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- Groenhof, Gerrit, et al.
(författare)
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Photoactivation of the photoactive yellow protein : why photon absorption triggers a trans-to-cis Isomerization of the chromophore in the protein.
- 2004
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 126:13, s. 4228-4233
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Tidskriftsartikel (refereegranskat)abstract
- Atomistic QM/MM simulations have been carried out on the complete photocycle of Photoactive Yellow Protein, a bacterial photoreceptor, in which blue light triggers isomerization of a covalently bound chromophore. The "chemical role" of the protein cavity in the control of the photoisomerization step has been elucidated. Isomerization is facilitated due to preferential electrostatic stabilization of the chromophore's excited state by the guanidium group of Arg52, located just above the negatively charged chromophore ring. In vacuo isomerization does not occur. Isomerization of the double bond is enhanced relative to isomerization of a single bond due to the steric interactions between the phenyl ring of the chromophore and the side chains of Arg52 and Phe62. In the isomerized configuration (ground-state cis), a proton transfer from Glu46 to the chromophore is far more probable than in the initial configuration (ground-state trans). It is this proton transfer that initiates the conformational changes within the protein, which are believed to lead to signaling.
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- Saint-Martin, Humberto, et al.
(författare)
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An application of flexible constraints in Monte Carlo simulations of the isobaric-isothermal ensemble of liquid water and ice Ih with the polarizable and flexible mobile charge densities in harmonic oscillators model
- 2004
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 120:23, s. 11133-11143
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Tidskriftsartikel (refereegranskat)abstract
- The method of flexible constraints was implemented in a Monte Carlo code to perform numerical simulations of liquid water and ice Ih in the constant number of molecules, volume, and temperature and constant pressure, instead of volume ensembles, using the polarizable and flexible mobile charge densities in harmonic oscillators (MCDHO) model. The structural and energetic results for the liquid at T=298 K and rho=997 kg m(-3) were in good agreement with those obtained from molecular dynamics. The density obtained at P=1 atm with flexible constraints, rho=1008 kg m(-3), was slightly lower than with the classical sampling of the intramolecular vibrations, rho=1010 kg m(-3). The comparison of the structures and energies found for water hexamers and for ice Ih with six standard empirical models to those obtained with MCDHO, show this latter to perform better in describing water far from ambient conditions: the MCDHO minimum lattice energy, density, and lattice constants were in good agreement with experiment. The average angle HOH of the water molecule in ice was predicted to be slightly larger than in the liquid, yet 1.2% smaller than the experimental value.
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- Vogel, J, et al.
(författare)
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Complete 5 ' and 3 ' end maturation of group II intron-containing tRNA precursors
- 2001
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Ingår i: RNA-A PUBLICATION OF THE RNA SOCIETY. - : CAMBRIDGE UNIV PRESS. - 1355-8382. ; 7:2, s. 285-292
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Tidskriftsartikel (refereegranskat)abstract
- Higher plant chloroplasts provide the only experimentally validated example of functional tRNA genes that are disrupted by group II introns, Here, precursor transcripts for tRNA(Gly)(UCC), tRNA(Val)(UAC), and tRNA(Ala)(UGC) were investigated for processin
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