Search results for "Helix"
showing 10 items of 196 documents
Mechanical unfolding pathway of a model β-peptide foldamer.
2015
Foldamers constructed from oligomers of β-peptides form stable secondary helix structures already for small chain lengths, which makes them ideal candidates for the investigation of the (un)folding of polypeptides. Here, the results of molecular simulations of the mechanical unfolding of a β-heptapeptide in methanol solvent revealing the detailed unfolding pathway are reported. The unfolding process is shown to proceed via a stable intermediate even for such a small system. This result is arrived at performing non-equilibrium force ramp simulations employing different pulling velocities and also using standard calculations of the potential of mean force, i.e., the free energy as a function …
Field-induced ferromagnetism due to magneto-striction in 1-D helical chains
2016
Two homochiral copper(II) helices, [Cu(μ1,3-N3)(L1)]n (1) and [Cu(μ1,3-NCO)(L2)]n (2), with end-to-end pseudohalide bridges, were synthesized using two N2O donor achiral Schiff bases via spontaneous chiral resolution. Field-induced ferromagnetic ordering due to magneto-striction in homochiral 1-D helix [Cu(μ1,3-N3)(L1)]n (1) is reported for the first time. At temperatures below 5.5 K, under a magnetic field of 1 T, orthogonality between the magnetic orbitals of copper centres increases significantly due to the contraction of lattice parameters, giving rise to long-range ferromagnetic ordering in the helical chain. The magneto-dielectric results are also indicative of the observed magneto-st…
Ferrochirality: a simple theoretical model of interacting, dynamically invertible, helical polymers, 2. Molecular field approach: supports and the de…
1995
Using a molecular field approach, the effect of interaction between reversibly invertible, helical polymers is investigated theoretically. The helices are modelled by nearest-neighbour statistical thermodynamics. If the interaction energy between two helices of common handedness is lower than that of oppositely handed ones, a critical temperature Tc exists, below which the system spontaneously must leave the racemic state, though there is no contact to any chiral centre or force. This is analogous to the second-order phase transition of ferromagnets. The critical point increases with molecular weight and optical persistence of the helices. At the critical point the system is highly sensitiv…
Solution NMR structure of aD,L-alternating oligonorleucine as a model of ?-helix
2001
beta-Helix structures are of particular interest due to their capacity to form transmembrane channels with different transport properties. However, the relatively large number of beta-helices configurations does not allow a direct conformational analysis of beta-helical oligopeptides. A synthetic alternating D,L-oligopeptide with twelve norleucines (XIIMe) has been used as a model to get insight in the conformational features of beta-helix structures. The spatial configuration of XIIMe in solution has been determined by NMR. An extensive set of distances (nuclear Overhauser effect) and dihedral (J coupling constants) constraints have been included in molecular dynamics calculations. The NMR…
Predictive modeling of aryl hydrocarbon receptor (AhR) agonism
2020
Abstract The aryl hydrocarbon receptor (AhR) plays a key role in the regulation of gene expression in metabolic machinery and detoxification systems. In the recent years, this receptor has attracted interest as a therapeutic target for immunological, oncogenic and inflammatory conditions. In the present report, in silico and in vitro approaches were combined to study the activation of the AhR. To this end, a large database of chemical compounds with known AhR agonistic activity was employed to build 5 classifiers based on the Adaboost (AdB), Gradient Boosting (GB), Random Forest (RF), Multilayer Perceptron (MLP) and Support Vector Machine (SVM) algorithms, respectively. The built classifier…
Copper(II)-Binding Induces a Unique Polyproline Type II Helical Structure within the Ion-Binding Segment in the Intrinsically Disordered F-Domain of …
2019
Reproduction of the dominant vector of Zika and dengue diseases, Aedes aegypti mosquito, is controlled by an active heterodimer complex composed of the 20-hydroxyecdysone receptor (EcR) and ultraspiracle protein. Although A. aegypti EcR shares the structural and functional organization with other nuclear receptors, its C-terminus has an additional long F domain (AaFEcR). Recently, we showed that the full length AaFEcR is intrinsically disordered with the ability to specifically bind divalent metal ions. Here, we describe the details of the exhaustive structural and thermodynamic properties of Zn2+- and Cu2+-complexes with the AaFEcR domain, based on peptide models of its two putative metal …
Revisión taxonómica de Helix zapateri Hidalgo, 1870 (Pulmonata: Trissexodontidae) y su nuevo estatus en la malacofauna ibérica
2008
Alberto Martínez Ortí: alberto.martinez@uv.es Revisión taxonómica de Helix zapateri Hidalgo, 1870 (Pulmonata, Trissexodontidae) y su nuevo estatus en la malacofauna ibérica.— Se realiza la revisión taxonómica y se discute la nueva asignación genérica del taxon ibérico Helix zapateri, mediante la comparación de caracteres conquiológicos con las especies más similares, Hatumia pseudogasulli y Gasullia gasulli, ambas trissexodóntidos. Los estudios conquiológicos nos permiten concluir que Helix zapateri debe ser considerada como una especie válida y designarse como Hatumia zapateri, y que Hatumia pseudogasulli corresponde a un sinónimo posterior de H. zapateri. Taxonomical revision of Helix zap…
A unique example of structural and magnetic diversity in four interconvertible copper(II)-azide complexes with the same schiff base ligand: a monomer…
2010
Four new Cu(II)-azido complexes of formula [CuL(N(3))] (1), [CuL(N(3))](2) (2), [Cu(7)L(2)(N(3))(12)](n) (3), and [Cu(2)L(dmen)(N(3))(3)](n) (4) (dmen = N,N-dimethylethylenediamine) have been synthesized using the same tridentate Schiff base ligand HL (2-[1-(2-dimethylaminoethylimino)ethyl]phenol, the condensation product of dmen and 2-hydroxyacetophenone). The four compounds have been characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. Complex 1 is mononuclear, whereas 2 is a single mu-1,1 azido-bridged dinuclear compound. The polymeric compound 3 possesses a 2D structure in which the Cu(II) ions are linked by phenoxo oxygen atoms and t…
Which regions produce the most innovation policy research?
2022
[EN] This article uses the data indexed in the Web of Science Core Collection and Scopus databases up to and including the year 2020 to map leading regions and trending topics in academic innovation policy research. The country analysis highlights four leading regions in this research field: Western Europe (led by the UK, the Netherlands, Germany, and Spain), North America (led by the USA), Scandinavia (led by Sweden and Denmark), and Asia-Pacific (led by China and Australia). The most common keywords are used to develop a conceptual framework. Applying the Tree of Science approach, we classify the most influential studies into three categories: foundational studies (the roots), structural …
A Research Journey from National Systems of Innovation to National Systems of Entrepreneurship: Introducing the Sextuple Helix
2021
[EN] National systems of innovation (NSI) have attracted substantial interest from public administrations, the scientific community and international organizations. Innovation is a key factor for countries to be competitive in the today's global economy. Entrepreneurship is an innovation source that has gained importance in NSI research over the last few decades. This focus on entrepreneurship in the context of NSI has led scholars to propose novel concepts such as entrepreneurial ecosystems and the national system of entrepreneurship (NSE). This paper uses bibliometric methods and the Web of Science Core Collection (WoS CC) database to explore how entrepreneurship fits into NSI research an…