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The characterization of wastes constituted by LED lamps at the end of their lives is currently a concern of researchers and environmental managers not only because of the large volume will be generated by such wastes, but also to identify appropriate strategies for their reuse as well as their recyclability. This research describes the different steps involved in the characterization of LED lamps at the end of their lives such as, testing the functionality of the whole lamps, as well as modules and the LED components of the non-functional lamps. The results revealed that about 30.8 % of the wasted LED lamps are still working and could be reused in the social and solidarity economy or remarketed if economically viable. On the other hand, functionality test of the non-functional lamps showed that 56.5 % of the LED modules and 75% of the LED chips are still functional. Our investigations revealed that, repairing the non-functional lamps or reusing their functional components is challenging and therefore, their recycling is highly recommended.

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Structuring pores into stable membrane and controlling their opening is extremely useful for applications that require nanopores as channels for material exchange and transportation. In this work, nanoporous vesicles with aggregation-induced emission (AIE) properties were developed from the amphiphilic polymer PEG550-TPE-Chol, in which the hydrophobic part is composed of a tetraphenylethene (TPE) group and a cholesterol moiety and the hydrophilic block is a poly(ethylene glycol) (PEG, Mn = 550 Da). Two stereoisomers, trans-PEG550-TPE-Chol and cis-PEG550-TPE-Chol, were successfully synthesized. These thermally stable stereoisomers showed distinct self-assembly behavior in water: trans-PEG550-TPE-Chol formed classical vesicles, while cis-PEG550-TPE-Chol self-assembled into cylindrical micelles. Interestingly, trans/cis mixtures of PEG550-TPE-Chol (trans/cis = 60/40), either naturally synthesized without isomers' separation during the synthesis or intentionally mixed using trans- and cis-isomers, constructed perforated vesicles with nanopores. Moreover, under the illumination of high intensity UV light (365 nm, 15 mW/cm2), the classical vesicles of trans-PEG550-TPE-Chol were perforated by its cis counterparts generated from the trans-cis photoisomerization, while the cylindrical micelles of cis-PEG550-TPE-Chol interweaved to form meshes and nanoporous membranes due to the trans-isomers produced by cis-trans photoisomerization. All of these assemblies in water emitted bright cyan fluorescence under UV light, while their constituent molecules were not fluorescent when solubilized in organic solvent. The AIE fluorescent normal vesicles and nanoporous vesicles may find potential applications in biotechnology as light-gated delivery vehicles and capsules with nanochannels for material exchange.

The understanding of endothelium–extracellular matrix interactions during the initiation of new blood vessels is of great medical importance; however, the mechanobiological principles governing endothelial protrusive behaviours in 3D microtopographies remain imperfectly understood. In blood capillaries submitted to angiogenic factors (such as vascular endothelial growth factor, VEGF), endothelial cells can transiently transdifferentiate in filopodia-rich cells, named tip cells, from which angiogenesis processes are locally initiated. This protrusive state based on filopodia dynamics contrasts with the lamellipodia-based endothelial cell migration on 2D substrates. Using two-photon polymerization, we generated 3D microstructures triggering endothelial phenotypes evocative of tip cell behaviour. Hexagonal lattices on pillars (“open”), but not “closed” hexagonal lattices, induced engagement from the endothelial monolayer with the generation of numerous filopodia. The development of image analysis tools for filopodia tracking allowed to probe the influence of the microtopography (pore size, regular vs. elongated structures, role of the pillars) on orientations, engagement and filopodia dynamics, and to identify MLCK (myosin light-chain kinase) as a key player for filopodia-based protrusive mode. Importantly, these events occurred independently of VEGF treatment, suggesting that the observed phenotype was induced through microtopography. These microstructures are proposed as a model research tool for understanding endothelial cell behaviour in 3D fibrillary networks.

Graphene oxide (GO) is a carbon material with wide chemistry, and its functionalization represents the main challenge to develop multi-functional materials for different applications. Besides to epoxide and carboxyl groups, the alkenes that arise during the graphite oxidation seem to provide an excellent approach for developing selective reactions. In specific, α,β-unsaturated acids can be functionalized by thiol-ene Michael addition (TEMA) using base catalysts. However, when base catalysts are used, the thiol-epoxide ring opening reaction (TEROR) has been considered as the predominant and unique reaction. Therefore, there is a need to understand the reactivity of the GO when TEMA and TEROR take place from a qualitative and quantitative point of view. Herein, we studied the functionalization of GO and reduced graphene oxide (RGO) with cysteamine (CA) using different base catalysts. XPS results revealed that despite the thermal reduction of GO, the functionalization was possible confirming the coupling reaction between the CA and α,β-unsaturated acids of RGO by TEMA. In addition, a quantitative analysis was conducted via fluorescent labelling corroborating that TEMA produced more CA molecules bonded to GO than TEROR.

Graphene oxide (GO) is an important platform that can be functionalized due notably to its wide variety of functional groups. The functionalization is a critical step leading the production of GO b...

Capsules with holes in the walls exist in natural systems like virus capsids, and in biomimetic systems like immune-stimulating complexes vaccines and liposomes of phospholipids/surfactants mixtures. Structuring pores into stable membrane and controlling their opening are extremely useful for applications that require nano-pores as channels for material exchange and transportation. Polymersomes, which are stable and robust vesicles made of amphiphilic block copolymer, are good candidates for drug carriers or micro/nanoreactors. Engineering structure-inherent and light-gated nano-porous polymersomes is especially appealing, but still unexplored. Here we present these polymersomes made from a polymer including a tetraphenylethene (TPE) in its center. TPE is an emblematic fluorogen with aggregation-induced emission, which possesses two stereoisomers sensitive to photoisomerization. Trans-isomer of the polymer forms classical vesicles, cis-isomer forms cylindrical micelles, while trans/cis mixtures construct perforated vesicles with nano-pores. Under UV light, the classical polymersomes of trans-isomer can be perforated by its cis-counterpart generated from the photoisomerization.

We developed a new transcutaneous method for breast cancer detection with dogs: 2 dogs were trained to sniff skin secretion samples on compresses that had been worn overnight by women on their breast, and to recognize a breast cancer sample among 4 samples. During the test, the dogs recognized 90.3% of skin secretion breast cancer samples. This proof-of-concept study opens new avenues for the development of a reliable cancer diagnostic tool integrating olfactory abilities of dogs.

Amino acids are important compounds for GO functionalization because they can improve GO properties for many applications ranging from biomedicine to depollution. However, amino acids can act as nucleophiles or as reducing agents for GO functionalization or reduction, respectively. Hence, we systematically studied the GO functionalization/reduction using glycine as a model amino acid under basic conditions at room temperature. Attenuated total reflectance–Fourier transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy, and Raman spectroscopy were used to characterize the modified GO with glycine. We found that low glycine concentrations produced an epoxide ring opening reaction, whereas an increase in glycine concentration led to GO reduction. The basic medium allowed to conserve the carboxylic acid groups, whereas the GO reduction mechanism was governed by the partial hydrolysis of epoxide groups and the subsequent reduction of carboxylic acids to carbonyls. This article opens up the opportunity to study and control the conditions in which different amino acids could be used for either GO functionalization or GO reduction.

Initial adhesion of bacterial cells to surfaces or host tissues is a key step in colonisation and biofilm formation processes, and is mediated by cell surface appendages. It was previously demonstrated that Escherichia coli K-12 possesses an arsenal of silenced chaperone-usher fimbriae that were functional when constitutively expressed. Among them, production of prevalent Yad fimbriae induces adhesion to abiotic surfaces. Functional characterisation of Yad fimbriae were undertook, and YadN was identified as the most abundant and potential major pilin, and YadC as the potential tip-protein of Yad fimbriae. It was showed that Yad production participates to binding of E. coli K-12 to human eukaryotic cells (Caco-2) and inhibits macrophage phagocytosis, but also enhances E. coli K-12 binding to xylose, a major component of the plant cell wall, through its tip-lectin YadC. Consistently, it was demonstrated that Yad production provides E. coli with a competitive advantage in colonising corn seed rhizospheres. The latter phenotype is correlated with induction of Yad expression at temperatures below 37°C, and under anaerobic conditions, through a complex regulatory network. Taken together, these results suggest that Yad fimbriae are versatile adhesins that beyond potential capacities to modulate host-pathogen interactions might contribute to E. coli environmental persistence.

Two cationic polymers containing vinyl and quaternary ammonium groups were successfully grafted on silicone surfaces containing Si H groups. The reaction was carried out by straightforward hydrosilylation reaction in water without using exogenous catalyst and without doping the surface with Si H groups. The Si H content was varied by changing the curing time or the ratio between silicone components. The surfaces obtained exhibited quaternary ammonium densities ranging from 1.8 y 10 14 to 2.8 y 10 15 charge/cm 2 and higher polarity and hydrophilicity in comparison with non grafted surfaces. Bactericidal effects of these surfaces against Escherichia coli and Staphylococcus epidermidis were evidenced. This study have evidenced also the fouling of the poly(quaternary ammonium) (PQA) surfaces by contact with plasmatic proteins probably limiting their use in some biomedical field (e.g. implantable medical devices).

International audience; Cells are able to develop various types of membrane protrusions that modulate their adhesive, migratory, or functional properties. However, their ability to form basal protrusions, particularly in the context of epithelial sheets, is not widely characterized. The authors built hexagonal lattices to probe systematically the microtopography-induced formation of epithelial cell protrusions. Lattices of hexagons of various sizes (from 1.5 to 19 μm) and 5–10 μm height were generated by two-photon photopolymerization in NOA61 or poly(ethylene glycol) diacrylate derivatives. The authors found that cells generated numerous, extensive, and deep basal protrusions for hexagons inferior to cell size (3–10 μm) while maintaining a continuous epithelial layer above structures. They characterized the kinetics of protrusion formation depending on scaffold geometry and size. The reported formation of extensive protrusions in 3D microtopography could be beneficial to develop new biomaterials with increased adhesive properties or to improve tissue engineering.

Resume Introduction L’odeur est une perception. Dans une majorite des situations, les odeurs nauseabondes des plaies peuvent etre traitees. Mais sur des lesions specifiques (comme sur les plaies tumorales evoluees), ce symptome reste parfois incontrolable, entrainant des mouvements naturels de repulsion. Le curcuma, connu en tant qu’epice, est evoque comme potentiellement efficace sur les odeurs des plaies. Objectif Evaluer les interets de l’application de curcuma sur les plaies malodorantes, en vue de developper un travail de recherche structure (recherche translationnelle et/ou recherche et developpement) si les resultats semblent encourageants. Materiel et methode Etude preliminaire avec utilisation des donnees recueillies lors d’un travail de these ; observation de l’efficacite clinique des applications locales de curcuma et realisation d’une premiere serie de tests d’absorption, d’adsorption et microbiologique. Resultats Cliniquement, une reduction complete ou partielle de l’intensite des odeurs a ete observee. Le curcuma semble etre legerement moins performant a capturer les composes volatils que le charbon, cependant l’analyse par chromatographie a mis en evidence une multitude de COVs (> 100) dont de nombreux aromes qui pourraient expliquer l’efficacite clinique. Le curcuma semble ne pas pouvoir etre considere comme un absorbant, meme s’il absorbe une quantite non negligeable de liquide. L’absence de zones d’inhibition autour des plots de curcuma apres ensemencement d’une gelose avec E. coli MG 1655 est en defaveur d’une activite antibacterienne significative. Cependant, des articles demontrant une efficacite a base d’extraits (alcool) de curcuma imposerait la realisation d’une nouvelle serie de tests. Conclusion La poursuite de ce travail preliminaire pourrait permettre d’ameliorer la qualite des soins des plaies malodorantes, l’acquisition de connaissances sur un domaine peu explore et l’eventuelle formulation d’un nouveau topique a base de curcuma.

Inorganic bases such as NaH, KOt-Bu, NaOH, or KOH are efficient catalysts to promote the transcarbamoylation reaction between urethanes and a variety of primary and secondary alcohols under mild conditions. They constitute an alternative to organometallic catalysis and can be applied to aliphatic or aromatic urethanes.

Lʼodeur est une perception qui peut apparaitre au decours de l'evolution dʼune plaie ou en l'absence de soins (dʼhygiene et/ou de plaies). Dans la plupart des situations, les odeurs nauseabondes des plaies peuvent etre traitees, mais ce symptome reste parfois incontrolable, pouvant aller jusquʼa lʼisolement ou la repudiation. Lʼobjectif de cette etude est de developper une solution topique a base de cannelle pour le traitement des plaies malodorantes.

We have investigated the most efficient way of preparing biocompatible gold nanorods (GNR) used as tool for cancer imaging and therapy. The surface of cetyltrimethylammonium bromide-stabilized gold nanorods (GNR-CTAB) was functionalized with various thio-polyethylene glycols of the general formula HS-PEG mX ( m = 356–10,000; X = −OMe, −NH 2 ). The influence of several parameters such as PEG chain length, reaction conditions and purification method on long-term stability, morphology and optical properties of the produced GNR-S-PEG mX was studied, demonstrating the existence of a threshold HS-PEG mX chain length (with molecular weight m ⩾ 2000) for efficient steric stabilization of GNR. Several purification techniques were compared: dialysis, centrifugation and a rarely used technique in this field, size exclusion chromatography. While a very weak efficiency of dialysis was evidenced, both centrifugation and size exclusion chromatography were found to provide pure GNRs, though the latter method yielded nanoparticles with a significantly higher stability. Finally, the long-term stability of the produced GNRs was investigated in various media: water, PBS buffer and serum.

This paper describes a systematic study of the thermodynamics of association of bovine carbonic anhydrase II (BCA) and para-substituted benzenesulfonamides with chains of oligoglycine, oligosarcosine, and oligoethylene glycol of lengths of one to five residues. For all three of these series of ligands, the enthalpy of binding became less favorable, and the entropy less unfavorable, as the chain length of the ligands increased. The dependence on chain length of the enthalpy was almost perfectly compensated by that of the entropy; this compensation resulted in dissociation constants that were independent of chain length for the three series of ligands. Changes in heat capacity were independent of chain length for the three series and revealed that the amount of molecular surface area buried upon protein-ligand complexation did not increase with increasing chain length. Taken together, these data refute a model in which the chains of the ligands interact hydrophobically with the surface of BCA. To explain the data, a model is proposed based on decreasing "tightness" of the protein-ligand interface as the chain length of the ligand increases. This decreasing tightness, as the chain length increases, is reflected in a less favorable enthalpy (due to fewer van der Waals contacts) and a less unfavorable entropy (due to greater mobility of the chain) of binding for ligands with long chains than for those with short chains. Thus, this study demonstrates a surprising example of enthalpy/entropy compensation in a well-defined system. Understanding this compensation is integral to the rational design of high-affinity ligands for proteins.

To further investigate the degree of structural homology between γ-peptides A and N,N′-linked oligoureas B, we prepared oligourea nonamer 2 containing Ala, Val, Leu, Phe, Tyr and Lys side chains. Oligomer 2 was synthesized on solid support from activated monomers, i.e., from enantiomerically pure succinimidyl {2-{[(9H-fluoren-9-ylmethoxy)carbonyl]amino}ethyl}carbamates 3a–f that are further substituted at C(2) of the ethyl moiety. These precursors were conveniently prepared from N-Fmoc-protected β3-amino acids with corresponding side chains. Detailed NMR studies (DQF-COSY, TOCSY, and ROESY) in (D5)pyridine revealed that 2 adopts a regular (P)-2.5 helical secondary structure very similar to that previously determined for oligourea heptamer 1 and closely related to the (P)-2.614 helix of γ-peptides. Temperature-dependent NMR further demonstrated the conformational homogeneity and remarkable stability of the structure of 2 in pyridine. The CD spectrum of 2 (0.2 mM) was recorded in MeOH with the aim to gain more information about the conformation of oligoureas. In contrast to 2.6-helical γ-peptides, which display only a weak or no Cotton effect, oligourea 2 exhibits an intense positive Cotton effect at ca. 203 nm ([Θ]=+373000 deg cm2 dmol−1) that decreases only slowly upon increasing the temperature.

International audience; The use of catheters and other implanted devices is constantly increasing in modern medicine. Although catheters improve patients' healthcare, the hydrophobic nature of their surface material promotes protein adsorption and cell adhesion. Catheters are therefore prone to complications, such as colonization by bacterial and fungal biofilms, associated infections, and thrombosis. Here we describe the in vivo efficacy of biologically inspired glycocalyxlike antiadhesive coatings to inhibit Staphylococcus aureus and Pseudomonas aeruginosa colonization on commercial totally implantable venous access ports (TIVAPs) in a clinically relevant rat model of biofilm infection. Although noncoated TIVAPs implanted in rats were heavily colonized by the 2 biofilm-forming pathogens with a high percentage of occlusion, coating TIVAPs reduced their initial adherence and subsequently led to 4-log reduction in biofilm formation and reduced occlusion. Our antiadhesive approach is a simple and generalizable strategy that could be used to minimize clinical complications associated with the use of implantable medical devices.

In contrast to the situation observed in the crystal state, the urea moiety in N-Boc-N'-carbamoyl-gem-diaminoalkyl derivatives (single-residue ureidopeptides) 1-4 exclusively assumes a cis-trans conformation in solution. When R(3) = H, the resulting structure can be further stabilized by an intramolecular hydrogen bond that closes an eight-membered pseudocycle. The root-mean-square deviation calculated for heavy atoms between a peptide gamma-turn and the folded conformation that we propose to call urea turn is 0.60 A. [structure: see text]

Among the different technologies currently tested for the development of novel vaccines, synthetic peptides represent a promising option, since they are chemically pure and induce immune responses of predetermined specificity. Furthermore, they can be replaced with pseudopeptides or peptide mimetics that contain changes in the amide bond, resulting in more stable and immunogenic molecules. Administration of peptide vaccines via non-invasive routes, such as the nose or the bare skin, allows the efficient uptake of antigen by antigen-presenting cells, which are abundant in the associated lymphoid tissues, ensuring the induction of effective systemic and mucosal immune responses. Using non-invasive routes could be advantageous for vaccination programs in third-world countries, since vaccine administration is simple, painless and economical. In this review, we discuss and present some preliminary data on the advantages of synthetic peptides and peptidomimetics as candidate vaccines, and their potential for administration via the skin and the nose.

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The synthesis of Boc- or Fmoc-monoprotected propylenediamine derivatives is reported starting from N-protected α-amino acids. The introduction of these building blocks on solid support via the formation of a urea moiety leads to a new pseudopeptide family (CαCH2CH2Nα(R)CONHCα). Two carbonylating reagents, i.e N,N′-carbonyldiimidazole and triphosgene, as well as different coupling procedures, have been tested to optimize the Boc and Fmoc solid-phase synthesis of a model peptide incorporating this isosteric replacement.

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A new strategy to improve silicon-based endodontic treatment tightness by dentine hydrophobization is presented in this work: root dentine was silanized to obtain a hydrophobic dentine-sealer interface that limits fluid penetration. This strategy was based on the grafting of aliphatic carbon chains on the dentine through a silanization with the silane end groups [octadecyltrichlorosilane (OTS) and octadecyltriethoxysilane]. Dentine surface was previously pretreated, applying ethylenediaminetetraacetic acid and sodium hypochlorite, to expose hydroxyl groups of collagen for the silane grafting. Collagen fibers exposure after pretreatment was visible with scanning electron microscopy, and Fourier transform infrared (FTIR) spectroscopy showed their correct exposition for the silanization (amide I and II, with 1630, 1580, and 1538 cm⁻¹ peaks corresponding to the vibration of C=O and C--N bonds). The grafting of aliphatic carbon chains was confirmed by FTIR (peaks at 2952 and 2923 cm⁻¹ corresponding to the stretching of C--H bonds) and by the increasing of the water contact angle. The most efficient hydrophobization was obtained with OTS in ethyl acetate, with a water contact angle turning from 51° to 109°. Gas and liquid permeability tests showed an increased seal tightness after silanization: the mean gas and water flows dropped from 2.02 × 10⁻⁸ to 1.62 × 10⁻⁸ mol s⁻¹ and from 10.8 × 10⁻³ to 5.4 × 10⁻³ µL min⁻¹, respectively. These results show clear evidences to turn hydrophilic dentine surface into a hydrophobic surface that may improve endodontic sealing.

This work describes an integrated approach for designing on demand Self-Assembled Monolayers (SAMs) on silicon oxides and particularly glass substrates for cell biology applications. Starting from commercially available compounds, the strategy relies on thiol–ene reaction and provides high quality SAMs exhibiting adhesive and anti-adhesive patterns.

Objective This study evaluated the hydrophobicity of dentin surfaces that were modified through chemical silanization with octadecyltrichlorosilane (OTS). Material and Methods An in vitro experimental study was performed using 40 human permanent incisors that were divided into the following two groups: non-silanized and silanized. The specimens were pretreated and chemically modified with OTS. After the chemical modification, the dentin hydrophobicity was examined using a water contact angle measurement (WCA). The effectiveness of the modification of hydrophobicity was verified by the fluid permeability test (FPT). Results and Conclusions Statistically significant differences were found in the values of WCA and FPT between the two groups. After silanization, the hydrophobic intraradicular dentin surface exhibited in vitro properties that limit fluid penetration into the sealed root canal. This chemical treatment is a new approach for improving the sealing of the root canal system.

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A new, simple method to obtain ultrathin polycationic monolayers on hydroxylated surfaces is described which uses a bifunctional copolymer comprising a reactive part (trimethoxysilane) and positive charges (quaternary ammonium salts) to confer antimicrobial properties.

This paper proposes a method for sensing affinity interactions by triggering disruption of self-assembly of ion channel-forming peptides in planar lipid bilayers. It shows that the binding of a derivative of alamethicin carrying a covalently attached sulfonamide ligand to carbonic anhydrase II (CA II) resulted in the inhibition of ion channel conductance through the bilayer. We propose that the binding of the bulky CA II protein (MW approximately 30 kD) to the ion channel-forming peptides (MW approximately 2.5 kD) either reduced the tendency of these peptides to self-assemble into a pore or extracted them from the bilayer altogether. In both outcomes, the interactions between the protein and the ligand lead to a disruption of self-assembled pores. Addition of a competitive inhibitor, 4-carboxybenzenesulfonamide, to the solution released CA II from the alamethicin-sulfonamide conjugate and restored the current flow across the bilayer by allowing reassembly of the ion channels in the bilayer. Time-averaged recordings of the current over discrete time intervals made it possible to quantify this monovalent ligand binding interaction. This method gave a dissociation constant of approximately 2 microM for the binding of CA II to alamethicin-sulfonamide in the bilayer recording chamber: this value is consistent with a value obtained independently with CA II and a related sulfonamide derivative by isothermal titration calorimetry.

This paper reports dissociation constants and "effective molarities" (M(eff)) for the intramolecular binding of a ligand covalently attached to the surface of a protein by oligo(ethylene glycol) (EG(n)) linkers of different lengths (n = 0, 2, 5, 10, and 20) and compares these experimental values with theoretical estimates from polymer theory. As expected, the value of M(eff) is lowest when the linker is too short (n = 0) to allow the ligand to bind noncovalently at the active site of the protein without strain, is highest when the linker is the optimal length (n = 2) to allow such binding to occur, and decreases monotonically as the length increases past this optimal value (but only by a factor of approximately 8 from n = 2 to n = 20). These experimental results are not compatible with a model in which the single bonds of the linker are completely restricted when the ligand has bound noncovalently to the active site of the protein, but they are quantitatively compatible with a model that treats the linker as a random-coil polymer. Calorimetry revealed that enthalpic interactions between the linker and the protein are not important in determining the thermodynamics of the system. Taken together, these results suggest that the manifestation of the linker in the thermodynamics of binding is exclusively entropic. The values of M(eff) are, theoretically, intrinsic properties of the EG(n) linkers and can be used to predict the avidities of multivalent ligands with these linkers for multivalent proteins. The weak dependence of M(eff) on linker length suggests that multivalent ligands containing flexible linkers that are longer than the spacing between the binding sites of a multivalent protein will be effective in binding, and that the use of flexible linkers with lengths somewhat greater than the optimal distance between binding sites is a justifiable strategy for the design of multivalent ligands.

The preparation of succinimidyl (1-{[(alkyloxy)carbonyl]amino}-1-X-methyl)carbamates (4) and succinimidyl [1-(acylamino)-1-X-methyl] carbamates (5) from a variety ofN-Boc-, -Z- or -Fmoc-protected α-amino acids and dipeptides as well as the carbamate structural characterization are described. We have previously shown that succinimidyl carbamates 5, derived from N-Boc dipeptides, can serve as direct precursors of 1,3,5-triazepan-2,6-diones, a novel class of conformationally constrained dipeptide mimetics. Herein, we have evaluated the use of these building blocks for the synthesis of ureido-peptides (in solution and on solid support), peptidyl hydantoins, oligoureas and some oligo(urea/amide) hybrids. Conformational investigations by NMR of ureidotripeptide 6i and pentamer 10, consisting of alternating amides and ureas, suggested that folded conformations (i.e. a urea turn) characterized by a cis,trans (E,Z) geometry of the urea linkage are populated in both [D5]pyridine and [D6]DMSO solutions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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International audience; N,N'-linked oligoureas with proteinogenic side chains are peptide backbone mimetics belonging to the gamma-peptide lineage. In pyridine, heptamer 4 adopts a stable helical fold reminiscent of the 2.6(14) helical structure proposed for gamma-peptide foldamers. In the present study, we have used a combination of CD and NMR spectroscopies to correlate far-UV chiroptical properties and conformational preferences of oligoureas as a function of chain length from tetramer to nonamer. Both the intensity of the CD spectra and NMR chemical shift differences between alphaCH2 diastereotopic protons experienced a marked increase for oligomers between four and seven residues. No major change in CD spectra occurred between seven and nine residues, thus suggesting that seven residues could be the minimum length required for stabilizing a dominant conformation. Unexpectedly, in-depth NMR conformational investigation of heptamer 4 in CD3OH revealed that the 2.5 helix probably coexists with partially (un)folded conformations and that Z-E urea isomerization occurs, to some degree, along the backbone. Removing unfavorable electrostatic interactions at the amino terminal end of 4 and adding one H-bond acceptor by acylation with alkyl isocyanate (4 --> 7) was found to reinforce the 2.5 helical population. The stability of the 2.5 helical fold in MeOH is further discussed in light of unrestrained molecular dynamics (MD) simulation. Taken together, these new data provide additional insight into the folding propensity of oligoureas in protic solvent and should be of practical value for the design of helical bioactive oligoureas.

This work describes a method for patterning a gold substrate with multiple, aligned self-assembled monolayers (SAMs) using light at different wavelengths. It describes the synthesis and characterization of an alkanethiolate SAM that is photosensitive to light at both 220 and 365 nm. A photomask acts as an area-selective filter for light at 220 and 365 nm, and a single set of exposures at these two wavelengths through one photomask, without steps of alignment between the exposures, can produce three aligned SAMs on one gold substrate. We demonstrate the versatility of this method of photopatterning by modifying individual aligned SAMs chemically to produce surfaces having different properties. We characterize the modified SAMs using immunolabeling, matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy, and surface plasmon resonance spectroscopy. We also describe the patterning of two aligned SAMs that resist the adsorption of proteins and a third region that does not resist the adsorption of proteins. The ability to produce multiple, aligned patterns of SAMs in a single step, without alignment of photomasks in separate steps, increases the versatility of SAMs for studying a range of physical phenomena.