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The hysteretic spin transition of a 130 nm-thick film becomes quantitative by annealing the co-crystallized metastable phase.

PB1-F2 is a small accessory protein encoded by an alternative open reading frame in PB1 segments of most influenza A virus. PB1-F2 is involved in virulence by inducing mitochondria-mediated immune cells apoptosis, increasing inflammation, and enhancing predisposition to secondary bacterial infections. Using biophysical approaches we characterized membrane disruptive activity of the full-length PB1-F2 (90 amino acids), its N-terminal domain (52 amino acids), expressed by currently circulating H1N1 viruses, and its C-terminal domain (38 amino acids). Both full-length and N-terminal domain of PB1-F2 are soluble at pH values <6, whereas the C-terminal fragment was found soluble only at pH < 3. All three peptides are intrinsically disordered. At pH > 7, the C-terminal part of PB1-F2 spontaneously switches to amyloid oligomers, whereas full-length and the N-terminal domain of PB1-F2 aggregate to amorphous structures. When incubated with anionic liposomes at pH 5, full-length and the C-terminal part of PB1-F2 assemble into amyloid structures and disrupt membrane at nanomolar concentrations. PB1-F2 and its C-terminal exhibit no significant antimicrobial activity. When added in the culture medium of mammalian cells, PB1-F2 amorphous aggregates show no cytotoxicity, whereas PB1-F2 pre-assembled into amyloid oligomers or fragmented nanoscaled fibrils was highly cytotoxic. Furthermore, the formation of PB1-F2 amyloid oligomers in infected cells was directly reflected by membrane disruption and cell death as observed in U937 and A549 cells. Altogether our results demonstrate that membrane-lytic activity of PB1-F2 is closely linked to supramolecular organization of the protein.

A POM to remember: Hexanuclear Fe(III) polyoxometalate (POM) single-molecule magnets (see structure) can be noncovalently assembled on the surface of single-wall carbon nanotubes. Complementary characterization techniques (see TEM image and magnetic hysteresis loops) demonstrate the integrity and bistability of the individual molecules, which could be used to construct single-molecule memory devices.

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5402www.MaterialsViews.com wileyonlinelibrary.com their post-modifi cation. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] We have reported an alternative surfactant-free synthesis that led, by adjusting the physico-chemical para meters, to the formation of stable colloidal aqueous solutions of nanocrystals with a narrow size distribution. [ 25,26 ] This stability originates from the negatively charged surface and has been exploited to set a versatile simple synthetic route for core-multishell heterostructured nanoparticles. [ 17 ] The method is based on a seed-mediated growth in solution of a shell on the as-obtained colloids either using the same PBA coordination network or another one. [ 17,[25][26][27][28][29] It was quite remarkable to observe that the size distribution of the resulting objects was of the order of 10%. Then, knowing that the cell parameter of the PBA networks is about 1 nm, which corresponds to two atomic layers ( Figure 1 ), such a size distribution corresponds to a control during the growth in solution over one monolayer. [ 17 ] The control of the monodispersity and the absence of stabilizing agents in these anionic objects allowed their organization in thin fi lms, [ 30,31 ] their use for surface nanopatterning, [ 32 ] and is essential for the analysis of their magnetic behaviour (see below).In a fi rst communication, [ 27 ] we have reported a series of cubic-like coordination nanoparticles of the ferromagnetic network CsNi II Cr III (CN) 6 ( T C (bulk) = 90 K) with sizes ranging from 6 to 30 nm and a narrow distribution (10-20%), using the seedmediated growth process. The study of the magnetic properties of these particles dispersed in a polymer (polyvinylpyrrolidone, PVP, for instance) allowed us determining experimentally the single domain limit size that was found to be around 15-16 nm. Below this size, as expected, a uniform reversal of the magnetization was observed. These results were in line with a Néel-Brown thermal activated magnetization reversal process with a relaxation governed by an anisotropy energy proportional to the volume of the particles, with no detectable surface anisotropy effect. [33][34][35] However, upon decreasing their size surface effects may become dominant and contribute greatly to the magnetic anisotropy of nanoparticles. [ 36,37 ] As evidenced in thin fi lms and nanoparticles, surface anisotropy constant is found higher by many orders of magnitude than that of the bulk. [ 1,38,39 ] Specifi cally in PBA nanoparticles, the role of surface anisotropy cannot be neglected because the coordination sphere of the divalent metal ions (Ni II ions here) present on the surface can be different from those belonging to the

International audienceSTM Observation of Open- and Closed-Ring Forms of Functionalized Diarylethene Molecules Self-Assembled on a Au(111) Surface Abstract HTMLFull Text HTML PDFHi-Res PDF[3988 KB] PDFPDF w/ Links[782 KB] Supporting Info Figures Your current credentials do not allow retrieval of the full text. Purchase the full-text Cart PDF/HTML, figures/images, references and tables, (where available) PDF Sergii V. Snegir†‡||, Alexandr A. Marchenko§, Pei Yu, Francois Maurel#, Oleksiy L. Kapitanchuk, Sandra Mazerat, Marc Lepeltier, Anne Léaustic, and Emmanuelle Lacaze*†|| Institut des NanoSciences de Paris (INSP), CNRS, 4 place Jussieu, 75251 Paris, France Institut des NanoSciences de Paris (INSP), UPMC Université Paris 6, 4 place Jussieu, 75251 Paris, France ‡Chuiko Institute of Surface Chemistry, §Institute of Physics, and Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Kyiv, Ukraine Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182, Université Paris Sud 11, 91405 Orsay, France Univ Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR CNRS 7086, 15 rue J-A de Baïf, 75205 Paris Cedex 13, France J. Phys. Chem. Lett., 2011, 2 (19), pp 2433-2436 DOI: 10.1021/jz200875c Publication Date (Web): August 24, 2011 Copyright © 2011 American Chemical Society E-mail: Emmanuelle.lacaze@insp.jussieu.fr. CASSection: Surface Chemistry and Colloids Abstract Abstract Image Ordered self-assembled monolayers (SAMs) of thiolated diarylethene photochromic molecules have been built on a Au(111) surface and characterized by mean of scanning tunneling microscopy (STM) for the first time. It has been revealed that molecules deposited from UV-illuminated (closed-ring isomer) and initial solutions (open-ring isomer) both occupy 4 × 2√3 adsorption sites on Au(111) and present a conformation where conjugated parts are parallel to the surface, forming "umbrella-like" structure. On the basis of the distances measured from STM images with intramolecular resolution and on quantum chemical DFT calculations of electronic structure for single molecules, an identical model of molecular packing with a 4 × 4√3 unit cell is proposed for both isomers. The variation of internal orbitals between open- and closed-ring isomers leads to significant change of STM contrast, allowing direct identification of each diarylethene isomer using STM images

Photo-switchable 11 nm nanocrystals of the coordination network Cs{Co[Fe(CN)6]} were obtained using a template-free method. The nanocrystals were recovered from the colloidal solutions as solid materials surrounded by cetyltrimethylammonium (CTA) cations or embedded in the organic polymer polyvinylpyrrolidone (PVP). Complementary magnetic, spectroscopic and structural techniques, including EPR Spectroscopy, reveal a majority (≈70%) of the low spin and photoactive diamagnetic Co III Fe II pairs located in the core of the nanocrystals and a mixture of Co II Fe II and Co II Fe III species present mainly within the shell of the objects. While bulk compounds with similar vacancy concentration do not exhibit noticeable photoinduced charge transfer, the obersved photoactivity of the nanocrystals is ascribed to their nanometric size. The relaxation temperature of the photo-induced state shifts upwards by ≈ 55 K when PVP is replaced by CTA. This is ascribed to the larger rigidity of the dense CsCoFe_CTA material whose metastable state is lower than for CsCoFe_PVP leading to a larger relaxation energy barrier and, therefore, to higher relaxation temperature.