1,721,060 research outputs found
Early stages of misfolding of PAP248-286 at two different pH values: An insight from molecular dynamics simulations
Full text linkPAP248-286 peptides, which are highly abundant in human semen, aggregate and form amyloid fibrils that enhance HIV infection. Previous experimental studies have shown that the infection-promoting activity of PAP248-286 begins to increase well before amyloid formation takes place and that pH plays a key role in the enhancement of PAP248-286-related infection. Hence, understanding the early stages of misfolding of the PAP2482-86 peptide is crucial. To this end, we have performed 60 independent MD simulations for a total of 24 µs at two different pH values (4.2 and 7.2). Our data shows that early stages of misfolding of the PAP248-286 peptide is a multistage process and that the first step of the process is a transition from an “I-shaped” structure to a “U-shaped” structure. We further observed that the structure of PAP248-286 at the two different pH values shows significantly different features. At pH 4.2, the peptide has less intra-molecular H-bonds and a reduced α-helical content than at pH 7.2. Moreover, differences in intra-peptide residues contacts are also observed at the two pH values. Finally, free energy landscape analysis shows that there are more local minima in the energy surface of the peptide at pH 7.2 than at pH 4.2. Overall, the present study elucidates the early stages of misfolding of the PAP248-286 peptide at the atomic level, thus possibly opening new avenues in structure-based drug discovery against HIV infection
Crystal Structure of the Apo and the ADP-Bound Form of Choline Kinase from Plasmodium falciparum
Full text linkAmong the malaria-causing parasites, the deadliest is Plasmodium falciparum, which accounts for the majority of the fatalities. As the infection progresses inside erythrocytes, major cellular and metabolic changes take place. For its own growth, the parasite relies on the accumulation of phospholipids, which are essential for membrane synthesis. Within the Kennedy pathway, the P. falciparum choline kinase (PfChoK) has a central role in the biosynthesis of phosphatidylcholine and its selective inhibition leads to the parasite arrest and eradication. Here, we report the crystal structure of the apo and the ADP-bound form of choline kinase from Plasmodium falciparum at 2.0 and 2.2 Å resolution, respectively. These new structural data will facilitate the implementation of effective structure-based drug development strategies against PfChoK in the fight against malaria
A new mechanism for the rearrangement of the icosahedral carboranes
No full textA new mechanism which involves the anticubeoctahedron as the complementary geometry is postulated to rationalise previously reported data on the rearrangement of various icosahedral carboranes
Synthesis and characterisation of trifluoro(??5-n-propyltetramethylcyclopentadienyl) metal(IV)-compounds of the elements of group IV
No full textA series of trifluoro metal complexes of titanium, zirconium and hafnium containing the n-propyltetramethylcyclopentadienyl ligand (C(5)Me(4)nPr) have been synthesised by metathesis reactions of the trichloro analogue using three equivalents of Me3SnF. X-ray analysis of (C(5)Me(4)nPr)TiF3 1 confirms the presence of two (C(5)Me(4)nPr)TiF3 moieties with two fluorine atoms bridging the metal atoms resulting in a centre of symmetry. The starting materials (C(5)Me(4)nPr)MCl3 (M=Zr, Hf) were prepared by reaction of (C(5)Me(4)nPr)Li with MCl4 (M=Zr, Hf). (C) 1997 Published by Elsevier Science S.A
Organic‐Soluble Neutral and Ionic Indium Siloxane Cages: Potential Precursors for Indium‐Containing Silicates
No full textN/
Time-Dependent Structure and Solubilization Kinetics of Graphene Oxide in Methanol and Water Dispersions
No full textCarbonaceous materials have long been attracting attention due to their physical and chemical properties as well as their low production costs. Among them, graphene oxide is considered to be an extremely promising material in the context of a wide spectrum of emerging technologies. However, since graphene oxide is charaterized by a variable and therefore elusive chemical composition, complete control on the structure and the reactivity of this complex material has yet to be achieved, which clearly represents a knowledge gap that needs to be closed in order to confidently enable as many future applications as possible. Here, we present a spectroscopic study of graphene oxide obtained via the Sun method showing structural alteration of the material upon utilization of solvents of different polarity. In particular, our data provide clear experimental evidence that the use of methanol results in a graphene oxide material essentially enriched in carbonyl and hydroxyl groups. Moreover, the conjugated character of the material is also influenced by the nature of the solvent. The observed structural changes, which are due to the functionalization of the graphene basal plane, are time-dependent and correspond to different solubility properties of the resulting material. Finally, the modification of the graphene oxide structure alters the rate and the activation energy of solubilization
Synthesis and spectroscopic characterization of a series of substituted cyclopentadienyl Group 4 fluorides; crystal structure of the acetylacetonato complex [(acac) 2 (??-C 5 Me 5 )Zr(??-F)SnMe 3 Cl]
No full textA series of mono- and di-substituted cyclopentadienyl Group 4 fluorides [Ti{eta-C(5)H(3)R(R')-1,3}F-n(m)], (n = m = 2 and n = 1, m = 3; R = H or SiMe(3); R' = H, Me or SiMe(3)), [Ti(eta-C(5)Me(5))(2)F-2] and [Zr(eta-C5H5)(2)F-2] have been-prepared via the reaction of the corresponding chlorides with SnMe(3)F. The compounds have been characterized by means of H-1 and F-19 NMR, IR and mass spectroscopy and chemical analyses. The solvent dependence of the reactions using SnMe,F is discussed. To demonstrate the wide applicability of this fluorinating system the acetylacetonatofluoro complex [(acac)(2)(eta-C(5)Me(5))Zr(eta-F)SnMe(3)Cl] has been prepared and its crystal structure determined
Synthesis and Characterization of (4-Fluorophenyl)amino-Based Amino- and Iminometallanes of Group 13. Crystal Structures of (MeAlNR f ) 4 , (MeMNR f ) 6 ?? n THF (M = Al, n = 2; M = Ga, n = 7), and (MeIn(THF)NR f ) 4 (R f = 4-C 6 H 4 F)
No full textThe novel amino- and iminometallanes (MeAlNR(f))(n) (1) (n = 4, 1a; n = 6, 1b), (Me(2)GaN(H)R(f))(2) (2), (MeGaNR(f))(6) (3), (Me(2)InN(H)R(f))(2) (4), and (MeIn(THF)NR(f))(4) (5) (R(f) = 4-C6(5)H(4)F) have been prepared in high yield by the reaction of AlMe(3), GaMe(3), and InMes(3), respectively, with 4-fluoroaniline. All of the products have been fully characterized by elemental analysis, IR, NMR, and mass spectroscopy. The crystal structures of 1a, 1b . 2THF, 3 . 7THF, and 5 have been determined. For the degree of oligomerization of compound 1 a solvent- and temperature-dependent influence is assumed. (MeGaNR(f))(6) (3) is the first hexameric iminogallane and (MeIn(THF)NR(f))(4) (5) is the second iminoindane described in the literature
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