1.Noninvasive Screening for Chronic Atrophic Gastritis Using Photoplethysmography-derived Meridian-labelled Harmonic Parameters
Yun-Qing LE ; Jian-Xin CHEN ; Ai-Ping CHEN ; Zhi-Hong LI
Progress in Biochemistry and Biophysics 2026;53(5):1178-1194
ObjectiveChronic atrophic gastritis (CAG) is usually diagnosed by gastroscopy and histopathological biopsy. These procedures remain the reference standard, but their invasive nature and resource requirements may limit their use in large-scale population screening and repeated follow-up. A convenient and reproducible method for noninvasive auxiliary screening may help identify individuals who require further endoscopic assessment. Fingertip photoplethysmography (PPG) provides a noninvasive recording of peripheral pulse waves and allows harmonic features to be extracted from the signal. In this study, the so-called meridian-related variables were defined as PPG-derived harmonic parameters labelled according to meridian nomenclature, rather than as direct measurements of meridian physiology. This study aimed to compare these harmonic parameters between patients with CAG and non-CAG controls, identify parameters that remained different after age adjustment, and develop a multivariable model for noninvasive auxiliary screening and pre-endoscopic risk stratification of CAG. MethodsA total of 343 participants were included, comprising 171 patients with CAG and 172 non-CAG controls. CAG diagnosis was established using gastroscopy and histopathology as the reference standard. Fingertip PPG signals were collected using a PPG-based pulse acquisition device. Eight PPG-derived harmonic parameters labelled according to meridian nomenclature were extracted for analysis. Between-group differences were first assessed using nonparametric tests. Age-adjusted analyses were then performed to reduce potential confounding by age. The false discovery rate (FDR) method was applied for multiple-comparison correction. A multivariable logistic regression model integrating age and multiple harmonic parameters was constructed. Model performance was evaluated using receiver operating characteristic (ROC) analysis and the area under the curve (AUC). Internal validation performance was assessed using stratified five-fold cross-validation and bootstrap optimism correction. Threshold performance was examined using both a high-specificity strategy and a Youden index-based cutoff. Decision curve analysis was used to evaluate the model’s net clinical benefit across a range of threshold probabilities. ResultsAll eight harmonic parameters were non-normally distributed. In the univariate analysis, the stomach-labelled harmonic parameter (ST), bladder-labelled harmonic parameter (BL), and liver-labelled harmonic parameter (LR) differed between the CAG and non-CAG groups. After age adjustment and FDR correction, only ST and BL remained statistically significant. Compared with non-CAG controls, patients with CAG showed higher ST values and lower BL values. This finding indicates an associated differential harmonic pattern that was not fully explained by age distribution. However, the discriminative ability of a single harmonic parameter was limited. The best-performing single indicator was ST, with an AUC of 0.652 (95% CI: 0.595-0.707). The multivariable model integrating age and multiple harmonic parameters achieved an AUC of 0.791 (95% CI: 0.743-0.835), representing an improvement of 0.139 over ST alone. In internal validation, stratified five-fold cross-validation yielded a mean AUC of 0.753 (95% CI: 0.715-0.781), and the bootstrap optimism-corrected AUC was 0.748. These results suggest that the model retained moderate discriminative performance after internal validation.At a specificity of at least 95%, the model achieved a sensitivity of only 40.4% (95% CI: 25.7%-49.7%). This high-specificity cutoff may be suboptimal as the preferred threshold for an initial screening setting because of the potential risk of missed CAG cases. The Youden index-based optimal cutoff was 0.419, corresponding to a sensitivity of 80.7% and a specificity of 62.8%. This threshold may better match the practical aim of noninvasive auxiliary screening, where sensitivity is usually prioritized to reduce missed cases. Decision curve analysis showed that, within a threshold probability range of 10%-55%, the model provided higher net clinical benefit than the reference strategies of recommending gastroscopy for all participants or for none. ConclusionPatients with CAG showed associated harmonic differences in fingertip PPG-derived features, mainly characterized by higher ST and lower BL values after age adjustment and FDR correction. Compared with a single harmonic parameter, the multivariable model showed better overall discrimination and retained moderate internal validation performance. These findings suggest that PPG-derived harmonic parameters labelled according to meridian nomenclature may provide auxiliary information for noninvasive auxiliary screening and front-line triage before gastroscopic confirmation in CAG. The present results support further validation rather than immediate clinical implementation. External validation in independent, multicenter, and preferably prospective screening cohorts is needed to assess the model’s generalizability, screening performance, and potential clinical utility.
2.Noninvasive Screening for Chronic Atrophic Gastritis Using Photoplethysmography-derived Meridian-labelled Harmonic Parameters
Yun-Qing LE ; Jian-Xin CHEN ; Ai-Ping CHEN ; Zhi-Hong LI
Progress in Biochemistry and Biophysics 2026;53(5):1178-1194
ObjectiveChronic atrophic gastritis (CAG) is usually diagnosed by gastroscopy and histopathological biopsy. These procedures remain the reference standard, but their invasive nature and resource requirements may limit their use in large-scale population screening and repeated follow-up. A convenient and reproducible method for noninvasive auxiliary screening may help identify individuals who require further endoscopic assessment. Fingertip photoplethysmography (PPG) provides a noninvasive recording of peripheral pulse waves and allows harmonic features to be extracted from the signal. In this study, the so-called meridian-related variables were defined as PPG-derived harmonic parameters labelled according to meridian nomenclature, rather than as direct measurements of meridian physiology. This study aimed to compare these harmonic parameters between patients with CAG and non-CAG controls, identify parameters that remained different after age adjustment, and develop a multivariable model for noninvasive auxiliary screening and pre-endoscopic risk stratification of CAG. MethodsA total of 343 participants were included, comprising 171 patients with CAG and 172 non-CAG controls. CAG diagnosis was established using gastroscopy and histopathology as the reference standard. Fingertip PPG signals were collected using a PPG-based pulse acquisition device. Eight PPG-derived harmonic parameters labelled according to meridian nomenclature were extracted for analysis. Between-group differences were first assessed using nonparametric tests. Age-adjusted analyses were then performed to reduce potential confounding by age. The false discovery rate (FDR) method was applied for multiple-comparison correction. A multivariable logistic regression model integrating age and multiple harmonic parameters was constructed. Model performance was evaluated using receiver operating characteristic (ROC) analysis and the area under the curve (AUC). Internal validation performance was assessed using stratified five-fold cross-validation and bootstrap optimism correction. Threshold performance was examined using both a high-specificity strategy and a Youden index-based cutoff. Decision curve analysis was used to evaluate the model’s net clinical benefit across a range of threshold probabilities. ResultsAll eight harmonic parameters were non-normally distributed. In the univariate analysis, the stomach-labelled harmonic parameter (ST), bladder-labelled harmonic parameter (BL), and liver-labelled harmonic parameter (LR) differed between the CAG and non-CAG groups. After age adjustment and FDR correction, only ST and BL remained statistically significant. Compared with non-CAG controls, patients with CAG showed higher ST values and lower BL values. This finding indicates an associated differential harmonic pattern that was not fully explained by age distribution. However, the discriminative ability of a single harmonic parameter was limited. The best-performing single indicator was ST, with an AUC of 0.652 (95% CI: 0.595-0.707). The multivariable model integrating age and multiple harmonic parameters achieved an AUC of 0.791 (95% CI: 0.743-0.835), representing an improvement of 0.139 over ST alone. In internal validation, stratified five-fold cross-validation yielded a mean AUC of 0.753 (95% CI: 0.715-0.781), and the bootstrap optimism-corrected AUC was 0.748. These results suggest that the model retained moderate discriminative performance after internal validation.At a specificity of at least 95%, the model achieved a sensitivity of only 40.4% (95% CI: 25.7%-49.7%). This high-specificity cutoff may be suboptimal as the preferred threshold for an initial screening setting because of the potential risk of missed CAG cases. The Youden index-based optimal cutoff was 0.419, corresponding to a sensitivity of 80.7% and a specificity of 62.8%. This threshold may better match the practical aim of noninvasive auxiliary screening, where sensitivity is usually prioritized to reduce missed cases. Decision curve analysis showed that, within a threshold probability range of 10%-55%, the model provided higher net clinical benefit than the reference strategies of recommending gastroscopy for all participants or for none. ConclusionPatients with CAG showed associated harmonic differences in fingertip PPG-derived features, mainly characterized by higher ST and lower BL values after age adjustment and FDR correction. Compared with a single harmonic parameter, the multivariable model showed better overall discrimination and retained moderate internal validation performance. These findings suggest that PPG-derived harmonic parameters labelled according to meridian nomenclature may provide auxiliary information for noninvasive auxiliary screening and front-line triage before gastroscopic confirmation in CAG. The present results support further validation rather than immediate clinical implementation. External validation in independent, multicenter, and preferably prospective screening cohorts is needed to assess the model’s generalizability, screening performance, and potential clinical utility.
3.Effects of Liangxue Heying Formula-medicated serum on the activation of LPS-induced human umbilical vein endothelial cells via JAK2/STAT3 signaling pathway
Chun-lan XIA ; Xia FENG ; Ye-min CAO ; Zhi-qiang LIANG ; Yi LE ; Hong-tao XU ; Fei QI ; Ji LI
Chinese Traditional Patent Medicine 2025;47(4):1150-1156
AIM To investigate the effects of Liangxue Heying Formula-medicated serum(LXHY-MS)on human umbilical vein endothelial cells(HUVECs)induced by lipopolysaccharide(LPS).METHODS CCK-8,DCFH-DA fluorescence probe and Western blot method were used to screen the LPS concentration in modeling and the serum LXHY concentration for treatment.The HUVECs divided into the normal group,the model group and the LXHY-MS group had their SOD activity detected by automatic biochemical analyzer;their MDA level detected by colorimetry;their protein expressions of ICAM-1,VCAM-1,IL-6,TNF-α,p-JAK2 and p-STAT3 detected by Western blot;and their mROS expression and recruitment effect on THP-1 photographed with high connotation.With the use of JAK2/STAT3 pathway inhibitor(AG490),the HUVECs divided into the normal group,the AG490 group,the LPS group,the LPS+AG490 group,the LPS+LXHY-MS group,and LPS+LXHY-MS+AG490 group were subjected to the corresponding treatment,followed by the detection of their protein expressions of ICAM-1,VCAM-1,IL-6,TNF-α,p-JAK2 and p-STAT3 by Western blot.RESULTS Compared with the normal group,the model group displayed decreased SOD activity(P<0.01),increased MDA level(P<0.05),increased ICAM-1,VCAM-1,IL-6,TNF-α,p-JAK2,p-STAT3 protein expressions(P<0.05,P<0.01),and increased mROS expression and THP-1 cells recruitment.Compared with the model group,the LXHY-MS group shared increased SOD activity(P<0.05),decreased MDA level(P<0.01),decreased ICAM-1,VCAM-1,IL-6,TNF-α,p-JAK2,p-STAT3 protein expressions(P<0.05,P<0.01),reduced mROS expression and THP-1 cells recruitment.Given the use of AG490,the model group displayed increased protein expressions of ICAM-1,VCAM-1,IL-6,TNF-α,p-JAK2 and p-STAT3 in contrast to the normal group(P<0.05,P<0.01);each intervened group showed decreased expressions of related proteins in contrast to the model group(P<0.05,P<0.01).CONCLUSION LXHY-MS may protect the injury due to the activation of HUVECs by inhibiting the JAK2/STAT3 signaling pathway.
4.In vitro fluorescent substrate assay for the activity of leucine aminopeptidase(LAP)in Echinococcus multilocularis
Jia-yu CHEN ; Yao DAI ; Shun-juan WANG ; Yang XIAO ; Xin-zong YAN ; Tong LIU ; Zhi-hao YUAN ; Kai-li SHI ; Run-le LI ; Feng TANG
Chinese Journal of Zoonoses 2025;41(1):23-31
This study was aimed at developing an in vitro fluorescent substrate assay for the activity of leucyl aminopeptid-ase(LAP)from Echinococcus multilocularis and comparing it with the chemical chromogenic substrate enzyme activity assay.Through the establishment of reaction conditions for the fluorescent substrate-based in vitro enzyme activity assay,we com-pared the differences between the fluorescent substrate L-Leucine-7-amido-4-methylocoumarin(Leu-AMC)and the chemical chromogenic substrate L-Leucine-4-nitroanilide(Leu-pNA)through molecular docking,inhibition rates,and precision measures.Molecular docking revealed that the fluorescent substrate Leu-AMC had higher affinity for the protein than the chemical chromogenic substrate Leu-pNA.Through analysis of the effects of varying reaction conditions on fluorescence intensi-ty,we optimized the fluorescent substrate enzyme activity assay to demonstrate favorable performance at a reaction temperature of 37℃,a pH of 9.0,a protein concentration of 800 nmol/L,and a reaction duration of 60 minutes.Leu-AMC exhibited significant and distinct responses at a 5 μmol/L substrate concentration,under varying substrate conditions.The fluo-rescent substrate assay demonstrated more significant intergroup differences than the chemical chromogenic substrate assay when various inhibitors were added.This study established a fluorescence-based enzyme activity assay for leucyl aminopeptidase from Echinococcus multilocularis by using Leu-AMC as the substrate;this method demonstrated a more significant intergroup difference and sensitivity than the chemical chromogenic substrate assay.
5.Applied value of physical motor function assessment system in the risk assessment of recruit training injury
Wei WEI ; Wei-Xu ZHANG ; Lv-Gang ZHU ; Liang TANG ; Huan-Le LI ; Zhi-Chao XUE ; Liang ZHANG ; Hao-Feng WANG ; Qi CHANG
Medical Journal of Chinese People's Liberation Army 2025;50(5):531-535
Objective To assess the effectiveness of the evaluation of military physical function(EMPF)system in predicting the occurrence of military training injuries among new recruits to provide scientific guidance and methodological choice for military training.Methods A total of 527 new recruits from 5 grassroots units from July 2016 to February 2018 were selected for the study.The recruits underwent EMPF testing,and their military training injuries were monitored over a 2-year follow-up period.Those who sustained injuries during training were divided into injury group(n=163),while the remaining recruits were placed in healthy group(n=364).The predictive ability of the total EMPF score for training injuries was assessed using the receiver operating characteristic curve(ROC),and the correlation between the total EMPF score,individual test scores,and military training injuries were analyzed using binary logistic regression.Results The total EMPF score of new recruits in injury group(19.52±1.97)was significantly lower than that of healthy group(24.31±1.54)(P<0.001),which also demonstrated a high diagnostic value in predicting the risk of military training injuries,with an area under the curve(AUC)of ROC of 0.971(P<0.001).A cut-off value of 22 scores was found to have the highest accuracy in predicting future training injuries,with an odds ratio(OR)of 25.63,sensitivity of 0.939,specificity of 0.879,positive likelihood ratio of 7.76,and a post-test probability of 0.67.Binary logistic regression analysis revealed that 6 EMPF tests,including holding the ball over and leaning back,bending forward and touching the ground with the ball,lunge squat and twist,swallow balance with holding the ball afterward,vertical jump,and respiratory pattern assessment,were negatively associated with the risk of military training injuries(P<0.0001).Conclusion The EMPF system can effectively predict the risk of military training injuries,with military personnel whose total EMPF score is less than 22 being at higher risk of sustaining such injuries.
6.Establishment and validation of a predictive model for increased drainage volume after open transforaminal lumbar interbody fusion
Yin HU ; Hai-long YU ; Hong-wen GU ; Kang-en HAN ; Shi-lei TANG ; Yuan-hang ZHAO ; Zhi-hao ZHANG ; Jun-chao LI ; Le XING ; Hong-wei WANG
Journal of Regional Anatomy and Operative Surgery 2025;34(11):981-986
Objective To analyze the risk factors for increased drainage volume after open transforaminal lumbar interbody fusion(TLIF),and to establish a predictive model and then validate it.Methods The clinical data of 680 patients who underwent open TLIF at the General Hospital of Northern Theater Command from January 2016 to December 2019 were collected and the patients were randomly divided into the training group(n=476)and the validation group(n=204).Taking the predictive factors screened out by LASSO regression analysis as independent variables,a multivariate Logistic regression predictive model was constructed.The model was internally validated through the receiver operating characteristic(ROC)curve,Hosmer-Lemeshow goodness-of-fit test,and calibration curve,and its clinical utility was assessed via decision curve analysis(DCA).Results LASSO regression analysis screened out four predictive variables:age,number of surgical segments,operative duration,and intraoperative blood loss.The multivariate Logistic regression predictive model demonstrated that age≥60 years,number of surgical segments≥4,operative duration≥2 hours,and intraoperative blood loss≥200 mL were independent influencing factors for the increased postoperative drainage volume in patients undergoing TLIF(P<0.05).ROC curve analysis revealed an area under the curve(AUC)of 0.816(95%CI:0.798 to 0.867)in the training group and 0.783(95%CI:0.685 to 0.823)in the validation group,indicating that the predictive model had good discriminatory ability.Additionally,the Hosmer-Lemeshow goodness-of-fit test and calibration curve indicated that the predictive model had a good degree of fit,and the predicted probability was basically consistent with the actual probability,demonstrating a good calibration.The DCA results confirmed that this predictive model could be applied in clinical practice.Conclusion The risk factors for increased drainage volume after open TLIF include age,number of surgical segments,operative duration,and intraoperative blood loss.The predictive model established based on these factors demonstrates good performance,and it can be applied in clinical guidance for the selection of drainage tube removal time after TLIF.
7.Establishment and validation of a predictive model for increased drainage volume after open transforaminal lumbar interbody fusion
Yin HU ; Hai-long YU ; Hong-wen GU ; Kang-en HAN ; Shi-lei TANG ; Yuan-hang ZHAO ; Zhi-hao ZHANG ; Jun-chao LI ; Le XING ; Hong-wei WANG
Journal of Regional Anatomy and Operative Surgery 2025;34(11):981-986
Objective To analyze the risk factors for increased drainage volume after open transforaminal lumbar interbody fusion(TLIF),and to establish a predictive model and then validate it.Methods The clinical data of 680 patients who underwent open TLIF at the General Hospital of Northern Theater Command from January 2016 to December 2019 were collected and the patients were randomly divided into the training group(n=476)and the validation group(n=204).Taking the predictive factors screened out by LASSO regression analysis as independent variables,a multivariate Logistic regression predictive model was constructed.The model was internally validated through the receiver operating characteristic(ROC)curve,Hosmer-Lemeshow goodness-of-fit test,and calibration curve,and its clinical utility was assessed via decision curve analysis(DCA).Results LASSO regression analysis screened out four predictive variables:age,number of surgical segments,operative duration,and intraoperative blood loss.The multivariate Logistic regression predictive model demonstrated that age≥60 years,number of surgical segments≥4,operative duration≥2 hours,and intraoperative blood loss≥200 mL were independent influencing factors for the increased postoperative drainage volume in patients undergoing TLIF(P<0.05).ROC curve analysis revealed an area under the curve(AUC)of 0.816(95%CI:0.798 to 0.867)in the training group and 0.783(95%CI:0.685 to 0.823)in the validation group,indicating that the predictive model had good discriminatory ability.Additionally,the Hosmer-Lemeshow goodness-of-fit test and calibration curve indicated that the predictive model had a good degree of fit,and the predicted probability was basically consistent with the actual probability,demonstrating a good calibration.The DCA results confirmed that this predictive model could be applied in clinical practice.Conclusion The risk factors for increased drainage volume after open TLIF include age,number of surgical segments,operative duration,and intraoperative blood loss.The predictive model established based on these factors demonstrates good performance,and it can be applied in clinical guidance for the selection of drainage tube removal time after TLIF.
8.The neurophysiological mechanisms of exercise-induced improvements in cognitive function.
Jian-Xiu LIU ; Bai-Le WU ; Di-Zhi WANG ; Xing-Tian LI ; Yan-Wei YOU ; Lei-Zi MIN ; Xin-Dong MA
Acta Physiologica Sinica 2025;77(3):504-522
The neurophysiological mechanisms by which exercise improves cognitive function have not been fully elucidated. A comprehensive and systematic review of current domestic and international neurophysiological evidence on exercise improving cognitive function was conducted from multiple perspectives. At the molecular level, exercise promotes nerve cell regeneration and synaptogenesis and maintains cellular development and homeostasis through the modulation of a variety of neurotrophic factors, receptor activity, neuropeptides, and monoamine neurotransmitters, and by decreasing the levels of inflammatory factors and other modulators of neuroplasticity. At the cellular level, exercise enhances neural activation and control and improves brain structure through nerve regeneration, synaptogenesis, improved glial cell function and angiogenesis. At the structural level of the brain, exercise promotes cognitive function by affecting white and gray matter volumes, neural activation and brain region connectivity, as well as increasing cerebral blood flow. This review elucidates how exercise improves the internal environment at the molecular level, promotes cell regeneration and functional differentiation, and enhances the brain structure and neural efficiency. It provides a comprehensive, multi-dimensional explanation of the neurophysiological mechanisms through which exercise promotes cognitive function.
Animals
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Humans
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Brain/physiology*
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Cognition/physiology*
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Exercise/physiology*
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Nerve Regeneration/physiology*
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Neuronal Plasticity/physiology*
9.Effects of Liangxue Heying Formula-medicated serum on the activation of LPS-induced human umbilical vein endothelial cells via JAK2/STAT3 signaling pathway
Chun-lan XIA ; Xia FENG ; Ye-min CAO ; Zhi-qiang LIANG ; Yi LE ; Hong-tao XU ; Fei QI ; Ji LI
Chinese Traditional Patent Medicine 2025;47(4):1150-1156
AIM To investigate the effects of Liangxue Heying Formula-medicated serum(LXHY-MS)on human umbilical vein endothelial cells(HUVECs)induced by lipopolysaccharide(LPS).METHODS CCK-8,DCFH-DA fluorescence probe and Western blot method were used to screen the LPS concentration in modeling and the serum LXHY concentration for treatment.The HUVECs divided into the normal group,the model group and the LXHY-MS group had their SOD activity detected by automatic biochemical analyzer;their MDA level detected by colorimetry;their protein expressions of ICAM-1,VCAM-1,IL-6,TNF-α,p-JAK2 and p-STAT3 detected by Western blot;and their mROS expression and recruitment effect on THP-1 photographed with high connotation.With the use of JAK2/STAT3 pathway inhibitor(AG490),the HUVECs divided into the normal group,the AG490 group,the LPS group,the LPS+AG490 group,the LPS+LXHY-MS group,and LPS+LXHY-MS+AG490 group were subjected to the corresponding treatment,followed by the detection of their protein expressions of ICAM-1,VCAM-1,IL-6,TNF-α,p-JAK2 and p-STAT3 by Western blot.RESULTS Compared with the normal group,the model group displayed decreased SOD activity(P<0.01),increased MDA level(P<0.05),increased ICAM-1,VCAM-1,IL-6,TNF-α,p-JAK2,p-STAT3 protein expressions(P<0.05,P<0.01),and increased mROS expression and THP-1 cells recruitment.Compared with the model group,the LXHY-MS group shared increased SOD activity(P<0.05),decreased MDA level(P<0.01),decreased ICAM-1,VCAM-1,IL-6,TNF-α,p-JAK2,p-STAT3 protein expressions(P<0.05,P<0.01),reduced mROS expression and THP-1 cells recruitment.Given the use of AG490,the model group displayed increased protein expressions of ICAM-1,VCAM-1,IL-6,TNF-α,p-JAK2 and p-STAT3 in contrast to the normal group(P<0.05,P<0.01);each intervened group showed decreased expressions of related proteins in contrast to the model group(P<0.05,P<0.01).CONCLUSION LXHY-MS may protect the injury due to the activation of HUVECs by inhibiting the JAK2/STAT3 signaling pathway.
10.In vitro fluorescent substrate assay for the activity of leucine aminopeptidase(LAP)in Echinococcus multilocularis
Jia-yu CHEN ; Yao DAI ; Shun-juan WANG ; Yang XIAO ; Xin-zong YAN ; Tong LIU ; Zhi-hao YUAN ; Kai-li SHI ; Run-le LI ; Feng TANG
Chinese Journal of Zoonoses 2025;41(1):23-31
This study was aimed at developing an in vitro fluorescent substrate assay for the activity of leucyl aminopeptid-ase(LAP)from Echinococcus multilocularis and comparing it with the chemical chromogenic substrate enzyme activity assay.Through the establishment of reaction conditions for the fluorescent substrate-based in vitro enzyme activity assay,we com-pared the differences between the fluorescent substrate L-Leucine-7-amido-4-methylocoumarin(Leu-AMC)and the chemical chromogenic substrate L-Leucine-4-nitroanilide(Leu-pNA)through molecular docking,inhibition rates,and precision measures.Molecular docking revealed that the fluorescent substrate Leu-AMC had higher affinity for the protein than the chemical chromogenic substrate Leu-pNA.Through analysis of the effects of varying reaction conditions on fluorescence intensi-ty,we optimized the fluorescent substrate enzyme activity assay to demonstrate favorable performance at a reaction temperature of 37℃,a pH of 9.0,a protein concentration of 800 nmol/L,and a reaction duration of 60 minutes.Leu-AMC exhibited significant and distinct responses at a 5 μmol/L substrate concentration,under varying substrate conditions.The fluo-rescent substrate assay demonstrated more significant intergroup differences than the chemical chromogenic substrate assay when various inhibitors were added.This study established a fluorescence-based enzyme activity assay for leucyl aminopeptidase from Echinococcus multilocularis by using Leu-AMC as the substrate;this method demonstrated a more significant intergroup difference and sensitivity than the chemical chromogenic substrate assay.

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