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Crystalline Metal‐Peptide Networks: Structures, Applications, and Future Outlook
No full textMetal-peptide networks (MPNs), which are assembled from short peptides and metal ions, are considered one of the most fascinating metal-organic coordinated architectures because of their unique and complicated structures. Although MPNs have considerable potential for development into versatile materials, they have not been developed for practical applications because of several underlying limitations, such as designability, stability, and modifiability. In this review, we summarise several important milestones in the development of crystalline MPNs and thoroughly analyse their structural features, such as peptide sequence designs, coordination geometries, cross-linking types, and network topologies. In addition, potential applications such as gas adsorption, guest encapsulation, and chiral recognition are introduced. We believe that this review is a useful survey that can provide insights into the development of new MPNs with more sophisticated structures and novel functions.
Self‐Assembly of a β‐Peptide Foldamer: The Role of the Surfactant in Three‐Dimensional Shape Selection
No full textThe effect of a small ionic surfactant, cetyltrimethylammonium bromide (CTAB), on the self-assembly of a beta-peptide has been systematically studied by using scanning electron microscopy, X-ray diffraction, selected area electron diffraction, and molecular dynamics (MD) simulations. The latter study suggested that the formation of asymmetric microcrystals may be due to the preferential adsorption of CTAB on {011} and (001) crystal faces. This work provides a plausible rationale for the characteristic 3D morphogenesis of foldectures and elucidates the interaction between the surfactant and organic building block molecules.
Spontaneous Nanobelt Formation by Self‐Assembly of β‐Benzyl GABA
No full textWe present the formation of a nanobelt by self-assembly of beta-benzyl GABA (gamma-aminobutyric acid). This simple gamma-amino acid building block self-assembled to form a well-defined nanobelt in chloroform. The nanobelt showed distinct optical properties due to pi-pi interactions. This new-generation self-assembled single amino acid may serve as a template for functional nanomaterials.
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
베타-펩타이드 폴대머의 자기조립 조절을 통한 3차원 분자 아키텍쳐 합성에 관한 연구
No full text학위논문(박사) - 한국과학기술원 : 화학과, 2013.8
,[xv, 115 p. :]Molecular self-assembly of organic compounds by multiple noncovalent interactions is recognized as a promising bottom-up method to construct nanoscale materials. In particular, self-assembly of peptide scaffolds has been significantly investigated in order to understand the principle of protein folding and underlying mechanism of self-association of natural counterparts. Functional diversity and inherent biocompatibility of peptides afford a myriad of opportunities for the novel design of versatile nanomaterials. However, most of the precedent studies on self-assembly of natural peptides have displayed limited supramolecular morphologies such as tubes, fibers, sheets, and spheres. And intrinsic conformational flexibility of peptides often makes the assembly process complicated and elusive on a practical level. To extend the diversity of the three-dimensional shapes of self-assembled structures without any incidental complications, one should be able to establish a set of assembling components that can be directly linked to the su-pramolecular morphologies by governing parameters of self-assembly.
This dissertation treats the unusual and unprecedented three-dimensional molecular architectures by the self-assembly of non-natural -peptide foldamers. Homo-oligomers of trans-2-aminocyclopentanecarboxylic acid (trans-ACPC) well-known for the stable 12-helical secondary conformations and predictable intermolecular interactions were used as the building blocks of self-assembly. In the aqueous solution of nonionic surfactant pluronic P123, trans-ACPC heptamer and hexamer self-assembled into micron-sized unprecedented structures such as windmills, petals, square rods, and tooth shapes with very uniform shape and size distributions. And the supramolecular morphologies were readily controlled by the regulation of surfactant micelles. Surfactant micelles are considered to recognize the functional anisotropy of trans-ACPC oligomers to enhance or suppress the growth of specific facets. The mechanisms of self-assembly were suggested based on the observed supramolecular shape evolutions. Powder X-ray diffraction patterns and thermal properties of the assemblages were analyzed to verify the molecular arrangements inside the assembled structures. In case of the tooth-shaped assembly of trans-ACPC hexamer, it was revealed that four individual helical monomers constitute a superhelix in a unit cell of the assembly, similar to that found in the supercoiled structure of collagen. In addition, other types of shape evolution in self-assembled structures were observed by adjusting the assembling parameters. A number of polyhedral shapes such as square pyramids, rhombic dodecahedrons, and cuboids were obtained by the self-assembly of trans-ACPC hexamer and heptamer in a presence of ionic surfactant CTAB. These are the first examples of peptide self-assembly which exhibit finite and well-defined three-dimensional supramolecular structures with highly controllable features. The obtained unique three-dimensional molecular architectures were named “foldecture” as a compound of “foldamer” and “architecture”.
Interestingly, a series of self-assembled structures of -peptides were aligned in specific orientations by the external strong magnetic field to facilitate the hierarchical organization. The origin of magnetic alignment is thought to be torque generation from the diamagnetic anisotropy in crystal structures. Highly ordered organization of well-defined self-assembled structures of -peptide foldamers not only provides an insight for the higher-order structures found in natural proteins but is expected to be employed to create the anisotropic surfaces for a wide variety of potential applications.
A very short trans-ACPC tetramer with insufficient helical propensity self-assembled into well-defined microtubes with rectangular cross-section on surface by the evaporation-induced self-assembly (EISA) process. Conformational instability and heterogeneity of trans-ACPC tetramer in solution state were identified by 2D NMR and circular dichroism analyses. Surprisingly, single crystal X-ray diffraction and PXRD analyses revealed that the molecular arrangements in crystal and in the tubular assembly were essentially identical. In case of trans-ACPC hexamer, unusual hollow parallelopiped-shaped self-assembled structures were obtained by EISA process. Distinct pseudopolymorphism in the assembled structure and chiral expression at the supramolecular level were observed. Self-assembly of the analogues of trans-ACPC hexamer revealed the effect of terminal groups on the three-dimensional supramolecular morphology. Formation mechanisms of tubular assemblies of trans-ACPC tetramer and hexamer were suggested based on diffusion-limited mass transport.
This dissertation, which is about the novel self-assembly phenomena of unnatural -peptides, is ex-pected to contribute to the development of artificial functional complexes and diverse applications in biological and material science.한국과학기술원 :화학과
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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