Protein-Induced Modulation of Chloroplast Membrane Morphology

Organelles are surrounded by membranes with a distinct lipid and protein composition. While it is well established that lipids affect protein functioning and vice versa, it has been only recently suggested that elevated membrane protein concentrations may affect the shape and organization of membranes. We therefore analyzed the effects of high chloroplast envelope protein concentrations on membrane structures using an in vivo approach with protoplasts. Transient expression of outer envelope proteins or protein domains such as CHUP1-TM–GFP, outer envelope protein of 7 kDa–GFP, or outer envelope protein of 24 kDa–GFP at high levels led to the formation of punctate, circular, and tubular membrane protrusions. Expression of inner membrane proteins such as translocase of inner chloroplast membrane 20, isoform II (Tic20-II)–GFP led to membrane protrusions including invaginations. Using increasing amounts of DNA for transfection, we could show that the frequency, size, and intensity of these protrusions increased with protein concentration. The membrane deformations were absent after cycloheximide treatment. Co-expression of CHUP1-TM–Cherry and Tic20-II–GFP led to membrane protrusions of various shapes and sizes including some stromule-like structures, for which several functions have been proposed. Interestingly, some structures seemed to contain both proteins, while others seem to contain one protein exclusively, indicating that outer and inner envelope dynamics might be regulated independently. While it was more difficult to investigate the effects of high expression levels of membrane proteins on mitochondrial membrane shapes using confocal imaging, it was striking that the expression of the outer membrane protein Tom20 led to more elongate mitochondria. We discuss that the effect of protein concentrations on membrane structure is possibly caused by an imbalance in the lipid to protein ratio and may be involved in a signaling pathway regulating membrane biogenesis. Finally, the observed phenomenon provides a valuable experimental approach to investigate the relationship between lipid synthesis and membrane protein expression in future studies

Exploring the Relationship between Social Class and Quality of Life: the Mediating Role of Power and Status

Funder: Universität zu Köln (1017)AbstractWhy does social class affect Quality of Life? We simultaneously investigated two novel possible explanations: Because a high social class is associated with increased control over resources (i.e., power) or because a high social class is associated with higher respect and esteem in the eyes of others (i.e., status). To test these explanations, we collected data from 384 US-based individuals. We measured their social class, power, status, and four facets of Quality of Life (physical, mental, social, and environmental). For each facet, we calculated the correlation with social class. Next, we tested whether the relationship between social class and the specific facet was mediated by power, status, or both. Social class correlated significantly with all facets of Quality of Life (physical, mental, social, and environmental). Using parallel mediation models, we found that this positive relationship was mediated by status, but not by power. For some facets of Quality of Life (physical, environmental), power even had a negative indirect effect. These results suggest that upper-class individuals indeed have a higher Quality of Life. However, this seems to be mostly due to the increased status of upper-class individuals, whereas power was less important or even had detrimental effects on Quality of Life. Researchers and policymakers aiming to address class-based Quality of Life inequality could thus benefit from focusing on status as an important mediator. Moreover, our work demonstrates the importance of considering power and status as distinct constructs, in order to fully unravel the relationship between social class and Quality of Life.</jats:p

Measurements of NH3 and CO2 with distributed-feedback diode lasers near 2.0 µm in bioreactor vent gases

When this research was performed, M. E. Webber, J. B. Jeffries and R. K. Hanson were with the High Temperature Gasdynamics Laboratory, Department of Mechanical Engineering, Stanford University. M. E. Webber is now with Pranalytica, Inc. When this research was performed, R. Claps, F. V. Englich, and F. K. Tittel were with the Laser Science Group, Rice Quantum Institute, Department of Electrical and Computer Engineering, Rice University. R. Claps is now with Radiant Photonics, Inc.Measurements of NH3 and CO2 were made in bioreactor vent gases with distributed-feedback diode-laser sensors operating near 2 um. Calculated spectra of NH3 and CO2 were used to determine the optimum transitions for interrogating with an absorption sensor. For ammonia, a strong and isolated absorption transition at 5016.977 cm-1 was selected for trace gas monitoring. For CO2, an isolated transition at 5007.787 cm-1 was selected to measure widely varying concentrations [500 parts per million (ppm) to 10%], with sufficient signal for low mole fractions and without being optically thick for high mole fractions. Using direct absorption and a 36-m total path-length multipass flow-through cell, we achieved a minimum detectivity of 0.25 ppm forNH3 and 40 ppm for CO2. We report on the quasi-continuous field measurements of NH3 and CO2 concentration in bioreactor vent gases that were recorded at NASA Johnson Space Center with a portable and automated sensor system over a 45-h data collection window.Mechanical Engineerin