84 research outputs found
Exploring the coupling between electron transfer and protein dynamics in photosynthetic reaction centers embedded into dehydrated amorphous matrices
No full textThe interplay between protein dynamics and electron transfer (ET)
has been extensively investigated in the bacterial photosynthetic reaction
center (RC) from Rhodobacter sphaeroides by hampering RC internal
motions at low temperatures [1]. Alternatively, the RC dynamics can
be inhibited at room temperature by incorporating the RC into
dehydrated trehalose matrices [2]. In the glasses the recombination
kinetics of the charge separated state P+QA
are accelerated and
distributed in rate as compared to solution, mimicking at room
temperature the effects observed at 10 K in water-glycerol. This is
taken to indicate inhibition of the RC relaxation from the dark- to the
light-adapted conformation, as well as of the RC thermal fluctuations
[1,2]. We proposed that the inhibition is mediated by residual water
molecules of the RC hydration shell which bridge protein surface
groups with trehalose molecules of the matrix by forming a network
of multiple hydrogen bonds [3]. Consistently, similar effects have
been observed also in RC films dehydrated in the absence of sugar [4].
However, striking differences are found between RC-trehalose glasses
and RC-films: (a) The thermal stability of the RC is tremendously
enhanced in the trehalose matrix. (b) In RC-trehalose matrices, the
P+QA
recombination after a few seconds of continuous photoexcitation
is only partially decelerated as compared to the one recorded
after a laser flash, whereas in dried RC films a comparable period of
continuous illumination leads to a total recovery of the kinetics
observed in the hydrated system. These data indicate that in films the
protein dynamics can be easily regained, in contrast to trehalose
glasses, which reveal much stronger structural constraints. We are
extending these studies to a series of RC mutants characterized by
a widely altered P+/P midpoint potential relative to wild-type [5].
In these mutants, the acceleration of P+QA
recombination induced
by cooling to 10 K in the dark decreased with increasing midpoint
potential [6]. Interestingly, incorporation into dehydrated trehalose
matrices causes instead acceleration of the kinetics by the same factor
for all P+/P midpoint potential values
Static and dynamic aspects of DNA charge transfer: a theoretical perspective
No full textIn this work, we approach the impact of dynamic and static disorder on DNA charge transfer from a theoretical and numerical perspective. Disordered or defect geometries are either realized via molecular dynamics simulations using a classical force field or by experimentally determined DNA bulge structures. We apply a chemically specific, atomically resolved extended Su-Schrieffer-Heeger model to compute the energy parameters relevant to DNA charge transfer. For both models studied here, the effective donor-acceptor couplings-and hence the charge transfer rates-significantly depend upon the geometry. Dynamic disorder leads to a correlation time in this quantity of the order of 30 fs, and the transfer rates universally exhibit a broad, yet well-defined, exponential distribution. For DNA bulges, the angle characterizing the defect controls the charge transfer efficiency. The results are discussed and extensively compared to experimental findings and other calculations
Molecular dynamics of ultrathin supported polysulfone films studied by dielectric spectroscopy
No full textGlassy dynamics of ultra-thin supported polysufone layers as studied by dielectric spectroscopy
No full text
Glass transition of ultrathin supported polysulfone films studied by dielectric spectroscopy
No full textDie H+-ATPase aus Chloroplasten: Die Kinetik der mit einem Protonentransport gekoppelten ATP-Synthese auf einem Bindungsplatz (The H+-ATPase from chloroplasts: the kinetics of proton coupled ATPsynthesis at one nucloetide binding site)
No full textAspects of Somali Literature in European Languages
No full textThe author analyses some aspects of Somali literature written directy or later translated into European languages.Qoraagu wuxuu wax ka baarayaa suugaanta soomaaliyeed ee si tooska ah loo qoray ama marka dambe loo tarjumay afafka reer galbeed.L'autore analizza alcuni aspetti della letteratura somala scritta direttamente o poi tradotta nelle diverse lingue europee.Thomas Labahn (ed.
Dance and Society in Nineteenth Century Mogadishu
No full textIn this paper, the author attempts to extend existing researches to a preliminary discussion of dance in 19th century Mogadishu.Qoruhu wuxuu maqaalkan ku sii ballaarinayaa cilmibaaris horey loogu sameeyay Muqdisho qarnigii XIX oo ku saabsan ciyaar dhaqameed.In questo lavoro, l'autore tenta di estendere le ricerche esistenti a osservazioni preliminari sulla danza nella Mogadiscio del XIX secolo.Thomas Labahn (ed.
The Influence of Quinone Structure on Quinone Binding to the QA Site in Bacterial Reaction Centers from Rhodobacter Sphaeroides
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