10 research outputs found
Observations of the thermal environment on Red Sea platform reefs: a heat budget analysis
An investigation of slow charge separation in a tyrosine M210 to tryptophan mutant of the <i>Rhodobacter Sphaeroides</i> reaction center by femtosecond mid-infrared spectroscopy
Energy and electron transfer in a tyrosine M210 to tryptophan (YM210W) mutant of the Rhodobacter sphaeroides reaction center (RC) were investigated through time-resolved visible pump/mid-infrared (mid-IR) probe spectroscopy at room temperature, with the aim to further characterize the primary charge separated states in the RC. This mutant is known to display slow and multi-exponential charge separation, and was used in earlier work to prove the existence of an alternative route for charge separation starting from the accessory bacteriochlorophyll in the active branch,
Initial charge separation in photosystem II reaction centers identified with femtosecond mid-infrared spectroscopy
Ultrafast infrared observation of exciton equilibration from oriented single crystals of photosystem II
This work was supported by the Leverhulme Trust through award RPG-2014-126 and the Biotechnology and Biological Sciences Research Council through award BB/H004238/1. T.R. acknowledges support by the Austrian Science Fund: P24774-N27
Atlantic origin of observed and modelled freshwater anomalies in the Nordic Seas
Between 1965 and 1990, the waters of the Nordic Seas and the subpolar basins of the North Atlantic Ocean freshened substantially1. The Arctic Ocean also became less saline over this time, as a consequence of increasing runoff1, 2, 3, 4, but it is not clear whether flow from the Arctic Ocean was the main source of the Nordic Seas salinity anomaly. As a region of deep-water formation, the Nordic Seas are central to the Atlantic meridional overturning circulation, but this process is inhibited if the surface salinity is too low2. Here we use the instrumental record of Nordic Seas hydrography, along with a global oceanâsea-ice model hindcast simulation, to identify the sources and magnitude of freshwater that has accumulated in the Nordic Seas since 1950. We find that the freshwater anomalies within the Nordic Seas can mostly be explained by less salt entering the southern part of the basin with the relatively saline Atlantic inflow, with seemingly little contribution from the Arctic Ocean. We conclude that hydrographic changes in the Nordic Seas are primarily related to changes in the Atlantic Ocean. We infer that if the Atlantic inflow and Nordic Seas both freshen similarly, this would render the Atlantic meridional overturning circulation relatively insensitive to Nordic Seas freshwater content
Both electronic and vibrational coherences are involved in primary electron transfer in bacterial reaction center
Structure-based modeling of energy transfer in photosynthesis
We provide a minimal model for a structure-based simulation of excitation energy transfer in pigmentâprotein complexes (PPCs). In our treatment, the PPC is assembled from its building blocks. The latter are defined such that electron exchange occurs only within, but not between these units. The variational principle is applied to investigate how the Coulomb interaction between building blocks changes the character of the electronic states of the PPC. In this way, the standard exciton Hamiltonian is obtained from first principles and a hierarchy of calculation schemes for the parameters of this Hamiltonian arises. Possible extensions of this approach are discussed concerning (i) the inclusion of dispersive site energy shifts and (ii) the inclusion of electron exchange between pigments. First results on electron exchange within the special pair of photosystem II of cyanobacteria and higher plants are presented and compared with earlier results on purple bacteria. In the last part of this mini-review, the coupling of electronic and nuclear degrees of freedom is considered. First, the standard excitonâvibrational Hamiltonian is parameterized with the help of a normal mode analysis of the PPC. Second, dynamical theories are discussed that exploit this Hamiltonian in the study of dissipative exciton motion