| 1. |
- Bao, Q. X., et al.
(författare)
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Hydrogen adsorption on Ti containing organometallic structures grafted on silsesquioxanes
- 2010
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Ingår i: Structural Chemistry. - : Springer Science and Business Media LLC. - 1040-0400 .- 1572-9001. ; 21:5, s. 1111-1116
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of hydrogen molecule on a novel structure of Ti containing organometallic complexes grafted on silsequioxanes (SQ, H8Si8O12) was investigated by means of DFT method. The hydrogen adsorption properties of the complex structures TiRH7Si8O12 (R = C4H3, C5H4, C6H5) keep almost the same as that of corresponding Ti containing organometallic complexes. Moreover, these complex structures can avoid the problem of transition metal clustering which is a disadvantage for hydrogen adsorption. The maximum number of hydrogen molecules adsorbed was still determined by 18 electron rule, that is to say 5, 4, and 4 H-2 molecules for TiRH7Si8O12 with R = C4H3, C5H4, and C6H5, respectively. At the same time, all the average binding energy of H-2 is located in 0.2-1.0 eV, which is an advantage for hydrogen storage at ambient conditions. Therefore, the materials studied here may provide some enlightenment for developing new types of hydrogen storage materials.
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| 2. |
- Chakraborty, Jishnunil, et al.
(författare)
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Synthesis, crystal, and molecular structure of coordination polymers constructed by self-assembly of NiN4 cores with 2,2 '-iminodibenzoate and nitroprusside ions
- 2007
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Ingår i: Structural Chemistry. - : Springer Science and Business Media LLC. - 1040-0400 .- 1572-9001. ; 18:2, s. 157-164
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Tidskriftsartikel (refereegranskat)abstract
- Two coordination compounds of compositions [Ni(L-1)(idba)(H2O)]center dot 1.5 H2O (1) and [Ni(L-2)Fe(CN)(5)NO]. C2H5OH (2) where L-1 is N, N-bis(3-aminopropyl)ethylenediamine, L-2 is 2,12-dimethyl-3,7,11,17-tetraazabicyclo [11.3.1]heptadeca-1(17),2,11,13,15-pentaene, and idba(2)- is 2,2'-iminodibenzoate have been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis, and single-crystal X-ray diffraction. Complex I crystallizes in the monoclinic space group P2(1)/n (No. 14) with a = 9.810(2) angstrom, b = 10.230(2) angstrom, c = 25.350(5) angstrom, V = 2543.6(9) angstrom(3), Z = 4, and R = 0.0727. The nickel atom is six-coordinated by four N atoms of amine and two 0 atoms of water and idba2-. The molecular packing of the complex comprises of an infinite one-dimensional layered network in which the molecules in the crystal are held together by a system of hydrogen bonding. Complex 2, however, crystallizes in the space group C2/c (No. 15) of the monoclinic system with a = 19.7990(4) angstrom, b = 14.9440(3) angstrom, c = 19.8800(3) angstrom, V = 5115.90(17) angstrom(3), Z = 4, and R = 0.0540. The Ni ion in compound 2 has a slightly distorted octahedral arrangement of the N-4 donor atoms of primary ligand L-2 and two N-donor atoms of the secondary nitroprusside ligand. The structure of 2 displays an extended one-dimensional network formed by linear [-Ni-NC-Fe-CN-] units. A cyclic voltammetric study shows that compound 1 undergoes a quasireversible oxidation attributable to Ni2+ -> Ni3+ in the range 300-420 mV vs SCE.
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| 3. |
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| 4. |
- Larsson, Marcus, et al.
(författare)
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Reversible clustering of sodium channels at the spike is driven by a local crystallization/melting transition around bilayer rafts
- 2012
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Ingår i: Structural Chemistry. - : Springer Science and Business Media LLC. - 1040-0400 .- 1572-9001. ; 23:4, s. 1053-1055
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Tidskriftsartikel (refereegranskat)abstract
- The classical theory of nerve signal conduction, introduced half a century ago by Hodgkin and Huxley, was challenged in 2005 by the so called soliton theory introduced by Heimburg and Jackson. This latter theory is based on a bilayer phase transition forming a mechanical wave, involving a transition from a disordered conformation of the bilayer into the gel-state, and the electric pulse is regarded a result of the phase transition. We support the phase transition concept, and provide evidence for a reversible clustering process at the spike. This clustering involves cholesterol-rich rafts, where the voltage-gated sodium channels are located of the sodium channels at the spike region. The clustering is driven by local crystallization into the gel-type of bilayer conformation around the rafts, and is explained by the hexagonal chain organization in the gel-phase related to that in the raft structure. The clustering is reversed at the melting transition, and the role of the action potential in these phase transition is finally considered.
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| 5. |
- Liljas, Anders
(författare)
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Labor pains in the early days of the Nobel Committee for Chemistry
- 2017
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Ingår i: Structural Chemistry. - : Springer Science and Business Media LLC. - 1040-0400 .- 1572-9001. ; 28:2, s. 555-561
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Tidskriftsartikel (refereegranskat)abstract
- Human activities have been marred for ages by conflicts of interest. This is no less true in the field of science. In the early years of the Nobel Prizes, little attention was focused on this aspect, but awareness steadily grew. In particular, this concerned Swedes nominated for Nobel Prizes, who were most likely themselves members of the Royal Swedish Academy of Sciences, but whose fellows at the Academy should treat them equally with respect to foreign nominees. In addition, conflicts of interest can arise when committee members have close contacts with nominated scientists, regardless of nationality.
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| 6. |
- Lu, Tian, et al.
(författare)
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Wavefunction and reactivity study of benzo[a]pyrene diol epoxide and its enantiomeric forms
- 2014
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Ingår i: Structural Chemistry. - : Springer Science and Business Media LLC. - 1040-0400 .- 1572-9001. ; 25:5, s. 1521-1533
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Tidskriftsartikel (refereegranskat)abstract
- Benzo[a]pyrene is a known carcinogen, which derives from fossil fuel combustion, cigarette smoke, and generic biomass combustion including traffic emissions. This potent carcinogen has a well-known mechanism of action, leading to the formation of adducts with the DNA, primarily at guanosine positions. The reactivity and chemistry of this notorious compound are, however, dependent on the electronic configuration of the biologically activated metabolite, the benzo[a]pyrene diol epoxide. The activated metabolite exists mainly as four isomers, which have particular chemical reactivities toward guanosine sites on the DNA. These isomers exert also a different carcinogenicity compared to one another, which is a feature that is conventionally attributed to their geometry. However, the reactivity and properties of the isomers are not fully defined, and a determination of these properties by wavefunction behavior is required. This study reports the electronic properties of the benzo[a]pyrene diol epoxide enantiomers, along with a detailed analysis of the energy landscape, geometry, and electronic configuration of the epoxide ring. The results show that the epoxide ring, the core of the reactivity, bears different properties at the level of wavefunction for each isomer. Each of the isomers has a distinct profile on the epoxide ring, in terms of hydrogen bonds and in terms of the non-covalent interaction between the diol groups and the epoxide. These profiles generate differential reactivities of epoxide group, which can be attributed to its local bond lengths, the electron localization function, and polarized bonds. Most interestingly, the quantum chemical calculations showed also that the epoxide ring is inclined more perpendicularly toward the angular ring plane for the more carcinogenic isomers, a feature which suggests a potential geometrical relationship between the inclination of the epoxide group and its interaction with the guanosine group upon adduct formation. Our results introduce novel and crucial information, which assist in understanding the mechanism of toxic potential of this known molecule, and display the strength and level of detail of applying quantum chemical methods to reveal the reactivity, energy properties, and electronic properties of a mutagen.
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| 7. |
- Manzetti, Sergio
(författare)
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Quantum chemical calculations of the active site of the solute-binding protein PsaA from Streptococcus pneumoniae explain electronic selectivity of metal binding
- 2018
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Ingår i: Structural Chemistry. - : Springer Science and Business Media LLC. - 1040-0400 .- 1572-9001. ; 29:2, s. 393-401
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Tidskriftsartikel (refereegranskat)abstract
- Streptococcus pneumoniae is the world’s foremost bacterial pathogen. Virulence in the host is dependent on manganese acquisition via the PsaBCA permease. Crystallographic studies of its solute-binding protein component, PsaA, have previously shown that the nature of the metal ion bound by the protein modulates the conformational changes associated with its function. Notably, manganese and cadmium ions can be bound in a reversible manner, facilitating transport via PsaA, whereas zinc binds in an essentially irreversible manner preventing release to the permease. All three ionic species show a similar coordination in the PsaA crystal structures. A set of quantum chemical calculations have here been performed in order to differentiate between the ions in terms of electronic configuration. Based on natural bond orbital (NBO) analysis, the results show that manganese and cadmium bind more strongly to the protein than zinc, in that their coordination to the enzyme involves more shared electrons. Manganese has the highest indirect indicator of bonding strength and provides an unpaired electron that induces the formation of three bonds to the enzyme active site. Cadmium binds more strongly than zinc, though more weakly than manganese, and forms only ionic bonds in its ligand framework. These calculations indicate a concrete differentiation of the bonding states of the three active sites; however, bonding energies which can give more accurate estimates have not been computed presently. The calculations further show that the ionic radii are critical for the bonding state between the enzyme and the metal and that the conformational motions responsible for the PsaA’s functional cycle may depend on the ion binding strongly to the enzyme. Our results add important information of the PsaA-metal ion binding architecture to the existing crystallography data and aid in understanding the function of this protein.
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| 8. |
- Shaikh, M, et al.
(författare)
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Synthesis and NMR elucidation of homoisoflavanone analogues
- 2011
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Ingår i: Structural Chemistry. - : Springer Science and Business Media LLC. - 1040-0400 .- 1572-9001. ; 22:1, s. 161-166
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Tidskriftsartikel (refereegranskat)abstract
- A series of five homoisoflavanone analogues have been synthesized from the corresponding 3,5-methoxy phenols via chroman-4-one in three steps. The complete NMR elucidation of these homoisoflavanone analogues is reported. The use of 2D NMR techniques (COSY, NOESY, HSQC and HMBC) proved to be very useful tools in the elucidation of homoisoflavanone analogues. The homoisoflavanone analogues exhibit an AA'BB' spin pattern in the ring B of the homoisoflavanone. These homoisoflavanone analogues are potential antifungal and anti-inflammatory agents.
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| 9. |
- Sokka, Ilia, et al.
(författare)
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One-dimensional chloro-bridged Cd(II) chains separated by dimethyl hexadecyl sulfonium cation layers : synthesis and structure
- 2008
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Ingår i: Structural Chemistry. - : Springer Science and Business Media LLC. - 1040-0400 .- 1572-9001. ; 19:1, s. 51-55
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Tidskriftsartikel (refereegranskat)abstract
- A low-dimensional material with the composition {(n-C16H33)(CH3)(2)S}(infinity)(+1)[CdCl3](-) has been prepared. As expected, the sulfonium cations form an insulating organic layer; the closest Cd-Cd distance between layers is about 19 angstrom, as compared to 3.9 angstrom within the same layer. The inorganic layer is formed by a 5-coordinated cadmium(II) moiety CdCl5, connected to a one-dimensional chain of slightly distorted, edge-sharing square pyramids. The compound was synthesized from the parent sulfonium chloride and CdCl2 in ethanol, exploiting the Lewis acidity of Cd(II).
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| 10. |
- Tamulis, A., et al.
(författare)
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Quantum mechanical studies of intensity in electronic spectra of fluorescein dianion and monoanion forms
- 2003
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Ingår i: Structural Chemistry. - 1040-0400 .- 1572-9001. ; 14:6, s. 643-648
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Tidskriftsartikel (refereegranskat)abstract
- Quantum chemical ab initio investigations with full geometrical optimizations of dianion and monoanion fluorescein molecules in the ground state were performed by applying the density functional theory (DFT) B3PW91/6-311G** model to clarify the difference in the geometrical and electronic structure of the dianion molecule and that of monoanion in influencing fluorescence. The mechanism of fluorescence of dianion and monoanion is explained and the reason for intensive fluorescence of dianion compared with that of monoanion is studied.
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| 11. |
- Olsson, Erik J, et al.
(författare)
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On the Role of the Research Agenda in Epistemic Change
- 2006
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Ingår i: Erkenntnis. - : Springer Science and Business Media LLC. - 1572-8420 .- 0165-0106. ; 65:2, s. 165-183
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Tidskriftsartikel (refereegranskat)abstract
- The standard way of representing an epistemic state in formal philosophy is in terms of a set of sentences, corresponding to the agent's beliefs, and an ordering of those sentences, reflecting how well entrenched they are in the agent's epistemic state. We argue that this wide-spread representational view-a view that we identify as a "Quinean dogma" - is incapable of making certain crucial distinctions. We propose, as a remedy, that any adequate representation of epistemic states must also include the agent's research agenda, i.e., the list of question that are open or closed at any given point in time. If the argument of the paper is sound, a person's questions and practical interests, on the one hand, and her beliefs and theoretical values, on the other, are more tightly interwoven than has previously been assumed to be the case in formal epistemology.
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| 12. |
- Kozlov, Vladimir, 1954-, et al.
(författare)
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Heat content asymptotics for Riemannian manifolds with Zaremba boundary conditions
- 2007
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Ingår i: Potential Analysis. - : Springer Science and Business Media LLC. - 0926-2601 .- 1572-929X. ; 26:3, s. 225-254
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Tidskriftsartikel (refereegranskat)abstract
- The existence of a full asymptotic expansion for the heat content asymptotics of an operator of Laplace type with classical Zaremba boundary conditions on a smooth manifold is established. The first three coefficients in this asymptotic expansion are determined in terms of geometric invariants, partial information is obtained about the fourth coefficient.
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