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1.
Sylvie Baltora-Rosset Danielle Marty François-Yves Dupradeau Emmanuel Pauthe Véronique Larreta-Garde Gilles Gacel Jean-Pierre Monti 《International journal of peptide research and therapeutics》1997,4(4-6):391-395
Summary The conformations of thermolysin synthetic substrates in H2O/D2O (9/1) and glycerol-d
5 (5 M) are investigated using two-dimensional nuclear magnetic resonance spectroscopy and molecular modeling. The structures
obtained from molecular modeling and NMR studies are compared. Comparisons of these structures with bound inhibitor in the
active site of thermolysin are also discussed. 相似文献
2.
《BBA》2019,1860(10):148059
Based on characterization by X-ray absorption spectroscopy, it has been proposed that the Mn4CaO5 cluster in the crystal structure of the water-oxidizing enzyme, photosystem II (PSII), may represent an over-reduced form arising from reduction by the X-ray beam. Using a quantum mechanical/molecular mechanical approach, and assuming that all of the μ-oxo bridges are deprotonated in S1, we analyzed the reduction process of the Mn4CaO5 cluster. In the crystal structure, the O atom (O5), which is linked with three Mn atoms and one Ca atom, has no H-bond. When reduced to S–2, unexpectedly, a water molecule at Ca2+ (W3) reoriented itself, formed a H-bond with O5, and released a proton to O5, resulting in formation of OH− at both W3 and O5. Once generated, the OH− group at O5 was stable, because the W3…O5 H-bond had already disappeared. A weak binding of H2O at Ca2+ led W3 to reorient and serve as a proton donor to O5 upon over-reduction. 相似文献
3.
Gerda Urbach William Stark Akio Nobuhara 《Bioscience, biotechnology, and biochemistry》2013,77(7):1217-1228
Mass spectra of the δ-lactones of the following 5-hydroxy-2-enoic acids were determined: 5-hydroxyhex-2-enoic acid (I), 5-hydroxyoct-2-enoic acid (II), 5-hydroxydec-2-enoic acid (III), 5-hydroxydodec-2-enoic acid (IV), 5-hydroxy-8-methylnon-2-enoic acid (V), 5-hydroxy-6-ethyloct-2-enoic acid (VI), 5-hydroxy-5, 6, 6-trimethylhept-2-enoic acid (VII), and 5-hydroxy-5-methylnon-2-enoic acid (VIII). The following modes of fragmentation are consistent with observed m/e values, metastable peaks, and established modes of breakdown in compounds containing similar atomic groupings:—1. Loss of side chain, resulting in ions at m/e 97 for I-VI and at m/e 111 and 153 for VII and VIII (diagnostic peaks); 2. 1,4-Rupture of the ring giving an ion at m/e 68 (diagnostic peak) which loses CO to give m/e 40; 3. Loss of CO from m/e 97 fragment to give m/e 69 which breaks down further to m/e 41→m/e 39; 4. 1, 4-Rupture of m/e 111 and m/e 153 fragments to give m/e 43 and 85, further breakdown of m/e 85→57→41→39; 5. Loss of H2O from the molecular ion providing there is a hydrogen atom on C5 and the side chain is at least 3 carbon atoms in length, further loss of H2O when the side chain is equal to C5 or C7; 6. Loss of CO2 from the molecular ion of I, IV-VIII; 7. Loss of CO from all molecular ions; 8. Loss of 2×28 from the molecular ions of III, IV, V, VI; 9. Loss of (18 + 28) from the molecular ion of III, IV, V, VI; 10. Loss of 60 from the molecular ion of II, III, IV, V, VI; 11. Formation of M + 1 ion (169) of VII and VIII; 12. Formation of M + 1 ion (143) of saturated δ-octalactone and loss of H2O from this M + 1 ion. 相似文献
4.
《Biophysical journal》2022,121(7):1289-1298
Get3/4/5 chaperone complex is responsible for targeting C-terminal tail-anchored membrane proteins to the endoplasmic reticulum. Despite the availability of several crystal structures of independent proteins and partial structures of subcomplexes, different models of oligomeric states and structural organization have been proposed for the protein complexes involved. Here, using native mass spectrometry (Native-MS), coupled with intact dissociation, we show that Get4/5 exclusively forms a tetramer using both Get5/5 and a novel Get4/4 dimerization interface. Addition of Get3 to this leads to a hexameric (Get3)2-(Get4)2-(Get5)2 complex with closed-ring cyclic architecture. We further validate our claims through molecular modeling and mutational abrogation of the proposed interfaces. Native-MS has become a principal tool to determine the state of oligomeric organization of proteins. The work demonstrates that for multiprotein complexes, native-MS, coupled with molecular modeling and mutational perturbation, can provide an alternative route to render a detailed view of both the oligomeric states as well as the molecular interfaces involved. This is especially useful for large multiprotein complexes with large unstructured domains that make it recalcitrant to conventional structure determination approaches. 相似文献
5.
Tibor G. Szanto Szabolcs Gaal Izhar Karbat Zoltan Varga Eitan Reuveny Gyorgy Panyi 《The Journal of general physiology》2021,153(6)
It has been reported earlier that the slow (C-type) inactivated conformation in Kv channels is stabilized by a multipoint hydrogen-bond network behind the selectivity filter. Furthermore, MD simulations revealed that structural water molecules are also involved in the formation of this network locking the selectivity filter in its inactive conformation. We found that the application of an extracellular, but not intracellular, solution based on heavy water (D2O) dramatically slowed entry into the slow inactivated state in Shaker-IR mutants (T449A, T449A/I470A, and T449K/I470C, displaying a wide range of inactivation kinetics), consistent with the proposed effect of the dynamics of structural water molecules on the conformational stability of the selectivity filter. Alternative hypotheses capable of explaining the observed effects of D2O were examined. Increased viscosity of the external solution mimicked by the addition of glycerol had a negligible effect on the rate of inactivation. In addition, the inactivation time constants of K+ currents in the outward and the inward directions in asymmetric solutions were not affected by a H2O/D2O exchange, negating an indirect effect of D2O on the rate of K+ rehydration. The elimination of the nonspecific effects of D2O on our macroscopic current measurements supports the hypothesis that the rate of structural water exchange at the region behind the selectivity filter determines the rate of slow inactivation, as proposed by molecular modeling. 相似文献
6.
Benaki Dimitra C. Paxinou Eugenia Magafa Vassiliki Pairas George N. Manessi-Zoupa Evy Cordopatis Paul A. Mikros Emmanuel 《International journal of peptide research and therapeutics》2001,8(2):77-87
Summary The nonapeptide Leuprorelin, one of the LHRH agonists, was studied by means of 2D nuclear magnetic resonance spectroscopy
and molecular modeling. NOESY spectra in aqueous/deuterated methanol solution (50% H2O/CD3OD) at low temperature (268 K) revealed short-range nOe connectivities (i, i+1), characteristic of flexibility of the molecule.
The H
N
-H
N
sequential connectivities observed provide evidence that the sequence has the propensity to form a bend involving residues
5 and 6 and the N-terminal segment. The α-proton chemical shifts compared to random coil and additional data from the amide
proton temperature coefficients support this assumption. One long-range nOe cross peak between H
2
α
-H
NEth
is indicative of proximity between C- and N-termini. 相似文献
7.
The tetrapeptide Boc-Trp-(N-Me)Nle-Asp-Phe-NH2 is a potent CCK-B agonist. Replacement in this analogue of the norleucine residue by a phenylalanine, to yield Boc-Trp-(N-Me)Phe-Asp-Phe-NH2, led to a 740-fold decrease in affinity whereas the same decrease in affinity was not observed in their nonmethylated counterparts. In order to ascertain the conformational preferences of these two N-methylated tetrapeptides, a study by two-dimensional (2D) nmr spectroscopy and molecular modeling was undertaken. The solution conformation of the two peptides was examined by 1H-nmr in a d6-DMSO/H2O (80 : 20) mixture. A cis-trans equilibrium, induced by N-methylation, was observed for both analogues, and the proton spectra of the two retamers were fully characterized in each case. 1H-1H distance constraints, derived from 2D nuclear Overhauser effect spectroscopy and rotating frame nuclear Overhauser effect spectroscopy experiments, were used as inputs for subsequent restrained molecular dynamics simulations. Comparisons of the nmr and molecular modeling data point toward distinct conformational preferences for these two peptides with an opposite spatial orientation of the Trp residue, and could explain the large difference in their biological activities. Furthermore, the tridimensional structure of Boc-Trp-(N-Me)Nle-Asp-Phe-NH2 could serve as a model for the design of nonpeptide CCK-B agonists. © 1994 John Wiley & Sons, Inc. 相似文献
8.
Recent ab initio studies reported in the literature have challenged the mechanistic assignments made on the basis of volume of activation data [1,2]. In addition to that ab initio molecular orbital calculations on hydrated zinc(II)-ions were used to elucidate the general role of this ion in metalloproteins [3]. Due to our interest in both inorganic reaction mechanisms and enzymatic catalysis we started a systematic investigation of solvent exchange processes on divalent zinc-ion using density functional calculations. Our investigations cover aqua complexes of the general form [Zn(H2O)n]2+·mH20 with n=3-6 and m=0-2, where n and m represent the number of water molecules in the coordination and solvation sphere, respectively.The complexes [Zn(H2O)5]2+·2H2O and [Zn(H2O)4]2+·2H2O turnend out to be the most stable zinc complexes with seven and six water molecules, respectively. This implies that a heptacoordinated zinc(II) complex, where all water molecules are located in the co-ordination sphere, should be energetically highly unfavorable and that [Zn(H2O)6]2+ can quite readily push two coordinated water molecules into the solvation sphere. For the pentaqua complex [Zn(H2O)5]2+ only one water molecule is easily lost to the solvation sphere, which makes the [Zn(H2O)4]2+·H2O complex the most favorable in order to consider the limiting dissociative and associative water exchange process of hexacoordinated zinc(II). The dehydration and hydration energies using the most stable zinc(II) complexes [Zn(H2O)4]2+·2H2O, [Zn(H2O)5]2+·2H2O and [Zn(H2O)4]2+·H2O were calculated to be 24.1 and -21.0 kcal/mol, respectively. 相似文献
9.
R. Vijayalakshmi V. Subramanian Balachandran Unni Nair 《Journal of biomolecular structure & dynamics》2013,31(6):1063-1071
Abstract Molecular modeling and energy minimisation calculations have been used to investigate the interaction of chromium(III) complexes in different ligand environments with various sequences of B-DNA. The complexes are [Cr(salen)(H2O)2]+; salen denotes 1, 2 bis-salicylideneaminoethane, [Cr(salprn)(H2O)2]+; salprn denotes 1, 3 bis- salicylideneamino-propane, [Cr(phen)3]3+; phen denotes 1, 10 phenanthroline and [Cr(en)3]3+; en denotes eth- ylenediamine. All the chromium(III) complexes are interacted with the minor groove and major groove of d(AT)12, d(CGCGAATTCGCG)2 and d(GC)12 sequences of DNA. The binding energy and hydrogen bond parameters of DNA-Cr complex adduct in both the groove have been determined using molecular mechanics approach. The binding energy and formation of hydrogen bonds between chromium(III) complex and DNA has shown that all complexes of chromium(III) prefer minor groove interaction as the favourable binding mode. 相似文献
10.
Sumanta Kumar Padhi 《Inorganica chimica acta》2011,372(1):383-388
Compounds of the molecular formulae, [LH3](NO3)3 (1), [Fe(LH)2](PF6)4·5H2O (2), [Fe(L)2][Fe(L)(LH)](PF6)5·H2O (3), [Fe(L)2][Fe(L)(LH)](BF4)5·2H2O (4) and [Fe(L)2](Cr2O7)·6H2O (5) have been synthesized using 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine (L). The molecular structures of all the compounds were determined. The Fe(II) complexes are high spin in nature at room temperature and upon cooling a gradual spin-transition is observed. Among 1-5, hydrogen-bonding, π···π, and anion···π interactions as well as water tetramer and pentamer are present in the molecular packing. 相似文献
11.
Rupam Sarma 《Inorganica chimica acta》2011,377(1):50-55
A 1D-coordination polymer [{Mn3(C6H5COO)6(BPNO)2(MeOH)2}(MeOH)2]n (1) having benzoate as the anionic ligand and 4,4′-bipyridyl-N,N′-dioxide (BPNO) as bridging ligand is synthesized by reacting benzoic acid with manganese(II) acetate tetrahydrate followed by reaction with 4,4′-bipyridyl-N N′-dioxide. The bridging bidentate BPNO ligands in this coordination polymer along with the benzoate bridges hold the repeated units. The chain like structure in one dimension by benzoate bridges are connected to each other through the μ3-η2:η1 bridges of BPNO ligands. This coordination polymer can be transformed to a molecular complex [Mn(H2O)6](C6H5COO)2.4BPNO (2). In this complex the BPNO remains outside the coordination sphere but they are hydrogen bonded to water molecules to form self assembled structure. The reaction of 3,5-pyrazoledicarboxylic acid (L1H2) and BPNO with manganese(II) acetate or zinc(II) acetate led to molecular complexes with composition [M2(L1)2(H2O)6].BPNO·xH2O {where M = Mn(II) (3), Zn(II)(4)}. These molecular complexes of BPNO are characterised by X-ray crystallography. The complexes 3-4 are binuclear carboxylate complexes having M2O2 core formed from carboxylate ligands with two metal ions. 相似文献
12.
Bing‐Jie Ni Zhiguo Yuan Kartik Chandran Peter A. Vanrolleghem Sudhir Murthy 《Biotechnology and bioengineering》2013,110(1):153-163
There is increasing evidence showing that ammonia‐oxidizing bacteria (AOB) are major contributors to N2O emissions from wastewater treatment plants (WWTPs). Although the fundamental metabolic pathways for N2O production by AOB are now coming to light, the mechanisms responsible for N2O production by AOB in WWTP are not fully understood. Mathematical modeling provides a means for testing hypotheses related to mechanisms and triggers for N2O emissions in WWTP, and can then also become a tool to support the development of mitigation strategies. This study examined the ability of four mathematical model structures to describe two distinct mechanisms of N2O production by AOB. The production mechanisms evaluated are (1) N2O as the final product of nitrifier denitrification with NO as the terminal electron acceptor and (2) N2O as a byproduct of incomplete oxidation of hydroxylamine (NH2OH) to NO. The four models were compared based on their ability to predict N2O dynamics observed in three mixed culture studies. Short‐term batch experimental data were employed to examine model assumptions related to the effects of (1) NH concentration variations, (2) dissolved oxygen (DO) variations, (3) NO accumulations and (4) NH2OH as an externally provided substrate. The modeling results demonstrate that all these models can generally describe the NH, NO, and NO data. However, none of these models were able to reproduce all measured N2O data. The results suggest that both the denitrification and NH2OH pathways may be involved in N2O production and could be kinetically linked by a competition for intracellular reducing equivalents. A unified model capturing both mechanisms and their potential interactions needs to be developed with consideration of physiological complexity. Biotechnol. Bioeng. 2013; 110: 153–163. © 2012 Wiley Periodicals, Inc. 相似文献
13.
《Inorganica chimica acta》1988,147(2):265-274
Trifunctional dialkyl [1,2-bis(diethylcarbamoyl)- ethyl] phosphonates, (RO)2P(O)CH[C(O)N(C2H5)2]- [CH2C(O)N(C2H5)2] R CH3, C2H5, i-C3H7, n-C6H13 were prepared from the respective sodium salts, Na[(RO)2P(O)CHC(O)N(C2H5)2] and N,N- diethylchloroacetamide, and they were characterized by elemental analysis, mass, infrared and NMR spectroscopy. The molecular structure of (i-C3H7O)2- P(O)CH[C(O)N(C2H5)2][CH2C(O)N(C2H5)2] was determined by single crystal X-ray diffraction analysis and found to crystallize in the monoclinic space group P21/c with a=15.589(6), b=9.783(4), c= 16.283(7) Å, β = 110.90(3)°, Z = 4 and V= 2320(2) Å3. The structure was solved by direct methods and blocked least-squares refinement converged with Rf = 5.7% and RwF= 4.4% on 2266 unique data with F>4σ(F). Important bond distances include PO 1.459(3) Å, CHCO 1.228(3) Å and CHCH2CO 1.223(3) Å. The coordination chemistry of the ligand with several lanthanides was examined, and the structure of the complex Gd(NO3)3{[(i-C3H7O)2P(O)CH[C(O)N(C2H5)2][CH2C(O)N(C2H5)2]}2·H2O was determined. The complex crystallized in the monoclinic space group P21/n with a = 13.524(5), b = 22.033(4), c = 19.604(4) Å β = 106.22(2)°, Z = 4 and V= 5609(3) Å3. The structure was solved by heavy atom techniques and blocked least-squares refinement converged with RF = 5.9% and RwF = 4.1% on 5275 reflections with F > 4σ(F). Both trifunctional ligands were found to bond to Gd(III) through only the phosphoryl oxygen atoms. The remainder of the Gd coordination sphere was composed of three bidentate nitrate oxygen atoms and an oxygen bonded water molecule. Several important bond distances include GdO(phosphoryl)av = 2.343(5) Å, GdO(nitrate)av = 2.475(7) Å, GdO(water) = 2.354(5) Å, PO(phosphoryl)av = 1.467(6) Å, CHCOav = 1.242(10) Å and CHCH2COav = 1.209(11) Å. 相似文献
14.
The pH dependency of N‐converting enzymatic processes,pathways and microbes: effect on net N2O production
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Yunjie Ma Borja Valverde‐Pérez Carlos Domingo‐Félez Marlene Mark Jensen Barth F. Smets 《Environmental microbiology》2018,20(5):1623-1640
Nitrous oxide (N2O) is emitted during microbiological nitrogen (N) conversion processes, when N2O production exceeds N2O consumption. The magnitude of N2O production vs. consumption varies with pH and controlling net N2O production might be feasible by choice of system pH. This article reviews how pH affects enzymes, pathways and microorganisms that are involved in N‐conversions in water engineering applications. At a molecular level, pH affects activity of cofactors and structural elements of relevant enzymes by protonation or deprotonation of amino acid residues or solvent ligands, thus causing steric changes in catalytic sites or proton/electron transfer routes that alter the enzymes' overall activity. Augmenting molecular information with, e.g., nitritation or denitrification rates yields explanations of changes in net N2O production with pH. Ammonia oxidizing bacteria are of highest relevance for N2O production, while heterotrophic denitrifiers are relevant for N2O consumption at pH > 7.5. Net N2O production in N‐cycling water engineering systems is predicted to display a ‘bell‐shaped’ curve in the range of pH 6.0–9.0 with a maximum at pH 7.0–7.5. Net N2O production at acidic pH is dominated by N2O production, whereas N2O consumption can outweigh production at alkaline pH. Thus, pH 8.0 may be a favourable pH set‐point for water treatment applications regarding net N2O production. 相似文献
15.
Amin Ahmed Ouameur Philippe Bourassa Heidar-Ali Tajmir-Riahi 《RNA (New York, N.Y.)》2010,16(10):1968-1979
Biogenic polyamines are found to modulate protein synthesis at different levels. This effect may be explained by the ability of polyamines to bind and influence the secondary structure of tRNA, mRNA, and rRNA. We report the interaction between tRNA and the three biogenic polyamines putrescine, spermidine, spermine, and cobalt(III)hexamine at physiological conditions, using FTIR spectroscopy, capillary electrophoresis, and molecular modeling. The results indicated that tRNA was stabilized at low biogenic polyamine concentration, as a consequence of polyamine interaction with the backbone phosphate group. The main tRNA reactive sites for biogenic polyamine at low concentration were guanine-N7/O6, uracil-O2/O4, adenine-N3, and 2′OH of the ribose. At high polyamine concentration, the interaction involves guanine-N7/O6, adenine-N7, uracil-O2 reactive sites, and the backbone phosphate group. The participation of the polycation primary amino group, in the interaction and the presence of the hydrophobic contact, are also shown. The binding affinity of biogenic polyamine to tRNA molecule was in the order of spermine > spermidine > putrescine with KSpm = 8.7 × 105 M−1, KSpd = 6.1 × 105 M−1, and KPut = 1.0 × 105 M−1, which correlates with their positively charged amino group content. Hill analysis showed positive cooperativity for the biogenic polyamines and negative cooperativity for cobalt-hexamine. Cobalt(III)hexamine contains high- and low-affinity sites in tRNA with K1 = 3.2 × 105 M−1 and K2 = 1.7 × 105 M−1, that have been attributed to the interactions with guanine-N7 sites and the backbone PO2 group, respectively. This mechanism of tRNA binding could explain the condensation phenomenon observed at high Co(III) content, as previously shown in the Co(III)–DNA complexes. 相似文献
16.
Lucia Squarcialupi Marco Betti Daniela Catarzi Flavia Varano Matteo Falsini Annalisa Ravani 《Journal of enzyme inhibition and medicinal chemistry》2017,32(1):248-263
New 7-amino-2-phenylpyrazolo[4,3-d]pyrimidine derivatives, substituted at the 5-position with aryl(alkyl)amino- and 4-substituted-piperazin-1-yl- moieties, were synthesized with the aim of targeting human (h) adenosine A1 and/or A2A receptor subtypes. On the whole, the novel derivatives 1–24 shared scarce or no affinities for the off-target hA2B and hA3 ARs. The 5-(4-hydroxyphenethylamino)- derivative 12 showed both good affinity (Ki =?150?nM) and the best selectivity for the hA2A AR while the 5-benzylamino-substituted 5 displayed the best combined hA2A (Ki =?123?nM) and A1 AR affinity (Ki =?25?nM). The 5-phenethylamino moiety (compound 6) achieved nanomolar affinity (Ki =?11?nM) and good selectivity for the hA1 AR. The 5-(N4-substituted-piperazin-1-yl) derivatives 15–24 bind the hA1 AR subtype with affinities falling in the high nanomolar range. A structure-based molecular modeling study was conducted to rationalize the experimental binding data from a molecular point of view using both molecular docking studies and Interaction Energy Fingerprints (IEFs) analysis. 相似文献
17.
Dimitra C. Benaki Eugenia Paxinou Vassiliki Magafa George N. Pairas Evy Manessi-Zoupa Paul A. Cordopatis Emmanuel Mikros 《Letters in Peptide Science》2001,8(2):77-87
The nonapeptide Leuprorelin, one of the LHRH agonists, was studied by means of 2D nuclear magnetic resonance spectroscopy and molecular modeling. NOESY spectra in aqueous/deuterated methanol solution (50%H2O/CD3OD) at low temperature (268 K) revealed short-range nOe connectivities (i, i+1), characteristic of flexibility of the molecule. The HN–HN sequential connectivities observed provide evidence that the sequence has the propensity to form a bend involving residues 5 and 6 and the N-terminal segment. The -proton chemical shifts compared to random coil and additional data from the amide proton temperature coefficients support this assumption. One long-range nOe cross peak between H2
–HNEth is indicative of proximity between C- and N-termini. 相似文献
18.
Emission analysis of Tb3+‐and Sm3+‐ion‐doped (Li2O/Na2O/K2O) and (Li2O + Na2O/Li2O + K2O/K2O + Na2O)‐modified borosilicate glasses
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B. Naveen Kumar Reddy S. Sailaja K. Thyagarajan Young Dahl Jho B. Sudhakar Reddy 《Luminescence》2018,33(3):486-494
Four series of borosilicate glasses modified by alkali oxides and doped with Tb3+ and Sm3+ ions were prepared using the conventional melt quenching technique, with the chemical composition 74.5B2O3 + 10SiO2 + 5MgO + R + 0.5(Tb2O3/Sm2O3) [where R = 10(Li2O /Na2O/K2O) for series A and C, and R = 5(Li2O + Na2O/Li2O + K2O/K2O + Na2O) for series B and D]. The X‐ray diffraction (XRD) patterns of all the prepared glasses indicate their amorphous nature. The spectroscopic properties of the prepared glasses were studied by optical absorption analysis, photoluminescence excitation (PLE) and photoluminescence (PL) analysis. A green emission corresponding to the 5D4 → 7F5 (543 nm) transition of the Tb3+ ions was registered under excitation at 379 nm for series A and B glasses. The emission spectra of the Sm3+ ions with the series C and D glasses showed strong reddish‐orange emission at 600 nm (4G5/2 →6H7/2) with an excitation wavelength λexci = 404 nm (6H5/2→4F7/2). Furthermore, the change in the luminescence intensity with the addition of an alkali oxide and combinations of these alkali oxides to borosilicate glasses doped with Tb3+ and Sm3+ ions was studied to optimize the potential alkali‐oxide‐modified borosilicate glass. 相似文献
19.
Nur Syafiqah Abdul Ghani Roghayeh Abedi Karjiban Mahiran Basri Nur Hana Faujan Wui Zhuan Lim 《International journal of peptide research and therapeutics》2017,23(3):393-407
Alzheimer’s disease (AD) is a neurodegenerative disorder caused by overproduction and accumulation of amyloid beta-peptide (Aβ). The hallmarks associated with this AD are the presence of Aβ plaques between the nerve cell in the brain which leading to synaptic loss in memory. The amyloid plaques contain of transition metals like zinc, copper and iron. In a healthy brain, the metal ions are present in balance concentration. High concentrations of Zn are normally released during neurotransmission process. The release of Zn might cause the aggregation of Aβ leading to AD. Amyloid-β1–42 is the main type of Aβ in amyloid plaque. There still have limited explanation on how Aβ1–42 interaction with Zn metal, as well as the effect of Zn metal on the Aβ structure in different solvents in atomic detail. Therefore, we investigated the structural changes of Aβ1–42 in water (Aβ-H2O) and the mixed hexafluoroisopropanol (HFIP) with water (Aβ-HFIP/H2O). The mixed solvent consisted of hexafluoroisopropanol (HFIP) and water was used with the ratio of HFIP:H2O (80:20). The effect of zinc ion was also examined for the interaction of Aβ peptide with zinc in water (Aβ-Zn-H2O) and mixed solvent (Aβ-Zn-HFIP/H2O) using all atom level molecular dynamics (MD) calculations for 1 μs. We found that Aβ-Zn-HFIP/H2O contained more α-helix compared to Aβ-HFIP/H2O while Aβ-H2O and Aβ-Zn-H2O produced well-dissolved structure and they contained more β-sheets. β-turns are possible to bind with the receptor proteins and may induce the aggregation process in AD. Thus, Aβ-H2O and Aβ-Zn-H2O have higher possibility leading to AD compared to Aβ-Zn-HFIP/H2O and Aβ-HFIP/H2O models. 相似文献
20.
《Inorganica chimica acta》1986,125(3):135-142
The electrochemical behavior of μ-oxo-N,N-bis- (5-(o-phenyl)-10,15,20-triphenylporphinatoiron(III))- urea mono hydrate, [(FF)Fe]20, was investigated at a platinum electrode in both 1,2-dichloroethane and pyridine. In EtCl2, electroreduction of this oxo-bridged and urea-linked dimer produced a binuclear ferrous hydroxide porphyrin. This latter species could be oxidized to regenerate the μ-oxo dimer in quantitative yield. In pyridine, [(FF)Fe]2O underwent a chemically irreversible electroreduction producing a hexacoordinate binuclear ferrous porphyrin with pyridine occupying the axial positions of each iron atom. Oxidation of this species also produced the μ-oxo and urea-linked dimer in quantitative yield. These results are in contrast to the redox behavior of [(TPP)Fe]2O in these solvents. Electron transfer pathways, consistent with voltammetric and spectroelectrochemical results, are proposed for [(FF)Fe]2O and compared with those found for [(TPP)Fe]2O. The redox behavior observed for [(FF)Fe]2O implicates the steric constraint of the urea linkage and hydrogen bonding of the protonated bridging oxygen atom with the amide groups. This marks the first evidence of molecular environmental effects in the redox chemistry of hematin dimers. 相似文献