Effects of Cavities in the Bacterial Reaction Center

A site-specific double mutant of Rhodobacter capsulatus, in which the large aromatic residues M208Tyr and L181Phe in the interior of the photosynthetic reaction center (RC) complex were replaced by smaller theonine residues, showed a dramatic reduction in the number of assembled complexes and was incapable of photosynthetic growth. The cavity created by the smaller side chains interferes mostly with the assembly of the complex. Phenotypic revertants were recovered in which a spontaneous second-site mutation restored photocompetence in the presence of the original site-specific mutations. In these strains, an Ala to Pro substitution in neighboring transmembrane helix (at M271) resulted in an increased yield of RC complexes. To test the hypothesis that the original phenotype was due to a cavity, other mutants were constructed where L180Phe and M207Leu were replaced with alanines that created similar-sized voids at other positions in the membrane-spanning interior. The L180Ala-M207A mutant had the same phenotype. Coupling of the above proline substitution to these new cavity mutants also resulted in photocompetant strains that carry increased levels of RC complexes. Therefore, the proline substitution at M271 serves as a global suppressor of the phenotype caused by these internal cavities

Waste In-Situ Stabilization/Entombment Research and Development Project

The technical basis and stakeholder acceptance of entombment technology is necessary before entombment becomes a decontamination and decommissioning (D and D) option for nuclear reactors. The authors present a research and development (R and D) approach addressing technical basis and stakeholder acceptance of entombment technology. The approach includes a consortium and the conceptual R and D program

From photons to protons in the photocycle of bacterial reaction center

The detailed knowledge of the atomic coordinates of the bacterial reaction center (RC) has permitted a close scrutiny of structure/function relationships not only of the quinones but of the protein itself with its internal water structure. Protonatable groups were identified as intrinsic part of the redox reactions, providing charge compensation and forming channels for the movement of hydrogen ions to QB2-. The nature and position of these groups give rise to electrostatic profiles that determine the kinetics and energetics of proton transport. Fine tuning or dramatic variations of protein delivery pathways can adapt the photocycle to changes in bulk phase pH value, buffering capacities and primary structure of the RC

The interrelation between temperature regimes and fish size in juvenile Atlantic cod (Gadus morhua): effects on growth and feed conversion efficiency

The present paper describes the growth properties of juvenile Atlantic cod (Gadus morhua) reared at 7, 10, 13 and 16 °C, and a group reared under “temperature steps” i.e. with temperature reduced successively from 16 to 13 and 10 °C. Growth rate and feed conversion efficiency of juvenile Atlantic cod were significantly influenced by the interaction of temperature and fish size. Overall growth was highest in the 13 °C and the T-step groups but for different reasons, as the fish at 13 °C had 10% higher overall feeding intake compared to the T-step group, whereas the T-step had 8% higher feeding efficiency. After termination of the laboratory study the fish were reared in sea pens at ambient conditions for 17 months. The groups performed differently when reared at ambient conditions in the sea as the T-step group was 11.6, 11.5, 5.3 and 7.5% larger than 7, 10, 13 and 16 °C, respectively in June 2005. Optimal temperature for growth and feed conversion efficiency decreased with size, indicating an ontogenetic reduction in optimum temperature for growth with increasing size. The results suggest an optimum temperature for growth of juvenile Atlantic cod in the size range 5–50 g dropping from 14.7 °C for 5–10 g juvenile to 12.4 °C for 40–50 g juvenile. Moreover, a broader parabolic regression curve between growth, feed conversion efficiency and temperature as size increases, indicate increased temperature tolerance with size. The study confirms that juvenile cod exhibits ontogenetic variation in temperature optimum, which might partly explain different spatial distribution of juvenile and adult cod in ocean waters. Our study also indicates a physiological mechanism that might be linked to cod migrations as cod may maximize their feeding efficiency by active thermoregulation

Search for leptophobic Z ' bosons decaying into four-lepton final states in proton-proton collisions at root s=8 TeV

Peer reviewe

Search for black holes and other new phenomena in high-multiplicity final states in proton-proton collisions at root s=13 TeV

Peer reviewe