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Carotenoid (Car) pigments perform central roles in photosynthesis-related light harvesting (LH), photoprotection, and assembly of functional pigment-protein complexes. However, the relationships between Car depletion in the LH, assembly of the prokaryotic reaction center (RC)-LH complex, and quinone exchange are not fully understood. Here, we analyzed native RC-LH (nRC-LH) and Car-depleted RC-LH (dRC-LH) complexes in Roseiflexus castenholzii, a chlorosome-less filamentous anoxygenic phototroph that forms the deepest branch of photosynthetic bacteria. Newly identified exterior Cars functioned with the bacteriochlorophyll B800 to block the proposed quinone channel between LHαβ subunits in the nRC-LH, forming a sealed LH ring that was disrupted by transmembrane helices from cytochrome c and subunit X to allow quinone shuttling. dRC-LH lacked subunit X, leading to an exposed LH ring with a larger opening, which together accelerated the quinone exchange rate. We also assigned amino acid sequences of subunit X and two hypothetical proteins Y and Z that functioned in forming the quinone channel and stabilizing the RC-LH interactions. This study reveals the structural basis by which Cars assembly regulates the architecture and quinone exchange of bacterial RC-LH complexes. These findings mark an important step forward in understanding the evolution and diversity of prokaryotic photosynthetic apparatus.

It is widely recognized that reliability-based optimization methodologies are rational and promising tools to perform the life-cycle management (LCM) of civil engineering structures. In order to re...

Harmless treatment and resource utilization of wastes like fly ash have always been a social difficulty and a research hot spot in the field of pavement. In this paper, samples of fly ash generated from a coal-fired power plant in Yan’an City, Shaanxi Province were collected; and a desulfurized-high-calcium-fly-ash (DHCFA) was selected as the representative to be used for the alternative of traditional limestone fine powder (LFP) in asphalt mixture. Specifically, the chemical and physical characteristics of DHCFA and LFP were studied and compared firstly. Then the performance of asphalt mortar and asphalt mixture containing different amounts of DHCFA were further investigated. XRF and XRD results show that DHCFA and LFP both have significant alkalinity, and DHCFA has relatively richer chemical composition and phase distribution. TG-DSC results show DHCFA and LFP both satisfy the construction requirements on thermal stability. Asphalt mortar results showed DHCFA had the similar effect as LFP (control sample) on the whole. Asphalt mixture results revealed that the characteristics of DHCFA such as density, composition and compaction influence the performance of asphalt mixture. DHCFA could improve the low temperature performance and water stability of asphalt mixture, while reducing the high temperature performance and strength. Above results indicates that DHCFA could be used for mineral powder in asphalt mixture, however, its dosage should be carefully verified since it has adverse impact on the high temperature performance and strength of asphalt mixture.

Generally, various kinds of cracks are the main type of distresses during the service period of asphalt pavements. To save maintenance costs and improve the crack resistance of asphalt pavements effectively, this paper presents a unique design method for the material composition of small particle-size (SPS) asphalt mixture for controlling cracks in asphalt pavement. First, Stone Mastic Asphalt (SMA)-II was designed as a basic gradation according to the A.N. Talbot curve and SMA-II-1, SMA-II-2 and SMA-II-3 were designed according to the Superpave mix design method, the Bailey method and the Particle interference theory, respectively. Second, based on Marshall test results, the optimal fiber content and optimal asphalt content of three gradations were determined. Then, the influence of the passing rate of 1.18-mm sieve and 0.075-mm sieve on the air voids of SMA-II and the influence of the filler-asphalt ratio on the performance of SMA-II were investigated, and an appropriate range of filler-asphalt ratio was obtained. Finally, a high-temperature performance test, a water stability test, and a skid resistance test demonstrate that the overall performance of SMA-II can satisfy the specifications. A low-temperature bend test and analysis of bending strain energy density show that SMA-II with a crumb rubber modifier and a polymer fiber has better crack resistance performance than SMA-I (SBS-modified mixture). Life-cycle cost analysis shows the economic advantage of SPS asphalt thin overlays over traditional AC-13 thin overlays.

Corrosion-induced crack width can provide effective information on the deterioration level of in situ corroded reinforced concrete (RC) structures. However, the uncertainty associated with the relationship between corrosion-induced crack width and steel corrosion in RC structures is quite large. In this study, a probabilistic framework for estimating the structural capacity of corroded RC structures using the observational corrosion-induced crack width distribution and machine learning is proposed. Based on the experimental results of corroded RC beams, random field theory, and finite element (FE) analysis, artificial samples composed of corrosion-induced crack width and steel weight loss distributions over the RC beams are generated. Two machine learning-based models are then developed using these samples to estimate the steel weight loss distribution from the observational corrosion-induced crack distribution. Finally, a Monte Carlo-based FE analysis with the estimated steel weight loss distribution as the input data is conducted to obtain the probability density function (PDF) of the structural capacity of corroded RC beams. For illustrative purposes, the effect of observational corrosion-induced crack width distribution on the PDF of flexural capacity of an existing RC beam is investigated using the proposed framework. The results show that the proposed framework using a machine learning-based model is a reliable and computationally efficient approach for estimating the structural capacity of corroded RC members and demonstrates the potential for assessing the deterioration condition of existing RC structures based on the corrosion-induced crack width distribution.

ATM/Tel1 is an apical kinase that orchestrates the multifaceted DNA damage response. Mutations of ATM/Tel1 are associated with ataxia telangiectasia syndrome. Here, we report cryo-EM structures of symmetric dimer (4.1 Å) and asymmetric dimer (4.3 Å) of Saccharomyces cerevisiae Tel1. In the symmetric state, the side chains in Tel1 C-terminus (residues 1129–2787) are discernible and an atomic model is built. The substrate binding groove is completely embedded in the symmetric dimer by the intramolecular PRD and intermolecular LID domains. Point mutations in these domains sensitize the S. cerevisiae cells to DNA damage agents and hinder Tel1 activation due to reduced binding affinity for its activator Xrs2/Nbs1. In the asymmetric state, one monomer becomes more compact in two ways: the kinase N-lobe moves down and the Spiral of α-solenoid moves upwards, which resemble the conformational changes observed in active mTOR. The accessibility of the activation loop correlates with the synergistic conformational disorders in the TRD1-TRD2 linker, FATC and PRD domains, where critical post-translational modifications and activating mutations are coincidently condensed. This study reveals a tunable allosteric network in ATM/Tel1, which is important for substrate recognition, recruitment and efficient phosphorylation.