| 1. |
- Dourado, Daniel F A R, et al.
(författare)
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Glutathione transferase : new model for glutathione activation
- 2008
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 14:31, s. 9591-8
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Tidskriftsartikel (refereegranskat)abstract
- Glutathione transferases are enzymes of the cellular detoxification system that metabolize a vast spectrum of xenobiotic and endobiotic toxic compounds. They are homodimers or heterodimers and each monomer has an active center composed of a G-site in which glutathione (GSH) binds and an H-site for the electrophilic substrate. When GSH binds to the G-site, the pKa value of its thiol group drops by 2.5 units; this promotes its deprotonation and, therefore, produces a strong nucleophilic thiolate that is able to react with the electrophilic substrate. The mechanism behind the deprotonation of the thiol group is still unknown. Some studies point to the fact that the GSH glutamyl alpha-carboxylate group is essential for GSH activation, whereas others indicate the importance of the active-center water molecules. On the basis of QM/MM calculations, we propose a mechanism of GSH activation in which a water molecule, acting as a bridge, is able to assist in the transfer of the proton from the GSH thiol group to the GSH glutamyl alpha-carboxylate group, after an initial GSH conformational rearrangement. We calculated the potential of mean force of this GSH structural rearrangement that would be necessary for the approach of both groups and we then performed a QM/MM ONIOM scan of water-assisted proton transfer. The overall free-energy barrier for the process is consistent with experimental studies of the enzyme kinetics.
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| 2. |
- Edgar, Brian, 1945-, et al.
(författare)
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Obtaining a class of conformally flat pure radiation metrics with cosmological constant using invariant operators
- 2006
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Ingår i: XXVIII Spanish Relativity Meeting E.R.E. A Century of Relativity Physics,2005. - Melville, NY, USA : American Institute of Physics (AIP). - 0735403333 ; , s. 507-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In a recent paper by B. Edgar and M. P. Ramos the method using invariant operators to obtain the type O pure radiation class of metrics was generalized to type N pure radiation solutions. In this work we further generalize the method in determining type O pure radiation metrics with cosmological constant.
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| 3. |
- Edgar, Brian, 1945-, et al.
(författare)
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Obtaining a class of type N pure radiation metrics using invariant operators
- 2005
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Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 22:5, s. 791-802
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Tidskriftsartikel (refereegranskat)abstract
- We develop further the integration procedure in the generalized invariant formalism, and demonstrate its efficiency by obtaining a class of Petrov type N pure radiation metrics without any explicit integration, and with comparatively little detailed calculations. The method is similar to the one exploited by Edgar and Vickers when deriving the general conformally flat pure radiation metric. A major addition to the technique is the introduction of non-intrinsic elements in the generalized invariant formalism, which can be exploited to keep calculations manageable.
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| 4. |
- Edgar, Brian, 1945-, et al.
(författare)
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Obtaining a class of Type O pure radiation metrics with a negative cosmological constant, using invariant operators
- 2007
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Ingår i: General Relativity and Gravitation. - : Springer Science and Business Media LLC. - 0001-7701 .- 1572-9532. ; 39, s. 539-566
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Tidskriftsartikel (refereegranskat)abstract
- Using the generalised invariant formalism we derive a special subclass of conformally flat spacetimes whose Ricci tensor has a pure radiation and a Ricci scalar component. The method used is a development of the methods used earlier for pure radiation spacetimes of Petrov types O and N, respectively. In this paper we demonstrate how to handle, in the generalised invariant formalism, spacetimes with isotropy freedom and rich Killing vector structure. Once the spacetimes have been constructed, it is straightforward to deduce their Karlhede classification: the Karlhede algorithm terminates at the fourth derivative order, and the spacetimes all have one degree of null isotropy and three, four or five Killing vectors.
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| 5. |
- Edgar, Brian, 1945-, et al.
(författare)
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Type O pure radiation metrics with a cosmological constant
- 2007
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Ingår i: General Relativity and Gravitation. - : Springer Science and Business Media LLC. - 0001-7701 .- 1572-9532. ; 39:11, s. 1749-1772
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we complete the integration of the conformally flat pure radiation spacetimes with a non-zero cosmological constant Λ, and τ ≠ 0, by considering the case Λ +ττ ≠ 0. This is a further demonstration of the power and suitability of the generalised invariant formalism (GIF) for spacetimes where only one null direction is picked out by the Riemann tensor. For these spacetimes, the GIF picks out a second null direction (from the second derivative of the Riemann tensor) and once this spinor has been identified the calculations are transferred to the simpler GHP formalism, where the tetrad and metric are determined. The whole class of conformally flat pure radiation spacetimes with a non-zero cosmological constant (those found in this paper, together with those found earlier for the case Λ +ττ = 0) have a rich variety of subclasses with zero, one, two, three, four or five Killing vectors. © 2007 Springer Science+Business Media, LLC.
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| 6. |
- Edgar, Brian, 1945-, et al.
(författare)
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Using the generalised invariant formalism : a class of conformally flat pure radiation metrics with a negative cosmological constant
- 2007
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Ingår i: The Spanish Relativity Meeting ERE 2006: Einsteins Legacy,2006. - : Institute of Physics Publishing (IOPP). ; , s. 012013-
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Konferensbidrag (refereegranskat)abstract
- We demonstrate an integration procedure for the generalised invariant formalism by obtaining a subclass of conformally flat pure radiation spacetimes with a negative cosmological constant. The method used is a development of the methods used earlier for pure radiation spacetimes of Petrov types O and N respectively. This subclass of spacetimes turns out to have one degree of isotropy freedom, so in this paper we have extended the integration procedure for the generalised invariant formalism to spacetimes with isotropy freedom.
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