The native architecture of a photosynthetic membrane

In photosynthesis, the harvesting of solar energy and its subsequent conversion into a stable charge separation are dependent upon an interconnected macromolecular network of membrane-associated chlorophyll–protein complexes. Although the detailed structure of each complex has been determined, the size and organization of this network are unknown. Here we show the use of atomic force microscopy to directly reveal a native bacterial photosynthetic membrane. This first view of any multi-component membrane shows the relative positions and associations of the photosynthetic complexes and reveals crucial new features of the organization of the network: we found that the membrane is divided into specialized domains each with a different network organization and in which one type of complex predominates. Two types of organization were found for the peripheral light-harvesting LH2 complex. In the first, groups of 10–20 molecules of LH2 form light-capture domains that interconnect linear arrays of dimers of core reaction centre (RC)–light-harvesting 1 (RC–LH1–PufX) complexes; in the second they were found outside these arrays in larger clusters. The LH1 complex is ideally positioned to function as an energy collection hub, temporarily storing it before transfer to the RC where photochemistry occurs: the elegant economy of the photosynthetic membrane is demonstrated by the close packing of these linear arrays, which are often only separated by narrow 'energy conduits' of LH2 just two or three complexes wide

Ultra-fast sampling of terahertz pulses from a quantum cascade laser using superconducting antenna-coupled NbN and YBCO detectors

We demonstrate the ultra-fast detection of terahertz pulses from a quantum cascade laser (QCL) using superconducting NbN and YBCO detectors. This has enabled both the intrapulse and interpulse dynamics of a THz QCL to be measured directly, including interpulse heating effects on sub-μs timescales

The hierarchical assembly of septins revealed by high-speed AFM

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Jiao, F., Cannon, K. S., Lin, Y. C., Gladfelter, A. S., & Scheuring, S. The hierarchical assembly of septins revealed by high-speed AFM. Nature Communications, 11(1), (2020): 5062, doi:10.1038/s41467-020-18778-x.Septins are GTP-binding proteins involved in diverse cellular processes including division and membrane remodeling. Septins form linear, palindromic heteromeric complexes that can assemble in filaments and higher-order structures. Structural studies revealed various septin architectures, but questions concerning assembly-dynamics and -pathways persist. Here we used high-speed atomic force microscopy (HS-AFM) and kinetic modeling which allowed us to determine that septin filament assembly was a diffusion-driven process, while formation of higher-order structures was complex and involved self-templating. Slightly acidic pH and increased monovalent ion concentrations favor filament-assembly, -alignment and -pairing. Filament-alignment and -pairing further favored diffusion-driven assembly. Pairing is mediated by the septin N-termini face, and may occur symmetrically or staggered, likely important for the formation of higher-order structures of different shapes. Multilayered structures are templated by the morphology of the underlying layers. The septin C-termini face, namely the C-terminal extension of Cdc12, may be involved in membrane binding.We thank J. Thorner for the generous gift of the CTE mutant plasmids. K.S.C. was supported in part by a grant from NIGMS under award T32 GM119999 and A.S.G., F.J. and S.S. were supported by NIH RO1 GM130934

Fatigue in U.S. Astronauts Onboard the International Space Station: Environmental Factors, Operational Impacts, and Implementation of Countermeasures

Since 2000, US astronauts have been supporting missions up to a six month duration on the International Space Station (ISS). Crewmembers have experienced fatigue for reasons similar to military deployments. Astronauts experience psychological stressors such as heavy workloads, extended duty periods, circadian misalignment, inadequate/ineffective sleep, and loss of the environmental cues of a gravity environment. Complicating the psychological stressors are environmental factors; distracting background noise, unexpected and variable mission schedules, unfavorable thermal control, elevated CO2 levels, and an unusual sleep environment with schedules that impinge on presleep periods. Physiological contributors to poor sleep and fatigue include a cephalad fluid shift and back pain. Restful sleep is further challenged due to a lack of gravityrelated proprioceptive cues and need for restraints. The term "space fog" has been used by astronauts to describe a phenomenon of forgetfulness, slowed reaction time and transient confusion while trying to complete tasks. There is a distinct temporal correlation with arrival on the Space Station and the onset of slowed cognitive skills and a spontaneous resolution that may take up to 6 weeks. The Genesis of this phenomenon may be chronic fatigue secondary to transitioning from a planar environment to a 360deg microgravity perspective. Recently, countermeasures to improve sleep duration and quality in astronauts on the ISS have been instituted with moderate degrees of success as measured by selfreaction time (psychomotor vigilance task testing), actigraphy, and subjective reports. Judicious use of stimulants and hypnotics, light therapy, controlled sleep periods and sleep shifting and reducing ambient CO2 levels are a few of the most promising countermeasures being used in space to improve sleep and reduce fatigue

Teknik Pemuliaan Kentang dan Produksi Bibit Kentang Bebas Virus di Texas, USA

Kentang merupakan sumber karbohidrat penting di negara maju seperti Amerika Serikat, Eropa dan Australia. Produktivitas kentang di Amerika Serikat mencapai 40 ton/ha. Berbagai varietas kentang juga tersedia dengan kegunaan yang berbeda seperti untuk keripik, kentang goreng (french fries), kentang rebus dan kentang panggang. Tulisan ini bertujuan untuk memaparkan teknik pemuliaan kentang untuk mendapatkan berbagai varietas serta metode perbanyakan benih kentang bebas virus melalui teknik kultur jaringan di Texas. Kunci utama keberhasilan pemuliaan kentang di Texas adalah ketersediaan sumber daya genetik kentang yang luas, serta evaluasi di lapang (field day) untuk genotipe-genotipe potential hasil pemuliaan yang melibatkan para peneliti, petani, pelaku pasar dan media. Teknik kultur jaringan digunakan untuk perbanyakan benih terpilih, serta meminimalisasi penyebaran penyakit yang berasal dari umbi seperti virus kentang PVX, PVY dan PLRV. Penggunaan teknik kultur jaringan juga mampu menekan biaya produksi benih karena mengurangi penggunaan ruang untuk stok benih dan perbanyakan di rumah kaca. Tahapan pemuliaan, produksi benih di lapang, evaluasi varietas, introduksi benih in vitro, perbanyakan in vitro, teknik eliminasi virus dan produksi benih di rumah kaca dideskripsikan pada tulisan ini

Optimasi Metode Cryotherapy Untuk Mengeliminasi Virus Pada Tunas Kentang in Vitro

Penggunaan benih kentang generasi awal dan bebas virus merupakan kunci keberhasilan produksi kentang berkualitas. Cryotherapy (perendaman dalam nitrogen cair) merupakan teknik terbaru untuk mengeliminasi virus pada benih kentang. Salah satu kendala dalam penerapan teknologi cryotherapy ialah tingkat daya hidup eksplan yang masih rendah. Penelitian ini bertujuan untuk mengetahui efektifitas teknik enkapsulasi-dehidrasi untuk mendapatkan tunas yang sehat setelah perendaman dalam nitrogen cair. Ujung tunas in vitro ukuran 2–3 mm dari empat genotipe kentang di prakultur selama 3 hari secara bertahap pada media MS dengan penambahan gula 0,25 M, 0,5 M, dan 0, 75 M. Kemudian tunas dienkapsulasi, didehidrasi selama 5 jam, lalu direndam dalam nitrogen cair selama 60 menit lalu dihangatkan kembali dalam waterbath selama 3 menit. Tunas dalam kapsul kemudian dikulturkan pada media MS +30 g/l sukrosa + 8 g/l agar + 0,4 mg/l BAP + 1 mg/l GA3 untuk pemulihan, lalu dipelihara di ruang kultur dengan suhu 24oC. Daya hidup ujung tunas diamati pada minggu ke-8 dengan menggunakan kriteria skoring sebagai berikut: (1) pemutihan jaringan dan tidak ada respons pertumbuhan, (2) kalus mencokelat, (3) kalus hijau, (4) tumbuh tunas, dan (5) planlet sehat. Hasil penelitian menunjukkan daya hidup ujung tunas bervariasi antargenotipe. Skor daya hidup berkisar 1–2 (frekuensi 2–10) pada perlakuan nitrogen cair, yang menunjukkan tidak ada respons pertumbuhan tunas, beberapa memperlihatkan pertumbuhan kalus. Tunas pada perlakuan kontrol (tanpa perendaman dalam nitrogen cair) menunjukkan skor daya hidup 5 (frekuensi 1–7), di mana ujung tunas mampu beregenerasi menjadi planlet

Oro-Nasal Mask Versus Two-Way Non-Rebreathing Valves for Maximal Aerobic Capacity Testing in Astronauts

Astronauts complete maximal aerobic capacity (VO2pk) testing as part of their annual fitness assessment (AFA) as well as several times once assigned to an International Space Station mission. Historically, the 2-Way T-Shape Non-Rebreathing valve with a mouthpiece and nose clip (Mouthpiece) has been used in these tests. The testing procedure was updated to use the oro-nasal mask (Mask) for the AFA starting in June 2017. Astronauts who used the mask during their AFA requested it be certified to be used for all mission associated tests. Considering the criticality of the data and the schedule constraints of astronauts, it is imperative that the requested hardware change provide data with equivalent reliability and repeatability as provided by the mouthpiece. PURPOSE: To assess the reliability and validity of mask vs. mouthpiece by comparing submaximal and VO2pkdata within subjects (approximately 1 year apart). METHODS: Each of 17 active astronauts completed a VO (sub 2pk) test with the mouthpiece (first) and the mask (second) for their AFA. The VO (sub 2pk) test was conducted on a cycle ergometer with a metabolic cart. The nominal protocol started with a 3-minute warm-up at 50 Watts (W) and increased 25W every minute until volitional fatigue (Light: 45W start; 15W increase). The VO (sub 2pk)s were compared between tests and the expected day-to-day variation (plus or minus 5 percent) was used as the threshold for determining agreement between tests. Submaximal values were plotted and evaluated visually for deviations between mask and mouthpiece. RESULTS: VO (sub 2pk) values were more than 5 percent different, despite similar test times, between mouthpiece and mask in 6 of 17 comparisons, 3 of which were higher with the mask (9.0 plus or minus 5.9 percent) while 3 were lower (minus10.8 plus or minus 2.0 percent) with the mask. The submaximal data did not indicate a leak in either apparatus during these tests. An Astronaut Strength & Conditioning Rehabilitation specialist confirmed that the measured differences in VO (sub 2pk) of these 6 astronauts was consistent with observed changes in exercise habits during the year that separated the two tests. CONCLUSION: After being presented with the results of this data mining effort the mask was accepted for use in all tests, excepting that, if a leak is detected without resolve, the test will be repeated (if schedule allows) and remaining tests will be completed with the mouthpiece

Self-assembled monolayer of light-harvesting core complexes of photosynthetic bacteria on an amino-terminated ITO electrode

Light-harvesting antenna core (LH1-RC) complexes isolated from Rhodospirillum rubrum and Rhodopseudomonas palustris were successfully self-assembled on an ITO electrode modified with 3-aminopropyltriethoxysilane. Near infra-red (NIR) absorption, fluorescence, and IR spectra of these LH1-RC complexes indicated that these LH1-RC complexes on the electrode were stable on the electrode. An efficient energy transfer and photocurrent responses of these LH1-RC complexes on the electrode were observed upon illumination of the LH1 complex at 880 nm

Potential of Malian Landraces in Hybrid Combination

The first possibility of economic hybrid seed production in sorghum has been discussed since the discovery of the genetic-cytoplasmic male-sterility. The greater advantage of hybrids to yields, compared to cultivars, has been demonstrated throughout the world. Hybrids made with local cultivars of Mali used as the male parents and were compared to their parents. Heterosis was observed in all stages of plant growth. Seedling vigour and seedling drought tolerance were emphatically better than the Malian parents. The frequency of landraces with fertility reactions was more frequent than those with maintainer reactions. Significant and positive heterotic effects were recorded for grain yield per panicle and the panicle yield components, seed number and seed weight. However, there was no scope for direct exploitation of the hybrids involving the ATx623 and Malian landrace parents. The typical Caudatum “turtle-back” seed shape was dominant in hybrid combinations with all Malian races. This seed shape renders the grain more difficult to dehull than local cultivars. The grain of hybrids made with guinea parents had a thick brown sub coat with astringent tannins, which was undesirable for food uses