CO 3 2- in water, both transmetalation and reductive elimination result slower than those performed from nBu 4NOH at equal concentrations as Cs 2CO 3. Therefore, the overall reactivity is finely tuned by the concentration of the common base OH - and the ratio [OH -]/[Ar'B(OH) 2]. Hence, the anionic base (pure OH - or OH - generated from CO 3 2-) associated with its countercation (Na +, Cs +, K +) plays four antagonist kinetic roles: acceleration of the transmetalation by formation of the reactive ArPd(OH)L 2, acceleration of the reductive elimination, deceleration of the transmetalation by formation of unreactive Ar'B(OH) 3 - and by complexation of ArPd(OH)L 2 by M +. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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