Series Of Assemblies Research Articles

Tailored Cross-β Assemblies Establish Peptide "Dominos" Structures for Anchoring Undruggable Pharmacophores.

β-sheets have the ability to hierarchically stack into assemblies, and much effort has been spent on designing different peptides to regulate their assembly behaviors. Although the progress is remarkable, it remains challenging to manipulate them in a controllable way for achieving both tailored structures and specific functions. In this study, we obtained bola-like peptides using de novo design and combinatorial chemical screening. By regulating the solvent-accessible surface area of the peptide chain, a series of assemblies with different tilt angles and active sites of the β-sheet were obtained, resembling collapsed dominos. The structure-activity relationship of the optimized peptide NQ40 system was established and its ability to target the PD-L1 was demonstrated. This study successfully established the structure-function relationship of β-sheets assemblies and has positive implications on the rational design of peptide assemblies that possess recognition abilities.

Tailored Cross‐β Assemblies Establish Peptide “Dominos” Structures for Anchoring Undruggable Pharmacophores

Abstractβ‐sheets have the ability to hierarchically stack into assemblies, and much effort has been spent on designing different peptides to regulate their assembly behaviors. Although the progress is remarkable, it remains challenging to manipulate them in a controllable way for achieving both tailored structures and specific functions. In this study, we obtained bola‐like peptides using de novo design and combinatorial chemical screening. By regulating the solvent‐accessible surface area of the peptide chain, a series of assemblies with different tilt angles and active sites of the β‐sheet were obtained, resembling collapsed dominos. The structure‐activity relationship of the optimized peptide NQ40 system was established and its ability to target the PD‐L1 was demonstrated. This study successfully established the structure‐function relationship of β‐sheets assemblies and has positive implications on the rational design of peptide assemblies that possess recognition abilities.

Assembly and Pre-Loading Specifications for the Series Production of the Nb3Sn MQXFA Quadrupole Magnets for the HL-LHC

The High Luminosity LHC (HL-LHC) Project is planning to install 16 cold-masses made with Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn quadrupole magnets in the LHC Interaction Regions to significantly increase its luminosity. Half of these cold masses are fabricated at BNL, FNAL, and LBNL under the US Accelerator Research Program (AUP). Each cold mass includes two identical Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn quadrupole magnets, called MQXFA with a magnetic length of 4.2 m. Currently, the AUP project has completed the fabrication and test of the first 5 pre-series magnets, and is working on the following 16 magnets for the series production. The brittleness and strain sensitivity of the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn superconducting material requires a careful definition of the allowable maximum stress in the windings during magnet assembly and pre-load, and a tight control of their variation within the whole coil length. Therefore, a series of assembly and pre-load specifications have been defined with the goals of minimizing the risk of conductor degradation and providing the mechanical support required to reach the nominal current during powering. In this paper we present the specifications defined for the MQXFA magnets and applied during the different assembly phases and during the pre-load process of the first 5 pre-series magnets.

Influence of reaction conditions on the self-assembly of the natural silk sericin protein.

In the past years, the self-assembly of specific proteins has been paid more and more attention due to their significant role in human health and fabrication of new materials. In this article, we explore the effect of reaction conditions on the self-assembly of natural silk sericin protein, including the molecular weight and the concentration of sericin, pH, and metal ions in the reaction system. The results indicate that all these factors, especially species and concentration of metal ions, could influence the self-assembly process of the silk sericin protein. A series of assemblies with various morphologies can be fabricated by modulating the reaction condition. The article may provide some clue for the understanding of the protein self-assembly in the body and a method to fabricate new organic materials with different morphology. Microsc. Res. Tech. 80:298-304, 2017. © 2016 Wiley Periodicals, Inc.

Electron-Transfer Kinetics within Supramolecular Assemblies of Donor Tetrapyrrolytic Dyes and an Acceptor Palladium Cluster.

9,18,27,36-Tetrakis[meso-(4-carboxyphenyl)]tetrabenzoporphyrinatozinc(II) (TCPBP, as a sodium salt) was prepared in order to compare its photoinduced electron-transfer behavior toward unsaturated cluster Pd3(dppm)3(CO)(2+) ([Pd3(2+)]; dppm = Ph2PCH2PPh2 as a PF6(-) salt) with that of 5,10,15,20-tetrakis[meso-(4-carboxyphenyl)]porphyrinatozinc(II) (TCPP) in nonluminescent assemblies of the type dye···[Pd3(2+)]x (x = 0-4; dye = TCPP and TCPBP) using femtosecond transient absorption spectroscopy. Binding constants extracted from UV-vis titration methods are the same as those extracted from fluorescence quenching measurements (static model), and both indicate that the TCPBP···[Pd3(2+)]x assemblies (K14 = 36000 M(-1)) are slightly more stable than those for TCPP···[Pd3(2+)]x (K14 = 27000 M(-1)). Density functional theory computations (B3LYP) corroborate this finding because the average ionic Pd···O distance is shorter in the TCPBP···[Pd3(2+)] assembly compared to that for TCPP···[Pd3(2+)]. Despite the difference in the binding constants and excited-state driving forces for the photoinduced electron transfer in dye*···[Pd3(2+)] → dye(•+)···[Pd3(•+)], the time scale for this process is ultrafast in both cases (<85 fs). The time scales for the back electron transfers (dye(•+)···[Pd3(•+)] → dye···[Pd3(2+)]) occurring in the various observed species (dye···[Pd3(2+)]x; x = 0-4) are the same for both series of assemblies. It is concluded that the structural modification on going from porphyrin to tetrabenzoporphyrin does not greatly affect the kinetic behavior in these processes.

An Overview of the Experiments Performed at the BFS Facilities and Evaluated for the International Reactor Physics Experiment Evaluation Project

In total, eight evaluations with 27 critical configurations spanning 11 series of assemblies conducted at the BFS-1 and BFS-2 facilities [BFS: Bol’shoy Fizicheskiy Stand (in transcription from Russian: Big Physical Facility)] are documented in the 2013 edition of the International Handbook of Evaluated Reactor Physics Benchmark Experiments (IRPhEP Handbook). The evaluations concern four scientific issues: physics of sodium-cooled, medium-sized fast reactors; physics of sodium-cooled, small-sized experimental reactors; physics of lead-cooled fast reactors; and integral benchmark data for the mixed oxide (MOX) fuel manufacturing process, particularly low-moderated MOX fissile media. Also, two evaluations with 11 critical configurations spanning two series of assemblies conducted at the BFS-1 facility where many physical parameters in addition to criticality were measured and are documented in the International Handbook of Evaluated Criticality Safety Benchmark Experiments (ICSBEP Handbook). These experiments were designed to obtain data that are applicable to a wide range of criticality safety operations involving fissile contaminated waste streams. This paper provides an overview of the BFS experiments presented in the IRPhEP and ICSBEP Handbooks.

Design of Triads for Probing the Direct Through Space Energy Transfers in Closely Spaced Assemblies

Using a selective stepwise Suzuki cross-coupling reaction, two trimers built on three different chromophores were prepared. These trimers exhibit a D(^)A1-A2 structure where the donor D (octa-β-alkyl zinc(II)porphyrin either as diethylhexamethyl, 10a, or tetraethyltetramethyl, 10b, derivatives) through space transfers the S1 energy to two different acceptors, di(4-ethylbenzene) zinc(II)porphyrin (A1; acceptor 1) placed cofacial with D, and the corresponding free base (A2; acceptor 2), which is meso-meso-linked with A1. This structure design allows for the possibility of comparing two series of assemblies, 9a,b (D(^)A1) with 10a,b (D(^)Â1-A2), for the evaluation of the S1 energy transfer for the global process D*→A2 in the trimers. From the comparison of the decays of the fluorescence of D, the rates for through space energy transfer, kET for 10a,b (kET ≈ 6.4 × 10(9) (10a), 5.9 × 10(9) s(-1) (10b)), and those for the corresponding cofacial D(^)A1 systems, 9a,b, (kET ≈ 5.0 × 10(9) (9a), 4.7 × 10(9) s(-1) (9b)), provide an estimate for kET for the direct through space D*→A2 process (i.e., kET(D(^)A1-A2) - kET(D(^)A1) = kET(D*→A2) ∼ 1 × 10(9) s(-1)). This channel of relaxation represents ∼15% of kET for D*→A1.

Surface-Enhanced Raman Scattering from Synergistic Contribution of Metal and Semiconductor in TiO2/MBA/Ag(Au) and Ag(Au)/MBA/TiO2 Assemblies

Traditional metal SERS-active substrate (Ag or Au) and novel semiconductor SERS-active substrate (TiO2) are combined into the composite system for their synergetic contribution to SERS. A series of assemblies with 4-mercaptobenzoic acid (4-MBA) molecule, TiO2, and/or Ag (Au) nanoparticles (NPs) have been fabricated by a self-assembly method. In the sandwich-structure assemblies (TiO2/MBA/Ag(Au) and Ag(Au)/MBA/TiO2), the SERS signals of 4-MBA molecule exhibit obvious difference in not only the intensity but also Raman frequency as compared with that SERS enhancement in the TiO2/MBA, which is attributed to the introduce of metals and its interaction/synergistic action with TiO2 NPs. SERS enhancement behaviors of 4-MBA in the sandwich-structure assemblies strongly depend on the natures of metals and 4-MBA molecule, which can result in a influence on the TiO2-to-molecule charge transfer and consequent additional EM field effect. This work would like to be interesting and of considerable value for both theory ...

Cover Picture: Nucleation‐Governed Reversible Self‐Assembly of an Organic Semiconductor at Surfaces: Long‐Range Mass Transport Forming Giant Functional Fibers (Adv. Funct. Mater. 18/2007)

AbstractThe cover shows a fluorescence microscopy image of solvent‐vapor annealed (SVA) films of an alkylated perylene‐bis(dicarboximide), reported by Vincenzo Palermo, Klaus Müllen, Paolo Samorì, and co‐workers on p. 3791. Upon exposure to tetrahydrofuran vapors, ultrathin films exhibiting needle‐like structures rearrange into millimeter‐long fibers, which have a sub‐micrometer cross section. The SVA growth was found to be a nucleation‐governed process leading to the formation of birefringent fibers on various substrates. (The result was obtained in the framework of the ESF‐EUROCORES‐SONS2‐SUPRAMATES project.)The use of solvent‐vapor annealing (SVA) to form millimeter‐long crystalline fibers, having a sub‐micrometer cross section, on various solid substrates is described. Thin films of a perylene‐bis(dicarboximide) (PDI) derivative, with branched alkyl chains, prepared from solution exhibit hundreds of nanometer‐sized PDI needles. Upon exposure to the vapors of a chosen solvent, tetrahydrofuran (THF), the needles re‐organize into long fibers that have a remarkably high aspect ratio, exceeding 103. Time‐ and space‐resolved mapping with optical microscopy allows the self‐assembly mechanism to be unravelled; the mechanism is found to be a nucleation‐governed growth, which complies with an Avrami‐type of mechanism. SVA is found to lead to self‐assembly featuring i) long‐range order (up to the millimeter scale), ii) reversible characteristics, as demonstrated through a series of assembly and disassembly steps, obtained by cycling between THF and CHCl3 as solvents, iii) remarkably high mass transport because the PDI molecular motion is found to occur at least over hundreds of micrometers. Such a detailed understanding of the growth process is fundamental to control the formation of self‐assembled architectures with pre‐programmed structures and physical properties. The versatility of the SVA approach is proved by its successful application using different substrates and solvents. Kelvin probe force microscopy reveals that the highly regular and thermodynamically stable fibers of PDI obtained by SVA exhibit a greater electron‐accepting character than the smaller needles of the drop‐cast films. The giant fibers can be grown in situ in the gap between microscopic electrodes supported on SiOx, paving the way towards the application of SVA in micro‐ and nanoelectronics.

Nucleation‐Governed Reversible Self‐Assembly of an Organic Semiconductor at Surfaces: Long‐Range Mass Transport Forming Giant Functional Fibers

AbstractThe use of solvent‐vapor annealing (SVA) to form millimeter‐long crystalline fibers, having a sub‐micrometer cross section, on various solid substrates is described. Thin films of a perylene‐bis(dicarboximide) (PDI) derivative, with branched alkyl chains, prepared from solution exhibit hundreds of nanometer‐sized PDI needles. Upon exposure to the vapors of a chosen solvent, tetrahydrofuran (THF), the needles re‐organize into long fibers that have a remarkably high aspect ratio, exceeding 103. Time‐ and space‐resolved mapping with optical microscopy allows the self‐assembly mechanism to be unravelled; the mechanism is found to be a nucleation‐governed growth, which complies with an Avrami‐type of mechanism. SVA is found to lead to self‐assembly featuring i) long‐range order (up to the millimeter scale), ii) reversible characteristics, as demonstrated through a series of assembly and disassembly steps, obtained by cycling between THF and CHCl3 as solvents, iii) remarkably high mass transport because the PDI molecular motion is found to occur at least over hundreds of micrometers. Such a detailed understanding of the growth process is fundamental to control the formation of self‐assembled architectures with pre‐programmed structures and physical properties. The versatility of the SVA approach is proved by its successful application using different substrates and solvents. Kelvin probe force microscopy reveals that the highly regular and thermodynamically stable fibers of PDI obtained by SVA exhibit a greater electron‐accepting character than the smaller needles of the drop‐cast films. The giant fibers can be grown in situ in the gap between microscopic electrodes supported on SiOx, paving the way towards the application of SVA in micro‐ and nanoelectronics.

Transduction of Analytical Signals by Supramolecular Assemblies of Amphiphiles Containing Heterogeneously Distributed Fluorophores.

We report on the development and characterization of supramolecular assemblies of amphiphiles which are able to transduce changes of pH into optical signals. A series of assemblies have been investigated, including vesicular bilayer lipid membranes, monolayer films of fatty acids or phospholipids at the air-water interface, and covalently immobilized alkylsilane monolayers. In all cases, these membrane assemblies were formed from mixtures of species having zwitterionic and ionizable headgroups. In addition, a small amount of the fluorescently labeled phospholipid nitrobenzoxadiazole phosphatidylethanolamine (1 - 3%) was incorporated into the membranes. This resulted in systems which were able to transduce alterations of pH into changes in fluorescence intensity. Investigations into the physical mechanism responsible for alterations of fluorescence intensity from such membranes suggested that the nitro-benzoxadiazole phosphatidylethanolamine (NBD-PE) signal was based on changes of self-quenching of the probe which occurred when the physical and electrostatic characteristics of the membranes were altered. Useful signals were obtained only when microscopic phase separation existed within the membranes, indicating that careful design of the membrane was required to optimize the signal generated.

Evapotranspiration of herbaceous mimosa (Mimosa strigillosa), a new drought-resistant species in the southeastern United States

Abstract Herbaceous mimosa (Mimosa strigillosa Torr and Gray) is a new reclamation species currently under a series of assembly and evaluation programs by the Natural Resources Conservation Service's Plant Materials Center and Stephen F. Austin State University at Nacogdoches, Texas. Two floating lysimeters were designed and installed at the Stephen F. Austin Experimental Forest, about 20 km south of Nacogdoches, Texas to study differences in evapotranspiration (ET) between the mimosa and bare ground in July–October 1993. Pan coefficients during the study period ranged from 0.40 to 0.58, and no irrigation was applied to the lysimeters in the study. Water losses to the air in area covered by herbaceous mimosa were compatible with other turfgrasses under optimum soil moisture conditions. However, under environmental stress, average daily ET for the mimosa in four summer months was 1.6 mm/day, a value only 0.4 mm/day greater than bare ground. These results agree with a previous study that the plant is a water conservation species capable of tolerating severe drought conditions.

Venezuela: from doctrine to dialogue to participation in the processes of regional development.

The growing toward decentralization and democratization of development planning in Venezuela was discussed. Venezuela has a long tradition of rule by a strong centralized authority. Currently the Office of the President is vested with considerable power despite the existence of an elected legislator and an independent judiciary. The president rules by decree. State legislatures are elected but governors of the states are appointed by the president. There are also elected municipal councils. Both state and municipal governments are almost fully dependent on the federal government for both their operating and capital investment budgets. Development programs are administered through 2 systems. Specific programs are administered by almost 100 different institutes and enterprises. The activities of these various programs are coordinated by administrative bodies at the state and federal level. The 2nd administrative system operates at the regional and federal levels. The administrative body at the federal level is the Central Office for Coordination and Planning and was established by Presidential Decree in 1958. This body prepares and coordinates all national development plans. The administrative bodies at the regional level are the Regional Organizations for Development. These bodies were created in specific regions through a series of legislative acts commencing in 1969 and continuing into the present. The development of these regional bodies represented a 1st step toward decentralization. Decree 478 promulgated in 1980 further promoted the decentalization of developmental planning. The decree established a series of assemblies and councils at various levels. A National Council of Regional Development was created at the federal level and a Regional Council of Development was established at the regional level. At the state level an Assembly of Participation was organized and at the municipal level a Committee of Citizen Participation was established. Neighborhood associations were mentioned in the decree but their role was not formalized. This series of newly established bodies plays a role in both advisory and administrative processes. The advisory process begins at the lowest level and local concerns are expressed upward through the hierarchy. The administrative process flows in the opposite direction. Participation remains highly formalized and is restricted to the participation of recognized leaders and organizations. For example members of the Assembly of Participation include the state governor representatives of municipal councils and representatives of various industrial and commercial organizations. Despite the formal nature of the participation the 1980 Decree clearly exhibited the trend toward decentralization predicted by John Freeman in his analysis of Venezuelan political structure and published in a book entitled "venezuela: From doctrine to Dialogue." Increased pressure will now be exerted for broader community participation in the development process and eventually development planning will focus on the equitable distribution of development benefits rather than on the maximization of economic growth.

Outer Space, Prospects for Man and Society. Edited by Lincoln P. Bloomfield. The American Assembly Series, Englewood Cliffs: Spectrum Book, Prentice-Hall Inc., 1962. Pp. ix, 203 ($ 1.95).

Outer Space, Prospects for Man and Society. Edited by Lincoln P. Bloomfield. The American Assembly Series, Englewood Cliffs: Spectrum Book, Prentice-Hall Inc., 1962. Pp. ix, 203 ($ 1.95).