Two functionally distinct manganese clusters formed by introducing a mutation in the carboxyl terminus of a photosystem II reaction center polypeptide, D1, of the green alga Chlamydomonas reinhardtii

AbstractTo study the function of the carboxyl-terminal domain of a photosystem II (PSII) reaction center polypeptide, D1, chloroplast mutants of the green alga Chlamydomonas reinhardtii have been generated in which Leu-343 and Ala-344 have been simultaneously or individually replaced by Phe and Ser, respectively. The mutants carrying these replacements individually, L343F and A344S, showed a wild-type phenotype. In contrast, the double mutant, L343FA344S, evolved O2 at only 20–30% of the wild-type rate and was unable to grow photosynthetically. In this mutant, PSII accumulated to 60% of the wild-type level, indicating that the O2-evolving activity per PSII was reduced to approximately half that of the wild-type. However, the amount of Mn atom detected in the thylakoids suggested that a normal amount of Mn cluster was assembled. An investigation of the kinetics of flash-induced fluorescence yield decay revealed that the electron transfer from Q−A to QB was not affected. When a back electron transfer from Q−A to a donor component was measured in the presence of 3-(3,4-dichlorophenol)-1,1-dimethylurea, a significantly slower component of the Q−A oxidation was detected in addition to the normal component that corresponds to the back electron transfer from the Q−A to the S2-state of the Mn cluster. Thermoluminescence measurements revealed that L343FA344S cells contained two functionally distinct Mn clusters. One was equivalent to that of the wild-type, while the other was incapable of water oxidation and was able to advance the transition from the S1-state to the S2-state. These results suggested that a fraction of the Mn cluster had been impaired by the L343FA344S mutation, leading to decreased O2 evolution. We concluded that the structure of the C-terminus of D1 is critical for the formation of the Mn cluster that is capable of water oxidation, in particular, transition to higher S-states

Thinking about thinking: people underestimate how enjoyable and engaging just waiting is

The ability to engage in internal thoughts without external stimulation is a unique characteristic in humans. The current research tested the hypothesis that people metacognitively underestimate their capability to enjoy this process of “just thinking.” Participants (university students; total N = 259) were asked to sit and wait in a quiet room without doing anything. Across six experiments, we consistently found that participants’ predicted enjoyment and engagement for the waiting task were significantly less than what they actually experienced. This underappreciation of just thinking also led participants to proactively avoid the waiting task in favor of an alternative task (i.e., Internet news checking), despite their experiences not being statistically different. These results suggest an inherent difficulty in accurately appreciating how engaging just thinking can be, and could explain why people prefer keeping themselves busy, rather than taking a moment for reflection and imagination in our daily life

Toxic Epidermal Necrolysis in a Patient with Autoimmune Limbic Encephalitis with Anti-Glutamate Receptor Antibodies

We report on a 44-year-old woman who was diagnosed with toxic epidermal necrolysis (TEN) during the recovery phase from autoimmune limbic encephalitis with anti-glutamate receptor antibodies. Both, autoimmune limbic encephalitis and TEN are very rare diseases. The co-existence of the two diseases has not yet been reported. We speculate that the total of 18 drugs needed for the treatment of encephalitis might have increased the risk of TEN. Similar reports would be required to elucidate the pathophysiology of the co-existence

Support for UNRWA's survival

The United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) provides life-saving humanitarian aid for 5·4 million Palestine refugees now entering their eighth decade of statelessness and conflict. About a third of Palestine refugees still live in 58 recognised camps. UNRWA operates 702 schools and 144 health centres, some of which are affected by the ongoing humanitarian disasters in Syria and the Gaza Strip. It has dramatically reduced the prevalence of infectious diseases, mortality, and illiteracy. Its social services include rebuilding infrastructure and homes that have been destroyed by conflict and providing cash assistance and micro-finance loans for Palestinians whose rights are curtailed and who are denied the right of return to their homeland

A 32-society investigation of the influence of perceived economic inequality on social class stereotyping

International audienceThere is a growing body of work suggesting that social class stereotypes are amplified when people perceive higher levels of economic inequality-that is, the wealthy are perceived as more competent and assertive and the poor as more incompetent and unassertive. The present study tested this prediction in 32 societies and also examines the role of wealth-based categorization in explaining this relationship. We found that people who perceived higher economic inequality were indeed more likely to consider wealth as a meaningful basis for categorization. Unexpectedly, however, higher levels of perceived inequality were associated with perceiving the wealthy as less competent and assertive and the poor as more competent and assertive. Unpacking this further, exploratory analyses showed that the observed tendency to stereotype the wealthy negatively only emerged in societies with lower social mobility and democracy and higher corruption. This points to the importance of understanding how socio-structural features that co-occur with economic inequality may shape perceptions of the wealthy and the poor

Thinking about thinking: People underestimate how enjoyable and engaging just waiting is

The ability to engage in internal thoughts without external stimulation is a unique characteristic in humans. The current research tested the hypothesis that people metacognitively underestimate their capability to enjoy this process of “just thinking”. Participants (university students; total N =259) were asked to sit and wait in a quiet room without doing anything. Across six experiments, we consistently found that participants’ predicted enjoyment and engagement for the waiting task were significantly less than what they actually experienced. This underappreciation of just thinking also led participants to proactively avoid the waiting task in favor of an alternative task (i.e., internet news checking), despite their experiences not being statistically different. These results suggest an inherent difficulty in accurately appreciating how engaging just thinking can be, and could explain why people prefer keeping themselves busy, rather than taking a moment for reflection and imagination in our daily life