1.Exploring Chemical Constituent Distribution in Blood/Brain(Hippocampus) and Emotional Regulatory Effect of Raw and Vinegar-processed Products of Citri Reticulatae Pericarpium Viride
Yi BAO ; Yonggui SONG ; Qianmin LI ; Zhifu AI ; Genhua ZHU ; Ming YANG ; Huanhua XU ; Qin ZHENG ; Yiting HUANG ; Zihan GAO ; Dan SU
Chinese Journal of Experimental Traditional Medical Formulae 2026;32(2):189-197
ObjectiveTo investigate the migration and distribution characteristics of chemical constituents in blood and hippocampal tissues before and after vinegar processing of Citri Reticulatae Pericarpium Viride(CRPV), and to explore the potential material basis and mechanisms underlying their regulatory effects on emotional disorders by comparing the effects of raw and vinegar-processed products of CRPV. MethodsUltra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry(UPLC-Q-TOF-MS/MS) was employed to characterize and identify the chemical constituents of raw and vinegar-processed products of CRPV extracts, as well as their migrating components in blood and hippocampal tissues after oral administration. Reference standards, databases, and relevant literature were utilized for compound annotation, with data processing performed using PeakView 1.2 software. Seventy male C57BL/6 mice were randomly divided into seven groups, including the blank group, model group, diazepam group(2.5 mg·kg-1), raw CRPV low/high dose groups(0.6, 1.2 g·kg-1), and vinegar-processed CRPV low/high dose groups(0.6, 1.2 g·kg-1), with 10 mice per group. Except for the blank group, all other groups underwent chronic restraint stress(2 h·d-1) for 20 d. Each drug-treated group received oral administration at the predetermined dose starting 10 d after modeling, with a total treatment duration of 10 d. Following model-based drug administration, mice underwent open-field, forced swimming, and elevated plus maze tests. After anesthesia with isoflurane, whole brains were collected from each group of mice, and hippocampi were dissected. Reactive oxygen species(ROS) level in hippocampal tissues was quantified by enzyme-linked immunosorbent assay(ELISA). Hematoxylin-eosin(HE) staining was used to observe hippocampal tissue morphology. Immunofluorescence was performed to detect neuronal nuclei(NeuN) and peroxisome proliferator-activated receptor alpha(PPARα) expressions in hippocampal tissue. Then, pharmacodynamic evaluations were conducted to assess the effects of raw and vinegar-processed CRPV on mood disorders, exploring the potential mechanisms. ResultsVinegar processing caused significant changes in the chemical composition of CRPV, with 18 components showing increased relative content and 35 components showing decreased relative content. The primary changes occurred in flavonoid compounds, including 20 flavonoids, 20 flavonoid glycosides, 3 triterpenes, 3 phenolic acids, 1 alkaloid, and 6 other compounds. Twenty-one components were detected in blood(15 methoxyflavones, 4 flavonoid glycosides, and 2 phenolic acids), with 17 shared between raw and vinegar-processed CRPV. Seven components reached hippocampal tissues(all common to both forms). In regulating emotional disorders, Vinegar-processed CRPV exhibited superior antidepressant-like effects compared to raw products. HE staining revealed that both treatments improved hippocampal neuronal morphology, particularly in the damaged CA1 and CA3 regions. Immunofluorescence and ELISA analyses demonstrated that both raw and vinegar-processed CRPV significantly modulated NeuN and PPARα expressions in hippocampal tissue while alleviating oxidative stress induced by excessive ROS(P<0.05). ConclusionThe chemical composition of CRPV undergoes changes after vinegar processing, but the migrating components in blood and hippocampus are primarily methoxyflavonoids. These components may serve as the potential material basis for activating the PPARα pathway, thereby negatively regulating ROS generation in the hippocampus, reducing oxidative stress, and promoting the development of NeuN-positive neurons. These findings provide experimental evidence for enhancing quality standards, pharmacodynamic material research, and active drug development of raw and vinegar-processed CRPV.
2.Technique and Application of Deep Learning-based EEG Denoising
Bao-Lian SHAN ; Hai-Qing YU ; Yong-Zhi HUANG ; Jia-Yuan MENG ; Min-Peng XU ; Tzyy-Ping JUNG ; Dong MING
Progress in Biochemistry and Biophysics 2026;53(8):2147-2160
Electroencephalography (EEG) is a non-invasive neurophysiological monitoring technique. It records the electrical activity of the cerebral cortex using electrodes placed on the scalp surface. Owing to its high safety, portability, and millisecond-level temporal resolution, EEG has been widely utilized in a variety of fields, including clinical diagnosis, brain-computer interfaces (BCIs), and cognitive neuroscience research. However, due to its microvolt-level amplitude, EEG is highly susceptible to various artifacts, including electrooculographic (EOG), electrocardiographic (ECG), electromyographic (EMG), and power line interference (PLI). These artifacts can obscure genuine neural activity and introduce spurious electrophysiological features. Consequently, they may compromise EEG signal quality, thereby reducing the reliability of downstream analyses. To address this issue, numerous EEG artifact removal methods have been developed, including both traditional denoising techniques and deep learning-based approaches. Traditional EEG denoising methods have long served as the primary solutions for artifact removal. Representative approaches include filtering, regression, and blind source separation. Although these methods have demonstrated effectiveness in specific scenarios, they suffer from several inherent limitations. Filtering assumes that artifacts and EEG signals can be separated in the frequency domain, but many artifacts, such as EOG and EMG, overlap with EEG spectra, which may lead to the loss of valuable neural information. Regression methods require high-quality artifact references to estimate and subtract contaminations, limiting their effectiveness in reference-free scenarios. Blind source separation can remove artifacts without external references, but it typically requires the number of EEG channels to exceed the number of sources, restricting its application in single- or low-channel EEG recordings. Deep learning-based EEG denoising methods address these limitations effectively. First, they learn the nonlinear mapping between contaminated and clean EEG directly from data in an end-to-end manner. This approach does not rely on assumptions about spectral separability, thereby preserving neural activity more completely. Second, the reference information is incorporated during the training phase, allowing the trained model to perform artifact removal independently without external references. Third, deep learning models can be flexibly designed to accommodate various recording setups, achieving robust denoising for both high-density and single-channel EEG. Collectively, these advantages enable deep learning-based methods to overcome the main challenges of traditional approaches, providing more accurate and reliable EEG signal recovery. The superior denoising performance of deep learning-based EEG denoising methods has attracted increasing attention in EEG artifact removal research. As a result, many deep learning-based denoising methods have been developed and successfully applied in neural engineering areas. However, a systematic review of the techniques and applications in this field is still lacking. To address this gap, this paper reviews recent advances in deep learning-based EEG denoising from four perspectives: technical principle, benchmark dataset, denoising model, and evaluation method. Representative applications in neural signal analysis and BCI decoding are also summarized. Furthermore, the advantage, existing challenge, and future research direction of deep learning-based EEG denoising are discussed. This review aims to provide valuable theoretical insights and technical guidance for researchers. It is also expected to promote further advances and broader applications of deep learning-based EEG denoising techniques.
3.Applications of Brain-heart Interaction in Consciousness State Assessment
Jun-Yi WANG ; Hai-Qing YU ; Qiang-Fan MENG ; Yong-Zhi HUANG ; Min-Peng XU ; Dong MING
Progress in Biochemistry and Biophysics 2026;53(10):2767-2785
Consciousness, which underpins human perception, cognition, and behavioural responses, has long been a major focus of neuroscience and medicine. Alterations in consciousness occur not only during reversible processes such as sleep and anaesthesia, but also in pathological conditions, including disorders of consciousness (DOC) and brain injury. With recent advances in the synchronized acquisition and analysis of multimodal physiological signals, such as electroencephalography (EEG) and electrocardiography (ECG), the dynamic interactions between the heart and brain have become increasingly apparent. A growing body of evidence indicates that heart-brain interactions are closely associated with the maintenance and transition of consciousness states, offering a novel perspective for elucidating their underlying mechanisms and supporting relevant clinical assessments. Current approaches to heart-brain interaction analysis for consciousness-state assessment can be broadly grouped into three categories: ECG-based methods, EEG-based methods, and heart-brain coupling analysis. These approaches characterize heart-brain interactions during changes in consciousness from the complementary perspectives of autonomic regulation, cortical interoceptive processing, and cross-system information transfer, respectively. Nevertheless, this field remains at an early stage. Most studies have focused on a single experimental context or a fixed analytical method, with insufficient systematic consideration of the applicability and limitations of different approaches. Moreover, the mechanisms underlying the emergence and alteration of consciousness remain incompletely understood. Accordingly, this review examines heart-brain interaction methods employed in recent consciousness-state assessment studies in accordance with progressively deeper analytical perspectives, and systematically evaluates the advantages and limitations of these methods across distinct consciousness-related conditions. Heart rate variability (HRV) is one of the classical ECG-based indices used to investigate heart-brain interactions. It refers to fluctuations in consecutive interbeat intervals over a specified time period and is regarded as a physiological measure of autonomic nervous system regulation that may indirectly reflect the strength of heart-brain interactions. Depending on the analytical dimension, HRV analysis is commonly divided into time-domain, frequency-domain, and complexity-index analyses. These approaches characterize autonomic activity in terms of temporal fluctuations, the distribution of frequency components, and nonlinear dynamical properties, respectively. Although extensive research supports their physiological interpretation, they cannot characterize directional interactions from the heart to the brain. Among EEG-based methods for heart-brain interaction analysis, EEG activity directly related to cardiac fluctuations has received particular attention. One of the most widely used measures is the heartbeat-evoked potential (HEP). HEP-based approaches are considered to directly reflect the capacity of the cerebral cortex to process cardiac afferent signals and may be especially advantageous for characterizing rapidly changing consciousness levels, such as those observed during sleep. However, they do not comprehensively capture dynamic bidirectional information exchange between the brain and heart and are susceptible to cardiac artefacts, respiration, and variation in preprocessing procedures. Heart-brain coupling analysis quantifies functional associations between ECG and EEG through cross-system interaction measures, thereby assessing dynamic interactions between the heart and brain. It emphasizes information transfer, feedback regulation, and cross-timescale coordination between the two systems, offering a more comprehensive perspective for investigating changes in consciousness during sleep, anaesthesia, and DOC. However, the neurophysiological mechanisms and physiological interpretation of individual computational indices have not yet been fully established, and the robustness of their results and their potential for clinical generalization require further validation. Finally, this review summarizes the commonalities and differences among the three classes of methods across research domains involving different consciousness states. It further argues that heart-brain interaction research requires deeper investigation at both the mechanistic level of consciousness and the level of clinical application. Current challenges and key issues are identified, and future directions and feasible pathways for heart-brain interaction research are discussed, with the aim of providing new perspectives for researchers in related fields.
4.Applications of Vaterite in Drug Loading and Controlled Release
Xiao-Hui SONG ; Ming-Yu PAN ; Jian-Feng XU ; Zheng-Yu HUANG ; Qing PAN ; Qing-Ning LI
Progress in Biochemistry and Biophysics 2025;52(1):162-181
Currently, the drug delivery system (DDS) based on nanomaterials has become a hot interdisciplinary research topic. One of the core issues is drug loading and controlled release, in which the key lever is carriers. Vaterite, as an inorganic porous nano-material, is one metastable structure of calcium carbonate, full of micro or nano porous. Recently, vaterite has attracted more and more attention, due to its significant advantages, such as rich resources, easy preparations, low cost, simple loading procedures, good biocompatibility and many other good points. Vaterite, gained from suitable preparation strategies, can not only possess the good drug carrying performance, like high loading capacity and stable loading efficiency, but also improve the drug release ability, showing the better drug delivery effects, such as targeting release, pH sensitive release, photothermal controlled release, magnetic assistant release, optothermal controlled release. At the same time, the vaterite carriers, with good safety itself, can protect proteins, enzymes, or other drugs from degradation or inactivation, help imaging or visualization with loading fluorescent drugs in vitro and in vivo, and play synergistic effects with other therapy approaches, like photodynamic therapy, sonodynamic therapy, and thermochemotherapy. Latterly, some renewed reports in drug loading and controlled release have led to their widespread applications in diverse fields, from cell level to clinical studies. This review introduces the basic characteristics of vaterite and briefly summarizes its research history, followed by synthesis strategies. We subsequently highlight recent developments in drug loading and controlled release, with an emphasis on the advantages, quantity capacity, and comparations. Furthermore, new opportunities for using vaterite in cell level and animal level are detailed. Finally, the possible problems and development trends are discussed.
5.Simultaneous Determination of 21 Kinds of Aconitum Alkaloids in Biological Specimens and Herbal Wines Using Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry
Ju YANG ; Guo-Jun LI ; Xian-Mou FAN ; Rui-Bin ZHAO ; Shao-Ming SU ; Xu-Xian FU ; En-Jin ZHU ; Qi-Lin HUANG ; Yao QIN ; Li-Na LI
Chinese Journal of Analytical Chemistry 2025;53(8):1391-1401,后插1-后插6,封3
A method for simultaneous determination of 21 kinds of Aconitum alkaloids(ATS)in biological specimens and infused liquor using ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS)was developed.The biological samples were pretreated with methanol-acetonitrile(1∶2,V/V)for protein precipitation,while infused liquors were diluted 100-fold with acetonitrile,followed by centrifugation,and filtration by a 0.22-μm membrane.Chromatographic separation was carried out on an EC-C18 column using gradient elution with the mixture of 10 mmol/L ammonium acetate and 0.2%formic acid as mobile phase A and acetonitrile as mobile phase B.With this method,all the analytes were separated within 9.5 min.The samples were detected in positive ESI mode with dynamic multiple reaction monitoring(MRM)and quantified via external standard calibration.The results showed that the concentrations of the analytes in the range of 2-1000 ng/mL had excellent linearity(R2>0.9992)with the peak area.The developed method was successfully used for detection of 21 kinds of aconitum alkaloids,with limits of detection of 0.5-2 ng/mL,quantification limits of 2-6 ng/mL,intra/inter-day precision≤6.0%,spiked recoveries of 89.4%-100.9%,extraction recoveries of 74.2%-104.4%,and matrix effects ranging from-11.1%to 9.2%in blood/urine.The method was applied to detection of 12 samples from 4 fatal aconite poisoning cases,and all 21 kinds of ATS with total alkaloid concentrations of 0.04-4.18 μg/mL in blood and 154.96-422.83 μg/mL in medicinal liquors were detected.Tissue distribution revealed that the order of concentrations from highest to lowest is as follows:urine(157.22 μg/mL)>gastric contents(51.37 μg/mL)>kidney(21.6 μg/g)>whole blood(4.18 μg/mL)>liver(0.03 μg/g).This method showed many advantages such as simple pretreatment,low detection limits,accurate quantification,broad analyte coverage,and superior anti-interference capability in complex matrices,proving ideal for forensic and toxicological analysis of aconitum alkaloids.
6.Guided by National Strategic Needs,Striving to Build a First-Class Forensic Medicine Discipline—The Construction Plan for Forensic Medicine at Southern Medical University
Dong-Fang QIAO ; Ping-Ming QIU ; Qi WANG ; Yun-Chun TAI ; Dong-Ri LI ; Jing-Tao XU ; Qi-Zhi LUO ; En-Ping HUANG ; Bo-Feng ZHU
Journal of Forensic Medicine 2025;41(1):15-19
The 2024 National Education Work Conference pointed out that at the current juncture of the critical period for achieving the goals and tasks of the 14th Five-Year Plan,the implementation of the Education Powerhouse Construction Plan Outline should be taken as the main line of work,and building first-class disciplines is an crucial task for a higher education powerhouse.In 2022,forensic medicine was officially listed as a first-level discipline under the medical category,presenting an un-precedented historical opportunity for the development of forensic medicine.The forensic medicine dis-cipline of Southern Medical University comprehensively improves the quality of talent cultivation and facilitates the construction of first-class disciplines as its main direction.It aims to initiate and imple-ment a high-level faculty team building plan featuring"combining recruitment and cultivation,inter-disciplinary integration";make vigorous efforts to establish a first-level doctoral program,refine advan-tageous second-level disciplines and research directions;and establish an innovative research platform from a high starting point with deep integration.The discipline adheres to moral cultivation and the Five Domains of Education simultaneous development,to build a high-quality talent joint training model.Guided by the construction of the national legal system and industry needs,the discipline will enhance social service capabilities.The forensic medicine construction in our university will continue to contribute to the rule of law in China and educational power.
7.The Role of NEAT1 in Bone and Cartilage Metabolism and Bone Diseases
Rui-Ming WEN ; Rui-Qi HUANG ; Yi-Xing CHANG ; Ke XU ; Xue-Jie YI
Progress in Biochemistry and Biophysics 2025;52(4):930-945
In the process of maintaining the steady state of bone tissue, the transcription network and signal pathway of the body play a vital role. These complex regulatory mechanisms need precise coordination to ensure the balance between bone formation and bone absorption. Once this balance is broken, it may lead to pathological changes of bone and cartilage, and then lead to various bone diseases. Therefore, it is of great significance to understand these regulatory mechanisms for the prevention and treatment of bone diseases. In recent years, with the deepening of research, more and more lncRNA has been found to be closely related to bone health. Among them, nuclear paraspeckle assembly transcript 1 (NEAT1), as an extremely abundant RNA molecule in mammalian nuclei, has attracted extensive attention. NEAT1 is mainly transcribed from a specific site in human chromosome 11 by RNA polymerase II (RNaseP), which can form two different subtypes NEAT1_1 and NEAT1_2. These two subtypes are different in intracellular distribution and function, but they participate in many biological processes together. Studies have shown that NEAT1 plays a specific role in the process of cell growth and stress response. For example, it can regulate the development of osteoblasts (OB), osteoclasts (OC) and chondrocytes by balancing the differentiation of bone marrow mesenchymal stem cells (BMSCs), thus maintaining the steady state of bone metabolism. This discovery reveals the important role of NEAT1 in bone development and remodeling. In addition, NEAT1 is closely related to a variety of bone diseases. In patients with bone diseases such as osteoporosis (OP), osteoarthritis (OA) and osteosarcoma (OS), the expression level of NEAT1 is different. These differential expressions may be closely related to the pathogenesis and progression of bone diseases. By regulating the level of NEAT1, it can affect a variety of signal transduction pathways, and then affect the development of bone diseases. For example, some studies show that by regulating the expression level of NEAT1, the activity of osteoclasts can be inhibited, and the proliferation and differentiation of osteoblasts can be promoted, thus improving the symptoms of osteoporosis. It is worth noting that NEAT1 can also be used as a key sensor for the prevention and treatment of bone diseases. When exercising or receiving some natural products, the expression level of NEAT1 will change, thus reflecting the response of bones to external stimuli. This feature makes NEAT1 an important target for studying the prevention and treatment strategies of bone diseases. However, although the role of NEAT1 in bone biology and bone diseases has been initially recognized, its specific mechanism and regulatory relationship are still controversial. For example, the expression level, mode of action and interaction with other molecules of NEAT1 in different bone diseases still need further in-depth study. This paper reviews the role of NEAT1 in maintaining bone and cartilage metabolism, and discusses its expression and function in various bone diseases. By combing the existing research results and controversial points, this paper aims to provide new perspectives and ideas for the prevention and treatment of bone diseases, and provide useful reference and enlightenment for future research.
8.Impact of antimicrobial volume-based procurement and classification manage-ment policy on the use of carbapenem antibiotics in Hunan Province
Zehua WU ; Junyu CHEN ; Linyong XU ; Yuxing MING ; Yusong ZHOU ; Xun HUANG ; Chenchao FU ; Zhaohui WANG ; Shikun LIU ; Zuojun LI
Chinese Journal of Infection Control 2025;24(1):105-112
Objective To explore the impact of antimicrobial volume-based procurement(VBP)and classification management policy on the clinical use of carbapenem antibiotics.Methods Changing trend in defined daily doses(DDDs),procurement cost(Cost),defined daily dose cost(DDDc),and DDDs per 1 000 inhabitants daily(DID)of carbapenem antibiotics in all levels of medical institutions were analyzed by Mann-Kendall trend test.May 1,2020 was taken as the intervention cut-off point of VBP policy,September 2021 was as intervention cut-off point of cla-ssification management list.The impact of VBP and classification management policy on the clinical use of carbape-nem antibiotics were studied by interrupted time series analysis.Results After implementing VBP policy,the DDDs and DID of carbapenem antibiotics increased obviously,but the long-term trend didn't change significantly.Compared with before the implementation of the policy,the cost and DDDc of carbapenem antibiotics decreased im-mediately,the long-term trend of DDDc changed significantly,but the long-term trend of cost didn't change signifi-cantly.The DDDs and Cost of carbapenem antibiotics decreased immediately after the update of classification ma-nagement list,but the long-term downward trend was not significant,and DDDc presented a long-term upward trend.Conclusion VBP policy reduces the DDDc and short-term cost of carbapenem antibiotics,but its long-term impact on DDDs,cost and DID is limited.Classification management has limited impact on the use of carbapenem antibiotics in medical institutions.
9.Malignancy risk assessment and cause analysis of the Bethesda class Ⅰ/Ⅲ cytolo-gy diagnosis due to insufficient cell volume in thyroid solid nodule
Hongzhen YU ; Ming LI ; Xiang XIE ; Xiaofeng LAN ; Tianyu XU ; Shan HUANG ; Xian WANG ; Zhenzhong FENG
Chinese Journal of Clinical and Experimental Pathology 2025;41(1):44-50
Purpose To investigate the incidence and risk of malignancy(ROM)of the Bethesda class Ⅰ/Ⅲ di-agnosis of thyroid nodules due to insufficient number of follicular cells,and to analyze the correlation between their in-sufficient cell volume and the characteristics of the nodules themselves from the perspective of ultrasound and histology.Methods Clinical data were collected from fine needle aspiration cytology(FNAC)of the thyroid gland.Review and statistical analysis was performed on cases with the Bethesda class Ⅰ/Ⅲ diagnosis due to insufficient cell volume.The incidence and the ROM of Bethesda class Ⅰ/Ⅲ diagnosis were calculated.BRAF V600E(+)or postoperative patho-logical indicating papillary thyroid carcinoma(PTC)was used as the criterion for malignancy.Then,we matched the Bethesda class Ⅱ/Ⅵ cases with sufficient cell volume as the control group.The ultrasound characteristics and histo-logical images of the two groups were compared and analyzed in order to reveal the correlation between the insufficient amount of penetrating cells and the objective characteristics of the nodule itself.Results There were 39 solid thyroid nodules with the Bethesda class Ⅰ diagnosis,with an incidence of 3.3%and a ROM of 38.5%,and 160 nodules with the Bethesda class Ⅲ diagnosis,with an incidence of 13.5%and a ROM of 59.4%.The incidence and ROM of nod-ules with C-TIRADS ≥4b(22.4%,67.6%)were higher than those of C-TIRADS ≤4a(12.7%,39.8%),and the differences were statistically significant(P<0.001).Compared to the Bethesda class Ⅱ/Ⅵ nodules with sufficient cell volume,occurrence of the Bethesda class Ⅰ/Ⅲ nodules were significantly correlated with small nodules(maximal diameter<5 mm),vertical growth(aspect ratio ≥ 1)and poor blood supply(no or little blood flow signals)(r=0.131,-0.230,0.237,P=0.008,<0.001,<0.001).They were also significantly correlated with the pathologic histologic structure of diffuse significant fibrosis of the interstitium and low parenchyma/interstitium composition ratio(about 1:1)(r=-0.269,-0.396,P=0.019,<0.001).Conclusion Thyroid Bethesda class Ⅰ/Ⅲ nodules have a high ROM,and BRAF V600E detection is recommended as a tool of tiered management.Bethesda class Ⅰ/Ⅲ diagnosis of insufficient cell volume is more likely when the nodules are too small,grow vertically and lack blood sup-ply,presumably associated with extensive interstitial fibrosis and sparse parenchymal cells.
10.Novel Structural Features of Isoflavone Synthase from Medicago truncatula Shed Light on Its Unique Enzymatic Mechanism
Chao SHI ; Zhao-Yang YE ; Fei XU ; Xiang-Ning DU ; Zhang-Xin CHEN ; Ming-Yue GU ; Jie DENG ; Wei WANG ; Liang-Yu LIU ; Mei-Ying WANG ; Xiao-Dong SU ; He-Li LIU ; Ming-Ying SHANG ; Li-Xin HUANG ; Zhen-Zhan CHANG
Chinese Journal of Biochemistry and Molecular Biology 2025;41(8):1204-1213,中插1-中插6
Isoflavones which mainly distributed in leguminous plants have plenty of health benefits.Isoflavone synthase(IFS)is a membrane-associated cytochrome P450 enzyme(CYP450)which carries out the unique aryl-ring migration and hydroxylation.So far,few crystal structures of plant P450s have been obtained.We determined the crystal structure of IFS from Medicago truncatula at 1.9 ? by MAD method using a selenomethionine substituted crystal and conducted molecular docking and mutagenesis study.The structure of IFS complexed with imidazole exhibits the helix Ⅰa-loop-helix Ⅰβ motif which cor-responds to helix Ⅰ of other P450s.Compared with structures of common P450s,IFS/imidazole structure contains an extra domain,i.e.,the γ-domain.The structure reveals a homodimer in which the γ-domain of one molecule interacts with the β-domain of another.The plane of heme group makes an angle of ap-proximately 40° with the helix Ⅰa-loop-helix Ⅰβ motif.Molecular docking combined with mutagenesis study suggested that Trp-128 and Asp-300 might play important roles in substrate binding and recogni-tion.Phe-301,Ser-303 and Gly-305 from the helix Ⅰa-loop-helix Ⅰβ motif may play important roles in the aryl-ring migration.These novel structural features reveal insights into the unique reaction mechanism of IFS and provide a basis for engineering IFS in leguminous crops for health purpose.

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