A larger TatBC complex associates with TatA clusters for transport of folded proteins across the bacterial cytoplasmic membrane.

The twin-arginine translocation (Tat) system transports folded proteins across energized biological membranes in bacteria, plastids, and plant mitochondria. In Escherichia coli, the three membrane proteins TatA, TatB and TatC associate to enable Tat transport. While TatB and TatC together form complexes that bind Tat-dependently transported proteins, the TatA component is responsible for the permeabilization of the membrane during transport. With wild type Tat systems, the TatB- and TatC-containing Tat complexes TC1 and TC2 can be differentiated. Their TatA content has not been resolved, nor could they be assigned to any step of the translocation mechanism. It is therefore a key question of current Tat research to understand how TatA associates with Tat systems during transport. By analyzing affinity-purified Tat complexes with mutations in TatC that selectively enrich either TC1 or TC2, we now for the first time demonstrate that both Tat complexes associate with TatA, but the larger TC2 recruits significantly more TatA than the smaller TC1. Most TatA co-purified as multimeric clusters. Using site-specific photo cross-linking, we could detect TatA-TatC interactions only near TatC transmembrane helices 5 and 6. Substrate-binding did not change the interacting positions but affected the stability of the interaction, pointing to a substrate-induced conformational transition. Together, our findings indicate that TatA clusters associate with TatBC without being integrated into the complex by major rearrangements. The increased TatA affinity of the larger Tat complex TC2 suggests that functional assembly is advanced in this complex.

Role of communication in successful outpatient attendance in a New Zealand hospital: a qualitative study.

BACKGROUND: There are significant implications for both patients and providers when patients do not attend outpatient specialist appointments. Nonattendance has an impact on the efficiency of health care, provider resources and patient health outcomes. AIMS: In this qualitative study we aimed to gather insights on how Dunedin Hospital notifies patients about their appointments, the implications for the hospital and for patients and how the system could be improved. METHODS: We interviewed 13 hospital staff members and nine patients who volunteered to participate because they had missed appointments as a result of communication problems. Interviews were transcribed and analysed thematically using NVivo software. RESULTS: Dunedin Hospital relies heavily on posted letters to inform people about their appointments, with some also receiving reminder texts closer to the time of the appointment. Frustration with the current system was a common theme among both patients and staff. Almost all patients had missed an appointment because of a letter not arriving. While most patients found that the text reminders were helpful, most said they were sent too late and did not allow enough time for arrangements to be made for their appointments. Almost all patients experienced treatment delays, which caused distress. Most patients believed a self-booking system would improve the ability to attend their appointments, and most of them wanted to be notified of appointments via email. CONCLUSIONS: We recommend that a patient-oriented approach to communication should be implemented, and alternative methods of communication should be explored.

Ultrafast response of spontaneous photovoltaic effect in 3R-MoS2-based heterostructures.

Rhombohedrally stacked MoS2 has been shown to exhibit spontaneous polarization down to the bilayer limit and can sustain a strong depolarization field when sandwiched between graphene. Such a field gives rise to a spontaneous photovoltaic effect without needing any p-n junction. In this work, we show that the photovoltaic effect has an external quantum efficiency of 10% for devices with only two atomic layers of MoS2 at low temperatures, and identify a picosecond-fast photocurrent response, which translates to an intrinsic device bandwidth at ∼100-GHz level. To this end, we have developed a nondegenerate pump-probe photocurrent spectroscopy technique to deconvolute the thermal and charge-transfer processes, thus successfully revealing the multicomponent nature of the photocurrent dynamics. The fast component approaches the limit of the charge-transfer speed at the graphene-MoS2 interface. The remarkable efficiency and ultrafast photoresponse in the graphene-3R-MoS2 devices support the use of ferroelectric van der Waals materials for future high-performance optoelectronic applications.