Analysis of the electron transfer pathway in small laccase by EPR and UV-vis spectroscopy coupled with redox titration

Bacterial small laccases(SLAC) are promising industrial biocatalysts due to their ability to oxidize a broad range of substrates with exceptional thermostability and tolerance for alkaline p H. Electron transfer between substrate, copper centers, and O2is one of the key steps in the catalytic turnover of SLAC. However, limited research has been conducted on the electron transfer pathway of SLAC and SLAC-catalyzed reactions, hindering further engineering of SLAC to produce tunable biocatalysts for novel applications. Herein, the combinational use of electron paramagnetic resonance(EPR) and ultraviolet-visible(UV-vis) spectroscopic methods coupled with redox titration were employed to monitor the electron transfer processes and obtain further insights into the electron transfer pathway in SLAC. The reduction potentials for type 1 copper(T1Cu), type 2 copper(T2Cu) and type 3copper(T3Cu) were determined to be 367 ± 2 mV, 378 ± 5 m V and 403 ± 2 mV,respectively. Moreover, the reduction potential of a selected substrate of SLAC, hydroquinone(HQ), was determined to be 288 mV using cyclic voltammetry(CV). In this way, an electron transfer pathway was identified based on the reduction potentials. Specifically,electrons are transferred from HQ to T1Cu, then to T2Cu and T3Cu, and finally to O2.Furthermore, superhyperfine splitting observed via EPR during redox titration indicated a modification in the covalency of T2Cu upon electron uptake, suggesting a conformational alteration in the protein environment surrounding the copper sites, which could potentially influence the reduction potential of the copper sites during catalytic processes. The results presented here not only provide a comprehensive method for analyzing the electron transfer pathway in metalloenzymes through reduction potential measurements, but also offer valuable insights for further engineering and directed evolution studies of SLAC in the aim for biotechnological and industrial applications.

Studies and Practices on Cloud-Based Practical Teaching Unified Services System and Teaching Mode

Traditional practical teaching has problems on low reusability, high cost and low collaboration ability. To solve these problems, this paper proposes a solution that is to build and use a novel practical teaching platform based on cloud computing. By utilizing advanced information technology, for example, cloud computing, this solution can present a unified service system providing practical teaching resource management, innovation resource management and knowledge management both inside and outside class. Moreover, an instance implementing the cloud-based practical teaching unified services system, Yun Hai, would be detailedly discussed in this paper. The system deployment, resource configuration and matched practice teaching mode will be presented. Yun Hai is independently developed by State Key Laboratory of Networking and Switching Technology and has been deployed and employed in many institutions. To verify the effectiveness of this teaching platform, we take Data Mining, a representative course of computer science, as an example, and analyze how the system would perform when applied to such course which contains cross-disciplinary knowledges. The practice indicates that this teaching system and practical teaching mode can improve convenience and flexibility on practical teaching resource. This kind of one-stop service can contribute to the overall teaching quality improvement.

Construction and Practice of Cloud-based Experiment and Innovation Project Supporting Platform for Computer Science Education

Higher and more requirements on experiments and innovation projects of computer science courses is brought forward to promote the "Double First Class". For these requirements, the cloud-based experiment and innovation project supporting platform is introduced in this paper. On the one hand, the platform could satisfy the diversified resource requirements of both teachers and students in course experiments and innovation projects. On the other hand, the feature of "construct once and access anywhere" could achieve higher resource utilization rate and lower costs than the traditional "lab-based" experiment mode. The supporting platform has been applied to practice and gains a lot of positive feedbacks.

A cytochrome c551 mediates the cyclic electron transport chain of the anoxygenic phototrophic bacterium Roseiflexus castenholzii

Roseiflexus castenholzii is a gram-negativefilamentous phototrophic bacterium that carries out anoxygenic photosynthesis through a cyclic electron transport chain(ETC).The ETC is composed of a reaction center(RC)–light-harvesting(LH)complex(rcRC–LH);an alternative complex III(rcACIII),which functionally re-places the cytochrome bc1/b6f complex;and the periplasmic electron acceptor auracyanin(rcAc).Although compositionally and structurally different from the bc1/b6f complex,rcACIII plays similar essential roles in oxidizing menaquinol and transferring electrons to the rcAc.However,rcACIII-mediated electron transfer(which includes both an intraprotein route and a downstream route)has not been clearly elucidated,nor have the details of cyclic ETC.Here,we identify a previously unknown monoheme cytochrome c(cyt c551)as a novel periplasmic electron acceptor of rcACIII.It reduces the light-excited rcRC–LH to complete a cyclic ETC.We also reveal the molecular mechanisms involved in the ETC using electron paramagnetic resonance(EPR),spectroelectrochemistry,and enzymatic and structural analyses.Wefind that electrons released from rcACIII-oxidized menaquinol are transferred to two alternative periplasmic electron acceptors(rcAc and cyt c551),which eventually reduce the rcRC to form the complete cyclic ETC.This work serves as a foundation for further studies of ACIII-mediated electron transfer in anoxygenic photosynthesis and broadens our under-standing of the diversity and molecular evolution of prokaryotic ETCs.

Petrogenesis, Tectonic Evolution and Geothermal Implications of Mesozoic Granites in the Huangshadong Geothermal Field, South China

Mesozoic multi-stage tectono-magmatic events produced widely distributed granitoids in the South China Block. Huangshadong(HSD) is located in south-eastern South China Block, where closely spaced hot springs accompany outcrops of Mesozoic granites. New data on whole-rock geochemistry, zircon U-Pb geochronology, and zircon Lu-Hf isotopes are presented, to study the petrogenesis and tectonic evolution of the granites, and to explore the relationship between granites and geothermal anomalies. Zircon U-Pb isotopes display three periods of granites in the HSD area: Indosinian(ca. 253 Ma, G4) muscovite-bearing monzonitic granite, early Yanshanian(ca. 175–155 Ma, G5 and G3) monzonitic granite and granodiorite, and late Yanshanian(ca. 140 Ma, G1 and G2) biotite monzonitic granite. In petrogenetic type, granites of the three periods are I-type granite. Among them, G1, G2, G3, and G4 are characterized by high fractionation, with high values of SiO2, alkalis, Ga/Al, and Rb/Sr, and depletion in Sr, Ba, Zr, Nb, Ti, REEs, with low(La/Yb)N, Nb/Ta, and Zr/Hf ratios and negative Eu anomalies. In terms of tectonic setting, 253 Ma G4 may be the product of partial melting of the ancient lower crust under post-orogenic extensional tectonics, as the closure of the Paleo-Tethys Ocean resulted in an intracontinental orogeny. At 175 Ma, the subduction of the Pacific Plate became the dominant tectonic system, and low-angle subduction of the Paleo-Pacific Plate facilitated partial melting of the subducted oceanic crust and basement to generate the hornblende-bearing I-type granodiorite. As the dip angle of the subducting plate increased, the continental arc tectonic setting was transformed to back-arc extension, inducing intense partial melting of the lower crust at ca. 158 Ma and resulting in the most frequent granitic magmatic activity in the South China hinterland. When slab foundering occurred at ca. 140 Ma, underplating of mantle-derived magmas caused melting of the continental crust, generating extensive highly fractionated granites in HSD. Combining the granitic evolution of HSD and adjacent areas and radioactive heat production rates, it is suggested that highly fractionated granites are connected to the enrichments in U and Th with magma evolution. The high radioactive heat derived from the Yanshanian granites is an important part of the crustal heat, which contributes significantly to the terrestrial heat flow. Drilling ZK8 reveals deep, ca. 140 Ma granite, which implies the heat source of the geothermal anomalies is mainly the concealed Yanshanian granites, combining the granite distribution on the surface.

Crustal Thermo-Structure and Geothermal Implication of the Huangshadong Geothermal Field in Guangdong Province

Dense distribution of granites and surrounding hot springs, the high anomalous heating rates of geothermal fluids and the high geothermal gradients in shallow crust in Southeast China are revealed by previous geothermal explorations. However, there have always been debates on the genesis of geothermal anomalies of Southeast China. It is imperative to look into the genesis mechanism of geothermal anomalies through selecting a typical geothermal field, and constructing fine crustal thermostructure. In this study, in-depth excavation is implemented for the previous data of geophysical exploration and deep drilling exploration in the Huangshadong area. We synthetically analyze the results of radioactive heat productions(RHPs), thermophysical properties of rocks and audio-frequency magnetotellurics(AMT) sounding. This study concludes that the coefficient of radioactive heat generation(RHG) of crustal rocks and conduction heat of concealed granites is the main formation mechanism of geothermal anomalies of South China, where occurs a Great Granite Province. There is a regional indicating implication for the genesis of geothermal anomalies, taking the Huangshadong geothermal field as a typical example. It is also an important reference to guide the exploration, evaluation, development and utilization of geothermal resources in this region.

Downstream Channel Evolution and Its Causes in the Yuan River during the Qing Dynasty

The determination of channel evolutions and the causes is important for reconstructing the evolutionary history of river landforms.This study aimed to elucidate the downstream channel evolution of the Yuan River in Hunan Province,China,during the Qing Dynasty via Landsat 8 satellite image data and relevant literature.The objective was to establish the modes of channel evolution and discuss the significance of historical climate change.The downstream paleochannel of the Yuan River was identified in the Late Ming Dynasty and Early Qing Dynasty(1600–1644 AD),the Kangxi-Qianlong periods of the Qing Dynasty(1661–1796 AD),the Late Qing Dynasty(1840–1912 AD),and the World War II(1939–1945 AD),and three main modes of river evolution were determined.Using remote sensing data and the ancient literature,the evolution characteristics of the paleochannel in the Lower Yuan River were analyzed and its distribution across historical periods was comprehensively revealed.The findings reveal a strong correlation between channel evolution,flood events,and climate change.Numerous flood events that occurred from the Late Qing Dynasty to the World War II caused a high rate of channel evolution,demonstrating the combined effects of climate change and human activities.These findings will help adopt robust and resilient hydrological management methods in the future of a changing climate.

Fact-condition statements and super relation extraction for geothermic knowledge graphs construction

Researchers utilize information from the geoscience literature to deduce the regional or global geological evolution.Traditionally this process has relied on the labor of researchers.As the number of papers continues to increase,acquiring domain-specific knowledge becomes a heavy burden.Knowledge Graph(KG)is proposed as a new knowledge representation technology to change this situation.However,the super relation is not considered in the previous KG,which bridges the geological phenomenon(fact)and its precondition(condition).For instance,in the statement(“the late Archean was a crucial transition period in the history of global geodynamics”),the condition statement(“crucial transition for global geodynamics”)works as the complementary fact statement(“the late Archean was a crucial transition period”),which defines the scale of crucial transition accurately in the late Archean.In this study,fact-condition statement extraction is introduced to construct a geological knowledge graph.A rule-based multi-input multi-output model(R-MIMO)is proposed for information extraction.In the R-MIMO,fact-condition statements and their super relation are considered and extracted for the first time.To verify its performances,a GeothCF dataset with 1455 fact tuples and 789 condition tuples is constructed.In experiments,the R-MIMO model achieves the best performance by using BERT as encoder and LSTM-d as decoder,achieving F180.24%in tuple extraction and F170.03%in tag prediction task.Furthermore,the geothermic KG with super relation is automatically constructed for the first time by trained R-MIMO,which can provide structured data for further geothermic research.