Sample records for artificial light-harvesting self-assemble

  1. Quantum-dot-induced self-assembly of cricoid protein for light harvesting.

    PubMed

    Miao, Lu; Han, Jishu; Zhang, Hao; Zhao, Linlu; Si, Chengye; Zhang, Xiyu; Hou, Chunxi; Luo, Quan; Xu, Jiayun; Liu, Junqiu

    2014-04-22

    Stable protein one (SP1) has been demonstrated as an appealing building block to design highly ordered architectures, despite the hybrid assembly with other nano-objects still being a challenge. Herein, we developed a strategy to construct high-ordered protein nanostructures by electrostatic self-assembly of cricoid protein nanorings and globular quantum dots (QDs). Using multielectrostatic interactions between 12mer protein nanoring SP1 and oppositely charged CdTe QDs, highly ordered nanowires with sandwich structure were achieved by hybridized self-assembly. QDs with different sizes (QD1, 3-4 nm; QD2, 5-6 nm; QD3, ?10 nm) would induce the self-assembly protein rings into various nanowires, subsequent bundles, and irregular networks in aqueous solution. Atomic force microscopy, transmission electron microscopy, and dynamic light scattering characterizations confirmed that the size of QDs and the structural topology of the nanoring play critical functions in the formation of the superstructures. Furthermore, an ordered arrangement of QDs provides an ideal scaffold for designing the light-harvesting antenna. Most importantly, when different sized QDs (e.g., QD1 and QD3) self-assembled with SP1, an extremely efficient Förster resonance energy transfer was observed on these protein nanowires. The self-assembled protein nanostructures were demonstrated as a promising scaffold for the development of an artificial light-harvesting system. PMID:24601558

  2. Optimal efficiency of self-assembling light-harvesting arrays.

    PubMed

    Kim, Ji-Hyun; Cao, Jianshu

    2010-12-16

    Using a classical master equation that describes energy transfer over a given lattice, we explore how energy transfer efficiency along with the photon capturing ability depends on network connectivity, on transfer rates, and on volume fractions-the numbers and relative ratio of fluorescence chromophore components, e.g., donor (D), acceptor (A), and bridge (B) chromophores. For a one-dimensional AD array, the exact analytical expression (derived in Appendix A) for efficiency shows a steep increase with a D-to-A transfer rate when a spontaneous decay is sufficiently slow. This result implies that the introduction of B chromophores can be a useful method for improving efficiency for a two-component AD system with inefficient D-to-A transfer and slow spontaneous decay. Analysis of this one-dimensional system can be extended to higher-dimensional systems with chromophores arranged in structures such as a helical or stacked-disk rod, which models the self-assembling monomers of the tobacco mosaic virus coat protein. For the stacked-disk rod, we observe the following: (1) With spacings between sites fixed, a staggered conformation is more efficient than an eclipsed conformation. (2) For a given ratio of A and D chromophores, the uniform distribution of acceptors that minimizes the mean first passage time to acceptors is a key point to designing the optimal network for a donor-acceptor system with a relatively small D-to-A transfer rate. (3) For a three-component ABD system with a large B-to-A transfer rate, a key design strategy is to increase the number of the pathways in accordance with the directional energy flow from D to B to A chromophores. These conclusions are consistent with the experimental findings reported by Francis, Fleming, and their co-workers and suggest that synthetic architectures of self-assembling supermolecules and the distributions of AD or ABD chromophore components can be optimized for efficient light-harvesting energy transfer. PMID:20964280

  3. A nanoscale bio-inspired light-harvesting system developed from self-assembled alkyl-functionalized metallochlorin nano-aggregates.

    PubMed

    Ocakoglu, Kasim; Joya, Khurram S; Harputlu, Ersan; Tarnowska, Anna; Gryko, Daniel T

    2014-08-21

    Self-assembled supramolecular organization of nano-structured biomimetic light-harvesting modules inside solid-state nano-templates can be exploited to develop excellent light-harvesting materials for artificial photosynthetic devices. We present here a hybrid light-harvesting system mimicking the chlorosomal structures of the natural photosynthetic system using synthetic zinc chlorin units (ZnChl-C6, ZnChl-C12 and ZnChl-C18) that are self-aggregated inside the anodic aluminum oxide (AAO) nano-channel membranes. AAO nano-templates were modified with a TiO2 matrix and functionalized with long hydrophobic chains to facilitate the formation of supramolecular Zn-chlorin aggregates. The transparent Zn-chlorin nano-aggregates inside the alkyl-TiO2 modified AAO nano-channels have a diameter of ?120 nm in a 60 ?m length channel. UV-Vis studies and fluorescence emission spectra further confirm the formation of the supramolecular ZnChl aggregates from monomer molecules inside the alkyl-functionalized nano-channels. Our results prove that the novel and unique method can be used to produce efficient and stable light-harvesting assemblies for effective solar energy capture through transparent and stable nano-channel ceramic materials modified with bio-mimetic molecular self-assembled nano-aggregates. PMID:24909123

  4. Highly Efficient Photon Upconversion in Self-Assembled Light-Harvesting Molecular Systems.

    PubMed

    Ogawa, Taku; Yanai, Nobuhiro; Monguzzi, Angelo; Kimizuka, Nobuo

    2015-01-01

    To meet the world's demands on the development of sunlight-powered renewable energy production, triplet-triplet annihilation-based photon upconversion (TTA-UC) has raised great expectations. However, an ideal highly efficient, low-power, and in-air TTA-UC has not been achieved. Here, we report a novel self-assembly approach to achieve this, which enabled highly efficient TTA-UC even in the presence of oxygen. A newly developed lipophilic 9,10-diphenylanthracene-based emitter molecule functionalized with multiple hydrogen-bonding moieties spontaneously coassembled with a triplet sensitizer in organic media, showing efficient triplet sensitization and subsequent triplet energy migration among the preorganized chromophores. This supramolecular light-harvesting system shows a high UC quantum yield of 30% optimized at low excitation power in deaerated conditions. Significantly, the UC emission largely remains even in an air-saturated solution, and this approach is facilely applicable to organogel and solid-film systems. PMID:26057321

  5. Highly Efficient Photon Upconversion in Self-Assembled Light-Harvesting Molecular Systems

    PubMed Central

    Ogawa, Taku; Yanai, Nobuhiro; Monguzzi, Angelo; Kimizuka, Nobuo

    2015-01-01

    To meet the world’s demands on the development of sunlight-powered renewable energy production, triplet–triplet annihilation-based photon upconversion (TTA–UC) has raised great expectations. However, an ideal highly efficient, low-power, and in-air TTA–UC has not been achieved. Here, we report a novel self-assembly approach to achieve this, which enabled highly efficient TTA–UC even in the presence of oxygen. A newly developed lipophilic 9,10-diphenylanthracene-based emitter molecule functionalized with multiple hydrogen-bonding moieties spontaneously coassembled with a triplet sensitizer in organic media, showing efficient triplet sensitization and subsequent triplet energy migration among the preorganized chromophores. This supramolecular light-harvesting system shows a high UC quantum yield of 30% optimized at low excitation power in deaerated conditions. Significantly, the UC emission largely remains even in an air-saturated solution, and this approach is facilely applicable to organogel and solid-film systems. PMID:26057321

  6. Self-assembled zinc chlorin rod antennae powered by peripheral light-harvesting chromophores.

    PubMed

    Röger, Cornelia; Miloslavina, Yuliya; Brunner, Doris; Holzwarth, Alfred R; Würthner, Frank

    2008-05-01

    The multichromophoric dyads 1, 2 and triad 3 have been synthesized by coupling of the appropriately functionalized chlorin derivative with naphthalene diimide dyes through esterification, and subsequent metalation of the chlorin center with zinc acetate. The self-assembly properties of naphthalene diimide (NDI)-zinc chlorin (ZnChl) dyads 1, 2 and triad 3 have been studied in nonpolar, aprotic solvents by UV-vis, CD, and steady-state emission spectroscopy, revealing formation of rod-like structures by noncovalent interactions of zinc chlorin units, while the appended naphthalene diimide dyes do not aggregate at the periphery of the rod antennae. In all these systems, photoexcitation of the enveloping naphthalene diimides at 540 and 620 nm, respectively, leads to highly efficient energy-transfer processes (FRET; phiET > or = 0.99) to the inner zinc chlorin backbone, as explored by time-resolved fluorescence spectroscopy on the picosecond time scale. The efficiencies of zinc chlorin rod aggregates for the harvesting of solar light are markedly increased from 26% for dyad 2 up to 63% for triad 3, compared to the LH capacity of the monochromophoric aggregates of model system ZnChl 6a. Thus, with the self-assembled zinc chlorin rod antenna based on triad 3, a highly efficient artificial LH system has been achieved. PMID:18393414

  7. Photochemical Bleaching of an Elaborate Artificial Light-Harvesting Antenna.

    PubMed

    Alamiry, Mohammed A H; Harriman, Anthony; Haefele, Alexandre; Ziessel, Raymond

    2015-06-22

    The front cover artwork is provided by the groups of Tony Harriman (Newcastle University) and Raymond Ziessel (ECPM-Strasbourg). The image shows the processes following illumination of an artificial light harvester that slowly fades under continuous exposure to white light. Read the full text of the article at 10.1002/cphc.201500150. PMID:26037252

  8. Self-assembly of artificial microtubules

    E-print Network

    Cheng, Shengfeng; Stevens, Mark J

    2012-01-01

    Understanding the complex self-assembly of biomacromolecules is a major outstanding question. Microtubules are one example of a biopolymer that possesses characteristics quite distinct from standard synthetic polymers that are derived from its hierarchical structure. In order to understand how to design and build artificial polymers that possess features similar to those of microtubules, we have initially studied the self-assembly of model monomers into a tubule geometry. Our model monomer has a wedge shape with lateral and vertical binding sites that are designed to form tubules. We used molecular dynamics simulations to study the assembly process for a range of binding site interaction strengths. In addition to determining the optimal regime for obtaining tubules, we have calculated a diagram of the structures that form over a wide range of interaction strengths. Unexpectedly, we find that the helical tubules form, even though the monomer geometry is designed for nonhelical tubules. We present the detailed ...

  9. Self-assembly of artificial microtubules

    E-print Network

    Shengfeng Cheng; Ankush Aggarwal; Mark J. Stevens

    2012-01-10

    Understanding the complex self-assembly of biomacromolecules is a major outstanding question. Microtubules are one example of a biopolymer that possesses characteristics quite distinct from standard synthetic polymers that are derived from its hierarchical structure. In order to understand how to design and build artificial polymers that possess features similar to those of microtubules, we have initially studied the self-assembly of model monomers into a tubule geometry. Our model monomer has a wedge shape with lateral and vertical binding sites that are designed to form tubules. We used molecular dynamics simulations to study the assembly process for a range of binding site interaction strengths. In addition to determining the optimal regime for obtaining tubules, we have calculated a diagram of the structures that form over a wide range of interaction strengths. Unexpectedly, we find that the helical tubules form, even though the monomer geometry is designed for nonhelical tubules. We present the detailed dynamics of the tubule self-assembly process and show that the interaction strengths must be in a limited range to allow rearrangement within clusters. We extended previous theoretical methods to treat our system and to calculate the boundaries between different structures in the diagram.

  10. Artificial light-harvesting arrays for solar energy conversion.

    PubMed

    Harriman, Anthony

    2015-07-01

    Solar fuel production, the process whereby an energy-rich substance is produced using electrons provided by water under exposure to sunlight, requires the cooperative accumulation of multiple numbers of photons. Identifying the optimum reagents is a difficult challenge, even without imposing the restriction that these same materials must function as both sensitiser and catalyst. The blockade caused by an inadequate supply of photons at the catalytic sites might be resolved by making use of an artificial light-harvesting array whose sole purpose is to funnel photons of appropriate frequency to the active catalyst, which can now be a dark reagent. Here we consider several types of artificial photon collectors built from fluorescent modules interconnected via electronic energy transfer. Emphasis is placed on the materials aspects and on establishing the basic operating principles. PMID:26086688

  11. Photocurrent generation in a light-harvesting system with multifunctional artificial nanochannels.

    PubMed

    Zhang, Qianqian; Liu, Zhaoyue; Zhai, Jin

    2015-07-16

    We develop an artificial light-harvesting system for photocurrent generation. Platinized TiO2 nanochannels are used as ultraviolet-light-harvesting antennae, which generate a transmembrane electrochemical gradient by asymmetric work function driven photochemical reactions. As a result, a potential difference is formed across the nanochannels, producing a photocurrent flowing through the external circuit. PMID:26139227

  12. Photochemical Bleaching of an Elaborate Artificial Light-Harvesting Antenna.

    PubMed

    Alamiry, Mohammed A H; Harriman, Anthony; Haefele, Alexandre; Ziessel, Raymond

    2015-06-22

    The target artificial light-harvesting antenna, comprising 21 discrete chromophores arranged in a logical order, undergoes photochemical bleaching when dispersed in a thin plastic film. The lowest-energy component, which has an absorption maximum at 660 nm, bleaches through first-order kinetics at a relatively fast rate. The other components bleach more slowly, in part, because their excited-state lifetimes are rendered relatively short by virtue of fast intramolecular electronic energy transfer to the terminal acceptor. Two of the dyes, these being close to the terminal acceptor but interconnected through a reversible energy-transfer step, bleach by way of an autocatalytic step. Loss of the terminal acceptor, thereby switching off the energy-transfer route, escalates the rate of bleaching of these ancillary dyes. The opposite terminal, formed by a series of eight pyrene-based chromophores, does not bleach to any significant degree. Confirmation of the various bleaching steps is obtained by examination of an antenna lacking the terminal acceptor, where the autocatalytic route does not exist and bleaching is very slow. PMID:25900879

  13. Donor-acceptor star-shaped conjugated macroelectrolytes: synthesis, light-harvesting properties, and self-assembly-induced förster resonance energy transfer.

    PubMed

    Zhao, Li; Liu, Cheng-Fang; Xu, Wei-Dong; Jiang, Yi; Lai, Wen-Yong; Huang, Wei

    2015-06-01

    A novel series of donor-acceptor star-shaped conjugated macroelectrolytes (CMEs), denoted as 4FTs, including anionic carboxylic acid sodium groups (4FNaT), neutral diethanolamine groups (4FNOHT), and cationic ammonium groups (4FNBrT), were designed, synthesized, and explored as an excellent platform to investigate the impact of various polar pendent groups on self-assembly behaviors. The resulting CMEs with donor-acceptor star-shaped architectures exhibited distinct light-harvesting properties. The interactions between 4FTs and TrNBr, a star-shaped monodisperse CME grafted with cationic quaternary ammonium side chains, were investigated in H2O and CH3OH using steady-state, time-resolved fluorescence, dynamic light scattering (DLS), and transmission electron microscopy (TEM). Highly favored energy transfer has been proven by the excellent spectral overlap between TrNBr fluorescence and 4FTs absorptions which can be tuned by adjusting the pendent polar groups and solvents. It is suggested that self-assembled structures are formed between TrNBr and 4FNaT, while there is no obvious change for TrNBr/4FNOHT and TrNBr/4FNBrT in both H2O and CH3OH at low concentrations (<10(-6) M). This result is confirmed by the change of the TrNBr and 4FTs fluorescence properties and the time-resolved fluorescence data. The overall results manifest that at low concentrations the self-assembly between TrNBr and 4FTs is dominated by the electrostatic interactions. This study suggests that the functionalization of pendent polar groups of star-shaped CMEs has proven to be effective to modulate the self-assembly behaviors in dilute solutions and thus provide a strategy to further manage the optoelectronic properties. PMID:25981514

  14. Out of the cleanroom, self-assembled magnetic artificial cilia.

    PubMed

    Wang, Ye; Gao, Yang; Wyss, Hans; Anderson, Patrick; den Toonder, Jaap

    2013-09-01

    Micro-sized hair-like structures, such as cilia, are abundant in nature and have various functionalities. Many efforts have been made to mimic the fluid pumping function of cilia, but most of the fabrication processes for these "artificial cilia" are tedious and expensive, hindering their practical application. In this paper a cost-effective in situ fabrication technique for artificial cilia is demonstrated. The cilia are constructed by self-assembly of micron sized magnetic beads and encapsulated with soft polymer coatings. Actuation of the cilia induces an effective fluid flow, and the cilia lengths and distribution can be adjusted by varying the magnetic bead concentration and fabrication parameters. PMID:23846423

  15. Vibronic origin of long-lived coherence in an artificial molecular light harvester.

    PubMed

    Lim, James; Pale?ek, David; Caycedo-Soler, Felipe; Lincoln, Craig N; Prior, Javier; von Berlepsch, Hans; Huelga, Susana F; Plenio, Martin B; Zigmantas, Donatas; Hauer, Jürgen

    2015-01-01

    Natural and artificial light-harvesting processes have recently gained new interest. Signatures of long-lasting coherence in spectroscopic signals of biological systems have been repeatedly observed, albeit their origin is a matter of ongoing debate, as it is unclear how the loss of coherence due to interaction with the noisy environments in such systems is averted. Here we report experimental and theoretical verification of coherent exciton-vibrational (vibronic) coupling as the origin of long-lasting coherence in an artificial light harvester, a molecular J-aggregate. In this macroscopically aligned tubular system, polarization-controlled 2D spectroscopy delivers an uncongested and specific optical response as an ideal foundation for an in-depth theoretical description. We derive analytical expressions that show under which general conditions vibronic coupling leads to prolonged excited-state coherence. PMID:26158602

  16. G-quartet-based nanostructure for mimicking light-harvesting antenna.

    PubMed

    Pu, Fang; Wu, Li; Ran, Xiang; Ren, Jinsong; Qu, Xiaogang

    2015-01-12

    Artificial light-harvesting systems have received great attention for use in photosynthetic and optoelectronic devices. Herein, a system involving G-quartet-based hierarchical nanofibers generated from the self-assembly of guanosine 5'-monophosphate (GMP) and a two-step Förster resonance energy transfer (FRET) is presented that mimics natural light-harvesting antenna. This solid-state property offers advantages for future device fabrication. The generation of photocurrent under visible light shows it has potential for use as a nanoscale photoelectric device. The work will be beneficial for the development of light-harvesting systems by the self-assembly of supramolecular nanostructures. PMID:25423890

  17. Charge transfer and quantum coherence in solar cells and artificial light harvesting system

    NASA Astrophysics Data System (ADS)

    Lienau, Christoph

    2014-03-01

    In artificial light harvesting systems the conversion of light into electrical or chemical energy happens on the femtosecond time scale, and is thought to involve the incoherent jump of an electron from the optical absorber to an electron acceptor. Here we investigate the primary dynamics of the photoinduced electronic charge transfer process in two prototypical structures: (i) a carotene-porphyrin-fullerene triad, a prototypical elementary component for an artificial light harvesting system and (ii) a polymer:fullerene blend as a model system for an organic solar cell. Our approach combines coherent femtosecond spectroscopy and first-principles quantum dynamics simulations. Our experimental and theoretical results provide strong evidence that the driving mechanism of the primary step within the current generation cycle is a quantum-correlated wavelike motion of electrons and nuclei on a timescale of few tens of femtoseconds. We furthermore highlight the fundamental role played by the flexible interface between the light-absorbing chromophore and the charge acceptor in triggering the coherent wavelike electron-hole splitting.

  18. Stepwise photoconversion of an artificial light-harvesting array built from extended BODIPY units.

    PubMed

    Harriman, Anthony; Stachelek, Patrycja; Sutter, Alexandra; Ziessel, Raymond

    2015-06-01

    A molecular dyad, comprising two disparate extended boron dipyrromethene (BODIPY) units, has been identified as a potential component of artificial light-harvesting arrays. Highly efficient, intramolecular electronic energy transfer takes place under illumination but there is some competition from light-induced electron transfer along the molecular axis. The primary energy acceptor has a somewhat shortened excited-state lifetime and reduced emission quantum yield due to charge transfer from a terminal amine residue, the latter being required for the molecular system to operate in organic solar cells. Under continuous illumination with simulated solar light, the dyad undergoes very slow decomposition. In a protic solvent, both BODIPY units degrade at the same rate via an autocatalytic process. The products, one of which is a protonated analogue of the donor, degrade further by independent routes. In aprotic solvents or thin plastic films, the acceptor BODIPY dye absorbing at lowest energy undergoes photochemical degradation as above but the donor is much more stable under these conditions. At each stage of degradation, the molecule retains the ability to sensitize an amorphous silicon solar cell and the overall turnover number with respect to absorbed photons exceeds 10 million. The optical properties of the target compound nicely complement those of the solar cell and sensitization helps to avoid Staebler-Wronski photo-degradation. PMID:25898915

  19. In Vitro Self-Assembly of the Light Harvesting Pigment-Protein LH2 Revealed by Ultrafast Spectroscopy and Electron Microscopy

    PubMed Central

    Schubert, Axel; Stenstam, Anna; Beenken, Wichard J. D.; Herek, Jennifer L.; Cogdell, Richard; Pullerits, Tõnu; Sundström, Villy

    2004-01-01

    Controlled ensemble formation of protein-surfactant systems provides a fundamental concept for the realization of nanoscale devices with self-organizing capability. In this context, spectroscopic monitoring of pigment-containing proteins yields detailed structural information. Here we have studied the association behavior of the bacterial light-harvesting protein LH2 from Rhodobacter spheroides in an n,n-dimethyldodecylamine-n-oxide/water environment. Time-resolved studies of the excitation annihilation yielded information about aggregate sizes and packing of the protein complexes therein. The results are compared to transmission electron microscopy images of instantaneously frozen samples. Our data indicate the manifestation of different phases, which are discussed with respect to the thermodynamic equilibrium in ternary protein-surfactant-water systems. Accordingly, by varying the concentration the formation of different types of aggregates can be controlled. Conditions for the appearance of isolated LH2 complexes are defined. PMID:15041674

  20. Linear birefringence magnitude of artificial self-assembled DNA crystals

    PubMed Central

    Lehmuskero, Anni; Hakulinen, Nina; Lajunen, Hanna; Zheng, Jianping; Sha, Ruojie; Bai, Benfeng; Huang, Lingling; Turunen, Jari; Vahimaa, Pasi; Seeman, Nadrian C.

    2012-01-01

    We determine the linear birefringence magnitude, i.e. the difference between refractive indexes along the extraordinary and ordinary axes, of artificial uniaxial DNA crystals assembled with the so-called DNA tile approach. Based on the ellipsometric measurements, the birefringence magnitude is between 0.001 and 0.0018 in the visible and near infrared range. Besides being of fundamental interest, the optical properties of DNA crystals are crucial in the design of novel photonic nanostuctures. PMID:24490121

  1. Design and self-assembly of simple coat proteins for artificial viruses

    NASA Astrophysics Data System (ADS)

    Hernandez-Garcia, Armando; Kraft, Daniela J.; Janssen, Anne F. J.; Bomans, Paul H. H.; Sommerdijk, Nico A. J. M.; Thies-Weesie, Dominique M. E.; Favretto, Marco E.; Brock, Roland; de Wolf, Frits A.; Werten, Marc W. T.; van der Schoot, Paul; Stuart, Martien Cohen; de Vries, Renko

    2014-09-01

    Viruses are among the simplest biological systems and are highly effective vehicles for the delivery of genetic material into susceptible host cells. Artificial viruses can be used as model systems for providing insights into natural viruses and can be considered a testing ground for developing artificial life. Moreover, they are used in biomedical and biotechnological applications, such as targeted delivery of nucleic acids for gene therapy and as scaffolds in material science. In a natural setting, survival of viruses requires that a significant fraction of the replicated genomes be completely protected by coat proteins. Complete protection of the genome is ensured by a highly cooperative supramolecular process between the coat proteins and the nucleic acids, which is based on reversible, weak and allosteric interactions only. However, incorporating this type of supramolecular cooperativity into artificial viruses remains challenging. Here, we report a rational design for a self-assembling minimal viral coat protein based on simple polypeptide domains. Our coat protein features precise control over the cooperativity of its self-assembly with single DNA molecules to finally form rod-shaped virus-like particles. We confirm the validity of our design principles by showing that the kinetics of self-assembly of our virus-like particles follows a previous model developed for tobacco mosaic virus. We show that our virus-like particles protect DNA against enzymatic degradation and transfect cells with considerable efficiency, making them promising delivery vehicles.

  2. Design and self-assembly of simple coat proteins for artificial viruses.

    PubMed

    Hernandez-Garcia, Armando; Kraft, Daniela J; Janssen, Anne F J; Bomans, Paul H H; Sommerdijk, Nico A J M; Thies-Weesie, Dominique M E; Favretto, Marco E; Brock, Roland; de Wolf, Frits A; Werten, Marc W T; van der Schoot, Paul; Stuart, Martien Cohen; de Vries, Renko

    2014-09-01

    Viruses are among the simplest biological systems and are highly effective vehicles for the delivery of genetic material into susceptible host cells. Artificial viruses can be used as model systems for providing insights into natural viruses and can be considered a testing ground for developing artificial life. Moreover, they are used in biomedical and biotechnological applications, such as targeted delivery of nucleic acids for gene therapy and as scaffolds in material science. In a natural setting, survival of viruses requires that a significant fraction of the replicated genomes be completely protected by coat proteins. Complete protection of the genome is ensured by a highly cooperative supramolecular process between the coat proteins and the nucleic acids, which is based on reversible, weak and allosteric interactions only. However, incorporating this type of supramolecular cooperativity into artificial viruses remains challenging. Here, we report a rational design for a self-assembling minimal viral coat protein based on simple polypeptide domains. Our coat protein features precise control over the cooperativity of its self-assembly with single DNA molecules to finally form rod-shaped virus-like particles. We confirm the validity of our design principles by showing that the kinetics of self-assembly of our virus-like particles follows a previous model developed for tobacco mosaic virus. We show that our virus-like particles protect DNA against enzymatic degradation and transfect cells with considerable efficiency, making them promising delivery vehicles. PMID:25150720

  3. Efficient excited energy transfer reaction in clay/porphyrin complex toward an artificial light-harvesting system.

    PubMed

    Ishida, Yohei; Shimada, Tetsuya; Masui, Dai; Tachibana, Hiroshi; Inoue, Haruo; Takagi, Shinsuke

    2011-09-14

    The quantitative excited energy transfer reaction between cationic porphyrins on an anionic clay surface was successfully achieved. The efficiency reached up to ca. 100% owing to the "Size-Matching Rule" as described in the text. It was revealed that the important factors for the efficient energy transfer reaction are (i) suppression of the self-quenching between adjacent dyes, and (ii) suppression of the segregated adsorption structure of two kinds of dyes on the clay surface. By examining many different kinds of porphyrins, we found that tetrakis(1-methylpyridinium-3-yl) porphyrin (m-TMPyP) and tetrakis(1-methylpyridinium-4-yl) porphyrin (p-TMPyP) are the suitable porphyrins to accomplish a quantitative energy transfer reaction. These findings indicate that the clay/porphyrin complexes are promising and prospective candidates to be used for construction of an efficient artificial light-harvesting system. PMID:21809841

  4. Vibronic coupling explains the ultrafast carotenoid-to-bacteriochlorophyll energy transfer in natural and artificial light harvesters.

    PubMed

    Perlík, Václav; Seibt, Joachim; Cranston, Laura J; Cogdell, Richard J; Lincoln, Craig N; Savolainen, Janne; Šanda, František; Man?al, Tomáš; Hauer, Jürgen

    2015-06-01

    The initial energy transfer steps in photosynthesis occur on ultrafast timescales. We analyze the carotenoid to bacteriochlorophyll energy transfer in LH2 Marichromatium purpuratum as well as in an artificial light-harvesting dyad system by using transient grating and two-dimensional electronic spectroscopy with 10 fs time resolution. We find that Förster-type models reproduce the experimentally observed 60 fs transfer times, but overestimate coupling constants, which lead to a disagreement with both linear absorption and electronic 2D-spectra. We show that a vibronic model, which treats carotenoid vibrations on both electronic ground and excited states as part of the system's Hamiltonian, reproduces all measured quantities. Importantly, the vibronic model presented here can explain the fast energy transfer rates with only moderate coupling constants, which are in agreement with structure based calculations. Counterintuitively, the vibrational levels on the carotenoid electronic ground state play the central role in the excited state population transfer to bacteriochlorophyll; resonance between the donor-acceptor energy gap and the vibrational ground state energies is the physical basis of the ultrafast energy transfer rates in these systems. PMID:26049454

  5. Vibronic coupling explains the ultrafast carotenoid-to-bacteriochlorophyll energy transfer in natural and artificial light harvesters

    NASA Astrophysics Data System (ADS)

    Perlík, Václav; Seibt, Joachim; Cranston, Laura J.; Cogdell, Richard J.; Lincoln, Craig N.; Savolainen, Janne; Šanda, František; Man?al, Tomáš; Hauer, Jürgen

    2015-06-01

    The initial energy transfer steps in photosynthesis occur on ultrafast timescales. We analyze the carotenoid to bacteriochlorophyll energy transfer in LH2 Marichromatium purpuratum as well as in an artificial light-harvesting dyad system by using transient grating and two-dimensional electronic spectroscopy with 10 fs time resolution. We find that Förster-type models reproduce the experimentally observed 60 fs transfer times, but overestimate coupling constants, which lead to a disagreement with both linear absorption and electronic 2D-spectra. We show that a vibronic model, which treats carotenoid vibrations on both electronic ground and excited states as part of the system's Hamiltonian, reproduces all measured quantities. Importantly, the vibronic model presented here can explain the fast energy transfer rates with only moderate coupling constants, which are in agreement with structure based calculations. Counterintuitively, the vibrational levels on the carotenoid electronic ground state play the central role in the excited state population transfer to bacteriochlorophyll; resonance between the donor-acceptor energy gap and the vibrational ground state energies is the physical basis of the ultrafast energy transfer rates in these systems.

  6. Light Harvesting Single Wall Carbon Nanotube Hybrids

    Microsoft Academic Search

    Benjamin Baker; Tae-Gon Cha; M. Dane Sauffer; Yujun Wu; Jong Hyun Choi

    2010-01-01

    Due to extraordinary electron accepting and conductivity properties, single wall carbon nanotubes (SWNT) are explored as molecular wires in light harvesting cells. Here SWNT are employed as acceptors of photo-excited charge\\/energy in self-assembling aqueous soluble nanohybrids. DNA oligonucleotides and functionalized pyrene moieties are used as surfactants to solubilize an ensemble of individually suspended SWNT. Water-soluble porphyrins, chlorophyll-like molecules with strong

  7. Question 9: Quantum Self-Assembly and Photoinduced Electron Tunneling in Photosynthetic Systems of Artificial Minimal Living Cells

    NASA Astrophysics Data System (ADS)

    Tamulis, Arvydas; Tamulis, Vykintas

    2007-10-01

    Natural and artificial living cells and their substructures are self-assembling, due to electron correlation interactions among biological and water molecules, which lead to attractive dispersion forces and hydrogen bonds. Dispersion forces are weak intermolecular forces that arise from the attractive force between quantum multipoles. A hydrogen bond is a special type of quantum attractive interaction that exists between an electronegative atom and a hydrogen atom bonded to another electronegative atom; and this hydrogen atom exist in two quantum states. The best method to simulate these dispersion forces and hydrogen bonds is to perform quantum mechanical non-local density functional potential calculations of artificial minimal living cells consisting of around 1,000 atoms. The cell systems studied are based on peptide nucleic acid and are 3.0-4.2 nm in diameter. The electron tunneling and associated light absorption of the most intense transitions, as calculated by the time dependent density functional theory method, differs from spectroscopic experiments by only 0.2-0.3 nm, which is within the value of experiment errors. This agreement implies that the quantum mechanically self-assembled structures of artificial minimal living cells very closely approximate realistic ones.

  8. Self-assembled chromophores within mesoporous nanocrystalline TiO2: towards biomimetic solar cells.

    PubMed

    Marek, Peter L; Sieger, Hermann; Scherer, Torsten; Hahn, Horst; Balaban, Teodor Silviu

    2009-06-01

    Artificial light-harvesting antennas consisting of self-assembled chromophores that mimic the natural pigments of photosynthetic bacteria have been inserted into voids induced in porous titania (TiO2, anatase) in order to investigate their suitability for hybrid solar cells. Mesoporous nanocrystalline TiO2 with additional uniform macropores was treated with precursor solutions of the pigment which was then induced to self-assemble within the voids. The chromophores were tailored to combine the self-assembly characteristics of the natural bacteriochlorophylls with the robustness of artificial Zn-porphyrins being stable for prolonged periods even upon heating to over 200 degrees C. They assemble on the TiO2 surface to form nano- to micro-crystalline structures with lengths from tens of nm up to several microm and show a photosensitization effect which is supposed to be dependent on the assembly size. The natural examples of these antennas are found in green sulfur bacteria which are able to use photosynthesis in deep water regions with minute light intensities. The implementation of biomimetic antennas for light harvesting and a better photon management may lead to a rise in efficiency of dye-sensitized solar cells also under low light illumination conditions. PMID:19504907

  9. Natural strategies for photosynthetic light harvesting.

    PubMed

    Croce, Roberta; van Amerongen, Herbert

    2014-07-01

    Photosynthetic organisms are crucial for life on Earth as they provide food and oxygen and are at the basis of most energy resources. They have a large variety of light-harvesting strategies that allow them to live nearly everywhere where sunlight can penetrate. They have adapted their pigmentation to the spectral composition of light in their habitat, they acclimate to slowly varying light intensities and they rapidly respond to fast changes in light quality and quantity. This is particularly important for oxygen-producing organisms because an overdose of light in combination with oxygen can be lethal. Rapid progress is being made in understanding how different organisms maximize light harvesting and minimize deleterious effects. Here we summarize the latest findings and explain the main design principles used in nature. The available knowledge can be used for optimizing light harvesting in both natural and artificial photosynthesis to improve light-driven production processes. PMID:24937067

  10. Tetraphenylethene-based star shaped porphyrins: synthesis, self-assembly, and optical and photophysical study.

    PubMed

    Rananaware, Anushri; Bhosale, Rajesh S; Ohkubo, Kei; Patil, Hemlata; Jones, Lathe A; Jackson, Sam L; Fukuzumi, Shunichi; Bhosale, Sidhanath V; Bhosale, Sheshanath V

    2015-04-17

    Supramolecular self-assembly and self-organization are simple and convenient ways to design and create controlled assemblies with organic molecules, and they have provoked great interest due to their potential applications in various fields, such as electronics, photonics, and light-energy conversion. Herein, we describe the synthesis of two ?-conjugated porphyrin molecules bearing tetraphenylethene moieties with high fluorescence quantum yield. Photophysical and electrochemical studies were conducted to understand the physical and redox properties of these new materials, respectively. Furthermore, these derivatives were used to investigate self-assembly via the solvophobic effect. The self-assembled aggregation was performed in nonpolar and polar organic solvents and forms nanospheres and ring-like nanostructures, respectively. The solution based aggregation was studied by means of UV-vis absorption, emission, XRD, and DLS analyses. Self-assembled ring-shape structures were visualized by SEM and TEM imaging. This ring-shape morphology of nanosized macromolecules might be a good candidate for the creation of artificial light-harvesting nanodevices. PMID:25822257

  11. Ni(II)-mediated self-assembly of artificial beta-dipeptides forming a macrocyclic tetranuclear complex with interior spaces for in-line molecular arrangement.

    PubMed

    Miyake, Ryosuke; Tashiro, Shohei; Shiro, Motoo; Tanaka, Kentaro; Shionoya, Mitsuhiko

    2008-04-30

    Metal-mediated self-assembly of bioinspired molecular building blocks shows promise as an excellent strategy to provide well-defined metal arrays and nanoscopic metallo-architectures in a programmable way. Herein, we report Ni(II)-mediated self-assembly of artificial beta-dipeptides (1) which were prepared from a newly designed beta-amino acid bearing a propanediamine ligand as the side chain. The beta-dipeptide (1) has thus two sets of ligands, that is, each building block serves as a tridentate ligand with a bidentate propanediamine unit and an amide carbonyl group. Both C- and N-terminal tridentate ligands in 1 bind to two Ni(II) ions independently, and consequently, four beta-dipeptides are circularly arranged in a head-to-tail fashion to form a macrocyclic tetranuclear Ni(II) complex, Ni414(ClO4)8(H2O)10. The cyclic structure was determined by X-ray analysis and ESI-TOF mass spectrometry. The resulting unique twisted-boat structure allows the formation of isolated spaces for in-line hydrogen-bonded arrangement of water and anion molecules within a hole and two grooves rich in hydrogen bonding groups. PMID:18396868

  12. Self-assembled lipid bilayer materials

    DOEpatents

    Sasaki, Darryl Y.; Waggoner, Tina A.; Last, Julie A.

    2005-11-08

    The present invention is a self-assembling material comprised of stacks of lipid bilayers formed in a columnar structure, where the assembly process is mediated and regulated by chemical recognition events. The material, through the chemical recognition interactions, has a self-regulating system that corrects the radial size of the assembly creating a uniform diameter throughout most of the structure. The materials form and are stable in aqueous solution. These materials are useful as structural elements for the architecture of materials and components in nanotechnology, efficient light harvesting systems for optical sensing, chemical processing centers, and drug delivery vehicles.

  13. The chlorosome: a prototype for efficient light harvesting in photosynthesis

    PubMed Central

    Oostergetel, Gert T.; van Amerongen, Herbert

    2010-01-01

    Three phyla of bacteria include phototrophs that contain unique antenna systems, chlorosomes, as the principal light-harvesting apparatus. Chlorosomes are the largest known supramolecular antenna systems and contain hundreds of thousands of BChl c/d/e molecules enclosed by a single membrane leaflet and a baseplate. The BChl pigments are organized via self-assembly and do not require proteins to provide a scaffold for efficient light harvesting. Their excitation energy flows via a small protein, CsmA embedded in the baseplate to the photosynthetic reaction centres. Chlorosomes allow for photosynthesis at very low light intensities by ultra-rapid transfer of excitations to reaction centres and enable organisms with chlorosomes to live at extraordinarily low light intensities under which no other phototrophic organisms can grow. This article reviews several aspects of chlorosomes: the supramolecular and molecular organizations and the light-harvesting and spectroscopic properties. In addition, it provides some novel information about the organization of the baseplate. PMID:20130996

  14. PHYSICAL REVIEW B 86, 214504 (2012) Artificial and self-assembled vortex-pinning centers in superconducting Ba(Fe1-xCox)2As2 thin films

    E-print Network

    Eom, Chang Beom

    2012-01-01

    in superconducting Ba(Fe1-xCox)2As2 thin films as a route to obtaining very high critical-current densities C on the superior vortex pinning of single- and multilayer Ba(Fe1-xCox)2As2 thin films with self- assembled c-axis and artificially introduced ab-plane pins. Ba(Fe1-xCox)2As2 can accept a very high density of pins (15­20 vol

  15. Quantum mechanical modeling of self-assembly and photoinduced electron transfer in PNA-based artificial living organisms.

    PubMed

    Tamulis, A; Tamulis, V; Graja, A

    2006-04-01

    In order to support the creation of both artificial living organisms in the USA LANL "Protocell Assembly" project and programmable nano-biorobots in the EU "Programmable Artificial Cell Evolution" project, we used quantum mechanical (QM), density functional theory (DFT), the semiempirical PM3 method, and molecular mechanics (MM) software to investigate various complex photosynthetic systems based on peptide nucleic acid (PNA) in a water environment. Quantum mechanical DFT PBEPBE simulations, including electron correlations, confirm that water molecules that surround all the photosynthetic complex of the LANL protoorganism are main constructing factors and stabilize this system consisting of: PNA fragment attached by covalent bond sensitizer 1,4-bis(N,N-dimethylamino)naphthalene molecule, lipid precursor molecule and fragment of lipid molecules mono layer. The absorption spectrum shift to the red wavelengths in the complex artificial protocell photosynthetic center might be used as the measure of the complexity of this system. The electron pi-pi* transitions in the first and third excited states are from HOMO and HOMO-1 located on the conjugated water molecules and sensitizer 1,4-bis(N,N-dimethylamino)naphthalene molecule to the LUMO of the lipid precursor molecule as calculated using the time dependent (TD) PBEPBE/6-31G model. Electron charge tunneling in the first and third excited states should induce metabolic photodissociation of the lipid precursor molecule because of localization of the transferred electron cloud on the head (waste) of the lipid precursor molecule. TD electron correlation PBEPBE/6-31G calculations show that in the different energies of excitation, the charge transfer tunneling is from sensitizer to lipid precursor and cytosine molecules. One should note that in a water solvent, the electron charge transfer pi-pi* transition in the fifth and sixth excited state is from the HOMO and HOMO-1 located on the sensitizer 1,4-bis(N,N-dimethylamino)naphthalene molecule to the LUMO+2 located on the cytosine-PNA fragment molecule. Investigation results indicate that strong back electron tunneling from the sensitizer 1,4-bis(N,N-dimethylamino)naphthalene molecule to the cytosine molecule in the LANL artificial photosynthetic system exists. PMID:16736752

  16. Molecular Self-Assembly

    NSDL National Science Digital Library

    2012-07-19

    In this activity, students interact with 12 models to observe emergent phenomena as molecules assemble themselves. Investigate the factors that are important to self-assembly, including shape and polarity. Try to assemble a monolayer by "pushing" the molecules to the substrate (it's not easy!). Rotate complex molecules to view their structure. Finally, create your own nanostructures by selecting molecules, adding charges to them, and observing the results of self-assembly.

  17. Self-assembly of fluorescent carbon dots in a N,N-dimethylmethanamide solution via Schiff base reaction.

    PubMed

    Hu, Shengliang; Ding, Yanli; Chang, Qing; Trinchi, Adrian; Lin, Kui; Yang, Jinlong; Liu, Jun

    2015-03-14

    The transition from nanoparticles suspended in aqueous solutions into solid fluorescent structures is developed for application in solid functional devices. The presented approach enables the organization of carbon dots into rod-like shapes that can still be re-dispersed into aqueous solution. Schiff bases forming at the surface of carbon dots not only protect their surface states, but also provide sites for tethering to other carbon dots. As a consequence, the large assemblies of CDs can come together to form regular, well ordered structures whilst still maintaining their photoluminescence properties. This opens up enormous possibilities for device manufacture, as these self-assemblies could be grown or grafted onto templates forming regular structures, and find innumerable applications ranging from optoelectronic devices, light harvesting to artificial photosynthesis. PMID:25684699

  18. Self-assembling RNA square.

    PubMed

    Dibrov, Sergey M; McLean, Jaime; Parsons, Jerod; Hermann, Thomas

    2011-04-19

    The three-dimensional structures of noncoding RNA molecules reveal recurring architectural motifs that have been exploited for the design of artificial RNA nanomaterials. Programmed assembly of RNA nanoobjects from autonomously folding tetraloop-receptor complexes as well as junction motifs has been achieved previously through sequence-directed hybridization of complex sets of long oligonucleotides. Due to size and complexity, structural characterization of artificial RNA nanoobjects has been limited to low-resolution microscopy studies. Here we present the design, construction, and crystal structure determination at 2.2 ? of the smallest yet square-shaped nanoobject made entirely of double-stranded RNA. The RNA square is comprised of 100 residues and self-assembles from four copies each of two oligonucleotides of 10 and 15 bases length. Despite the high symmetry on the level of secondary structure, the three-dimensional architecture of the square is asymmetric, with all four corners adopting distinct folding patterns. We demonstrate the programmed self-assembly of RNA squares from complex mixtures of corner units and establish a concept to exploit the RNA square as a combinatorial nanoscale platform. PMID:21464284

  19. Self-assembly of fluorescent carbon dots in a N,N-dimethylmethanamide solution via Schiff base reaction

    NASA Astrophysics Data System (ADS)

    Hu, Shengliang; Ding, Yanli; Chang, Qing; Trinchi, Adrian; Lin, Kui; Yang, Jinlong; Liu, Jun

    2015-02-01

    The transition from nanoparticles suspended in aqueous solutions into solid fluorescent structures is developed for application in solid functional devices. The presented approach enables the organization of carbon dots into rod-like shapes that can still be re-dispersed into aqueous solution. Schiff bases forming at the surface of carbon dots not only protect their surface states, but also provide sites for tethering to other carbon dots. As a consequence, the large assemblies of CDs can come together to form regular, well ordered structures whilst still maintaining their photoluminescence properties. This opens up enormous possibilities for device manufacture, as these self-assemblies could be grown or grafted onto templates forming regular structures, and find innumerable applications ranging from optoelectronic devices, light harvesting to artificial photosynthesis.The transition from nanoparticles suspended in aqueous solutions into solid fluorescent structures is developed for application in solid functional devices. The presented approach enables the organization of carbon dots into rod-like shapes that can still be re-dispersed into aqueous solution. Schiff bases forming at the surface of carbon dots not only protect their surface states, but also provide sites for tethering to other carbon dots. As a consequence, the large assemblies of CDs can come together to form regular, well ordered structures whilst still maintaining their photoluminescence properties. This opens up enormous possibilities for device manufacture, as these self-assemblies could be grown or grafted onto templates forming regular structures, and find innumerable applications ranging from optoelectronic devices, light harvesting to artificial photosynthesis. Electronic supplementary information (ESI) available: Experimental details and more characterization of carbon dot assemblies. See DOI: 10.1039/c4nr07119k

  20. Principles of light harvesting from single photosynthetic complexes.

    PubMed

    Schlau-Cohen, G S

    2015-06-01

    Photosynthetic systems harness sunlight to power most life on Earth. In the initial steps of photosynthetic light harvesting, absorbed energy is converted to chemical energy with near-unity quantum efficiency. This is achieved by an efficient, directional and regulated flow of energy through a network of proteins. Here, we discuss the following three key principles of this flow and of photosynthetic light harvesting: thermal fluctuations of the protein structure; intrinsic conformational switches with defined functional consequences; and environmentally triggered conformational switches. Through these principles, photosynthetic systems balance two types of operational costs: metabolic costs, or the cost of maintaining and running the molecular machinery, and opportunity costs, or the cost of losing any operational time. Understanding how the molecular machinery and dynamics are designed to balance these costs may provide a blueprint for improved artificial light-harvesting devices. With a multi-disciplinary approach combining knowledge of biology, this blueprint could lead to low-cost and more effective solar energy conversion. Photosynthetic systems achieve widespread light harvesting across the Earth's surface; in the face of our growing energy needs, this is functionality we need to replicate, and perhaps emulate. PMID:26052423

  1. Modeling Self Assembly

    NSDL National Science Digital Library

    This lesson, presented by the National Nanotechnology Infrastructure Network, covers self-assembly of molecules. Two activity are contained in this lesson. The first is "a hands-on modeling activity designed to introduce students to the area of nanotechnology and give them a basic understanding of how researchers build very small devices by the self-assembly of molecules." The second activity follows up on the first and gives "the students a chance to practice and demonstrate what they have learned." Two Teacher Preparation Guides and Two Student Guides are included. 

  2. Assembly of Bacterial Light-Harvesting Complexes on Solid Substrates

    Microsoft Academic Search

    Kouji Iida; Takehisa Dewa; Mamoru Nango

    Light-harvesting (LH) and reaction center (RC) complexes were adsorbed onto mica and gold substrates, in order to assemble\\u000a an artificial antenna complex on a solid support, with the eventual aim of developing useful nanodevices. The normal near-infra-red\\u000a (IR) absorption spectra of photosynthetic complexes were retained indicating stable assembly on these solid substrates. Atomic\\u000a Force Microscopy (AFM) of reassociated LH1 complexes,

  3. Self-assembly concepts for multicompartment nanostructures.

    PubMed

    Gröschel, André H; Müller, Axel H E

    2015-07-28

    Compartmentalization is ubiquitous to many biological and artificial systems, be it for the separate storage of incompatible matter or to isolate transport processes. Advancements in the synthesis of sequential block copolymers offer a variety of tools to replicate natural design principles with tailor-made soft matter for the precise spatial separation of functionalities on multiple length scales. Here, we review recent trends in the self-assembly of amphiphilic block copolymers to multicompartment nanostructures (MCNs) under (semi-)dilute conditions, with special emphasis on ABC triblock terpolymers. The intrinsic immiscibility of connected blocks induces short-range repulsion into discrete nano-domains stabilized by a third, soluble block or molecular additive. Polymer blocks can be synthesized from an arsenal of functional monomers directing self-assembly through packing frustration or response to various fields. The mobility in solution further allows the manipulation of self-assembly processes into specific directions by clever choice of environmental conditions. This review focuses on practical concepts that direct self-assembly into predictable nanostructures, while narrowing particle dispersity with respect to size, shape and internal morphology. The growing understanding of underlying self-assembly mechanisms expands the number of experimental concepts providing the means to target and manipulate progressively complex superstructures. PMID:26123217

  4. Biogenesis of light harvesting proteins.

    PubMed

    Dall'Osto, Luca; Bressan, Mauro; Bassi, Roberto

    2015-09-01

    The LHC family includes nuclear-encoded, integral thylakoid membrane proteins, most of which coordinate chlorophyll and xanthophyll chromophores. By assembling with the core complexes of both photosystems, LHCs form a flexible peripheral moiety for enhancing light-harvesting cross-section, regulating its efficiency and providing protection against photo-oxidative stress. Upon its first appearance, LHC proteins underwent evolutionary diversification into a large protein family with a complex genetic redundancy. Such differentiation appears as a crucial event in the adaptation of photosynthetic organisms to changing environmental conditions and land colonization. The structure of photosystems, including nuclear- and chloroplast-encoded subunits, presented the cell with a number of challenges for the control of the light harvesting function. Indeed, LHC-encoding messages are translated in the cytosol, and pre-proteins imported into the chloroplast, processed to their mature size and targeted to the thylakoids where are assembled with chromophores. Thus, a tight coordination between nuclear and plastid gene expression, in response to environmental stimuli, is required to adjust LHC composition during photoacclimation. In recent years, remarkable progress has been achieved in elucidating structure, function and regulatory pathways involving LHCs; however, a number of molecular details still await elucidation. In this review, we will provide an overview on the current knowledge on LHC biogenesis, ranging from organization of pigment-protein complexes to the modulation of gene expression, import and targeting to the photosynthetic membranes, and regulation of LHC assembly and turnover. Genes controlling these events are potential candidate for biotechnological applications aimed at optimizing light use efficiency of photosynthetic organisms. This article is part of a Special Issue entitled: Chloroplast biogenesis. PMID:25687893

  5. Toward a molecular programming language for algorithmic self-assembly

    NASA Astrophysics Data System (ADS)

    Patitz, Matthew John

    Self-assembly is the process whereby relatively simple components autonomously combine to form more complex objects. Nature exhibits self-assembly to form everything from microscopic crystals to living cells to galaxies. With a desire to both form increasingly sophisticated products and to understand the basic components of living systems, scientists have developed and studied artificial self-assembling systems. One such framework is the Tile Assembly Model introduced by Erik Winfree in 1998. In this model, simple two-dimensional square 'tiles' are designed so that they self-assemble into desired shapes. The work in this thesis consists of a series of results which build toward the future goal of designing an abstracted, high-level programming language for designing the molecular components of self-assembling systems which can perform powerful computations and form into intricate structures. The first two sets of results demonstrate self-assembling systems which perform infinite series of computations that characterize computably enumerable and decidable languages, and exhibit tools for algorithmically generating the necessary sets of tiles. In the next chapter, methods for generating tile sets which self-assemble into complicated shapes, namely a class of discrete self-similar fractal structures, are presented. Next, a software package for graphically designing tile sets, simulating their self-assembly, and debugging designed systems is discussed. Finally, a high-level programming language which abstracts much of the complexity and tedium of designing such systems, while preventing many of the common errors, is presented. The summation of this body of work presents a broad coverage of the spectrum of desired outputs from artificial self-assembling systems and a progression in the sophistication of tools used to design them. By creating a broader and deeper set of modular tools for designing self-assembling systems, we hope to increase the complexity which is attainable. These tools provide a solid foundation for future work in both the Tile Assembly Model and explorations into more advanced models.

  6. Nanopropulsion by biocatalytic self-assembly.

    PubMed

    Leckie, Joy; Hope, Alexander; Hughes, Meghan; Debnath, Sisir; Fleming, Scott; Wark, Alastair W; Ulijn, Rein V; Haw, Mark D

    2014-09-23

    A number of organisms and organelles are capable of self-propulsion at the micro- and nanoscales. Production of simple man-made mimics of biological transportation systems may prove relevant to achieving movement in artificial cells and nano/micronscale robotics that may be of biological and nanotechnological importance. We demonstrate the propulsion of particles based on catalytically controlled molecular self-assembly and fiber formation at the particle surface. Specifically, phosphatase enzymes (acting as the engine) are conjugated to a quantum dot (the vehicle), and are subsequently exposed to micellar aggregates (fuel) that upon biocatalytic dephosphorylation undergo fibrillar self-assembly, which in turn causes propulsion. The motion of individual enzyme/quantum dot conjugates is followed directly using fluorescence microscopy. While overall movement remains random, the enzyme-conjugates exhibit significantly faster transport in the presence of the fiber forming system, compared to controls without fuel, a non-self-assembling substrate, or a substrate which assembles into spherical, rather than fibrous structures upon enzymatic dephosphorylation. When increasing the concentration of the fiber-forming fuel, the speed of the conjugates increases compared to non-self-assembling substrate, although directionality remains random. PMID:25162764

  7. Efficient energy transfer in light-harvesting systems, I: optimal temperature, reorganization energy and spatial–temporal correlations

    E-print Network

    Wu, Jianlan

    Understanding the mechanisms of efficient and robust energy transfer in light-harvesting systems provides new insights for the optimal design of artificial systems. In this paper, we use the Fenna–Matthews–Olson (FMO) ...

  8. Functionalized Nanoparticles and Surfaces for Controlled Chemical Catalysis and Effective Light Harvesting

    SciTech Connect

    Marye Anne Fox, James K. Whitesell

    2012-11-02

    We have prepared a range of such arrays as key components for biotechnology and photonic applications. These involve self-assembled arrays of increasing complexity with three-dimensionally disposed multilayer interactions. These arrays also include dendrimers as the distinguishing structural building blocks. These photoactive integrated systems have a regular, highly-branched, three-dimensional architecture. Structural modifications of these units include variation of the core, bridging layers, and terminal groups. These modifications result in a large array of dendritic molecules with potential applications for light harvesting.

  9. Activation energy-based simulation for self-assembly of multi-shape tiles

    Microsoft Academic Search

    Mostafa Mostafa Hashim Ellabaan

    2007-01-01

    Building artificial systems using self-assembly is one of the main issues of artificial life [17]. Scientists are trying to understand this process either using experimental approaches or computer simulation approaches. This paper aims at supporting research using computer simulation approaches mimicking self-assembly as it occurs in the real world using basic principles in physics such as Brownian motion and basic

  10. Self-Assembling Circuits Plasticity in Self-Assembly: Templating

    E-print Network

    Prentiss, Mara

    ] Neural circuits follow an adaptive, bottom- up plan, and assemble themselves of individual componentsSelf-Assembling Circuits Plasticity in Self-Assembly: Templating Generates Functionally Different Circuits from a Single Precursor** Mila Boncheva, Rosaria Ferrigno, Derek A. Bruzewicz, and George M

  11. Exploring Fabrication: Self-Assembly

    NSDL National Science Digital Library

    2014-06-10

    In this activity, learners participate in several full-body interactive games to model the process of self-assembly in nature and nanotechnology. Through these activities learners assemble into a ring, a capsule, and a snowflake. Learners discover that self-assembly is a process by which molecules and cells form themselves into functional structures. Note: this activity requires at least nine learners.

  12. ?-Carotene to bacteriochlorophyll c energy transfer in self-assembled aggregates mimicking chlorosomes

    Microsoft Academic Search

    J. Alster; T. Polívka; J. B. Arellano; P. Chábera; F. Vácha; J. Pšen?ík

    2010-01-01

    Carotenoids are together with bacteriochlorophylls important constituents of chlorosomes, the light-harvesting antennae of green photosynthetic bacteria. Majority of bacteriochlorophyll molecules form self-assembling aggregates inside the chlorosomes. Aggregates of bacteriochlorophylls with optical properties similar to those of chlorosomes can also be prepared in non-polar organic solvents or in aqueous environments when a suitable non-polar molecule is added. In this work, the

  13. Microfluidic self assembly

    E-print Network

    Bingqing Shen; Joshua Ricouvier; Mathilde Reyssat; Florent Malloggi; Patrick Tabeling

    2014-09-14

    Recent progress in colloidal science has led to elaborate self-assembled structures whose complexity raises hopes for elaborating new materials. However, the throughputs are extremely low and consequently, the chance to produce materials of industrial interest, for instance, groundbreaking optical devices, harnessing complete three-dimensional band gaps, is markedly low. We discovered a novel hydrodynamic effect that may unlock this bottleneck. It is based on the dipolar flow interactions that build up when droplets are slowed down by the microchannel walls along which they are transported. Coupled with depletion forces, we succeeded to form, via a continuous flow process, at unprecedented speeds and under exquisite control, a rich ensemble of monodisperse planar and tridimensional clusters, such as chains, triangles, diamonds, tetahedrons, heterotrimers, possessing geometrical, chemical, and/or magnetic anisotropies enabling directional bonding. Continuous productions of millions of building blocks per second for elaborating new functional materials can be envisioned.

  14. Quantum entanglement in photosynthetic light harvesting complexes

    E-print Network

    Mohan Sarovar; Akihito Ishizaki; Graham R. Fleming; K. Birgitta Whaley

    2010-06-07

    Light harvesting components of photosynthetic organisms are complex, coupled, many-body quantum systems, in which electronic coherence has recently been shown to survive for relatively long time scales despite the decohering effects of their environments. Within this context, we analyze entanglement in multi-chromophoric light harvesting complexes, and establish methods for quantification of entanglement by presenting necessary and sufficient conditions for entanglement and by deriving a measure of global entanglement. These methods are then applied to the Fenna-Matthews-Olson (FMO) protein to extract the initial state and temperature dependencies of entanglement. We show that while FMO in natural conditions largely contains bipartite entanglement between dimerized chromophores, a small amount of long-range and multipartite entanglement exists even at physiological temperatures. This constitutes the first rigorous quantification of entanglement in a biological system. Finally, we discuss the practical utilization of entanglement in densely packed molecular aggregates such as light harvesting complexes.

  15. Nanotechnology and Quasicrystals: From self assembly to photonic applications

    E-print Network

    Ron Lifshitz

    2008-10-28

    After providing a concise overview on quasicrystals and their discovery more than a quarter of a century ago, I consider the unexpected interplay between nanotechnology and quasiperiodic crystals. Of particular relevance are efforts to fabricate artificial functional micro- or nanostructures, as well as efforts to control the self-assembly of nanostructures, where current knowledge about the possibility of having long-range order without periodicity can provide significant advantages. I discuss examples of systems ranging from artificial metamaterials for photonic applications, through self-assembled soft matter, to surface waves and optically-induced nonlinear photonic quasicrystals.

  16. Self-assembly and nanotechnology

    NASA Astrophysics Data System (ADS)

    Whitesides, George M.

    1996-02-01

    Molecular self-assembly is a strategy for nanofabrication that involves designing molecules and supramolecular entities so that shape-complementarity causes them to aggregate into desired structures. Self-assembly has a number of advantages as a strategy: first, it carries out many of the most difficult steps in nanofabrication -- those involving atomic-level modification of structure -- using the very highly developed techniques of synthetic chemistry. Second, it draws from the enormous wealth of examples in biology for inspiration: self-assembly is one of the most important strategies used in biology for the development of complex, functional structures. Third, it can incorporate biological structures directly as components in the final systems. Fourth, because it requires that the target structures be the thermodynamically most stable ones open to the system, it tends to produce structures that are relatively defect-free and self-healing. Self-assembly also poses a number of substantial intellectual challenges. The brief summary of these challenges is that we do not yet know how to do it, and cannot even mimic those processes known to occur in biological systems at other than quite elementary levels. In addition, there are issues of function in self-assembled aggregates that need solution. The most promising avenues for self-assembly are presently those based on organic compounds, and organic compounds, as a group (although with exceptions), are electrical insulators; thus, many ideas for information processing and electrical/mechanical transduction will require either fundamental redesign in going from the macroscopic systems presently used to self-assembled systems, or the development of new types of organic molecules that show appropriate properties. This talk outlines some of these issues, and illustrates one of the approaches to self-assembled structures that has been particularly successful: that is, self- assembly on surfaces. There are now a range of different molecular systems that self-assemble -- that is, form ordered, monomolecular structures -- by the coordination of molecules to surfaces. These systems -- self-assembled monomlayers (SAMs) -- are reasonably well understood, and increasingly useful technologically. The crucial dimension in SAMs is the thickness perpendicular to the plane of the monolayer: this dimension, and the composition along this axis, can be controlled very simply at the scale of 0.1 nm by controlling the structures of the molecules making up the monolayer. (truncated)

  17. Biomimetic self-assembling acylphthalocyanines.

    PubMed

    Jin, Hong-Guang; Balaban, Mihaela Carmen; Chevallier-Michaud, Sabine; Righezza, Michel; Balaban, Teodor Silviu

    2015-07-01

    We synthesized a series of biomimetic self-assembling phthalocyanines equipped with carbonyl groups as recognition motifs, a central zinc atom and diverse solubilizing alkyl chains mimicking for the first time with these robust pigments the natural chlorosomal bacteriochlorophylls. Upon self-assembly a very broad and red-shifted Q-band absorption extending to over 900 nm is put into evidence. PMID:26112252

  18. Self-assembly and nanotechnology

    Microsoft Academic Search

    George M. Whitesides

    1996-01-01

    Molecular self-assembly is a strategy for nanofabrication that involves designing molecules and supramolecular entities so that shape-complementarity causes them to aggregate into desired structures. Self-assembly has a number of advantages as a strategy: first, it carries out many of the most difficult steps in nanofabrication -- those involving atomic-level modification of structure -- using the very highly developed techniques of

  19. Self-Assembling Dessert Toppings

    NSDL National Science Digital Library

    2012-12-27

    This is an activity (located on page 3 of the PDF) about self-assembly, the ability of molecules to assemble themselves according to certain rules. Learners will use food-grade components to create delicious dessert topping-filled gel capsules, macroscale relatives of the capsules nanoscientists make in a lab to carry medicine to targeted cells of the body. Relates to linked video, DragonflyTV Nano: Self-Assembly.

  20. Quantum entanglement in photosynthetic light harvesting complexes

    E-print Network

    Sarovar, Mohan; Fleming, Graham R; Whaley, K Birgitta

    2009-01-01

    Light harvesting components of photosynthetic organisms are complex, coupled, many-body quantum systems, in which electronic coherence has recently been shown to survive for relatively long time scales despite the decohering effects of their environments. Within this context, we critically analyze entanglement in multi-chromophoric light harvesting complexes; we clarify the connection between coherence and entanglement in these systems, and establish methods for quantification of entanglement by presenting necessary and sufficient conditions for entanglement and by deriving a measure of global entanglement. These methods are then applied to the Fenna-Matthews-Olson (FMO) protein to extract the initial state and temperature dependencies of entanglement in this complex. We show that while FMO in natural conditions largely contains bipartite entanglement between dimerized chromophores, a small amount of long-range and multipartite entanglement exists even at physiological temperatures. This constitutes the first...

  1. Temperature and Ionic Strength Effects on the Chlorosome Light-Harvesting Antenna Complex

    SciTech Connect

    Tang, Kuo-Hsiang; Zhu, Liying; Urban, Volker S; Collins, Aaron M.; Biswas, Pratim; Blankenship, R. E.

    2011-01-01

    Chlorosomes, the peripheral light-harvesting antenna complex from green photosynthetic bacteria, are the largest and one of the most efficient light-harvesting antenna complexes found in nature. In contrast to other light-harvesting antennas, chlorosomes are constructed from more than 150?000 self-assembled bacteriochlorophylls (BChls) and contain relatively few proteins that play secondary roles. These unique properties have led to chlorosomes as an attractive candidate for developing biohybrid solar cell devices. In this article, we investigate the temperature and ionic strength effects on the viability of chlorosomes from the photosynthetic green bacterium Chloroflexus aurantiacus using small-angle neutron scattering and dynamic light scattering. Our studies indicate that chlorosomes remain intact up to 75 °C and that salt induces the formation of large aggregates of chlorosomes. No internal structural changes are observed for the aggregates. The salt-induced aggregation, which is a reversible process, is more efficient with divalent metal ions than with monovalent metal ions. Moreover, with treatment at 98 °C for 2 min, the bulk of the chlorosome pigments are undamaged, while the baseplate is destroyed. Chlorosomes without the baseplate remain rodlike in shape and are 30?40% smaller than with the baseplate attached. Further, chlorosomes are stable from pH 5.5 to 11.0. Together, this is the first time such a range of characterization tools have been used for chlorosomes, and this has enabled elucidation of properties that are not only important to understanding their functionality but also may be useful in biohybrid devices for effective light harvesting.

  2. Quantum entanglement in photosynthetic light harvesting

    Microsoft Academic Search

    Mohan Sarovar; Akihito Ishizaki; Graham Fleming; Birgitta Whaley

    2009-01-01

    Identification of non-trivial quantum mechanical effects in the functioning of biological systems has been a long-standing and elusive goal in the fields of physics, chemistry and biology. Recent progress in control and measurement technologies, especially in the optical spectroscopy domain, have made possible the identification of such effects. I examine light harvesting components of photosynthetic organisms -- complex, coupled, many-body

  3. Evolution and function of light harvesting proteins.

    PubMed

    Büchel, Claudia

    2015-01-01

    Photosynthetic eukaryotes exhibit very different light-harvesting proteins, but all contain membrane-intrinsic light-harvesting complexes (Lhcs), either as additional or sole antennae. Lhcs non-covalently bind chlorophyll a and in most cases another Chl, as well as very different carotenoids, depending on the taxon. The proteins fall into two major groups: The well-defined Lhca/b group of proteins binds typically Chl b and lutein, and the group is present in the 'green lineage'. The other group consists of Lhcr/Lhcf, Lhcz and Lhcx/LhcSR proteins. The former are found in the so-called Chromalveolates, where they mostly bind Chl c and carotenoids very efficient in excitation energy transfer, and in their red algae ancestors. Lhcx/LhcSR are present in most Chromalveolates and in some members of the green lineage as well. Lhcs function in light harvesting, but also in photoprotection, and they influence the organisation of the thylakoid membrane. The different functions of the Lhc subfamilies are discussed in the light of their evolution. PMID:25240794

  4. Self-assembling amphiphilic peptides†

    PubMed Central

    Dehsorkhi, Ashkan; Castelletto, Valeria; Hamley, Ian W

    2014-01-01

    The self-assembly of several classes of amphiphilic peptides is reviewed, and selected applications are discussed. We discuss recent work on the self-assembly of lipopeptides, surfactant-like peptides and amyloid peptides derived from the amyloid-? peptide. The influence of environmental variables such as pH and temperature on aggregate nanostructure is discussed. Enzyme-induced remodelling due to peptide cleavage and nanostructure control through photocleavage or photo-cross-linking are also considered. Lastly, selected applications of amphiphilic peptides in biomedicine and materials science are outlined. © 2014 The Authors. Journal of Peptide Science published by European Peptide Society and John Wiley & Sons, Ltd. PMID:24729276

  5. Solder self-assembly for MEMS fabrication

    E-print Network

    Au, Hin Meng, 1977-

    2004-01-01

    This thesis examines and demonstrates self-assembly of MEMS components on the 25 micron scale onto substrates using the capillary force of solder. This is an order of magnitude smaller than current solder self-assembly in ...

  6. Surface Modification with Self-Assembled Monolayer &

    E-print Network

    Hong, Deog Ki

    1 1 / 40 Surface Modification with Self-Assembled Monolayer & Polymer Brush for Biotechnology Surface Modification with Self-Assembled Monolayer & Polymer Brush for Biotechnology 2 / 40 linear star comb / brush network/ crosslinked dendritic / hyperbranched homopolymer random copolymer periodic

  7. Light-Harvesting Nanoparticle Core-Shell Clusters with Controllable Optical Output.

    PubMed

    Sun, Dazhi; Tian, Ye; Zhang, Yugang; Xu, Zhihua; Sfeir, Matthew Y; Cotlet, Mircea; Gang, Oleg

    2015-06-23

    We used DNA self-assembly methods to fabricate a series of core-shell gold nanoparticle-DNA-colloidal quantum dot (AuNP-DNA-Qdot) nanoclusters with satellite-like architecture to modulate optical (photoluminescence) response. By varying the intercomponent distance through the DNA linker length designs, we demonstrate precise tuning of the plasmon-exciton interaction and the optical behavior of the nanoclusters from regimes characterized by photoluminescence quenching to photoluminescence enhancement. The combination of detailed X-ray scattering probing with photoluminescence intensity and lifetime studies revealed the relation between the cluster structure and its optical output. Compared to conventional light-harvesting systems like conjugated polymers and multichromophoric dendrimers, the proposed nanoclusters bring enhanced flexibility in controlling the optical behavior toward a desired application, and they can be regarded as controllable optical switches via the optically pumped color. PMID:25933097

  8. Patterning self-assembled monolayers using microcontact

    E-print Network

    Mrksich, Milan

    228 reviews Patterning self-assembled monolayers using microcontact printing: a new technology for biosensors? Milan Mrksich and George M. Whitesides Self-assembled monolayers (SAMs), formed upon. The system of self-assembled monolayers (SAMs) of alkanethiolates on gold is probably the best that is cur

  9. Combining Self-Assembled Monolayers and Mass

    E-print Network

    Mrksich, Milan

    Combining Self-Assembled Monolayers and Mass Spectrometry for Applications in Biochips Zachary A. The discussion emphasizes the use of self-assembled monolayers of alkanethiolates on gold as a structurally well current work with self-assembled monolayers (SAMs) to tailor the interfacial layer, and emphasize current

  10. Quantum mechanical light harvesting mechanisms in photosynthesis

    NASA Astrophysics Data System (ADS)

    Scholes, Gregory

    2012-02-01

    More than 10 million billion photons of light strike a leaf each second. Incredibly, almost every red-coloured photon is captured by chlorophyll pigments and initiates steps to plant growth. Last year we reported that marine algae use quantum mechanics in order to optimize photosynthesis [1], a process essential to its survival. These and other insights from the natural world promise to revolutionize our ability to harness the power of the sun. In a recent review [2] we described the principles learned from studies of various natural antenna complexes and suggested how to utilize that knowledge to shape future technologies. We forecast the need to develop ways to direct and regulate excitation energy flow using molecular organizations that facilitate feedback and control--not easy given that the energy is only stored for a billionth of a second. In this presentation I will describe new results that explain the observation and meaning of quantum-coherent energy transfer. [4pt] [1] Elisabetta Collini, Cathy Y. Wong, Krystyna E. Wilk, Paul M. G. Curmi, Paul Brumer, and Gregory D. Scholes, ``Coherently wired light-harvesting in photosynthetic marine algae at ambient temperature'' Nature 463, 644-648 (2010).[0pt] [2] Gregory D. Scholes, Graham R. Fleming, Alexandra Olaya-Castro and Rienk van Grondelle, ``Lessons from nature about solar light harvesting'' Nature Chem. 3, 763-774 (2011).

  11. Nanoparticles in a capillary trap: dynamic self-assembly at fluid interfaces.

    PubMed

    Sashuk, Volodymyr; Winkler, Katarzyna; ?ywoci?ski, Andrzej; Wojciechowski, Tomasz; Górecka, Ewa; Fia?kowski, Marcin

    2013-10-22

    Dynamic self-assembly is an emerging scientific concept aimed to construct artificial systems of adaptative behavior. Here, we present a first nanoscopic system that is able to dynamically self-assemble in two dimensions. This system is composed of charged gold nanoparticles, dispersed at the air-water interface, which self-assemble into a dense monolayer of area of several square centimeters in response to surface tension gradient. The surface tension gradient is imposed by localized addition or removal of organic solvent from the interface. After the surface tension is equalized over the whole fluid interface, the nanoparticles return to their initial dispersed state. The arrangement of nanoparticles before and after the self-assembly was characterized using SEM microscopy and SAXS spectroscopy. The constructed self-assembling system offers a "chemical" alternative for the Langmuir-Blodgett technique. Also, it was applied for creating self-erasing nanoparticle patterns on a fluid surface. PMID:24016224

  12. Long range excitonic transport in a biomimetic system inspired by the bacterial light-harvesting apparatus

    SciTech Connect

    Harel, Elad [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208 (United States)

    2012-05-07

    Photosynthesis, the process by which energy from sunlight drives cellular metabolism, relies on a unique organization of light-harvesting and reaction center complexes. Recently, the organization of light-harvesting LH2 complexes and dimeric reaction center-light-harvesting I-PufX core complexes in membranes of purple non-sulfur bacteria was revealed by atomic force microscopy [S. Bahatyrova et al., Nature (London) 430, 1058 (2004)]. Here, we discuss optimal exciton transfer in a biomimetic system closely modeled on the structure of LH2 and its organization within the membrane using a Markovian quantum model with dissipation and trapping added phenomenologically. In a deliberate manner, we neglect the high level detail of the bacterial light-harvesting complex and its interaction with the phonon bath in order to elucidate a set of design principles that may be incorporated in artificial pigment-scaffold constructs in a supramolecular assembly. We show that our scheme reproduces many of the most salient features found in their natural counterpart and may be largely explained by simple electrostatic considerations. Most importantly, we show that quantum effects act primarily to enforce robustness with respect to spatial and spectral disorder between and within complexes. The implications of such an arrangement are discussed in the context of biomimetic photosynthetic analogs capable of transferring energy efficiently across tens to hundreds of nanometers.

  13. Structure-based model for light-harvesting properties of nucleic acid nanostructures

    PubMed Central

    Pan, Keyao; Boulais, Etienne; Yang, Lun; Bathe, Mark

    2014-01-01

    Programmed self-assembly of DNA enables the rational design of megadalton-scale macromolecular assemblies with sub-nanometer scale precision. These assemblies can be programmed to serve as structural scaffolds for secondary chromophore molecules with light-harvesting properties. Like in natural systems, the local and global spatial organization of these synthetic scaffolded chromophore systems plays a crucial role in their emergent excitonic and optical properties. Previously, we introduced a computational model to predict the large-scale 3D solution structure and flexibility of nucleic acid nanostructures programmed using the principle of scaffolded DNA origami. Here, we use Förster resonance energy transfer theory to simulate the temporal dynamics of dye excitation and energy transfer accounting both for overall DNA nanostructure architecture as well as atomic-level DNA and dye chemical structure and composition. Results are used to calculate emergent optical properties including effective absorption cross-section, absorption and emission spectra and total power transferred to a biomimetic reaction center in an existing seven-helix double stranded DNA-based antenna. This structure-based computational framework enables the efficient in silico evaluation of nucleic acid nanostructures for diverse light-harvesting and photonic applications. PMID:24311563

  14. Multifunctional self-assembled monolayers

    SciTech Connect

    Zawodzinski, T.; Bar, G.; Rubin, S.; Uribe, F. [Los Alamos National Lab., NM (United States); Ferrais, J. [Texas Univ., Dallas, TX (United States)

    1996-06-01

    This is the final report of at three year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The specific goals of this research project were threefold: to develop multifunctional self-assembled monolayers, to understand the role of monolayer structure on the functioning of such systems, and to apply this knowledge to the development of electrochemical enzyme sensors. An array of molecules that can be used to attach electrochemically active biomolecules to gold surfaces has been synthesized. Several members of a class of electroactive compounds have been characterized and the factors controlling surface modification are beginning to be characterized. Enzymes have been attached to self-assembled molecules arranged on the gold surface, a critical step toward the ultimate goal of this project. Several alternative enzyme attachment strategies to achieve robust enzyme- modified surfaces have been explored. Several means of juxtaposing enzymes and mediators, electroactive compounds through which the enzyme can exchange electrons with the electrode surface, have also been investigated. Finally, the development of sensitive biosensors based on films loaded with nanoscale-supported gold particles that have surface modified with the self-assembled enzyme and mediator have been explored.

  15. Self-assembled peptide architecture with a tooth shape: folding into shape.

    PubMed

    Kwon, Sunbum; Shin, Hye Sun; Gong, Jintaek; Eom, Jae-Hoon; Jeon, Aram; Yoo, Sung Hyun; Chung, Im Sik; Cho, Sung June; Lee, Hee-Seung

    2011-11-01

    Molecular self-assembly is the spontaneous association of molecules into structured aggregates by which nature builds complex functional systems. While numerous examples have focused on 2D self-assembly to understand the underlying mechanism and mimic this process to create artificial nano- and microstructures, limited progress has been made toward 3D self-assembly on the molecular level. Here we show that a helical ?-peptide foldamer, an artificial protein fragment, with well-defined secondary structure self-assembles to form an unprecedented 3D molecular architecture with a molar tooth shape in a controlled manner in aqueous solution. Powder X-ray diffraction analysis, combined with global optimization and Rietveld refinement, allowed us to propose its molecular arrangement. We found that four individual left-handed helical monomers constitute a right-handed superhelix in a unit cell of the assembly, similar to that found in the supercoiled structure of collagen. PMID:21985392

  16. Photonic crystals for improved light harvesting

    NASA Astrophysics Data System (ADS)

    Clays, Koen; Kolaric, Branko; Baert, Kasper; Vallée, Renaud A. L.

    2008-08-01

    The fluorescence of chromophores embedded in a photonic crystal is inhibited by the presence of a photonic pseudo-gap. We present the influence of such an incomplete bandgap on the emission and energy transfer by studying the steady-state and time-resolved emission properties of both a donor and an acceptor fluorophore in a self-assembled photonic crystal. Our results clearly show an inhibition of the donor emission and a concomitant enhancement of the acceptor emission, indicating improved energy transfer from donor to acceptor. This is explained by the decreased number of available photonic modes for radiative decay for the donor in a suitable engineered photonic crystal with respect to in the effective homogeneous medium.

  17. Chemical Reactions Directed Peptide Self-Assembly

    PubMed Central

    Rasale, Dnyaneshwar B.; Das, Apurba K.

    2015-01-01

    Fabrication of self-assembled nanostructures is one of the important aspects in nanoscience and nanotechnology. The study of self-assembled soft materials remains an area of interest due to their potential applications in biomedicine. The versatile properties of soft materials can be tuned using a bottom up approach of small molecules. Peptide based self-assembly has significant impact in biology because of its unique features such as biocompatibility, straight peptide chain and the presence of different side chain functionality. These unique features explore peptides in various self-assembly process. In this review, we briefly introduce chemical reaction-mediated peptide self-assembly. Herein, we have emphasised enzymes, native chemical ligation and photochemical reactions in the exploration of peptide self-assembly. PMID:25984603

  18. Chemical reactions directed Peptide self-assembly.

    PubMed

    Rasale, Dnyaneshwar B; Das, Apurba K

    2015-01-01

    Fabrication of self-assembled nanostructures is one of the important aspects in nanoscience and nanotechnology. The study of self-assembled soft materials remains an area of interest due to their potential applications in biomedicine. The versatile properties of soft materials can be tuned using a bottom up approach of small molecules. Peptide based self-assembly has significant impact in biology because of its unique features such as biocompatibility, straight peptide chain and the presence of different side chain functionality. These unique features explore peptides in various self-assembly process. In this review, we briefly introduce chemical reaction-mediated peptide self-assembly. Herein, we have emphasised enzymes, native chemical ligation and photochemical reactions in the exploration of peptide self-assembly. PMID:25984603

  19. Self-assembling magnetic "snakes"

    SciTech Connect

    None

    2010-01-01

    Nickel particles float peacefully in a liquid medium until a giant snake seems to swim by and snatch several particles up, adding to its own mass. The self-assembled "snakes" act like biological systems, but they are not alive and are driven by a magnetic field. The research may someday offer some insight into the organization of life itself. Read more at Wired: http://www.wired.com/wiredscience/2009/03/snakes/ Research and video by Alex Snezhko and Igor Aronson, Argonne National Laboratory.

  20. Self-Assembly at All Scales

    Microsoft Academic Search

    George M. Whitesides; Bartosz Grzybowski

    2002-01-01

    Self-assembly is the autonomous organization of components into patterns or structures without human intervention. Self-assembling processes are common throughout nature and technology. They involve components from the molecular (crystals) to the planetary (weather systems) scale and many different kinds of interactions. The concept of self-assembly is used increasingly in many disciplines, with a different flavor and emphasis in each.

  1. Triangular and Hexagonal Tile Self-Assembly Systems Triangular and Hexagonal Tile Self-Assembly Systems

    E-print Network

    Kari, Lila

    -assembly. A systematic study of self-assembly as a computational process was initiated by Adleman1 , who studied the time of the construction of large squares via self-assembly. Rothemund and Winfree5 studied the self-assembly of squares. Besides a natural the- oretical interest, this study is motivated by the fact that triangular DNA tiles ha

  2. Peptide self-assembly triggered by metal ions.

    PubMed

    Zou, Rongfeng; Wang, Qi; Wu, Junchen; Wu, Jingxian; Schmuck, Carsten; Tian, He

    2015-08-01

    Through their unique and specific interactions with various metal ions, naturally occurring proteins control structures and functions of many biological processes and functions in organisms. Inspired by natural metallopeptides, chemists have developed artificial peptides which coordinate with metal ions through their functional groups either for introducing a special reactivity or for constructing nanostructures. However, the design of new coordination peptides requires a deep understanding of the structures, assembly properties, and dynamic behaviours of such peptides. This review briefly discusses strategies of peptide self-assembly induced by metal coordination to different natural and non-natural binding sites in the peptide. The structures and functions of the obtained aggregates are described as well. We also highlight some examples of a metal-induced peptide self-assembly with relevance to biotechnology applications. PMID:25952028

  3. Self-assembly of membrane junctions.

    PubMed Central

    Bruinsma, R; Goulian, M; Pincus, P

    1994-01-01

    We present a mechanism for the aggregation of mobile intermembrane junctions, such as the connexon dyad of gap junctions. The model demonstrates that intermembrane repulsion provides a powerful self-assembly pressure. If the membrane repulsion is strong enough to prevent membrane adhesion, then the self-assembly pressure is of effective infinite range. Images FIGURE 1 PMID:7948688

  4. Two-dimensional patterning of bacterial light-harvesting 2 complexes on lipid-modified gold surface

    NASA Astrophysics Data System (ADS)

    Yajima, Shunsuke; Furukawa, Rei A.; Nagata, Morio; Sakai, Shunsuke; Kondo, Masaharu; Iida, Kouji; Dewa, Takehisa; Nango, Mamoru

    2012-06-01

    In a photosynthetic membrane, nano-scale patterns of light-harvesting (LH) pigment-protein complexes play an essential role in capturing photons and ensuring efficient excitation energy transfer. LH complexes 1 and 2 have drawn attention as building blocks of a nano-scale photoelectric device. For obtaining a device with efficiency comparable to that of the natural photosynthesis, a method has to be established for forming a two-dimensional assembly of LH complexes around a metal electrode. In this study, LH2 complexes isolated from Rb. sphaeroides were immobilized on a patterned gold surface. Quenching of photo-excitation energy by gold was prevented through the placement of a self-assembled phospholipid monolayer between the LH2 complexes and the gold surface.

  5. Self-assembling materials for therapeutic delivery?

    PubMed Central

    Branco, Monica C.; Schneider, Joel P.

    2009-01-01

    A growing number of medications must be administered through parenteral delivery, i.e., intravenous, intramuscular, or subcutaneous injection, to ensure effectiveness of the therapeutic. For some therapeutics, the use of delivery vehicles in conjunction with this delivery mechanism can improve drug efficacy and patient compliance. Macromolecular self-assembly has been exploited recently to engineer materials for the encapsulation and controlled delivery of therapeutics. Self-assembled materials offer the advantages of conventional crosslinked materials normally used for release, but also provide the ability to tailor specific bulk material properties, such as release profiles, at the molecular level via monomer design. As a result, the design of materials from the “bottom up” approach has generated a variety of supramolecular devices for biomedical applications. This review provides an overview of self-assembling molecules, their resultant structures, and their use in therapeutic delivery. It highlights the current progress in the design of polymer- and peptide-based self-assembled materials. PMID:19010748

  6. From Solvolysis to Self-Assembly*

    PubMed Central

    Stang, Peter J.

    2009-01-01

    My sojourn from classical physical-organic chemistry and solvolysis to self-assembly and supramolecular chemistry, over the last forty years, is described. My contributions to unsaturated reactive intermediates, namely vinyl cations and unsaturated carbenes, along with my decade long involvement with polyvalent iodine chemistry, especially alkynyliodonium salts, as well as my more recent research with metal-ligand, coordination driven and directed self-assembly of finite supramolecular ensembles are discussed. PMID:19111062

  7. Directed Self-Assembly of Nanodispersions

    SciTech Connect

    Furst, Eric M [University of Delaware] [University of Delaware

    2013-11-15

    Directed self-assembly promises to be the technologically and economically optimal approach to industrial-scale nanotechnology, and will enable the realization of inexpensive, reproducible and active nanostructured materials with tailored photonic, transport and mechanical properties. These new nanomaterials will play a critical role in meeting the 21st century grand challenges of the US, including energy diversity and sustainability, national security and economic competitiveness. The goal of this work was to develop and fundamentally validate methods of directed selfassembly of nanomaterials and nanodispersion processing. The specific aims were: 1. Nanocolloid self-assembly and interactions in AC electric fields. In an effort to reduce the particle sizes used in AC electric field self-assembly to lengthscales, we propose detailed characterizations of field-driven structures and studies of the fundamental underlying particle interactions. We will utilize microscopy and light scattering to assess order-disorder transitions and self-assembled structures under a variety of field and physicochemical conditions. Optical trapping will be used to measure particle interactions. These experiments will be synergetic with calculations of the particle polarizability, enabling us to both validate interactions and predict the order-disorder transition for nanocolloids. 2. Assembly of anisotropic nanocolloids. Particle shape has profound effects on structure and flow behavior of dispersions, and greatly complicates their processing and self-assembly. The methods developed to study the self-assembled structures and underlying particle interactions for dispersions of isotropic nanocolloids will be extended to systems composed of anisotropic particles. This report reviews several key advances that have been made during this project, including, (1) advances in the measurement of particle polarization mechanisms underlying field-directed self-assembly, and (2) progress in the directed self-assembly of anisotropic nanoparticles and their unique physical properties.

  8. Lamellar Self-Assembly Nanostructured Magnetic Materials

    Microsoft Academic Search

    B. Hamdoun

    2004-01-01

    Synthesis of lamellar self-assemblies symmetric polystyrene–polybutylmethacrylate (PS–PBMA) copolymers, doped by magnetic nanoparticles was described. Self-assembly is a spontaneous process by which molecules and nanophase entities may materialize into organized aggregates or networks. As soon as particles are coated by a grafted PS layer, they can be confined in the PS layer of the polymeric smectic. The lamellar order was maintained

  9. Aluminum Nanoarrays for Plasmon-Enhanced Light Harvesting.

    PubMed

    Lee, Minah; Kim, Jong Uk; Lee, Ki Joong; Ahn, SooHoon; Shin, Yong-Beom; Shin, Jonghwa; Park, Chan Beum

    2015-06-23

    The practical limits of coinage-metal-based plasmonic materials demand sustainable, abundant alternatives with a wide plasmonic range of the solar energy spectrum. Aluminum (Al) is an emerging alternative, but its instability in aqueous environments critically limits its applicability to various light-harvesting systems. Here, we report a design strategy to achieve a robust platform for plasmon-enhanced light harvesting using Al nanostructures. The incorporation of mussel-inspired polydopamine nanolayers in the Al nanoarrays allowed for the reliable use of Al plasmonic resonances in a highly corrosive photocatalytic redox solution and provided nanoscale arrangement of organic photosensitizers on Al surfaces. The Al-photosensitizer core-shell assemblies exhibited plasmon-enhanced light absorption, which resulted in a 300% efficiency increase in photo-to-chemical conversion. Our strategy enables stable and advanced use of aluminum for plasmonic light harvesting. PMID:26046384

  10. Biomimetic Branched Hollow Fibers Templated by Self-assembled Fibrous Polyvinylpyrrolidone (PVP) Structures in Aqueous Solution

    PubMed Central

    Qiu, Penghe; Mao, Chuanbin

    2010-01-01

    Branched hollow fibers are common in nature, but to form artificial fibers with a similar branched hollow structure is still a challenge. We discovered that polyvinylpyrrolidone (PVP) could self-assemble into branched hollow fibers in an aqueous solution after aging the PVP solution for about two weeks. Based on this finding, we demonstrated two approaches by which the self-assembly of PVP into branched hollow fibers could be exploited to template the formation of branched hollow inorganic fibers. First, inorganic material such as silica with high affinity against the PVP could be deposited on the surface of the branched hollow PVP fibers to form branched hollow silica fibers. To extend the application of PVP self-assembly in templating the formation of hollow branched fibers, we then adopted a second approach where the PVP molecules bound to inorganic nanoparticles (using gold nanoparticles as a model) co-self-assemble with the free PVP molecules in an aqueous solution, resulting in the formation of the branched hollow fibers with the nanoparticles embedded in the PVP matrix constituting the walls of the fibers. Heating the resultant fibers above the glass transition temperature of PVP led to the formation of branched hollow gold fibers. Our work suggests that the self-assembly of the PVP molecules in the solution can serve as a general method for directing the formation of branched hollow inorganic fibers. The branched hollow fibers may find potential applications in microfluidics, artificial blood vessel generation, and tissue engineering. PMID:20158250

  11. Self-Assembling Behavior and Inhibition Effect of Dodecanethiol Self-Assembled Monolayers on Copper Surface

    NASA Astrophysics Data System (ADS)

    Zhang, Xiulan; Zhang, Heng; Yang, Yihong; Chen, Zhenyu

    2013-08-01

    The self-assembling behavior and inhibition effect of dodecanethiol self-assembled monolayers (SAMs) on copper surface were investigated by atomic force microscopy (AFM) and electrochemical methods. The assembling process was monitored by AFM phase images. The assembling time influences the corrosion protection efficiency of dodecanethiol SAMs. Surface friction significantly decreases when the copper surface is covered by SAMs.

  12. Automated Self-Assembly Programming Paradigm: Initial Investigations Lin Li, Natalio Krasnogor, Jon Garibaldi

    E-print Network

    Aickelin, Uwe

    Garibaldi ASAP Group, School of CS and IT, Univeristy of Nottingham {lxl,nxk,jmg}@cs.nott.ac.uk Abstract- tigations on the Automated Self-Assembly Programming Paradigm (ASAP2 ) is presented whereby software compo Paradigm (ASAP2 ) we have in mind is inspired by systems, both nat- ural and artificial, that exhibit self

  13. Structure and interactions in biomaterials based on membrane-biopolymer self-assembly

    Microsoft Academic Search

    Ilya Koltover

    1998-01-01

    Physical and chemical properties of artificial pure lipid membranes have been extensively studied during the last two decades and are relatively well understood. However, most real membrane systems of biological and biotechnological importance incorporate macromolecules either embedded into the membranes or absorbed onto their surfaces. We have investigated three classes of self-assembled membrane-biopolymer biomaterials: (i) Structure, interactions and stability of

  14. Carotenoid Cation Formation and the Regulation of Photosynthetic Light Harvesting

    Microsoft Academic Search

    Nancy E. Holt; Donatas Zigmantas; Leonas Valkunas; Xiao-Ping Li; Krishna K. Niyogi; Graham R. Fleming

    2005-01-01

    Photosynthetic light harvesting in excess light is regulated by a process known as feedback deexcitation. Femtosecond transient absorption measurements on thylakoid membranes show selective formation of a carotenoid radical cation upon excitation of chlorophyll under conditions of maximum, steady-state feedback deexcitation. Studies on transgenic Arabidopsis thaliana plants confirmed that this carotenoid radical cation formation is correlated with feedback deexcitation and

  15. Research article Translational regulation of light-harvesting complex expression

    E-print Network

    Durnford, Dion G.

    ,1-dimethylurea; H2O2, hydrogen peroxide; HL, High-Light; LHC, Light harvesting complex; LL, Low-Light; PSII dismutase (FeSOD), and through measurement of protein synthesis by in vivo labelling. Within two hours an increase in overall protein synthesis. After 4 hours HL exposure, however, a global disassembly

  16. Broadband Enhancement of Light Harvesting in a Luminescent Solar Concentrator

    Microsoft Academic Search

    Yun-Feng Xiao; Chang-Ling Zou; Yi-Wen Hu; Yan Li; Lixin Xiao; Fang-Wen Sun; Qihuang Gong

    2011-01-01

    Luminescent solar concentrators (LSCs) are large- area devices that absorb incident sunlight and emit lumines- cence photons with high quantum efficiency, which will finally be collected by a small photovoltaic (PV) system. The light- harvesting area of the PV system is much smaller than that of the LSC system, potentially reducing the cost of solar cells. Here, we present a

  17. Quantum entanglement phenomena in photosynthetic light harvesting complexes

    Microsoft Academic Search

    K. Birgitta Whaley; Mohan Sarovar; Akihito Ishizaki

    2010-01-01

    We review recent theoretical calculations of quantum entanglement in photosynthetic light harvesting complexes. These works establish, for the first time, a manifestation of this characteristically quantum mechanical phenomenon in biologically functional structures. We begin by summarizing calculations on model biomolecular systems that aim to reveal non-trivial characteristics of quantum entanglement in non-equilibrium biological environments. We then discuss and compare several

  18. Quantum entanglement phenomena in photosynthetic light harvesting complexes

    Microsoft Academic Search

    K. Birgitta Whaley; Mohan Sarovar; Akihito Ishizaki

    2011-01-01

    We review recent theoretical calculations of quantum entanglement in photosynthetic light harvesting complexes. These works establish, for the first time, a manifestation of this characteristically quantum mechanical phenomenon in biologically functional structures. We begin by summarizing calculations on model biomolecular systems that aim to reveal non-trivial characteristics of quantum entanglement in non-equilibrium biological environments. We then discuss and compare several

  19. Quantum superpositions in photosynthetic light harvesting: delocalization and entanglement

    Microsoft Academic Search

    Akihito Ishizaki; Graham R. Fleming

    2010-01-01

    We explore quantum entanglement among the chlorophyll molecules in light-harvesting complex II, which is the most abundant photosynthetic antenna complex in plants containing over 50% of the world's chlorophyll molecules. Our results demonstrate that there exists robust quantum entanglement under physiological conditions for the case of a single elementary excitation. However, this nonvanishing entanglement is not unexpected because entanglement in

  20. Programming biomolecular self-assembly pathways.

    PubMed

    Yin, Peng; Choi, Harry M T; Calvert, Colby R; Pierce, Niles A

    2008-01-17

    In nature, self-assembling and disassembling complexes of proteins and nucleic acids bound to a variety of ligands perform intricate and diverse dynamic functions. In contrast, attempts to rationally encode structure and function into synthetic amino acid and nucleic acid sequences have largely focused on engineering molecules that self-assemble into prescribed target structures, rather than on engineering transient system dynamics. To design systems that perform dynamic functions without human intervention, it is necessary to encode within the biopolymer sequences the reaction pathways by which self-assembly occurs. Nucleic acids show promise as a design medium for engineering dynamic functions, including catalytic hybridization, triggered self-assembly and molecular computation. Here, we program diverse molecular self-assembly and disassembly pathways using a 'reaction graph' abstraction to specify complementarity relationships between modular domains in a versatile DNA hairpin motif. Molecular programs are executed for a variety of dynamic functions: catalytic formation of branched junctions, autocatalytic duplex formation by a cross-catalytic circuit, nucleated dendritic growth of a binary molecular 'tree', and autonomous locomotion of a bipedal walker. PMID:18202654

  1. Associative memory through self-assembly

    NASA Astrophysics Data System (ADS)

    Zeravcic, Zorana

    2015-03-01

    Self-assembly has recently emerged as a powerful technique for synthesizing structures on the nano- and micro-scale. The basis of this development is the use of biopolymers, like DNA, to design specific interactions between multiple species of components, allowing the spontaneous assembly of complex structures. Here we address a fundamental limitation of the existing approaches to self-assembly: Namely, every target structure must have its own dedicated set of components, which are programmed to assemble only that very structure. In contrast, in biological systems, the same set of components can assemble many different complexes. Inspired by this, we extend the self-assembly framework to mixtures of shared components capable of assembling distinct structures at will.

  2. Theory of Programmable Hierarchic Self-Assembly

    NASA Astrophysics Data System (ADS)

    Tkachenko, Alexei V.

    2011-06-01

    We present a theoretical analysis of the inverse problem in self-assembly. A particular scheme is proposed for building an arbitrary desired nanostructure out of self-assembled building blocks (“octopus” nanoparticles). The conditions for robust self-assembly of the target structure are identified. This includes the minimal number of “colors” needed to encode interparticle bonds, which are to be implemented as pairs of complementary DNA sequences. As a part of this analysis, it is demonstrated that a floppy network with thermal fluctuations, in a certain range of coordination numbers ?Z?, possesses entropic rigidity and can be described as a traditional elastic solid. The onset of the entropic rigidity, ?Z?=d+1, determines the minimal number of bond types per particle needed to encode the desired structure. Thermodynamic considerations give additional conditions for the implementation of this scheme.

  3. Self-Assembly of Peptides to Nanostructures

    PubMed Central

    Mandal, Dindyal; Shirazi, Amir Nasrolahi; Parang, Keykavous

    2014-01-01

    The formation of well-ordered nanostructures through self-assembly of diverse organic and inorganic building blocks has drawn much attention owing to their potential applications in biology and chemistry. Among all organic building blocks, peptides are one of the most promising platforms due to their biocompatibility, chemical diversity, and resemblance with proteins. Inspired from the protein assembly in biological systems, various self-assembled peptide structures have been constructed using several amino acids and sequences. This review focuses on this emerging area, the recent advances in peptide self-assembly, and formation of different nanostructures, such as tubular, fibers, vesicles, spherical, and rod coil structures. While different peptide nanostructures are discovered, potential applications will be explored in drug delivery, tissue engineering, wound healing, and surfactants. PMID:24756480

  4. Computing by molecular self-assembly

    PubMed Central

    Jonoska, Nataša; Seeman, Nadrian C.

    2012-01-01

    The paper reviews two computing models by DNA self-assembly whose proof of principal have recently been experimentally confirmed. The first model incorporates DNA nano-devices and triple crossover DNA molecules to algorithmically arrange non-DNA species. This is achieved by simulating a finite-state automaton with output where golden nanoparticles are assembled to read-out the result. In the second model, a complex DNA molecule representing a graph emerges as a solution of a computational problem. This supports the idea that in molecular self-assembly computing, it may be necessary to develop the notion of shape processing besides the classical approach through symbol processing. PMID:23919130

  5. Amyloid character of self-assembling proteins based on adenovirus fiber shaft sequences

    Microsoft Academic Search

    Haris Retsos; Katerina Papanikolopoulou; Claude Filippini; Christian Riekel; Kenncorwin H. Gardner; V. Trevor Forsyth; Anna Mitraki

    2005-01-01

    Fibrous proteins found in natural materials such as silk fibroins, spider silks, and viral spikes increasingly serve as a\\u000a source of inspiration for the design of novel, artificial fibrous materials. The fiber protein from the adenovirus has previously\\u000a served as a model for the design of artificial, self-assembling fibers. The fibrous shaft of this protein consists of 15-amino-acid\\u000a sequence repeats

  6. Early events in the biosynthesis and assembly of the cyanobacterial light-harvesting system

    NASA Astrophysics Data System (ADS)

    Anderson, Lamont

    1996-02-01

    The cyanobacteria are photosynthetic procaryotes that employ a mechanism of photosynthesis which is essentially identical to the systems found in plant chloroplasts and the eukaryotic green algae. Cyanobacteria can drive photosynthesis with light energy from a broad region of the visible spectrum (500 - 650 nm wavelength) that is not available to plants and green algae, which are limited to the narrow band of light energy that is absorbed by chlorophyll (660-680 nm). The light-harvesting capacity of the cyanobacteria is a function of a complex protein structure that resides on the surface of the photosynthetic membrane in contact with the PSII chlorophyll reaction centers. This light-harvesting complex is called a phycobilisome and functions as a protein scaffold for a rigid array of chromophores that absorbs light energy and transfers it to chlorophyll. The chromophores are linear tetrapyrroles (the bilins) that are covalently attached to the biliproteins, which comprise 80 - 85% of the total phycobilisome mass. There are three major classes of spectrally distinct biliproteins [phycoerythrin (PE), (lambda) max equals 565 nm; phycocyanin (PC), (lambda) max equals 617 nm; and allophycocyanin (AP), (lambda) max equals 650 nm] and their spatial organization within the phycobilisome creates an array of donor and acceptor chromophores that is optimized for resonance energy transfer to chlorophyll on a picosecond timescale and at close to 100% efficiency. The cyanobacteria can exert control over the biliprotein composition of the phycobilisomes in response to both light quality and light quantity, and they do so primarily by light-responsive transcription control mechanisms. The biosynthesis and assembly of a phycobilisome is an interesting example of self-assembly in a complex protein system. A phycobilisome from Synechocystis sp. strain 6701 can contain 400 proteins derived from a repertoire of 16 different polypeptides that includes the (alpha) and (beta) subunits for each major biliprotein and the achromic linker proteins that mediate assembly throughout the structure. The biliprotein subunit structures all show an identical motif that is reflected by significant amino acid sequence similarities across the different classes. Since phycobilisomes can comprise up to 40% of the cyanobacterial dry mass, assembly of these complexes must occur in the presence of high localized concentrations of components that are very similar in structure. That phycobilisome assembly is an efficient process with no evidence of significant misassembly suggests that effective molecular recognition during phycobilisome biosynthesis is based upon the subtle differences between subunits of different class biliproteins. We are using a protein engineering approach to examine structural features that mediate molecular recognition in two of the earliest steps of phycobilisome assembly, the docking of (alpha) and (beta) subunits and the selective attachment of chromophores.

  7. Separating annihilation and excitation energy transfer dynamics in light harvesting systems.

    PubMed

    Vengris, Mikas; Larsen, Delmar S; Valkunas, Leonas; Kodis, Gerdenis; Herrero, Christian; Gust, Devens; Moore, Thomas; Moore, Ana; van Grondelle, Rienk

    2013-09-26

    The dependence of excitation energy transfer kinetics on the electronic state of the acceptor (ground vs excited) has been resolved with a novel multipulse prePump-Pump-Probe spectroscopy. The primary energy transfer and annihilation dynamics in two model light-harvesting systems were explored: an artificially synthesized carotenoid-zinc-phthalocyanine dyad and a naturally occurring light-harvesting peridinin-chlorophyll protein complex from Amphidinium carterae. Both systems use carotenoid as the primary excitation energy donor with porphyrin chromophores as the acceptor molecules. The prePump-Pump-Probe transient signals were analyzed with Monte Carlo modeling to explicitly address the underlying step-by-step kinetics involved in both excitation migration and annihilation processes. Both energy transfer and annihilation dynamics were demonstrated to occur with approximately the same rate in both systems, regardless of the excitation status of the acceptor pigments. The possible reasons for these observations are discussed in the framework of the Förster energy transfer model. PMID:23662680

  8. Self-assembled Monolayer Films: Microcontact Printing

    E-print Network

    Prentiss, Mara

    Self-assembled Monolayer Films: Microcontact Printing , Microcontact printing (PCP), one of the non to generate two-dimensional patterns by print- * ing the molecules of an "ink" onto the surface of a solid(dimethylsiloxane) (PDMS), the "ink" is an alkanethiol, and the substrate on which the printing occurs is a thin

  9. Inverse Problem in Self-assembly

    NASA Astrophysics Data System (ADS)

    Tkachenko, Alexei

    2012-02-01

    By decorating colloids and nanoparticles with DNA, one can introduce highly selective key-lock interactions between them. This leads to a new class of systems and problems in soft condensed matter physics. In particular, this opens a possibility to solve inverse problem in self-assembly: how to build an arbitrary desired structure with the bottom-up approach? I will present a theoretical and computational analysis of the hierarchical strategy in attacking this problem. It involves self-assembly of particular building blocks (``octopus particles''), that in turn would assemble into the target structure. On a conceptual level, our approach combines elements of three different brands of programmable self assembly: DNA nanotechnology, nanoparticle-DNA assemblies and patchy colloids. I will discuss the general design principles, theoretical and practical limitations of this approach, and illustrate them with our simulation results. Our crucial result is that not only it is possible to design a system that has a given nanostructure as a ground state, but one can also program and optimize the kinetic pathway for its self-assembly.

  10. Molecular Dynamics in Self-Assembled Monolayers

    Microsoft Academic Search

    Jason Bochinski; Derrick Stevens; Mary Scott; Laura Guy; Casey Dedeugd; Laura Clarke

    2007-01-01

    Silane self-assembled monolayers (SAMs) are an important tool for both scientific research and technological applications. Despite their widespread use, few experimental investigations have addressed molecular motion within these films, which offer a unique and useful physical system for fundamental scientific studies, such as observing dipolar and other glass transitions in two-dimensions. In addition, relaxations such as ``rotator'' phases where molecular

  11. Molecular self-assembly: Searching sequence space

    NASA Astrophysics Data System (ADS)

    Gazit, Ehud

    2015-01-01

    Short peptides are among the most intriguing building blocks in nanotechnology, but it would be very challenging to experimentally study the properties of large numbers of different sequences. Now, a computational analysis of all 8,000 possible tripeptides has been used to identify those with interesting self-assembly behaviour.

  12. Self-assembled thin film chemical sensors

    SciTech Connect

    Swanson, B.; Li, DeQuan

    1996-11-01

    This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Current chemical sensors suffer from poor molecular specificity, sensitivity, and stability and seldom have the recovery properties needed for real-time monitoring applications. We have employed self-assembly techniques to covalently bond species- selective reagents directly to the surface of the transducer so that analyte/reagent chemistry occurs at the interface between the transducer and the media to be monitored. The use of self-assembling monolayer and -multilayer (SAM) techniques results in stable sensing elements with optimal specificity built in through the use of reagents that have been designed for molecular recognition. Moreover, self-assembly chemistry applied to oxide surfaces allows flexible means of transduction spanning optical, electrochemical, mass-loading, and conduction methods. The work conducted on this project focused on demonstration of the methodology and the application to selected organic vapors (aromatic compounds and halogenated hydrocarbons). We have been able to develop a series of surface acoustic wave (SAW) sensors that are specific for aromatic compounds and halogenated hydrocarbons based on self-assembled thin films of cyclodextrins and calixarenes. Monolayers of seven different cyclodextrins and clixarenes have been attached to SAW transducers and their response to several organic molecules in the vapor phase have been measured. This preliminary data confirms the efficacy of this approach for real- time monitoring of hydrocarbons.

  13. Templated self-assembly of sub-10 nm quantum dots

    E-print Network

    Leu, Joshua C. (Joshua Chung)

    2008-01-01

    Patterned templates can guide the self-assembly of nanoparticles into ordered arrays. Our motivation in pursuing templated self-assembly is to develop a robust method for the creation of ordered structures at length scales ...

  14. Light-harvesting function of beta -carotene inside carbon nanotubes

    Microsoft Academic Search

    Kazuhiro Yanagi; Konstantin Iakoubovskii; Said Kazaoui; Nobutsugu Minami; Yutaka Maniwa; Yasumitsu Miyata; Hiromichi Kataura

    2006-01-01

    Single-wall carbon nanotubes (SWCNTs) are attractive components for nanoscale electronics, however their optoelectronic properties have been limited by the optical characteristics of semiconducting SWCNTs. To enhance the functionalities of SWCNTs, beta -carotene was encapsulated in SWCNTs and its light-harvesting function was investigated. The detailed structure of encapsulated beta -carotene was clarified using x-ray diffraction and the polarization dependence of the

  15. Light Harvesting by Lamellar Chromatophores in Rhodospirillum photometricum

    PubMed Central

    Chandler, Danielle E.; Strümpfer, Johan; Sener, Melih; Scheuring, Simon; Schulten, Klaus

    2014-01-01

    Purple photosynthetic bacteria harvest light using pigment-protein complexes which are often arranged in pseudo-organelles called chromatophores. A model of a chromatophore from Rhodospirillum photometricum was constructed based on atomic force microscopy data. Molecular-dynamics simulations and quantum-dynamics calculations were performed to characterize the intercomplex excitation transfer network and explore the interplay between close-packing and light-harvesting efficiency. PMID:24896130

  16. Optical Spectroscopy of Individual Light-Harvesting Complexes

    Microsoft Academic Search

    Thijs J. Aartsma; Jürgen Köhler

    In this contribution we present an overview of the results of detailed spectroscopic investigations of individual light-harvesting\\u000a complexes of photosynthetic purple bacteria at 1.2 K. By applying single-molecule detection techniques the properties of the\\u000a electronically excited states of the assemblies of bacteriochlorophyll a (BChl a) pigment molecules in the individual complexes are revealed, without ensemble averaging. The results show that

  17. Self-assembled nanolaminate coatings (SV)

    SciTech Connect

    Fan, H.

    2012-03-01

    Sandia National Laboratories (Sandia) and Lockheed Martin Aeronautics (LM Aero) are collaborating to develop affordable, self-assembled, nanocomposite coatings and associated fabrication processes that will be tailored to Lockheed Martin product requirements. The purpose of this project is to develop a family of self-assembled coatings with properties tailored to specific performance requirements, such as antireflective (AR) optics, using Sandia-developed self-assembled techniques. The project met its objectives by development of a simple and economic self-assembly processes to fabricate multifunctional coatings. Specifically, materials, functionalization methods, and associated coating processes for single layer and multiple layers coatings have been developed to accomplish high reflective coatings, hydrophobic coatings, and anti-reflective coatings. Associated modeling and simulations have been developed to guide the coating designs for optimum optical performance. The accomplishments result in significant advantages of reduced costs, increased manufacturing freedom/producibility, improved logistics, and the incorporation of new technology solutions not possible with conventional technologies. These self-assembled coatings with tailored properties will significantly address LMC's needs and give LMC a significant competitive lead in new engineered materials. This work complements SNL's LDRD and BES programs aimed at developing multifunctional nanomaterials for microelectronics and optics as well as structure/property investigations of self-assembled nanomaterials. In addition, this project will provide SNL with new opportunities to develop and apply self-assembled nanocomposite optical coatings for use in the wavelength ranges of 3-5 and 8-12 micrometers, ranges of vital importance to military-based sensors and weapons. The SANC technologies will be applied to multiple programs within the LM Company including the F-35, F-22, ADP (Future Strike Bomber, UAV, UCAV, etc.). The SANC technologies will establish LMA and related US manufacturing capability for commercial and military applications therefore reducing reliance on off-shore development and production of related critical technologies. If these technologies are successfully licensed, production of these coatings in manufactory will create significant technical employment opportunities.

  18. Molecular Self-assembly for Organic Electronics

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Kaur, Irvinder; Diaconescu, Bogdan; Jazdzyk, Mikael; Miller, Glen P.; Pohl, Karsten

    2009-10-01

    Self-assembled thin films of novel organic molecules hold the promise of emerging technologies and applications ranging from sensors for biological applications to organic electronics and more efficient organic photovoltaics. Self-assembled monolayers (SAMs) form as a result of a delicate balance between competing molecule-substrate and intermolecular interactions. To control such self-assembly processes, it is mandatory to understand how this balance reflects onto the SAM's final structure. Here we present an ultra-high vacuum scanning tunneling microscopy (STM) study of the self-assembly of novel pentacene derivatives and functionalized fullerenes (F-C60) on metal surfaces. Pentacene is known to exhibit large carrier mobility and has been studied extensively as a semiconductor in organic thin film devices. However, it is subject to facile photo-oxidation that limits device lifetime. We recently synthesized novel pentacene derivatives that show a dramatically increased resistance to photo-oxidation. We identified 6,13-dichloropentacene as a promising candidate for organic electronics. On the compact surface of gold, 6,13-dichloropentacene forms self-assembled domains with various high symmetry orientations. The quality of the SAM is seem to dramatically improve when the 6,13-dichloropentacene are deposited on the (788) vicinal surface of gold where the presence of parallel atomic steps will select only one of the possible SAM orientations due to the molecule-step interaction. Thus we observe the formation of very large self-assembled 6,13-dichloropentacene monolayers with perfect single domain orientation. We have also studied the self-assembly of C60 functionalized with alkyl chains of various lengths (F-C60) on Ag(111). We find that as a function of the alkyl chain length various structures are forming, ranging from zigzag like to linear arrays of C60 fullerene cages. The symmetry and unit cell size of the F-C60 SAMs is dictated by the alkyl-surface and the intermolecular interactions. These results show that C60 molecules can be assembled in 2D and non-compact molecular arrays with a surface density controllable via appropriate chemical functionalization. Those structures show promise as candidates for selfassembled molecular junctions.

  19. Amphipols and photosynthetic light-harvesting pigment-protein complexes.

    PubMed

    Opa?i?, Milena; Durand, Grégory; Bosco, Michael; Polidori, Ange; Popot, Jean-Luc

    2014-10-01

    The trimeric light-harvesting complexes II (LHCII) of plants and green algae are pigment-protein complexes involved in light harvesting and photoprotection. Different conformational states have been proposed to be responsible for their different functions. At present, detergent-solubilized LHCII is used as a model for the "light-harvesting conformation", whereas the "quenched conformation" is mimicked by LHCII aggregates. However, none of these conditions seem to perfectly reproduce the properties of LHCII in vivo. In addition, several monomeric LHC complexes are not fully stable in detergent. There is thus a need to find conditions that allow analyzing LHCs in vitro in stable and, hopefully, more native-like conformations. Here, we report a study of LHCII, the major antenna complex of plants, in complex with amphipols. We have trapped trimeric LHCII and monomeric Lhcb1 with either polyanionic or non-ionic amphipols and studied the effect of these polymers on the properties of the complexes. We show that, as compared to detergent solutions, amphipols have a stabilizing effect on LHCII. We also show that the average fluorescence lifetime of LHCII trapped in an anionic amphipol is ~30% shorter than in ?-dodecylmaltoside, due to the presence of a conformation with 230-ps lifetime that is not present in detergent solutions. PMID:25107304

  20. Self-assembling membranes and related methods thereof

    DOEpatents

    Capito, Ramille M; Azevedo, Helena S; Stupp, Samuel L

    2013-08-20

    The present invention relates to self-assembling membranes. In particular, the present invention provides self-assembling membranes configured for securing and/or delivering bioactive agents. In some embodiments, the self-assembling membranes are used in the treatment of diseases, and related methods (e.g., diagnostic methods, research methods, drug screening).

  1. MULTI-BATCH SELF-ASSEMBLY FOR MICROSYSTEM INTEGRATION

    E-print Network

    by adsorption of an alkanethiolate self-assembled monolayer (SAM), while they can be deMULTI-BATCH SELF-ASSEMBLY FOR MICROSYSTEM INTEGRATION Xiaorong Xiong*, Yael Hanein*, Jiandong Fang describe a parts-to-substrate self-assembly approach driven by surface tension. To perform assembly

  2. Electrochemical impedance sensing of DNA at PNA self assembled monolayer

    E-print Network

    Kwak, Juhyoun

    Electrochemical impedance sensing of DNA at PNA self assembled monolayer Tesfaye Hailu Degefa and the mismatch can be discriminated effectively at PNA self assembled monolayers (SAMs). Therefore, this work can 2007 Elsevier B.V. All rights reserved. Keywords: Peptide nucleic acid; Self assembled monolayers; DNA

  3. Self-Assembled Monolayers DOI: 10.1002/anie.200703642

    E-print Network

    Prentiss, Mara

    Self-Assembled Monolayers DOI: 10.1002/anie.200703642 Eutectic Gallium­Indium (EGaIn): A Moldable Liquid Metal for Electrical Characterization of Self-Assembled Monolayers** Ryan C. Chiechi, Emily A, 25% In by weight, m.p. = 15.58C),[1] and their use in studying charge transport across self-assembled

  4. Kinetically driven self assembly of highly ordered nanoparticle monolayers

    E-print Network

    Jaeger, Heinrich M.

    LETTERS Kinetically driven self assembly of highly ordered nanoparticle monolayers TERRY P. BIGIONI islands nucleate and grow. This self-assembly mechanism produces monolayers with exceptional long directly observed this monolayer self-assembly process under the highly non-equilibrium conditions

  5. Microcontact Printing of Proteins on Mixed Self-Assembled Monolayers

    E-print Network

    Chen, Christopher S.

    Microcontact Printing of Proteins on Mixed Self-Assembled Monolayers John L. Tan, Joe Tien consisted of two-component, mixed self-assembled monolayers (SAMs) of alkanethiols on gold presenting -CH3-OHgroups.InµCPofproteins,itisunclearwhatcauses proteinadsorbedonastamptotransferorwhythisprocess is successful only on certain surfaces. In this study, we printed proteins onto two-component self-assembled

  6. Patterning Multiple Aligned Self-Assembled Monolayers Using Light

    E-print Network

    Prentiss, Mara

    Patterning Multiple Aligned Self-Assembled Monolayers Using Light Declan Ryan, Babak Amir Parviz, aligned self-assembled monolayers (SAMs) using light at different wavelengths. It describes the synthesis describes a method for patterning a gold substrate with three aligned regions of self-assembled monolayers

  7. Correspondence Analysis of Self-Assembled Monolayers on Gold

    E-print Network

    Nesnas, Nasri

    Correspondence Analysis of Self-Assembled Monolayers on Gold Surfaces Using Direct Analysis in Real of chemical species in self- assembled monolayers. The ability to modify certain surfaces with a single layer the formation of self- assembled monolayers (SAMs) on gold surfaces from thiols. Lines of inquiry in SAMs on Au

  8. Poly(ethylene glycol) Self-Assembled Monolayer Island Growth

    E-print Network

    Haviland, David

    Poly(ethylene glycol) Self-Assembled Monolayer Island Growth Jonas Rundqvist, Jan H. Hoh, and David modified with self-assembled monolayers (SAMs) of oligo- (ethylene glycol) (OEG) or PEG can have excellent: January 3, 2005 Here, we report a study of the morphology and growth dynamics of a self-assembled

  9. Manipulating Excited-State Dynamics of Individual Light-Harvesting Chromophores through Restricted Motions in a Hydrated Nanoscale Protein Cavity.

    PubMed

    Noriega, Rodrigo; Finley, Daniel T; Haberstroh, John; Geissler, Phillip L; Francis, Matthew B; Ginsberg, Naomi S

    2015-06-11

    Manipulating the photophysical properties of light-absorbing units is a crucial element in the design of biomimetic light-harvesting systems. Using a highly tunable synthetic platform combined with transient absorption and time-resolved fluorescence measurements and molecular dynamics simulations, we interrogate isolated chromophores covalently linked to different positions in the interior of the hydrated nanoscale cavity of a supramolecular protein assembly. We find that, following photoexcitation, the time scales over which these chromophores are solvated, undergo conformational rearrangements, and return to the ground state are highly sensitive to their position within this cavity and are significantly slower than in a bulk aqueous solution. Molecular dynamics simulations reveal the hindered translations and rotations of water molecules within the protein cavity with spatial specificity. The results presented herein show that fully hydrated nanoscale protein cavities are a promising way to mimic the tight protein pockets found in natural light-harvesting complexes. We also show that the interplay between protein, solvent, and chromophores can be used to substantially tune the relaxation processes within artificial light-harvesting assemblies in order to significantly improve the yield of interchromophore energy transfer and extend the range of excitation transport. Our observations have implications for other important, similarly sized bioinspired materials, such as nanoreactors and biocompatible targeted delivery agents. PMID:26035585

  10. Self-assembly of Fmoc-diphenylalanine inside liquid marbles.

    PubMed

    Braun, Hans-Georg; Cardoso, André Zamith

    2012-09-01

    Liquid marbles made from Lycopodium clavatum spores are used to encapsulate aqueous solutions of 9-fluorenylmethoxycarbonyl-diphenylalanine (Fmoc-FF). Acidification of the Fmoc-FF solution at the liquid/air interface of the liquid marble triggers the self-assembly of ribbon-like peptide fibrils into an ultrathin peptide membrane (50-500 nm). The membrane incorporates the lycopodium microparticles and as a result stabilizes the liquid marble against collapse, that could otherwise occur through particle disintegration at the floating interphase. Ultrathin nanostructured peptide membrane formation at the liquid/air interface is also observed within artificial microstructured floating objects. Thus, peptide membranes formed were inspected by SEM and TEM. Electron diffraction data reveal information about the molecular organization inside the oligopeptide membranes. PMID:22584262

  11. Self-assembled tunable photonic hyper-crystals

    PubMed Central

    Smolyaninova, Vera N.; Yost, Bradley; Lahneman, David; Narimanov, Evgenii E.; Smolyaninov, Igor I.

    2014-01-01

    We demonstrate a novel artificial optical material, the “photonic hyper-crystal”, which combines the most interesting features of hyperbolic metamaterials and photonic crystals. Similar to hyperbolic metamaterials, photonic hyper-crystals exhibit broadband divergence in their photonic density of states due to the lack of usual diffraction limit on the photon wave vector. On the other hand, similar to photonic crystals, hyperbolic dispersion law of extraordinary photons is modulated by forbidden gaps near the boundaries of photonic Brillouin zones. Three dimensional self-assembly of photonic hyper-crystals has been achieved by application of external magnetic field to a cobalt nanoparticle-based ferrofluid. Unique spectral properties of photonic hyper-crystals lead to extreme sensitivity of the material to monolayer coatings of cobalt nanoparticles, which should find numerous applications in biological and chemical sensing. PMID:25027947

  12. Self-assembled Oniontype Multiferroic Nanostructures

    NASA Astrophysics Data System (ADS)

    Ren, Shenqiang; Briber, Robert M.; Wuttig, Manfred

    2009-03-01

    Spontaneously self-assembled oniontype multiferroic nanostructures based on block copolymers as templating materials are reported. Diblock copolymer containing two different magnetoelectric precursors separately segregated to the two microdomains have been shown to form well-ordered templated lamellar structures. Onion-type multilamellar ordered multiferroic (PZT/CoFe2O4) nanostructures have been induced by room temperature solvent annealing in a magnetic field oriented perpendicular to the plane of the film. The evolution of the onion-like microstructure has been characterized by AFM, MFM, and TEM. The structure retains lamellar periodicity observed at zero field. The onion structure is superparamagnetic above and antiferromagnetic below the blocking temperature. This templating process opens a route for nanometer-scale patterning of magnetic toroids by means of self-assembly on length scales that are difficult to obtain by standard lithography techniques.

  13. Algorithmic Self-Assembly DNA (Layered

    E-print Network

    Hagiya, Masami

    DNA DNA Algorithmic Self-Assembly DNA DNA DNA DNA DNA 2 DNA (Layered Tile Model) [1] LTM Fig.1-Origami 4 DNA (Fig.1) DNA Fig.2 [2] DNA DNA Fig. 2 DNA ( ( ), SEM )) DNA DNA DNA DNA DNA DNA DNA RecA 1 DNA 2 DNA ATP DNA 3 DNA (Fig. ) DNA DNA DNA RecA 1 DNA 3 #12;Fig. 4 AFM image of triple strand DNA

  14. Anisotropic Self-Assembly of Nanoparticle Amphiphiles

    NASA Astrophysics Data System (ADS)

    Kumar, Sanat

    2009-03-01

    It is easy to understand the self-assembly of particles having anisotropic shapes or interactions, such as Co nanoparticles or proteins, into highly extended structures. However, there is no experimentally established strategy for creating anisotropic structures from common spherical nanoparticles. We demonstrate that spherical nanoparticles, uniformly grafted with macromolecules, robustly self-assemble into a range of anisotropic superstructures when they are dispersed in the corresponding homopolymer matrix. This phenomenon is driven by the microphase separation between the inorganic nanoparticles and the (organic) polymeric chains grafted to their surfaces in a fashion similar to block copolymers. This microphase separation driven particle self-assembly provides a unique means of controlling the global nanoparticle dispersion state in polymer nanocomposites. The relationship between the state of particle dispersion and nanocomposite properties can thus be critically examined, and in particular we focus on the mechanical reinforcement afforded when particles are added to polymers. Grafted nanoparticles are thus versatile building blocks for creating tunable and functional particle superstructures with significant practical applications. With Pinar Akcora, Hongjun Liu, Yu Li, Brian Benicewicz, Linda Schadler, Thanos Panagiotopoulos, Jack Douglas, P. Thiyagarajan and Ralph Colby.

  15. Self-Assembly of Nanoparticle Surfactants

    NASA Astrophysics Data System (ADS)

    Lombardo, Michael T.

    Self-assembly utilizes non-covalent forces to organize smaller building blocks into larger, organized structures. Nanoparticles are one type of building block and have gained interest recently due to their unique optical and electrical properties which have proved useful in fields such as energy, catalysis, and advanced materials. There are several techniques currently used to self-assemble nanoparticles, each with its own set of benefits and drawbacks. Here, we address the limited number of techniques in non-polar solvents by introducing a method utilizing amphiphilic gold nanoparticles. Grafted polymer chains provide steric stabilization while small hydrophilic molecules induce assembly through short range attractive forces. The properties of these self-assembled structures are found to be dependent on the polymer and small molecules surface concentrations and chemistries. These particles act as nanoparticle surfactants and can effectively stabilize oil-water interfaces, such as in an emulsion. In addition to the work in organic solvent, similar amphiphilic particles in aqueous media are shown to effectively stabilize oil-in-water emulsions that show promise as photoacoustic/ultrasound theranostic agents.

  16. Formal Verification of Self-Assembling Systems

    E-print Network

    Sterling, Aaron

    2010-01-01

    This paper introduces the theory and practice of formal verification of self-assembling systems. We interpret a well-studied abstraction of nanomolecular self assembly, the Abstract Tile Assembly Model (aTAM), into Computation Tree Logic (CTL), a temporal logic often used in model checking. We then consider the class of "rectilinear" tile assembly systems. This class includes most aTAM systems studied in the theoretical literature, and all (algorithmic) DNA tile self-assembling systems that have been realized in laboratories to date. We present a polynomial-time algorithm that, given a tile assembly system T as input, either provides a counterexample to T's rectilinearity or verifies whether T has a unique terminal assembly. Using partial order reductions, the verification search space for this algorithm is reduced from exponential size to O(n^2), where n x n is the size of the assembly surface. That reduction is asymptotically the best possible. We report on experimental results obtained by translating tile ...

  17. Molecular factors controlling photosynthetic light harvesting by carotenoids.

    PubMed

    Polívka, Tomás; Frank, Harry A

    2010-08-17

    Carotenoids are naturally occurring pigments that absorb light in the spectral region in which the sun irradiates maximally. These molecules transfer this energy to chlorophylls, initiating the primary photochemical events of photosynthesis. Carotenoids also regulate the flow of energy within the photosynthetic apparatus and protect it from photoinduced damage caused by excess light absorption. To carry out these functions in nature, carotenoids are bound in discrete pigment-protein complexes in the proximity of chlorophylls. A few three-dimensional structures of these carotenoid complexes have been determined by X-ray crystallography. Thus, the stage is set for attempting to correlate the structural information with the spectroscopic properties of carotenoids to understand the molecular mechanism(s) of their function in photosynthetic systems. In this Account, we summarize current spectroscopic data describing the excited state energies and ultrafast dynamics of purified carotenoids in solution and bound in light-harvesting complexes from purple bacteria, marine algae, and green plants. Many of these complexes can be modified using mutagenesis or pigment exchange which facilitates the elucidation of correlations between structure and function. We describe the structural and electronic factors controlling the function of carotenoids as energy donors. We also discuss unresolved issues related to the nature of spectroscopically dark excited states, which could play a role in light harvesting. To illustrate the interplay between structural determinations and spectroscopic investigations that exemplifies work in the field, we describe the spectroscopic properties of four light-harvesting complexes whose structures have been determined to atomic resolution. The first, the LH2 complex from the purple bacterium Rhodopseudomonas acidophila, contains the carotenoid rhodopin glucoside. The second is the LHCII trimeric complex from higher plants which uses the carotenoids lutein, neoxanthin, and violaxanthin to transfer energy to chlorophyll. The third, the peridinin-chlorophyll-protein (PCP) from the dinoflagellate Amphidinium carterae, is the only known complex in which the bound carotenoid (peridinin) pigments outnumber the chlorophylls. The last is xanthorhodopsin from the eubacterium Salinibacter ruber. This complex contains the carotenoid salinixanthin, which transfers energy to a retinal chromophore. The carotenoids in these pigment-protein complexes transfer energy with high efficiency by optimizing both the distance and orientation of the carotenoid donor and chlorophyll acceptor molecules. Importantly, the versatility and robustness of carotenoids in these light-harvesting pigment-protein complexes have led to their incorporation in the design and synthesis of nanoscale antenna systems. In these bioinspired systems, researchers are seeking to improve the light capture and use of energy from the solar emission spectrum. PMID:20446691

  18. Carotenoid Cation Formation and the Regulation of Photosynthetic Light Harvesting

    NASA Astrophysics Data System (ADS)

    Holt, Nancy E.; Zigmantas, Donatas; Valkunas, Leonas; Li, Xiao-Ping; Niyogi, Krishna K.; Fleming, Graham R.

    2005-01-01

    Photosynthetic light harvesting in excess light is regulated by a process known as feedback deexcitation. Femtosecond transient absorption measurements on thylakoid membranes show selective formation of a carotenoid radical cation upon excitation of chlorophyll under conditions of maximum, steady-state feedback deexcitation. Studies on transgenic Arabidopsis thaliana plants confirmed that this carotenoid radical cation formation is correlated with feedback deexcitation and requires the presence of zeaxanthin, the specific carotenoid synthesized during high light exposure. These results indicate that energy transfer from chlorophyll molecules to a chlorophyll-zeaxanthin heterodimer, which then undergoes charge separation, is the mechanism for excess energy dissipation during feedback deexcitation.

  19. Molecular Factors Controlling Photosynthetic Light-Harvesting by Carotenoids

    PubMed Central

    Polívka, Tomáš; Frank, Harry A.

    2010-01-01

    Carotenoids are naturally-occurring pigments that absorb light in the spectral region in which the sun irradiates maximally. These molecules transfer this energy to chlorophylls, initiating the primary photochemical events of photosynthesis. Carotenoids also regulate the flow of energy within the photosynthetic apparatus and protect it from photo-induced damage caused by excess light absorption. To carry out these functions in nature, carotenoids are bound in discrete pigment-protein complexes in close proximity to chlorophylls. A few 3D structures of these carotenoid complexes have been determined by X-ray crystallography. Thus, the stage is set for attempting to correlate the structural information with the spectroscopic properties of carotenoids to understand the molecular mechanism(s) of their function in photosynthetic systems. In this Account, we summarize current spectroscopic data describing the excited state energies and ultrafast dynamics of purified carotenoids in solution and bound in light-harvesting complexes from purple bacteria, marine algae, and green plants. Many of these complexes can be modified using mutagenesis or pigment exchange which facilitates making the correlations between structure and function. We describe the structural and electronic factors controlling the function of carotenoids as energy donors. We also discuss unresolved issues related to the nature of spectroscopically dark excited states, which could play a role in light-harvesting. To illustrate the interplay between structural determinations and spectroscopic investigations that exemplifies work in the field, we describe the spectroscopic properties of four light-harvesting complexes whose structures have been determined to atomic resolution. The first, the LH2 complex from the purple bacterium Rhodopseudomonas acidophila, contains the carotenoid, rhodopin glucoside. The second is the LHCII trimeric complex from higher plants which uses the carotenoids, lutein, neoxanthin and violaxanthin to transfer energy to chlorophyll. The third, the peridinin-chlorophyll-protein (PCP) from the dinoflagellate, Amphidinium carterae, is the only known complex where the bound carotenoid (peridinin) pigments outnumber the chlorophylls. The last is xanthorhodopsin from the eubacterium, Salinibacter ruber. This complex contains the carotenoid, salinixanthin, which transfers energy to a retinal chromophore. The carotenoids in these pigment-protein complexes transfer energy with high efficiency by optimizing both the distance and orientation of the carotenoid donor and chlorophyll acceptor molecules. Importantly, the versatility and robustness of carotenoids in these light-harvesting pigment-protein complexes have led to their incorporation in the design and synthesis of nanoscale antenna systems. In these bio-inspired systems, researchers are seeking to improve the light capture and use of energy from the solar emission spectrum. PMID:20446691

  20. Integrated Nanosystems Templated by Self-assembled Virus Capsids

    NASA Astrophysics Data System (ADS)

    Stephanopoulos, Nicholas

    This dissertation presents the synthesis and modeling of multicomponent nanosystems templated by self-assembled virus capsids. The design principles, synthesis, analysis, and future directions for these capsid-based materials are presented. Chapter 1 gives an overview of the literature on the application of virus capsids in constructing nanomaterials. The uses of capsids in three main areas are considered: (1) as templates for inorganic materials or nanoparticles; (2) as vehicles for biological applications like medical imaging and treatment; and (3) as scaffolds for catalytic materials. In light of this introduction, an overview of the material in this dissertation is described. Chapters 2-4 all describe integrated nanosystems templated by bacteriophage MS2, a spherical icosahedral virus capsid. MS2 possesses an interior and exterior surface that can be modified orthogonally using bioconjugation chemistry to create multivalent, multicomponent constructs with precise localization of components attached to the capsid proteins. Chapter 2 describes the use of MS2 to synthesize a photocatalytic construct by modifying the internal surface with sensitizing chromophores and the external surface with a photocatalytic porphyrin. The chromophores absorbed energy that the porphyrin could not, and transferred it to the porphyrin via FRET through the protein shell. The porphyrin was then able to utilize the energy to carry out photocatalysis at new wavelengths. In Chapter 3, porphyrins were installed on the interior surface of MS2 and DNA aptamers specific for Jurkat leukemia T cells on the exterior surface. The dual-modified capsids were able to bind to Jurkat cells, and upon illumination the porphyrins generated singlet oxygen to kill them selectively over non-targeted cells. Chapter 4 explores integrating MS2 with DNA origami in order to arrange the capsids at larger length scales. Capsids modified with fluorescent dyes inside and single-stranded DNA outside were able to bind to origami tiles bearing complementary DNA probes. The tiles could then be used to arrange the capsids in a one-dimensional array with dimensions far exceeding those of individual MS2 particles. In Chapter 5, the use of a different capsid, that of the tobacco mosaic virus (TMV) is described. The defect tolerance of light harvesting systems built using TMV as a scaffold was investigated using a kinetic Monte Carlo model to simulate the energy transfer processes. The results of the simulation were used to understand and explain experimental results obtained from the system.

  1. Triplet Energy Transport in Platinum-Acetylide Light Harvesting Arrays.

    PubMed

    Chen, Zhuo; Hsu, Hsien-Yi; Arca, Mert; Schanze, Kirk S

    2015-06-18

    Light harvesting and triplet energy transport is investigated in chromophore-functionalized polystyrene polymers featuring light harvesting and energy acceptor chromophores (traps) at varying loading. The series of precision polymers was constructed via reversible addition-fragmentation transfer polymerization and functionalized with platinum acetylide triplet chromophores by using an azide-alkyne "click" reaction. The polymers have narrow polydispersity and degree of polymerization ?60. The chromophores have the general structure, trans-[-R-C6H4-C?C-Pt(PBu3)2-C?C-Ar], where R is the attachment point to the polystyrene backbone and Ar is either -C6H4-C?C-Ph or -pyrenyl (PE2-Pt and Py-Pt, respectively, with triplet energies of 2.35 and 1.88 eV). The polychromophores contain mainly the high-energy PE2-Pt units (light absorber and energy donor), with randomly distributed Py-Pt units (3-20% loading, energy acceptor). Photophysical methods are used to study the dynamics and efficiency of energy transport from the PE2-Pt to Py-Pt units in the polychromophores. The energy transfer efficiency is >90% for copolymers that contain 5% of the Py-Pt acceptor units. Time-resolved phosphorescence measurements combined with Monte Carlo exciton dynamics simulations suggest that the mechanism of exciton transport is exchange energy transfer hopping between PE2-Pt units. PMID:25337631

  2. Organization of the Bacterial Light-Harvesting Apparatus Rationalized by Exciton Transport Optimization

    Microsoft Academic Search

    Elad Harel

    2011-01-01

    Photosynthesis, the process by which energy from sunlight drives cellular metabolism, relies on a unique organization of light-harvesting and reaction center complexes. Recently, the organization of light-harvesting LH2 complexes and dimeric reaction center-light harvesting I-PufX (RC-LH1-PufX) core complexes in membranes of purple non-sulfur bacteria was revealed by atomic force microscopy (AFM)1. Here, we report that the structure of LH2 and

  3. Construction of a smart microgel glutathione peroxidase mimic based on supramolecular self-assembly.

    PubMed

    Yin, Yanzhen; Jiao, Shufei; Zhang, Ruirui; Hu, Xiaoxi; Shi, Zhongfeng; Huang, Zuqiang

    2015-07-14

    In an effort to construct smart artificial glutathione peroxidase (GPx) featuring high catalytic activity in an efficient preparation process, an artificial microgel GPx (PPAM-ADA-Te) has been prepared using a supramolecular host-guest self-assembly technique. Herein, 6,6'-telluro-bis(6-deoxy-?-cyclodextrin) (CD-Te-CD) was selected as a tellurium-containing host molecule, which also served as the crosslinker for the scaffold of the supramolecular microgel. And an adamantane-containing block copolymer (PPAM-ADA) was designed and synthesized as a guest building block copolymer. Subsequently, PPAM-ADA-Te was constructed through the self-assembly of CD-Te-CD and PPAM-ADA. The formation of this self-assembled construct was confirmed by dynamic light scattering, NMR, SEM and TEM. Notably, PPAM-ADA-Te not only exhibits a significant temperature responsive catalytic activity, but also features the characteristic saturation kinetics behaviour similar to that of a natural enzyme catalyst. We demonstrate in this paper that both the hydrophobic microenvironment and the crosslinker in this supramolecular microgel network played significant roles in enhancing and altering the temperature responsive catalytic behaviour. The successful construction of PPAM-ADA-Te not only provides a novel method for the preparation of microgel artificial GPx with high catalytic activity but also provides properties suitable for the future development of intelligent antioxidant drugs. PMID:26053236

  4. Pigment interactions in light-harvesting complex II in different molecular environments.

    PubMed

    Akhtar, Parveen; Dorogi, Márta; Pawlak, Krzysztof; Kovács, László; Bóta, Attila; Kiss, Teréz; Garab, Gy?z?; Lambrev, Petar H

    2015-02-20

    Extraction of plant light-harvesting complex II (LHCII) from the native thylakoid membrane or from aggregates by the use of surfactants brings about significant changes in the excitonic circular dichroism (CD) spectrum and fluorescence quantum yield. To elucidate the cause of these changes, e.g. trimer-trimer contacts or surfactant-induced structural perturbations, we compared the CD spectra and fluorescence kinetics of LHCII aggregates, artificial and native LHCII-lipid membranes, and LHCII solubilized in different detergents or trapped in polymer gel. By this means we were able to identify CD spectral changes specific to LHCII-LHCII interactions, at (-)-437 and (+)-484 nm, and changes specific to the interaction with the detergent n-dodecyl-?-maltoside (?-DM) or membrane lipids, at (+)-447 and (-)-494 nm. The latter change is attributed to the conformational change of the LHCII-bound carotenoid neoxanthin, by analyzing the CD spectra of neoxanthin-deficient plant thylakoid membranes. The neoxanthin-specific band at (-)-494 nm was not pronounced in LHCII in detergent-free gels or solubilized in the ? isomer of DM but was present when LHCII was reconstituted in membranes composed of phosphatidylcholine or plant thylakoid lipids, indicating that the conformation of neoxanthin is sensitive to the molecular environment. Neither the aggregation-specific CD bands, nor the surfactant-specific bands were positively associated with the onset of fluorescence quenching, which could be triggered without invoking such spectral changes. Significant quenching was not active in reconstituted LHCII proteoliposomes, whereas a high degree of energetic connectivity, depending on the lipid:protein ratio, in these membranes allows for efficient light harvesting. PMID:25525277

  5. Designing dye-nanochannel antenna hybrid materials for light harvesting, transport and trapping.

    PubMed

    Calzaferri, Gion; Méallet-Renault, Rachel; Brühwiler, Dominik; Pansu, Robert; Dolamic, Igor; Dienel, Thomas; Adler, Pauline; Li, Huanrong; Kunzmann, Andreas

    2011-02-25

    We discuss artificial photonic antenna systems that are built by incorporating chromophores into one-dimensional nanochannel materials and by organizing the latter in specific ways. Zeolite L (ZL) is an excellent host for the supramolecular organization of different kinds of molecules and complexes. The range of possibilities for filling its one-dimensional channels with suitable guests has been shown to be much larger than one might expect. Geometrical constraints imposed by the host structure lead to supramolecular organization of the guests in the channels. The arrangement of dyes inside the ZL channels is what we call the first stage of organization. It allows light harvesting within the volume of a dye-loaded ZL crystal and also the radiationless transport of energy to either the channel ends or center. One-dimensional FRET transport can be realized in these guest-host materials. The second stage of organization is realized by coupling either an external acceptor or donor stopcock fluorophore at the ends of the ZL channels, which can then trap or inject electronic excitation energy. The third stage of organization is obtained by interfacing the material to an external device via a stopcock intermediate. A possibility to achieve higher levels of organization is by controlled assembly of the host into ordered structures and preparation of monodirectional materials. The usually strong light scattering of ZL can be suppressed by refractive-index matching and avoidance of microphase separation in hybrid polymer/dye-ZL materials. The concepts are illustrated and discussed in detail on a bidirectional dye antenna system. Experimental results of two materials with a donor-to-acceptor ratio of 33:1 and 52:1, respectively, and a three-dye system illustrate the validity and challenges of this approach for synthesizing dye-nanochannel hybrid materials for light harvesting, transport, and trapping. PMID:21337487

  6. Role of peptide self-assembly in antimicrobial peptides.

    PubMed

    Tian, Xibo; Sun, Fude; Zhou, Xi-Rui; Luo, Shi-Zhong; Chen, Long

    2015-07-01

    Antimicrobial peptides (AMPs) are considered as potential antibiotic substitutes because of their potent activities. Previous studies mainly focused on the effects of peptide charges and secondary structures, but the self-assembly of AMPs was neglected. As more and more researchers notice the roles of peptide self-assembly in AMPs, it has been considered as another important property. In this review, we will discuss the influences of peptide self-assembly on the activity and mode of action, and some specific features it introduces to the AMPs, such as particular responsiveness, improved cell selectivity and stability and sustained release. In addition, some methods to design self-assembling AMPs are primarily discussed. With further understanding about the self-assembling regularity, design of particular self-assembling AMPs will be very helpful for their applications, especially in the fields of drug delivery and biomedical engineering. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd. PMID:26100854

  7. Self-assembled Au nanorods - polymer composites

    NASA Astrophysics Data System (ADS)

    Park, Heung-Shik; Lavrentovich, Oleg; Agarwal, Ashish; Kotov, Nicholas

    2009-03-01

    The unique optoelectronic properties of the anisotropic metallic nanorods (NRs) are of great interest because of their potential applications in biological sensing, solar energy conversion, cloaking devices, etc. In order to utilize NRs, tuning their properties and immobilizing NRs into polymer matrix are essential. We present a simple and universal process for formation of self-assembled nanorods polymer composite. This approach is based on the anisotropic electrostatic interaction between aggregates of chromonic molecules and NRs that lead to either end-to-end or side-by-side assembly of NRs. We discuss encapsulation of these structures with polymer matrices.

  8. Bio-inspired supramolecular self-assembly towards soft nanomaterials

    PubMed Central

    LIN, Yiyang; MAO, Chuanbin

    2011-01-01

    Supramolecular self-assembly has proven to be a reliable approach towards versatile nanomaterials based on multiple weak intermolecular forces. In this review, the development of bio-inspired supramolecular self-assembly into soft materials and their applications are summarized. Molecular systems used in bio-inspired “bottom-up self-assembly” involve small organic molecules, peptides or proteins, nucleic acids, and viruses. Self-assembled soft nanomaterials have been exploited in various applications such as inorganic nanomaterial synthesis, drug or gene delivery, tissue engineering, and so on. PMID:21980594

  9. Bio-inspired supramolecular self-assembly towards soft nanomaterials

    NASA Astrophysics Data System (ADS)

    Lin, Yiyang; Mao, Chuanbin

    2011-09-01

    Supramolecular self-assembly has proven to be a reliable approach towards versatile nanomaterials based on multiple weak intermolecular forces. In this review, the development of bio-inspired supramolecular self-assembly into soft materials and their applications are summarized. Molecular systems used in bio-inspired "bottom-up self-assembly" involve small organic molecules, peptides or proteins, nucleic acids, and viruses. Self-assembled soft nanomaterials have been exploited in various applications such as inorganic nanomaterial synthesis, drug or gene delivery, tissue engineering, and so on.

  10. Perspective: Detecting and measuring exciton delocalization in photosynthetic light harvesting

    SciTech Connect

    Scholes, Gregory D., E-mail: greg.scholes@utoronto.ca; Smyth, Cathal [Department of Chemistry, University of Toronto, 80 St. George St., Toronto, Ontario M5S 3H6 (Canada)] [Department of Chemistry, University of Toronto, 80 St. George St., Toronto, Ontario M5S 3H6 (Canada)

    2014-03-21

    Photosynthetic units perform energy transfer remarkably well under a diverse range of demanding conditions. However, the mechanism of energy transfer, from excitation to conversion, is still not fully understood. Of particular interest is the possible role that coherence plays in this process. In this perspective, we overview photosynthetic light harvesting and discuss consequences of excitons for energy transfer and how delocalization can be assessed. We focus on challenges such as decoherence and nuclear-coordinate dependent delocalization. These approaches complement conventional spectroscopy and delocalization measurement techniques. New broadband transient absorption data may help uncover the difference between electronic and vibrational coherences present in two-dimensional electronic spectroscopy data. We describe how multipartite entanglement from quantum information theory allows us to formulate measures that elucidate the delocalization length of excitation and the details of that delocalization even from highly averaged information such as the density matrix.

  11. Self-Assemblies of novel molecules, VECAR

    NASA Astrophysics Data System (ADS)

    Shrestha, Bijay; Kim, Hye-Young; Lee, Soojin; Novak, Brian; Moldovan, Dorel

    2015-03-01

    VECAR is a newly synthesized molecule, which is an amphiphilic antioxidant molecule that consists of two molecular groups, vitamin-E and Carnosine, linked by a hydrocarbon chain. The hydrocarbon chain is hydrophobic and both vitamin-E and Carnosine ends are hydrophilic. In the synthesis process, the length of the hydrophobic chain of VECAR molecules can vary from the shortest (n =0) to the longest (n =18), where n indicates the number of carbon atoms in the chain. We conducted MD simulation studies of self-assembly of VECAR molecules in water using GROMACS on LONI HPC resources. Our study shows that there is a strong correlation between the shape and atomistic structure of the self-assembled nano-structures (SANs) and the chain-length (n) of VECAR molecules. We will report the results of data analyses including the atomistic structure of each SANs and the dynamic and energetic mechanisms of their formation as function of time. In summary, both VECAR molecules of chain-length n =18 and 9 form worm-like micelles, which may be used as a drug delivery system. This research is supported by the Louisiana Board of Regents-RCS Grant (LEQSF(2012-15)-RD-A-19).

  12. Directed Self-Assembly: Expectations and Achievements

    PubMed Central

    2010-01-01

    Nanotechnology has been a revolutionary thrust in recent years of development of science and technology for its broad appeal for employing a novel idea for relevant technological applications in particular and for mass-scale production and marketing as common man commodity in general. An interesting aspect of this emergent technology is that it involves scientific research community and relevant industries alike. Top–down and bottom–up approaches are two broad division of production of nanoscale materials in general. However, both the approaches have their own limits as far as large-scale production and cost involved are concerned. Therefore, novel new techniques are desired to be developed to optimize production and cost. Directed self-assembly seems to be a promising technique in this regard; which can work as a bridge between the top–down and bottom–up approaches. This article reviews how directed self-assembly as a technique has grown up and outlines its future prospects. PMID:20730077

  13. Comparison of directed self-assembly integrations

    NASA Astrophysics Data System (ADS)

    Somervell, Mark; Gronheid, Roel; Hooge, Joshua; Nafus, Kathleen; Rincon Delgadillo, Paulina; Thode, Chris; Younkin, Todd; Matsunaga, Koichi; Rathsack, Ben; Scheer, Steven; Nealey, Paul

    2012-03-01

    Directed Self-Assembly (DSA) is gaining momentum as a means for extending optical lithography past its current limits. There are many forms of the technology, and it can be used for creating both line/space and hole patterns.1-3 As with any new technology, adoption of DSA faces several key challenges. These include creation of a new materials infrastructure, fabrication of new processing hardware, and the development of implementable integrations. Above all else, determining the lowest possible defect density remains the industry's most critical concern. Over the past year, our team, working at IMEC, has explored various integrations for making 12-14nm half-pitch line/space arrays. Both grapho- and chemo-epitaxy implementations have been investigated in order to discern which offers the best path to high volume manufacturing. This paper will discuss the manufacturing readiness of the various implementations by comparing the process margin for different DSA processing steps and defect density for the entirety of the flow. As part of this work, we will describe our method for using programmed defectivity on reticle to elucidate the mechanisms that drive self-assembly defectivity on wafer.

  14. Quantifying quality in DNA self-assembly

    PubMed Central

    Wagenbauer, Klaus F.; Wachauf, Christian H.; Dietz, Hendrik

    2014-01-01

    Molecular self-assembly with DNA is an attractive route for building nanoscale devices. The development of sophisticated and precise objects with this technique requires detailed experimental feedback on the structure and composition of assembled objects. Here we report a sensitive assay for the quality of assembly. The method relies on measuring the content of unpaired DNA bases in self-assembled DNA objects using a fluorescent de-Bruijn probe for three-base ‘codons’, which enables a comparison with the designed content of unpaired DNA. We use the assay to measure the quality of assembly of several multilayer DNA origami objects and illustrate the use of the assay for the rational refinement of assembly protocols. Our data suggests that large and complex objects like multilayer DNA origami can be made with high strand integration quality up to 99%. Beyond DNA nanotechnology, we speculate that the ability to discriminate unpaired from paired nucleic acids in the same macromolecule may also be useful for analysing cellular nucleic acids. PMID:24751596

  15. Self-Assembly of Patchy Colloidal Dumbbells

    E-print Network

    Guido Avvisati; Teun Vissers; Marjolein Dijkstra

    2014-12-05

    We employ Monte Carlo simulations to investigate the self-assembly of patchy colloidal dumbbells interacting via a modified Kern-Frenkel potential by probing the system concentration and dumbbell shape. We consider dumbbells consisting of one attractive sphere with diameter $\\sigma_1$ and one repulsive sphere with diameter $\\sigma_2$ and center-to-center distance $d$ between the spheres. For three different size ratios, we study the self-assembled structures for different separations $l = 2d/(\\sigma_1+\\sigma_2)$ between the two spheres. In particular, we focus on structures that can be assembled from the homogeneous fluid, as these might be of interest in experiments. We use cluster order parameters to classify the shape of the formed structures. When the size of the spheres is almost equal, $q=\\sigma_2/\\sigma_1=1.035$, we find that, upon increasing $l$, spherical micelles are transformed to elongated micelles and finally to vesicles and bilayers. For size ratio $q=1.25$ we observe a continuously tunable transition from spherical to elongated micelles upon increasing the sphere separation. For size ratio $q=0.95$ we find bilayers and vesicles, plus faceted polyhedra and liquid droplets. Our results identify key parameters to create colloidal vesicles with attractive dumbbells in experiments.

  16. A case of adaptive self-assembly.

    PubMed

    Ding, Yi; Yang, Yang; Yang, Lu; Yan, Yun; Huang, Jianbin; Cohen Stuart, Martien A

    2012-02-28

    We report in this paper direct observation of redox-induced uptake of a charged species in micelles with a complex coacervate core, using a system consisting of negatively charged iron-coordination polymers and positively charged-b-neutral block co-polyelectrolytes. Neutral, charge-balanced micelles are first prepared by stoichiometric mixing of the oppositely charged components. Upon a redox stimulus, the micelles develop excess charges, which (as proposed in our previous work) most likely lead to sequestration of oppositely charged species, as the charge balance has to be restored. In this work we verify this prediction by using a rigid, rod-like iron coordination polymer, namely, the positively charged MEPE, as the species to be taken up. After uptake of this rigid cargo, the morphology of the micelles was found to transform from spheres to banana-shaped bundles and fibers, which clearly indicate the uptake of MEPE in the micellar core. Our result proves that the redox stimulus indeed induces excess charges in the core, which forces the self-assembled particles to change both composition and shape. As an interesting example of "adaptive self-assembly", our findings also pave the way to novel redox-triggered uptake and release systems. PMID:22208815

  17. Self-Assembly of Gemini Surfactants

    NASA Astrophysics Data System (ADS)

    Yethiraj, Arun; Mondal, Jagannath; Mahanthappa, Mahesh

    2013-03-01

    The self-assembly behavior of Gemini (dimeric or twin-tail) dicarboxylate disodium surfactants is studied using molecular dynamics simulations. This gemini architecture, in which two single tailed surfactants are joined through a flexible hydrophobic linker, has been shown to exhibit concentration-dependent aqueous self-assembly into lyotropic phases including hexagonal, gyroid, and lamellar morphologies. Our simulations reproduce the experimentally observed phases at similar amphiphile concentrations in water, including the unusual ability of these surfactants to form gyroid phases over unprecedentedly large amphiphile concentration windows. We demonstrate quanitative agreement between the predicted and experimentally observed domain spacings of these nanostructured materials. Through careful conformation analyses of the surfactant molecules, we show that the gyroid phase is electrostatically stabilized related to the lamellar phase. By starting with a lamellar phase, we show that decreasing the charge on the surfactant headgroups by carboxylate protonation or use of a bulkier tetramethyl ammonium counterion in place of sodium drives the formation of a gyroid phase.

  18. Fabrication of bioinspired nanostructured materials via colloidal self-assembly

    NASA Astrophysics Data System (ADS)

    Huang, Wei-Han

    Through millions of years of evolution, nature creates unique structures and materials that exhibit remarkable performance on mechanicals, opticals, and physical properties. For instance, nacre (mother of pearl), bone and tooth show excellent combination of strong minerals and elastic proteins as reinforced materials. Structured butterfly's wing and moth's eye can selectively reflect light or absorb light without dyes. Lotus leaf and cicada's wing are superhydrophobic to prevent water accumulation. The principles of particular biological capabilities, attributed to the highly sophisticated structures with complex hierarchical designs, have been extensively studied. Recently, a large variety of novel materials have been enabled by natural-inspired designs and nanotechnologies. These advanced materials will have huge impact on practical applications. We have utilized bottom-up approaches to fabricate nacre-like nanocomposites with "brick and mortar" structures. First, we used self-assembly processes, including convective self-assembly, dip-coating, and electrophoretic deposition to form well oriented layer structure of synthesized gibbsite (aluminum hydroxide) nanoplatelets. Low viscous monomer was permeated into layered nanoplatelets and followed by photo-curing. Gibbsite-polymer composite displays 2 times higher tensile strength and 3 times higher modulus when compared with pure polymer. More improvement occurred when surface-modified gibbsite platelets were cross-linked with the polymer matrix. We observed ˜4 times higher strength and nearly 1 order of magnitude higher modulus than pure polymer. To further improve the mechanical strength and toughness of inorganicorganic nanocomposites, we exploited ultrastrong graphene oxide (GO), a single atom thick hexagonal carbon sheet with pendant oxidation groups. GO nanocomposite is made by co-filtrating GO/polyvinyl alcohol suspension on 0.2 im pore-sized membrane. It shows ˜2 times higher strength and ˜15 times higher ultimate strains than nacre and pure GO paper (also synthesized by filtration). Specifically, it exhibits ˜30 times higher fracture energy than filtrated graphene paper and nacre, ˜100 times tougher than filtrated GO paper. Besides reinforced nanocomposites, we further explored the self-assembly of spherical colloids and the templating nanofabrication of moth-eye-inspired broadband antireflection coatings. Binary crystalline structures can be easily accomplished by spin-coating double-layer nonclose-packed colloidal crystals as templates, followed by colloidal templating. The polymer matrix between self-assembled colloidal crystal has been used as a sacrificial template to define the resulting periodic binary nanostructures, including intercalated arrays of silica spheres and polymer posts, gold nanohole arrays with binary sizes, and dimple-nipple antireflection coatings. The binary-structured antireflection coatings exhibit better antireflective properties than unitary coatings. Natural optical structures and nanocomposites teach us a great deal on how to create high performance artificial materials. The bottom-up technologies developed in this thesis are scalable and compatible with standard industrial processes, promising for manufacturing high-performance materials for the benefits of human beings.

  19. Self-assembled ultra small ZnO nanocrystals for dye-sensitized solar cell application

    SciTech Connect

    Patra, Astam K.; Dutta, Arghya; Bhaumik, Asim, E-mail: msab@iacs.res.in

    2014-07-01

    We demonstrate a facile chemical approach to produce self-assembled ultra-small mesoporous zinc oxide nanocrystals using sodium salicylate (SS) as a template under hydrothermal conditions. These ZnO nanomaterials have been successfully fabricated as a photoanode for the dye-sensitized solar cell (DSSC) in the presence of N719 dye and iodine–triiodide electrolyte. The structural features, crystallinity, purity, mesophase and morphology of the nanostructure ZnO are investigated by several characterization tools. N{sub 2} sorption analysis revealed high surface areas (203 m{sup 2} g{sup ?1}) and narrow pore size distributions (5.1–5.4 nm) for different samples. The mesoporous structure and strong photoluminescence facilitates the high dye loading at the mesoscopic void spaces and light harvesting in DSSC. By utilizing this ultra-small ZnO photoelectrode with film thickness of about 7 ?m in the DSSC with an open-circuit voltage (V{sub OC}) of 0.74 V, short-circuit current density (J{sub SC}) of 3.83 mA cm{sup ?2} and an overall power conversion efficiency of 1.12% has been achieved. - Graphical abstract: Ultra-small ZnO nanocrystals have been synthesized with sodium salicylate as a template and using it as a photoanode in a dye-sensitized solar cell 1.12% power conversion efficiency has been observed. - Highlights: • Synthesis of self-assembled ultra-small mesoporous ZnO nanocrystals by using sodium salicylate as a template. • Mesoporous ZnO materials have high BET surface areas and void space. • ZnO nanoparticles serve as a photoanode for the dye-sensitized solar cell (DSSC). • Using ZnO nanocrystals as photoelectrode power conversion efficiency of 1.12% has been achieved.

  20. Efficient light harvesting in multiple-device stacked structure for polymer solar cells

    E-print Network

    Efficient light harvesting in multiple-device stacked structure for polymer solar cells Vishal structure of polymer solar cells for efficient light harvesting. Two polymer photovoltaic cells are stacked harvesting has been demonstrated for organic solar cells uti- lizing tandem structure.11,12 However

  1. Energy Transfer in the Major Intrinsic Light-Harvesting Complex from Amphidinium carterae

    E-print Network

    van Stokkum, Ivo

    their light-harvesting capacity, especially in the blue-green spectral region. Al- though cyanobacteria and cryptophytes use phycobiliproteins in their light-harvesting antennae to harvest blue-green light (3), marine is of vital importance to underwater organisms. Marine algae are important in maintaining the stability

  2. Self-assembling chimeric polypeptide-doxorubicin conjugate nanoparticles that abolish tumours after a single injection

    NASA Astrophysics Data System (ADS)

    Andrew Mackay, J.; Chen, Mingnan; McDaniel, Jonathan R.; Liu, Wenge; Simnick, Andrew J.; Chilkoti, Ashutosh

    2009-12-01

    New strategies to self-assemble biocompatible materials into nanoscale, drug-loaded packages with improved therapeutic efficacy are needed for nanomedicine. To address this need, we developed artificial recombinant chimeric polypeptides (CPs) that spontaneously self-assemble into sub-100-nm-sized, near-monodisperse nanoparticles on conjugation of diverse hydrophobic molecules, including chemotherapeutics. These CPs consist of a biodegradable polypeptide that is attached to a short Cys-rich segment. Covalent modification of the Cys residues with a structurally diverse set of hydrophobic small molecules, including chemotherapeutics, leads to spontaneous formation of nanoparticles over a range of CP compositions and molecular weights. When used to deliver chemotherapeutics to a murine cancer model, CP nanoparticles have a fourfold higher maximum tolerated dose than free drug, and induce nearly complete tumour regression after a single dose. This simple strategy can promote co-assembly of drugs, imaging agents and targeting moieties into multifunctional nanomedicines.

  3. Metal-Directed Protein Self Assembly

    PubMed Central

    SALGADO, ERIC N.; RADFORD, ROBERT J.

    2010-01-01

    CONSPECTUS Proteins are Nature’s premier building blocks for constructing sophisticated nanoscale architectures that carry out complex tasks and chemical transformations. It is estimated that 70–80% of all proteins are permanently oligomeric, that is, they are composed of multiple proteins that are held together in precise spatial organization through non-covalent interactions. While it is of great fundamental interest to understand the physicochemical basis of protein self-assembly, the mastery of protein-protein interactions (PPIs) would also allow access to novel biomaterials using Nature’s favorite and most versatile building block. With this possibility in mind, we have developed a new approach, Metal Directed Protein Self-Assembly (MDPSA), which utilizes the strength, directionality and selectivity of metal-ligand interactions to control PPIs. At its core, MDPSA is inspired by supramolecular coordination chemistry which exploits metal coordination for the self-assembly of small molecules into discrete, more-or-less predictable higher-order structures. Proteins, however, are not exactly small molecules or simple metal ligands: they feature extensive, heterogeneous surfaces that can interact with each other and with metal ions in unpredictable ways. We will start this Account by first describing the challenges of using entire proteins as molecular building blocks. This will be followed by our work on a model protein (cytochrome cb562) to both highlight and overcome those challenges toward establishing some ground rules for MDPSA. Proteins are also Nature’s metal ligands of choice. In MDPSA, once metal ions guide proteins into forming large assemblies, they are by definition embedded within extensive interfaces formed between protein surfaces. These complex surfaces make an inorganic chemist’s life somewhat difficult, yet they also provide a wide platform to modulate the metal coordination environment through distant, non-covalent interactions – exactly as natural metalloproteins and enzymes do. We will describe our computational and experimental efforts on restructuring the non-covalent interaction network formed between proteins surrounding the interfacial metal centers. This approach of metal templating followed by the redesign of protein interfaces (Metal-Templated Interface Redesign, MeTIR) not only provides a route to engineer de novo PPIs and novel metal coordination environments, but also carries possible parallels to the evolution of metalloproteins. PMID:20192262

  4. Self-AssembledMonolayersof AlkanethiolatesPresentingTri(propylene

    E-print Network

    Prentiss, Mara

    (ethylene glycol) groups, as measuredby advancing contact angles of water of 27o and 38o, respectively. A propylenepr NE CffiM SOCIEry' Self-AssembledMonolayersof AlkanethiolatesPresentingTri(propylene sulloxidel.5136-5137 Self-AssembledMonolayersof Alkanethiolates PresentingTri(propylene sulfoxide)Groups Resist

  5. Perspective Beyond molecules: Self-assembly of mesoscopic and

    E-print Network

    Prentiss, Mara

    ) and the folding of nucleic acids into their functional forms (10). Even the association of a ligand nucleic acids, protein aggre- gates, molecular machines, and many oth- ers that form by self-assembly (12 determines the structure of the assembly (1). Synthesis makes mol- ecules; self-assembly makes ordered en

  6. Self-assembled levan nanoparticles for targeted breast cancer imaging.

    PubMed

    Kim, Sun-Jung; Bae, Pan Kee; Chung, Bong Hyun

    2015-01-01

    We report on the targeted imaging of breast cancer using self-assembled levan nanoparticles. Indocyanine green (ICG) was encapsulated in levan nanoparticles via self-assembly. Levan-ICG nanoparticles were found to be successfully accumulated in breast cancer via specific interaction between fructose moieties in levan and overexpressed glucose transporter 5 in breast cancer cells. PMID:25383444

  7. Nano-engineering by optically directed self-assembly

    Microsoft Academic Search

    Eric Furst; Elissa Dunn; Jin-Gyu Park; C. Jeffrey Brinker; Sunil Sainis; Jason Merrill; Eric Dufresne; Matthew D. Reichert; Christopher M. Brotherton; Katherine Huderle Andersen Bogart; Ryan A. Molecke; Timothy P. Koehler; Nelson Simmons Bell; Anne Mary Grillet; Allen D. Gorby; John Singh; Pushkar Lele; Manish Mittal

    2009-01-01

    Lack of robust manufacturing capabilities have limited our ability to make tailored materials with useful optical and thermal properties. For example, traditional methods such as spontaneous self-assembly of spheres cannot generate the complex structures required to produce a full bandgap photonic crystals. The goal of this work was to develop and demonstrate novel methods of directed self-assembly of nanomaterials using

  8. Molecule-Mimetic Chemistry and Mesoscale Self-Assembly

    E-print Network

    Prentiss, Mara

    Molecule-Mimetic Chemistry and Mesoscale Self-Assembly NED B. BOWDEN, MARCUS WECK, INSUNG S. CHOI, and possible uses for these processes and assemblies.6-22 Mesoscale Self-Assembly (MESA) Mesoscale Self technically, and especially in physics, a mesoscale object is one whose dimensions are comparable to the scale

  9. Electrochemical Transduction Self-Assembled Monolayers That Transduce

    E-print Network

    Mrksich, Milan

    Electrochemical Transduction Self-Assembled Monolayers That Transduce Enzymatic Activities prepared a self-assembled monolayer (SAM) con- taining an alkanethiolate terminated by a 4-hydroxyphenyl-workers developed a class of monolayer substrates in which the activities of immobilized ligands can be reversibly

  10. Hierarchical self-assembly of DNA into symmetric supramolecular polyhedra

    E-print Network

    Jiang, Wen

    LETTERS Hierarchical self-assembly of DNA into symmetric supramolecular polyhedra Yu He1 , Tao Ye1 approach to forming DNA polyhedra is a one-pot self- assembly process illustrated in Fig. 1: individual then further assemble into polyhedra through sticky-end asso- ciation between the tiles. The three

  11. Thermally and Photochemically Triggered Self-Assembly of Peptide Hydrogels

    E-print Network

    peptides that self- assemble into nanotubes,1c-e and peptides that form fibrillar -sheet networks.1f-i Here. We show that the induction of self-assembly by gentle warming or by exposure to near-infrared light results in rapid gelation of peptide/liposome suspensions into highly cross-linked, fibrillar, -sheet

  12. Predicting self-assembly: from empirism to determinism.

    PubMed

    Palma, Carlos-Andres; Cecchini, Marco; Samorì, Paolo

    2012-05-21

    Self-assembly is one of the most important concepts of the 21st century. Strikingly, despite the rational design of molecules for biological and pharmaceutical applications is rather well established, only few are the attempts to formally refine predictions of self-assembly in material science. In the present tutorial review, we encompass some of the most significant efforts towards the systematic study of (thermodynamically stable) self-assembly. We discuss experimental and computer-simulated self-assembly events in hard-matter, soft-matter and higher symmetry architectures under the common framework of partition functions. In this framework, we endeavor to correlate state-of-the-art chemical design, programming and/or engineering of reversible (thermal and chemical equilibrium) self-assembly with knowledge of the underlying partition function landscape in a step towards quantitative predictions and ab initio molecular design. PMID:22430648

  13. Self-Assembly of Optical Molecules with Supramolecular Concepts

    PubMed Central

    Okamoto, Ken; Chithra, Parayalil; Richards, Gary J.; Hill, Jonathan P.; Ariga, Katsuhiko

    2009-01-01

    Fabrication of nano-sized objects is one of the most important issues in nanoscience and nanotechnology. Soft nanomaterials with flexible properties have been given much attention and can be obtained through bottom-up processing from functional molecules, where self-assembly based on supramolecular chemistry and designed assembly have become crucial processes and techniques. Among the various functional molecules, dyes have become important materials in certain areas of nanotechnology and their self-assembling behaviors have been actively researched. In this short review, we briefly introduce recent progress in self-assembly of optical molecules and dyes, based mainly on supramolecular concepts. The introduced examples are classified into four categories: self-assembly of (i) low-molecular-weight dyes and (ii) polymeric dyes and dye self-assembly (iii) in nanoscale architectures and (iv) at surfaces. PMID:19564931

  14. Self-assembly of active attractive spheres.

    PubMed

    Prymidis, Vasileios; Sielcken, Harmen; Filion, Laura

    2015-05-20

    We study the self-assembly of a system of self-propelled, Lennard-Jones particles using Brownian dynamics simulations. We examine the state diagrams of the system for different rotational diffusion coefficients of the self-propelled motion of the particles. For fast rotational diffusion, the state diagram exhibits a strong similarity to that of the equilibrium Lennard-Jones fluid. As we decrease the rotational diffusion coefficient, the state diagram is slowly transformed. Specifically, the liquid-gas coexistence region is gradually replaced by a highly dynamic percolating network state. We find significant local alignment of the particles in the percolating network state despite the absence of aligning interactions, and propose a simple mechanism to justify the formation of this novel state. PMID:25866369

  15. Self-assembling multimeric nucleic acid constructs

    DOEpatents

    Cantor, C.R.; Niemeyer, C.M.; Smith, C.L.; Sano, Takeshi; Hnatowich, D.J.; Rusckowski, M.

    1996-10-01

    The invention is directed to constructs and compositions containing multimeric forms of nucleic acid. Multimeric nucleic acids comprise single-stranded nucleic acids attached via biotin to streptavidin and bound with a functional group. These constructs can be utilized in vivo to treat or identify diseased tissue or cells. Repeated administrations of multimeric nucleic acid compositions produce a rapid and specific amplification of nucleic acid constructs and their attached functional groups. For treatment purposes, functional groups may be toxins, radioisotopes, genes or enzymes. Diagnostically, labeled multimeric constructs may be used to identify specific targets in vivo or in vitro. Multimeric nucleic acids may also be used in nanotechnology and to create self-assembling polymeric aggregates such as membranes of defined porosity, microcircuits and many other products. 5 figs.

  16. Self-assembly of reconfigurable colloidal molecules.

    PubMed

    Ortiz, Daniel; Kohlstedt, Kevin L; Nguyen, Trung Dac; Glotzer, Sharon C

    2014-05-28

    The lock-and-key colloidal particles of Sacanna et al. are novel "dynamic" building blocks consisting of a central spherical colloidal particle (key) attached to a finite number of dimpled colloidal particles (locks) via depletion interactions strong enough to bind the particles together but weak enough that the locks are free to rotate around the key. This rotation imbues a mechanical reconfigurability to these colloidal "molecules". Here we use molecular simulation to predict that these lock-and-key building blocks can self-assemble into a wide array of complex crystalline structures that are tunable via a set of reconfigurability dimensions: the number of locks per building block, bond length, size ratio, confinement, and lock mobility. We demonstrate that, with reconfigurability, ordered structures - such as random triangle square tilings - assemble, despite being kinetically inaccessible with non-reconfigurable but similar building blocks. PMID:24756150

  17. Self-assembled magnetic surface swimmers.

    SciTech Connect

    Snezhko, A.; Belkin, M.; Aranson, I. S.; Kwok, W.-K.; Materials Science Division; Illinois Inst. of Tech.

    2009-03-20

    We report studies of novel self-assembled magnetic surface swimmers (magnetic snakes) formed from a dispersion of magnetic microparticles at a liquid-air interface and energized by an alternating magnetic field. We show that under certain conditions the snakes spontaneously break the symmetry of surface flows and turn into self-propelled objects. Parameters of the driving magnetic field tune the propulsion velocity of these snakelike swimmers. We find that the symmetry of the surface flows can also be broken in a controlled fashion by attaching a large bead to a magnetic snake (bead-snake hybrid), transforming it into a self-locomoting entity. The observed phenomena have been successfully described by a phenomenological model based on the amplitude equation for surface waves coupled to a large-scale hydrodynamic mean flow equation.

  18. Hairy self-assemblies of surfactants

    NASA Astrophysics Data System (ADS)

    Ligoure, C.

    2005-08-01

    Surfactant-containing systems are characterized by the self-assembly of aggregated units that endow the bulk level with emergent physical properties. The aggregates themselves take on different shapes from lamellae to spheres. During the last decade the soft matter complexity in this field has been contributed by the polymeric component. I will focus on the addition of amphiphilic copolymers in structured surfactant phases on simple shapes, i.e., flat bilayers, cylinders and spheres. In all cases, the hydrophobic block of the copolymer adsorbs on the surfactant layer, whereas the hydrophilic tails remain in the aqueous solvent and decorate the film. The guest component modifies both the elastic properties of the film and the interactions between the surfactant mesoscopic objects. Small angle neutron scattering is the main experimental technique we used to reveal and analyse some of these polymer-induced modifications.

  19. Self-assembling multimeric nucleic acid constructs

    DOEpatents

    Cantor, Charles R. (Boston, MA); Niemeyer, Christof M. (Bremen, DE); Smith, Cassandra L. (Boston, MA); Sano, Takeshi (Boston, MA); Hnatowich, Donald J. (Brookline, MA); Rusckowski, Mary (Southborough, MA)

    1999-10-12

    The invention is directed to constructs and compositions containing multimeric forms of nucleic acid. Multimeric nucleic acids comprise single-stranded nucleic acids attached via biotin to streptavidin and bound with a functional group. These constructs can be utilized in vivo to treat or identify diseased tissue or cells. Repeated administrations of multimeric nucleic acid compositions produce a rapid and specific amplification of nucleic acid constructs and their attached functional groups. For treatment purposes, functional groups may be toxins, radioisotopes, genes or enzymes. Diagnostically, labeled multimeric constructs may be used to identify specific targets in vivo or in vitro. Multimeric nucleic acids may also be used in nanotechnology and to create self-assembling polymeric aggregates such as membranes of defined porosity, microcircuits and many other products.

  20. Self-assembling multimeric nucleic acid constructs

    DOEpatents

    Cantor, Charles R. (Boston, MA); Niemeyer, Christof M. (Bremen, DE); Smith, Cassandra L. (Boston, MA); Sano, Takeshi (Boston, MA); Hnatowich, Donald J. (Brookline, MA); Rusckowski, Mary (Southborough, MA)

    1996-01-01

    The invention is directed to constructs and compositions containing multimeric forms of nucleic acid. Multimeric nucleic acids comprise single-stranded nucleic acids attached via biotin to streptavidin and bound with a functional group. These constructs can be utilized in vivo to treat or identify diseased tissue or cells. Repeated administrations of multimeric nucleic acid compositions produce a rapid and specific amplification of nucleic acid constructs and their attached functional groups. For treatment purposes, functional groups may be toxins, radioisotopes, genes or enzymes. Diagnostically, labeled multimeric constructs may be used to identify specific targets in vivo or in vitro. Multimeric nucleic acids may also be used in nanotechnology and to create self-assembling polymeric aggregates such as membranes of defined porosity, microcircuits and many other products.

  1. Supramolecular self-assemblies as functional nanomaterials

    NASA Astrophysics Data System (ADS)

    Busseron, Eric; Ruff, Yves; Moulin, Emilie; Giuseppone, Nicolas

    2013-07-01

    In this review, we survey the diversity of structures and functions which are encountered in advanced self-assembled nanomaterials. We highlight their flourishing implementations in three active domains of applications: biomedical sciences, information technologies, and environmental sciences. Our main objective is to provide the reader with a concise and straightforward entry to this broad field by selecting the most recent and important research articles, supported by some more comprehensive reviews to introduce each topic. Overall, this compilation illustrates how, based on the rules of supramolecular chemistry, the bottom-up approach to design functional objects at the nanoscale is currently producing highly sophisticated materials oriented towards a growing number of applications with high societal impact.

  2. Intrinsic Electronic Transport through Alkanedithiol Self-Assembled Monolayer , Wenyong WANG

    E-print Network

    Reed, Mark

    Intrinsic Electronic Transport through Alkanedithiol Self-Assembled Monolayer Takhee LEE Ã an alkanedithiol self-assembled monolayer (SAM) is investigated using a nanometer scale device. Temperature.523] KEYWORDS: organic devices, self-assembled monolayer, alkanethiol, tunneling, molecular electronics 1

  3. Self assembled structures for 3D integration

    NASA Astrophysics Data System (ADS)

    Rao, Madhav

    Three dimensional (3D) micro-scale structures attached to a silicon substrate have various applications in microelectronics. However, formation of 3D structures using conventional micro-fabrication techniques are not efficient and require precise control of processing parameters. Self assembly is a method for creating 3D structures that takes advantage of surface area minimization phenomena. Solder based self assembly (SBSA), the subject of this dissertation, uses solder as a facilitator in the formation of 3D structures from 2D patterns. Etching a sacrificial layer underneath a portion of the 2D pattern allows the solder reflow step to pull those areas out of the substrate plane resulting in a folded 3D structure. Initial studies using the SBSA method demonstrated low yields in the formation of five different polyhedra. The failures in folding were primarily attributed to nonuniform solder deposition on the underlying metal pads. The dip soldering method was analyzed and subsequently refined. A modified dip soldering process provided improved yield among the polyhedra. Solder bridging referred as joining of solder deposited on different metal patterns in an entity influenced the folding mechanism. In general, design parameters such as small gap-spacings and thick metal pads were found to favor solder bridging for all patterns studied. Two types of soldering: face and edge soldering were analyzed. Face soldering refers to the application of solder on the entire metal face. Edge soldering indicates application of solder only on the edges of the metal face. Mechanical grinding showed that face soldered SBSA structures were void free and robust in nature. In addition, the face soldered 3D structures provide a consistent heat resistant solder standoff height that serve as attachments in the integration of dissimilar electronic technologies. Face soldered 3D structures were developed on the underlying conducting channel to determine the thermo-electric reliability of face soldered structures.

  4. Large-Area Nanosphere Self-Assembly by a Micro-Propulsive Injection Method for High Throughput Periodic Surface Nanotexturing.

    PubMed

    Gao, Pingqi; He, Jian; Zhou, Suqiong; Yang, Xi; Li, Sizhong; Sheng, Jiang; Wang, Dan; Yu, Tianbao; Ye, Jichun; Cui, Yi

    2015-07-01

    A high throughput surface texturing process for optical and optoelectric devices based on a large-area self-assembly of nanospheres via a low-cost micropropulsive injection (MPI) method is presented. The novel MPI process enables the formation of a well-organized monolayer of hexagonally arranged nanosphere arrays (NAs) with tunable periodicity directly on the water surface, which is then transferred onto the preset substrates. This process can readily reach a throughput of 3000 wafers/h, which is compatible with the high volume photovoltaic manufacturing, thereby presenting a highly versatile platform for the fabrication of periodic nanotexturing on device surfaces. Specifically, a double-sided grating texturing with top-sided nanopencils and bottom-sided inverted-nanopyramids is realized in a thin film of crystalline silicon (28 ?m in thickness) using chemical etching on the mask of NAs to significantly enhance antireflection and light trapping, resulting in absorptions nearly approaching the Lambertian limit over a broad wavelength range of 375-1000 nm and even surpassing this limit beyond 1000 nm. In addition, it is demonstrated that the NAs can serve as templates for replicas of three-dimensional conformal amorphous silicon films with significantly enhanced light harvesting. The MPI induced self-assembly process may provide a universal and cost-effective solution for boosting light utilization, a problem of crucial importance for ultrathin solar cells. PMID:26039258

  5. Self-assembled ultra small ZnO nanocrystals for dye-sensitized solar cell application

    NASA Astrophysics Data System (ADS)

    Patra, Astam K.; Dutta, Arghya; Bhaumik, Asim

    2014-07-01

    We demonstrate a facile chemical approach to produce self-assembled ultra-small mesoporous zinc oxide nanocrystals using sodium salicylate (SS) as a template under hydrothermal conditions. These ZnO nanomaterials have been successfully fabricated as a photoanode for the dye-sensitized solar cell (DSSC) in the presence of N719 dye and iodine-triiodide electrolyte. The structural features, crystallinity, purity, mesophase and morphology of the nanostructure ZnO are investigated by several characterization tools. N2 sorption analysis revealed high surface areas (203 m2 g-1) and narrow pore size distributions (5.1-5.4 nm) for different samples. The mesoporous structure and strong photoluminescence facilitates the high dye loading at the mesoscopic void spaces and light harvesting in DSSC. By utilizing this ultra-small ZnO photoelectrode with film thickness of about 7 ?m in the DSSC with an open-circuit voltage (VOC) of 0.74 V, short-circuit current density (JSC) of 3.83 mA cm-2 and an overall power conversion efficiency of 1.12% has been achieved.

  6. Strongly coupled plasmonic modes on macroscopic areas via template-assisted colloidal self-assembly.

    PubMed

    Hanske, Christoph; Tebbe, Moritz; Kuttner, Christian; Bieber, Vera; Tsukruk, Vladimir V; Chanana, Munish; König, Tobias A F; Fery, Andreas

    2014-12-10

    We present ensembles of surface-ordered nanoparticle arrangements, which are formed by template-assisted self-assembly of monodisperse, protein-coated gold nanoparticles in wrinkle templates. Centimeter-squared areas of highly regular, linear assemblies with tunable line width are fabricated and their extinction cross sections can be characterized by conventional UV/vis/NIR spectroscopy. Modeling based on electrodynamic simulations shows a clear signature of strong plasmonic coupling with an interparticle spacing of 1-2 nm. We find evidence for well-defined plasmonic modes of quasi-infinite chains, such as resonance splitting and multiple radiant modes. Beyond elementary simulations on the individual chain level, we introduce an advanced model, which considers the chain length distribution as well as disorder. The step toward macroscopic sample areas not only opens perspectives for a range of applications in sensing, plasmonic light harvesting, surface enhanced spectroscopy, and information technology but also eases the investigation of hybridization and metamaterial effects fundamentally. PMID:25347293

  7. Electron transport and light-harvesting switches in cyanobacteria

    PubMed Central

    Mullineaux, Conrad W.

    2014-01-01

    Cyanobacteria possess multiple mechanisms for regulating the pathways of photosynthetic and respiratory electron transport. Electron transport may be regulated indirectly by controlling the transfer of excitation energy from the light-harvesting complexes, or it may be more directly regulated by controlling the stoichiometry, localization, and interactions of photosynthetic and respiratory electron transport complexes. Regulation of the extent of linear vs. cyclic electron transport is particularly important for controlling the redox balance of the cell. This review discusses what is known of the regulatory mechanisms and the timescales on which they occur, with particular regard to the structural reorganization needed and the constraints imposed by the limited mobility of membrane-integral proteins in the crowded thylakoid membrane. Switching mechanisms requiring substantial movement of integral thylakoid membrane proteins occur on slower timescales than those that require the movement only of cytoplasmic or extrinsic membrane proteins. This difference is probably due to the restricted diffusion of membrane-integral proteins. Multiple switching mechanisms may be needed to regulate electron transport on different timescales. PMID:24478787

  8. DNA-Based Oligochromophores as Light-Harvesting Systems.

    PubMed

    Ensslen, Philipp; Brandl, Fabian; Sezi, Sabrina; Varghese, Reji; Kutta, Roger-Jan; Dick, Bernhard; Wagenknecht, Hans-Achim

    2015-06-22

    The chromophores ethynyl pyrene as blue, ethynyl perylene as green and ethynyl Nile red as red emitter were conjugated to the 5-position of 2'-deoxyuridine via an acetylene bridge. Using phosphoramidite chemistry on solid phase labelled DNA duplexes were prepared that bear single chromophore modifications, and binary and ternary combinations of these chromophore modifications. The steady-state and time-resolved fluorescence spectra of all three chromophores were studied in these modified DNA duplexes. An energy-transfer cascade occurs from ethynyl pyrene over ethynyl perylene to ethynyl Nile red and subsequently an electron-transfer cascade in the opposite direction (from ethynyl Nile red to ethynyl perylene or ethynyl pyrene, but not from ethynyl perylene to ethynyl pyrene). The electron-transfer processes finally provide charge separation. The efficiencies by these energy and electron-transfer processes can be tuned by the distances between the chromophores and the sequences. Most importantly, excitation at any wavelength between 350 and 700?nm finally leads to charge separated states which make these DNA samples promising candidates for light-harvesting systems. PMID:26069203

  9. The light-harvesting function of carotenoids in the cyanobacterial stress-inducible IsiA complex

    E-print Network

    van Stokkum, Ivo

    The light-harvesting function of carotenoids in the cyanobacterial stress-inducible IsiA complex Available online xxxx Keywords: Carotenoids Light harvesting Ultrafast spectroscopy Cyanobacteria a b s t r a c t We present a spectroscopic investigation of the light-harvesting role of carotenoids

  10. Cascade exciton-pumping engines with manipulated speed and efficiency in light-harvesting porous ?-network films.

    PubMed

    Gu, Cheng; Huang, Ning; Xu, Fei; Gao, Jia; Jiang, Donglin

    2015-01-01

    Light-harvesting antennae are the machinery for exciton pumping in natural photosynthesis, whereas cascade energy transfer through chlorophyll is key to long-distance, efficient energy transduction. Numerous artificial antennae have been developed. However, they are limited in their cascade energy-transfer abilities because of a lack of control over complex chromophore aggregation processes, which has impeded their advancement. Here we report a viable approach for addressing this issue by using a light-harvesting porous polymer film in which a three-dimensional ?-network serves as the antenna and micropores segregate multiple dyes to prevent aggregation. Cascade energy-transfer engines are integrated into the films; the rate and efficiency of the energy-funneling engines are precisely manipulated by tailoring the dye components and contents. The nanofilms allow accurate and versatile luminescence engineering, resulting in the production of thirty emission hues, including blue, green, red and white. This advance may open new pathways for realising photosynthesis and photoenergy conversion. PMID:25746459

  11. Self-assembled single-crystal silicon circuits on plastic

    PubMed Central

    Stauth, Sean A.; Parviz, Babak A.

    2006-01-01

    We demonstrate the use of self-assembly for the integration of freestanding micrometer-scale components, including single-crystal, silicon field-effect transistors (FETs) and diffusion resistors, onto flexible plastic substrates. Preferential self-assembly of multiple microcomponent types onto a common platform is achieved through complementary shape recognition and aided by capillary, fluidic, and gravitational forces. We outline a microfabrication process that yields single-crystal, silicon FETs in a freestanding, powder-like collection for use with self-assembly. Demonstrations of self-assembled FETs on plastic include logic inverters and measured electron mobility of 592 cm2/V-s. Finally, we extend the self-assembly process to substrates each containing 10,000 binding sites and realize 97% self-assembly yield within 25 min for 100-?m-sized elements. High-yield self-assembly of micrometer-scale functional devices as outlined here provides a powerful approach for production of macroelectronic systems. PMID:16968780

  12. Light Harvesting Proteins for Solar Fuel Generation in Bioengineered Photoelectrochemical Cells

    PubMed Central

    Ihssen, Julian; Braun, Artur; Faccio, Greta; Gajda-Schrantz, Krisztina; Thöny-Meyer, Linda

    2014-01-01

    The sun is the primary energy source of our planet and potentially can supply all societies with more than just their basic energy needs. Demand of electric energy can be satisfied with photovoltaics, however the global demand for fuels is even higher. The direct way to produce the solar fuel hydrogen is by water splitting in photoelectrochemical (PEC) cells, an artificial mimic of photosynthesis. There is currently strong resurging interest for solar fuels produced by PEC cells, but some fundamental technological problems need to be solved to make PEC water splitting an economic, competitive alternative. One of the problems is to provide a low cost, high performing water oxidizing and oxygen evolving photoanode in an environmentally benign setting. Hematite, ?-Fe2O3, satisfies many requirements for a good PEC photoanode, but its efficiency is insufficient in its pristine form. A promising strategy for enhancing photocurrent density takes advantage of photosynthetic proteins. In this paper we give an overview of how electrode surfaces in general and hematite photoanodes in particular can be functionalized with light harvesting proteins. Specifically, we demonstrate how low-cost biomaterials such as cyanobacterial phycocyanin and enzymatically produced melanin increase the overall performance of virtually no-cost metal oxide photoanodes in a PEC system. The implementation of biomaterials changes the overall nature of the photoanode assembly in a way that aggressive alkaline electrolytes such as concentrated KOH are not required anymore. Rather, a more environmentally benign and pH neutral electrolyte can be used. PMID:24678669

  13. Light harvesting proteins for solar fuel generation in bioengineered photoelectrochemical cells.

    PubMed

    Ihssen, Julian; Braun, Artur; Faccio, Greta; Gajda-Schrantz, Krisztina; Thöny-Meyer, Linda

    2014-01-01

    The sun is the primary energy source of our planet and potentially can supply all societies with more than just their basic energy needs. Demand of electric energy can be satisfied with photovoltaics, however the global demand for fuels is even higher. The direct way to produce the solar fuel hydrogen is by water splitting in photoelectrochemical (PEC) cells, an artificial mimic of photosynthesis. There is currently strong resurging interest for solar fuels produced by PEC cells, but some fundamental technological problems need to be solved to make PEC water splitting an economic, competitive alternative. One of the problems is to provide a low cost, high performing water oxidizing and oxygen evolving photoanode in an environmentally benign setting. Hematite, ?-Fe2O3, satisfies many requirements for a good PEC photoanode, but its efficiency is insufficient in its pristine form. A promising strategy for enhancing photocurrent density takes advantage of photosynthetic proteins. In this paper we give an overview of how electrode surfaces in general and hematite photoanodes in particular can be functionalized with light harvesting proteins. Specifically, we demonstrate how low-cost biomaterials such as cyanobacterial phycocyanin and enzymatically produced melanin increase the overall performance of virtually no-cost metal oxide photoanodes in a PEC system. The implementation of biomaterials changes the overall nature of the photoanode assembly in a way that aggressive alkaline electrolytes such as concentrated KOH are not required anymore. Rather, a more environmentally benign and pH neutral electrolyte can be used. PMID:24678669

  14. Structural and Chemical Control of Supramolecular Coordination Self-Assembly Confined on Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Shi, Ziliang

    This thesis is concerned with the structural and chemical control of two-dimensional (2D) supramolecular self-assemblies through judiciously manipulating bonding motifs at various intrinsic and external conditions. The self-selection and the self-recognition of the noncovalent interactions among organic and/or metallic building blocks govern the structural and chemical properties of the resultant self-assembled two-dimensional nanostructures, accompanying with the thermodynamic and kinetic process as well. In this thesis, we have investigated the supramolecular self-assembly achieved via coordination bonds assisted by transition metals and functional ligands on metal surfaces. The self-assembled nanostructures were studied by ultra-high vacuum scanning tunneling microscopy working at room temperatures. The structural transition processes were also inspected via the low energy electron diffraction. Further, artificial "quantum dots" represented by the cavities of the self-assembled networks were investigated. The modulation of surface electrons by these "quantum dots" was characterized by the local density of states detected by low-temperature scanning tunneling spectroscopy. The major contributions of this thesis are outlined as below: (1) Through modifying the chemical states of organic ligands, a unique coordination Kagome network structure was obtained for the first time by two distinct methods. TPyP (5, 10, 15, 20-tetra(4-pyridyl)porphyrin) species on Au(111) surfaces form the TPyP-Au coordination Kagome network achieved by a novel treatment that was suggested to modify the chemical state of the TPyP. In a condition that the TPyP coexists with Cu on a Au(111), Cu adatoms play two roles in the self-assembly---the coordination with pyridyl end-groups and the reaction with TPyP macrocycles, which control the chemical and structural phase of the self-assembly. Following a high temperature annealing, the same Kagome structure emerged from a precursor rhombus network structure. We proposed a new mechanism which provides a consistent explanation to both assembly methods. ZnTPyP (zinc 5, 10, 15, 20-tetra(4- pyridyl)porphyrin) molecules show chemical stability at high annealing temperature, which allows for preparing chemically pure ZnTPyP-Cu bimetallic networks. Furthermore, a reversible structural transformation between a hydrogen-bonded network and a coordination network was realized by either adding Cu atoms or annealing samples at certain temperatures. (2) The influence of the thermodynamic and kinetic effects on the selection of binding modes was studied by a combined STM and LEED investigation which offered spatial as well as temporal insights. The molecules of TPyB (1,3,5-trispyridylbenzene) coordinate with Cu or Fe respectively, forming two distinct polymorphism network structures. Two coordination binding modes show different binding energies. By the kinetic and thermodynamic control, either of binding modes was selected. LEED patterns revealed the dynamic process of structural transition from that of low binding-energy mode to that of high binding-energy mode. In the latter section the structural phase transition induced by two-dimensional compression is introduced. Pyridyl-Cu coordination bond is of certain liability, allowing for the alternation of bonds under various environments. Through increasing the coverage of molecules, distinctive polygraphic networks presented via different pyridyl-Cu binding modes. (3) The self-assembly of multiple components represent a much more complicated assembly system, where the elaborate balance of interactions among all components and substrates comprises greater challenging. To study such a system, the third part deals with the multiple-ligand self-assembly. Achieved by TPyP and PBTP 4',4"-(1,4- phenylene)bis(2,2':6',2"-terpyridine)) molecules and Fe, two types of network structure formed on Au(111) surfaces. Both networks coexisted due to similar bonding configurations and free energies. However, the entropy is presumably suggested to promote the

  15. Strong antenna-enhanced fluorescence of a single light-harvesting complex shows photon antibunching

    PubMed Central

    Wientjes, Emilie; Renger, Jan; Curto, Alberto G.; Cogdell, Richard; van Hulst, Niek F.

    2014-01-01

    The nature of the highly efficient energy transfer in photosynthetic light-harvesting complexes is a subject of intense research. Unfortunately, the low fluorescence efficiency and limited photostability hampers the study of individual light-harvesting complexes at ambient conditions. Here we demonstrate an over 500-fold fluorescence enhancement of light-harvesting complex 2 (LH2) at the single-molecule level by coupling to a gold nanoantenna. The resonant antenna produces an excitation enhancement of circa 100 times and a fluorescence lifetime shortening to ~\

  16. Self-assembled alkali and alkaline earth metal nanopatterns on Fe3 O4 ( 001 )

    NASA Astrophysics Data System (ADS)

    Mariotto, G.; Ceballos, S. F.; Murphy, S.; Berdunov, N.; Seoighe, C.; Shvets, I. V.

    2004-07-01

    We have studied the mechanism of nanopattern formation by self-assembly of impurities aggregated on the Fe3O4(001) surface. Self-assembly was controlled by thermal diffusion from the bulk of natural and artificial single crystals. We show that the diffusion of potassium and calcium is of fundamental importance to the surface dynamics of magnetite. The self-assembly of Ca and K impurities, combined with the reduction in oxygen concentration, leads to the formation of nanotrenches that can be identified as a p(1×4) structure. According to our model, the formation of nanotrenches contributes in two ways to the reduction of the surface energy. Firstly, alkali and alkaline earth impurities cause a reduction of the strain energy due to their large ionic radii. Secondly, their segregation and the reduction of the O/Fe ratio at the surface cause a reduction of the surface polarity. The structure of ordered nanotrenches could be used as a template for the deposition of carbon nanotubes, fullerenes, and DNA molecules.

  17. Molecularly engineered self-assembling membranes for cell-mediated degradation.

    PubMed

    Ferreira, Daniela S; Lin, Yi-An; Cui, Honggang; Hubbell, Jeffrey A; Reis, Rui L; Azevedo, Helena S

    2015-03-11

    The use of peptide engineering to develop self-assembling membranes that are responsive to cellular enzyme activities is reported. The membranes are obtained by combining hyaluronan (HA) and a rationally designed peptide amphiphile (PA) containing a proteolytic domain (GPQGIWGQ octapeptide) sensitive to matrix metalloproteinase-1 (MMP-1). Insertion of an octapeptide in a typical PA structure does not disturb its self-assembly into fibrillar nanostructures neither the ability to form membranes with HA. In vitro enzymatic degradation with hyaluronidase and MMP-1 shows that membranes containing the MMP-1 substrate exhibit enhanced enzymatic degradation, compared with control membranes (absence of MMP-1 cleavable peptide or containing a MMP-1 insensitive sequence), being completely degraded after 7 days. Cell viability and proliferation is minimally affected by the enzymatically cleavable functionality of the membrane, but the presence of MMP-1 cleavable sequence does stimulate the secretion of MMP-1 by fibroblasts and interfere with matrix deposition, particularly the deposition of collagen. By showing cell-responsiveness to biochemical signals presented on self-assembling membranes, this study highlights the ability of modulating certain cellular activities through matrix engineering. This concept can be further explored to understand the cellular remodeling process and as a strategy to develop artificial matrices with more biomimetic degradation for tissue engineering applications. PMID:25413155

  18. RNA self-assembly and RNA nanotechnology.

    PubMed

    Grabow, Wade W; Jaeger, Luc

    2014-06-17

    CONSPECTUS: Nanotechnology's central goal involves the direct control of matter at the molecular nanometer scale to build nanofactories, nanomachines, and other devices for potential applications including electronics, alternative fuels, and medicine. In this regard, the nascent use of nucleic acids as a material to coordinate the precise arrangements of specific molecules marked an important milestone in the relatively recent history of nanotechnology. While DNA served as the pioneer building material in nucleic acid nanotechnology, RNA continues to emerge as viable alternative material with its own distinct advantages for nanoconstruction. Several complementary assembly strategies have been used to build a diverse set of RNA nanostructures having unique structural attributes and the ability to self-assemble in a highly programmable and controlled manner. Of the different strategies, the architectonics approach uniquely endeavors to understand integrated structural RNA architectures through the arrangement of their characteristic structural building blocks. Viewed through this lens, it becomes apparent that nature routinely uses thermodynamically stable, recurrent modular motifs from natural RNA molecules to generate unique and more complex programmable structures. With the design principles found in natural structures, a number of synthetic RNAs have been constructed. The synthetic nanostructures constructed to date have provided, in addition to affording essential insights into RNA design, important platforms to characterize and validate the structural self-folding and assembly properties of RNA modules or building blocks. Furthermore, RNA nanoparticles have shown great promise for applications in nanomedicine and RNA-based therapeutics. Nevertheless, the synthetic RNA architectures achieved thus far consist largely of static, rigid particles that are still far from matching the structural and functional complexity of natural responsive structural elements such as the ribosome, large ribozymes, and riboswitches. Thus, the next step in synthetic RNA design will involve new ways to implement these same types of dynamic and responsive architectures into nanostructures functioning as real nanomachines in and outside the cell. RNA nanotechnology will likely garner broader utility and influence with a greater focus on the interplay between thermodynamic and kinetic influences on RNA self-assembly and using natural RNAs as guiding principles. PMID:24856178

  19. Self-assembled nanostructures in oxide ceramics

    NASA Astrophysics Data System (ADS)

    Ansari, Haris Masood

    Self-assembled nanoislands in the gadolinia-doped ceria (GDC)/ yttria-stabilized zirconia (YSZ) system have recently been discovered. This dissertation is an attempt to study the mechanism by which these nanoislands form. Nanoislands in the GDC/YSZ system form via a strain based mechanism whereby the stress accumulated in the GDC-doped surface layer on the YSZ substrate is relieved by creation of self-assembled nanoislands by a mechanism similar to the ATG instability. Unlike what was previously believed, a modified surface layer is not required prior to annealing, that is, this modification can occur during annealing by surface diffusion of dopants from the GDC sources (distributed on the YSZ surface in either lithographically defined patch or powder form) with simultaneous breakup, which occurs at the hold temperature independent of the subsequent cooling. Additionally, we have developed a simple powder based process of producing nanoislands which bypasses lithography and thin film deposition setups. The versatility of the process is apparent in the fact that it allows us to study the effect of experimental parameters such as soak time, temperature, cooling rate and the effect of powder composition on nanoisland properties in a facile way. With the help of this process, we have shown that nanoislands are not peculiar to Gd containing oxide source materials on YSZ substrates and can also be produced with other source materials such as La2O3, Nd2O3, Sm 2O3, Eu2O3, Tb2O3 and even Y2O3, which is already present in the substrate and hence simplifies the system further. We have extended our work to include YSZ substrates of the (110) surface orientation and have found that instead of nanoisland arrays, we obtain an array of parallel nanobars which have their long axes oriented along the [1-10] direction on the YSZ-(110) surface. STEM EDS performed on both the bars and the nanoislands has revealed that they are solid YSZ-rich solid solutions with the dopant species and are heterogeneous in composition with dopant enrichment at the top of the islands (bars) while their bases are pure YSZ. Finally, we discuss some of the future work directions and possible applications of these nanostructures that are being explored in collaboration with our colleagues Kunal Parikh and Prof. Jessica O. Winter in the Dept. of Chemical and Biomolecular Engineering and Michael Susner and Prof. Michael Sumption in the Dept. of Materials Science and Engineering.

  20. Patterned self-assembly of magnetic biomolecules on semiconductor substrates

    NASA Astrophysics Data System (ADS)

    Sun, Kien Wen; Chang, Chia-Ching

    2007-05-01

    The paper reports on the methods of preparing and patterning magnetic metallothionein (Mn,Cd-MT-2) molecules on semiconductor surfaces. The molecules are placed into nanopores prepared on silicon (0 0 1) substrates. We observe the self-assembled growth of those MT molecules on the patterned Si surface. Dense arrays of molecular rods are demonstrated on templates with small pores and pitch sizes. Then the structures of the self-assembled protein are studied by atomic force microscopy (AFM) and magnetic force microscopy (MFM). Our measurements indicate that molecular self-assembly has a magnetic dipole moment which interacts with the applied magnetic field.

  1. Potential control of DNA self-assembly on gold electrode

    Microsoft Academic Search

    Cunwang Ge; Yibin Tan; Jianhui Liao; Yu Zhang; Haiqian Zhang; Ning Gu

    2002-01-01

    The self-assembly monolayer (SAM) was prepared with 2-aminoethanethiol (AET) on the gold electrode. A new approach based on\\u000a potential was first used to control DNA self-assembly covalently onto the SAM with the activation of l-ethyl-3(3-dimethylaminopropyl)-carbodiimide\\u000a (EDC) and N-hydroxysulfosuccinimide (NHS). The influence of potential on DNA self-assembly was investigated by means of cyclic\\u000a voltammetry (CV), AC impedance, Auger electron spectrometry (AES)

  2. Scaling up self-assembly: bottom-up approaches to macroscopic particle organization.

    PubMed

    Lash, M H; Fedorchak, M V; McCarthy, J J; Little, S R

    2015-07-01

    This review presents an overview of recent work in the field of non-Brownian particle self-assembly. Compared to nanoparticles that naturally self-assemble due to Brownian motion, larger, non-Brownian particles (d > 6 ?m) are less prone to autonomously organize into crystalline arrays. The tendency for particle systems to experience immobilization and kinetic arrest grows with particle radius. In order to overcome this kinetic limitation, some type of external driver must be applied to act as an artificial "thermalizing force" upon non-Brownian particles, inducing particle motion and subsequent crystallization. Many groups have explored the use of various agitation methods to overcome the natural barriers preventing self-assembly to which non-Brownian particles are susceptible. The ability to create materials from a bottom-up approach with these characteristics would allow for precise control over their pore structure (size and distribution) and surface properties (topography, functionalization and area), resulting in improved regulation of key characteristics such as mechanical strength, diffusive properties, and possibly even photonic properties. This review will highlight these approaches, as well as discuss the potential impact of bottom-up macroscale particle assembly. The applications of such technology range from customizable and autonomously self-assembled niche microenvironments for drug delivery and tissue engineering to new acoustic dampening, battery, and filtration materials, among others. Additionally, crystals made from non-Brownian particles resemble naturally derived materials such as opals, zeolites, and biological tissue (i.e. bone, cartilage and lung), due to their high surface area, pore distribution, and tunable (multilevel) hierarchy. PMID:25947543

  3. Computational Analysis of ?-Peptide Self-Assembly

    NASA Astrophysics Data System (ADS)

    McGovern, Michael

    2011-03-01

    ? - peptides are a class of synthetic oligomers that are capable of folding in precise patterns. The wide variety of side chains that are available for insertion into ? -peptide sequences along with the stability of these folded secondary structures allow precise control over the nanoscale presentation of various chemical functional groups in three dimensional space. Some ? -peptides have been shown to spontaneously fold into complex supramolecular structures, and others have been shown to be effective antimicrobial agents that are believed to act by aggregating in certain types of cell membranes. However, more work is needed to understand what drives this assembly in order to design ? -peptides that assemble in particular ways. Using molecular simulations, the process of ? -peptide aggregation is examined in a variety of environments that allow for direct comparison to experiment. Using new simulation techniques, the structure of the aggregates formed by several ? -peptides are predicted in both bulk solutions, and at interfaces. Free energy surfaces are generated using multiple geometric parameters to directly compare the favorability of different modes of aggregation. By analyzing these results, we gain an understanding of the factors that drive self-assembly and aggregation. Nanoscale Science and Engineering Center on Templated Synthesis and Assembly at the Nanoscale. We gratefully acknowledge funding from the National Science Foundation, DMR-0832760.

  4. Self-assembly of basement membrane collagen.

    PubMed

    Yurchenco, P D; Furthmayr, H

    1984-04-10

    The in vitro self-assembly of murine type IV collagen was examined by using biochemical and morphological techniques. Dimeric collagen undergoes a rapid and reversible thermal gelation at neutral pH without an appreciable lag period. The process is seen to be concentration dependent and inhibited by 2 M urea. The formed complex can be visualized by electron microscopy rotary shadowing as an irregular polygonal lattice network with extensive side by side associations within the collagenous triple-helical part of the molecules, two and three strands thick. Measurements on the matrix suggest a median stagger dimension of 170 nm, one-fifth the length of a dimer. The conversion of pepsin-generated monomers into N-terminally bound tetramers can also be demonstrated in vitro. This process is also concentration dependent and inhibited and reversed by 2 M urea but is thermally irreversible and occurs at a slow rate relative to the lateral associations. These tetramers can be seen by rotary shadowing as four-armed "spider" structures. It is proposed that lateral associations, by virtue of their faster rate of formation, precede 7S bond formation, and several models for the assembly of basement membrane collagen are discussed. PMID:6722126

  5. Self-assembling holographic biosensors and biocomputers.

    SciTech Connect

    Light, Yooli Kim; Bachand, George David (Sandia National Laboratories, Albuquerque, NM); Schoeniger, Joseph S.; Trent, Amanda M. (Sandia National Laboratories, Albuquerque, NM)

    2006-05-01

    We present concepts for self-assembly of diffractive optics with potential uses in biosensors and biocomputers. The simplest such optics, diffraction gratings, can potentially be made from chemically-stabilized microtubules migrating on nanopatterned tracks of the motor protein kinesin. We discuss the fabrication challenges involved in patterning sub-micron-scale structures with proteins that must be maintained in aqueous buffers to preserve their activity. A novel strategy is presented that employs dry contact printing onto glass-supported amino-silane monolayers of heterobifunctional crosslinkers, followed by solid-state reactions of these cross-linkers, to graft patterns of reactive groups onto the surface. Successive solution-phase addition of cysteine-mutant proteins and amine-reactive polyethylene glycol allows assembly of features onto the printed patterns. We present data from initial experiments showing successful micro- and nanopatterning of lines of single-cysteine mutants of kinesin interleaved with lines of polyethylene, indicating that this strategy can be employed to arrays of features with resolutions suitable for gratings.

  6. Self-assembled biomimetic superhydrophobic hierarchical arrays.

    PubMed

    Yang, Hongta; Dou, Xuan; Fang, Yin; Jiang, Peng

    2013-09-01

    Here, we report a simple and inexpensive bottom-up technology for fabricating superhydrophobic coatings with hierarchical micro-/nano-structures, which are inspired by the binary periodic structure found on the superhydrophobic compound eyes of some insects (e.g., mosquitoes and moths). Binary colloidal arrays consisting of exemplary large (4 and 30 ?m) and small (300 nm) silica spheres are first assembled by a scalable Langmuir-Blodgett (LB) technology in a layer-by-layer manner. After surface modification with fluorosilanes, the self-assembled hierarchical particle arrays become superhydrophobic with an apparent water contact angle (CA) larger than 150°. The throughput of the resulting superhydrophobic coatings with hierarchical structures can be significantly improved by templating the binary periodic structures of the LB-assembled colloidal arrays into UV-curable fluoropolymers by a soft lithography approach. Superhydrophobic perfluoroether acrylate hierarchical arrays with large CAs and small CA hysteresis can be faithfully replicated onto various substrates. Both experiments and theoretical calculations based on the Cassie's dewetting model demonstrate the importance of the hierarchical structure in achieving the final superhydrophobic surface states. PMID:23786830

  7. Functional Self-Assembled Nanofibers by Electrospinning

    NASA Astrophysics Data System (ADS)

    Greiner, A.; Wendorff, J. H.

    Electrospinning constitutes a unique technique for the production of nanofibers with diameters down to the range of a few nanometers. In strong contrast to conventional fiber producing techniques, it relies on self-assembly processes driven by the Coulomb interactions between charged elements of the fluids to be spun to nanofibers. The transition from a macroscopic fluid object such as a droplet emerging from a die to solid nanofibers is controlled by a set of complex physical instability processes. They give rise to extremely high extensional deformations and strain rates during fiber formation causing among others a high orientational order in the nanofibers as well as enhanced mechanical properties. Electrospinning is predominantly applied to polymer based materials including natural and synthetic polymers, but, more recently, its use has been extended towards the production of metal, ceramic and glass nanofibers exploiting precursor routes. The nanofibers can be functionalized during electrospinning by introducing pores, fractal surfaces, by incorporating functional elements such as catalysts, quantum dots, drugs, enzymes or even bacteria. The production of individual fibers, random nonwovens, or orientationally highly ordered nonwovens is achieved by an appropriate selection of electrode configurations. Broad areas of application exist in Material and Life Sciences for such nanofibers, including not only optoelectronics, sensorics, catalysis, textiles, high efficiency filters, fiber reinforcement but also tissue engineering, drug delivery, and wound healing. The basic electrospinning process has more recently been extended towards compound co-electrospinning and precision deposition electrospinning to further broaden accessible fiber architectures and potential areas of application.

  8. Excitonic energy transfer in light-harvesting complexes in purple bacteria

    E-print Network

    Ye, Jun

    Two distinct approaches, the Frenkel-Dirac time-dependent variation and the Haken-Strobl model, are adopted to study energy transfer dynamics in single-ring and double-ring light-harvesting (LH) systems in purple bacteria. ...

  9. Ultrafast dynamics of light-harvesting function of beta-carotene in carbon nanotube

    Microsoft Academic Search

    Masayuki Yoshizawa; Kenta Abe; Daisuke Kosumi; Kazuhiro Yanagi; Yasumitsu Miyata; Hiromichi Kataura

    2009-01-01

    Ultrafast dynamics of beta-carotene encapsulated in single-walled carbon nanotubes (SWCNTs) was investigated by femtosecond absorption spectroscopy. Energy transfer from the excited states of beta-carotene to SWCNTs (light-harvesting function) has been observed.

  10. Light harvesting with non covalent carbon nanotube / porphyrin compounds. C. Roqueleta

    E-print Network

    Paris-Sud XI, Université de

    Light harvesting with non covalent carbon nanotube / porphyrin compounds. C. Roqueleta , B covalently bound porphyrin/carbon nanotube compounds. The issue of the chemical stability of non covalent; Porphyrins; Energy transfer; Transient spectroscopy; Photoluminescence; Micelle swelling. 1. Introduction

  11. Supramolecular chirality in self-assembled peptide amphiphile nanostructures.

    PubMed

    Garifullin, Ruslan; Guler, Mustafa O

    2015-07-21

    Induced supramolecular chirality was investigated in the self-assembled peptide amphiphile (PA) nanosystems. Having shown that peptide chirality can be transferred to the covalently-attached achiral pyrene moiety upon PA self-assembly, the chiral information is transferred to molecular pyrene via weak noncovalent interactions. In the first design of a supramolecular chiral system, the chromophore was covalently attached to a peptide sequence (VVAGH) via an ?-aminohexanoic acid spacer. Covalent attachment yielded a PA molecule self-assembling into nanofibers. In the second design, the chromophore was encapsulated within the hydrophobic core of self-assembled nanofibers of another PA consisting of the same peptide sequence attached to lauric acid. We observed that supramolecular chirality was induced in the chromophore by PA assembly into chiral nanostructures, whether it was covalently attached, or noncovalently bound. PMID:26146021

  12. Self-assembly of globular protein-polymer diblock copolymers

    E-print Network

    Thomas, Carla S. (Carla Stephanie)

    2014-01-01

    Self-assembly of protein-polymer block copolymers provides a simple bottom-up approach towards protein nanopatteming for the fabrication of more effective and efficient bioelectronic and biocatalytic devices. Changes in ...

  13. Self-assembly of helical ribbons from chiral amphiphiles

    E-print Network

    Zastavker, Yevgeniya Vladimirovna, 1971-

    2001-01-01

    The study of the self-assembly of helical structures has been motivated by their newly found biological and technological importance. In many systems, helical ribbons are precursors to the formation of tubules, which may ...

  14. Complexity of Self-Assembled Shapes (Extended Abstract )

    E-print Network

    Winfree, Erik

    this definition of shape, we show that for any shape ~S, if Ksa( ~S) is the minimal number of distinct tile types necessary to self-assemble it then Ksa( ~S) log Ksa( ~S) is within multiplicative and additive constants

  15. Spontaneous Self-Assembly of Engineered Armadillo Repeat Protein Fragments

    E-print Network

    Caflisch, Amedeo

    Structure Article Spontaneous Self-Assembly of Engineered Armadillo Repeat Protein Fragments), and the armadillo repeat proteins (ArmRPs) (Hatzfeld, 1999, Xu and Kimelman, 2007, Tewari et al., 2010, Marfori et

  16. Self-assembly of biofunctional polymer on graphene nanoribbons.

    PubMed

    Reuven, Darkeyah G; Suggs, Kelvin; Williams, Michael D; Wang, Xiao-Qian

    2012-02-28

    Graphene's adhesive properties owing to inherent van der Waals interactions become increasingly relevant in the nanoscale regime. Polymer self-assembly via graphene-mediated noncovalent interactions offers a powerful tool for the creation of anisotropic nanopatterned systems. Here, we report the supramolecular self-assembly of biofunctional-modified poly(2-methoxystyrene) on graphene nanoribbons prepared by unzipping multiwalled carbon nanotubes. This approach promotes the glycol-modified polymer to self-assemble into structured nanopatterns with preserved bioactivity. The self-assembly is attributed to enhanced van der Waals interactions and the associated charge transfer from polymer to graphene. These findings demonstrate that the assembly yields a prospective route to novel nanomaterial systems. PMID:22239759

  17. Ordering Control of Self-Assembled Colloidal Crystals

    E-print Network

    Koh, Yaw Koon

    Colloidal crystals are 3D nanostructures formed by self assembly of nanoparticles in suspension. The interaction forces between the colloid particles are expected to affect the ordering and the defect density in the resultant ...

  18. Conformational flexibility facilitates self-assembly of complex DNA nanostructures

    E-print Network

    Jiang, Wen

    self-assembly of well defined nano- structures. Recently, we have shown that adequate conforma- tional-up approach to the preparation of nanostructures (1­3). DNA, in partic- ular, shows great potential

  19. Bright Fluorescence and Host-Guest Sensing with a Nanoscale M4 L6 Tetrahedron Accessed by Self-Assembly of Zinc-Imine Chelate Vertices and Perylene Bisimide Edges.

    PubMed

    Frischmann, Peter D; Kunz, Valentin; Würthner, Frank

    2015-06-15

    A highly luminescent Zn4 L6 tetrahedron is reported with 3.8?nm perylene bisimide edges and hexadentate Zn(II) -imine chelate vertices. Replacing Fe(II) and monoamines commonly utilized in subcomponent self-assembly with Zn(II) and tris(2-aminoethyl)amine provides access to a metallosupramolecular host with the rare combination of structural integrity at concentrations <10(-7) ?mol?L(-1) and an exceptionally high fluorescence quantum yield of ?em =0.67. Encapsulation of multiple perylene or coronene guest molecules is accompanied by strong luminescence quenching. We anticipate this self-assembly strategy may be generalized to improve access to brightly fluorescent coordination cages tailored for host-guest light-harvesting, photocatalysis, and sensing. PMID:25925735

  20. Molecular design of the photosystem II light-harvesting antenna: photosynthesis and photoprotection

    Microsoft Academic Search

    Peter Horton; Alexander Ruban

    2004-01-01

    The photosystem II (PSII) light-harvesting system car- ries out two essential functions, the efficient collection of light energy for photosynthesis, and the regulated dissipation of excitation energy in excess of that which can be used. This dual function requires structural and functional flexibility, in which light-harvesting proteins respond to an external signal, the thylakoid DpH, to induce feedback control. This

  1. Laser-assisted nanoimprinting using self-assembled nanoparticles

    Microsoft Academic Search

    L. P. Li; Y. F. Lu; K. K. Mendu; D. W. Doerr; D. R. Alexander

    2004-01-01

    A new approach to fabricating hemispherical-cavity arrays on silicon substrates using laser-assisted nanoimprinting of self-assembled particles has been developed. Monolayers of silica or polystyrene particles, with different diameters ranging from 160 nm to 5 \\/spl mu\\/m, were deposited on silicon substrates by self-assembly. A quartz plate, which is transparent to the laser wavelength of 248 nm, was tightly placed on

  2. Self-Assembly Based on Chromium\\/Copper Bilayers

    Microsoft Academic Search

    Pawan Tyagi; Noy Bassik; Timothy G. Leong; Jeong-Hyun Cho; Bryan R. Benson; David H. Gracias

    2009-01-01

    In this paper, we detail a strategy to self-assemble microstructures using chromium\\/copper (Cr\\/Cu) bilayers. Self-assembly was primarily driven by the intrinsic residual stresses of Cr within these films; in addition, the degree of bending could be controlled by changing the Cu film thickness and by introducing a third layer with either a flexible polymer or a rigid metal. We correlate

  3. Self-assembly of polymeric microspheres of complex internal structures

    Microsoft Academic Search

    Marcin Fialkowski; Agnieszka Bitner; Bartosz A. Grzybowski

    2005-01-01

    Self-assembly can easily produce intricate structures that would be difficult to make by conventional fabrication means. Here, self-assembly is used to prepare multicomponent polymeric microspheres of arbitrary internal symmetries. Droplets of liquid prepolymers are printed onto a water-soluble hydrogel, and are allowed to spread and coalesce into composite patches. These patches are then immersed in an isodense liquid, which both

  4. Molecular Recognition Directed Self-Assembly of Supramolecular Liquid Crystals

    Microsoft Academic Search

    V. Percec; J. Heck; G. Johansson; D. Tomazos; M. Kawasumi; P. Chu; G. Ungar

    1994-01-01

    The first part of this paper discusses the molecular design of selected examples of structural units containing taper shaped exo-receptors and various crown ether, oligooxyethylenic, and H-bonding based endo-receptors, which self-assemble into cylindrical channel-like architectures via principles resembling those of tobacco mosaic virus (TMV). The ability of these structural units to self-assemble via a delicate combination of exo- and endo-recognition

  5. Self-assembly of amphiphilic peanut-shaped nanoparticles

    E-print Network

    Stephen Whitelam; Stefan A. F. Bon

    2010-02-19

    We use computer simulation to investigate the self-assembly of Janus-like amphiphilic peanut-shaped nanoparticles, finding phases of clusters, bilayers and micelles in accord with ideas of packing familiar from the study of molecular surfactants. However, packing arguments do not explain the hierarchical self-assembly dynamics that we observe, nor the coexistence of bilayers and faceted polyhedra. This coexistence suggests that experimental realizations of our model can achieve multipotent assembly of either of two competing ordered structures.

  6. Calixarene-encapsulated nanoparticles: self-assembly into functional nanomaterials

    Microsoft Academic Search

    Alexander Wei

    2006-01-01

    Calixarenes are excellent surfactants for enhancing the dispersion and self-assembly of metal nanoparticles into well-defined structures, particularly those with unit length scales in the 10–100 nm size range. Particles within these ensembles are strongly coupled, giving rise to unique collective optical or magnetic properties. The self-assembled nanostructures described in this feature article include 2D arrays of colloidal Au nanoparticles with

  7. Self-assembly of silicotungstate anions on silver surfaces

    Microsoft Academic Search

    Maohui Ge; Bianxiao Zhong; Walter G. Klemperer; Andrew A. Gewirth

    1996-01-01

    We report here the self assembly of α-dodecatungstosilicate anions, α-SiWââOââ⁴⁻, on Ag(111) surfaces from acidic aqueous solution. The ability of α-SiWââOââ⁴⁻ to form self-assembled monolayers on Ag(111) offers great opportunity for generalization to other functionalized inorganic molecules on other surfaces. We find that the silicotungstate anions will also adhere to Cu surfaces, and we anticipate that they will bind to

  8. Two-dimensional nanoarchitectonics based on self-assembly

    Microsoft Academic Search

    Katsuhiko Ariga; Michael V. Lee; Taizo Mori; Xiao-Yan Yu; Jonathan P. Hill

    2010-01-01

    Top–down nanofabrication techniques, especially photolithography, have advanced nanotechnology to a point where system-process integration with bottom–up self-assembly is now required. Because most lithographic techniques are constrained to two-dimensional planes, investigation of integrated self-assembly systems should focus on two-dimensional organization. In this review, research on two-dimensional nanoartchitectonics is classified and summarized according to the type of interface used. Pattern formation following

  9. Modelling Self-assembly in BlenX

    Microsoft Academic Search

    Roberto Larcher; Corrado Priami; Alessandro Romanel

    2010-01-01

    \\u000a The process through which disordered components spontaneously arrange themselves into patterns is called self-assembly. Molecular\\u000a self-assembly describes the process by which molecules adopt a defined arrangement without external guidance (e.g. formation\\u000a of membranes and protein complexes). These biological processes are essential to the functioning of cells. We investigate\\u000a the usage of BlenX, a process calculi based programming language, for modelling

  10. Self-assembly of (sub-)micron particles into supermaterials

    NASA Astrophysics Data System (ADS)

    Elwenspoek, Miko; Abelmann, Leon; Berenschot, Erwin; van Honschoten, Joost; Jansen, Henri; Tas, Niels

    2010-06-01

    We review aspects of static self-assembly with regard to the synthesizing of new types of three-dimensional materials made of specifically designed particles in the 100 nm to 10 µm range. Mechanical interconnection technologies based on static friction used in the assembly of macroscopic systems (such as screws and nails) are unsuitable for self-assembly. An analogy of self-assembly with first-order phase transitions is used to argue that self-assembly is a process requiring interfaces separating assembled and disordered regions. Available types of interaction are reviewed with emphasis on scaling. We discuss at some length how interaction and dynamic properties scale with respect to the particle size. Chains of particles seem to be of particular importance as they might form three-dimensional structures similar to proteins. These structures are constrained by the sequence of the particles and by their interactions between themselves and with the solvent. Using chains might provide a viable route to complex, inhomogeneous, supermaterials and systems. Kinetic processes, specifically nucleation and the relationship between self-assembly and thermodynamic phase transitions form a major part of this paper. Finally we review some applications of self-assembly, notably in MEMS, and put forward some ideas for the assembly of new types of (smart) supermaterials with interesting optical, mechanical, electrical and magnetic properties and describe some of the technological challenges we face when attempting to realize these materials and systems thereof.

  11. Electric Field Controlled Self-Assembly of Hierarchically Ordered Membranes

    PubMed Central

    Velichko, Yuri S.; Mantei, Jason R.; Bitton, Ronit; Carvajal, Daniel; Shull, Kenneth R.; Stupp, Samuel I.

    2012-01-01

    Self-assembly in the presence of external forces is an adaptive, directed organization of molecular components under nonequilibrium conditions. While forces may be generated as a result of spontaneous interactions among components of a system, intervention with external forces can significantly alter the final outcome of self-assembly. Superimposing these intrinsic and extrinsic forces provides greater degrees of freedom to control the structure and function of self-assembling materials. In this work we investigate the role of electric fields during the dynamic self-assembly of a negatively charged polyelectrolyte and a positively charged peptide amphiphile in water leading to the formation of an ordered membrane. In the absence of electric fields, contact between the two solutions of oppositely charged molecules triggers the growth of closed membranes with vertically oriented fibrils that encapsulate the polyelectrolyte solution. This process of self-assembly is intrinsically driven by excess osmotic pressure of counterions, and the electric field is found to modify the kinetics of membrane formation, and also its morphology and properties. Depending on the strength and orientation of the field we observe a significant increase or decrease of up to nearly 100% in membrane thickness, as well as the controlled rotation of nanofiber growth direction by 90 degrees, resulting in a significant increase in mechanical stiffness. These results suggest the possibility of using electric fields to control structure in self-assembly processes involving diffusion of oppositely charged molecules. PMID:23166533

  12. Self assembly: An approach to terascale integration

    SciTech Connect

    Singer, S.

    1993-09-01

    Surely one of the most remarkable accomplishments of modern times has been the miniaturization of electronic components, starting with discrete transistors and leading to Very Large Scale Integrated (VLSI) Circuits which will soon contain almost 100 million components in a few square centimeters. It led to an information processing industry that fuels almost every aspect of industrial societies and that has brought manifold benefits to their citizens. Although continuation of the miniaturization process is likely to produce even greater benefits, many experts are concerned that extrapolation of traditional silicon VLSI techniques will meet with increasingly severe difficulties. Some of these are fundamental in nature, e. g., granularity and fluctuations in semiconductors and interconnects and proximity effects such as tunneling. The first major difficulty to be encountered will be a rising cost of products due to increased complexity and difficulty of manufacturing and assembly. Such difficulties are likely to be seen in about 10 years when minimum component sizes are expected to decrease below 0.15--0.2 {mu}m. If alternatives to present VLSI techniques are to be available when needed, work on them must start now. At Los Alamos, we are exploring the feasibility of ultrasmall wires and switches that self-assemble themselves into computing elements and circuits. Their operation is based on the quantum properties of nanometer scale molecular clusters. This paper will describe our efforts in the development of these components and will summarize our work in four areas: (1) the development of conducting molecular wires, (2) conducting nanoparticle wires and switches based on the Coulomb Blockade principle, (3) the development of advanced architectures that benefit from the use of such components and that significantly advance the art of high performance computing, and (4) the development of novel methods for attaining sub-Angstrom 3-D non-destructive imaging.

  13. Low-Bandgap Thiophene Dendrimers for Improved Light Harvesting

    SciTech Connect

    Rupert, B. L.; Mitchell, W. J.; Ferguson, A. J.; Kose, M. E.; Rance, W. L.; Rumbles, G.; Ginley, D. S.; Shaheen, S. E.; Kopidakis, N.

    2009-01-01

    This article follows our previous work on the synthesis and characterization of pi-conjugated dendrimers for use in organic solar cells. Here we discuss five new thiophene-based dendrimers that were synthesized in order to study the relationship between their chemical structures and electronic properties. Three of these dendrimers incorporate acetylene spacers, included to relieve steric strain, between the thiophene arms and phenyl cores used in previous studies. Only a small effect on the electronic properties is observed upon inclusion of the acetylene spacer in the three-arm dendrimer, 3G1-2S-Ac. In contrast, a decrease in the bandgap is observed for the four-arm dendrimer, 4G1-2S-Ac, due to a reduction of interactions between the arms in the more sterically congested 1,2,4,5-arrangement around the phenyl core, resulting in delocalization of the exciton through the phenyl core. Incorporation of electron-withdrawing cyano groups on the phenyl core of the three-arm dendrimer, 3G1-2S-CN, resulted in a very large ({approx}0.5 eV) decrease in the bandgap, due to stabilization of the lowest unoccupied molecular orbital, and the low energy absorption band in this material is attributed to a transition with significant intramolecular charge-transfer character. The electronic properties of three- and four-arm dendrimers with electron-donating dibutylaniline moieties attached to the end of the thiophene dendron, 3G1-2S-N and 4G1-2S-N respectively, are almost identical, indicating that they are dominated by the arms, with no through-core communication allowed, even for the para-linked arms of 4G1-2S-N. However, there is a significant increase in the molar absorptivity of these materials, concomitant with significant broadening of the absorption spectrum, which is an important attribute in light-harvesting applications.

  14. The Self-Assembly of Nanogold for Optical Metamaterials

    NASA Astrophysics Data System (ADS)

    Nidetz, Robert A.

    2011-12-01

    Optical metamaterials are an emerging field that enables manipulation of light like never before. Producing optical metamaterials requires sub-wavelength building blocks. The focus here was to develop methods to produce building blocks for metamaterials from nanogold. Electron-beam lithography was used to define an aminosilane patterned chemical template in order to electrostatically self-assemble citrate-capped gold nanoparticles. Equilibrium self-assembly was achieved in 20 minutes by immersing chemical templates into gold nanoparticle solutions. The number of nanoparticles that self-assembled on an aminosilane dot was controlled by manipulating the diameters of the dots and nanoparticles. Adding salt to the nanoparticle solution enabled the nanoparticles to self-assemble in greater numbers on the same sized dot. However, the preparation of the nanoparticle solution containing salt was sensitive to spikes in the salt concentration which led to aggregation of the nanoparticles and non-specific deposition. Gold nanorods were also electrostatically self-assembled. Polyelectrolyte-coated gold nanorods were patterned with limited success. A polyelectrolyte chemical template also patterned gold nanorods, but the gold nanorods preferred to pattern on the edges of the pattern. Ligand-exchanged gold nanorods displayed the best self-assembly, but suffered from slow kinetics. Self-assembled gold nanoparticles were cross-linked with poly(diallyldimethylammonium chloride). The poly(diallyldimethylammonium chloride) allowed additional nanoparticles to pattern on top of the already patterned nanoparticles. Cross-linked nanoparticles were lifted-off of the substrate by sonication in a sodium hydroxide solution. The presence of van der Waals forces and/or amine bonding prevent the nanogold from lifting-off without sonication. A good-solvent evaporation process was used to self-assemble poly(styrene) coated gold nanoparticles into spherical microbead assemblies. The use of larger nanoparticles and larger poly(styrene) ligands resulted in larger and smaller assemblies, respectively. Stirring the solution resulted in a wider size distribution of microbead assemblies due to the stirring's shear forces. Two undeveloped methods to self-assemble nanogold were investigated. One method used block-copolymer thin films as chemical templates to direct the electrostatic self-assembly of nanogold. Another method used gold nanorods that are passivated with different ligands on different faces. The stability of an alkanethiol ligand in different acids and bases was investigated to determine which materials could be used to produce Janus nanorods.

  15. Lipid-like self-assembling peptides.

    PubMed

    Zhang, Shuguang

    2012-12-18

    One important question in prebiotic chemistry is the search for simple structures that might have enclosed biological molecules in a cell-like space. Phospholipids, the components of biological membranes, are highly complex. Instead, we looked for molecules that might have been available on prebiotic Earth. Simple peptides with hydrophobic tails and hydrophilic heads that are made up of merely a combination of these robust, abiotically synthesized amino acids and could self-assemble into nanotubes or nanovesicles fulfilled our initial requirements. These molecules could provide a primitive enclosure for the earliest enzymes based on either RNA or peptides and other molecular structures with a variety of functions. We discovered and designed a class of these simple lipid-like peptides, which we describe in this Account. These peptides consist of natural amino acids (glycine, alanine, valine, isoleucine, leucine, aspartic acid, glutamic acid, lysine, and arginine) and exhibit lipid-like dynamic behaviors. These structures further undergo spontaneous assembly to form ordered arrangements including micelles, nanovesicles, and nanotubes with visible openings. Because of their simplicity and stability in water, such assemblies could provide examples of prebiotic molecular evolution that may predate the RNA world. These short and simple peptides have the potential to self-organize to form simple enclosures that stabilize other fragile molecules, to bring low concentration molecules into a local environment, and to enhance higher local concentration. As a result, these structures plausibly could not only accelerate the dehydration process for new chemical bond formation but also facilitate further self-organization and prebiotic evolution in a dynamic manner. We also expect that this class of lipid-like peptides will likely find a wide range of uses in the real world. Because of their favorable interactions with lipids, these lipid-like peptides have been used to solubilize and stabilize membrane proteins, both for scientific studies and for the fabrication of nanobiotechological devices. They can also increase the solubility of other water-insoluble molecules and increase long-term stability of some water-soluble proteins. Likewise, because of their lipophilicity, these structures can deliver molecular cargo, such as small molecules, siRNA, and DNA, in vivo for potential therapeutic applications. PMID:22720818

  16. Insight into the Structure of Light Harvesting Complex II and its Stabilization in Detergent Solution

    SciTech Connect

    Cardoso, Mateus B [ORNL; Smolensky, Dmitriy [ORNL; Heller, William T [ORNL; O'Neill, Hugh Michael [ORNL

    2009-01-01

    The structure of spinach light-harvesting complex II (LHC II), stabilized in a solution of the detergent n-octyl-{beta}-d-glucoside (BOG), was investigated by small-angle neutron scattering (SANS). Physicochemical characterization of the isolated complex indicated that it was pure (>95%) and also in its native trimeric state. SANS with contrast variation was used to investigate the properties of the protein-detergent complex at three different H{sub 2}O/D{sub 2}O contrast match points, enabling the scattering properties of the protein and detergent to be investigated independently. The topological shape of LHC II, determined using ab initio shape restoration methods from the SANS data at the contrast match point of BOG, was consistent with the X-ray crystallographic structure of LHC II (Liu et al. Nature 2004 428, 287-292). The interactions of the protein and detergent were investigated at the contrast match point for the protein and also in 100% D{sub 2}O. The data suggested that BOG micelle structure was altered by its interaction with LHC II, but large aggregate structures were not formed. Indirect Fourier transform analysis of the LHC II/BOG scattering curves showed that the increase in the maximum dimension of the protein-detergent complex was consistent with the presence of a monolayer of detergent surrounding the protein. A model of the LHC II/BOG complex was generated to interpret the measurements made in 100% D{sub 2}O. This model adequately reproduced the overall size of the LHC II/BOG complex, but demonstrated that the detergent does not have a highly regular shape that surrounds the hydrophobic periphery of LHC II. In addition to demonstrating that natively structured LHC II can be produced for functional characterization and for use in artificial solar energy applications, the analysis and modeling approaches described here can be used for characterizing detergent-associated {alpha}-helical transmembrane proteins.

  17. Self-Assembled Surfactant Cyclic Peptide Nanostructures as Stabilizing Agents

    PubMed Central

    Mandal, Dindyal; Oh, Donghoon; Ye, Guofeng; Banerjee, Antara; Yadav, Arpita; Parang, Keykavous

    2013-01-01

    A number of cyclic peptides including [FR]4, [FK]4, [WR]4, [CR]4, [AK]4, and [WK]n (n = 3-5) containing L-amino acids were produced using solid-phase peptide synthesis. We hypothesized that an optimal balance of hydrophobicity and charge could generate self-assembled nanostructures in aqueous solution by intramolecular and/or intermolecular interactions. Among all the designed peptides, [WR]n (n = 3-5) generated self-assembled vesicle-like nanostructures at room temperature as shown by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and/or dynamic light scattering (DLS). This class of peptides represents the first report of surfactant-like cyclic peptides that self-assemble into nanostructures. A plausible mechanistic insight into the self-assembly of [WR]5 was obtained by molecular modeling studies. Modified [WR]5 analogues, such as [WMeR]5, [WR(Me)2]5, [WMeR(Me)2]5, and [WdR]5, exhibited different morphologies to [WR]5 as shown by TEM observations. [WR]5 exhibited a significant stabilizing effect for generated silver nanoparticles and glyceraldehyde-3-phosphate dehydrogenase activity. These studies established a new class of surfactant-like cyclic peptides that self-assembled into nanostructures and could have potential applications for the stabilization of silver nanoparticles and protein biomolecules. PMID:24187575

  18. Structure-based model for light-harvesting properties of nucleic acid nanostructures

    E-print Network

    Pan, Keyao

    Programmed self-assembly of DNA enables the rational design of megadalton-scale macromolecular assemblies with sub-nanometer scale precision. These assemblies can be programmed to serve as structural scaffolds for secondary ...

  19. Guided and magnetic self-assembly of tunable magnetoceptive gels.

    PubMed

    Tasoglu, S; Yu, C H; Gungordu, H I; Guven, S; Vural, T; Demirci, U

    2014-01-01

    Self-assembly of components into complex functional patterns at microscale is common in nature, and used increasingly in numerous disciplines such as optoelectronics, microfabrication, sensors, tissue engineering and computation. Here, we describe the use of stable radicals to guide the self-assembly of magnetically tunable gels, which we call 'magnetoceptive' materials at the scale of hundreds of microns to a millimeter, each can be programmed by shape and composition, into heterogeneous complex structures. Using paramagnetism of free radicals as a driving mechanism, complex heterogeneous structures are built in the magnetic field generated by permanent magnets. The overall magnetic signature of final structure is erased via an antioxidant vitamin E, subsequent to guided self-assembly. We demonstrate unique capabilities of radicals and antioxidants in fabrication of soft systems with heterogeneity in material properties, such as porosity, elastic modulus and mass density; then in bottom-up tissue engineering and finally, levitational and selective assembly of microcomponents. PMID:25175148

  20. Self-assembling peptide scaffolds for regenerative medicine

    PubMed Central

    Matson, John B.

    2012-01-01

    Biomaterials made from self-assembling, short peptides and peptide derivatives have great potential to generate powerful new therapies in regenerative medicine. The high signaling capacity and therapeutic efficacy of peptidic scaffolds has been established in several animal models, and the development of more complex, hierarchical structures based on peptide materials is underway. This highlight discusses several classes of self-assembling peptide-based materials, including peptide amphiphiles, Fmoc-peptides, self-complementary ionic peptides, hairpin peptides, and others. The self-assembly designs, bioactive signalling strategies, and cell signalling capabilities of these bioactive materials are reported. The future challenges of the field are also discussed, including short-term goals such as integration with biopolymers and traditional implants, and long term goals, such as immune system programming, subcellular targeting, and the development of highly integrated scaffold systems. PMID:22080255

  1. Self-assembly of tunable protein suprastructures from recombinant oleosin

    PubMed Central

    Vargo, Kevin B.; Parthasarathy, Ranganath; Hammer, Daniel A.

    2012-01-01

    Using recombinant amphiphilic proteins to self-assemble suprastructures would allow precise control over surfactant chemistry and the facile incorporation of biological functionality. We used cryo-TEM to confirm self-assembled structures from recombinantly produced mutants of the naturally occurring sunflower protein, oleosin. We studied the phase behavior of protein self-assembly as a function of solution ionic strength and protein hydrophilic fraction, observing nanometric fibers, sheets, and vesicles. Vesicle membrane thickness correlated with increasing hydrophilic fraction for a fixed hydrophobic domain length. The existence of a bilayer membrane was corroborated in giant vesicles through the localized encapsulation of hydrophobic Nile red and hydrophilic calcein. Circular dichroism revealed that changes in nanostructural morphology in this family of mutants was unrelated to changes in secondary structure. Ultimately, we envision the use of recombinant techniques to introduce novel functionality into these materials for biological applications. PMID:22753512

  2. Self-assembly and switching in ferroelectrics and multiferroics

    NASA Astrophysics Data System (ADS)

    Scott, J. F.

    2013-08-01

    Molecules of low symmetry often self-assemble in Nature to produce mesoscopic structures of symmetry higher than their constituent building blocks, including “super-cubic” structures. Such self-assembled hexagonal domains have recently been observed in orthorhombic polymeric ferroelectrics, and resemble those known in surfactants and in magnetic bubble domains. Ferroelastic nanodomains in ferroelectric films also self-assemble into bundles of tens of nanometers diameter within each ferroelectric domain that locally average polarization \\langle P\\rangle and strain \\langle s\\rangle to small values. Under applied stress or electric or magnetic field these bundles exhibit higher mobility than expected and switch polarization via magnetostriction plus piezoelectricity. The phenomenon is analogous to Anderson's 1962 model of “vortex bundle” motion in Type-II superconductors.

  3. Self-assembly of polyhedral shells: A molecular dynamics study

    E-print Network

    D. C. Rapaport

    2004-07-18

    The use of reduced models for investigating the self-assembly dynamics underlying protein shell formation in spherical viruses is described. The spontaneous self-assembly of these polyhedral, supramolecular structures, in which icosahedral symmetry is a conspicuous feature, is a phenomenon whose dynamics remain unexplored; studying the growth process by means of computer simulation provides access to the mechanisms underlying assembly. In order to capture the more universal aspects of self-assembly, namely the manner in which component shapes influence structure and assembly pathway, in this exploratory study low-resolution approximations are used to represent the basic protein building blocks. Alternative approaches involving both irreversible and reversible assembly are discussed, models based on both schemes are introduced, and examples of the resulting behavior described.

  4. Hierarchical self-assembly of chiral fibres from achiral particles.

    PubMed

    Prybytak, P; Frith, W J; Cleaver, D J

    2012-10-01

    We investigate, by molecular dynamics simulation, the behaviour of discotic particles in a solvent of Lennard-Jones spheres. When chromonic disc-sphere interactions are imposed on these systems, three regimes of self-assembly are observed. At moderate temperatures, numerous short threads of discs develop, but these threads remain isolated from one another. Quenching to low temperatures, alternatively, causes all of the discs to floc into a single extended aggregate which typically comprises several distinct sections and contains numerous packing defects. For a narrow temperature range between these regimes, however, defect-free chiral fibres are found to freely self-assemble. The spontaneous chirality of these fibres results from frustration between the hexagonal packing and interdigitation of neighbouring threads, the pitch being set by the particle shape. This demonstration of aggregate-wide chirality emerging owing to packing alone is pertinent to many biological and synthetic hierarchically self-assembling systems. PMID:24098850

  5. Hierarchical self-assembly of chiral fibres from achiral particles

    PubMed Central

    Prybytak, P.; Frith, W. J.; Cleaver, D. J.

    2012-01-01

    We investigate, by molecular dynamics simulation, the behaviour of discotic particles in a solvent of Lennard-Jones spheres. When chromonic disc–sphere interactions are imposed on these systems, three regimes of self-assembly are observed. At moderate temperatures, numerous short threads of discs develop, but these threads remain isolated from one another. Quenching to low temperatures, alternatively, causes all of the discs to floc into a single extended aggregate which typically comprises several distinct sections and contains numerous packing defects. For a narrow temperature range between these regimes, however, defect-free chiral fibres are found to freely self-assemble. The spontaneous chirality of these fibres results from frustration between the hexagonal packing and interdigitation of neighbouring threads, the pitch being set by the particle shape. This demonstration of aggregate-wide chirality emerging owing to packing alone is pertinent to many biological and synthetic hierarchically self-assembling systems. PMID:24098850

  6. Intrinsic Defect Formation in Peptide Self-Assembly

    E-print Network

    Li Deng; Yurong Zhao; Hai Xu; Yanting Wang

    2015-04-05

    In contrast to extensively studied defects in traditional materials, we report here for the first time a systematic investigation of the formation mechanism of intrinsic defects in self-assembled peptide nanostructures. The Monte Carlo simulations with our simplified dynamic hierarchical model revealed that the symmetry breaking of layer bending mode at the two ends during morphological transformation is responsible for intrinsic defect formation, whose microscopic origin is the mismatch between layer stacking along the side-chain direction and layer growth along the hydrogen bond direction. Moreover, defect formation does not affect the chirality of the self-assembled structure, which is determined by the initial steps of the peptide self-assembly process.

  7. Actinide Sequestration Using Self-Assembled Monolayers on Mesoporous Supports

    SciTech Connect

    Fryxell, Glen E.; Lin, Yuehe; Fiskum, Sandra K.; Birnbaum, Jerome C.; Wu, Hong; Kemner, K. M.; Kelly, Shelley

    2005-03-01

    Surfactant templated synthesis of mesoporous ceramics provides a versatile foundation upon which to create high efficiency environmental sorbents. These nanoporous ceramic oxides condense a huge amount of surface area into a very small volume. The ceramic oxide interface is receptive to surface functionalization through molecular self-assembly. The marriage of mesoporous ceramics with self-assembled monolayer chemistry creates a powerful new class of environmental sorbent materials called self-assembled monolayers on mesoporous supports (SAMMS). These SAMMS materials are highly efficient sorbents, whose interfacial chemistry can be fine-tuned to selectively sequester a specific target species, such as heavy metals, tetrahedral oxometallate anions and radionuclides. Details addressing the design, synthesis and characterization of SAMMS materials specifically designed to sequester actinides, of central importance to the environmental clean-up necessary after 40 years of weapons grade plutonium production, as well as evaluation of their binding affinities and kinetics are presented.

  8. Guided and magnetic self-assembly of tunable magnetoceptive gels

    NASA Astrophysics Data System (ADS)

    Tasoglu, S.; Yu, C. H.; Gungordu, H. I.; Guven, S.; Vural, T.; Demirci, U.

    2014-09-01

    Self-assembly of components into complex functional patterns at microscale is common in nature, and used increasingly in numerous disciplines such as optoelectronics, microfabrication, sensors, tissue engineering and computation. Here, we describe the use of stable radicals to guide the self-assembly of magnetically tunable gels, which we call ‘magnetoceptive’ materials at the scale of hundreds of microns to a millimeter, each can be programmed by shape and composition, into heterogeneous complex structures. Using paramagnetism of free radicals as a driving mechanism, complex heterogeneous structures are built in the magnetic field generated by permanent magnets. The overall magnetic signature of final structure is erased via an antioxidant vitamin E, subsequent to guided self-assembly. We demonstrate unique capabilities of radicals and antioxidants in fabrication of soft systems with heterogeneity in material properties, such as porosity, elastic modulus and mass density; then in bottom-up tissue engineering and finally, levitational and selective assembly of microcomponents.

  9. Self-assembly of DNA-functionalized Colloids

    E-print Network

    Panagiotis E. Theodorakis; Nikolaos G. Fytas; Gerhard Kahl; Christoph Dellago

    2015-03-18

    Colloidal particles grafted with single-stranded DNA (ssDNA) chains can self-assemble into a number of different crystalline structures, where hybridization of the ssDNA chains creates links between colloids stabilizing their structure. Depending on the geometry and the size of the particles, the grafting density of the ssDNA chains, and the length and choice of DNA sequences, a number of different crystalline structures can be fabricated. However, understanding how these factors contribute synergistically to the self-assembly process of DNA-functionalized nano- or micro-sized particles remains an intensive field of research. Moreover, the fabrication of long-range structures due to kinetic bottlenecks in the self-assembly are additional challenges. Here, we discuss the most recent advances from theory and experiment with particular focus put on recent simulation studies.

  10. Nanostructures formed by cyclodextrin covered aminobenzophenones through supramolecular self assembly

    NASA Astrophysics Data System (ADS)

    Rajendiran, N.; Sankaranarayanan, R. K.; Saravanan, J.

    2014-06-01

    Cyclodextrin (? and ?) based nanostructures formed with 2-aminobenzophenone, 3-aminobenzophenone through the supramolecular self assembly are studied by absorption, fluorescence, time-resolved fluorescence, SEM, TEM, FT-IR, DSC, PXRD and 1H NMR. The unequal layer by layer nanosheets and nanoribbons are formed through self assembly of 3ABP/CD inclusion complexes. 2ABP/?-CD complex nanostructures show the self assembly hierarchical thread structure and ?-CD complexes displays a nanobrick structure. The formation of nanostructures are prearranged to Hsbnd O⋯H, NH2⋯O and H2N⋯H intermolecular hydrogen bond between individual complexes. The absorption and fluorescence spectral changes explicit formation of 1:1 inclusion complexes and solvent study demonstrate the ESIPT and TICT present in both molecules. The thermodynamic parameters (?H, ?G and ?S) of 2ABP and 3ABP molecule and the inclusion complexes were determined from semiempirical PM3 calculations.

  11. Self-assembly of DNA-functionalized colloids

    E-print Network

    Panagiotis E. Theodorakis; Nikolaos G. Fytas; Gerhard Kahl; Christoph Dellago

    2015-06-16

    Colloidal particles grafted with single-stranded DNA (ssDNA) chains can self-assemble into a number of different crystalline structures, where hybridization of the ssDNA chains creates links between colloids stabilizing their structure. Depending on the geometry and the size of the particles, the grafting density of the ssDNA chains, and the length and choice of DNA sequences, a number of different crystalline structures can be fabricated. However, understanding how these factors contribute synergistically to the self-assembly process of DNA-functionalized nano- or micro-sized particles remains an intensive field of research. Moreover, the fabrication of long-range structures due to kinetic bottlenecks in the self-assembly are additional challenges. Here, we discuss the most recent advances from theory and experiment with particular focus put on recent simulation studies.

  12. Examples of molecular self-assembly at surfaces

    E-print Network

    Stephen Whitelam

    2014-12-05

    The self-assembly of molecules at surfaces can be caused by a range of physical mechanisms. Assembly can be driven by intermolecular forces, or molecule-surface forces, or both; it can result in structures that are in equilibrium or that are kinetically trapped. Here we review examples of self-assembly at surfaces that have been studied within the User program of the Molecular Foundry at Lawrence Berkeley National Laboratory, focusing on a physical understanding of what causes patterns seen in experiment. Some apparently disparate systems can be described in similar physical terms, indicating that simple factors -- such as the geometry and energy scale of intermolecular binding -- are key to understanding the self-assembly of those systems.

  13. Probing peptide amphiphile self-assembly in blood serum.

    PubMed

    Ghosh, Arijit; Buettner, Christian J; Manos, Aaron A; Wallace, Ashley J; Tweedle, Michael F; Goldberger, Joshua E

    2014-12-01

    There has been recent interest in designing smart diagnostic or therapeutic self-assembling peptide or polymeric materials that can selectively undergo morphological transitions to accumulate at a disease site in response to specific stimuli. Developing approaches to probe these self-assembly transitions in environments that accurately amalgamate the diverse plethora of proteins, biomolecules, and salts of blood is essential for creating systems that function in vivo. Here, we have developed a fluorescence anisotropy approach to probe the pH-dependent self-assembly transition of peptide amphiphile (PA) molecules that transform from spherical micelles at pH 7.4 to nanofibers under more acidic pH's in blood serum. By mixing small concentrations of a Ru(bipy)3(2+)-tagged PA with a Gd(DO3A)-tagged PA having the same lipid-peptide sequence, we showed that the pH dependence of self-assembly is minimally affected and can be monitored in mouse blood serum. These PA vehicles can be designed to transition from spherical micelles to nanofibers in the pH range 7.0-7.4 in pure serum. In contrast to the typical notion of serum albumin absorbing isolated surfactant molecules and disrupting self-assembly, our experiments showed that albumin does not bind these anionic PAs and instead promotes nanofibers due to a molecular crowding effect. Finally, we created a medium that replicates the transition pH in serum to within 0.08 pH units and allows probing self-assembly behavior using conventional spectroscopic techniques without conflicting protein signals, thus simplifying the development pathway from test tube to in vivo experimentation for stimuli-responsive materials. PMID:25347387

  14. The PucC protein of Rhodobacter capsulatus mitigates an inhibitory effect of light-harvesting 2 ? and ? proteins on light-harvesting complex 1

    Microsoft Academic Search

    Paul R. Jaschke; Heidi N. LeBlanc; Andrew S. Lang; J. Thomas Beatty

    2008-01-01

    Rhodobacter capsulatus contains lhaA and pucC genes that have been implicated in light-harvesting complex 1 and 2 (LH1 and LH2) assembly. The proteins encoded by these\\u000a genes, and homologues in other photosynthetic organisms, have been classified as the bacteriochlorophyll delivery (BCD) family\\u000a of the major facilitator superfamily. A new BCD family phylogenetic tree reveals that several PucC, LhaA and Orf428-related

  15. CCMR: Interfacial Study of Self-Assembled Monolayers and Water

    NSDL National Science Digital Library

    Cagle, Courtney

    2010-08-15

    This project is a study of the ultrafast dynamics of water at hydrophobic and hydrophilic surfaces using sum-frequency generation and surface-specific 2D spectroscopy that is being developed in Dr. Poul Petersen’s lab. By determining the dynamics of water, many theories and models of water and interfacial processes can be corrected. This summer, the methods of making hydrophobic self-assembled monolayers was determined. These self-assembled monolayers will be the hydrophobic and hydrophilic interfaces used in the study to look at water.

  16. Self-assembly of flagellin on Au(111) surfaces.

    PubMed

    González Orive, Alejandro; Pissinis, Diego E; Diaz, Carolina; Miñán, Alejandro; Benítez, Guillermo A; Rubert, Aldo; Daza Millone, Antonieta; Rumbo, Martin; Hernández Creus, Alberto; Salvarezza, Roberto C; Schilardi, Patricia L

    2014-11-01

    The adsorption of flagellin monomers from Pseudomonas fluorescens on Au(111) has been studied by Atomic Force Microscopy (AFM), Scanning Tunneling Microscopy (STM), X-ray Photoelectron Spectroscopy (XPS), Surface Plasmon Resonance (SPR), and electrochemical techniques. Results show that flagellin monomers spontaneously self-assemble forming a monolayer thick protein film bounded to the Au surface by the more hydrophobic subunit and exposed to the environment the hydrophilic subunit. The films are conductive and allow allocation of electrochemically active cytochrome C. The self-assembled films could be used as biological platforms to build 3D complex molecular structures on planar metal surfaces and to functionalize metal nanoparticles. PMID:25112916

  17. Structural simulations of nanomaterials self-assembled from ionic macrocycles.

    SciTech Connect

    van Swol, Frank B.; Medforth, Craig John (University of New Mexico, Albuquerque, NM)

    2010-10-01

    Recent research at Sandia has discovered a new class of organic binary ionic solids with tunable optical, electronic, and photochemical properties. These nanomaterials, consisting of a novel class of organic binary ionic solids, are currently being developed at Sandia for applications in batteries, supercapacitors, and solar energy technologies. They are composed of self-assembled oligomeric arrays of very large anions and large cations, but their crucial internal arrangement is thus far unknown. This report describes (a) the development of a relevant model of nonconvex particles decorated with ions interacting through short-ranged Yukawa potentials, and (b) the results of initial Monte Carlo simulations of the self-assembly binary ionic solids.

  18. A Two-Piece Derivative of a Group I Intron RNA as a Platform for Designing Self-Assembling RNA Templates to Promote Peptide Ligation

    PubMed Central

    Tanaka, Takahiro; Furuta, Hiroyuki; Ikawa, Yoshiya

    2012-01-01

    Multicomponent RNA-peptide complexes are attractive from the viewpoint of artificial design of functional biomacromolecular systems. We have developed self-folding and self-assembling RNAs that serve as templates to assist chemical ligation between two reactive peptides with RNA-binding capabilities. The design principle of previous templates, however, can be applied only to limited classes of RNA-binding peptides. In this study, we employed a two-piece derivative of a group I intron RNA from the Tetrahymena large subunit ribosomal RNA (LSU rRNA) as a platform for new template RNAs. In this group I intron-based self-assembling platform, modules for the recognition of substrate peptides can be installed independently from modules holding the platform structure. The new self-assembling platform allows us to expand the repertoire of substrate peptides in template RNA design. PMID:22966423

  19. BULK TITANIUM MICROFLUIDIC NETWORKS FOR PROTEIN SELF-ASSEMBLY STUDIES

    E-print Network

    MacDonald, Noel C.

    BULK TITANIUM MICROFLUIDIC NETWORKS FOR PROTEIN SELF-ASSEMBLY STUDIES E.R. Parker1 , L.S. Hirst2 developed micromachining technique to fabricate microfluidic networks in thin titanium foils. These devices been integrated into the fabrication process in order to minimize protein adsorption to the titanium

  20. THERMAL TRANSPORT IN SELF-ASSEMBLED NANOSTRUCTURES IAN PEARSON BLITZ

    E-print Network

    Braun, Paul

    THERMAL TRANSPORT IN SELF-ASSEMBLED NANOSTRUCTURES BY IAN PEARSON BLITZ THESIS Submitted in partial Understanding of phonon mediated thermal transport properties in nanostructured materials is essential of the thermal transport properties of model organic- inorganic, nanoscopically layered systems for the purpose

  1. Original Papers Biomineralization of a Self-Assembled Extracellular Matrix

    E-print Network

    Meng, Yizhi

    in the extracellular matrix (ECM) of bone cells is crucial to the un- derstanding of bone formation and the development that bone cells, extracellular matrix (ECM), and scaffold material be addressed holistically as a threeOriginal Papers Biomineralization of a Self-Assembled Extracellular Matrix for Bone Tissue

  2. Templated self-assembly for complex pattern fabrication

    E-print Network

    Chang, Jae-Byum

    2014-01-01

    The long-term goal of my Ph.D. study has been controlling the self-assembly of various materials using state-of-the-art nanofabrication techniques. Electron-beam lithography has been used for decades to generate nanoscale ...

  3. Self-Assembly of Globular Protein-Polymer Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Thomas, C. S.; Olsen, B. D.

    2011-03-01

    The self-assembly of globular protein-polymer diblock copolymers into nanostructured phases is demonstrated as an elegant and simple method for structural control in biocatalysis or bioelectronics. In order to fundamentally investigate self-assembly in these complex block copolymer systems, a red fluorescent protein was expressed in E. coli and site-specifically conjugated to a low polydispersity poly(N-isopropyl acrylamide) (PNIPAM) block using thiol-maleimide coupling to form a well-defined model globular protein-polymer diblock. Functional protein materials are obtained by solvent evaporation and solvent annealing above and below the lower critical solution temperature of PNIPAM in order to access different pathways toward self-assembly. Small angle x-ray scattering and microscopy are used to show that the diblock forms lamellar nanostructures and to explore dependence of nanostructure formation on processing conditions. Circular dichroism and UV-vis show that a large fraction of the protein remains in its folded state after conjugation, and wide angle x-ray scattering demonstrates that diblock copolymer self-assembly changes the protein packing symmetry.

  4. Self-assembled zinc oxide nanodots on silicon oxide

    NASA Astrophysics Data System (ADS)

    Giannakopoulos, K.; Boukos, N.; Travlos, A.

    2005-01-01

    Self assembled ZnO nanodots are grown by electron beam evaporation of Zn on thermally oxidized silicon substrates and subsequent annealing in oxygen. Characterization by TEM and EELS shows that the quantum dots are indeed zinc oxide single crystals grown with their c-axis perpendicular to the substrate; their distribution and size depends on the deposition parameters of zinc onto the substrates.

  5. Self-assembled polystyrene microsphere monolayers: Annealing morphology and ellipsometry

    Microsoft Academic Search

    Christian Gigault

    2000-01-01

    Ordered monolayers of polystyrene (PS) microspheres were created on hydrophilic and hydrophobic substrates by convective self-assembly. The size of each domain within the monolayer was often as large as a few hundred sphere diameters. Images of monolayers acquired with an optical microscope during annealing at temperatures below the glass transition temperature Tg of PS were analyzed to assess the order

  6. Casting Metal Nanowires Within Discrete Self-Assembled Peptide Nanotubes

    Microsoft Academic Search

    Meital Reches; Ehud Gazit

    2003-01-01

    Tubular nanostructures are suggested to have a wide range of applications in nanotechnology. We report our observation of the self-assembly of a very short peptide, the Alzheimer's beta-amyloid diphenylalanine structural motif, into discrete and stiff nanotubes. Reduction of ionic silver within the nanotubes, followed by enzymatic degradation of the peptide backbone, resulted in the production of discrete nanowires with a

  7. Guiding 3-D Self Assembly of Nanostructures by DNA Hybridization

    Microsoft Academic Search

    Phillip Rogers; Brad Roberts; David Pine; Eric Michel; Peter Schwartz

    2005-01-01

    The directed three dimensional self-assembly of microstructures and nanostructures through the selective hybridization of DNA is the focus of great interest toward the fabrication of new materials. Single stranded DNA is covalently attached to polystyrene latex microspheres and functions as a ``smart Velcro'' by only bonding to another strand of DNA of complementary sequence. The attached DNA increases the charge

  8. Structural Analysis of Self-Assembling Nanocrystal Superlattices**

    E-print Network

    Wang, Zhong L.

    Structural Analysis of Self-Assembling Nanocrystal Superlattices** By Zhong Lin Wang* 1. This article focuses on the structural analysis of NCSs with an emphasis on electron microscopy related tech properties of nanophase materials are determined by their atomic scale structures, particularly

  9. Electrochemically assisted self-assembly of mesoporous silica thin films

    Microsoft Academic Search

    E. Sibottier; M. Etienne; J. Ghanbaja; A. Walcarius

    2007-01-01

    Supported mesostructured thin films are of major importance for applications in optical, electrochemical and sensing devices. However, good performance is restricted to mesostructured phases ensuring good accessibility from the film surface, which would be straightforward with cylindrical pores oriented normal to the underlying support, but this remains challenging. Here, we demonstrate that electrochemistry is likely to induce self-assembly of surfactant-templated

  10. Chiral perylene diimides: building blocks for ionic self-assembly.

    PubMed

    Echue, Geraldine; Lloyd-Jones, Guy C; Faul, Charl F J

    2015-03-23

    A chiral perylene diimide building block has been prepared based on an amine derivative of the amino acid L-phenylalanine. Detailed studies were carried out into the self-assembly behaviour of the material in solution and the solid state using UV/Vis, circular dichroism (CD) and fluorescence spectroscopy. For the charged building block BTPPP, the molecular chirality of the side chains is translated into the chiral supramolecular structure in the form of right-handed helical aggregates in aqueous solution. Temperature-dependent UV/Vis studies of BTPPP in aqueous solution showed that the self-assembly behaviour of this dye can be well described by an isodesmic model in which aggregation occurs to generate short stacks in a reversible manner. Wide-angle X-ray diffraction studies (WXRD) revealed that this material self-organises into aggregates with ?-? stacking distances typical for ?-conjugated materials. TEM investigations revealed the formation of self-assembled structures of low order and with no expression of chirality evident. Differential scanning calorimetry (DSC) and polarised optical microscopy (POM) were used to investigate the mesophase properties. Optical textures representative of columnar liquid-crystalline phases were observed for solvent-annealed samples of BTPPP. The high solubility, tunable self-assembly and chiral ordering of these materials demonstrate their potential as new molecular building blocks for use in the construction of chiro-optical structures and devices. PMID:25689392

  11. Self-assembling electroactive hydrogels for flexible display technology

    NASA Astrophysics Data System (ADS)

    Jones, Scott L.; Hou Wong, Kok; Thordarson, Pall; Ladouceur, François

    2010-12-01

    We have assessed the potential of self-assembling hydrogels for use in conformal displays. The self-assembling process can be used to alter the transparency of the material to all visible light due to scattering by fibres. The reversible transition is shown to be of low energy by differential scanning calorimetry. For use in technology it is imperative that this transition is controlled electrically. We have thus synthesized novel self-assembling hydrogelator molecules which contain an electroactive group. The well-known redox couple of anthraquinone/anthrahydroquinone has been used as the hydrophobic component for a series of small molecule gelators. They are further functionalized with peptide combinations of L-phenylalanine and glycine to provide the hydrophilic group to complete 'head-tail' models of self-assembling gels. The gelation and electroactive characteristics of the series were assessed. Cyclic voltammetry shows the reversible redox cycle to be only superficially altered by functionalization. Additionally, spectroelectrochemical measurements show a reversible transparency and colour change induced by the redox process.

  12. Self-assembling Nanotube-based Circuits with Collagen Substrates

    Microsoft Academic Search

    Sharlene Coleman; David Elihu; Todd Hoffenberg; Ziyad Jabaji; Don Riggs

    We suggest several assembly strategies for creating a col- lagen substrate capable of supporting a self-assembling car- bon nanotube based circuit. Several strategies are explored and their strengths and weaknesses highlighted. A novel structure consisting of yeast-generated flat collagen strands with 'sticky ends' which tile to form a flat lattice structure is proposed as the support for a carbon nanotube

  13. Automated Tile Design for Self-Assembly Conformations German Terrazas

    E-print Network

    Krasnogor, Natalio

    Automated Tile Design for Self-Assembly Conformations Germ´an Terrazas ASAP Group School of CS and IT University of Nottingham gzt@cs.nott.ac.uk Natalio Krasnogor ASAP Group School of CS and IT University of Nottingham nxk@cs.nott.ac.uk Graham Kendall ASAP Group School of CS and IT University of Nottingham gxk

  14. Automated Self-Assembly Programming Paradigm: A Particle Swarm Realization

    E-print Network

    Aickelin, Uwe

    Krasnogor, and Jon Garibaldi ASAP Group School of Computer Science and Information Technology University Automated Self-Assembly Programming Para- digm (ASAP2 ). We investigated how external environment settings a mathematical model for ASAP2 that allows us to predict time to equilibrium and diversity of generated solutions

  15. Optimal control of electrostatic self-assembly of binary monolayers

    Microsoft Academic Search

    N. V. Shestopalov; G. Henkelman; C. T. Powell; G. J. Rodin

    2009-01-01

    A simple macroscopic model is used to determine an optimal annealing schedule for self-assembly of binary monolayers of spherical particles. The model assumes that a single rate-controlling mechanism is responsible for the formation of spatially ordered structures and that its rate follows an Arrhenius form. The optimal schedule is derived in an analytical form using classical optimization methods. Molecular dynamics

  16. Propagating Waves of Self-Assembly in Organosilane Monolayers

    Microsoft Academic Search

    Jack Douglas; Kirill Efimenko; Daniel Fischer; Fredrick Phelan; Jan Genzer

    2007-01-01

    Wavefronts associated with reaction diffusion and self-assembly processes are ubiquitous in the natural world. While it often claimed that this type of self-sustaining front propagation is well described by mean field `reaction diffusion' or `phase field' models, respectively, it has recently become appreciated from simulations that fluctuation effects can lead to appreciable deviations from the classical mean field theory (MFT)

  17. Shear force surface contrast on self-assembly monolayers

    Microsoft Academic Search

    L. Vaccaro; M.-P. Bernal; F. Marquis-Weible; C. Duschl

    2000-01-01

    Shear force measurements on self-assembly monolayers, which show domains of opposite water affinity, are performed with conventional Al-coated and functionalized near-field probes. Approach curves are discussed, illustrating the influence of the wettability properties of the tip as well as the sample on the oscillation amplitude damping of the probe.

  18. Department of Chemistry "Self-Assembled Soft Materials from Sugar

    E-print Network

    Mark, James E.

    Department of Chemistry "Self-Assembled Soft Materials from Sugar Amphiphiles, and the In Situ.D. (1993) in Chemistry from Kerala University, India under the mentorship of Dr. C.K.S Pillai, Regional is an Associate Professor of Chemistry, the City College of the City University of New York. His research

  19. Functional nanomaterials based on block copolymer self-assembly

    Microsoft Academic Search

    Jin Kon Kim; Seung Yun Yang; Youngmin Lee; Youngsuk Kim

    2010-01-01

    Block copolymers have received considerable attention as a promising platform for the synthesis of nanomaterials and fabrication of nanostructures because of their self-assembling nature to form periodically ordered structures in the nanometer-scale range. By controlling the composition and architecture of individual block components, a variety of nanoscale morphologies can be obtained. After a brief overview of the phase behavior of

  20. Computer Simulations of Block Copolymer Tethered Nanoparticle Self-Assembly

    NSDL National Science Digital Library

    Chan, Elaine

    2006-07-03

    We perform molecular simulations to study the self-assembly of block copolymer tethered cubic nanoparticles. Minimal models of the tethered nanoscale building blocks (NBBs) are utilized to explore the structures arising from self-assembly. We demonstrate that attaching a rigid nanocube to a diblock copolymer affects the typical equilibrium morphologies exhibited by the pure copolymer. Lamellar and cylindrical phases are observed in both systems but not at the corresponding relative copolymer tether block fractions. The effect of nanoparticle geometry on phase behavior is investigated by comparing the self-assembled structures formed by the tethered NBBs with those of their linear ABC triblock copolymer counterparts. The tethered nanocubes exhibit the conventional triblock copolymer lamellar and cylindrical phases when the repulsive interactions between different blocks are symmetric. The rigid and bulky nature of the cube induces interfacial curvature in the tethered NBB phases compared to their linear ABC triblock copolymer counterparts. We compare our results with those structures obtained from diblock copolymer tethered nanospheres to further elucidate the role of cubic nanoparticle geometry on self-assembly.

  1. Self-assembled lipid and membrane protein polyhedral nanoparticles

    E-print Network

    Stowell, Michael

    Self-assembled lipid and membrane protein polyhedral nanoparticles Tamara Bastaa,1 , Hsin-Jui Wub,1 of small conductance (MscS) as a model protein, we prepared mem- brane protein polyhedral nanoparticles to potential applications as drug de- livery carriers or as templates for inorganic nanoparticle formation

  2. Calixarene-encapsulated nanoparticles: self-assembly into functional nanomaterials{

    E-print Network

    Wei, Alexander

    Calixarene-encapsulated nanoparticles: self-assembly into functional nanomaterials{ Alexander Wei coupled, giving rise to unique collective optical or magnetic properties. The self-dependent plasmonic responses, and sub-100 nm Co nanoparticle rings with chiral magnetic states. These nanoparticle

  3. Phenotypic Characterization of Self- Assembling Protein Fragments Using Negative Dominance 

    E-print Network

    Zweifel, Adrienne Elizabeth

    2011-08-08

    Protein oligomerization provides a way for cells to modulate function in vivo. In this study, self-assembling protein fragments from ParC, DnaX, and proteins of unknown function were used to generate phenotypes in a dominant negative manner...

  4. Photoswitched protein adsorption on electrostatically self-assembled azobenzene films.

    PubMed

    Zhang, Jian; Hu, Te; Liu, Yibiao; Ma, Yanxuan; Dong, Jie; Xu, Liping; Zheng, Yudong; Yang, Huai; Wang, Guojie

    2012-08-01

    Photoresponsive polymeric films fabricated by a facile electrostatic self-assembly technique are utilized to switch protein adsorption by light irradiation. The introduction of SiO(2) nanoparticles on the substrate results in a large reversible change of both wettability and protein adsorption. PMID:22618888

  5. Gold nanorods: Synthesis, structural manipulation, and self-assembly

    Microsoft Academic Search

    Bishnu Prasad Khanal

    2009-01-01

    This work describes methods for the synthesis, structural manipulation, and self-assembly of one-dimensional gold nanostructures. The thesis begins with an efficient technique for the synthesis and separation of gold nanorods from a complex mixture, which has been a long standing challenge in the field of inorganic nanocrystals. The key aspect of our approach is the combination of partial oxidative dissolution

  6. pH-directed self-assembling helical peptide conformation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The beta-sheet and alpha-helix peptide conformation are two of the most fundamentally ordered secondary structures found in proteins and peptides. They also give rise to self-assembling motifs that form macromolecular channels and nanostructures. Through design these conformations can yield enhance...

  7. Bicontinuous Surfaces in Self-assembling Amphiphilic Systems

    E-print Network

    Schwarz, Ulrich

    Bicontinuous Surfaces in Self-assembling Amphiphilic Systems Ulrich Schwarz1 and Gerhard Gompper2 1¨orperforschung, Forschungszentrum J¨ulich, D-52425 J¨ulich Abstract. Amphiphiles are molecules which have both hydrophilic due to the hydrophobic effect. The free energy of an amphiphilic system can be written as a functional

  8. Nanostructured gene and drug delivery systems based on molecular self-assembly

    E-print Network

    Wood, Kris Cameron

    2007-01-01

    Molecular self-assembly describes the assembly of molecular components into complex, supramolecular structures governed by weak, non-covalent interactions. In recent years, molecular self-assembly has been used extensively ...

  9. Three-dimensional nanofabrication by electron-beam lithography and directed self-assembly

    E-print Network

    Do, Hyung Wan

    2014-01-01

    In this thesis, we investigated three-dimensional (3D) nanofabrication using electron-beam lithography (EBL), block copolymer (BCP) self-assembly, and capillary force-induced self-assembly. We first developed new processes ...

  10. Tissue engineering by self-assembly and bio-printing of living cells.

    PubMed

    Jakab, Karoly; Norotte, Cyrille; Marga, Francoise; Murphy, Keith; Vunjak-Novakovic, Gordana; Forgacs, Gabor

    2010-06-01

    Biofabrication of living structures with desired topology and functionality requires the interdisciplinary effort of practitioners of the physical, life and engineering sciences. Such efforts are being undertaken in many laboratories around the world. Numerous approaches are pursued, such as those based on the use of natural or artificial scaffolds, decellularized cadaveric extracellular matrices and, most lately, bioprinting. To be successful in this endeavor, it is crucial to provide in vitro micro-environmental clues for the cells resembling those in the organism. Therefore, scaffolds, populated with differentiated cells or stem cells, of increasing complexity and sophistication are being fabricated. However, no matter how sophisticated scaffolds are, they can cause problems stemming from their degradation, eliciting immunogenic reactions and other a priori unforeseen complications. It is also being realized that ultimately the best approach might be to rely on the self-assembly and self-organizing properties of cells and tissues and the innate regenerative capability of the organism itself, not just simply prepare tissue and organ structures in vitro followed by their implantation. Here we briefly review the different strategies for the fabrication of three-dimensional biological structures, in particular bioprinting. We detail a fully biological, scaffoldless, print-based engineering approach that uses self-assembling multicellular units as bio-ink particles and employs early developmental morphogenetic principles, such as cell sorting and tissue fusion. PMID:20811127

  11. Light-harvesting function of beta -carotene inside carbon nanotubes explored by femtosecond absorption spectroscopy

    Microsoft Academic Search

    Kenta Abe; Daisuke Kosumi; Kazuhiro Yanagi; Yasumitsu Miyata; Hiromichi Kataura; Masayuki Yoshizawa

    2008-01-01

    Single-walled carbon nanotubes (SWCNTs) encapsulating beta -carotene are attractive components for enhancing optical functionalities of SWCNTs. We have investigated ultrafast dynamics of light-harvesting function of beta -carotene. The relaxation kinetics of beta -carotene is faster in SWCNTs than in nonpolar solvent. The absorbance change due to SWCNTs increases with the encapsulation because of excited energy transfer from beta -carotene. The

  12. Increased light harvesting in dye-sensitized solar cells with energy relay dyes

    E-print Network

    McGehee, Michael

    Increased light harvesting in dye-sensitized solar cells with energy relay dyes Brian E. Hardin1 factors. However, dye-sensitized solar cells do not completely absorb all of the photons from the visible pathway to develop more efficient dye-sensitized solar cells. D ye-sensitized solar cells (DSCs) work

  13. Ultrafast Energy-Electron Transfer Cascade in a Multichromophoric Light-Harvesting Molecular Square

    E-print Network

    van Stokkum, Ivo

    Ultrafast Energy-Electron Transfer Cascade in a Multichromophoric Light-Harvesting Molecular Square, 2004; E-mail: wuerthner@chemie.uni-wuerzburg.de; williams@science.uva.nl Abstract: A molecular square with the closely packed structure of 20 chromophoric units, indicate that we can consider the molecular square

  14. Discrete Redox Signaling Pathways Regulate Photosynthetic Light-Harvesting and Chloroplast Gene

    E-print Network

    Allen, John F.

    of absorbed light energy distribution by phosphorylation of light-harvesting complex II (LHC II). Chloroplast fluorescence emission spectra, while room-temperature chlorophyll fluorescence emission transients from Arabidopsis leaves are perturbed by inactivation of CSK. The results indicate indirect, pleiotropic effects

  15. Optimization of light harvesting and photoprotection: molecular mechanisms and physiological consequences

    PubMed Central

    Horton, Peter

    2012-01-01

    The distinctive lateral organization of the protein complexes in the thylakoid membrane investigated by Jan Anderson and co-workers is dependent on the balance of various attractive and repulsive forces. Modulation of these forces allows critical physiological regulation of photosynthesis that provides efficient light-harvesting in limiting light but dissipation of excess potentially damaging radiation in saturating light. The light-harvesting complexes (LHCII) are central to this regulation, which is achieved by phosphorylation of stromal residues, protonation on the lumen surface and de-epoxidation of bound violaxanthin. The functional flexibility of LHCII derives from a remarkable pigment composition and configuration that not only allow efficient absorption of light and efficient energy transfer either to photosystem II or photosystem I core complexes, but through subtle configurational changes can also exhibit highly efficient dissipative reactions involving chlorophyll–xanthophyll and/or chlorophyll–chlorophyll interactions. These changes in function are determined at a macroscopic level by alterations in protein–protein interactions in the thylakoid membrane. The capacity and dynamics of this regulation are tuned to different physiological scenarios by the exact protein and pigment content of the light-harvesting system. Here, the molecular mechanisms involved will be reviewed, and the optimization of the light-harvesting system in different environmental conditions described. PMID:23148272

  16. Atomistic study of energy funneling in the light-harvesting complex of green sulfur bacteria

    E-print Network

    Joonsuk Huh; Semion K. Saikin; Jennifer C. Brookes; Stéphanie Valleau; Takatoshi Fujita; Alán Aspuru-Guzik

    2013-11-22

    Phototrophic organisms such as plants, photosynthetic bacteria and algae use microscopic complexes of pigment molecules to absorb sunlight. Within the light-harvesting complexes, which frequently have several functional and structural subunits, the energy is transferred in the form of molecular excitations with very high efficiency. Green sulfur bacteria are considered to be amongst the most efficient light-harvesting organisms. Despite multiple experimental and theoretical studies of these bacteria the physical origin of the efficient and robust energy transfer in their light-harvesting complexes is not well understood. To study excitation dynamics at the systems level we introduce an atomistic model that mimics a complete light-harvesting apparatus of green sulfur bacteria. The model contains approximately 4000 pigment molecules and comprises a double wall roll for the chlorosome, a baseplate and six Fenna-Matthews-Olson trimer complexes. We show that the fast relaxation within functional subunits combined with the transfer between collective excited states of pigments can result in robust energy funneling. Energy transfer is robust on the initial excitation conditions and temperature changes. Moreover, the same mechanism describes the coexistence of multiple timescales of excitation dynamics frequently observed in ultrafast optical experiments. While our findings support the hypothesis of supertransfer, the model reveals energy transport through multiple channels on different length scales.

  17. Energy Transfer from Quantum Dots to Metal-Organic Frameworks for Enhanced Light Harvesting

    E-print Network

    to natural porphyrin-type light-harvesting and photosynthesis pigments,12 porphyrin-based MOFs might be expected to mimic important aspects of natural photo- synthetic systems. Our previous studies have shown migration suggest promising applica- tions of MOFs, superior to monomer dye molecules, as efficient light

  18. Surface plasmon resonance of nano particles for spectroscopic bio-imaging and light-harvesting

    Microsoft Academic Search

    Sailing He

    Gold nanorods (GNRs) exhibit localized surface plasmon resonance (SPR) at visible and near-infrared wavebands, and the associated longitudinal SPR band is tunable and sensitive to the size, shape, density, and the environment of the GNRs. The properties are utilized for cellular targeting\\/imaging, bio-sensing and medical therapy. Light-harvesting with an optical nano antenna will also be presented.

  19. The importance of PS I chlorophyll red forms in light-harvesting by leaves

    Microsoft Academic Search

    Andrea Rivadossi; Giuseppe Zucchelli; Flavio M. Garlaschi; Robert C. Jennings

    1999-01-01

    We have investigated the importance of the long wavelength absorbing spectral forms (red forms) of Photosystem I in photosynthetic light harvesting by leaves. To this end leaf spectra were simulated by using a linear combination of absorption (OD) spectra of purified Photosystem I, Photosystem II and LHC II, multiplied by an empirical multiple scattering chloroplast\\/leaf conversion function. In this way

  20. A pigment-binding protein essential for regulation of photosynthetic light harvesting

    Microsoft Academic Search

    Xiao-Ping Li; Olle Bjorkman; Connie Shih; Arthur R. Grossman; Magnus Rosenquist; Stefan Jansson; Krishna K. Niyogi

    2000-01-01

    Photosynthetic light harvesting in plants is regulated in response to changes in incident light intensity. Absorption of light that exceeds a plant's capacity for fixation of CO2 results in thermal dissipation of excitation energy in the pigment antenna of photosystem II by a poorly understood mechanism. This regulatory process, termed nonphotochemical quenching, maintains the balance between dissipation and utilization of

  1. Studying the Effect of Light Quality on the Size of the Photosystem II Light Harvesting Complex

    ERIC Educational Resources Information Center

    Muhoz, Romualdo; Quiles, Maria J.

    2003-01-01

    In this article the effect of light quality on the size of the photosystem II (PSII) light harvesting complex (LHCII) is studied by measuring the chlorophyll fluorescence emitted by leaf sections of oat ("Avena sativa," var. Prevision) plants previously treated with either white light or with light filtered through blue, green, red or farred…

  2. Plasmon Enhanced Light Harvesting: Multiscale Modeling of the FMO Protein Coupled with Gold Nanoparticles.

    PubMed

    Andreussi, Oliviero; Caprasecca, Stefano; Cupellini, Lorenzo; Guarnetti-Prandi, Ingrid; Guido, Ciro A; Jurinovich, Sandro; Viani, Lucas; Mennucci, Benedetta

    2015-05-28

    Plasmonic systems, such as metal nanoparticles, are becoming increasingly important in spectroscopies and devices because of their ability to enhance, even by several orders of magnitude, the photophysical properties of neighboring systems. In particular, it has been shown both theoretically and experimentally that combining nanoplasmonic devices with natural light-harvesting proteins substantially increases the fluorescence and absorption properties of the system. This kind of biohybrid device can have important applications in the characterization and design of efficient light-harvesting systems. In the present work, the FMO light-harvesting protein was combined with gold nanoparticles of different sizes, and its photophysical properties were characterized using a multiscale quantum-mechanical classical-polarizable and continuum model (QM/MMPol/PCM). By optimal tuning of the plasmon resonance of the metal nanoparticles, fluorescence enhancements of up to 2 orders of magnitude were observed. Orientation effects were found to be crucial: amplifications by factors of up to 300 were observed for the absorption process, while the radiative decay of the emitting state increased at most by a factor of 10, mostly as a result of poor alignment of the emitting state with the considered metal aggregates. Despite being a limiting factor for high-fluorescence-enhancement devices, the strong orientation dependence may represent an important feature of the natural light-harvesting system that could allow selective enhancement of a specific excited state of the complex. PMID:25419640

  3. Organization of the Bacterial Light-Harvesting Apparatus Rationalized by Exciton Transport Optimization

    E-print Network

    Harel, Elad

    2011-01-01

    Photosynthesis, the process by which energy from sunlight drives cellular metabolism, relies on a unique organization of light-harvesting and reaction center complexes. Recently, the organization of light-harvesting LH2 complexes and dimeric reaction center-light harvesting I-PufX (RC-LH1-PufX) core complexes in membranes of purple non-sulfur bacteria was revealed by atomic force microscopy (AFM)1. Here, we report that the structure of LH2 and its organization within the membrane can be largely rationalized by a simple physical model that relies primarily on exciton transfer optimization. The process through which the light-harvesting complexes transfer excitation energy has been recognized to incorporate both coherent and incoherent processes mediated by the surrounding protein environment. Using the Haken-Strobl model, we show that the organization of the complexes in the membrane can be almost entirely explained by simple electrostatic considerations and that quantum effects act primarily to enforce robust...

  4. Lutein epoxide cycle, light harvesting and photoprotection in species of the tropical tree genus Inga

    Microsoft Academic Search

    SHIZUE MATSUBARA; G. HEINRICH KRAUSE; MARTIN SELTMANN; AURELIO VIRGO; THOMAS A. KURSAR; PETER JAHNS; KLAUS WINTER

    2008-01-01

    Dynamics and possible function of the lutein epoxide (Lx) cycle, that is, the reversible conversion of Lx to lutein (L) in the light-harvesting antennae, were investigated in leaves of tropical tree species. Photosynthetic pigments were quanti- fied in nine Inga species and species from three other genera. In Inga, Lx levels were high in shade leaves (mostly above 20 mmol

  5. Molecular basis of photoprotection and control of photosynthetic light-harvesting

    Microsoft Academic Search

    Andrew A. Pascal; Zhenfeng Liu; Koen Broess; Bart van Oort; Herbert van Amerongen; Chao Wang; Peter Horton; Bruno Robert; Wenrui Chang; Alexander Ruban

    2005-01-01

    In order to maximize their use of light energy in photosynthesis, plants have molecules that act as light-harvesting antennae, which collect light quanta and deliver them to the reaction centres, where energy conversion into a chemical form takes place. The functioning of the antenna responds to the extreme changes in the intensity of sunlight encountered in nature. In shade, light

  6. Structural and functional organization of the peripheral light-harvesting system in Photosystem I

    Microsoft Academic Search

    Alexander N. Melkozernov; Robert E. Blankenship

    2005-01-01

    This review centers on the structural and functional organization of the light-harvesting system in the peripheral antenna of Photosystem I (LHC I) and its energy coupling to the Photosystem I (PS I) core antenna network in view of recently available structural models of the eukaryotic Photosystem I–LHC I complex, eukaryotic LHC II complexes and the cyanobacterial Photosystem I core. A

  7. Highly efficient nonradiative energy transfer mediated light harvesting in water using aqueous CdTe quantum dot antennas.

    PubMed

    Mutlugun, Evren; Samarskaya, Olga; Ozel, Tuncay; Cicek, Neslihan; Gaponik, Nikolai; Eychmüller, Alexander; Demir, Hilmi Volkan

    2010-05-10

    We present light harvesting of aqueous colloidal quantum dots to nonradiatively transfer their excitonic excitation energy efficiently to dye molecules in water, without requiring ligand exchange. These as-synthesized CdTe quantum dots that are used as donors to serve as light-harvesting antennas are carefully optimized to match the electronic structure of Rhodamine B molecules used as acceptors for light harvesting in aqueous medium. By varying the acceptor to donor concentration ratio, we measure the light harvesting factor, along with substantial lifetime modifications of these water-soluble quantum dots, from 25.3 ns to 7.2 ns as a result of their energy transfer with efficiency levels up to 86%. Such nonradiative energy transfer mediated light harvesting in aqueous medium holds great promise for future quantum dot multiplexed dye biodetection systems. PMID:20588924

  8. Hierarchical self-assembly: Self-organized nanostructures in a nematically ordered matrix of self-assembled polymeric chains

    NASA Astrophysics Data System (ADS)

    Mubeena, Shaikh; Chatterji, Apratim

    2015-03-01

    We report many different nanostructures which are formed when model nanoparticles of different sizes (diameter ?n) are allowed to aggregate in a background matrix of semiflexible self-assembled polymeric wormlike micellar chains. The different nanostructures are formed by the dynamical arrest of phase-separating mixtures of micellar monomers and nanoparticles. The different morphologies obtained are the result of an interplay of the available free volume, the elastic energy of deformation of polymers, the density (chemical potential) of the nanoparticles in the polymer matrix, and, of course, the ratio of the size of self-assembling nanoparticles and self-avoidance diameter of polymeric chains. We have used a hybrid semi-grand-canonical Monte Carlo simulation scheme to obtain the (nonequilibrium) phase diagram of the self-assembled nanostructures. We observe rodlike structures of nanoparticles which get self-assembled in the gaps between the nematically ordered chains, as well as percolating gel-like network of conjoined nanotubes. We also find a totally unexpected interlocked crystalline phase of nanoparticles and monomers, in which each crystal plane of nanoparticles is separated by planes of perfectly organized polymer chains. We identified the condition which leads to such interlocked crystal structure. We suggest experimental possibilities of how the results presented in this paper could be used to obtain different nanostructures in the laboratory.

  9. Hierarchical self-assembly: Self-organized nanostructures in a nematically ordered matrix of self-assembled polymeric chains.

    PubMed

    Mubeena, Shaikh; Chatterji, Apratim

    2015-03-01

    We report many different nanostructures which are formed when model nanoparticles of different sizes (diameter ?n) are allowed to aggregate in a background matrix of semiflexible self-assembled polymeric wormlike micellar chains. The different nanostructures are formed by the dynamical arrest of phase-separating mixtures of micellar monomers and nanoparticles. The different morphologies obtained are the result of an interplay of the available free volume, the elastic energy of deformation of polymers, the density (chemical potential) of the nanoparticles in the polymer matrix, and, of course, the ratio of the size of self-assembling nanoparticles and self-avoidance diameter of polymeric chains. We have used a hybrid semi-grand-canonical Monte Carlo simulation scheme to obtain the (nonequilibrium) phase diagram of the self-assembled nanostructures. We observe rodlike structures of nanoparticles which get self-assembled in the gaps between the nematically ordered chains, as well as percolating gel-like network of conjoined nanotubes. We also find a totally unexpected interlocked crystalline phase of nanoparticles and monomers, in which each crystal plane of nanoparticles is separated by planes of perfectly organized polymer chains. We identified the condition which leads to such interlocked crystal structure. We suggest experimental possibilities of how the results presented in this paper could be used to obtain different nanostructures in the laboratory. PMID:25871136

  10. Construction Of Micro- And Nanoporous Hydrogels Via Designed Diblock Copolypeptide Self-Assembly And Oligopeptide Self-Assembly

    NASA Astrophysics Data System (ADS)

    Pochan, Darrin; Deming, Tim; Schneider, Joel

    2002-03-01

    The design, synthesis, and self-assembly of polypeptides as synthetic materials that possess the ability to aggregate and/or “fold” into specifically defined, a priori designed, functional nanostructures is being pursued via two avenues. First, synthetic block copolypeptides will be discussed that are observed to form novel hydrogels with structural and biological properties tailorable by the choice of amino acid (and consequent secondary structure) in the respective blocks. Specifically ionic, amphiphilic diblocks have been designed for tissue engineering hydrogels on assembly in aqueous solution. A bicontinuous morphology is observed at both the nanoscale and microscale. Second, de novo designed oligopeptides that undergo specific folding events triggered by pH, preceding or concurrent with self-assembly, will be discussed. Specifically, the ability of small (20 amino acid residues) molecules to produce relatively very large (approximately 100 micron diameter) spheres and tubes in additino to hydrogels via a hierarchical self-assembly process will be discussed. The assembled oligopeptides have the added design attribute of being responsive to pH, unfolding/disassembling at pH below 6. Both classes of peptide-based self-assembled materials were characterized via laser scanning confocal and cryotransmission electron microscopy combined with small angle neutron and x-ray scattering.

  11. Heirarchical Self Assembly: Self Organized nano-structures in a nematically ordered matrix of self assembled polymeric chains

    E-print Network

    Shaikh Mubeena; Apratim Chatterji

    2014-12-04

    We report many different nano-structures which are formed when model nano-particles of different sizes (diameter {\\sigma} n ) are allowed to aggregate in a background matrix of semi-flexible self assembled polymeric worm like micellar chains. The different nano-structures are formed by the dynamical arrest of phase-separating mixtures of micellar monomers and nano-particles. The different mor- phologies obtained are the result of an interplay of the available free volume, the elastic energy of deformation of polymers, the density (chemical potential) of the nano-particles in the polymer ma- trix and, of course, the ratio of the size of self assembling nano-particles and self avoidance diameter of polymeric chains. We have used a hybrid semi-grand canonical Monte Carlo simulation scheme to obtain the (non-equilibrium) phase diagram of the self-assembled nano-structures. We observe rod-like structures of nano-particles which get self assembled in the gaps between the nematically ordered chains as well as percolating gel-like network of conjoined nanotubes. We also find a totally unexpected interlocked crystalline phase of nano-particles and monomers, in which each crytal plane of nanoparticles is separated by planes of perfectly organized polymer chains. We identified the con- dition which leads to such interlocked crystal structure. We suggest experimental possibilities of how the results presented in this paper could be used to obtain different nano-structures in the lab.

  12. Non-degenerate magnetic alignment of self-assembled mesophases Pawel W. Majewski* Chinedum O. Osuji

    E-print Network

    Haller, Gary L.

    to understanding the mechanisms via which self-assembly or self-assembled structures in soft materials may magnetic degeneracy that may be present in the material. The use of non-ionic mesophases is noteworthyNon-degenerate magnetic alignment of self-assembled mesophases Pawel W. Majewski* Chinedum O. Osuji

  13. Self-Assembly of Mesoscale Isomers: The Role of Pathways and Degrees of Freedom

    E-print Network

    Menon, Govind

    Self-Assembly of Mesoscale Isomers: The Role of Pathways and Degrees of Freedom Shivendra Pandey1 geometric path sampling and a mesoscale experimental model to investigate the self-assembly of a model. Citation: Pandey S, Johnson D, Kaplan R, Klobusicky J, Menon G, et al. (2014) Self-Assembly of Mesoscale

  14. Neutralization of Polyatomic Ions at Self-Assembled Monolayer Surfaces before and after Electrodeposition of

    E-print Network

    Wysocki, Vicki H.

    Neutralization of Polyatomic Ions at Self-Assembled Monolayer Surfaces before and after: October 8, 1997X Self-assembled monolayer (SAM) films chemisorbed onto polycrystalline gold substrates sites that expose gold. Self-assembled monolayer (SAM) films of alkanethi- olates chemisorbed onto gold

  15. Formation and Structure of Self-Assembled Monolayers of Alkanethiolates on Palladium

    E-print Network

    Prentiss, Mara

    Formation and Structure of Self-Assembled Monolayers of Alkanethiolates on Palladium J. Christopher produces well-organized, self-assembled monolayers. The organization of the alkane chains in the monolayer of self-assembled monolayers (SAMs) of n-alkanethiolates formed by the adsorption of n

  16. Orientation Determination of 2-and 4-Chlorobenzylmercaptan Self-Assembled Monolayers

    E-print Network

    Goodman, Wayne

    Orientation Determination of 2- and 4-Chlorobenzylmercaptan Self-Assembled Monolayers Using to probe the outermost electronic structure of two similar self-assembled monolayers (SAMs), 2- and 4 extending outwardly from the surface. Self-assembled monolayers (SAMs) have considerable potential for use

  17. Alkylsiloxane self-assembled monolayer formation guided by nanoimprinted Si and SiO2 templates

    E-print Network

    Alkylsiloxane self-assembled monolayer formation guided by nanoimprinted Si and SiO2 templates Amir; accepted 21 August 2006; published online 12 October 2006 Alkylsiloxane self-assembled monolayers SAMs were nanoscaled regions.3 However, liquid-phase growth of a self-assembled monolayer on a nanopatterned surface

  18. Effect of Solvents on Interactions between Hydrophobic Self-Assembled Monolayers

    E-print Network

    Kokkoli, Efie

    Effect of Solvents on Interactions between Hydrophobic Self-Assembled Monolayers Efrosini Kokkoli: solvents; adhesion; self-assembled monolayers; wet- ting properties; atomic force microscope. INTRODUCTION chosen to work with self-assembled monolayers (SAMs) of hexadecanethiol, which satisfy both criteria

  19. Rapid Evaluation and Screening of Interfacial Reactions on Self-Assembled Monolayers

    E-print Network

    Mrksich, Milan

    Rapid Evaluation and Screening of Interfacial Reactions on Self-Assembled Monolayers Jing Li chemical reactions for elaborating the structures of self-assembled monolayers (SAMs) of alkanethiolates, and therefore the properties, of self-assembled monolayers of alkanethiolates on gold and to introduce label

  20. Comparison of the Mechanical Properties of Self-Assembled Langmuir Monolayers of Nanoparticles and Phospholipids

    E-print Network

    Jaeger, Heinrich M.

    Comparison of the Mechanical Properties of Self-Assembled Langmuir Monolayers of Nanoparticles with hydrophobic capping ligands and amphiphilic phospholipids are both found to self-assemble into monolayer films of the nanoparticle film. INTRODUCTION Amphiphilic surfactants spontaneously self-assemble into Langmuir monolayers

  1. Biosensors and Bioelectronics 22 (2007) 17231732 Self-assembled monolayers of polythiophene conductive polymers improve

    E-print Network

    Matsuoka, Yoky

    2007-01-01

    Biosensors and Bioelectronics 22 (2007) 1723­1732 Self-assembled monolayers of polythiophene polymer; Neural interface; Neural prosthesis; Self-assembled monolayer 1. Introduction The prospect and biocompatibility of electrodes for neural prostheses. We present here a new type of coating, based on mixed self-assembled

  2. Self-Assembled Fullerene-Derivative Monolayers on a Gold Substrate Using Phenanthroline-Au Interactions

    E-print Network

    Tao, Nongjian

    Self-Assembled Fullerene-Derivative Monolayers on a Gold Substrate Using Phenanthroline-ordered monolayers.5a A much less explored area in the field of self-assembly is the use of bipyridine (bpy of the final product, phenanthrolyl[60]fullerene, compound 1, in a 43% isolated yield. Spontaneous self-assembly

  3. Large-scale molecular dynamics simulations of alkanethiol self-assembled monolayers

    E-print Network

    Southern California, University of

    Large-scale molecular dynamics simulations of alkanethiol self-assembled monolayers Satyavani of self-assembled alkanethiol monolayer systems have been carried out using an all-atom model involving at high temperatures. © 2004 American Institute of Physics. DOI: 10.1063/1.1775779 I. INTRODUCTION Self-assembled

  4. Self-Assembled Monolayers for MALDI-TOF Mass Spectrometry for Immunoassays of Human Protein

    E-print Network

    Mrksich, Milan

    Self-Assembled Monolayers for MALDI-TOF Mass Spectrometry for Immunoassays of Human Protein that combines self-assembled monolayers with matrix-assisted laser desorption/ioniza- tion time-of-flight mass- mobilized on a self-assembled monolayer (SAM). This strategy was used to detect multiple protein antigens

  5. Molecular Electrostatics of Conjugated Self-Assembled Monolayers on Au(111) Using Electrostatic Force

    E-print Network

    Reifenberger, Ronald G.

    Molecular Electrostatics of Conjugated Self-Assembled Monolayers on Au(111) Using Electrostatic: April 5, 2002 The electrostatic potential produced by a variety of self-assembled monolayers on Au(111 electron acceptor. In this case, the surface potential produced by the self-assembled monolayer was found

  6. Design of Self-Assembled Monolayers That Release Attached Groups Using Applied Electrical Potentials

    E-print Network

    Mrksich, Milan

    Letters Design of Self-Assembled Monolayers That Release Attached Groups Using Applied ElectricalV and a reduction wave at -125 mV for the reversible oxidation of the catechol group. Self-assembled monolayers, Chicago, Illinois 60637 Received September 15, 1997X This Letter describes the design of a self-assembled

  7. Self-Assembled Monolayers deposition in Supercritical Carbon Dioxide Paper ID: 114 (Page 1 / 4)

    E-print Network

    Paris-Sud XI, Université de

    Self-Assembled Monolayers deposition in Supercritical Carbon Dioxide Paper ID: 114 (Page 1 / 4 -------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------- Self-Assembled Monolayers deposition in Supercritical Carbon Dioxide L. Rabbia1 , V. Perrut1 , P. Pons2 ----------------------------------------------------------------------------------------------------------------- Abstract Self-Assembled Monolayers of organic molecules have been successfully deposited onto wafer surface

  8. Defects in Microcontact-Printed and Solution-Grown Self-Assembled Monolayers

    E-print Network

    Parikh, Atul N.

    Letters Defects in Microcontact-Printed and Solution-Grown Self-Assembled Monolayers A. S of microcontact-printed self-assembled monolayers is significant for a number of technological applications, a method for patterning multi- component self-assembled monolayers developed at Har- vard,1

  9. Formation and removal of alkylthiolate self-assembled monolayers on gold in aqueous solutions

    E-print Network

    Roukes, Michael L.

    Formation and removal of alkylthiolate self-assembled monolayers on gold in aqueous solutions device by modifying the surface substrate with thin films and monolayers.1 Self-assembled monolayers adsorption stage is slower as the alkylthiolates self- assemble into a more organized and insulated film.20

  10. Surface vibrations in alkanethiol self-assembled monolayers of varying chain length

    E-print Network

    Sibener, Steven

    Surface vibrations in alkanethiol self-assembled monolayers of varying chain length A. W. Rosenbaum phase self-assembled monolayers on Au 111 was studied. We have examined the low-energy vibrational.1063/1.1643353 I. INTRODUCTION Self-assembled monolayers SAMs formed from or- ganic thiols on Au 111 have been

  11. Accepted Manuscript Title: Adjacent Assembly of Self-Assembled Monolayers for

    E-print Network

    Hone, James

    Accepted Manuscript Title: Adjacent Assembly of Self-Assembled Monolayers for the Construction.H. Lee, L. Amar, S. Ghassemi, J. Hone, Adjacent Assembly of Self-Assembled Monolayers interesting techniques is based on self-assembled monolayers (SAMs) [7]. Those have been greatly demonstrated

  12. Selective immobilization of proteins to self-assembled monolayers presenting active site-directed

    E-print Network

    Mrksich, Milan

    Selective immobilization of proteins to self-assembled monolayers presenting active site to a self-assembled monolayer presenting a phosphonate ligand and the subsequent displace- ment reaction for the selective and irreversible immobilization of proteins to self-assembled monolayers of alkanethiolates

  13. Adsorption of Proteins to Hydrophobic Sites on Mixed Self-Assembled Monolayers

    E-print Network

    Prentiss, Mara

    Adsorption of Proteins to Hydrophobic Sites on Mixed Self-Assembled Monolayers Emanuele Ostuni self-assembled monolayers of two alkanethiolates (-S(CH2)11(OCH2CH2)6OR, R ) a hydrophobic group to the ad- sorption of proteins. We used mixed self-assembled monolayers (SAMs) of alkanethiolates

  14. Significantly improved stability of n-octadecyltrichlorosilane self-assembled monolayer by plasma pretreatment on mica

    E-print Network

    Boo, Jin-Hyo

    Significantly improved stability of n-octadecyltrichlorosilane self-assembled monolayer by plasma been well known that plasma pretreatment can stabilize the hydrocarbon silane monolayer self-assembled-octadecyltrichlorosilane (OTS) monolayers were self-assembled on both untreated and plasma-treated mica surfaces

  15. Coexistence of the (23 3) Au(111) Reconstruction and a Striped Phase Self-Assembled Monolayer

    E-print Network

    Sibener, Steven

    Coexistence of the (23 × 3) Au(111) Reconstruction and a Striped Phase Self-Assembled Monolayer S deconstructs following formation of a thiolate self-assembled monolayer, but our results suggest Self-assembled monolayers (SAMs) based on a sulfur headgroup have been widely studied using numerous

  16. Surface Stress, Kinetics, and Structure of Alkanethiol Self-Assembled Monolayers

    E-print Network

    Grütter, Peter

    Surface Stress, Kinetics, and Structure of Alkanethiol Self-Assembled Monolayers Michel Godin,*, P during the formation of alkanethiol self-assembled monolayers (SAMs) on gold from the vapor phase produces high-quality self-assembled monolayers. An induced compressive surface stress of 15.9 ( 0.6 N

  17. Symmetry breaking in self-assembled monolayers on solid surfaces. II. Anisotropic substrate elasticity

    E-print Network

    Lu, Wei

    Symmetry breaking in self-assembled monolayers on solid surfaces. II. Anisotropic substrate On a solid surface a monolayer mixture may separate into two phases. The phases can self-assemble for a decade that a monolayer mixture on a solid surface may self-assemble into nanoscale phase patterns

  18. Alkanethiol self-assembled monolayers as the dielectric of capacitors with nanoscale thickness

    E-print Network

    Prentiss, Mara

    Alkanethiol self-assembled monolayers as the dielectric of capacitors with nanoscale thickness February 1998 Alkanethiol self-assembled monolayers SAMs on a mercury surface are used to build a junction of 6 MV/cm. © 1998 American Institute of Physics. S0003-6951 98 03114-3 Alkanethiol self-assembled

  19. Computing surface dipoles and potentials of self-assembled monolayers from first principles

    E-print Network

    Shapira, Yoram

    Computing surface dipoles and potentials of self-assembled monolayers from first principles Amir reserved. Keywords: Density functional theory; Dipole layer; Work function; Self-assembled monolayers 1 principles calculations of surface dipoles and potentials in general, and surface-adsorbed self- assembled

  20. Self-Assembled Monolayers and Multilayered Stacks of Lyotropic Chromonic Liquid Crystalline Dyes with

    E-print Network

    Lavrentovich, Oleg D.

    Self-Assembled Monolayers and Multilayered Stacks of Lyotropic Chromonic Liquid Crystalline Dyes technologies of molecular self-assembly use noncovalent association of molecules into aggregates of nanometer size.1 One of the proven strategies is layer- by-layer deposition of charged species that self-assemble

  1. Self-assembled monolayers of benzylmercaptan and para-cyanobenzylmercaptan on gold: surface infrared

    E-print Network

    Pfeifer, Holger

    Self-assembled monolayers of benzylmercaptan and para-cyanobenzylmercaptan on gold: surface as an Advance Article on the web 5th March 2010 DOI: 10.1039/b923628g Self-assembled monolayers (SAMs) on gold for the structural and spectroscopic characterization of self-assembled monolayers (SAMs) which have important

  2. Molecular Self-Assembly of Jointed Molecules on a Metallic Substrate: From Single Molecule to Monolayer**

    E-print Network

    Paris-Sud XI, Université de

    Molecular Self-Assembly of Jointed Molecules on a Metallic Substrate: From Single Molecule microscopy, molecular mechanics calculations, self-assembly. 1 hal-00080899,version1-21Jun2006 Author molecules adsorbed on metallic substrates. In this situation, self-assembled structures can be understood

  3. Rearrangements in an Alkylthiolate Self-Assembled Monolayer Using Electrostatic Interactions between Nanoscale Asperity and

    E-print Network

    Paramonov, Pavel B.

    Rearrangements in an Alkylthiolate Self-Assembled Monolayer Using Electrostatic Interactions. The rearrangements suggest a novel and general approach for nanoscale architecture in self-assembled systems of semiconductors4 and dip-pen lithography5), and controllable dielectric surface reshaping.6 Self-assembled mono

  4. Self-Assembly of Carbon Nanotubes** By Hideo Shimoda, Sue J. Oh, Huai Zhi Geng,

    E-print Network

    /water/substrate triple line Fig. 2. A schematic illustration of the self-assembly process. Short SWNTs were dispersedSelf-Assembly of Carbon Nanotubes** By Hideo Shimoda, Sue J. Oh, Huai Zhi Geng, Russel J. Walker, Xia Bin Zhang, Laurie E. McNeil, and Otto Zhou* Self-assembly is an efficient and often preferred

  5. Self-Organization in Coordination-Driven Self-Assembly

    PubMed Central

    Northrop, Brian H.; Zheng, Yao-Rong; Chi, Ki-Whan; Stang, Peter J.

    2009-01-01

    Conspectus Self-assembly allows for the preparation of highly complex molecular and supramolecular systems from relatively simple starting materials. Typically, self-assembled supramolecules are constructed by combining complementary pairs of two highly symmetric molecular components, thus limiting the chances of forming unwanted side products. Combining asymmetric molecular components or multiple complementary sets of molecules in one complex mixture can produce myriad different ordered and disordered supramolecular assemblies. Alternatively, spontaneous self-organization phenomena can promote the formation of specific product(s) out of a collection of multiple possibilities. Self-organization processes are common throughout much of nature and are especially common in biological systems. Recently, researchers have studied self-organized self-assembly in purely synthetic systems. This Account describes our investigations of self-organization in the coordination-driven self-assembly of platinum(II)-based metallosupramolecules. The modularity of the coordination-driven approach to self-assembly has allowed us to systematically study a wide variety of different factors that can control the extent of supramolecular self-organization. In particular, we have evaluated the effects of the symmetry and polarity of ambidentate donor subunits, differences in geometrical parameters (e.g. the size, angularity, and dimensionality) of Pt(II)-based acceptors and organic donors, the influence of temperature and solvent, and the effects of intermolecular steric interactions and hydrophobic interactions on self-organization. Our studies have shown that the extent of self-organization in the coordination-driven self-assembly of both 2D polygons and 3D polyhedra ranges from no organization (a statistical mixture of multiple products), to amplified organization (wherein a particular product or products are favored over others), and all the way to the absolute self-organization of discrete supramolecular assemblies. In many cases, inputs such as dipolar interactions, steric interactions, and differences in the geometric parameters of subunits—used either alone or as multiple factors simultaneously—can achieve absolute self-organization of discrete supramolecules. We have also observed instances where self-organization is not absolute and varies in its deviation from statistical results. Steric interactions are particularly useful control factors for driving such amplified self-organization because they can be subtly tuned through small structural variations. Having the ability to fully understand and control the self-organization of complex mixtures into specific synthetic supramolecules can provide a better understanding of analogous processes in biological systems. Furthermore, self-organization may allow for the facile synthesis of complex multifunctional, multicomponent systems from simply mixing a collection of much simpler, judiciously designed individual molecular components. PMID:19555073

  6. Self-assembly of hybrid structures on nano templates

    NASA Astrophysics Data System (ADS)

    Wang, Ruomiao

    This dissertation describes the investigation on the synthesis of hybrid structures on nano-templates. Fabrication of molecular nano-patterns of organic amphiphiles (e.g. fatty acids) by self-assembly has been discussed here, and their application as templates for two-dimensional in situ synthesis of metal soap molecular pattern has been demonstrated. The synthesis of nanoparticle---nanorod hybrid structure represents another effort to achieve hybrid materials. Therefore, methods to create complex inorganic---organic nano---hybrid are provided by this work. AFM disclosed the pattern structures of the self-assembled monolayers as designed nanoscaled patterns. It is observed two pattern periodicities reflecting the head-to-head and head-to-tail molecular assembly tendencies of the fatty acids and their dependence on the molecular structure and chain length, which exhibits a linear increase in the periodicity with an increasing molecular chain length. The investigation on molecular patterns of self-assembled monolayers of metal arachidates on graphite by AFM and FTIR is described. Metal arachidate self-assemblies show similar stripe pattern and periodicities as those of arachidic acid. The monolayer structure is mainly dictated by graphite, while the type of metal ions mainly affects the domain size, shape and regularity. The results of AFM and FTIR are correlated to the Irving-Williams Series, which predicts bond strength of the metal ions to ligands. The spin coated films from binary solutions of nanoparticles and fatty acids with different chain lengths (Even number of carbon, C18--C26), have been used to study the effect of nanoparticles on self-assemble pattern of fatty acids. C18--C22 acids formed uniform nanorods attached and induced by nanoparticles, while the self-assembled stripe patterns of C24 and C26 were unaffected by the presence of nanoparticles. The nanoparticles were aligned on C26 monolayer. The seeded nucleation mechanism has been studied by AFM, TEM, UV-Vis and in situ EDS and it is disclosed the confinement effect of nanoparticles and the competition between template effects from nanoparticle and from graphite. This strategy is proven to be universal, and nano-hybrids have been fabricated using different nanoparticle seeds, fatty acids, and solvents.

  7. Supramolecular Chemistry And Self-assembly Special Feature: Virus-assisted loading of polymer nanocontainer

    NASA Astrophysics Data System (ADS)

    Graff, Alexandra; Sauer, Marc; van Gelder, Patrick; Meier, Wolfgang

    2002-04-01

    We present a DNA-containing polymeric nanocontainer using the self-assembled superstructure of amphiphilic block copolymers in aqueous solutions. To demonstrate that DNA translocation is possible across a completely synthetic block copolymer membrane, we have used a phage transfection strategy as a DNA-transfer model system. For this purpose the bacterial channel forming protein LamB was reconstituted in ABA-triblock copolymer vesicles. The outer membrane protein LamB is a specific transporter for maltodextrins but also serves as a receptor for phage to trigger the ejection of phage DNA. We demonstrate that the functionality of the LamB protein is fully preserved despite the artificial surrounding. This leads to a type of polymeric vehicle for DNA that could be useful for gene therapy.

  8. Phonon line emission revealed by self-assembly of colloidal nanoplatelets.

    PubMed

    Tessier, Mickaël D; Biadala, Louis; Bouet, Cécile; Ithurria, Sandrine; Abecassis, Benjamin; Dubertret, Benoit

    2013-04-23

    We show that colloidal nanoplatelets can self-assemble to form a 1D superlattice. When self-assembled, an additional emission line appears in the photoluminescence spectrum at low temperatures. This emission line is a collective effect, greatly enhanced when the NPLs are self-assembled. It is attributed to the longitudinal optical (LO) phonon replica of the band-edge exciton, and its presence in self-assembled nanoplatelets is explained using a model based on an efficient photons reabsorption between neighboring nanoplatelets. The presence of phonon replica at low temperatures in ensemble measurements suggests the possibility to design a laser, based on self-assembled nanoplatelets. PMID:23458277

  9. Functionalized self-assembling peptide nanofiber hydrogels mimic stem cell niche to control human adipose stem cell behavior in vitro.

    PubMed

    Liu, Xi; Wang, Xiumei; Wang, Xiujuan; Ren, Hui; He, Jin; Qiao, Lin; Cui, Fu-Zhai

    2013-06-01

    A class of designer functionalized self-assembling peptide nanofiber scaffolds developed from self-assembling peptide RADA16-I (AcN-RADARADARADARADA-CONH2) has become increasingly attractive not only for studying spatial behaviors of cells, but also for developing approaches for a wide range of medical applications including regenerative medicine, rapid hemostasis and cell therapy. In this study, we report three functionalized self-assembling peptide hydrogels that serve as a three-dimensional (3-D) artificial microenvironment to control human adipose stem cell (hASC) behavior in vitro. Short peptide motifs SKPPGTSS (bone marrow homing motif), FHRRIKA (heparin-binding motif) and PRGDSGYRGDS (two-unit RGD cell adhesion motif) were used to extend the C-terminus of RADA16-I to obtain functionalized peptides. Atomic force microscopy confirmed the formation of self-assembling nanofibers in the mixture of RADA16-I peptide and functionalized peptides. The behaviors of hASCs cultured in 3-D peptide hydrogels, including migration, proliferation and growth factor-secretion ability, were studied. Our results showed that the functionalized peptide hydrogels were suitable 3-D scaffolds for hASC growth with higher cell proliferation, migration and the secretion of angiogenic growth factors compared with tissue culture plates and pure RADA16-I scaffolds. The present study suggests that these functionalized designer peptide hydrogels not only have promising applications for diverse tissue engineering and regenerative medicine applications as stem cell delivery vehicles, but also could be a biomimetic 3-D system to study nanobiomaterial-stem cell interactions and to direct stem cell behaviors. PMID:23380207

  10. Reinforcement of Shear Thinning Protein Hydrogels by Responsive Block Copolymer Self-Assembly

    PubMed Central

    Glassman, Matthew J.; Chan, Jacqueline

    2014-01-01

    Shear thinning hydrogels are promising materials that exhibit rapid self-healing following the cessation of shear, making them attractive for a variety of applications including injectable biomaterials. In this work, self-assembly is demonstrated as a strategy to introduce a reinforcing network within shear thinning artificially engineered protein gels, enabling a responsive transition from an injectable state at low temperatures with a low yield stress to a stiffened state at physiological temperatures with resistance to shear thinning, higher toughness, and reduced erosion rates and creep compliance. Protein-polymer triblock copolymers capable of the responsive self-assembly of two orthogonal networks have been synthesized by conjugating poly(N-isopropylacrylamide) to the N- and C- termini of a protein midblock decorated with coiled-coil self-associating domains. Midblock association forms a shear-thinning network, while endblock aggregation at elevated temperatures introduces a second, independent physical network into the protein hydrogel. These new, reversible crosslinks introduce extremely long relaxation times and lead to a five-fold increase in the elastic modulus, significantly larger than is expected from transient network theory. Thermoresponsive reinforcement reduces the high temperature creep compliance by over four orders of magnitude, decreases the erosion rate by at least a factor of five, and increases the yield stress by up to a factor of seven. The reinforced hydrogels also exhibit enhanced resistance to plastic deformation and failure in uniaxial compression. Combined with the demonstrated potential of shear thinning artificial protein hydrogels for various uses, including the minimally-invasive implantation of bioactive scaffolds, this reinforcement mechanism broadens the range of applications that can be addressed with shear-thinning physical gels. PMID:25568642

  11. Self assembled nanoparticle aggregates from line focused femtosecond laser ablation.

    PubMed

    Zuhlke, Craig A; Alexander, Dennis R; Bruce, John C; Ianno, Natale J; Kamler, Chad A; Yang, Weiqing

    2010-03-01

    In this paper we present the use of a line focused femtosecond laser beam that is rastered across a 2024 T3 aluminum surface to produce nanoparticles that self assemble into 5-60 micron diameter domed and in some cases sphere-shaped aggregate structures. Each time the laser is rastered over initial aggregates their diameter increases as new layers of nanoparticles self assemble on the surface. The aggregates are thus composed of layers of particles forming discrete layered shells inside of them. When micron size aggregates are removed, using an ultrasonic bath, rings are revealed that have been permanently formed in the sample surface. These rings appear underneath, and extend beyond the physical boundary of the aggregates. The surface is blackened by the formation of these structures and exhibits high light absorption. PMID:20389444

  12. Using Markov State Models to Study Self-Assembly

    NASA Astrophysics Data System (ADS)

    Perkett, Matthew; Hagan, Michael

    2014-03-01

    In recent years, a number of algorithms have been developed to study rare events, which has resulted in paradigm shift from running a few long trajectories to gathering statistics from many shorter trajectories. Running many simulations in parallel to build a Markov State Model (MSM) is one such technique, which has been applied to protein folding with great success. We present an adaptation to the MSM framework that enables its application to a wide range of systems undergoing self-assembly. The feasibility of this approach is demonstrated on two different coarse-grained models for virus self-assembly. We find good agreement between the MSM calculations and brute force long simulations, with up to several orders of magnitude reduction in simulation time.

  13. Self-assembly of amorphous calcium carbonate microlens arrays

    NASA Astrophysics Data System (ADS)

    Lee, Kyubock; Wagermaier, Wolfgang; Masic, Admir; Kommareddy, Krishna P.; Bennet, Mathieu; Manjubala, Inderchand; Lee, Seung-Woo; Park, Seung B.; Cölfen, Helmut; Fratzl, Peter

    2012-03-01

    Biological materials are often based on simple constituents and grown by the principle of self-assembly under ambient conditions. In particular, biomineralization approaches exploit efficient pathways of inorganic material synthesis. There is still a large gap between the complexity of natural systems and the practical utilization of bioinspired formation mechanisms. Here we describe a simple self-assembly route leading to a CaCO3 microlens array, somewhat reminiscent of the brittlestars' microlenses, with uniform size and focal length, by using a minimum number of components and equipment at ambient conditions. The formation mechanism of the amorphous CaCO3 microlens arrays was elucidated by confocal Raman spectroscopic imaging to be a two-step growth process mediated by the organic surfactant. CaCO3 microlens arrays are easy to fabricate, biocompatible and functional in amorphous or more stable crystalline forms. This shows that advanced optical materials can be generated by a simple mineral precipitation.

  14. Self-assembled liquid-crystal microlasers, microresonators, and microfibres

    NASA Astrophysics Data System (ADS)

    Muševi?, I.; Peng, Huang; Nikkhou, M.; Humar, M.

    2014-03-01

    When liquid crystals are dispersed in an immiscible fluid, microdroplets of liquid crystal are spontaneously formed in a fraction of a second. They have optically anisotropic internal structure, which is determined by the ordering of liquid crystal molecules at the interface. Spherical droplets of a nematic liquid crystal can function as whispering-gallery-mode microresonators with an unprecedented width of wavelength tunability by an electric field. WGM pulsed lasing in dyedoped nematic microdroplets is sensitive to strain, temperature and presence of molecules that change molecular orientation at the interface. Omnidirectional 3D lasing was demonstrated in droplets of chiral nematic liquid crystals that form 3D Bragg-onion resonators. We present recent progress in this field, including electric tuning of 3D lasing from chiral nematic droplets and self-assembly of ferroelectric smectic-C* microdroplets with the onion-Bragg structure. We show that anisotropic fibres could be self-assembled from smectic liquid crystals.

  15. Self-assembly of amorphous calcium carbonate microlens arrays

    PubMed Central

    Lee, Kyubock; Wagermaier, Wolfgang; Masic, Admir; Kommareddy, Krishna P.; Bennet, Mathieu; Manjubala, Inderchand; Lee, Seung-Woo; Park, Seung B.; Cölfen, Helmut; Fratzl, Peter

    2012-01-01

    Biological materials are often based on simple constituents and grown by the principle of self-assembly under ambient conditions. In particular, biomineralization approaches exploit efficient pathways of inorganic material synthesis. There is still a large gap between the complexity of natural systems and the practical utilization of bioinspired formation mechanisms. Here we describe a simple self-assembly route leading to a CaCO3 microlens array, somewhat reminiscent of the brittlestars' microlenses, with uniform size and focal length, by using a minimum number of components and equipment at ambient conditions. The formation mechanism of the amorphous CaCO3 microlens arrays was elucidated by confocal Raman spectroscopic imaging to be a two-step growth process mediated by the organic surfactant. CaCO3 microlens arrays are easy to fabricate, biocompatible and functional in amorphous or more stable crystalline forms. This shows that advanced optical materials can be generated by a simple mineral precipitation. PMID:22395616

  16. Calixarene-encapsulated nanoparticles: self-assembly into functional nanomaterials.

    PubMed

    Wei, Alexander

    2006-04-21

    Calixarenes are excellent surfactants for enhancing the dispersion and self-assembly of metal nanoparticles into well-defined structures, particularly those with unit length scales in the 10-100 nm size range. Particles within these ensembles are strongly coupled, giving rise to unique collective optical or magnetic properties. The self-assembled nanostructures described in this feature article include 2D arrays of colloidal Au nanoparticles with size-dependent plasmonic responses, and sub-100 nm Co nanoparticle rings with chiral magnetic states. These nanoparticle assemblies may be further developed for applications in chemical sensing based on surface-enhanced Raman scattering (SERS) and as binary elements for nonvolatile memory, respectively. PMID:16582988

  17. Electrostatically Directed Self-Assembly of Ultrathin Supramolecular Polymer Microcapsules

    PubMed Central

    Parker, Richard M; Zhang, Jing; Zheng, Yu; Coulston, Roger J; Smith, Clive A; Salmon, Andrew R; Yu, Ziyi; Scherman, Oren A; Abell, Chris

    2015-01-01

    Supramolecular self-assembly offers routes to challenging architectures on the molecular and macroscopic scale. Coupled with microfluidics it has been used to make microcapsules—where a 2D sheet is shaped in 3D, encapsulating the volume within. In this paper, a versatile methodology to direct the accumulation of capsule-forming components to the droplet interface using electrostatic interactions is described. In this approach, charged copolymers are selectively partitioned to the microdroplet interface by a complementary charged surfactant for subsequent supramolecular cross-linking via cucurbit[8]uril. This dynamic assembly process is employed to selectively form both hollow, ultrathin microcapsules and solid microparticles from a single solution. The ability to dictate the distribution of a mixture of charged copolymers within the microdroplet, as demonstrated by the single-step fabrication of distinct core–shell microcapsules, gives access to a new generation of innovative self-assembled constructs.

  18. Self-Assembly and Waterlike Anomalies in Janus Nanoparticles

    E-print Network

    José Rafael Bordin; Leandro B. Krott; Marcia C. Barbosa

    2015-04-28

    We explore the pressure versus temperature phase diagram of dimeric Janus nanoparticles using Molecular Dynamics simulations. The nanoparticle was modeled as a dumbbells particle, and have one monomer that interacts by a standard Lennard Jones potential and another monomer that is modeled using a two-length scale shoulder potential. Monomeric and dimeric systems modeled by this shoulder potential show waterlike anomalies, and we investigate if a Janus nanoparticle composed by one anomalous monomer will exhibit anomalous behavior and self-assembly structures. The influence of the non-anomalous monomer in the dimeric system properties was explored. We show that the diffusion anomaly is maintained, while the density anomaly can disappear depending on the non-anomalous monomer characteristics. As well, the self-assembled structures are affected. Our results are discussed in the basis of the distinct monomer-monomer interactions and on the two-length scale fluid characteristics.

  19. Biomolecular decision-making process for self assembly.

    SciTech Connect

    Osbourn, Gordon Cecil

    2005-01-01

    The brain is often identified with decision-making processes in the biological world. In fact, single cells, single macromolecules (proteins) and populations of molecules also make simple decisions. These decision processes are essential to survival and to the biological self-assembly and self-repair processes that we seek to emulate. How do these tiny systems make effective decisions? How do they make decisions in concert with a cooperative network of other molecules or cells? How can we emulate the decision-making behaviors of small-scale biological systems to program and self-assemble microsystems? This LDRD supported research to answer these questions. Our work included modeling and simulation of protein populations to help us understand, mimic, and categorize molecular decision-making mechanisms that nonequilibrium systems can exhibit. This work is an early step towards mimicking such nanoscale and microscale biomolecular decision-making processes in inorganic systems.

  20. Control of gene expression by modulated self-assembly

    E-print Network

    Jose M. G. Vilar; Leonor Saiz

    2011-05-25

    Numerous transcription factors self-assemble into different order oligomeric species in a way that is actively regulated by the cell. Until now, no general functional role has been identified for this widespread process. Here we capture the effects of modulated self-assembly in gene expression with a novel quantitative framework. We show that this mechanism provides precision and flexibility, two seemingly antagonistic properties, to the sensing of diverse cellular signals by systems that share common elements present in transcription factors like p53, NF-kappaB, STATs, Oct, and RXR. Applied to the nuclear hormone receptor RXR, this framework accurately reproduces a broad range of classical, previously unexplained, sets of gene expression data and corroborates the existence of a precise functional regime with flexible properties that can be controlled both at a genome-wide scale and at the individual promoter level.

  1. Self-Assembly of Graphene on Carbon Nanotube Surfaces

    PubMed Central

    Li, Kaiyuan; Eres, Gyula; Howe, Jane; Chuang, Yen-Jun; Li, Xufan; Gu, Zhanjun; Zhang, Litong; Xie, Sishen; Pan, Zhengwei

    2013-01-01

    The rolling up of a graphene sheet into a tube is a standard visualization tool for illustrating carbon nanotube (CNT) formation. However, the actual processes of rolling up graphene sheets into CNTs in laboratory syntheses have never been demonstrated. Here we report conformal growth of graphene by carbon self-assembly on single-wall and multi-wall CNTs using chemical vapor deposition (CVD) of methane without the presence of metal catalysts. The new graphene layers roll up into seamless coaxial cylinders encapsulating the existing CNTs, but their adhesion to the primary CNTs is weak due to the existence of lattice misorientation. Our study shows that graphene nucleation and growth by self-assembly of carbon on the inactive carbon basal plane of CNTs occurs by a new mechanism that is markedly different from epitaxial growth on metal surfaces, opening up the possibility of graphene growth on many other non-metal substrates by simple methane CVD. PMID:23912638

  2. Multilayered self-assembled optical fiber sensors for biomedical applications

    NASA Astrophysics Data System (ADS)

    Mecham, Jeffrey B.; Kang, Y.; Davis, B.; Arregui, Francisco J.; Matias, Ignacio R.; Claus, Richard O.

    2003-07-01

    We report recent developments in the design and fabrication of molecularly self-assembled thin film materials that may be incorporated with optical fiber waveguides to form humidity and other gas sensors of use in biomedical diagnositc systems. Optical fiber distal end sensors based on this concept may be fabricated by molecularly self-assembling selected polymers and functionalized inorganic nanoclustesr into multilayered optical thin films on the cleaved and polished flat ends of singlemode optical fibers. Prior work reported at this meeting has studied the synthesis process and sensor dynamics, including sensor 10-90% risetime on the order of microseconds. This paper briefly reviews that work but then reports new developments in the synthesis of the sensor films.

  3. Energy transfer in an LH4-like light harvesting complex from the aerobic purple photosynthetic bacterium Roseobacter denitrificans

    SciTech Connect

    Niedzwiedzki, Dariusz; Fuciman, Marcel; Frank, Harry A; Blankenship, R. E.

    2011-01-01

    A peripheral light-harvesting complex from the aerobic purple bacterium Roseobacter (R.) denitrificans was purified and its photophysical properties characterized. The complex contains two types of pigments, bacteriochlorophyll (BChl) a and the carotenoid (Car) spheroidenone and possesses unique spectroscopic properties. It appears to lack the B850 bacteriochlorophyll a Q{sub y} band that is typical for similar light-harvesting complex 2 antennas. Circular dichroism and low temperature steady-state absorption spectroscopy revealed that the B850 band is present but is shifted significantly to shorter wavelengths and overlaps with the B800 band at room temperature. Such a spectral signature classifies this protein as a member of the light-harvesting complex 4 class of peripheral light-harvesting complexes, along with the previously known light-harvesting complex 4 from Rhodopseudomonas palustris. The influence of the spectral change on the light-harvesting ability was studied using steady-state absorption, fluorescence, circular dichroism, femtosecond and microsecond time-resolved absorption and time-resolved fluorescence spectroscopies. The results were compared to the properties of the similar (in pigment composition) light-harvesting complex 2 from aerobically grown Rhodobacter sphaeroides and are understood within the context of shared similarities and differences and the putative influence of the pigments on the protein structure and its properties.

  4. Self-Assembly of [ n ]Rotaxanes Bearing Dendritic Stoppers ?

    Microsoft Academic Search

    David B. Amabilino; Peter R. Ashton; Vincenzo Balzani; Christopher L. Brown; Alberto Credi; Jean M. J. Frechet; Jeffrey W. Leon; Françisco M. Raymo; Neil Spencer; J. Fraser Stoddart; Margherita Venturi

    1996-01-01

    We have developed a synthetic approach to the self-assembly of (2)-, (3)-, and (4)rotaxanes, incorporating bis-p-phenylene-34-crown-10 as the ring component(s) surrounding bipyridinium-based dumbbell-shaped components bearing dendritic stoppers at both ends. As a result of the hydrophobic dendritic framework, these ( n)rotaxanes are soluble in a wide range of organic solvents, despite the polycationic natures of their bipyridinium-based backbones. In all

  5. Lighting up cells with lanthanide self-assembled helicates

    PubMed Central

    Bünzli, Jean-Claude G.

    2013-01-01

    Lanthanide bioprobes and bioconjugates are ideal luminescent stains in view of their low propensity to photobleaching, sharp emission lines and long excited state lifetimes permitting time-resolved detection for enhanced sensitivity. We show here how the interplay between physical, chemical and biochemical properties allied to microfluidics engineering leads to self-assembled dinuclear lanthanide luminescent probes illuminating live cells and selectively detecting biomarkers expressed by cancerous human breast cells. PMID:24511387

  6. Blocking behavior of self-assembled monolayers on gold electrodes

    Microsoft Academic Search

    Hong Shen; James E. Mark; Carl J. Seliskar; Harry B. Mark Jr.; William R. Heineman

    1997-01-01

    Self-assembled monolayers (SAMs) with metal electrodes, especially thiols on gold, are the subject of this investigation\\u000a because of the unique properties of SAM-modified surfaces. Normal alkanethiols are used to modify the surface of a conventional\\u000a gold electrode to block certain ions such as Pb(II) and Cu(II) from the surface of the electrode. Normal alkanethiols are\\u000a also used to study the

  7. Self-assembled monolayer gold electrode for surfactant analysis

    Microsoft Academic Search

    Marc Gerlache; Zühre Senturk; Guy Quarin; Jean-Michel Kauffmann

    1997-01-01

    A gold electrode coated with a self-assembled monolayer of octane-thiol (SAM\\/Au) has been used as an amperometric detector\\u000a for the determination of surfactants. This detector operated in the presence of a high percentage of organic solvent and was\\u000a adapted to an HPLC System. At the SAM\\/Au, the electrochemical response of an electroactive tracer (potassium ferricyanide)\\u000a was completely inhibited, but, in

  8. Intrinsic Electronic Conduction Mechanisms in Self-Assembled Monolayers

    Microsoft Academic Search

    Wenyong Wang; Takhee Lee; Mark A. Reed

    2005-01-01

    A review on the mechanisms and characterization methods of molecular electronic transport is presented. Using self-assembled\\u000a monolayers (SAMs) of alkanethiols in a nanometer scale device structure, tunneling is unambiguously demonstrated as the main\\u000a conduction mechanism for large bandgap SAMs, exhibiting well-known temperature and length dependencies. Inelastic electron\\u000a tunneling spectroscopy exhibits clear vibrational modes of the molecules in the device, presenting

  9. Preparation of self-assembled silk sericin nanoparticles

    Microsoft Academic Search

    Kwang Yong Cho; Jae Yu Moon; Yong Woo Lee; Kwang Gill Lee; Joo Hong Yeo; Hae Yong Kweon; Ki Ho Kim; Chong Su Cho

    2003-01-01

    Silk sericin (SS) possessing moisture-retaining property was reacted with activated poly(ethylene glycol) (PEG) to obtain self-assembled SS nanoparticles. The aliphatic and aromatic hydroxyl groups of serine and tyrosine residues as the reaction sites in SS were clarified by amino acid analysis and 1H NMR spectroscopy, respectively. From IR and circular dichroism (CD) measurements, introduction of PEG into SS induced the

  10. Fibrin self-assembly inhibitor turnover in rats

    SciTech Connect

    Chiryat'ev, E.A.; Umutbaeva, M.K.; Byshevskii, A.Sh.

    1987-10-01

    The aim of this investigation was to study changes in the concentration of the fibrin self-assembly inhibitor and the mechanism of the changes in diametrically opposite states of blood coagulation, namely, the acceleration and restriction of thrombin formation. Fibrin monomer was obtained from bovine plasma. The inhibitor, a polypeptide, was labelled with potassium iodide activated with iodine 131. The radioactive inhibitor was injected and its concentration determined by chromatography and tracer analysis.

  11. Novel Piezoelectric DDVP Sensor Based on Self?Assembly Method

    Microsoft Academic Search

    Hongjuan Zeng; Yadong Jiang; Guangzhong Xie; Junsheng Yu

    2007-01-01

    A novel piezoelectric sensor was fabricated by depositing the films of polyvinyl pyrrolindone (PVP) and PVP with butyl cholinesterase (BuChE) (BuChE?PVP), respectively, on the surface of quartz crystal microbalance (QCM) using self?assembly method. The sensitive films were characterized with online examination and XPS technique. The obtained sensors were applied to measure o,o?dimethyl?o?2,2?dichlorovinyl phosphate (DDVP) pesticide concentration. It shows that BuChE?PVP

  12. Self-assembled containers based on extended tetrathiafulvalene.

    PubMed

    Bivaud, Sébastien; Goeb, Sébastien; Croué, Vincent; Dron, Paul I; Allain, Magali; Sallé, Marc

    2013-07-10

    Two original self-assembled containers constituted each by six electroactive subunits are described. They are synthesized from a concave tetratopic ?-extended tetrathiafulvalene ligand bearing four pyridyl units and cis-M(dppf)(OTf)2 (M = Pd or Pt; dppf = 1,1'-bis(diphenylphosphino)ferrocene; OTf = trifluoromethane-sulfonate) complexes. Both fully characterized assemblies present an oblate spheroidal cavity that can incorporate one perylene molecule. PMID:23795694

  13. Self-assembled polymer MEMS sensors and actuators

    Microsoft Academic Search

    Andrea J. Hill; Richard O. Claus; Jennifer H. Lalli; Michelle Homer

    2006-01-01

    This paper describes the use of Metal RubberTM, which is an electrically-conductive, low modulus, highly-flexible, and optically transparent free-standing or conformal coating nanocomposite material that is fabricated via Electrostatic Self-Assembly (ESA), as a polymer MEMS sensor for actuator materials. ESA is an environmentally-friendly layer-by-layer fabrication technique in which Metal RubberTM can be tailor designed at the molecular level to function

  14. A ‘mixed’ self-assembled monolayer for an impedimetric immunosensor

    Microsoft Academic Search

    Peter Heiduschka

    1996-01-01

    A synthetic peptide with the amino acid sequence 135–154 of the capsid protein VP1 of the foot-and-mouth-disease virus was modified with ?-hydroxyundecanethiol and applied together with non-derivatised ?-hydroxyundecanethiol for consecutive adsorption onto gold electrodes according to self-assembling procedures. The binding of a specific antibody to prepared recognition layers could be monitored by measurement of impedance or capacitance. In order to

  15. Propagating Waves of Self-assembly in Organosilane Monolayers

    SciTech Connect

    Douglas,J.; Efimenko, K.; Fischer, D.; Phelan, F.; Genzer, J.

    2007-01-01

    Wavefronts associated with reaction-diffusion and self-assembly processes are ubiquitous in the natural world. For example, propagating fronts arise in crystallization and diverse other thermodynamic ordering processes, in polymerization fronts involved in cell movement and division, as well as in the competitive social interactions and population dynamics of animals at much larger scales. Although it is often claimed that self-sustaining or autocatalytic front propagation is well described by mean-field 'reaction-diffusion' or 'phase field' ordering models, it has recently become appreciated from simulations and theoretical arguments that fluctuation effects in lower spatial dimensions can lead to appreciable deviations from the classical mean-field theory (MFT) of this type of front propagation. The present work explores these fluctuation effects in a real physical system. In particular, we consider a high-resolution near-edge x-ray absorption fine structure spectroscopy (NEXAFS) study of the spontaneous frontal self-assembly of organosilane (OS) molecules into self-assembled monolayer (SAM) surface-energy gradients on oxidized silicon wafers. We find that these layers organize from the wafer edge as propagating wavefronts having well defined velocities. In accordance with two-dimensional simulations of this type of front propagation that take fluctuation effects into account, we find that the interfacial widths w(t) of these SAM self-assembly fronts exhibit a power-law broadening in time, w(t) {approx} t{sup {beta}}, rather than the constant width predicted by MFT. Moreover, the observed exponent values accord rather well with previous simulation and theoretical estimates. These observations have significant implications for diverse types of ordering fronts that occur under confinement conditions in biological or materials-processing contexts.

  16. Propagating Waves of Self-assembly in Organosilane Monolayers

    Microsoft Academic Search

    J. F. Douglas; K. Efimenko; D. A. Fischer; F. R. Phelan; J. Genzer

    2007-01-01

    Wavefronts associated with reaction-diffusion and self-assembly processes are ubiquitous in the natural world. For example, propagating fronts arise in crystallization and diverse other thermodynamic ordering processes, in polymerization fronts involved in cell movement and division, as well as in the competitive social interactions and population dynamics of animals at much larger scales. Although it is often claimed that self-sustaining or

  17. Self-assembly: mastering photonic processes at nanoscale

    Microsoft Academic Search

    C. Fiorini; F. Charra

    2010-01-01

    Supramolecular ordering happens as an important parameter for the control of light emission processes. In this review paper,\\u000a we discuss several examples of application of self-assembly to the realization of nano-structures designed in view of mastering\\u000a specific photonic processes. This comprises the formation of highly localized plasmon modes in self-organized 2D assemblies\\u000a of metal nanoparticles, the immobilization of dyes inside

  18. 3-D microbattery electrolyte by self-assembly of oligomers

    Microsoft Academic Search

    Semra Tan; Sylwia Walus; Torbjörn Gustafsson; Daniel Brandell

    2011-01-01

    This paper reports the preparation and characterization of novel thin film electrolytes by UV cross-linking of poly(propylene glycol) diacrylate in the presence of polyetheramine (glyceryl poly(oxypropylene)triamine) and LiTFSI. The oligomeric surfactant polyetheramine facilitates self-assembly of the electrolyte, enabling it to be applied conformally onto a complex substrate which is necessary for 3D-microbatteries, while the acrylate network supplies mechanical stability. Conformal

  19. Dispersion of nanoparticulate suspensions using self-assembled surfactant aggregates

    NASA Astrophysics Data System (ADS)

    Singh, Pankaj Kumar

    The dispersion of particles is critical for several industrial applications such as paints, inks, coatings, and cosmetics. Several emerging applications such as abrasives for precision polishing, and drug delivery systems are increasingly relying on nanoparticulates to achieve the desired performance. In the case of nanoparticles, the dispersion becomes more challenging because of the lack of fundamental understanding of dispersant adsorption and interparticle force prediction. Additionally, many of these processes use severe processing environments such as high normal forces (>100 mN/m), high shear forces (>10,000 s -1), and high ionic strengths (>0.1 M). Under such processing conditions, traditionally used dispersants based on electrostatics, and steric force repulsion mechanism may not be adequate. Hence, the development of optimally performing dispersants requires a fundamental understanding of the dispersion mechanism at the atomic/molecular scale. This study explores the use of self-assembled surfactant aggregates at the solid-liquid interface for dispersing nanoparticles in severe processing environments. Surfactant molecules can provide a feasible alternative to polymeric or inorganic dispersants for stabilizing ultrafine particles. The barrier to aggregation in the presence of surfactant molecules was measured using atomic force microscopy. The barrier heights correlated to suspension stability. To understand the mechanism for nanoparticulate suspension stability in the presence of surfactant films, the interface was characterized using zeta potential, contact angle, adsorption, and FT-IR (adsorbed surfactant film structure measurements). The effect of solution conditions such as pH and ionic strength on the suspension stability, and the self-assembled surfactant films was also investigated. It was determined that a transition from a random to an ordered orientation of the surfactant molecules at the interface was responsible for stability of nanoparticulates. Additionally, the role of the surface in surfactant self-assembly was investigated. Mechanical and thermodynamic properties of the self-assembled layer at the solid-liquid interface were calculated based on experimental results, and compared to the corresponding properties in the bulk solution.

  20. Sampling the Self-Assembly Pathways of KFFE Hexamers

    Microsoft Academic Search

    Guanghong Wei; Normand Mousseau; Philippe Derreumauxy

    2004-01-01

    The formation of amyloid fibrils is often encountered in Alzheimer’s disease, type II diabetes, and transmissible spongiform encephalopathies. In the last few years, however, mounting evidence has suggested that the soluble oligomers of amyloid-forming peptides are also cytotoxic agents. Understanding the early pathway steps of amyloid self-assembly at atomic detail might therefore be crucial for the development of specific inhibitors

  1. Perovskite Microdisk Microlasers Self-Assembled from Solution.

    PubMed

    Liao, Qing; Hu, Ke; Zhang, Haihua; Wang, Xuedong; Yao, Jiannian; Fu, Hongbing

    2015-06-01

    Single-crystalline square microdisks of CH3 NH3 PbBr3 are prepared by using a one-step solution self-assembly method. Single-mode lasing at 557 nm is achieved based on a built-in whispering gallery mode microresonator at room temperature. By partial replacement of Br with Cl, lasing wavelengths are continuously tuned from 525 to 557 nm. PMID:25903387

  2. Self-assembly of semiconductor nanocrystals into ordered superstructures

    Microsoft Academic Search

    Elena V. Shevchenko; Dmitri V. Talapin

    Organization of uniform objects into periodic structures can be found in many natural systems, such as atomic and molecular\\u000a solids, opals, sponges and bacterial colonies — self-assembly is the fundamental phenomenon that generates structural organization\\u000a on all scales [1]. In this chapter we discuss the structures spontaneously formed by nanoparticles which attracted significant interest from\\u000a different branches of science and

  3. Propagating waves of self-assembly in organosilane monolayers

    PubMed Central

    Douglas, Jack F.; Efimenko, Kirill; Fischer, Daniel A.; Phelan, Fredrick R.; Genzer, Jan

    2007-01-01

    Wavefronts associated with reaction–diffusion and self-assembly processes are ubiquitous in the natural world. For example, propagating fronts arise in crystallization and diverse other thermodynamic ordering processes, in polymerization fronts involved in cell movement and division, as well as in the competitive social interactions and population dynamics of animals at much larger scales. Although it is often claimed that self-sustaining or autocatalytic front propagation is well described by mean-field “reaction–diffusion” or “phase field” ordering models, it has recently become appreciated from simulations and theoretical arguments that fluctuation effects in lower spatial dimensions can lead to appreciable deviations from the classical mean-field theory (MFT) of this type of front propagation. The present work explores these fluctuation effects in a real physical system. In particular, we consider a high-resolution near-edge x-ray absorption fine structure spectroscopy (NEXAFS) study of the spontaneous frontal self-assembly of organosilane (OS) molecules into self-assembled monolayer (SAM) surface-energy gradients on oxidized silicon wafers. We find that these layers organize from the wafer edge as propagating wavefronts having well defined velocities. In accordance with two-dimensional simulations of this type of front propagation that take fluctuation effects into account, we find that the interfacial widths w(t) of these SAM self-assembly fronts exhibit a power-law broadening in time, w(t) ? t?, rather than the constant width predicted by MFT. Moreover, the observed exponent values accord rather well with previous simulation and theoretical estimates. These observations have significant implications for diverse types of ordering fronts that occur under confinement conditions in biological or materials-processing contexts. PMID:17566108

  4. Versatile bisethynyl[60]fulleropyrrolidine scaffolds for mimicking artificial light-harvesting photoreaction centers.

    PubMed

    Kremer, Adrian; Bietlot, Emerance; Zanelli, Alberto; Malicka, Joanna M; Armaroli, Nicola; Bonifazi, Davide

    2015-01-12

    Fullerene-based tetrads, triads, and dyads are presented in which [60]fulleropyrrolidine synthons are linked to an oligo(p-phenyleneethynylene) antenna at the nitrogen atom and to electron-donor phenothiazine (PTZ) and/or ferrocene (Fc) moieties at the ? carbon of the pyrrolidine cycle through an acetylene spacer. Cyclic voltammetry and UV/ Vis absorption spectra evidence negligible ground-state electronic interactions among the subunits. By contrast, strong excited-state interactions are detected upon selective light irradiation of the antenna (UV) or of the fullerene scaffold (Vis). When only PTZ is present as electron donor, photoinduced electron transfer to the fullerene unit is unambiguously detected in benzonitrile, but this is not the case when Fc is part of the multicomponent system. These results suggest that Fc is a formidable energy transfer quencher and caution should be used in choosing it as electron donor to promote efficient charge separation in multicomponent arrays. PMID:25418041

  5. Model-driven optimization of multicomponent self-assembly processes.

    PubMed

    Korevaar, Peter A; Grenier, Christophe; Markvoort, Albert J; Schenning, Albertus P H J; de Greef, Tom F A; Meijer, E W

    2013-10-22

    Here, we report an engineering approach toward multicomponent self-assembly processes by developing a methodology to circumvent spurious, metastable assemblies. The formation of metastable aggregates often hampers self-assembly of molecular building blocks into the desired nanostructures. Strategies are explored to master the pathway complexity and avoid off-pathway aggregates by optimizing the rate of assembly along the correct pathway. We study as a model system the coassembly of two monomers, the R- and S-chiral enantiomers of a ?-conjugated oligo(p-phenylene vinylene) derivative. Coassembly kinetics are analyzed by developing a kinetic model, which reveals the initial assembly of metastable structures buffering free monomers and thereby slows the formation of thermodynamically stable assemblies. These metastable assemblies exert greater influence on the thermodynamically favored self-assembly pathway if the ratio between both monomers approaches 1:1, in agreement with experimental results. Moreover, competition by metastable assemblies is highly temperature dependent and hampers the assembly of equilibrium nanostructures most effectively at intermediate temperatures. We demonstrate that the rate of the assembly process may be optimized by tuning the cooling rate. Finally, it is shown by simulation that increasing the driving force for assembly stepwise by changing the solvent composition may circumvent metastable pathways and thereby force the assembly process directly into the correct pathway. PMID:24101463

  6. Molecular Motions in Functional Self-Assembled Nanostructures

    PubMed Central

    Dhotel, Alexandre; Chen, Ziguang; Delbreilh, Laurent; Youssef, Boulos; Saiter, Jean-Marc; Tan, Li

    2013-01-01

    The construction of “smart” materials able to perform specific functions at the molecular scale through the application of various stimuli is highly attractive but still challenging. The most recent applications indicate that the outstanding flexibility of self-assembled architectures can be employed as a powerful tool for the development of innovative molecular devices, functional surfaces and smart nanomaterials. Structural flexibility of these materials is known to be conferred by weak intermolecular forces involved in self-assembly strategies. However, some fundamental mechanisms responsible for conformational lability remain unexplored. Furthermore, the role played by stronger bonds, such as coordination, ionic and covalent bonding, is sometimes neglected while they can be employed readily to produce mechanically robust but also chemically reversible structures. In this review, recent applications of structural flexibility and molecular motions in self-assembled nanostructures are discussed. Special focus is given to advanced materials exhibiting significant performance changes after an external stimulus is applied, such as light exposure, pH variation, heat treatment or electromagnetic field. The crucial role played by strong intra- and weak intermolecular interactions on structural lability and responsiveness is highlighted. PMID:23348927

  7. Patterning self-assembled FePt nanoparticles

    NASA Astrophysics Data System (ADS)

    Chen, Min; Nikles, David E.; Yin, Huaqin; Wang, Shoutao; Harrell, J. W.; Majetich, Sara A.

    2003-10-01

    We describe a potential way to extend the ordered domain of self-assembled FePt nanoparticles. The FePt particles, with an average diameter of 3 nm, were prepared by simultaneous thermal decomposition of Fe(CO) 5 and chemical reduction of Pt(acac) 2 and then were dispersed in a mixture of hexane and octane. When self-assembling on a plain silicon wafer, FePt nanoparticles formed ordered hexagonal arrays in a range of tens to a few hundred nanometers. A silicon wafer with patterned holes of a photoresist film, made using UV-lithographing technique, was used as a template to direct the stacking direction of the FePt nanoparticles. The FePt dispersion was dropped on the patterned holes of the photoresist film. After being heat-treated at 100°C for 30 min under vacuum condition, the photoresist was stripped out by dipping the sample in acetone. The patterned disks, with an average diameter of 2.0 ?m and a height of 250 nm, of self-assembled FePt nanoparticles were examined using SEM and Auger mapping. Their magnetic properties were measured using AGM. The Auger electrons of neither Fe LMM nor Pt MNN could be detected from the sample, which indicated the adsorption of oleic acid and oleylamine on the surface of FePt nanoparticles. The coercivity of patterned FePt significantly increased with the annealing temperature above 600°C.

  8. Size-controlled self-assembly of superparamagnetic polymersomes.

    PubMed

    Hickey, Robert J; Koski, Jason; Meng, Xin; Riggleman, Robert A; Zhang, Peijun; Park, So-Jung

    2014-01-28

    We report the size-controlled self-assembly of polymersomes through the cooperative self-assembly of nanoparticles and amphiphilic polymers. Polymersomes densely packed with magnetic nanoparticles in the polymersome membrane (magneto-polymersome) were fabricated with a series of different sized iron oxide nanoparticles. The distribution of nanoparticles in a polymersome membrane was size-dependent; while small nanoparticles were dispersed in a polymer bilayer, large particles formed a well-ordered superstructure at the interface between the inner and outer layer of a bilayer membrane. The yield of magneto-polymersomes increased with increasing the diameter of incorporated nanoparticles. Moreover, the size of the polymersomes was effectively controlled by varying the size of incorporated nanoparticles. This size-dependent self-assembly was attributed to the polymer chain entropy effect and the size-dependent localization of nanoparticles in polymersome bilayers. The transverse relaxation rates (r2) of magneto-polymersomes increased with increasing the nanoparticle diameter and decreasing the size of polymersomes, reaching 555 ± 24 s(-1) mM(-1) for 241 ± 16 nm polymersomes, which is the highest value reported to date for superparamagnetic iron oxide nanoparticles. PMID:24369711

  9. Hierarchically Organized Structures Engineered from Controlled Evaporative Self-Assembly

    NASA Astrophysics Data System (ADS)

    Lin, Zhiqun; Byun, Myunghwan; Han, Wei; Bowden, Ned

    2011-03-01

    By constraining an asymmetric comb block copolymer (CBCP) toluene solution to evaporate in a wedge-on-Si geometry composed of a wedge lens situated on a Si substrate, gradient concentric stripe-like surface patterns of CBCP at the microscopic scale were yielded as a direct consequence of controlled evaporative self-assembly of CBCP. The formation of either straight stripes or jagged stripes was dictated by the height of the wedge. Upon subsequent solvent vapor annealing, hierarchically organized structures of CBCP were produced, resulting from the interplay of solvent vapor-assisted, unfavorable interfacial interaction-driven destabilization of CBCP from the Si substrate at the microscopic scale and the solvent vapor-promoted reconstruction of CBCP nanodomains within the stripes at the nanometer scale. This facile approach of combining controlled evaporative self-assembly with subsequent solvent vapor annealing offers a new platform to rationally design and engineer self-assembling building blocks into functional materials and devices in a simple, cost-effective manner.

  10. Self-assembly of model DNA-binding peptide amphiphiles.

    PubMed

    Bitton, Ronit; Schmidt, Judith; Biesalski, Markus; Tu, Raymond; Tirrell, Matthew; Bianco-Peled, Havazelet

    2005-12-01

    Peptide amphiphiles combine the specific functionality of proteins with the engineering convenience of synthetic amphiphiles. These molecules covalently link a peptide headgroup, typically from an active fragment of a larger protein, to a hydrophobic alkyl tail. Our research is aimed at forming and characterizing covalently stabilized, self-assembled, peptide-amphiphile aggregates that can be used as a platform for the examination and modular design and construction of systems with engineering biological activity. We have studied the self-assembly properties of a model DNA-binding amphiphile, having a GCN4 peptide as the headgroup and containing a polymerizable methacrylic group in the tail region, using a combination of small-angle X-ray scattering, small-angle neutron scattering, and cryo- transmission electron microscopy. Our results reveal a variety of morphologies in this system. The peptide amphiphiles assembled in aqueous solution to helical ribbons and tubules. These structures transformed into lamella upon DNA binding. In contrast with common surfactants, the specific interaction between the headgroups seems to play an important role in determining the microstructure. The geometry of the self-assembled aggregate can be controlled by means of adding a cosurfactant. For example, the addition of SDS induced the formation of spherical micelles. PMID:16316129

  11. Engineering hierarchical nanostructures by elastocapillary self-assembly.

    PubMed

    De Volder, Michaël; Hart, A John

    2013-02-25

    Surfaces coated with nanoscale filaments such as silicon nanowires and carbon nanotubes are potentially compelling for high-performance battery and capacitor electrodes, photovoltaics, electrical interconnects, substrates for engineered cell growth, dry adhesives, and other smart materials. However, many of these applications require a wet environment or involve wet processing during their synthesis. The capillary forces introduced by these wet environments can lead to undesirable aggregation of nanoscale filaments, but control of capillary forces can enable manipulation of the filaments into discrete aggregates and novel hierarchical structures. Recent studies suggest that the elastocapillary self-assembly of nanofilaments can be a versatile and scalable means to build complex and robust surface architectures. To enable a wider understanding and use of elastocapillary self-assembly as a fabrication technology, we give an overview of the underlying fundamentals and classify typical implementations and surface designs for nanowires, nanotubes, and nanopillars made from a wide variety of materials. Finally, we discuss exemplary applications and future opportunities to realize new engineered surfaces by the elastocapillary self-assembly of nanofilaments. PMID:23339106

  12. Self-assembly of strongly dipolar molecules on metal surfaces

    NASA Astrophysics Data System (ADS)

    Kunkel, Donna A.; Hooper, James; Simpson, Scott; Miller, Daniel P.; Routaboul, Lucie; Braunstein, Pierre; Doudin, Bernard; Beniwal, Sumit; Dowben, Peter; Skomski, Ralph; Zurek, Eva; Enders, Axel

    2015-03-01

    The role of dipole-dipole interactions in the self-assembly of dipolar organic molecules on surfaces is investigated. As a model system, strongly dipolar model molecules, p-benzoquinonemonoimine zwitterions (ZI) of type C6H2(⋯ NHR)2(⋯ O)2 on crystalline coinage metal surfaces were investigated with scanning tunneling microscopy and first principles calculations. Depending on the substrate, the molecules assemble into small clusters, nano gratings, and stripes, as well as in two-dimensional islands. The alignment of the molecular dipoles in those assemblies only rarely assumes the lowest electrostatic energy configuration. Based on calculations of the electrostatic energy for various experimentally observed molecular arrangements and under consideration of computed dipole moments of adsorbed molecules, the electrostatic energy minimization is ruled out as the driving force in the self-assembly. The structures observed are mainly the result of a competition between chemical interactions and substrate effects. The substrate's role in the self-assembly is to (i) reduce and realign the molecular dipole through charge donation and back donation involving both the molecular HOMO and LUMO, (ii) dictate the epitaxial orientation of the adsorbates, specifically so on Cu(111), and (iii) inhibit attractive forces between neighboring chains in the system ZI/Cu(111), which results in regularly spaced molecular gratings.

  13. Molecular motions in functional self-assembled nanostructures.

    PubMed

    Dhotel, Alexandre; Chen, Ziguang; Delbreilh, Laurent; Youssef, Boulos; Saiter, Jean-Marc; Tan, Li

    2013-01-01

    The construction of "smart" materials able to perform specific functions at the molecular scale through the application of various stimuli is highly attractive but still challenging. The most recent applications indicate that the outstanding flexibility of self-assembled architectures can be employed as a powerful tool for the development of innovative molecular devices, functional surfaces and smart nanomaterials. Structural flexibility of these materials is known to be conferred by weak intermolecular forces involved in self-assembly strategies. However, some fundamental mechanisms responsible for conformational lability remain unexplored. Furthermore, the role played by stronger bonds, such as coordination, ionic and covalent bonding, is sometimes neglected while they can be employed readily to produce mechanically robust but also chemically reversible structures. In this review, recent applications of structural flexibility and molecular motions in self-assembled nanostructures are discussed. Special focus is given to advanced materials exhibiting significant performance changes after an external stimulus is applied, such as light exposure, pH variation, heat treatment or electromagnetic field. The crucial role played by strong intra- and weak intermolecular interactions on structural lability and responsiveness is highlighted. PMID:23348927

  14. Intercalators as molecular chaperones in DNA self-assembly.

    PubMed

    Greschner, Andrea A; Bujold, Katherine E; Sleiman, Hanadi F

    2013-07-31

    DNA intercalation has found many diagnostic and therapeutic applications. Here, we propose the use of simple DNA intercalators, such as ethidium bromide, as tools to facilitate the error-free self-assembly of DNA nanostructures. We show that ethidium bromide can influence DNA self-assembly, decrease the formation of oligomeric side products, and cause libraries of multiple equilibrating structures to converge into a single product. Using a variety of 2D- and 3D-DNA systems, we demonstrate that intercalators present a powerful alternative for the adjustment of strand-end alignment, favor the formation of fully duplexed "closed" structures, and create an environment where the smallest, most stable structure is formed. A new 3D-DNA motif, the ninja star, was self-assembled in quantitative yield with this method. Moreover, ethidium bromide can be readily removed using isoamyl alcohol extractions combined with intercalator-specific spin columns, thereby yielding the desired ready-to-use DNA structure. PMID:23829631

  15. Dynamic self-assembly and control of microfluidic particle crystals

    PubMed Central

    Lee, Wonhee; Amini, Hamed; Stone, Howard A.; Di Carlo, Dino

    2010-01-01

    Engineered two-phase microfluidic systems have recently shown promise for computation, encryption, and biological processing. For many of these systems, complex control of dispersed-phase frequency and switching is enabled by nonlinearities associated with interfacial stresses. Introducing nonlinearity associated with fluid inertia has recently been identified as an easy to implement strategy to control two-phase (solid-liquid) microscale flows. By taking advantage of inertial effects we demonstrate controllable self-assembling particle systems, uncover dynamics suggesting a unique mechanism of dynamic self-assembly, and establish a framework for engineering microfluidic structures with the possibility of spatial frequency filtering. Focusing on the dynamics of the particle–particle interactions reveals a mechanism for the dynamic self-assembly process; inertial lift forces and a parabolic flow field act together to stabilize interparticle spacings that otherwise would diverge to infinity due to viscous disturbance flows. The interplay of the repulsive viscous interaction and inertial lift also allow us to design and implement microfluidic structures that irreversibly change interparticle spacing, similar to a low-pass filter. Although often not considered at the microscale, nonlinearity due to inertia can provide a platform for high-throughput passive control of particle positions in all directions, which will be useful for applications in flow cytometry, tissue engineering, and metamaterial synthesis. PMID:21149674

  16. Self-assembly of amphiphilic dendritic dipeptides into helical pores

    NASA Astrophysics Data System (ADS)

    Percec, Virgil; Dulcey, Andrés E.; Balagurusamy, Venkatachalapathy S. K.; Miura, Yoshiko; Smidrkal, Jan; Peterca, Mihai; Nummelin, Sami; Edlund, Ulrica; Hudson, Steven D.; Heiney, Paul A.; Duan, Hu; Magonov, Sergei N.; Vinogradov, Sergei A.

    2004-08-01

    Natural pore-forming proteins act as viral helical coats and transmembrane channels, exhibit antibacterial activity and are used in synthetic systems, such as for reversible encapsulation or stochastic sensing. These diverse functions are intimately linked to protein structure. The close link between protein structure and protein function makes the design of synthetic mimics a formidable challenge, given that structure formation needs to be carefully controlled on all hierarchy levels, in solution and in the bulk. In fact, with few exceptions, synthetic pore structures capable of assembling into periodically ordered assemblies that are stable in solution and in the solid state have not yet been realized. In the case of dendrimers, covalent and non-covalent coating and assembly of a range of different structures has only yielded closed columns. Here we describe a library of amphiphilic dendritic dipeptides that self-assemble in solution and in bulk through a complex recognition process into helical pores. We find that the molecular recognition and self-assembly process is sufficiently robust to tolerate a range of modifications to the amphiphile structure, while preliminary proton transport measurements establish that the pores are functional. We expect that this class of self-assembling dendrimers will allow the design of a variety of biologically inspired systems with functional properties arising from their porous structure.

  17. Self-assembly of strongly dipolar molecules on metal surfaces.

    PubMed

    Kunkel, Donna A; Hooper, James; Simpson, Scott; Miller, Daniel P; Routaboul, Lucie; Braunstein, Pierre; Doudin, Bernard; Beniwal, Sumit; Dowben, Peter; Skomski, Ralph; Zurek, Eva; Enders, Axel

    2015-03-14

    The role of dipole-dipole interactions in the self-assembly of dipolar organic molecules on surfaces is investigated. As a model system, strongly dipolar model molecules, p-benzoquinonemonoimine zwitterions (ZI) of type C6H2(??NHR)2(??O)2 on crystalline coinage metal surfaces were investigated with scanning tunneling microscopy and first principles calculations. Depending on the substrate, the molecules assemble into small clusters, nano gratings, and stripes, as well as in two-dimensional islands. The alignment of the molecular dipoles in those assemblies only rarely assumes the lowest electrostatic energy configuration. Based on calculations of the electrostatic energy for various experimentally observed molecular arrangements and under consideration of computed dipole moments of adsorbed molecules, the electrostatic energy minimization is ruled out as the driving force in the self-assembly. The structures observed are mainly the result of a competition between chemical interactions and substrate effects. The substrate's role in the self-assembly is to (i) reduce and realign the molecular dipole through charge donation and back donation involving both the molecular HOMO and LUMO, (ii) dictate the epitaxial orientation of the adsorbates, specifically so on Cu(111), and (iii) inhibit attractive forces between neighboring chains in the system ZI/Cu(111), which results in regularly spaced molecular gratings. PMID:25770510

  18. Self-assembly in sugar-oil complex glasses

    NASA Astrophysics Data System (ADS)

    Dave, Hiteshkumar; Gao, Feng; Lee, Jing-Huei; Liberatore, Matthew; Ho, Chia-Chi; Co, Carlos C.

    2007-04-01

    In aqueous systems, the hydrophobic effect drives the self-assembly of amphiphiles into a broad range of micellar, rod-like, bicontinuous and liquid-crystalline complex fluids. Many of these are relevant to biological matter or technological applications. However, amphiphilic self-assembly is not limited to aqueous systems. Replacement of water with supercritical carbon dioxide, for example, results in complex fluids that combine the properties of gases and liquids. Along this vein, we explore the self-assembly of surfactants in anhydrous sugars. Our study reveals that anhydrous powders of sugars and surfactants suspended in oil spontaneously form molten glasses with nanometre-size domains of sugar and liquid oil without mixing. The low cost, water solubility, low toxicity and stabilizing properties of glassy sugars make them ideal water replacements for many pharmaceutical, food and materials synthesis applications. The optical clarity and solid appearance of these glasses at room temperature belie their inclusion of more than 50% (vol.) oil, which confers liquid-like diffusivity. The unique combination of solid- and liquid-like properties may lead to applications in sensors and optical devices.

  19. Fractal Dimension Analysis in Self-Assembled Poly(dA)·poly(dT) DNA Network on Mica Surface

    NASA Astrophysics Data System (ADS)

    Kawano, Satoyuki

    Characteristics of the self-assembled poly(dA)·poly(dT) DNA network adhered on the mica substrate are experimentally investigated based on the AFM observations and the fractal dimension analysis. Artificial B-type double stranded DNA, which consists of 50 base pairs of adenine and thymine, is specially prepared for the experiment. The manufacturing process of DNA network is done in the aqueous solution of poly(dA)·poly(dT) DNA, and the systematical experimental runs are made for various concentration of the solution. It is found that the 2D fractal dimension strongly depends on the fabrication process of the DNA network.

  20. Theoretical Studies on Excitation Energy Fluctuations of Pigments in a Light-Harvesting Complex

    NASA Astrophysics Data System (ADS)

    Higashi, Masahiro; Saito, Shinji

    2014-03-01

    Excitation energy fluctuations of pigments in light-harvesting complexes play an important role in the excitation energy transfer dynamics. It is considered that protein environment controls the excitation energy fluctuation to maximize the efficiency of excitation energy transfer. However, the detailed mechanism is still unknown. The high computational cost of reliable electronic structure calculations for excited states prevents us from carrying out a large number of sampling needed to evaluate the excitation energy fluctuations. To overcome this difficulty, we develop a new method called molecular mechanics with Shepard interpolation corrections (MMSIC), which enable us to generate potential energy surfaces for pigments in light-harvesting complexes efficiently. We illustrate the new method by application to bacteriochlorophyll a pigments in the Fenna-Matthews-Olson complex. The MMSIC calculations are more than a million times faster than the direct electronic structure calculations, and the calculated results are in good agreement with the experimental results.

  1. Anti-Correlated Pigment Fluctuations of Allophycocyanin for Highly Efficient Photosynthetic Light Harvesting in Cyanobacteria

    NASA Astrophysics Data System (ADS)

    Moran, Andrew; Nome, Rene; Scherer, Norbert

    2008-03-01

    The phycobiliprotein, allophycocyanin (APC), is an excellent model system for the study of light harvesting pigment interactions with a protein bath. This work investigates the relaxation of electronic excitations in APC with electric field-resolved transient grating and photon echo spectroscopies. Transient grating experiments observe a 35 fs internal conversion process between single exciton levels. Most importantly, our analysis shows that anti-correlated phycocyanobilin pigment energy level fluctuations cause the anti-diagonal orientation of the node in the measured dispersive photon echo spectrum. We believe this novel observation to reflect concerted protein bath fluctuations over the 2 nm length scale that separates the pigments. Consideration of the Forster energy transfer rate theory suggests that APC has evolved with this property to enhance its photosynthetic light harvesting efficiency.

  2. ARCHITECTURE OF A CHARGE-TRANSFER STATE REGULATING LIGHT HARVESTING IN A PLANT ANTENNA PROTEIN

    SciTech Connect

    Fleming, Graham; Ahn, Tae Kyu; Avenson, Thomas J.; Ballottari, Matteo; Cheng, Yuan-Chung; Niyogi, Krishna K.; Bassi, Roberto; Fleming, Graham R.

    2008-04-02

    Energy-dependent quenching of excess absorbed light energy (qE) is a vital mechanism for regulating photosynthetic light harvesting in higher plants. All of the physiological characteristics of qE have been positively correlated with charge-transfer between coupled chlorophyll and zeaxanthin molecules in the light-harvesting antenna of photosystem II (PSII). In this work, we present evidence for charge-transfer quenching in all three of the individual minor antenna complexes of PSII (CP29, CP26, and CP24), and we conclude that charge-transfer quenching in CP29 involves a de-localized state of an excitonically coupled chlorophyll dimer. We propose that reversible conformational changes in CP29 can `tune? the electronic coupling between the chlorophylls in this dimer, thereby modulating the energy of the chlorophylls-zeaxanthin charge-transfer state and switching on and off the charge-transfer quenching during qE.

  3. Nature-inspired light-harvesting liquid crystalline porphyrins for organic photovoltaics

    SciTech Connect

    Li, Lanfang; Kang, Shin-Woong; Harden, John; Sun, Qingjiang; Zhou, Xiaoli; Dai, Liming; Jakli, Antal; Kumar, Satyendra; Li, Quan (NSF); (Kent); (Dayton)

    2008-12-22

    A new class of nanoscale light-harvesting discotic liquid crystalline porphyrins, with the same basic structure of the best photoreceptor in nature (chlorophyll), was synthesized. These materials can be exceptionally aligned into a highly ordered architecture in which the columns formed by intermolecular {pi}-{pi} stacking are spontaneously perpendicular to the substrate. The homeotropic alignment, well confirmed by synchrotron X-ray diffraction, could not only provide the most efficient pathway for hole conduction along the columnar axis crossing the device thickness, but also offer the largest area to the incident light for optimized light harvesting. Their preliminary photocurrent generation and photovoltaic performances were also demonstrated. The results provide new and efficient pathways to the development of organic photovoltaics by using homeotropically aligned liquid crystal thin films.

  4. Molecular design of the photosystem II light-harvesting antenna: photosynthesis and photoprotection.

    PubMed

    Horton, Peter; Ruban, Alexander

    2005-01-01

    The photosystem II (PSII) light-harvesting system carries out two essential functions, the efficient collection of light energy for photosynthesis, and the regulated dissipation of excitation energy in excess of that which can be used. This dual function requires structural and functional flexibility, in which light-harvesting proteins respond to an external signal, the thylakoid DeltapH, to induce feedback control. This process, referred to as non-photochemical quenching (NPQ) depends upon the xanthophyll cycle and the PsbS protein. In nature, NPQ is heterogeneous in terms of kinetics and capacity, and this adapts photosynthetic systems to the specific dynamic features of the light environment. The molecular features of the thylakoid membrane which may enable this flexibility and plasticity are discussed. PMID:15557295

  5. Guided self-assembly of molecular dipoles on a substrate surface Y. F. Gao and Z. Suoa)

    E-print Network

    Suo, Zhigang

    can self-assemble into a monolayer. This article models the process of self-assembly guidedGuided self-assembly of molecular dipoles on a substrate surface Y. F. Gao and Z. Suoa) Department on the substrate surface, interact with one another through the intermolecular force, and self-assemble

  6. Scanning probe lithography of self-assembled monolayers Guohua Yang, Nabil A. Amro, Gang-yu Liu*

    E-print Network

    Liu, Gang-yu

    Scanning probe lithography of self-assembled monolayers Guohua Yang, Nabil A. Amro, Gang-yu Liu probe lithography (SPL) methodologies have been performed using self-assembled monolayers (SAMs) on Au, nanofabrication, thiol, self-assembled monolayers 1. INTRODUCTION Micro- and nano-fabrication of self-assembled

  7. Self-Assembly of biologically inspired complex functional materials.

    SciTech Connect

    Brinker, C. Jeffrey

    2004-08-01

    Nature combines hard and soft materials, often in hierarchical architectures, to get synergistic, optimized properties with proven, complex functionalities. Emulating such natural designs in robust engineering materials using efficient processing approaches represents a fundamental challenge to materials chemists. This presentation will review progress on understanding so-called 'evaporation-induced silica/surfactant self-assembly' (EISA) as a simple, general means to prepare porous thin-film nanostructures. Such porous materials are of interest for membranes, low-dielectric-constant (low-k) insulators, and even 'nano-valves' that open and close in response to an external stimulus. EISA can also be used to simultaneously organize hydrophilic and hydrophobic precursors into hybrid nanocomposites that are optically or chemically polymerizable, patternable, or adjustable. In constructing composite structures, a significant challenge is how to controllably organize or define multiple materials on multiple length scales. To address this challenge, we have combined sol-gel chemistry with molecular self-assembly in several evaporation-driven processing procedures collectively referred to as evaporation-induced self-assembly (EISA). EISA starts with a silica/water/surfactant system diluted with ethanol to create a homogeneous solution. We rely on ethanol and water evaporation during dip-coating (or other coating methods) to progressively concentrate surfactant and silica in the depositing film, driving micelle formation and subsequent continuous self-assembly of silica/surfactant thin film mesophases. One of the crucial aspects of this process, in terms of the sol-gel chemistry, is to work under conditions where the condensation rate of the hydrophilic silicic acid precursors (Si-OH) is minimized. The idea is to avoid gelation that would kinetically trap the system at an intermediate non-equilibrium state. We want the structure to self-assemble then solidify, with the addition of a siloxane condensation catalyst or by heating, to form the desired mesostructured product. Operating at an acidic pH (pH = 2) minimizes the condensation rate of silanols to form siloxanes Si-O-SiIn addition, hydrogen bonding and electrostatic interactions between silanols and hydrophilic surfactant head groups can further reduce the condensation rate. These combined factors maintain the depositing film in a fluid state, even beyond the point where ethanol and water are largely evaporated. This allows the deposited film to be self-healing and enables the use of virtually any evaporation-driven process (spin-coating, inkjet printing, or aerosol processing) to create ordered nanostructured films, patterns, or particles.

  8. Nanosized gradient pi-conjugated thienylethynylene dendrimers for light harvesting: synthesis and properties.

    PubMed

    Wang, Jin-Liang; Luo, Jia; Liu, Liang-Hui; Zhou, Qi-Feng; Ma, Yuguo; Pei, Jian

    2006-05-25

    [reaction: see text] A family of pi-conjugated dendrimers based on truxene and thienylethynylene units are synthesized via a mixed divergent/convergent growth approach. These dendrimers possess an intrinsic energy gradient from the periphery to the core through branches and thus show a broad absorption in the UV-vis range and an efficient energy transfer to the lower-energy center. The molecules hence have the potential to be used as light harvesting materials. PMID:16706506

  9. Supermolecular organization of photosystem II and its associated light-harvesting antenna in Arabidopsis thaliana

    Microsoft Academic Search

    Egbert J. Boekema; Henrik V. Scheller; Henny van Roon; Wilko Keegstra; Poul E. Jensen; Alevtyna E. Yakushevska; Jan P. Dekker

    2001-01-01

    The organization of Arabidopsis thaliana photosystem II (PSII) and its associated light-harvesting antenna (LHCII) was studied in isolated PSII–LHCII supercomplexes and native membrane-bound crystals by transmission electron microscopy and image analysis. Over 4000 single-particle projections of PSII–LHCII supercomplexes were analyzed. In comparison to spinach supercomplexes some striking differences were revealed: a much larger number of supercomplexes from Arabidopsis contain copies

  10. Association of Photosystem I and Light-Harvesting Complex II during State Transitions

    Microsoft Academic Search

    Egbert J. Boekema; Roman Kou?il; Jan P. Dekker; Poul Erik Jensen

    2006-01-01

    Green plant photosystem I (PS I) not only binds a chlorophyll a\\/b-binding, membrane-intrinsic antenna complex (LHCI) that is associated with the PS I core complex under almost all physiological\\u000a conditions, but it can also transiently bind the major chlorophyll a\\/b-binding light-harvesting complex (LHCII), when the light conditions favor excitation of photosystem II (PS II) and the photosynthetic\\u000a apparatus is in

  11. Single-molecule exploration of photoprotective mechanisms in light-harvesting complexes

    NASA Astrophysics Data System (ADS)

    Yang, Hsiang-Yu; Schlau-Cohen, Gabriela S.; Gwizdala, Michal; Krüger, Tjaart; Xu, Pengqi; Croce, Roberta; van Grondelle, Rienk; Moerner, W. E.

    2015-03-01

    Plants harvest sunlight by converting light energy to electron flow through the primary events in photosynthesis. One important question is how the light harvesting machinery adapts to fluctuating sunlight intensity. As a result of various regulatory processes, efficient light harvesting and photoprotection are balanced. Some of the biological steps in the photoprotective processes have been extensively studied and physiological regulatory factors have been identified. For example, the effect of lumen pH in changing carotenoid composition has been explored. However, the importance of photophysical dynamics in the initial light-harvesting steps and its relation to photoprotection remain poorly understood. Conformational and excited-state dynamics of multi-chromophore pigment-protein complexes are often difficult to study and limited information can be extracted from ensemble-averaged measurements. To address the problem, we use the Anti-Brownian ELectrokinetic (ABEL) trap to investigate the fluorescence from individual copies of light-harvesting complex II (LHCII), the primary antenna protein in higher plants, in a solution-phase environment. Perturbative surface immobilization or encapsulation schemes are avoided, and therefore the intrinsic dynamics and heterogeneity in the fluorescence of individual proteins are revealed. We perform simultaneous measurements of fluorescence intensity (brightness), excited-state lifetime, and emission spectrum of single trapped proteins. By analyzing the correlated changes between these observables, we identify forms of LHCII with different fluorescence intensities and excited-state lifetimes. The distinct forms may be associated with different energy dissipation mechanisms in the energy transfer chain. Changes of relative populations in response to pH and carotenoid composition are observed, which may extend our understanding of the molecular mechanisms of photoprotection.

  12. Identification of Proton-Active Residues in a Higher Plant Light-Harvesting Complex

    Microsoft Academic Search

    Robin G. Walters; Alexander V. Ruban; Peter Horton

    1996-01-01

    The thermal dissipation of absorbed light energy by the light-harvesting apparatus of higher plants is important in protecting the photosynthetic machinery from the effects of excess illumination. A major mechanism for such photoprotection, known as trans-thylakoid Delta pH-dependent chlorophyll fluorescence quenching (qE), is induced by acidification of the lumen, is correlated with the interconversion of xanthophyll pigments, and is manifested

  13. A thioredoxin-like/?-propeller protein maintains the efficiency of light harvesting in Arabidopsis

    PubMed Central

    Brooks, Matthew D.; Sylak-Glassman, Emily J.; Fleming, Graham R.; Niyogi, Krishna K.

    2013-01-01

    The light-harvesting complexes of plants have evolved the ability to switch between efficient light harvesting and quenching forms to optimize photosynthesis in response to the environment. Several distinct mechanisms, collectively termed “nonphotochemical quenching” (NPQ), provide flexibility in this response. Here we report the isolation and characterization of a mutant, suppressor of quenching 1 (soq1), that has high NPQ even in the absence of photosystem II subunit S (PsbS), a protein that is necessary for the rapidly reversible component of NPQ. The formation of NPQ in soq1 was light intensity-dependent, and it exhibited slow relaxation kinetics and other characteristics that distinguish it from known NPQ components. Treatment with chemical inhibitors or an uncoupler, as well as crosses to mutants known to affect other NPQ components, showed that the NPQ in soq1 does not require a transthylakoid pH gradient, zeaxanthin formation, or the phosphorylation of light-harvesting complexes, and it appears to be unrelated to the photosystem II damage-and-repair cycle. Measurements of pigments and chlorophyll fluorescence lifetimes indicated that the additional NPQ in soq1 is the result of a decrease in chlorophyll excited-state lifetime and not pigment bleaching. The SOQ1 gene was isolated by map-based cloning, and it encodes a previously uncharacterized thylakoid membrane protein with thioredoxin-like and ?-propeller domains located in the lumen and a haloacid-dehalogenase domain exposed to the chloroplast stroma. We propose that the role of SOQ1 is to prevent formation of a slowly reversible form of antenna quenching, thereby maintaining the efficiency of light harvesting. PMID:23818601

  14. Two-dimensional electronic spectroscopy and photosynthesis: Fundamentals and applications to photosynthetic light-harvesting

    Microsoft Academic Search

    Gabriela S. Schlau-Cohen; Akihito Ishizaki; Graham R. Fleming

    2011-01-01

    In natural light harvesting systems, pigment-protein complexes are able to harvest sunlight with near unity quantum efficiency. These complexes exhibit emergent properties that cannot be simply extrapolated from knowledge of their component parts. In this perspective, we focus on how two-dimensional electronic spectroscopy (2DES) can provide an incisive tool to probe the electronic, energetic, and spatial landscapes that must be

  15. Structural and functional diversification of the light-harvesting complexes in photosynthetic eukaryotes

    Microsoft Academic Search

    Jonathan A. D. Neilson; Dion G. Durnford

    2010-01-01

    Eukaryotes acquired photosynthetic metabolism over a billion years ago, and during that time the light-harvesting antennae\\u000a have undergone significant structural and functional divergence. The antenna systems are generally used to harvest and transfer\\u000a excitation energy into the reaction centers to drive photosynthesis, but also have the dual role of energy dissipation. Phycobilisomes\\u000a formed the first antenna system in oxygenic photoautotrophs,

  16. Reaction center and light-harvesting I genes from Rhodopseudomonas capsulatta

    Microsoft Academic Search

    D. C. Youvan; M. Alberti; H. Begusch; E. J. Bylina; J. E. Hearst

    1984-01-01

    Five structural genes coding for the reaction center (RC) L, M, and H subunits and the two light-harvesting (LH) I polypeptides, B870..cap alpha.. and B870..beta.., have been mapped on two restriction fragments from the R-prime plasmid pRPS404. It has been recently shown that enhanced near-infrared fluorescence mutants of Rhodopseudomonas capsulata typically lack RC or LH I polypeptides and that these

  17. AFM Characterization of Tilt and Intrinsic Flexibility of Rhodobacter sphaeroides Light Harvesting Complex 2 (LH2)

    Microsoft Academic Search

    Simon Scheuring; Jerome Seguin; Sergio Marco; Daniel Lévy; Cécile Breyton; Bruno Robert; Jean-Louis Rigaud

    2003-01-01

    Atomic force microscopy (AFM) has developed into a powerful tool to investigate membrane protein surfaces in a close-to-native environment. Here we report on the surface topography of Rhodobacter sphaeroides light harvesting complex 2 (LH2) reconstituted into two-dimensional crystals. These photosynthetic trans-membrane proteins formed cylindrical oligomeric complexes, which inserted tilted into the lipid membrane. This peculiar packing of an integral membrane

  18. Self-assembly triggered by self-assembly: optically active, paramagnetic micelles encapsulated in protein cage nanoparticles.

    PubMed

    Millán, Jealemy Galindo; Brasch, Melanie; Anaya-Plaza, Eduardo; de la Escosura, Andrés; Velders, Aldrik H; Reinhoudt, David N; Torres, Tomás; Koay, Melissa S T; Cornelissen, Jeroen J L M

    2014-07-01

    In this contribution, optically active and paramagnetic micelles of the ligand 1,4,7,10-tetraaza-1-(1-carboxymethylundecane)-4,7,10-triacetic acid cyclododecane (DOTAC10) have been incorporated inside capsids of the cowpea chlorotic mottle virus (CCMV) protein through a hierarchical process of self-assembly triggered by self-assembly. The DOTAC10 ligand was used to complex Gd(III), in order to form paramagnetic micelles, as well as to encapsulate an amphiphilic Zn(II) phthalocyanine (ZnPc) dye that optically confirmed the encapsulation of the micelles. The incorporation of ZnPc molecules in the paramagnetic micelles led to high capsid loading of both Gd(III) and ZnPc, as the micelles were stabilized by the amphiphilic dye encapsulation. The resulting protein cage nanoparticles (PCNs) show an improved r1 relaxivity, suggesting the possible use of these nanostructures as contrast agents (CAs) for magnetic resonance imaging (MRI). Since the encapsulated ZnPc dye also has a potential therapeutic value, the present results represent a first step towards the consecution of fully self-assembled PCNs for multimodal imaging and therapy. PMID:24513535

  19. Combustion and self-assembly of nanoenergetic materials

    NASA Astrophysics Data System (ADS)

    Malchi, Jonathan Yaniv

    The recent worldwide interest in nanotechnology spans a wide variety of scientific fields such as electronics, biology, materials science and medicine. Because of their extremely small dimensions, nanoparticles demonstrate properties different from matter at larger scales. Understanding these unusual properties and utilizing them for macroscale devices is an overall goal for nanotechnology. Moreover, manipulating these small particles into organized structures is crucial for taking full advantage of what nanotechnology has to offer, however it has proven to be a difficult task. Recent work utilizing electrostatic forces shows great potential for the self-assembly of nanoparticles into organized two-dimensional and three-dimensional structures. Overall, this work examines how nanotechnology and self-assembly can benefit the field of energetic materials. Because of aluminum's high energy density and low cost, it has been used in the field of energetic materials for several decades. In order to achieve sufficient energy release rates, aluminum is typically manufactured as a powder having spherical particles with diameters on the micron scale. It is well-known that decreasing the original particle diameter of a fuel particle will increase the burning time and, thus, energy release rate. Therefore, aluminum particles have recently been made to have diameters on the nanoscale, and shown to be advantageous for several applications. The combustion of nanoaluminum (nAl) in various systems is the primary focus of this study. A progression of experiments is used to analyze the combustion of nAl: (1) a fully heterogeneous flame spread system, (2) a semi-homogeneous sonicated thermite system and (3) a quasi-homogeneous self-assembled thermite system. The flame spread experiment physically separates the nAl from the gaseous oxidizer allowing for a well-understood convective, diffusive, reactive system to be analyzed. Because of the simplicity of the experimental setup, variables are easily changed and their effects on the flame spread rate are observed. Overall, spread rates are 2 to 3 orders of magnitude greater than what is demonstrated with typical solid fuels due to the high reactivity of the nAl. This large difference in spread rate brings about a fingering combustion instability in normal gravity conditions that has only been shown to occur in microgravity conditions. Moreover, a stability map is created based on the nondimensional Lewis and Damkohler numbers that predicts when a continuous flame front will transition to a fingering instability. This, along with the various other trends, is predicted using a simple scaling analysis. A nanoscale thermite is created via sonication of nAl and nanocopper-oxide (nCuO) particles. Although the mixture is unorganized and random, these materials boast extremely exothermic reactions with propagation rates on the order of 1 km/s. Experiments are performed to examine the effect of adding a diluent to the system. Two types of materials are added, a stable end product, aluminum-oxide, and long alkyl chain hydrocarbons. Both materials severely hinder the propagation rate, however, experiments suggest that hydrocarbon addition could help with the material's sensitivity to electrostatic discharge. Equilibrium calculations suggest that a dual temperature and gas production criteria must be met to allow for the convective propagation mechanism to take place and fast propagation rates to occur. Because of the hydrocarbons required for self-assembly, these experiments also give an indication of how the self-assembled material will react. To electrostatically self-assemble a nAl/nCuO thermite, the constituents are first coated with an o-functionalized alkyl chain ligand and suspended in a separate solutions. Upon mixing, the opposite electrostatic charges agglomerate the two constituents, which subsequently precipitate out of solution. Analyzing the material with Scanning Electron Microscopy shows that a portion has self-assembled into microspheres having diameters from 1-5mum. This is the first know

  20. Metal-Enhanced Fluorescence of Chlorophylls in Light-Harvesting Complexes Coupled to Silver Nanowires

    PubMed Central

    Kowalska, Dorota; Krajnik, Bartosz; Olejnik, Maria; Czechowski, Nikodem; Mackowski, Sebastian

    2013-01-01

    We investigate metal-enhanced fluorescence of peridinin-chlorophyll protein coupled to silver nanowires using optical microscopy combined with spectrally and time-resolved fluorescence techniques. In particular we study two different sample geometries: first, in which the light-harvesting complexes are deposited onto silver nanowires, and second, where solution of both nanostructures are mixed prior deposition on a substrate. The results indicate that for the peridinin-chlorophyll complexes placed in the vicinity of the silver nanowires we observe higher intensities of fluorescence emission as compared to the reference sample, where no nanowires are present. Enhancement factors estimated for the sample where the light-harvesting complexes are mixed together with the silver nanowires prior deposition on a substrate are generally larger in comparison to the other geometry of a hybrid nanostructure. While fluorescence spectra are identical both in terms of overall shape and maximum wavelength for peridinin-chlorophyll-protein complexes both isolated and coupled to metallic nanostructures, we conclude that interaction with plasmon excitations in the latter remains neutral to the functionality of the biological system. Fluorescence transients measured for the PCP complexes coupled to the silver nanowires indicate shortening of the fluorescence lifetime pointing towards modifications of radiative rate due to plasmonic interactions. Our results can be applied for developing ways to plasmonically control the light-harvesting capability of photosynthetic complexes. PMID:23533354

  1. Efficient light harvesting by photosystem II requires an optimized protein packing density in Grana thylakoids.

    PubMed

    Haferkamp, Silvia; Haase, Winfried; Pascal, Andrew A; van Amerongen, Herbert; Kirchhoff, Helmut

    2010-05-28

    A recently developed technique for dilution of the naturally high protein packing density in isolated grana membranes was applied to study the dependence of the light harvesting efficiency of photosystem (PS) II on macromolecular crowding. Slight dilution of the protein packing from 80% area fraction to the value found in intact grana thylakoids (70%) leads to an improved functionality of PSII (increased antenna size, enhanced connectivity between reaction centers). Further dilution induces a functional disconnection of light-harvesting complex (LHC) II from PSII. It is concluded that efficient light harvesting by PSII requires an optimal protein packing density in grana membranes that is close to 70%. We hypothesize that the decreased efficiency in overcrowded isolated grana thylakoids is caused by excited state quenching in LHCII, which has previously been correlated with neoxanthin distortion. Resonance Raman spectroscopy confirms this increase in neoxanthin distortion in overcrowded grana as compared with intact thylakoids. Furthermore, analysis of the changes in the antenna size in highly diluted membranes indicates a lipid-induced dissociation of up to two trimeric LHCII from PSII, leaving one trimer connected. This observation supports a hierarchy of LHCII-binding sites on PSII. PMID:20360011

  2. Metal-enhanced fluorescence of chlorophylls in light-harvesting complexes coupled to silver nanowires.

    PubMed

    Kowalska, Dorota; Krajnik, Bartosz; Olejnik, Maria; Twardowska, Magdalena; Czechowski, Nikodem; Hofmann, Eckhard; Mackowski, Sebastian

    2013-01-01

    We investigate metal-enhanced fluorescence of peridinin-chlorophyll protein coupled to silver nanowires using optical microscopy combined with spectrally and time-resolved fluorescence techniques. In particular we study two different sample geometries: first, in which the light-harvesting complexes are deposited onto silver nanowires, and second, where solution of both nanostructures are mixed prior deposition on a substrate. The results indicate that for the peridinin-chlorophyll complexes placed in the vicinity of the silver nanowires we observe higher intensities of fluorescence emission as compared to the reference sample, where no nanowires are present. Enhancement factors estimated for the sample where the light-harvesting complexes are mixed together with the silver nanowires prior deposition on a substrate are generally larger in comparison to the other geometry of a hybrid nanostructure. While fluorescence spectra are identical both in terms of overall shape and maximum wavelength for peridinin-chlorophyll-protein complexes both isolated and coupled to metallic nanostructures, we conclude that interaction with plasmon excitations in the latter remains neutral to the functionality of the biological system. Fluorescence transients measured for the PCP complexes coupled to the silver nanowires indicate shortening of the fluorescence lifetime pointing towards modifications of radiative rate due to plasmonic interactions. Our results can be applied for developing ways to plasmonically control the light-harvesting capability of photosynthetic complexes. PMID:23533354

  3. Antheraxanthin, a light harvesting carotenoid found in a chromophyte alga. [Chrysophaera magna Becher, Phaeodactylum tricornutum

    SciTech Connect

    Alberte, R.S.; Andersen, R.A.

    1986-02-01

    The pigments of the chromophyte freshwater alga, Chrysophaera magna Belcher were analyzed by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) to reveal the presence of chlorophylls a and c, ..beta..-carotene, fucoxanthin, and antheraxanthin. The presence of antheraxanthin was verified by comparison of TLC R/sub F/ values, HPLC retention times, and absorption features to those of authentic, synthetic antheraxanthin. Antheraxanthin accounted for about 15% of the total carotenoid content of C. magna. The molar ratio of the major carotenoids was antheraxanthin:fucoxanthin:..beta..-carotene, 1:2.3:3.3. The whole-cell absorption spectrum revealed a broad band between 470 and 520 nanometers which was attributed to fucoxanthin and antheraxanthin in vivo. Upon extraction in hydrocarbon, this broad absorption region was lost. The in vivo fluorescence excitation spectrum for 680 nm emission revealed the energy transfer activities and light harvesting roles of chlorophylls a and c, and fucoxanthin. In addition, an excitation band was resolved at 487 nanometers which could be attributed only to antheraxanthin. Comparison of whole-cell fluorescence excitation spectra of C. magna with the diatom Phaeodactylum tricornutum, which possesses fucoxanthin but not antheraxanthin, supports the assignment of the 487 nm band to antheraxanthin. This is the first report of a photosynthetic light harvesting function of the xanthophyll, antheraxanthin. This carotenoid broadens the absorption cross-section for photosynthesis in C. magna and extends light harvesting into the green portion of the spectrum.

  4. Direct evidence of quantum transport in photosynthetic light-harvesting complexes

    PubMed Central

    Panitchayangkoon, Gitt; Voronine, Dmitri V.; Abramavicius, Darius; Caram, Justin R.; Lewis, Nicholas H. C.; Mukamel, Shaul; Engel, Gregory S.

    2011-01-01

    The photosynthetic light-harvesting apparatus moves energy from absorbed photons to the reaction center with remarkable quantum efficiency. Recently, long-lived quantum coherence has been proposed to influence efficiency and robustness of photosynthetic energy transfer in light-harvesting antennae. The quantum aspect of these dynamics has generated great interest both because of the possibility for efficient long-range energy transfer and because biology is typically considered to operate entirely in the classical regime. Yet, experiments to date show only that coherence persists long enough that it can influence dynamics, but they have not directly shown that coherence does influence energy transfer. Here, we provide experimental evidence that interaction between the bacteriochlorophyll chromophores and the protein environment surrounding them not only prolongs quantum coherence, but also spawns reversible, oscillatory energy transfer among excited states. Using two-dimensional electronic spectroscopy, we observe oscillatory excited-state populations demonstrating that quantum transport of energy occurs in biological systems. The observed population oscillation suggests that these light-harvesting antennae trade energy reversibly between the protein and the chromophores. Resolving design principles evident in this biological antenna could provide inspiration for new solar energy applications. PMID:22167798

  5. Live visualizations of single isolated tubulin protein self-assembly via tunneling current: effect of electromagnetic pumping during spontaneous growth of microtubule

    NASA Astrophysics Data System (ADS)

    Sahu, Satyajit; Ghosh, Subrata; Fujita, Daisuke; Bandyopadhyay, Anirban

    2014-12-01

    As we bring tubulin protein molecules one by one into the vicinity, they self-assemble and entire event we capture live via quantum tunneling. We observe how these molecules form a linear chain and then chains self-assemble into 2D sheet, an essential for microtubule, --fundamental nano-tube in a cellular life form. Even without using GTP, or any chemical reaction, but applying particular ac signal using specially designed antenna around atomic sharp tip we could carry out the self-assembly, however, if there is no electromagnetic pumping, no self-assembly is observed. In order to verify this atomic scale observation, we have built an artificial cell-like environment with nano-scale engineering and repeated spontaneous growth of tubulin protein to its complex with and without electromagnetic signal. We used 64 combinations of plant, animal and fungi tubulins and several doping molecules used as drug, and repeatedly observed that the long reported common frequency region where protein folds mechanically and its structures vibrate electromagnetically. Under pumping, the growth process exhibits a unique organized behavior unprecedented otherwise. Thus, ``common frequency point'' is proposed as a tool to regulate protein complex related diseases in the future.

  6. Live visualizations of single isolated tubulin protein self-assembly via tunneling current: effect of electromagnetic pumping during spontaneous growth of microtubule.

    PubMed

    Sahu, Satyajit; Ghosh, Subrata; Fujita, Daisuke; Bandyopadhyay, Anirban

    2014-01-01

    As we bring tubulin protein molecules one by one into the vicinity, they self-assemble and entire event we capture live via quantum tunneling. We observe how these molecules form a linear chain and then chains self-assemble into 2D sheet, an essential for microtubule, --fundamental nano-tube in a cellular life form. Even without using GTP, or any chemical reaction, but applying particular ac signal using specially designed antenna around atomic sharp tip we could carry out the self-assembly, however, if there is no electromagnetic pumping, no self-assembly is observed. In order to verify this atomic scale observation, we have built an artificial cell-like environment with nano-scale engineering and repeated spontaneous growth of tubulin protein to its complex with and without electromagnetic signal. We used 64 combinations of plant, animal and fungi tubulins and several doping molecules used as drug, and repeatedly observed that the long reported common frequency region where protein folds mechanically and its structures vibrate electromagnetically. Under pumping, the growth process exhibits a unique organized behavior unprecedented otherwise. Thus, "common frequency point" is proposed as a tool to regulate protein complex related diseases in the future. PMID:25466883

  7. Redox control of GPx catalytic activity through mediating self-assembly of Fmoc-phenylalanine selenide into switchable supramolecular architectures.

    PubMed

    Huang, Zupeng; Luo, Quan; Guan, Shuwen; Gao, Jianxiong; Wang, Yongguo; Zhang, Bo; Wang, Liang; Xu, Jiayun; Dong, Zeyuan; Liu, Junqiu

    2014-12-28

    Artificial enzymes capable of achieving tunable catalytic activity through stimuli control of enzymatic structure transition are of significance in biosensor and biomedicine research. Herein we report a novel smart glutathione peroxidise (GPx) mimic with modulatory catalytic activity based on redox-induced supramolecular self-assembly. First, an amphiphilic Fmoc-phenylalanine-based selenide was designed and synthesized, which can self-assemble into nanospheres (NSs) in aqueous solution. The NSs demonstrate extremely low GPx activity. Upon the oxidation of hydroperoxides (ROOH), the selenide can be quickly transformed into the selenoxide form. The change of the molecular structure induces complete morphology transition of the self-assemblies from NSs to nanotubes (NTs), resulting in great enhancement in the GPx catalytic activity. Under the reduction of GSH, the selenoxide can be further reversibly reduced back into the selenide; therefore the reversible switch between the NSs and NTs can be successfully accomplished. The relationship between the catalytic activity and enzymatic structure was also investigated. The dual response nature makes this mimic play roles of both a sensor and a GPx enzyme at the same time, which can auto-detect the signal of ROOH and then auto-change its activity to achieve quick or slow/no scavenging of ROOH. The dynamic balance of ROOH is vital in organisms, in which an appropriate amount of ROOH does benefit to the metabolism, whereas surplus ROOH can cause oxidative damage of the cell instead and this smart mimic is of remarkable significance. We expect that such a mimic can be developed into an effective antioxidant drug and provide a new platform for the construction of intelligent artificial enzymes with multiple desirable properties. PMID:25366375

  8. Excitons in a photosynthetic light-harvesting system: A combined molecular dynamics, quantum chemistry, and polaron model study

    Microsoft Academic Search

    Ana Damjanovic; Ioan Kosztin; Ulrich Kleinekathöfer; Klaus Schulten

    2002-01-01

    The dynamics of pigment-pigment and pigment-protein interactions in light-harvesting complexes is studied with an approach that combines molecular dynamics simulations with quantum chemistry calculations and a polaron model analysis. The molecular dynamics simulation of light-harvesting (LH) complexes was performed on an 87 055 atom system comprised of a LH-II complex of Rhodospirillum molischianum embedded in a lipid bilayer and surrounded

  9. The Ring Structure and Organization of Light Harvesting 2 Complexes in a Reconstituted Lipid Bilayer, Resolved by Atomic Force Microscopy

    Microsoft Academic Search

    Amalia Stamouli; Sidig Kafi; Dionne C. G. Klein; Tjerk H. Oosterkamp; Joost W. M. Frenken; Richard J. Cogdell; Thijs J. Aartsma

    2003-01-01

    The main function of the transmembrane light-harvesting complexes in photosynthetic organisms is the absorption of a light quantum and its subsequent rapid transfer to a reaction center where a charge separation occurs. A combination of freeze-thaw and dialysis methods were used to reconstitute the detergent-solubilized Light Harvesting 2 complex (LH2) of the purple bacterium Rhodopseudomonas acidophila strain 10050 into preformed

  10. Synthesis, properties and supramolecular self-assembly of novel n-type organic semiconductors

    NASA Astrophysics Data System (ADS)

    Verma, Nisha

    In the quest to develop low cost energy production, utilization of solar energy to generate electrical energy has gained wide attention in recent years. Artificial photosynthetic systems, mimicking natural photosynthesis, are emerging as a promising approach for efficient photoinduced electron transfer and, consequently, a powerful technique to afford low cost electrical energy. Hydrogen-bonded supramolecular systems hold great promise in this application due to the involvement of H-bonds in electronic communication. Therefore, such a system possessing multi-point, hydrogen-bonded groups have the potential to enhance the photo conversion efficiency significantly. Among the small organic molecule n-type semiconductors, perylene tetracarboxylic diimides (PDIs) and perylene tetracarboxylic dianhydrides (PTCDs) possess great potential due to the combination of a variety of desirable characteristics such as excellent thermal and photostability, high molar absorptivities and good electron accepting properties. Because of these attractive properties, PDIs are being heavily researched as materials in the burgeoning field of organic electronics such as organic photovoltaic, n-channel materials, organic thin film transistors, etc. PDIs have great potential due to their ability to form self-assembled complex architectures via their high propensity for pi-pi stacking which can be coupled with other intermolecular interactions, such as hydrogen bonding, to form ordered functional systems. This dissertation focuses on the convenient synthesis and separation of 1,6- and 1,7-regioisomers of PDIs and PTCDs, the comparison of their anonymous properties, the effect of multi-point hydrogen bonding motifs on the self-assembly of PDIs, and the electron transport properties of novel derivatives of PTCDs.

  11. Self-Assembly of Channel Type ?-CD Dimers Induced by Dodecane

    PubMed Central

    Zhou, Chengcheng; Cheng, Xinhao; Zhao, Qiang; Yan, Yun; Wang, Jide; Huang, Jianbin

    2014-01-01

    Cyclodextrins (CDs) can hardly self-assemble into well-defined structures. Here we report if they preassemble into channel type dimers assisted by dodecane, well-defined vesicles and bricks can be formed. Unlike the traditional self-assembly of amphiphilic molecules driven by hydrophobic effect, the self-assembly of the channel type dodecane@2?-CD supramolecular building block is predoninantly driven by hydrogen-bonds. More water molecules are found in the lyophilized vesicles than in the bricks, suggesting water molecules play an important role in the self-assembly of the channel-type dimers of ?-CD. The amount of structural water in the self-assembly is closely related to the curvature of the final self-assembled structures. Our work reveals that the channel-type dimer of ?-CD may represent a new sort of building block for advanced structures. PMID:25532046

  12. A Programmable Transducer Self-Assembled from DNA

    PubMed Central

    Chakraborty, Banani; Jonoska, Natasha; Seeman, Nadrian C.

    2012-01-01

    A transducer consists of an input/output alphabet, a finite set of states, and a transition function. From an input symbol applied to a given state, the transition function determines the next state, and an output symbol. Using DNA, we have constructed a transducer that divides a number by 3. The input consists of a series of individually addressable 2-state DNA nanomechanical devices that control the orientations of a group of flat 6-helix DNA motifs; these motifs have edge domains tailed in sticky ends corresponding to the numbers 0 and 1. Three-domain DNA molecules (TX tiles) act as computational tiles that correspond to the transitions that the transducer can undergo. The output domain of these TX tiles contains sticky ends that also correspond to 0 or 1. Two different DNA tiles can chelate these output domains: A 5 nm gold nanoparticle is attached to the chelating tile that binds to 0-domains and a 10 nm gold nanoparticle is attached to the chelating tile that binds to 1-domains. The answer to the division is represented by the series of gold nanoparticles, which can be interpreted as a binary number. The answers of the computation are read out by examination of the transducer complexes under a transmission electron microscope. The start or end points of the output sequence can be indicated by the presence of a 15 nm gold nanoparticle. This work demonstrates two previously unreported features integrated in a single framework: [1] a system that combines DNA algorithmic self-assembly with DNA nanomechanical devices that control that input, and [2] the arrangement of non-DNA species, here metallic nanoparticles, through DNA algorithmic self-assembly. The nanomechanical devices are controlled by single-stranded DNA strands, allowing multiple input sequences to be applied to the rest of the system, thus guiding the algorithmic self-assembly to a variety of outputs. PMID:23139854

  13. A Programmable Transducer Self-Assembled from DNA.

    PubMed

    Chakraborty, Banani; Jonoska, Natasha; Seeman, Nadrian C

    2012-01-01

    A transducer consists of an input/output alphabet, a finite set of states, and a transition function. From an input symbol applied to a given state, the transition function determines the next state, and an output symbol. Using DNA, we have constructed a transducer that divides a number by 3. The input consists of a series of individually addressable 2-state DNA nanomechanical devices that control the orientations of a group of flat 6-helix DNA motifs; these motifs have edge domains tailed in sticky ends corresponding to the numbers 0 and 1. Three-domain DNA molecules (TX tiles) act as computational tiles that correspond to the transitions that the transducer can undergo. The output domain of these TX tiles contains sticky ends that also correspond to 0 or 1. Two different DNA tiles can chelate these output domains: A 5 nm gold nanoparticle is attached to the chelating tile that binds to 0-domains and a 10 nm gold nanoparticle is attached to the chelating tile that binds to 1-domains. The answer to the division is represented by the series of gold nanoparticles, which can be interpreted as a binary number. The answers of the computation are read out by examination of the transducer complexes under a transmission electron microscope. The start or end points of the output sequence can be indicated by the presence of a 15 nm gold nanoparticle. This work demonstrates two previously unreported features integrated in a single framework: [1] a system that combines DNA algorithmic self-assembly with DNA nanomechanical devices that control that input, and [2] the arrangement of non-DNA species, here metallic nanoparticles, through DNA algorithmic self-assembly. The nanomechanical devices are controlled by single-stranded DNA strands, allowing multiple input sequences to be applied to the rest of the system, thus guiding the algorithmic self-assembly to a variety of outputs. PMID:23139854

  14. Self-assembly of amorphous biophotonic nanostructures by phase separation

    SciTech Connect

    Dufresne, Eric R.; Noh, Heeso; Saranathan, Vinodkumar; Mochrie, Simon G.J.; Cao, Hui; Prum, Richard O.; (Yale)

    2009-04-23

    Some of the most vivid colors in the animal kingdom are created not by pigments, but by wavelength-selective scattering of light from nanostructures. Here we investigate quasi-ordered nanostructures of avian feather barbs which produce vivid non-iridescent colors. These {beta}-keratin and air nanostructures are found in two basic morphologies: tortuous channels and amorphous packings of spheres. Each class of nanostructure is isotropic and has a pronounced characteristic length scale of variation in composition. These local structural correlations lead to strong backscattering over a narrow range of optical frequencies and little variation with angle of incidence. Such optical properties play important roles in social and sexual communication. To be effective, birds need to precisely control the development of these nanoscale structures, yet little is known about how they grow. We hypothesize that multiple lineages of birds have convergently evolved to exploit phase separation and kinetic arrest to self-assemble spongy color-producing nanostructures in feather barbs. Observed avian nanostructures are strikingly similar to those self-assembled during the phase separation of fluid mixtures; the channel and sphere morphologies are characteristic of phase separation by spinodal decomposition and nucleation and growth, respectively. These unstable structures are locked-in by the kinetic arrest of the {beta}-keratin matrix, likely through the entanglement or cross-linking of supermolecular {beta}-keratin fibers. Using the power of self-assembly, birds can robustly realize a diverse range of nanoscopic morphologies with relatively small physical and chemical changes during feather development.

  15. Customizing mesoscale self-assembly with 3D printing

    E-print Network

    M. Poty; G. Lumay; N. Vandewalle

    2013-10-17

    Self-assembly due to capillary forces is a common method for generating 2D mesoscale structures from identical floating particles at the liquid-air interface. Designing building blocks to obtain a desired mesoscopic structure is a scientific challenge. We show herein that it is possible to shape the particles with a low cost 3D printer, for composing specific mesoscopic structures. Our method is based on the creation of capillary multipoles inducing either attractive or repulsive forces. Since capillary interactions can be downscaled, our method opens new ways to low cost microfabrication.

  16. Self-assembly of free-standing RNA membranes

    NASA Astrophysics Data System (ADS)

    Han, Daehoon; Park, Yongkuk; Kim, Hyejin; Lee, Jong Bum

    2014-07-01

    RNA has emerged as a promising material for nanostructure and microstructure engineering. Although rare, some macroscopic RNA structures have also been constructed using lipid or polymer materials. Here, we report the first example of an enzymatically generated RNA membrane. This robust and free-standing RNA membrane has a macroscopic structure and is generated without any polymer support or complexation. Our RNA membrane is fabricated following two sequential processes, complementary rolling circle transcription and evaporation-induced self-assembly, and its structural and functional properties are rationally controlled by adjusting RNA base pairing. In this study, three types of RNA membranes are fabricated and are used to demonstrate potential applications.

  17. Electrostatic Self-assembly : A New Route Towards Nanostructures

    E-print Network

    J. -F. Berret; P. Herve; M. Morvan; K. Yokota; M. Destarac; J. Oberdisse; I. Grillo; R. Schweins

    2005-01-05

    During the last 3 years, our group has investigated extensively the complexation mechanism between neutral-polyelectrolyte block copolymers with oppositely charged species. These species are surfactant micelles, multivalent counterions and inorganic nanoparticles. In the three cases, we have established the thermodynamical phase diagram of these systems, and found broad regions where supramolecular aggregates spontaneously form via electrostatic self-assembly. From earlier works, it was suspected that these mixed colloids exhibit a core-shell structure. However, their inner structure was unveiled by us only recently, using a combination of light, neutron and x-ray scattering experiments.

  18. Optoelectronic switching of addressable self-assembled monolayer molecular junctions

    NASA Astrophysics Data System (ADS)

    Li, J. C.

    2009-04-01

    This Letter reports on the observation of optoelectronic switching in addressable molecular crossbar junctions fabricated using stamp-printing method. The active medium is a self-assembled monolayer softly sandwiched between gold electrodes. The junctions are investigated through current-voltage measurements at varied temperature, which show reversible optoelectronic switching with on/off ratio of three orders of magnitude at 95 K. The switching is independent of both optical wavelength and molecular structure, while it strongly depends on the temperature. It is shown that the distinct binding nature of the molecule/electrode interfaces play a dominant role in the switching performance.

  19. Electron transfer into self-assembling monolayers on gold electrodes

    Microsoft Academic Search

    Bunding Lee

    1990-01-01

    Electron transfer through a nonconjugated hydrocarbon film was studied. 1-Methyl-1â²-(10-(octadecylthio)decyl)-4,4â²-bipyridinium dibromide, 1-(7-(octadecylthio)heptyl)-1â²-propyl-4,4â²-bipyridinium dibromide, and 1-hexyl-1â²-(5-(octadecylthio)pentyl)-4,4â²-bipyridinium dibromide were synthesized and were separately self-assembled with octadecyl mercaptan onto Au electrodes. The sulfide attached to the gold, and the hydrocarbon chains oriented such that the resulting monolayer films had the electroactive group fixed a distance of 5, 7, or 10 CHâ groups from

  20. Model for dynamic self-assembled magnetic surface structures.

    SciTech Connect

    Belkin, M.; Glatz, A.; Snezhko, A.; Aranson, I. S.; Materials Science Division; Northwestern Univ.

    2010-07-07

    We propose a first-principles model for the dynamic self-assembly of magnetic structures at a water-air interface reported in earlier experiments. The model is based on the Navier-Stokes equation for liquids in shallow water approximation coupled to Newton equations for interacting magnetic particles suspended at a water-air interface. The model reproduces most of the observed phenomenology, including spontaneous formation of magnetic snakelike structures, generation of large-scale vortex flows, complex ferromagnetic-antiferromagnetic ordering of the snake, and self-propulsion of bead-snake hybrids.

  1. Guiding 3-D Self Assembly of Nanostructures by DNA Hybridization

    NASA Astrophysics Data System (ADS)

    Rogers, Phillip; Roberts, Brad; Pine, David; Michel, Eric; Schwartz, Peter

    2005-03-01

    The directed three dimensional self-assembly of microstructures and nanostructures through the selective hybridization of DNA is the focus of great interest toward the fabrication of new materials. Single stranded DNA is covalently attached to polystyrene latex microspheres and functions as a ``smart Velcro'' by only bonding to another strand of DNA of complementary sequence. The attached DNA increases the charge stabilization of the microspheres and allows controllable aggregation of microspheres by hybridization of complementary DNA sequences. The process is perfectly selective and reversible by heating, with a characteristic ``aggregate dissociation temperature'' that is dependent on salt concentration, and the evolution of aggregate dissociation with temperature is observed with optical microscopy.

  2. Self-assembled carboxylate complexes of zinc, nickel and copper

    Microsoft Academic Search

    Kaustavmoni Deka; Nilotpal Barooah; Rupam Jyoti Sarma; Jubaraj B. Baruah

    2007-01-01

    A metallo-organic hybrid acid namely tetra-aquo bis-4-carboxy-N-phthaloylglycinato zinc(II) dihydrate is prepared and characterised. In this complex the hydrogen bonding by free carboxylic acid group and pi pi interactions between the rings in crystal lattice contributes to the formation of self-assembled structure. A monomeric nickel complex from 2-carbomethoxy benzoic acid (L2H) and pyridine [Ni(L2)(py)3(H2O)2]L2 is prepared (where py = pyridine). This

  3. Self-assembled carboxylate complexes of zinc, nickel and copper

    Microsoft Academic Search

    Kaustavmoni Deka; Nilotpal Barooah; Rupam Jyoti Sarma; Jubaraj B. Baruah

    2007-01-01

    A metallo-organic hybrid acid namely tetra-aquo bis-4-carboxy-N-phthaloylglycinato zinc(II) dihydrate is prepared and characterised. In this complex the hydrogen bonding by free carboxylic acid group and ?–? interactions between the rings in crystal lattice contributes to the formation of self-assembled structure. A monomeric nickel complex from 2-carbomethoxy benzoic acid (L2H) and pyridine [Ni(L2)(py)3(H2O)2]L2 is prepared (where py=pyridine). This complex has ionic

  4. Computing with Nanowires: A Self Assembled Neuromorphic Architecture

    Microsoft Academic Search

    Supriyo Bandyopadhyay; Koray Karahaliloglu; Sridhar Patibandla

    \\u000a A two-dimensional array of nanowires, embedded in a semi-insulating medium, can elicit powerful computational and signal processing\\u000a activity if the nanowires exhibit an N-type non-linearity in their current versus voltage characteristics. Such a system is\\u000a relatively easy to self assemble using chemical routes and we have synthesized such systems using simple electrochemistry.\\u000a The measured current–voltage characteristics of the nanowires exhibit

  5. Visible Fluorescence Emission from Self-assembled Porphyrin Nanotubes

    E-print Network

    Gupta, Jyotsana

    2009-01-01

    Porphyrin nanotubes (PNTs) are prepared by self-assembly using meso-tetrakis (4-sulfonatophenyl) porphyrin and Fe(III) meso-Tetra (N-Methyl-4-Pyridyl) porphyrin in water as starting materials. Long tubes of about one micron diameter are formed with bunches of smaller tubes attached to it, as judged from the analysis of HRTEM images. The PNTs formed by this method are found to exhibit good visible emission at 669 nm on excitation at 432 nm whereas both parent porphyrin monomers do not exhibit any fluorescence. This result highlights the scope of PNTs as functional components in the design of biofriendly devices in medical as well as nanophotonics applications.

  6. Self-assembly and reconfigurability of shape-shifting particles.

    PubMed

    Nguyen, Trung Dac; Jankowski, Eric; Glotzer, Sharon C

    2011-11-22

    Reconfigurability of two-dimensional colloidal crystal structures assembled by anisometric particles capable of changing their shape were studied by molecular dynamics computer simulation. We show that when particles change shape on cue, the assembled structures reconfigure into different ordered structures, structures with improved order, or more densely packed disordered structures, on faster time scales than can be achieved via self-assembly from an initially disordered arrangement. These results suggest that reconfigurable building blocks can be used to assemble reconfigurable materials, as well as to assemble structures not possible otherwise, and that shape shifting could be a promising mechanism to engineer assembly pathways to ordered and disordered structures. PMID:21950837

  7. Self-assembling peptide amphiphile nanostructures for cancer therapy

    NASA Astrophysics Data System (ADS)

    Soukasene, Stephen

    The application of nanotechnology to cancer therapy shows great promise for reducing the burden of the disease. By virtue of their size, nanoscale objects preferentially accumulate in tumor tissue through an enhanced permeability and retention (EPR) effect. However, to fully overcome the issues that limit current cancer treatments, viable nanostructures must also impart multifunctionality and be fully compatible with their biological surrounds. The self-assembling peptide amphiphile (PA) materials studied extensively in the Stupp Research Group form very biocompatible high aspect ratio nanostructures that meet these criteria. This thesis investigates the development of PA nanostructures designed to treat cancer. We first look to use the PA as a drug delivery vehicle by entrapping a small hydrophobic anti-cancer drug, camptothecin, in the core of the nanostructures. Using a solvent evaporation technique to load the drug into the PA nanofibers, we are able to improve the aqueous solubility of the molecule by nearly 30-fold. TEM and AFM studies show that entrapment of drug molecules does not disrupt the self-assembled morphology of the nanofiber. In vitro and in vivo studies are also conducted to demonstrate the bioactivity of the drug after its entrapment. As a potential platform for novel therapeutics, we next develop techniques for using light irradiation to trigger self-assembly inside the confined space of liposomes. We encapsulate PA monomers that assemble under acidic conditions along with a photoacid generator inside liposomes. Upon exposure to 254 nm light, the PA monomers self assemble inside the liposome to form nanostructures, which we observe through a quick freeze/deep etch technique that allows us to look inside the liposomes by SEM and TEM. Last of all, the development and discovery of epitopes for targeting PA nanostructures to tumors are explored. Using phage display technology we generate two groups of peptide sequences, one of which can potentially target tumor blood vessel formation, while the other is directed toward the ErbB2 receptor, which is over-expressed in certain aggressive breast cancers. Two peptide sequences from the literature that target breast cancer are also incorporated into PA molecules and we assess their biological affinity in vitro and in vivo.

  8. Rapid Self-Assembly of Uranyl Polyhedra into Crown Clusters

    SciTech Connect

    Sigmon, Ginger E. [Univ. of Notre Dame, IN (United States). Dept. of Civil Engineering and Geological Sciences; Burns, Peter C. [Univ. of Notre Dame, IN (United States). Dept. of Civil Engineering and Geological Sciences

    2011-06-22

    Clusters built from 32 uranyl peroxide polyhedra self-assemble and crystallize within 15 min after combining uranyl nitrate, ammonium hydroxide, and hydrogen peroxide in aqueous solution under ambient conditions. These novel crown-shaped clusters are remarkable in that they form so quickly, have extraordinarily low aqueous solubility, form with at least two distinct peroxide to hydroxyl ratios, and form in very high yield. The clusters, which have outer diameters of 23 Å, topologically consist of eight pentagons and four hexagons. Their rapid formation and low solubility in aqueous systems may be useful properties at various stages in an advanced nuclear energy system.

  9. Folding and bending of self-assembled nanoparticle membranes

    NASA Astrophysics Data System (ADS)

    Wang, Yifan; Liao, Jianhui; McBride, Sean; Efrati, Efi; Lin, Xiao-Min; Jaeger, Heinrich

    2015-03-01

    We demonstrate that self-assembled nanoparticle monolayers can be folded into 3 dimensional hollow structures - nanoparticle scrolls, by utilizing their internal strain gradient. Using an Atomic Force Microscope (AFM), indentation measurements were made on these nanoparticle scrolls, and the bending modulus of the nanoparticle membrane is obtained for the first time. The resulting bending modulus is two orders of magnitude larger than that predicted by classical continuum elastic theory, we show this can be explained by a micropolar theory as the material thickness approaches single nanoparticle size.

  10. Tunable resonant optical microcavities by self-assembled templating.

    PubMed

    Vijaya Prakash, G; Besombes, L; Kelf, T; Baumberg, Jeremy J; Bartlett, P N; Abdelsalam, M E

    2004-07-01

    Micrometer-scale optical cavities are produced by a combination of template sphere self-assembly and electrochemical growth. Transmission measurements of the tunable microcavities show sharp resonant modes with Q factors of >300 and 25-fold local enhancement of light intensity. The presence of transverse optical modes confirms the lateral confinement of photons. Calculations show that submicrometer mode volumes are feasible. The small mode volumes of these microcavities promise to lead to a wide range of applications. in microlasers, atom optics, quantum information, biophotonics, and single-molecule detection. PMID:15259726

  11. Tunable resonant optical microcavities by self-assembled templating

    NASA Astrophysics Data System (ADS)

    Prakash, G. Vijaya; Besombes, L.; Kelf, T.; Baumberg, Jeremy J.; Bartlett, P. N.; Abdelsalam, M. E.

    2004-07-01

    Micrometer-scale optical cavities are produced by a combination of template sphere self-assembly and electrochemical growth. Transmission measurements of the tunable microcavities show sharp resonant modes with Q factors of >300 and 25-fold local enhancement of light intensity. The presence of transverse optical modes confirms the lateral confinement of photons. Calculations show that submicrometer mode volumes are feasible. The small mode volumes of these microcavities promise to lead to a wide range of applications in microlasers, atom optics, quantum information, biophotonics, and single-molecule detection.

  12. Unifying Interfacial Self-Assembly and Surface Freezing

    SciTech Connect

    B Ocko; H Hlaing; P Jepsen; S Kewalramani; A Tkachenko; D Pontoni; H Reichert; M Deutsch

    2011-12-31

    X-ray investigations reveal that the monolayers formed at the bulk alkanol-sapphire interface are densely packed with the surface-normal molecules hydrogen bound to the sapphire. About 30-35 C above the bulk, these monolayers both melt reversibly and partially desorb. This system exhibits balanced intermolecular and molecule-substrate interactions which are intermediate between self-assembled and surface-frozen monolayers, each dominated by one interaction. The phase behavior is rationalized within a thermodynamic model comprising interfacial interactions, elasticity, and entropic effects. Separating the substrate from the melt leaves the monolayer structurally intact.

  13. Unifying Interfacial Self-Assembly and Surface Freezing

    SciTech Connect

    Ocko, B.M.; Hlaing, H.; Jepsen, P.N.; Kewalramani, S.; Tkachenko, A.; Pontoni, D.; Reichert, H.; Deutsch, M.

    2011-03-30

    X-ray investigations reveal that the monolayers formed at the bulk alkanol-sapphire interface are densely packed with the surface-normal molecules hydrogen bound to the sapphire. About 30-35 C above the bulk, these monolayers both melt reversibly and partially desorb. This system exhibits balanced intermolecular and molecule-substrate interactions which are intermediate between self-assembled and surface-frozen monolayers, each dominated by one interaction. The phase behavior is rationalized within a thermodynamic model comprising interfacial interactions, elasticity, and entropic effects. Separating the substrate from the melt leaves the monolayer structurally intact.

  14. Design, Simulation, and Experimental Demonstration of Self-assembled DNA Nanostructures and Motors

    Microsoft Academic Search

    John H. Reif; Thomas H. Labean; Sudheer Sahu; Hao Yan; Peng Yin

    2004-01-01

    Self-assembly is the spontaneous self-ordering of substructures into superstructures driven by the selective affinity of the substructures. DNA pro- vides a molecular scale material for programmable self-assembly, using the selective affinity of pairs of DNA strands to form DNA nanostructures. DNA self-assembly is the most advanced and versatile system that has been ex- perimentally demonstrated for programmable construction of patterned

  15. Real time monitoring of superparamagnetic nanoparticle self-assembly on surfaces of magnetic recording media

    SciTech Connect

    Ye, L.; Pearson, T.; Crawford, T. M., E-mail: crawftm@mailbox.sc.edu [Department of Physics and Astronomy, University of South Carolina, 712 Main Street, Columbia, South Carolina 29208 (United States); Qi, B.; Cordeau, Y.; Mefford, O. T. [Department of Materials Science and Engineering, Clemson University, 161 Sirrine Hall, Clemson, South Carolina 29634 (United States); Center for Optical Materials Science and Engineering Technologies (COMSET), 91 Technology Dr., Anderson, South Carolina 29625 (United States)

    2014-05-07

    Nanoparticle self-assembly dynamics are monitored in real-time by detecting optical diffraction from an all-nanoparticle grating as it self-assembles on a grating pattern recorded on a magnetic medium. The diffraction efficiency strongly depends on concentration, pH, and colloidal stability of nanoparticle suspensions, demonstrating the nanoparticle self-assembly process is highly tunable. This metrology could provide an alternative for detecting nanoparticle properties such as colloidal stability.

  16. Self-Assembly of Nanostructured Electronic Devices (454th Brookhaven Lecture)

    Microsoft Academic Search

    Charles

    2009-01-01

    Given suitable atmospheric conditions, water vapor from the air will crystallize into beautiful structures: snowflakes. Nature provides many other examples of spontaneous organization of materials into regular patterns, which is a process known as self-assembly. Since self-assembly works at all levels, it can be a useful tool for organizing materials on the nanometer scale. In particular, self-assembly provides a precise

  17. Polymer MEMS fabrication process for self-assembled millimeter-wave on-chip antennas

    Microsoft Academic Search

    S.-W. Lee; M. Parameswaran

    2011-01-01

    A novel micro-electro-mechanical systems (MEMS) fabrication process for self-assembled antennas has been characterized. Self-assembled vertical monopole antennas were previously reported [1]. The vertical on-chip antennas provide higher efficiency over conventional planar on-chip antennas. However, the metallization step of the antennas was performed after the release and self-assembly of the devices resulting in minimal deposition of metal on the backside of

  18. Templated hierarchical self-assembly of poly(p-aryltriazole) foldamers.

    PubMed

    Pfukwa, Rueben; Kouwer, Paul H J; Rowan, Alan E; Klumperman, Bert

    2013-10-11

    A biomimetic approach has been used for the templated self-assembly of a helical poly(para-aryltriazole) foldamer. The solvophobic folding process yields helices that further self-assemble into long nanotubes (see picture; scale bar: 100?nm). Constructs of controlled length and chirality can be generated by applying a poly(?-benzyl-l-glutamate) scaffold at the appropriate assembly conditions, mimicking tobacco mosaic virus self-assembly. PMID:24038888

  19. Self-assembling adhesion promoters for corrosion resistant metal polymer interfaces

    Microsoft Academic Search

    Iris Maege; Evelin Jaehne; Axel Henke; Hans-Juergen P Adler; Christian Bram; Christian Jung; Martin Stratmann

    1997-01-01

    The self-assembly process has been investigated for the replacement of the present chromating procedure on reactive metals like aluminium and to improve the lacquer adhesion and corrosion inhibition. It will be shown, that self-assembled layers can affect adhesion and corrosion inhibition on aluminium and its alloys. For self-assembly molecules (SAMs) substances are required which are able to react spontaneously on

  20. Vertical segregation in the self-assembly of nanoparticles at the liquid/air interface

    NASA Astrophysics Data System (ADS)

    LiuYanming Liu; Yang Liu Equally Contributed To This Paper., Yanming; Liu, Yang; Tao, Peng; Shang, Wen; Song, Chengyi; Deng, Tao

    2014-11-01

    Vertical segregation was induced by the size-dependent charge neutralization during the one-step interfacial self-assembly of colloidal gold nanoparticles with bimodal size distribution. This self-assembly approach also can assemble particles with tunable compositions into layered films.Vertical segregation was induced by the size-dependent charge neutralization during the one-step interfacial self-assembly of colloidal gold nanoparticles with bimodal size distribution. This self-assembly approach also can assemble particles with tunable compositions into layered films. Electronic supplementary information (ESI) available: Experimental procedures and Fig. S1-S13. See DOI: 10.1039/c4nr04779f

  1. Developing novel polymer architectures for applications In magnetic resonance imaging and self-assembly

    E-print Network

    McCombs, Jessica R. (Jessica Rose)

    2013-01-01

    Macromolecular scaffolds for drug delivery, self-assembly, and imaging applications have attracted significant attention over the last several decades. As polymerization techniques become more sophisticated, it becomes ...

  2. Self-assembly of nanoparticles into nanowires under laser exposure in liquids

    NASA Astrophysics Data System (ADS)

    Serkov, A. A.; Barmina, E. V.; Kuzmin, P. G.; Shafeev, G. A.

    2015-03-01

    Experimental results on the process of self-assembly of Au nanoparticles under their exposure to picosecond laser radiation in water are presented. Self-assembly of Au NPs into nanowires occurs under laser ablation of a bulk Au target, which is cathodically biased with respect to a Pt anode. Similar process is observed in excess of free electrons in solution due to presence of beta-active ions, e.g., Tritium. Self-assembly of Au NPs into nanowires also occurs under laser exposure of their dense colloidal solution to picosecond laser radiation and proceeds in an avalanche-like way. Possible mechanisms of self-assembly are discussed.

  3. Amphiphilic Janus gold nanoparticles prepared by interface-directed self-assembly: synthesis and self-assembly.

    PubMed

    Liu, Guannan; Tian, Jia; Zhang, Xu; Zhao, Hanying

    2014-09-01

    Materials with Janus structures are attractive for wide applications in materials science. Although extensive efforts in the synthesis of Janus particles have been reported, the synthesis of sub-10?nm Janus nanoparticles is still challenging. Herein, the synthesis of Janus gold nanoparticles (AuNPs) based on interface-directed self-assembly is reported. Polystyrene (PS) colloidal particles with AuNPs on the surface were prepared by interface-directed self-assembly, and the colloidal particles were used as templates for the synthesis of Janus AuNPs. To prepare colloidal particles, thiol-terminated polystyrene (PS-SH) was dissolved in toluene and citrate-stabilized AuNPs were dispersed in aqueous solution. Upon mixing the two solutions, PS-SH chains were grafted to the surface of AuNPs and amphiphilic AuNPs were formed at the liquid-liquid interface. PS colloidal particles decorated with AuNPs on the surfaces were prepared by adding the emulsion to excess methanol. On the surface, AuNPs were partially embedded in the colloidal particles. The outer regions of the AuNPs were exposed to the solution and were functionalized through the grafting of atom-transfer radical polymerization (ATRP) initiator. Poly[2-(dimethamino)ethyl methacrylate] (PDMAEMA) on AuNPs were prepared by surface-initiated ATRP. After centrifugation and dissolving the colloidal particles in tetrahydrofuran (THF), Janus AuNPs with PS and PDMAEMA on two hemispheres were obtained. In acidic pH, Janus AuNPs are amphiphilic and are able to emulsify oil droplets in water; in basic pH, the Janus AuNPs are hydrophobic. In mixtures of THF/methanol at a volume ratio of 1:5, the Janus AuNPs self-assemble into bilayer structures with collapsed PS in the interiors and solvated PDMAEMA at the exteriors of the structures. PMID:25044923

  4. Engineering Protocells: Prospects for Self-Assembly and Nanoscale Production-Lines

    PubMed Central

    Miller, David M.; Gulbis, Jacqueline M.

    2015-01-01

    The increasing ease of producing nucleic acids and proteins to specification offers potential for design and fabrication of artificial synthetic “organisms” with a myriad of possible capabilities. The prospects for these synthetic organisms are significant, with potential applications in diverse fields including synthesis of pharmaceuticals, sources of renewable fuel and environmental cleanup. Until now, artificial cell technology has been largely restricted to the modification and metabolic engineering of living unicellular organisms. This review discusses emerging possibilities for developing synthetic protocell “machines” assembled entirely from individual biological components. We describe a host of recent technological advances that could potentially be harnessed in design and construction of synthetic protocells, some of which have already been utilized toward these ends. More elaborate designs include options for building self-assembling machines by incorporating cellular transport and assembly machinery. We also discuss production in miniature, using microfluidic production lines. While there are still many unknowns in the design, engineering and optimization of protocells, current technologies are now tantalizingly close to the capabilities required to build the first prototype protocells with potential real-world applications. PMID:25815781

  5. Ion channel models based on self-assembling cyclic peptide nanotubes.

    PubMed

    Montenegro, Javier; Ghadiri, M Reza; Granja, Juan R

    2013-12-17

    The lipid bilayer membranes are Nature's dynamic structural motifs that individualize cells and keep ions, proteins, biopolymers and metabolites confined in the appropriate location. The compartmentalization and isolation of these molecules from the external media facilitate the sophisticated functions and connections between the different biological processes accomplished by living organisms. However, cells require assistance from minimal energy shortcuts for the transport of molecules across membranes so that they can interact with the exterior and regulate their internal environments. Ion channels and pores stand out from all other possible transport mechanisms due to their high selectivity and efficiency in discriminating and transporting ions or molecules across membrane barriers. Nevertheless, the complexity of these smart "membrane holes" has driven researchers to develop simpler artificial structures with comparable performance to the natural systems. As a broad range of supramolecular interactions have emerged as efficient tools for the rational design and preparation of stable 3D superstructures, these results have stimulated the creativity of chemists to design synthetic mimics of natural active macromolecules and even to develop artificial structures with functions and properties. In this Account, we highlight results from our laboratories on the construction of artificial ion channel models that exploit the self-assembly of conformationally flat cyclic peptides (CPs) into supramolecular nanotubes. Because of the straightforward synthesis of the cyclic peptide monomers and the complete control over the internal diameter and external surface properties of the resulting hollow tubular suprastructure, CPs are the optimal candidates for the fabrication of ion channels. The ion channel activity and selective transport of small molecules by these structures are examples of the great potential that cyclic peptide nanotubes show for the construction of functional artificial transmembrane transporters. Our experience to date suggests that the next steps for achieving conceptual devices with better performance and selectivity will derive from the topological control over cyclic peptide assembly and the functionalization of the lumen. PMID:23898935

  6. Kinetically driven self assembly of highly ordered nanoparticle monolayers.

    PubMed

    Bigioni, Terry P; Lin, Xiao-Min; Nguyen, Toan T; Corwin, Eric I; Witten, Thomas A; Jaeger, Heinrich M

    2006-04-01

    When a drop of a colloidal solution of nanoparticles dries on a surface, it leaves behind coffee-stain-like rings of material with lace-like patterns or clumps of particles in the interior. These non-uniform mass distributions are manifestations of far-from-equilibrium effects, such as fluid flows and solvent fluctuations during late-stage drying. However, recently a strikingly different drying regime promising highly uniform, long-range-ordered nanocrystal monolayers has been found. Here we make direct, real-time and real-space observations of nanocrystal self-assembly to reveal the mechanism. We show how the morphology of drop-deposited nanoparticle films is controlled by evaporation kinetics and particle interactions with the liquid-air interface. In the presence of an attractive particle-interface interaction, rapid early-stage evaporation dynamically produces a two-dimensional solution of nanoparticles at the liquid-air interface, from which nanoparticle islands nucleate and grow. This self-assembly mechanism produces monolayers with exceptional long-range ordering that are compact over macroscopic areas, despite the far-from-equilibrium evaporation process. This new drop-drying regime is simple, robust and scalable, is insensitive to the substrate material and topography, and has a strong preference for forming monolayer films. As such, it stands out as an excellent candidate for the fabrication of technologically important ultra thin film materials for sensors, optical devices and magnetic storage media. PMID:16547519

  7. Aerosol-Assisted Self-Assembly of Mesostructured Spherical Nanoparticles

    SciTech Connect

    Brinker, C.J.; Fan,; H.; Lu, Y.; Rieker, T.; Stump, A.; Ward, T.L.

    1999-03-23

    Nanostructured particles exhibiting well-defined pore sizes and pore connectivities (1-, 2-, or 3-dimensional) are of interest for catalysis, chromatography, controlled release, low dielectric constant fillers, and custom-designed pigments and optical hosts. During the last several years considerable progress has been made on controlling the macroscopic forms of mesoporous silicas prepared by surfactant and block copolymer liquid crystalline templating procedures. Typically interfacial phenomena are used to control the macroscopic form (particles, fibers, or films), while self-assembly of amphiphilic surfactants or polymers is used to control the mesostructure. To date, although a variety of spherical or nearly-spherical particles have been prepared, their extent of order is limited as is the range of attainable mesostructures. They report a rapid, aerosol process that results in solid, completely ordered spherical particles with stable hexagonal, cubic, or vesicular mesostructures. The process relies on evaporation-induced interfacial self-assembly (EISA) confined to a spherical aerosol droplet. The process is simple and generalizable to a variety of materials combinations. Additionally, it can be modified to provide the first aerosol route to the formation of ordered mesostructured films.

  8. Packing and self-assembly of truncated triangular bipyramids.

    PubMed

    Haji-Akbari, Amir; Chen, Elizabeth R; Engel, Michael; Glotzer, Sharon C

    2013-07-01

    Motivated by breakthroughs in the synthesis of faceted nano- and colloidal particles, as well as theoretical and computational studies of their packings, we investigate a family of truncated triangular bipyramids. We report dense periodic packings with small unit cells that were obtained via numerical and analytical optimization. The maximal packing fraction ?(max) changes continuously with the truncation parameter t. Eight distinct packings are identified based on discontinuities in the first and second derivatives of ?(max)(t). These packings differ in the number of particles in the fundamental domain (unit cell) and the type of contacts between the particles. In particular, we report two packings with four particles in the unit cell for which both ?(max)(t) and ?(max)'(t) are continuous and the discontinuity occurs in the second derivative only. In the self-assembly simulations that we perform for larger boxes with 2048 particles, only one out of eight packings is found to assemble. In addition, the degenerate quasicrystal reported previously for triangular bipyramids without truncation [Haji-Akbari et al., Phys. Rev. Lett. 107, 215702 (2011)] assembles for truncations as high as 0.45. The self-assembly propensities for the structures formed in the thermodynamic limit are explained using the isoperimetric quotient of the particles and the coordination number in the disordered fluid and in the assembled structure. PMID:23944434

  9. Facile self-assembly and stabilization of metal oxide nanoparticles.

    PubMed

    Charbonneau, Cecile; Holliman, Peter J; Davies, Matthew L; Watson, Trystan M; Worsley, David A

    2015-03-15

    This paper describes a facile method of self-assembling different metal oxide nanoparticles into nanostructured materials via di-carboxylate linkers (oxalic acid) using TiO2 as an example. In this method, the di-carboxylate linkers react with surface hydroxyls on metal oxide nanoparticles forming covalent, ester-like bonds, which enable the binding of two metal oxide particles, one at either end of the linker and facilitates efficient self-assembly of one group of metal oxide nanoparticles homogeneously distributed onto the surface of another group. The oxalate linkers can then be removed by thermal decomposition. This approach is shown to be effective using differently-sized TiO2 nanoparticles, namely in-house synthesized 3-5nm anatase nanocrystals and Degussa P25 titania particles (mean 21nm particle size). Our data show that the application of a high temperature heat treatment (450°C for 30min), conventionally applied to achieve a stable porous structure by thermal decomposition of the linker molecules and by inducing inter-particle necking, damages the surface area of the nanostructured material. However, here we show that sintering at 300°C for 30min or by flash near infrared radiation sintering for 12s efficiently decomposes the oxalate linkers and stabilizes the nanostructure of the material whilst maintaining its high surface area. PMID:25525978

  10. Self-assembly of Giant Molecular Shape Amphiphiles in Solution

    NASA Astrophysics Data System (ADS)

    Wang, Rong; Ma, Shiying

    2015-03-01

    The self-assembly of giant molecular shape amphiphiles consisting of a hydrophilic head and one or more hydrophobic tails is investigated by dissipative particle dynamics. The morphology can transform from vesicles to worm-like cylinders and further to spheres by increasing the interaction parameter between the hydrophilic heads. The results are in agreement with the experimental observations. Through changing the interaction parameter between hydrophilic head and solvents, the length of hydrophobic tail and the size of hydrophilic head, the self-assembled aggregates exhibit a rich variety of morphological structures, such as, spheres, vesicles, worm-like cylinders, disk-like micelles and layered-rod-like micelles. Vesicles form for short hydrophobic tail, while disk-like micelles are taken shape for longer hydrophobic tail. As further increasing the diameter of hydrophilic head, large compound micelles are obtained for short hydrophobic tail, however layered-rod-like micelles form for longer tail. The simulation findings might be valuable for guiding the experimental studies and fascinating new possibility and applications in material science. This work was financially supported by NNSFC (21474051 and 21074053), NBRPC (2010CB923303) and PCSIRT.

  11. Chiral plasmonics of self-assembled nanorod dimers

    PubMed Central

    Ma, Wei; Kuang, Hua; Wang, Libing; Xu, Liguang; Chang, Wei-Shun; Zhang, Huanan; Sun, Maozhong; Zhu, Yinyue; Zhao, Yuan; Liu, Liqiang; Xu, Chuanlai; Link, Stephan; Kotov, Nicholas A.

    2013-01-01

    Chiral nanoscale photonic systems typically follow either tetrahedral or helical geometries that require four or more different constituent nanoparticles. Smaller number of particles and different chiral geometries taking advantage of the self-organization capabilities of nanomaterials will advance understanding of chiral plasmonic effects, facilitate development of their theory, and stimulate practical applications of chiroplasmonics. Here we show that gold nanorods self-assemble into side-by-side orientated pairs and “ladders” in which chiral properties originate from the small dihedral angle between them. Spontaneous twisting of one nanorod versus the other one breaks the centrosymmetric nature of the parallel assemblies. Two possible enantiomeric conformations with positive and negative dihedral angles were obtained with different assembly triggers. The chiral nature of the angled nanorod pairs was confirmed by 4? full space simulations and the first example of single-particle CD spectroscopy. Self-assembled nanorod pairs and “ladders” enable the development of chiral metamaterials, (bio)sensors, and new catalytic processes. PMID:23752317

  12. Chiral plasmonics of self-assembled nanorod dimers.

    PubMed

    Ma, Wei; Kuang, Hua; Wang, Libing; Xu, Liguang; Chang, Wei-Shun; Zhang, Huanan; Sun, Maozhong; Zhu, Yinyue; Zhao, Yuan; Liu, Liqiang; Xu, Chuanlai; Link, Stephan; Kotov, Nicholas A

    2013-01-01

    Chiral nanoscale photonic systems typically follow either tetrahedral or helical geometries that require four or more different constituent nanoparticles. Smaller number of particles and different chiral geometries taking advantage of the self-organization capabilities of nanomaterials will advance understanding of chiral plasmonic effects, facilitate development of their theory, and stimulate practical applications of chiroplasmonics. Here we show that gold nanorods self-assemble into side-by-side orientated pairs and "ladders" in which chiral properties originate from the small dihedral angle between them. Spontaneous twisting of one nanorod versus the other one breaks the centrosymmetric nature of the parallel assemblies. Two possible enantiomeric conformations with positive and negative dihedral angles were obtained with different assembly triggers. The chiral nature of the angled nanorod pairs was confirmed by 4? full space simulations and the first example of single-particle CD spectroscopy. Self-assembled nanorod pairs and "ladders" enable the development of chiral metamaterials, (bio)sensors, and new catalytic processes. PMID:23752317

  13. Using lateral capillary forces to compute by self-assembly.

    PubMed

    Rothemund, P W

    2000-02-01

    Investigations of DNA computing have highlighted a fundamental connection between self-assembly (SA) and computation: in principle, any computation can be performed by a suitable self-assembling system. In practice, exploration of this connection is limited by our ability to control the geometry and specificity of binding interactions. Recently, a system has been developed that uses surface tension to assemble plastic tiles according to shape complementarity and likeness of wetting [Bowden, N., Terfort, A., Carbeck, J. & Whitesides, G. M. (1997) Science 276, 233-235]. Here the capacity of this system to compute by SA is explored. Tiles were prepared to test the system's ability to generate three structures of increasing complexity: a periodic checkerboard tiling, an aperiodic Penrose tiling, and a computational tiling that simulates a one-dimensional cellular automaton. Matching rules for these tilings were enforced by coating tiles with patterns of hydrophobic and hydrophilic patches or wetting codes. Energetic, kinetic, and mechanistic details of SA explain differences between experimental structures and mathematically ideal ones. In particular, the growth mechanism observed appears incompatible with computations that make use of a chosen input. PMID:10655471

  14. Molecular Self-Assembly at Metal-Electrolyte Interfaces

    PubMed Central

    Phan, Thanh Hai; Wandelt, Klaus

    2013-01-01

    The self-assembly of molecular layers has become an important strategy in modern design of functional materials. However, in particular, large organic molecules may no longer be sufficiently volatile to be deposited by vapor deposition. In this case, deposition from solution may be a promising route; in ionic form, these molecules may even be soluble in water. In this contribution, we present and discuss results on the electrochemical deposition of viologen- and porphyrin molecules as well as their co-adsorption on chloride modified Cu(100) and Cu(111) single crystal electrode surfaces from aqueous acidic solutions. Using in situ techniques like cyclic voltametry and high resolution scanning tunneling microscopy, as well as ex-situ photoelectron spectroscopy data the highly ordered self-assembled organic layers are characterized with respect to their electrochemical behavior, lateral order and inner conformation as well as phase transitions thereof as a function of their redox-state and the symmetry of the substrate. As a result, detailed structure models are derived and are discussed in terms of the prevailing interactions. PMID:23439555

  15. Silver nanoprisms self-assembly on differently functionalized silica surface

    NASA Astrophysics Data System (ADS)

    Pilipavicius, J.; Chodosovskaja, A.; Beganskiene, A.; Kareiva, A.

    2015-03-01

    In this work colloidal silica/silver nanoprisms (NPRs) composite coatings were made. Firstly colloidal silica sols were synthesized by sol-gel method and produced coatings on glass by dip-coating technique. Next coatings were silanized by (3-Aminopropyl)triethoxysilane (APTES), N-[3-(Trimethoxysilyl)propyl]ethylenediamine (AEAPTMS), (3- Mercaptopropyl)trimethoxysilane (MPTMS). Silver NPRs where synthesized via seed-mediated method and high yield of 94±15 nm average edge length silver NPRs were obtained with surface plasmon resonance peak at 921 nm. Silica-Silver NPRs composite coatings obtained by selfassembly on silica coated-functionalized surface. In order to find the most appropriate silanization way for Silver NPRs self-assembly, the composite coatings were characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), water contact angle (CA) and surface free energy (SFE) methods. Results have showed that surface functionalization is necessary to achieve self-assembled Ag NPRs layer. MPTMS silanized coatings resulted sparse distribution of Ag NPRs. Most homogeneous, even distribution composite coatings obtained on APTES functionalized silica coatings, while AEAPTMS induced strong aggregation of Silver NPRs.

  16. Self-assembled dummy patterns for lithography process margin enhancement

    NASA Astrophysics Data System (ADS)

    Moon, James; Nam, Byoung-Sub; Jeong, Joo-Hong; Nam, Byung-Ho; Yim, Dong Gyu

    2007-03-01

    Over the last couple of years, Design For Manufacturability (DFM) has progressed from concept to practice. What we thought then is actually applied to the design step to meet the high demand placed upon very high tech devices we make today. One of the DFM procedures that benefit the lithography process margin is generation of dummy patterns. Dummy pattern generated at design step enables stable yet high lithography process margin for many of the high technology device. But actual generation of the dummy pattern is very complex and risky for many of the layer used for memory devices. Dummy generation for simple pattern layers such as Poly or Isolation layer is not so difficult since pattern composed for these layers are usually 1 dimensional or very simple 2 dimensional patterns. But for interconnection layers that compose of complex 2 dimensional patterns, dummy pattern generation is very risky and requires lots of time and effort to safely place the dummy patterns. In this study, we propose simple self assembled dummy (SAD) generation algorithm to place dummy pattern for the complex 2 dimensional interconnection layers. This algorithm automatically self assembles dummy pattern based on the original design layout, therefore insuring the safety and simplicity of the generated dummy to the original design. Also we will evaluate SAD on interconnection layer using commercial Model Based Verification (MBV) tool to verify its applicability for both litho process margin and DFM perspective.

  17. Liposomes self-assembled from electrosprayed composite microparticles

    NASA Astrophysics Data System (ADS)

    Yu, Deng-Guang; Yang, Jun-He; Wang, Xia; Tian, Feng

    2012-03-01

    Composite microparticles, consisting of polyvinylpyrrolidone (PVP), naproxen (NAP) and lecithin (PC), have been successfully prepared using an electrospraying process and exploited as templates to manipulate molecular self-assembly for the synthesis of liposomes in situ. Field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) observations demonstrate that the microparticles have an average diameter of 960 ± 140 nm and a homogeneous structure. X-ray diffraction (XRD) patterns, differential scanning calorimetry (DSC) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) results verify that the building blocks NAP and PC are scattered in the polymer matrix in a molecular way owing to the very fast drying of the electrospraying process and the favorable secondary interactions among the components. FESEM, scanning probe microscope (SPM) and TEM observations demonstrate that the liposomes can be achieved through molecular self-assembly in situ when the microparticles contact water thanks to ‘like prefers like’ and by means of the confinement effect of the microparticles. The liposomes have an encapsulation rate of 91.3%, and 80.7% of the drug in the liposomes can be freed into the dissolution medium in a sustained way and by a diffusion mechanism over a period of 24 h. The developed strategy not only provides a new, facile, and effective method to assemble and organize molecules of multiple components into liposomes with electrosprayed microparticles as templates, but also opens a new avenue for nanofabrication in a step-by-step and controllable way.

  18. Reconstitution of Gloeobacter violaceus Rhodopsin with a Light-Harvesting Carotenoid Antenna†

    PubMed Central

    Imasheva, Eleonora S.; Balashov, Sergei P.; Choi, Ah Reum; Jung, Kwang-Hwan; Lanyi, Janos K.

    2009-01-01

    We show that salinixanthin, the light-harvesting carotenoid antenna of xanthorhodopsin, can be reconstituted into the retinal protein from Gloeobacter violaceus expressed in E. coli. Reconstitution of gloeobacter rhodopsin with the carotenoid is accompanied by characteristic absorption changes and the appearance of CD bands similar to those observed for xanthorhodopsin that indicate immobilization and twist of the carotenoid in the binding site. As in xanthorhodopsin, the carotenoid functions as a light-harvesting antenna. The excitation spectrum for retinal fluorescence emission shows that ca. 36% of the energy absorbed by the carotenoid is transferred to the retinal. From excitation anisotropy, we calculate the angle between the two chromophores as ca. 50°, similar to that in xanthorhodopsin. The results indicate that gloeobacter rhodopsin binds salinixanthin in a similar way as xanthorhodopsin, and suggest that it might bind a carotenoid also in vivo. In the crystallographic structure of xanthorhodopsin, the conjugated chain of the carotenoid lies on the surface of helices E and F, and the 4-keto-ring is immersed in the protein at van der Waals distance from the ionone ring of the retinal. The 4-keto-ring is in the space occupied by a tryptophan in bacteriorhodopsin, which is replaced by the smaller glycine in xanthorhodopsin and gloeobacter rhodopsin. Specific binding of the carotenoid and its light-harvesting function are eliminated by a single mutation of the gloeobacter protein that replaces this glycine with a tryptophan. This indicates that the 4-keto-ring is critically involved in carotenoid binding, and suggests that a number of other recently identified retinal proteins, from a diverse group of organisms, could also contain carotenoid antenna since they carry the homologous glycine near the retinal. PMID:19842712

  19. Reconstitution of Gloeobacter violaceus rhodopsin with a light-harvesting carotenoid antenna.

    PubMed

    Imasheva, Eleonora S; Balashov, Sergei P; Choi, Ah Reum; Jung, Kwang-Hwan; Lanyi, Janos K

    2009-11-24

    We show that salinixanthin, the light-harvesting carotenoid antenna of xanthorhodopsin, can be reconstituted into the retinal protein from Gloeobacter violaceus expressed in Escherichia coli. Reconstitution of gloeobacter rhodopsin with the carotenoid is accompanied by characteristic absorption changes and the appearance of CD bands similar to those observed for xanthorhodopsin that indicate immobilization and twist of the carotenoid in the binding site. As in xanthorhodopsin, the carotenoid functions as a light-harvesting antenna. The excitation spectrum for retinal fluorescence emission shows that ca. 36% of the energy absorbed by the carotenoid is transferred to the retinal. From excitation anisotropy, we calculate the angle between the two chromophores as being ca. 50 degrees , similar to that in xanthorhodopsin. The results indicate that gloeobacter rhodopsin binds salinixanthin in a manner similar to that of xanthorhodopsin and suggest that it might bind a carotenoid also in vivo. In the crystallographic structure of xanthorhodopsin, the conjugated chain of the carotenoid lies on the surface of helices E and F, and the 4-keto ring is immersed in the protein at van der Waals distance from the ionone ring of the retinal. The 4-keto ring is in the space occupied by a tryptophan in bacteriorhodopsin, which is replaced by the smaller glycine in xanthorhodopsin and gloeobacter rhodopsin. Specific binding of the carotenoid and its light-harvesting function are eliminated by a single mutation of the gloeobacter protein that replaces this glycine with a tryptophan. This indicates that the 4-keto ring is critically involved in carotenoid binding and suggests that a number of other recently identified retinal proteins, from a diverse group of organisms, could also contain carotenoid antenna since they carry the homologous glycine near the retinal. PMID:19842712

  20. Path induced coherent energy transfer in light-harvesting complexes in purple bacteria

    NASA Astrophysics Data System (ADS)

    Sun, Kewei; Ye, Jun; Zhao, Yang

    2014-09-01

    Features of path dependent energy transfer in a dual-ring light-harvesting (LH2) complexes (B850) system have been examined in detail systematically. The Frenkel-Dirac time dependent variational method with the Davydov D1 Ansatz is employed with detailed evolution of polaron dynamics in real space readily obtained. It is found that the phase of the transmission amplitude through the LH2 complexes plays an important role in constructing the coherent excitonic energy transfer. It is also found that the symmetry breaking caused by the dimerization of bacteriochlorophylls and coherence or correlation between two rings will be conducive in enhancing the exciton transfer efficiency.

  1. Long-distance electronic energy transfer in light-harvesting supramolecular polymers.

    PubMed

    Winiger, Christian B; Li, Shaoguang; Kumar, Ganesh R; Langenegger, Simon M; Häner, Robert

    2014-12-01

    The efficient collection of solar energy relies on the design and construction of well-organized light-harvesting systems. Herein we report that supramolecular phenanthrene polymers doped with pyrene are effective collectors of light energy. The linear polymers are formed through the assembly of short amphiphilic oligomers in water. Absorption of light by phenanthrene residues is followed by electronic energy transfer along the polymer over long distances (>100?nm) to the accepting pyrene molecules. The high efficiency of the energy transfer, which is documented by large fluorescence quantum yields, suggests a quantum coherent process. PMID:25345576

  2. Fluorescence enhancement of light-harvesting complex 2 from purple bacteria coupled to spherical gold nanoparticles

    SciTech Connect

    Bujak, L; Czechowski, N; Piatkowski, D; Litvin, R; Mackowski, S; Brotosudarmo, Tatas H.P.; Cogdell, Richard J; Pichler, S; Heiss, W

    2011-01-01

    The influence of plasmon excitations in spherical gold nanoparticles on the optical properties of a light-harvesting complex 2 (LH2) from the purple bacteria Rhodopseudomonas palustris has been studied. Systematic analysis is facilitated by controlling the thickness of a silica layer between Au nanoparticles and LH2 complexes. Fluorescence of LH2 complexes features substantial increase when these complexes are separated by 12 nm from the gold nanoparticles. At shorter distances, non-radiative quenching leads to a decrease of fluorescence emission. The enhancement of fluorescence originates predominantly from an increase of absorption of pigments comprising the LH2 complex.

  3. Theory of femtosecond coherent double-pump single-molecule spectroscopy: Application to light harvesting complexes

    NASA Astrophysics Data System (ADS)

    Chen, Lipeng; Gelin, Maxim F.; Domcke, Wolfgang; Zhao, Yang

    2015-04-01

    We develop a first principles theoretical description of femtosecond double-pump single-molecule signals of molecular aggregates. We incorporate all singly excited electronic states and vibrational modes with significant exciton-phonon coupling into a system Hamiltonian and treat the ensuing system dynamics within the Davydov D1 Ansatz. The remaining intra- and inter-molecular vibrational modes are treated as a heat bath and their effect is accounted for through lineshape functions. We apply our theory to simulate single-molecule signals of the light harvesting complex II. The calculated signals exhibit pronounced oscillations of mixed electron-vibrational (vibronic) origin. Their periods decrease with decreasing exciton-phonon coupling.

  4. Neutron and light scattering studies of light-harvesting photosynthetic antenna complexes

    SciTech Connect

    Tang, Kuo-Hsiang [Washington Univ., St. Louis, MO (United States); Blankenship, Robert E. [Washington Univ., St. Louis, MO (United States)

    2011-06-28

    Small-angle neutron scattering (SANS) and dynamic light scattering (DLS) have been employed in studying the structural information of various biological systems, particularly in systems without high-resolution structural information available. In this report, we briefly present some principles and biological applications of neutron scattering and DLS, compare the differences in information that can be obtained with small-angle X-ray scattering (SAXS), and then report recent studies of SANS and DLS, together with other biophysical approaches, for light-harvesting antenna complexes and reaction centers of purple and green phototrophic bacteria.

  5. Construction of energy transfer pathways self-assembled from DNA-templated stacks of anthracene.

    PubMed

    Iwaura, Rika; Yui, Hiroharu; Someya, Yuu; Ohnishi-Kameyama, Mayumi

    2014-01-01

    We describe optical properties of anthracene stacks formed from single-component self-assembly of thymidylic acid-appended anthracene 2,6-bis[5-(3'-thymidylic acid)pentyloxy] anthracene (TACT) and the binary self-assembly of TACT and complementary 20-meric oligoadenylic acid (TACT/dA20) in an aqueous buffer. UV-Vis and emission spectra for the single-component self-assembly of TACT and the binary self-assembly of TACT/dA20 were very consistent with stacked acene moieties in both self-assemblies. Interestingly, time-resolved fluorescence spectra from anthracene stacks exhibited very different features of the single-component and binary self-assemblies. In the single-component self-assembly of TACT, a dynamic Stokes shift (DSS) and relatively short fluorescence lifetime (?=0.35ns) observed at around 450nm suggested that the anthracene moieties were flexible. Moreover, a broad emission at 530nm suggested the formation of an excited dimer (excimer). In the binary self-assembly of TACT/dA20, we detected a broad, red-shifted emission component at 534nm with a lifetime (?=0.4ns) shorter than that observed in the TACT single-component self-assembly. Combining these results with the emission spectrum of the binary self-assembly of TACT/5'-HEX dA20, we concluded that the energy transfer pathway was constructed by columnar anthracene stacks formed from the DNA-templated self-assembly of TACT. PMID:24342131

  6. Self-Assembly of the Ionic Peptide EAK16: The Effect of Charge Distributions on Self-Assembly

    PubMed Central

    Jun, S.; Hong, Y.; Imamura, H.; Ha, B.-Y.; Bechhoefer, J.; Chen, P.

    2004-01-01

    Amphiphilic peptides suspended in aqueous solution display a rich set of aggregation behavior. Molecular-level studies of relatively simple amphiphilic molecules under controlled conditions are an essential step toward a better understanding of self-assembly phenomena of naturally occurring peptides/proteins. Here, we study the influence of molecular architecture and interactions on the self-assembly of model peptides (EAK16s), using both experimental and theoretical approaches. Three different types of EAK16 were studied: EAK16-I, -II, and -IV, which have the same amino acid composition but different amino acid sequences. Atomic force microscopy confirms that EAK16-I and -II form fibrillar assemblies, whereas EAK16-IV forms globular structures. The Fourier transform infrared spectrum of EAK16-IV indicates the possible formation of a ?-turn structure, which is not found in EAK16-I and -II. Our theoretical and numerical studies suggest the underlying mechanism behind these observations. We show that the hairpin structure is energetically stable for EAK16-IV, whereas the chain entropy of EAK16-I and -II favors relatively stretched conformations. Our combined experimental and theoretical approaches provide a clear picture of the interplay between single-chain properties, as determined by peptide sequences (or charge distributions), and the emerging structure at the nano (or more coarse-grained) level. PMID:15298927

  7. Electrochemical Properties of Organosilane Self Assembled Monolayers on Aluminum 2024

    NASA Technical Reports Server (NTRS)

    Hintze, Paul E.; Calle, Luz Marina

    2004-01-01

    Self assembled monolayers are commonly used to modify surfaces. Within the last 15 years, self assembled monolayers have been investigated as a way to protect from corrosion[1,2] or biofouling.[3] In this study, self assembled monolayers of decitriethoxysilane (C10H21Si(OC2H5)3) and octadecyltriethoxysilane (C18H37Si(OC2H5)3) were formed on aluminum 2024-T3. The modified surfaces and bare Al 2024 were characterized by dynamic water contact angle measurements, x-ray photoelectron spectroscopy (XIPS) and infrared spectroscopy. Electrochemical impedance spectroscopy (EIS) in 0.5 M NaCl was used to characterize the monolayers and evaluate their corrosion protection properties. The advancing water contact angle and infrared measurements show that the mono layers form a surface where the hydrocarbon chains are packed and oriented away from the surface, consistent with what is found in similar systems. The contact angle hysteresis measured in these systems is relatively large, perhaps indicating that the hydrocarbon chains are not as well packed as monolayers formed on other substrates. The results of the EIS measurements were modeled using a Randle's circuit modified by changing the capacitor to a constant phase element. The constant phase element values were found to characterize the monolayer. The capacitance of the monolayer modified surface starts lower than the bare Al 2024, but approaches values similar to the bare Al 2024 within 24 hours as the monolayer is degraded. The n values found for bare Al 2024 quickly approach the value of a true capacitor and are greater than 0.9 within hours after the start of exposure. For the monolayer modified structure, n can stay lower than 0.9 for a longer period of time. In fact, n for the monolayer modified surfaces is different from the bare surface even after the capacitance values have converged. This indicates that the deviation from ideal capacitance is the most sensitive indicator of the presence of the monolayer.

  8. Principles Governing the Self Assembly of Polypeptide Nanoparticles

    NASA Astrophysics Data System (ADS)

    Wahome, Newton

    Self assembling systems on the nanometer scale afford the advantage of being able to control submicron level events. In this study, we focus on the self-assembling polypeptide nanoparticles (SAPN). The SAPN scaffold is made up of oligomerizing domains that align along the principle rotational axes of icosahedral symmetry. By aligning them along these axes, a particle with spherical geometry can be achieved. This particle can be utilized as a vaccine, as a drug delivery vehicle, or as a biomedical imaging device. This research will try to answer why the SAPN self-assembles into distinct molecular weight ranges while mostly maintaining a spherical morphology. The first means will be theoretical and computational, where we will utilize a mathematical formalism to find out how the packing of SAPN's monomeric units can occur within symmetric space. Then molecular dynamics will be run within this symmetric space to test the per amino acid residue susceptibility of SAPN towards becoming polymorphic in nature. Means for examining the aggregation propensity of SAPN will be also be tested. Specifically, the relationship of different sequences of SAPN with pH will be elucidated. Co-assembly of SAPN to reduce the surface density of an aggregation prone epitope will be tested. Also, aggregation reduction consisting of the exchange of an anionic denaturant with a positively charged suppressor in order to mitigate a priori peptide association and misfolding, will also be attempted. SAPN has been shown to be an immunogenic platform for the presentation of pathogen derived antigens. We will attempt to show the efficacy of presenting an antigen from HIV-1 which is structurally restrained to best match the native conformation on the virus. Immunological studies will be performed to test the effect of this approach, as well testing the antigenicity of the nanoparticle in the absence of adjuvant. Finally, the antigen presenting nanoparticles will undergo formulation testing, to measure the feasibility of SAPN for lyophilization. The regular buffers for refolding will be optimized, or replaced, in order to enhance the formation of a uniform powder, one that will not enhance the aggregation potential of the peptide species once freeze-drying has occurred.

  9. Charge Conduction and Breakdown Mechanisms in Self-Assembled Nanodielectrics

    SciTech Connect

    DiBenedetto, S.; Facchetti, A; Ratner, M; Marks, T

    2009-01-01

    Developing alternative high dielectric constant (k) materials for use as gate dielectrics is essential for continued advances in conventional inorganic CMOS and organic thin film transistors (OTFTs). Thicker films of high-k materials suppress tunneling leakage currents while providing effective capacitances comparable to those of thin films of lower-k materials. Self-assembled monolayers (SAMs) and multilayers offer attractive options for alternative OTFT gate dielectrics. One class of materials, organosilane-based self-assembled nanodielectrics (SANDs), has been shown to form robust films with excellent insulating and surface passivation properties, enhancing both organic and inorganic TFT performance and lowering device operating voltages. Since gate leakage current through the dielectric is one factor limiting continued TFT performance improvements, we investigate here the current (voltage, temperature) (I (V,T)) transport characteristics of SAND types II ({Pi}-conjugated layer) and III ({sigma}-saturated + {Pi}-conjugated layers) in Si/native SiO{sub 2}/SAND/Au metal-insulator-metal (MIS) devices over the temperature range -60 to +100 C. It is found that the location of the {Pi}-conjugated layer with respect to the Si/SiO{sub 2} substrate surface in combination with a saturated alkylsilane tunneling barrier is crucial in controlling the overall leakage current through the various SAND structures. For small applied voltages, hopping transport dominates at all temperatures for the {Pi}-conjugated system (type II). However, for type III SANDs, the {sigma}- and {Pi}- monolayers dominate the transport in two different transport regimes: hopping between +25 C and +100 C, and an apparent switch to tunneling for temperatures below 25 C. The {sigma}-saturated alkylsilane tunneling barrier functions to reduce type III current leakage by blocking injected electrons, and by enabling bulk-dominated (Poole-Frenkel) transport vs electrode-dominated (Schottky) transport in type II SANDs. These observations provide insights for designing next-generation self-assembled gate dielectrics, since the bulk-dominated transport resulting from combining {sigma}- and {Pi}-layers should enable realization of gate dielectrics with further enhanced performance.

  10. From self-assembly fundamental knowledge to nanomedicine developments.

    PubMed

    Monduzzi, Maura; Lampis, Sandrina; Murgia, Sergio; Salis, Andrea

    2014-03-01

    This review highlights the key role of NMR techniques in demonstrating the molecular aspects of the self-assembly of surfactant molecules that nowadays constitute the basic knowledge which modern nanoscience relies on. The aim is to provide a tutorial overview. The story of a rigorous scientific approach to understand self-assembly in surfactant systems and biological membranes starts in the early seventies when the progresses of SAXRD and NMR technological facilities allowed to demonstrate the existence of ordered soft matter, and the validity of Tanford approach concerning self-assembly at a molecular level. Particularly, NMR quadrupolar splittings, NMR chemical shift anisotropy, and NMR relaxation of dipolar and quadrupolar nuclei in micellar solutions, microemulsions, and liquid crystals proved the existence of an ordered polar-apolar interface, on the NMR time scale. NMR data, rationalized in terms of the two-step model of relaxation, allowed to quantify the dynamic aspects of the supramolecular aggregates in different soft matter systems. In addition, NMR techniques allowed to obtain important information on counterion binding as well as on size of the aggregate through molecular self-diffusion. Indeed NMR self-diffusion proved without any doubt the existence of bicontinuous microemulsions and bicontinuous cubic liquid crystals, suggested by pioneering and brilliant interpretation of SAXRD investigations. Moreover, NMR self-diffusion played a fundamental role in the understanding of microemulsion and emulsion nanostructures, phase transitions in phase diagrams, and particularly percolation phenomena in microemulsions. Since the nineties, globalization of the knowledge along with many other technical facilities such as electron microscopy, particularly cryo-EM, produced huge progresses in surfactant and colloid science. Actually we refer to nanoscience: bottom up/top down strategies allow to build nanodevices with applications spanning from ICT to food technology. Developments in the applied fields have also been addressed by important progresses in theoretical skills aimed to understand intermolecular forces, and specific ion interactions. Nevertheless, this is still an open question. Our predictive ability has however increased, hence more ambitious targets can be planned. Nanomedicine represents a major challenging field with its main aims: targeted drug delivery, diagnostic, theranostics, tissue engineering, and personalized medicine. Few recent examples will be mentioned. Although the real applications of these systems still need major work, nevertheless new challenges are open, and perspectives based on integrated multidisciplinary approaches would enable both a deeper basic knowledge and the expected advances in biomedical field. PMID:24182715

  11. Circular dichroism of bacteriochlorophyll a in light-harvesting bacteriochlorophyll-protein complexes from Rhodopseudomonas palustris.

    PubMed

    Hayashi, H; Nozawa, T; Hatano, M; Morita, S

    1982-03-01

    Bacteriochlorophyll (Bchl)-protein complexes containing light-harvesting Bchls were isolated from Rhodopseudomonas palustris, and the CD spectra of these complexes were measured in the near-infrared region. These isolated Bchl-protein complexes retained the CD signals of light-harvesting Bchls that were observed in intracytoplasmic membrane preparation. Comparison of the CD spectrum of B870-reaction center complexes with that of the isolated reaction centers revealed that the peak at 860 nm and the trough at 890 nm were attributable to the B870 spectral form, and that the peak at 790 nm and the trough at 810 nm were not all attributable to the reaction center. The CD spectra of spectrally different types of B800--850 complex revealed that the magnitudes of the peak at 840--850 nm and the trough at 860--870 nm were correlated with the magnitude of the absorption peak at around 850 nm. Therefore, these positive and negative CD bands were attributable to the B850 spectral form. In a similar manner, the peak at 810--820 nm and trough at 790 nm were attributable to the B800 spectral form. PMID:7076643

  12. Zeaxanthin Radical Cation Formation in Minor Light-Harvesting Complexes of Higher Plant Antenna

    SciTech Connect

    Avenson, Thomas H.; Ahn, Tae Kyu; Zigmantas, Donatas; Niyogi, Krishna K.; Li, Zhirong; Ballottari, Matteo; Bassi, Roberto; Fleming, Graham R.

    2008-01-31

    Previous work on intact thylakoid membranes showed that transient formation of a zeaxanthin radical cation was correlated with regulation of photosynthetic light-harvesting via energy-dependent quenching. A molecular mechanism for such quenching was proposed to involve charge transfer within a chlorophyll-zeaxanthin heterodimer. Using near infrared (880-1100 nm) transient absorption spectroscopy, we demonstrate that carotenoid (mainly zeaxanthin) radical cation generation occurs solely in isolated minor light-harvesting complexes that bind zeaxanthin, consistent with the engagement of charge transfer quenching therein. We estimated that less than 0.5percent of the isolated minor complexes undergo charge transfer quenching in vitro, whereas the fraction of minor complexes estimated to be engaged in charge transfer quenching in isolated thylakoids was more than 80 times higher. We conclude that minor complexes which bind zeaxanthin are sites of charge transfer quenching in vivo and that they can assume Non-quenching and Quenching conformations, the equilibrium LHC(N)<--> LHC(Q) of which is modulated by the transthylakoid pH gradient, the PsbS protein, and protein-protein interactions.

  13. Energy transfer and clustering of photosynthetic light-harvesting complexes in reconstituted lipid membranes

    NASA Astrophysics Data System (ADS)

    Dewa, Takehisa; Sumino, Ayumi; Watanabe, Natsuko; Noji, Tomoyasu; Nango, Mamoru

    2013-06-01

    In purple photosynthetic bacteria, light-harvesting complex 2 (LH2) and light harvesting/reaction centre core complex (LH1-RC) play the key roles of capturing and transferring light energy and subsequent charge separation. These photosynthetic apparatuses form a supramolecular assembly; however, how the assembly influences the efficiency of energy conversion is not yet clear. We addressed this issue by evaluating the energy transfer in reconstituted photosynthetic protein complexes LH2 and LH1-RC and studying the structures and the membrane environment of the LH2/LH1-RC assemblies, which had been embedded into various lipid bilayers. Thus, LH2 and LH1-RC from Rhodopseudomonas palustris 2.1.6 were reconstituted in phosphatidylglycerol (PG), phosphatidylcholine (PC), and phosphatidylethanolamine (PE)/PG/cardiolipin (CL). Efficient energy transfer from LH2 to LH1-RC was observed in the PC and PE/PG/CL membranes. Atomic force microscopy revealed that LH2 and LH1-RC were heterogeneously distributed to form clusters in the PC and PE/PG/CL membranes. The results indicated that the phospholipid species influenced the cluster formation of LH2 and LH1-RC as well as the energy transfer efficiency.

  14. Chlorophyll and carotenoid binding in a simple red algal light-harvesting complex crosses phylogenetic lines.

    PubMed

    Grabowski, B; Cunningham, F X; Gantt, E

    2001-02-27

    The membrane proteins of peripheral light-harvesting complexes (LHCs) bind chlorophylls and carotenoids and transfer energy to the reaction centers for photosynthesis. LHCs of chlorophytes, chromophytes, dinophytes, and rhodophytes are similar in that they have three transmembrane regions and several highly conserved Chl-binding residues. All LHCs bind Chl a, but in specific taxa certain characteristic pigments accompany Chl a: Chl b and lutein in chlorophytes, Chl c and fucoxanthin in chromophytes, Chl c and peridinin in dinophytes, and zeaxanthin in rhodophytes. The specificity of pigment binding was examined by in vitro reconstitution of various pigments with a simple light-harvesting protein (LHCaR1), from a red alga (Porphyridium cruentum), that normally has eight Chl a and four zeaxanthin molecules. The pigments typical of a chlorophyte (Spinacea oleracea), a chromophyte (Thallasiosira fluviatilis), and a dinophyte (Prorocentrum micans) were found to functionally bind to this protein as evidenced by their participation in energy transfer to Chl a, the terminal pigment. This is a demonstration of a functional relatedness of rhodophyte and higher plant LHCs. The results suggest that eight Chl-binding sites per polypeptide are an ancestral trait, and that the flexibility to bind various Chl and carotenoid pigments may have been retained throughout the evolution of LHCs. PMID:11226340

  15. Lutein epoxide cycle, light harvesting and photoprotection in species of the tropical tree genus Inga.

    PubMed

    Matsubara, Shizue; Krause, G Heinrich; Seltmann, Martin; Virgo, Aurelio; Kursar, Thomas A; Jahns, Peter; Winter, Klaus

    2008-04-01

    Dynamics and possible function of the lutein epoxide (Lx) cycle, that is, the reversible conversion of Lx to lutein (L) in the light-harvesting antennae, were investigated in leaves of tropical tree species. Photosynthetic pigments were quantified in nine Inga species and species from three other genera. In Inga, Lx levels were high in shade leaves (mostly above 20 mmol mol(-1) chlorophyll) and low in sun leaves. In Virola surinamensis, both sun and shade leaves exhibited very high Lx contents (about 60 mmol mol(-1) chlorophyll). In Inga marginata grown under high irradiance, Lx slowly accumulated within several days upon transfer to deep shade. When shade leaves of I. marginata were briefly exposed to the sunlight, both violaxanthin and Lx were quickly de-epoxidized. Subsequently, overnight recovery occurred only for violaxanthin, not for Lx. In such leaves, containing reduced levels of Lx and increased levels of L, chlorophyll fluorescence induction showed significantly slower reduction of the photosystem II electron acceptor, Q(A), and faster formation as well as a higher level of non-photochemical quenching. The results indicate that slow Lx accumulation in Inga leaves may improve light harvesting under limiting light, while quick de-epoxidation of Lx to L in response to excess light may enhance photoprotection. PMID:18208510

  16. Crystal structure of spinach major light-harvesting complex at 2.72Å resolution

    NASA Astrophysics Data System (ADS)

    Liu, Zhenfeng; Yan, Hanchi; Wang, Kebin; Kuang, Tingyun; Zhang, Jiping; Gui, Lulu; An, Xiaomin; Chang, Wenrui

    2004-03-01

    The major light-harvesting complex of photosystem II (LHC-II) serves as the principal solar energy collector in the photosynthesis of green plants and presumably also functions in photoprotection under high-light conditions. Here we report the first X-ray structure of LHC-II in icosahedral proteoliposome assembly at atomic detail. One asymmetric unit of a large R32 unit cell contains ten LHC-II monomers. The 14 chlorophylls (Chl) in each monomer can be unambiguously distinguished as eight Chla and six Chlb molecules. Assignment of the orientation of the transition dipole moment of each chlorophyll has been achieved. All Chlb are located around the interface between adjacent monomers, and together with Chla they are the basis for efficient light harvesting. Four carotenoid-binding sites per monomer have been observed. The xanthophyll-cycle carotenoid at the monomer-monomer interface may be involved in the non-radiative dissipation of excessive energy, one of the photoprotective strategies that have evolved in plants.

  17. Allosteric regulation of the light-harvesting system of photosystem II.

    PubMed Central

    Horton, P; Ruban, A V; Wentworth, M

    2000-01-01

    Non-photochemical quenching of chlorophyll fluorescence (NPQ) is symptomatic of the regulation of energy dissipation by the light-harvesting antenna of photosystem II (PS II). The kinetics of NPQ in both leaves and isolated chloroplasts are determined by the transthylakoid delta pH and the de-epoxidation state of the xanthophyll cycle. In order to understand the mechanism and regulation of NPQ we have adopted the approaches commonly used in the study of enzyme-catalysed reactions. Steady-state measurements suggest allosteric regulation of NPQ, involving control by the xanthophyll cycle carotenoids of a protonation-dependent conformational change that transforms the PS II antenna from an unquenched to a quenched state. The features of this model were confirmed using isolated light-harvesting proteins. Analysis of the rate of induction of quenching both in vitro and in vivo indicated a bimolecular second-order reaction; it is suggested that quenching arises from the reaction between two fluorescent domains, possibly within a single protein subunit. A universal model for this transition is presented based on simple thermodynamic principles governing reaction kinetics. PMID:11127991

  18. Light-Harvesting Antenna System from the Phototrophic Bacterium Roseiflexus castenholzii

    SciTech Connect

    Collins, Aaron M.; Qian, Pu; Tang, Q; Bocian, David F; Hunter, C Neil; Blankenship, R. E.

    2010-01-01

    Photosynthetic organisms have evolved diverse light-harvesting complexes to harness light of various qualities and intensities. Photosynthetic bacteria can have (bacterio)chlorophyll Q{sub y} antenna absorption bands ranging from ?650 to ?1100 nm. This broad range of wavelengths has allowed many organisms to thrive in unique light environments. Roseiflexus castenholzii is a niche-adapted, filamentous anoxygenic phototroph (FAP) that lacks chlorosomes, the dominant antenna found in most green bacteria, and here we describe the purification of a full complement of photosynthetic complexes: the light-harvesting (LH) antenna, reaction center (RC), and core complex (RC-LH). By high-performance liquid chromatography separation of bacteriochlorophyll and bacteriopheophytin pigments extracted from the core complex and the RC, the number of subunits that comprise the antenna was determined to be 15 ± 1. Resonance Raman spectroscopy of the carbonyl stretching region displayed modes indicating that 3C-acetyl groups of BChl a are all involved in molecular interactions probably similar to those found in LH1 complexes from purple photosynthetic bacteria. Finally, two-dimensional projections of negatively stained core complexes and the LH antenna revealed a closed, slightly elliptical LH ring with an average diameter of 130 ± 10 Å surrounding a single RC that lacks an H-subunit but is associated with a tetraheme c-type cytochrome.

  19. Photothermal light harvesting and light-gated molecular release by nanoporous gold disks

    NASA Astrophysics Data System (ADS)

    Santos, Greggy M.; Zhao, Fusheng; Zeng, Jianbo; Shih, Wei-Chuan

    2015-03-01

    Photothermal heating has been an effective mechanism for harvesting light energy by plasmonic resonance. Photothermally generated hyperthermia can alter cell behavior, change cell microenvironment, and promote or suppress cell growth. In the past, colloidal nanoparticles such as gold nanospheres, nanoshells, nanorods, and nanocages have been developed for various applications. Here, we show that nanoporous gold disks (NPGDs) with 400 nm diameter, 75 nm thickness, and 13 nm pores exhibit large specific surface area and effective photothermal light harvesting capability. Another potential application is demonstrated by light-gated, multi-step molecular release of pre-adsorbed R6G fluorescent dye on arrayed NPGDs. Through the use of time-resolved temperature mapping, the spatial and temporal characteristics of photothermal heating in NPGD arrays is successfully demonstrated for both aqueous and air ambient environments. By applying a thermodynamic model to our experimental data, we determined the photothermal conversion efficiency at 56% for NPGD arrays. As a potential application, light-gated, multi-stage release of pre-adsorbed R6G dye molecules from NPGD arrays has been demonstrated. The results establish the foundation that NPGDs can be employed for photothermal light harvesting and light-gated molecular release.

  20. Self-Assembly of Filamentous Amelogenin Requires Calcium and Phosphate: From Dimers via Nanoribbons to Fibrils

    E-print Network

    Sali, Andrej

    Self-Assembly of Filamentous Amelogenin Requires Calcium and Phosphate: From Dimers via Nanoribbons calcium, phosphate, and pH 4.0-6.0. The pH range suggests that the formation of ion bridges through the importance of calcium and phosphate in self-assembly. X-ray scattering characterized amelo- genin dimers