Human adipose glycerol flux is regulated by a pH gate in AQP10.

Obesity is a major threat to global health and metabolically associated with glycerol homeostasis. Here we demonstrate that in human adipocytes, the decreased pH observed during lipolysis (fat burning) correlates with increased glycerol release and stimulation of aquaglyceroporin AQP10. The crystal structure of human AQP10 determined at 2.

Purification and functional comparison of nine human Aquaporins produced in Saccharomyces cerevisiae for the purpose of biophysical characterization.

The sparse number of high-resolution human membrane protein structures severely restricts our comprehension of molecular physiology and ability to exploit rational drug design. In the search for a standardized, cheap and easily handled human membrane protein production platform, we thoroughly investigated the capacity of S. cerevisiae to deliver high yields of prime quality human AQPs, focusing on poorly characterized members including some previously shown to be difficult to isolate.

Biomimetic Strategy To Reversibly Trigger Functionality of Catalytic Nanocompartments by the Insertion of pH-Responsive Biovalves.

We describe an innovative strategy to generate catalytic compartments with triggered functionality at the nanoscale level by combining pH-reversible biovalves and enzyme-loaded synthetic compartments. The biovalve has been engineered by the attachment of stimuli-responsive peptides to a genetically modified channel porin, enabling a reversible change of the molecular flow through the pores of the porin in response to a pH change in the local environment. The biovalve functionality triggers the reaction inside the cavity of the enzyme-loaded compartments by switching the in situ activity of the enzymes on/off based on a reversible change of the permeability of the membrane, which blocks or allows the passage of substrates and products.

Investigation of Horseradish Peroxidase Kinetics in an "Organelle-Like" Environment.

In order to mimic cell organelles, artificial nanoreactors have been investigated based on polymeric vesicles with reconstituted channel proteins (outer membrane protein F) and coencapsulated enzymes horseradish peroxidase (HRP) along with a crowding agent (Ficoll or polyethylene glycol) inside the cavity. Importantly, the presence of macromolecules has a strong impact on the enzyme kinetics, but no influence on the integrity of vesicles up to certain concentrations. This particular design allows for the first time the determination of HRP kinetics inside nanoreactors with crowded milieu.

Charge Transfer Pathways in Three Isomers of Naphthalene-Bridged Organic Mixed Valence Compounds.

Naphthalene was substituted at different positions with two identical triarylamine moieties to result in species which are mixed-valence compounds in their one-electron oxidized forms. They were investigated by cyclic voltammetry, optical absorption, EPR spectroscopy, X-ray crystallography, and DFT calculations. When the two redox-active triarylamine moieties are connected to the 2- and 6-positions of the naphthalene bridge, their electronic communication is significantly stronger than when they are linked to the 1- and 5-positions, and this can be understood on the basis of a simple through-bond charge transfer pathway model.

Stimuli-Triggered Activity of Nanoreactors by Biomimetic Engineering Polymer Membranes.

The development of advanced stimuli-responsive systems for medicine, catalysis, or technology requires compartmentalized reaction spaces with triggered activity. Only very few stimuli-responsive systems preserve the compartment architecture, and none allows a triggered activity in situ. We present here a biomimetic strategy to molecular transmembrane transport by engineering synthetic membranes equipped with channel proteins so that they are stimuli-responsive.

Does Membrane Thickness Affect the Transport of Selective Ions Mediated by Ionophores in Synthetic Membranes?

Biomimetic polymer nanocompartments (polymersomes) with preserved architecture and ion-selective membrane permeability represent cutting-edge mimics of cellular compartmentalization. Here it is studied whether the membrane thickness affects the functionality of ionophores in respect to the transport of Ca ions in synthetic membranes of polymersomes, which are up to 2.6 times thicker than lipid membranes (5 nm).

Polymersomes with engineered ion selective permeability as stimuli-responsive nanocompartments with preserved architecture.

Following a biomimetic approach, we present here polymer vesicles (polymersomes) with ion selective permeability, achieved by inserting gramicidin (gA) biopores in their membrane. Encapsulation of pH-, Na(+)- and K(+)- sensitive dyes inside the polymersome cavity was used to assess the proper insertion and functionality of gA inside the synthetic membrane. A combination of light scattering, transmission electron microscopy, and fluorescence correlation spectroscopy was used to show that neither the size, nor the morphology of the polymersomes was affected by successful insertion of gA in the polymer membrane.

New concepts to fight oxidative stress: nanosized three-dimensional supramolecular antioxidant assemblies.

Introduction: Misregulation of reactive oxygen species and reactive nitrogen species by the body's antioxidant system results in oxidative stress, which is known to be associated with aging, and involved in various pathologies including cancer, neurodegenerative and cardiovascular diseases. A large variety of low-molecular-weight (LMW) antioxidant compounds and antioxidant enzymes have been proposed to alleviate oxidative stress, but their therapeutic efficacy is limited by their solubility, stability or bioavailability. In this respect, nanoscience-based systems are expected to provide more efficient mitigation of oxidative stress.

Filling polymersomes with polymers by peroxidase-catalyzed atom transfer radical polymerization.

Polymersomes that encapsulate a hydrophilic polymer are prepared by conducting biocatalytic atom transfer radical polymerization (ATRP) in these hollow nanostructures. To this end, ATRPase horseradish peroxidase (HRP) is encapsulated into vesicles self-assembled from poly(dimethylsiloxane)-block-poly(2-methyl-2-oxazoline) (PDMS-b-PMOXA) diblock copolymers. The vesicles are turned into nanoreactors by UV-induced permeabilization with a hydroxyalkyl phenone and used to polymerize poly(ethylene glycol) methyl ether acrylate (PEGA) by enzyme-catalyzed ATRP.

Charge delocalization in an organic mixed valent bithiophene is greater than in a structurally analogous biselenophene.

A series of selenophenes with redox-active amine end-capping groups was synthesized and investigated. A combination of cyclic voltammetry, optical absorption, EPR spectroscopy, and quantum-chemical calculations based on Kohn-Sham density functional theory was used to explore charge delocalization in the monocationic mixed-valence forms of these selenophenes, and the results were compared to those obtained from analogous studies of structurally identical thiophenes. The striking finding is that the comproportionation constant (Kc) for the experimentally investigated biselenophene is more than 2 orders of magnitude lower than for its bithiophene counterpart (in CH3CN with 0.

Poly(N-isopropylacrylamide-co-tris-nitrilotriacetic acid acrylamide) for a combined study of molecular recognition and spatial constraints in protein binding and interactions.

Many biological processes require precise regulation and synergy of proteins, and consequently involve molecular recognition and spatial constraints between biomolecules. Here, a library of poly(N-isopropylacrylamide-co-tris-nitrilotriacetic acid acrylamide) (PNTs) has been synthesized and complexed with Cu(2+) in order to serve as models for investigation of the combined effects of molecular recognition and spatial constraints in biomolecular interactions. The average distance between Cu(2+)-trisNTA binding sites in PNTs polymers was varied from 4.

Electronic coupling mediated by furan, thiophene, selenophene and tellurophene in a homologous series of organic mixed valence compounds.

Charge delocalization in the mixed-valent monocationic forms of phenothiazine-decorated chalcogenophenes is explored by cyclic voltammetry, optical absorption and EPR spectroscopy. Single units of furan, thiophene, selenophene and tellurophene are found to mediate electronic coupling between the phenothiazines attached to their 2- and 5-positions roughly equally well. Electronic communication seems to occur mostly through the butadiene-like backbone of the chalcogenophenes.

Cellular Trojan horse based polymer nanoreactors with light-sensitive activity.

Stimulus-sensitive systems at the nanoscale represent ideal candidates for improving therapeutic and diagnostic approaches by producing rapid responses to the presence of specific molecules or conditions either by changing properties or by acting "on demand". Here we introduce an optimized light-sensitive nanoreactor based on encapsulation of a photosensitizer inside polymer vesicles to serve as an efficient source of reactive oxygen species (ROS) "on demand". Two types of amphiphilic block copolymers, poly(2-methyloxazoline)-block-poly(dimethylsiloxane)-block-poly(2-methyloxazoline), PMOXA-PDMS-PMOXA, and poly(N-vinylpyrrolidone)-block-poly(dimethylsiloxane)-block-poly(N-vinylpyrrolidone), PNVP-PDMS-PNVP, were used to encapsulate Rose Bengal-bovine serum albumin (RB-BSA) inside the cavity of vesicles.

Poly(N-vinylpyrrolidone)-poly(dimethylsiloxane)-based polymersome nanoreactors for laccase-catalyzed biotransformations.

Laccases (Lac) are oxidizing enzymes with a broad range of applications, for example, in soil remediation, as bleaching agent in the textile industry, and for cosmetics. Protecting the enzyme against degradation and inhibition is of great importance for many of these applications. Polymer vesicles (polymersomes) from poly(N-vinylpyrrolidone)-block-poly(dimethylsiloxane)-block-poly(N-vinylpyrrolidone) (PNVP-b-PDMS-b-PNVP) triblock copolymers were prepared and investigated as intrinsically semipermeable nanoreactors for Lac.

Combining polymers with the functionality of proteins: new concepts for atom transfer radical polymerization, nanoreactors and damage self-reporting materials.

Proteins are macromolecules with a great diversity of functions. By combining these biomolecules with polymers, exciting opportunities for new concepts in polymer sciences arise. This highlight exemplifies the aforementioned with current research results of our group.

Hemoglobin and red blood cells catalyze atom transfer radical polymerization.

Hemoglobin (Hb) is a promiscuous protein that not only transports oxygen, but also catalyzes several biotransformations. A novel in vitro catalytic activity of Hb is described. Bovine Hb and human erythrocytes were found to display ATRPase activity, i.

Photoreaction of a hydroxyalkyphenone with the membrane of polymersomes: a versatile method to generate semipermeable nanoreactors.

Block copolymer vesicles can be turned into nanoreactors when a catalyst is encapsulated in these hollow nanostructures. However the membranes of these polymersomes are most often impermeable to small organic molecules, while applications as nanoreactor, as artificial organelles, or as drug-delivery devices require an exchange of substances between the outside and the inside of polymersomes. Here, a simple and versatile method is presented to render polymersomes semipermeable.

Guest inclusion in cucurbiturils studied by ESR and DFT: the case of nitroxide radicals and spin adducts of DMPO and MNP.

We present an ESR and DFT study of the interaction of cucurbiturils CB[6], CB[7], and CB[8] with di-tert-butyl nitroxide ((CH(3))(3)C)(2)NO (DTBN) and with spin adducts of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and 2-methyl-2-nitrosopropane (MNP). The primary goal was to understand the structural parameters that determine the inclusion mechanism in the CBs using DTBN, a nitroxide with great sensitivity to the local environment. In addition, we focused on the interactions with CBs of the spin adducts DMPO/OH and MNP/CH(2)COOH generated in aqueous CH(3)COOH.

Fragmentation of perfluorinated membranes used in fuel cells: detecting very early events by selective encapsulation of short-lived fragments in β-cyclodextrin.

The fragmentation of perfluorinated ionomeric membranes during fuel cell (FC) operation is studied in our laboratory by direct electron spin resonance (ESR) and by spin trapping ESR, and interpretation of the results is facilitated by the study of model compounds (MCs). The advantage of this approach is the ability to detect and identify "early events" in the fragmentation process, before the appearance of stable species that can be detected by NMR and other methods. We report a spin trapping ESR study of the fragmentation of Nafion, Aquivion, and 3M membranes in their water dispersions and of the corresponding model compounds in the presence of HO•, using 2-methyl-2-nitrosopropane (MNP) as a spin trap.

Using cyclodextrins to encapsulate oxygen-centered and carbon-centered radical adducts: the case of DMPO, PBN, and MNP spin traps.

We present electron spin resonance (ESR) experiments that describe the interaction of beta-cyclodextrin (beta-CD) with spin adducts of three spin traps: 5,5-dimethyl-1-pyrroline N-oxide (DMPO), N-tert-butyl-alpha-phenylnitrone (PBN), and 2-methyl-2-nitrosopropane (MNP). The focus was on spin adducts of oxygen-centered radicals trapped by DMPO and PBN and on carbon-centered radical adducts trapped by MNP. The radicals were generated by reaction with hydroxyl radicals and the spin adducts studied were DMPO/OH and PBN/OH, MNP/CH(2)COOH generated in CH(3)COOH, and MNP/CF(2)COOH in CF(2)HCOOH.