Highly hydrophilic surfaces from polyglycidol grafts with dual antifouling and specific protein recognition properties

Homopolymer grafts from α-tert-butoxy-ω-vinylbenzyl-polyglycidol (PGL) were prepared on gold and stainless steel (SS) substrates modified by 4-benzoyl-phenyl (BP) moieties derived from the electroreduction of the parent salt 4-benzoyl benzene diazonium tetrafluoroborate. The grafted BP aryl groups efficiently served to surface-initiate photopolymerization (SIPP) of PGL. In similar conditions, SIPP of hydroxyethyl methacrylate (HEMA) permitted the production of PHEMA grafts as model surfaces. Water contact angles were found to be 66°, 15°, and 0° for SS-BP, SS-PHEMA, and SS-PPGL, respectively. The spontaneous spreading of water drops on SS-PPGL was invariably observed with 1.5 μL water drops. PPGL thus appears as a superhydrophilic polymer. Resistance to nonspecific adsorption of proteins of PPGL and PHEMA grafts on gold was evaluated by surface plasmon resonance (SPR) using antibovine serum albumin (anti-BSA). The results conclusively show that PPGL-grafts exhibit enhanced resistance to anti-BSA adsorption compared to the well-known hydrophilic PHEMA. PPGL grafts were further modified with BSA through the carbonyldiimidazole activation of the OH groups providing immunosensing surfaces. The so-prepared PPGL-grafted BSA hybrids specifically interacted with anti-BSA in PBS as compared to antimyoglobin. It is clear that the superhydrophilic character of PPGL grafts opens new avenues for biomedical applications where surfaces with dual functionality, namely, specific protein grafting together with resistance to biofouling, are required.     

Computational study of the effect of confinement within microporous structures on the activity and selectivity of metallocene catalysts for ethylene oligomerization

The effect of confinement within some zeolitic structures on the activity and selectivity of metallocene catalysts for the ethylene oligomerization has been investigated using grand canonical Monte Carlo simulations (GCMC). The following zeolite (host) frameworks displaying different pore sizes, have been studied as solid hosts: mazzite (MAZ), AIPO-8 (AET), UTD-1F (DON), faujasite (FAU), and VPI-5 (VFI). Intermediates and transition states involved in the ethylene trimerization reaction catalyzed by a Ti-based catalyst [(η(5)-C(5)H(4)CMe(2)C(6)H(5))TiCl(3)/MAO] have been used as sorbates (guests). We have demonstrated linear correlations with slope a(H,j) between the adsorption enthalpy and the molecular volume V(m) of the sorbates, each holding for a given microporous host below a host-specific threshold V(mmax,j). Beyond this maximal molecular volume, the adsorption vanishes due to steric exclusion. a(H,j) increases, and V(mmax,j) decreases with decreasing host pore size, in line with the confinement concept. We moreover showed that, in the limit of vanishing loading (Henry regime), the enthalpies and entropies of adsorption in a given host are linearly correlated. We have defined a host-specific confinement compensation temperature a(j), which refers to a temperature where the stabilizing adsorption enthalpic interactions are canceled out against the loss in entropy. However, calculated a(j) are much larger than the operating temperatures. With a setup microkinetic model, we predict that the activity and selectivity of the confined Ti-catalyst in ethylene oligomerization can be significantly altered with respect to homogeneous phase conditions, since the adsorption free energies of transition states and intermediates also become functions of a(H,j) and V(m). We have applied this theory to predict the optimum host pore size to get maximum α-octene production, instead of α-hexene, which is primarily produced in the homogeneous phase. We also predict a significantly increased activity for confined catalysts.     

Nonribosomal peptide synthesis in animals: the cyclodipeptide synthase of Nematostella

Cyclodipeptide synthases (CDPSs) are small enzymes structurally related to class-I aminoacyl-tRNA synthetases (aaRSs). They divert aminoacylated tRNAs from their canonical role in ribosomal protein synthesis, for cyclodipeptide formation. All the CDPSs experimentally characterized to date are?bacterial. We show here that a predicted CDPS from the sea anemone Nematostella vectensis is an active CDPS catalyzing the formation of various cyclodipeptides, preferentially containing tryptophan. Our findings demonstrate that eukaryotes encode active CDPSs and suggest that all CDPSs have?a similar aminoacyl-tRNA synthetase-like architecture and ping-pong mechanism. They also raise questions about the biological roles of the cyclodipeptides produced in bacteria and eukaryotes.     

Comparative properties of Amazonian oils obtained by different extraction methods

Pequi (Caryocar brasiliense Camb.), baba?u (Orbignya phalerata Mart.), buriti (Mauritia flexuosa), and passion fruit (Passiflora edulis) oils were studied to determine their antibacterial, antioxidant and cytotoxic activities, as well as their total phenol and carotenoid contents. The fatty acid contents were determined by GC-MS. The three types of passion fruit oils studied were refined, cold pressed or extracted from seeds in a Soxhlet apparatus. The oils thus obtained showed differences in antioxidant activity and carotenoid content, but were similar in regard to total phenols. Buriti and pequi had the highest carotenoid contents, while refined and cold pressed passion fruit oil displayed the highest antioxidant activity. Pequi oil was the only oil to display antibacterial and cytotoxic activity.     

On confined McKean Langevin processes satisfying the mean no-permeability boundary condition

We construct a confined Langevin type process aimed to satisfy a mean no-permeability condition at the boundary. This Langevin process lies in the class of conditional McKean Lagrangian stochastic models studied by Bossy, Jabir and Talay (2010) [5]. The confined process considered here is a first construction of solutions to the class of Lagrangian stochastic equations with boundary condition issued by the so-called PDF methods for Computational Fluid Dynamics. We prove the well-posedness of the confined system when the state space of the Langevin process is a half-space.     

Counting permutations with no long monotone subsequence via generating trees and the kernel method

We recover Gessel’s determinantal formula for the generating function of permutations with no ascending subsequence of length m+1. The starting point of our proof is the recursive construction of these permutations by insertion of the largest entry. This construction is of course extremely simple. The cost of this simplicity is that we need to take into account in the enumeration m−1 additional parameters—namely, the positions of the leftmost increasing subsequences of length i, for i=2,…,m. This yields for the generating function a functional equation with m−1 “catalytic” variables, and the heart of the paper is the solution of this equation.     

Ruthenium nanoparticles in ionic liquids: structural and stability effects of polar solutes

Ionic liquids are a stabilizing medium for the in situ synthesis of ruthenium nanoparticles. Herein we show that the addition of molecular polar solutes to the ionic liquid, even in low concentrations, eliminates the role of the ionic liquid 3D structure in controlling the size of ruthenium nanoparticles, and can induce their aggregation. We have performed the synthesis of ruthenium nanoparticles by decomposition of [Ru(COD)(COT)] in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(1)C(4)Im][NTf(2)], under H(2) in the presence of varying amounts of water or 1-octylamine. For water added during the synthesis of metallic nanoparticles, a decrease of the solubility in the ionic liquid was observed, showed by nanoparticles located at the interface between aqueous and ionic phases. When 1-octylamine is present during the synthesis, stable nanoparticles of a constant size are obtained. When 1-octylamine is added after the synthesis, aggregation of the ruthenium nanoparticles is observed. In order to explain these phenomena, we have explored the molecular interactions between the different species using (13)C-NMR and DOSY (Diffusional Order Spectroscopy) experiments, mixing calorimetry, surface tension measurements and molecular simulations. We conclude that the behaviour of the ruthenium nanoparticles in [C(1)C(4)Im][NTf(2)] in the presence of 1-octylamine depends on the interaction between the ligand and the nanoparticles in terms of the energetics but also of the structural arrangement of the amine at the nanoparticle's surface.     

A novel ruthenium(II) complex for two-photon absorption-based optical power limiting in the near-IR range

In this article, the synthesis of a novel high-conjugated ligand and its corresponding Ru(II) complex PTFTF:Ru is reported, along with the linear and nonlinear optical characterizations. Two-photon absorption based optical power limiting properties (OPL), especially in the near infrared, are described and compared to those of the analogous complexes previously published. Combined with a preliminary theoretical approach, this allows us to highlight several key parameters for OPL optimization in such molecular systems and more particularly the spectral overlap between TPA and excited-state absorption.