[Research progress of vaccination status, efficacy and safety in children with tumor]

Malignant tumors in children are one of the most important diseases that threaten the health and quality of life of children and are the second most common cause of death in children.With the continuous improvement and progress of treatment technology, the long-term survival rate of children with tumor has been significantly improved, but both the disease itself and the treatment can impair the immune function of children, which makes them vulnerable to various infectious diseases and secondary serious complications, and even become a source of infection, endangering the health of others. Vaccination is the most cost-effective measure to prevent infectious diseases. For children with normal immune functions, the benefits of vaccination usually outweigh the disadvantages. However, there is a lack of detailed data on the vaccination situation, efficacy and safety of vaccine use for such immunocompromised tumor survivors, and there are no authoritative and uniform vaccination recommendations. This article reviewed and summarized the literature and consensus of some domestic and foreign scholars on current status of post-treatment vaccination status, efficacy and safety of vaccination for children with tumors after treatment, with the aim of providing a reference for the practice in this field in China.

[Research progress in the promotion of peri-implant soft tissue integration of dental titanium implant based on immune microenvironment regulation]

A good integration of dental implants and the surrounding soft tissue is essential to ensure the long-term effect of implant. In this review, we summarized the research progress of peri-implant soft tissue integration of dental titanium implants, with emphasis on the modification of the gingival interface of implants based on immune microenvironment regulation. This method influences the immune response around the implant by promoting the surface properties of implants, so as to enhance the peri-implant soft tissue integration. The purpose of this review is to provide reference for the related research and clinical application in the field of dental implantation.

[Effectiveness of 13-valent pneumococcal conjugate vaccine against invasive disease caused by serotype 19A in children: a meta-analysis]

Objective: Using Meta-analysis to evaluate the vaccine effectiveness of 13-valent pneumococcal conjugate vaccine (PCV13) against invasive Streptococcus pneumoniae disease (IPD) caused by serotype 19A in children <5 years old. Methods: "Streptococcus pneumoniae infection""invasive pneumococcal disease""13-valent pneumococcal polysaccharide conjugate vaccine""PCV13""effectiveness""infant""child" and related terms were searched from China National Knowledge Infrastructure (CNKI), WANFANG DATA, PubMed, SCOPUS and Web of science with no limited on language, region and research institution. The retrieval time was limited from January 2010 to February 2023 and cohort study, case-control study and randomized controlled trial were included. Data were extracted from eligible studies by two independent reviewers, and after study quality assessment by NOS scale, Meta-analysis was completed using Stata 16.0 software. Results: A total of 2 340 related literatures were searched, and 10 literatures were finally included, including 5 case-control studies and 5 indirect cohort studies, which showed good literature quality. The vaccine effectiveness against serotype 19A IPD of PCV13 in children was 83.91% (95%CI: 78.92%-88.89%), and the subgroup analysis (P=0.240) showed there was no significant difference among the case-control study (VE=87.34%, 95%CI:79.74%-94.94%) and the indirect cohort study (VE=81.30%, 95%CI:74.69%-87.92%). The funnel plot and Egger test suggested that the possibility of publication bias was small. Conclusion: The present evidence indicates that PCV13 has a good vaccine effectiveness against serotype 19A IPD in children, and it is recommended to further increase the vaccination rate of PCV13 to reduce the disease burden of IPD in children <5 years old.

[Study of the predictive role of serum HBV RNA on HBeAg serological conversion in children with chronic hepatitis B]

Objective: To investigate the role of serum hepatitis B virus RNA (HBV RNA) in predicting HBeAg serological conversion in children with chronic hepatitis B. Methods: 175 children aged 1~17 years with chronic hepatitis B who received interferon α (IFNα) for 48 weeks were selected. Patients were divided into HBeAg seroconversion and non-conversion based on whether HBeAg seroconversion occurred at 48 weeks of treatment.T-test and Mann-Whitney U test were used to compare between groups; chisquare test or Fisher exact probability method was used to compare the frequency between groups of classified variables; and Pearson correlation was used to analyze the correlation between indicators. Univariate and multivariate logistic regression analyses were used to identify influencing factors associated with HBeAg serological conversion. The predictive effect of HBV RNA, HBV DNA, and HBsAg on HBeAg serological conversion was compared and analyzed by the receiver operating characteristic curve (ROC). Results: The seroconversion rate of HBeAg at 48 weeks was 36.0% (63/175). The reduction in HBVRNA levels from baseline to the 12th, 24th, 36th, and 48th weeks of antiviral therapy was significantly greater in the HBeAg serological conversion group than that in the non-conversion group, and the difference was statistically significant between the two groups (P < 0.05). Univariate and multivariate regression analyses showed that age and a decline in HBV RNA levels at week 12 were independent predictors of HBeAg serological conversion. The area under the ROC curve (AUROC) of HBV RNA decline at week 12 was 0.677(95% CI∶0.549-0.806, P = 0.012), which was significantly better than the same period of AUROC of HBV DNA (0.657, 95% CI∶0.527-0.788, P = 0.025) and HBsAg (0.660, 95% CI∶0.526-0.795, P = 0.023) decline. HBV RNA levels decreased (>1.385 log10 copies/ml) at week 12, with a positive predictive value of 53.2%, a negative predictive value of 72.2%, a sensitivity of 77.4%, and a specificity of 57.9% for HBeAg seroconversion. Conclusion: HBV RNA level lowering during the 12th week of antiviral therapy can serve as an early predictor marker for HBeAg serological conversion in children with chronic hepatitis B.

[Application progress of implementation research on diabetes management]

Diabetes is one of the most important non-communicable chronic diseases. Although a large amount of clinical evidence on the effectiveness of diabetes prevention and treatment interventions has been established, the current quality of care and results are still insufficient. Implementation Research can bridge the gap between research and practice. Implementation Research on diabetes management can clarify what is effective and what is ineffective in management, and promote the transformation of complex, multi-component interventions into medical practice faster and more effectively. This paper reviews the main research contents and application of implementation research of diabetes management at home and abroad, aiming to provide reference for related research and promote the application of implementation research in diabetes management in China.

[Prognostic factors for non-small cell lung cancer patients with central nervous system metastasis with positive driver genes]

Objective: To investigate the prognostic factors of patients with central nervous system (CNS) metastatic non-small cell lung cancer (NSCLC) with positive driver genes. Methods: The clinical data of 103 patients with CNS metastatic NSCLC admitted to Beijing Tongren Hospital from January 2016 to December 2020 were retrospectively analyzed, and the patients were divided into positive driver gene group (patients with driver genes mutation and receiving corresponding targeted therapy) and negative driver gene group. Cox univariate and multivariate regression analyses were performed to identify the factors affecting patients' prognosis, and the receiver operating characteristic curve (ROC) was used to compare the predictive ability of 4 scoring systems [recursive partitioning analysis (RPA) classes, diagnosis-specific graded prognostic assessment (DS-GPA) index, basic score for brain metastasesn (BS-BM) and (lung-molecular graded prognostic assessment (lung-mol GPA)]on patients' prognosis. Results: Among the 103 patients, 48 were males and 55 were females, and aged (64.6±9.7) years old. The median survival time of the 103 patients was 24.0 (95%CI: 20.0-28.0) months, the median survival time of the 59 patients in the positive driver gene group was 33.0 (95%CI: 23.4-42.6) months, the median survival time of the 44 patients in the negative driver gene group was 17.0 (95%CI: 14.4-19.6) months, and the difference was statistically significant (χ²=24.69, P<0.001). The results of Cox multivariate analysis showed that the negative driver genes (HR=3.788, 95%CI: 1.951-7.301, P=0.001), Karnofsky performance status (KPS) score<70 (HR=2.613, 95%CI: 1.185-5.761, P=0.017) and neutrophil-to-lymphocyte ratio (NLR)>3.22 (HR=2.714, 95%CI: 1.157-6.365, P=0.022) were independent risk factors affecting the prognosis of patients with CNS metastatic NSCLC. KPS score<70 (HR=3.719, 95%CI: 1.165-11.876, P=0.027) and no radiotherapy (HR=2.032, 95%CI: 1.033-11.364, P=0.041) were independent risk factors affecting the prognosis of patients with CNS metastatic NSCLC with positive driver genes. ROC curve analysis showed that the area under curve (AUC) value of lung-mol GPA was the highest among the 4 scoring systems (AUC=0.843, 95%CI: 0.731-0.956, P<0.001), and the AUC value of the lung-mol GPA combined scoring system (AUC=0.904, 95%CI: 0.816-0.991, P<0.001) was higher than lung-mol GPA. Conclusions: A low KPS score and no cranial radiation therapy are independent risk factors for the prognosis of patients with CNS metastatic NSCLC with positive driver genes; the lung-mol GPA joint scoring system is more conducive to the prognostic assessment of patients with CNS metastatic NSCLC with positive driver genes.

[The sleep condition and its association with cognitive function of the elderly in six provinces of China]

Objective: To analyze the association between sleep duration and cognitive function of the elderly in six provinces of China. Methods: Based on the cross-sectional survey data of the elderly from the Healthy Ageing Assessment Cohort Study in 2019, 4 644 participants' sociodemographic and economic indicators, lifestyle, prevalence of major chronic diseases, and sleep status, including night-time sleep duration, daytime sleep duration and insomnia, were collected by questionnaires. Cognitive function was evaluated by the Mini-Mental State Examination. Multivariate logistic regression was used to analyze the association between night-time sleep duration, daytime sleep duration and cognitive function. Results: The mean age of 4 644 respondents was (72.3±5.7) years, and 2 111 of them were males (45.5%). The mean total daily sleep time of the elderly was (7.9±1.9) hours, and the proportion of those who slept less than 7.0, 7.0-8.9 and≥9.0 hours was 24.1% (1 119), 42.1% (1 954) and 33.8% (1 571), respectively. The mean sleep time at night was (6.9±1.7) hours. About 23.7% (1 102) of the elderly did not sleep during the day, and the mean duration of the elderly who slept during the day was (78±51) minutes. Among the elderly with insomnia, 47.9% were still satisfied with their sleep quality. The mean value of MMSE score of 4 644 respondents was (24.5±5.3), and the cognitive impairment rate was 28.3% (1 316). The results of multivariate logistic regression model analysis showed that the OR (95%CI) value of the risk of cognitive impairment in older people who did not sleep, slept for 31 to 60 minutes and slept more than one hour was 1.473 (1.139 to 1.904), 1.277 (1.001 to 1.629) and 1.496 (1.160 to 1.928), respectively, compared with those who slept for 1 to 30 minutes during the daytime. Compared with those who slept for 7.0‒8.9 hours at night, the OR (95%CI) value of the risk of cognitive impairment in older people who slept more than 9.0 hours was 1.239 (1.011 to 1.519). Conclusion: The cognitive function is related to sleep duration in the Chinese elderly.

Development of a hardened THz energy meter for use on the kilojoule-scale, short-pulse OMEGA EP laser

A highly adaptable and robust terahertz (THz) energy meter is designed and implemented to detect energetic THz pulses from high-intensity (>10¹⁸ W/cm²) laser-plasma interactions on the OMEGA EP. THz radiation from the laser driven target is detected by a shielded pyrometer. A second identical pyrometer is used for background subtraction. The detector can be configured to detect THz pulses in the 1 mm to 30 μm (0.3- to 10-THz) range and pulse energies from joules to microjoules via changes in filtration, aperture size, and position. Additional polarization selective filtration can also be used to determine the THz pulse polarization. The design incorporates significant radiation and electromagnetic pulse shielding to survive and operate within the OMEGA EP radiation environment. We describe the design, operational principle, calibration, and testing of the THz energy meter. The pyrometers were calibrated using a benchtop laser and show linear sensitivity to up to 1000 nJ of absorbed energy. The initial results from four OMEGA EP THz experiments detected up to ∼15μJ at the detector, which can correspond to hundreds of mJ depending on THz emission and reflection models.

Molecular mechanism and therapeutic potential of YiQi FuMai injection in acute heart failure

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): The National Science Foundation for Distinguished Young Scholars of China

Background

 Acute heart failure (AHF) is a significant public health problem related to the high mortality and rehospitalization rate of patients. Although drug development is never interrupted, no single drug has been proven to play a decisive role in improving the survival of AHF patients. In China, multi-component traditional Chinese medicine has been widely used to treat AHF. As a Chinese herbal injection included in medical insurance, Yiqi Fumai Injection can reduce the level of NT-proBNP in AHF patients, improve heart function, and alleviate symptoms and signs related to heart failure. To further evaluate the therapeutic effect of Yiqi Fumai Injection on AHF, a multi-center, double-blind, randomized controlled trial that intends to recruit 1270 patients is being carried out in China. However, the mechanism of Yiqi Fumai Injection in the treatment of AHF has not been clarified. To further explore the underlying mechanism, we used systematic pharmacology methods to explore the potential molecular mechanisms of biologically active compounds.

Methods

 We used the databases of HERB, the Encyclopedia of Traditional Chinese Medicine (ETCM), the Comparative Toxicogenomics Database (CTD), Online Mendelian Inheritance in Man (OMIM), and GeneCards to predict the active ingredients and potential targets of Yiqi Fumai Injection in the treatment of AHF. STRING was used for PPI network construction and analysis. Cytoscape was used to build a network between Chinese medicine, ingredients and targets. The DAVID, GO, and KEGG databases were used to predict the potential pathways of Yiqi Fumai Injection for the treatment of AHF.

Results

 We obtained 31 active compounds of Yiqi Fumai Injection from HERB and ECTM databases. By overlapping targets between YQFMI and AHF, a total of 240 potential targets for Yiqi Fumai Injection to treat AHF were selected. According to the H-C-T network topology analysis, the core compounds include beta-sitosterol, Uridine, Guanosine, and Stigmasterol. Sixteen protein targets had significantly higher node degrees than the average in the PPI network, including AKT1, JUN, TNF, EDN1, CASP3, ESR1, DLG4, PTGS2, NOS3, IL1B, C3, AR, LEP, CNR1, CHRM2, and DRD2. The PPI results showed that the potential therapeutic targets of YQFMI were densely enriched in pathways related to endothelial function, neuromodulation, and lipid metabolism.The same results were shown in GO and KEGG pathway enrichment.

Conclusion

 Our results indicate that Yiqi Fumai Injection may achieve the goal of improving AHF-related symptoms by regulating the function of vascular endothelium and nerves and the biosynthetic pathway of lipid metabolism. These findings support previous studies and provide a reference for studying the mechanism of Yiqi Fumai Injection in the treatment of AHF. Abstract Figure.

[Prediction of 6-year risk of activities of daily living disability in elderly aged 65 years and older in China]

Objective: To construct an easy-to-use risk prediction tool for 6-year risk of activities of daily living(ADL) disability among Chinese elderly aged 65 and above. Methods: A total of 34 349 elderly aged 65 and above were recruited from the Chinese Longitudinal Healthy Longevity Survey. Demographic characteristics, lifestyle and chronic diseases of the elderly were collected through face-to-face interviews. The functional status of the elderly was evaluated by the instrumental activities of daily living(IADL) scale. The mental health status of the elderly was evaluated by the Mini-Mental State Examination. The height, weight, blood pressure and other information of the subjects were obtained through physical examination and body mass index(BMI) was calculated. The ADL status was evaluated by Katz Scale at baseline and follow-up surveys. Taking ADL status as the dependent variable and the key predictors were selected from Lasso regression as the independent variables, a Cox proportional risk regression model was constructed and visualized by the nomogram tool. Area under the receiver operating characteristic curve(AUC) and calibration curve were used to evaluate the discrimination and calibration of the model. A total of 200 bootstrap resamples were used for internal validation of the model. Sensitivity analysis was used to evaluate the robustness of the model. Results: The M(Q₁, Q₃) of subjects' age as 86(75, 94) years old, of which 9 774(46.0%) were males. A total of 112 606 person-years were followed up, 4 578 cases of ADL disability occurred and the incidence density was 40.7/1 000 person-years. Cox proportional risk regression model analysis showed that older age, higher BMI, female, hypertension and history of cerebrovascular disease were associated with higher risk of ADL disability [HR(95%CI) were 1.06(1.05-1.06), 1.05(1.04-1.06), 1.17(1.10-1.25),1.07(1.01-1.13) and 1.41(1.23-1.62), respectively.]; Ethnic minorities, walking 1 km continuously, taking public transportation alone and doing housework almost every day were associated with lower risk of ADL disability [HR(95%CI): 0.71(0.62-0.80), 0.72(0.65-0.80), 0.74(0.68-0.82) and 0.69(0.64-0.74), respectively]. The AUC value of the model was 0.853, and the calibration curve showed that the predicted probability was highly consistent with the observed probability. After excluding non-intervening factors(age, sex and ethnicity), the AUC value of the model for predicting the risk of ADL disability was 0.779. The AUC values of 65-74 years old and 75 years old and above were 0.634 and 0.765, respectively. The AUC values of the model based on walking 1 km continuous and taking public transport alone in IADL and the model based on comprehensive score of IADL were 0.853 and 0.851, respectively. Conclusion: The risk prediction model of ADL disability established in this study has good performance and robustness.

[Study on the establishment of regional healthy aging promotion index]

Objective: To establish an index that can reflect the level of healthy aging promotion in a region. Methods: Establish an indicators system using expert consultation and then determine the weight for each indicator using the analytic hierarchy process. Finally, we can get the regional healthy aging promotion index. Results: Regional healthy aging promotion indicator system was established, including five first-level indicators (residence environment, medical service, public health, nurse and care, and supporting system) and 21 second-level indicators. The weight of every level-one indicator ranges from 0.073 to 0.346. Two indicators with the highest weight are residence environment and public health (0.346 and 0.325, respectively), while the indicator with the lowest weight is nurse and care (0.073). The importance of every level-two indicator ranges from 0.011 to 0.162. The consistency ratio of the regional healthy aging promotion index is 0.021, and the consistency test is qualified. Conclusion: Regional healthy aging promotion index established in this study is very scientific, reasonable, and applicable. It can be used to evaluate the region's situation or level of healthy aging promotion.

The Benefits of Physical Activity and Positive Mental Health for Reducing the Burden of COVID-19: Validation from a Cross-sectional and Longitudinal Investigation in China and Germany

Many people experience high burden by the outbreak of the coronavirus disease (COVID-19) and its consequences for health and everyday life. The present cross-national study investigated potential factors that can reduce the burden by COVID-19 in China and Germany. Cross-sectional and longitudinal (China: N = 474, baseline, BL: 2015, follow-up, FU: 2020; Germany: N = 359, BL: 2019, FU: 2020) data on physical activity (e.g., jogging) (BL/FU), positive mental health (PMH) (BL/FU), and burden by COVID-19 (FU) were collected via online surveys. In both countries, physical activity was positively associated with PMH, and both variables were negatively related to burden by COVID-19. Furthermore, PMH mediated the link between physical activity and burden. The mediation model was significant when physical activity and PMH were assessed at the BL, while burden was measured at the FU; and it was also significant when all variables were assessed at the FU. The present findings reveal that physical activity in combination with PMH can reduce the experience of burden by COVID-19. Conscious fostering of physical activity and PMH is supported as an effective strategy to reduce the negative impact of the pandemic outbreak on mental and physical health. Additional benefits such as increased adherence to governmental measures around COVID-19 are discussed.

Mitochondrial DNA Polymorphism in Zhejiang She Population Based on Next Generation Sequencing

Abstract

Objective To study the genetic polymorphism of whole mitochondrial DNA （mtDNA） genomes in She population in Zhejiang and to explore the maternal genetic structure of the She population. Methods Whole mtDNA genomes of 231 unrelated individuals from She population in Zhejiang Province were sequenced. The number of mutations and population genetics parameters such as, the haplotype diversity （HD）, discrimination power （DP）, and random match probabilities （RMP） were analyzed. The mtDNA haplogroups of Zhejiang She population were classified, and the maternal genetic relationships between She and nine other Chinese populations were estimated. Results In 231 Zhejiang She samples, 8 507 mutations （702 types） were observed and the samples were classified into 94 haplogroups. The HD, DP and RMP values were 0.998 6, 0.994 2 and 0.005 8, respectively. The lowest genetic differentiation degree （F_st=0.006 89） was detected between Zhejiang She population and southern Han population. Principal component analysis （PCA） and median-joining network analysis showed that the genetic distance of Zhejiang She population with Guangxi Yao, Yunnan Dai and Southern Han populations was relatively close, but the population still had some unique genetic characteristics. Conclusion The whole mtDNA genomes are highly polymorphic in Zhejiang She population. The Zhejiang She population contains complex and diverse genetic components and has a relatively close maternal genetic relationship with Guangxi Yao, Yunnan Dai and Southern Han populations. Meanwhile, Zhejiang She population has kept its unique maternal genetic components.

[Influence of SARS-CoV-2 vaccination on the epidemiological and clinical characteristics of imported COVID-19 cases in Chengdu]

Objective: To analyze the epidemiological and clinical characteristics of imported COVID-19 cases after SARS-CoV-2 vaccination and to provide evidence for the prevention and control of COVID-19. Methods: The imported COVID-19 cases in Chengdu as of April 15, 2021 were divided into the vaccinated group and unvaccinated group according to the history of SARS-CoV-2 vaccination. The epidemiological and clinical data of the cases were collected retrospectively, and the differences in epidemiological and clinical characteristics of the two groups were compared. Laboratory tests consisted of nucleic acid test, clinical index test, serum antibody test and lymphocyte test. Software WPS2019 was used for data management and software R 4.0.3 was used for statistical analysis. Results: A total of 75 COVID-19 cases were included in the analysis, in which 20 had received SARS-CoV-2 vaccination and only 4 with clinical symptoms, 55 patients did not receive SARS-CoV-2 vaccination, and 16 had clinical symptoms. In vaccinated group, the first injection time of vaccination ranged from July to November 2020, and 10 cases received two doses of vaccine simultaneously and 10 cases received two doses of vaccine at intervals of 14-57 days. The intervals between the completion of vaccination and the onset ranged from 87 days to 224 days. The differences in classification and clinical type between the two groups were significant. Significant differences were observed in case classification and clinical type between vaccinated group and unvaccinated group (P<0.05). The vaccinated group had a relatively high proportion of asymptomatic infections (40.00%, 8/20), while mild infections were mainly observed in the unvaccinated group(76.36%,42/55). The differences in Ct values (ORF1ab gene and N gene) at the diagnosis were not significant between vaccinated group and unvaccinated group (P>0.05), similar results were also observed in lymphocyte subtypes, procalcitonin and C-reactive protein level comparisons. Serum amyloid A level was higher in unvaccinated group than in vaccinated group (P<0.05). However, the SARS-CoV-2 related serum antibody of IgM, IgG and total antibody levels were significantly higher in vaccinated group (P<0.05). Conclusions: Risk of infection still exists with SARS-CoV-2 after vaccination, which can facilitate the production of specific serum antibody of IgM and IgG when people are exposed to the virus. It has a certain protective effect on SARS-CoV-2 infected persons. Vaccination can reduce the clinical symptoms and mitigate disease severity.

Identification of Cannabis Sativa L. Based on rbcL Sequence

Abstract

Objective To assess the feasibility of the rbcL sequence of chloroplast DNA as a genetic marker to identify Cannabis sativa L. Methods The rbcL sequences in 62 Cannabis sativa L. samples, 10 Humulus lupulus samples and 10 Humulus scandens DNA samples were detected, and 96 rbcL sequences of the Cannabaceae family were downloaded from Genbank. Sequence alignment was performed by MEGA X software, the intraspecific and interspecific Kimura-2-Parameter （K2P） genetic distances were calculated, and the system clustering tree was constructed. Results The rbcL sequence length acquired by sequencing of Cannabis sativa L. and Humulus scandens were 617 bp and 649 bp, respectively, and two haplotypes of Cannabis sativa L. were observed in the samples. The BLAST similarity search results showed that the highest similarity between the sequences acquired by sequencing and Cannabis sativa L. rbcL sequences available from Genbank was 100%. The genetic distance analysis showed that the maximum intraspecific genetic distance （0.004 9） of Cannabis sativa L. was less than the minimum interspecific genetic distance （0.012 9）. The results of median-joining network and system clustering tree analysis showed that Cannabis sativa L. and other members of the Cannabaceae family were located in different branches. Conclusion The rbcL sequence could be used as a DNA barcode for identifying Cannabis sativa L., and combined with comparative analysis of the rbcL sequence and system cluster analysis could be a reliable and effective detection method for Cannabis sativa L. identification in forensic investigation.

[Urinary sodium, urine potassium and sodium-potassium ratio, and influencing factors of family cooks and family members in six regions of China]

Objective: To investigate the sodium intake, potassium intake, sodium- potassium ratio and influencing factors of family cooks and members in six regions of China. Methods: Using the multistage random sampling method, a total of 1 576 family cooks and their family members were recruited from 6 regions in China. Questionnaire survey and physical examination were conducted to collect basic information. 24 h urine was collected to test 24 h urinary sodium and potassium levels. Results: After excluding unqualified urine samples, a total of 1 530 people were included in the study. For all participants, 24 h urine sodium value was (4.39±1.93) g, 24 h urine potassium value was (1.59±0.62) g and sodium-potassium ratio was 5.02±2.18. 24 h urinary sodium was negatively correlated with age, female, junior high school education or above, and annual family income (P<0.05), and positively correlated with perceived salty taste, BMI and SBP (P<0.05). The 24 h urine potassium value was negatively correlated with eating out almost everyday (P<0.05), but positively correlated with BMI and unwillingness to reduct salt (P<0.05). The sodium-potassium ratio was negatively correlated with age, female and junior high school education or above annual family income (P<0.05), and positively correlated with perceived salty taste, SBP and eating out 3-5 d/week (P<0.05). Conclusions: The 24 h urinary sodium value and sodium potassium ratio of family cooks and family members in six regions of China are still at high level, while the 24 h urine potassium value is low, with multiple factors. Therefore, it is necessary to carry out long-term comprehensive salt reduction intervention for family cooks and their members.

Structure and mechanism of the human NHE1-CHP1 complex

Sodium/proton exchanger 1 (NHE1) is an electroneutral secondary active transporter present on the plasma membrane of most mammalian cells and plays critical roles in regulating intracellular pH and volume homeostasis. Calcineurin B-homologous protein 1 (CHP1) is an obligate binding partner that promotes NHE1 biosynthetic maturation, cell surface expression and pH-sensitivity. Dysfunctions of either protein are associated with neurological disorders. Here, we elucidate structures of the human NHE1-CHP1 complex in both inward- and inhibitor (cariporide)-bound outward-facing conformations. We find that NHE1 assembles as a symmetrical homodimer, with each subunit undergoing an elevator-like conformational change during cation exchange. The cryo-EM map reveals the binding site for the NHE1 inhibitor cariporide, illustrating how inhibitors block transport activity. The CHP1 molecule differentially associates with these two conformational states of each NHE1 monomer, and this association difference probably underlies the regulation of NHE1 pH-sensitivity by CHP1.

[Depression symtoms and related factors of fire fighters]

Objective: To analysis the status of the mental health and related factors of fire fighters in Tianjin Binhai New District, and to provide suggestions for their psychological health protection. Methods: 399 fire fighters in Tianjin Binhai New District were selected as study subjects in Jan to April 2019. Depression symptoms were measured by the depression module of the Patient Health Questionnaire (PHQ-9) . The Chinese version of Efrort Reword Imbalance (ERI) Questionnnaire were used to investigate and evaluate their occupational stress. Chi-Square test was used to analysis Categorical data. Binary logistic regression model was used to analysis the ralated factors of depression. Results: Among the 399 fire fighters, 71.1% (280/394) were found high level of depression symptom. The detection rates of depression symptoms in the related influceing factors ERI、station、disease、life pressure、eating habits and sleep disorder occupational stress were difierent (P<0.05) . Sleep disorder, life pressure and ERI occupational stress were risk factors for depressive symptoms (OR=1.921, 95% CI=1.002-3.682; OR=2.852, 95% CI=1.561-5.212; OR=2.367, 95% CI=1.163-4.818, P<0.05) . Conclusion: The rate of depression of fire fighters is relatively higher. Government should pay attention to and take measures to improve the psychological condition of fire fighters.

Cysteine-based crosslinking approach for characterization of oligomeric pore-forming proteins in the mitochondrial membranes

Mitochondria are important not only to healthy but also dying cells. In particular, apoptotic cell death initiates when the mitochondrial outer membrane is permeabilized by Bax, a protein of the Bcl-2 family. Bax shares a structural fold with some α-helical bacterial pore-forming toxins before these proteins actively engage membranes. Despite decades of intensive research, the structures of the pores formed by these proteins are mostly unknown, mainly because the pores are assembled by different numbers of the proteins whose conformation and interaction are highly dynamic. Site-specific crosslinking of the pore-forming proteins in cellular membranes where the pores are assembled is a powerful approach to assess the biological pore structure, dynamics and function. In this chapter, we describe a cysteine-based site-specific crosslinking protocol for the Bax protein in the mitochondrial membrane. We discuss the expected results and the resulting structural-functional models for the pore-forming Bax oligomer, in comparison with other crosslinking approaches that have been used to study other mitochondrial protein complexes. At the end, we highlight the advantages of the crosslinking approaches as well as the limitations and alternative approaches.

[Impact of transcatheter aortic valve replacement on renal function in patients with severe aortic stenosis]

Objective: To explore the impact of transcatheter aortic valve replacement (TAVR) on renal function in patients with severe aortic stenosis. Methods: This is a single-center retrospective study. Consecutive patients with severe aortic valve stenosis and received TAVR in Zhongshan Hospital from December 2014 to December 2019 were included. The patients were divided into four groups according to the estimate glomerular filtration rate (eGFR) measured at one day before TAVR, namely eGFR>90 ml·min-1·1.73m-2 group, 6090 ml·min-1·1.73m-2 group, 60 Collapse

Key Words

• Acute kidney recovery
• Aortic valve stenosis
• Renal function
• Transcatheter aortic valve implantation

Collapse

MESH Headings Collapse

Grants Collapse

Affiliation(s)

L F Yang Department of Cardiology, Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Fudan University, Shanghai 200032, China
X C Zhang Department of Cardiology, Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Fudan University, Shanghai 200032, China
Y Zhang Department of Cardiology, Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Fudan University, Shanghai 200032, China
S S Chen Department of Cardiology, Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Fudan University, Shanghai 200032, China
L H Guan Department of Cardiology, Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Fudan University, Shanghai 200032, China
W Z Pan Department of Cardiology, Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Fudan University, Shanghai 200032, China
D X Zhou Department of Cardiology, Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Fudan University, Shanghai 200032, China
J B Ge Department of Cardiology, Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Fudan University, Shanghai 200032, China

Collapse

[Association between lifestyle-related factors and colorectal adenoma]

Objective: To explore the association between lifestyle-related factors and colorectal adenoma. Methods: Based on the Screening Project of Early Diagnosis and Treatment of Colorectal Cancer in Jiashan county Zhejiang province, from August 2012 to March 2018, information gathered through records on questionnaire and colonoscopic diagnosis were collected from participants with positive results during the primary screening stage. According to the findings of colonoscopy, 11 232 controls without any colorectal diseases and 3 895 cases with colorectal adenoma were included in the study. Multivariate logistic regression models were used to analyze the association between lifestyle-related factors and colorectal adenoma. Results: After adjusting for possible confounding factors, results from multivariate logistic regression analysis showed that smoking, alcohol drinking and obesity were positively related to the risk of colorectal adenoma, with ORs (95%CIs) as 1.38 (1.24-1.54), 1.37 (1.24-1.51) and 1.38 (1.20-1.59) respectively. However, regular aspirin intake was negatively related with the risk of colorectal adenoma (OR=0.65, 95%CI: 0.53-0.80). After stratified by sex and age, data showed that the associations between smoking, alcohol drinking and colorectal adenoma were statistically significant in males, and the association between regular aspirin intake and colorectal adenoma was also statistically significant in older participants (aged 60 years and older). Conclusion: Smoking, alcohol drinking, regular aspirin intake and obesity were associated with colorectal adenoma.

Cryo-electron microscopy structure of human ABCB6 transporter

Human ATP-binding cassette transporter 6 of subfamily B (ABCB6) is an ABC transporter involved in the translocation toxic metals and anti-cancer drugs. Using cryo-electron microscopy, we determined the molecular structure of full-length ABCB6 in an apo state. The structure of ABCB6 unravels the architecture of a full-length ABCB transporter that harbors two N-terminal transmembrane domains which is indispensable for its ATPase activity in our in vitro assay. A slit-like substrate binding pocket of ABCB6 may accommodate the planar shape of porphyrins, and the existence of a secondary cavity near the mitochondrial intermembrane space side would further facilitate substrate release. Furthermore, the ATPase activity of ABCB6 stimulated with a variety of porphyrin substrates showed different profiles in the presence of glutathione (GSH), suggesting the action of a distinct substrate translocation mechanism depending on the use of GSH as a cofactor.

Cryo-electron microscopy structure of CLHM1 ion channel from Caenorhabditis elegans

Calcium homeostasis modulators (CALHMs/CLHMs) comprise a family of pore-forming protein complexes assembling into voltage-gated, Ca2+ -sensitive, nonselective channels. These complexes contain an ion-conduction pore sufficiently wide to permit the passing of ATP molecules serving as neurotransmitters. While their function and structure information is accumulating, the precise mechanisms of these channel complexes remain to be full understood. Here, we present the structure of the Caenorhabditis elegans CLHM1 channel in its open state solved through single-particle cryo-electron microscopy at 3.7-Å resolution. The transmembrane region of the channel structure of the dominant class shows an assembly of 10-fold rotational symmetry in one layer, and its cytoplasmic region is involved in additional twofold symmetrical packing in a tail-to-tail manner. Furthermore, we identified a series of amino acid residues critical for the regulation of CeCLHM1 channel using functional assays, electrophysiological analyses as well as structural-based analysis. Our structure and function analyses provide new insights into the mechanisms of CALHM channels.

Biological background of the genomic variations of cf-DNA in healthy individuals

BACKGROUND

Cell-free DNA (cf-DNA)-based liquid biopsy is emerging as a revolutionary new method in individualized cancer treatment and prognosis monitoring, although detecting early-stage cancers using cf-DNA remains challenging, partially because of the undefined biological background of cf-DNA.

MATERIALS AND METHODS

We investigated somatic mutations in the cf-DNA of 259 cancer-free individuals with a median age of 47 years using an endogenous barcoding duplex method with an ultralow base error rate (2 × 10-7) and compared the variant allele frequencies (VAFs) of these mutations between the cf-DNA and the corresponding blood cell DNA.

RESULTS

Sixty percent (155/259) of the samples showed at least one nonsynonymous mutation on either of two similar target panels covering 508 and 559 cancer-related genes. For individuals older than 50 years of age, the positive rate increased to 76%. Most cf-DNA mutations were also present at similar VAFs in the paired blood cell DNA. The most frequently mutated genes were driver genes of hematologic malignancies, including DNMT3A, TET2, AXSL1, and JAK2. However, the other 58.4% (192/329) of the mutations were likely 'passenger mutations' of clonal hematopoiesis, including mutations in NOTCH2, FAT3, EXT2, ERBB4, and ARID2, which are driver genes of solid tumors.

CONCLUSION

Hematopoietic clone-derived mutations, including 'driver mutations' and 'passenger mutations', are prevalent in the cf-DNA of both healthy individuals and cancer patients and may be a potential source of false positives in the liquid biopsy. Our results also suggest the ineffectiveness for distinguishing clonal hematopoietic mutations of low VAF (≤0.1%) from tumor-derived mutations using conventional next-generation sequencing of blood cell DNA. However, an error correction model with an ultralow error rate and high coverage depth is required for blood cell DNA sequencing, which is difficult and costly to achieve with current technologies.

Unique genetic profiles from cerebrospinal fluid cell-free DNA in leptomeningeal metastases of EGFR-mutant non-small-cell lung cancer: a new medium of liquid biopsy

Background

Leptomeningeal metastases (LM) are more frequent in non-small-cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutations. Due to limited access to leptomeningeal lesions, the purpose of this study was to explore the potential role of cerebrospinal fluid (CSF) as a source of liquid biopsy in patients with LM.

Patients and methods

Primary tumor, CSF, and plasma in NSCLC with LM were tested by next-generation sequencing. In total, 45 patients with suspected LM underwent lumbar puncture, and those with EGFR mutations diagnosed with LM were enrolled.

Results

A total of 28 patients were enrolled in this cohort; CSF and plasma were available in 26 patients, respectively. Driver genes were detected in 100% (26/26), 84.6% (22/26), and 73.1% (19/26) of samples comprising CSF cell-free DNA (cfDNA), CSF precipitates, and plasma, respectively; 92.3% (24/26) of patients had much higher allele fractions in CSF cfDNA than the other two media. Unique genetic profiles were captured in CSF cfDNA compared with those in plasma and primary tissue. Multiple copy number variations (CNVs) were mainly identified in CSF cfDNA, and MET copy number gain identified in 47.8% (11/23) of patients was the most frequent one, while other CNVs included ERBB2, KRAS, ALK, and MYC. Moreover, loss of heterozygosity (LOH) of TP53 was identified in 73.1% (19/26) CSF cfDNA, which was much higher than that in plasma (2/26, 7.7%; P < 0.001). There was a trend towards a higher frequency of concomitant resistance mutations in patients with TP53 LOH than those without (70.6% versus 33.3%; P = 0.162). EGFR T790M was identified in CSF cfDNA of 30.4% (7/23) of patients who experienced TKI progression.

Conclusion

CSF cfDNA could reveal the unique genetic profiles of LM and should be considered as the most representative liquid biopsy medium for LM in EGFR-mutant NSCLC.

[Effects of transcatheter aortic valve replacement in patients with severe aortic valve stenosis]

Objective: To investigate the effects of transcatheter aortic valve replacement (TAVR) in patients with severe aortic valve stenosis. Methods: The clinical data of 130 patients with severe aortic valve stenosis, who underwent TAVR in our hospital with self-expanding valve between January 1,2010 and October 30, 2016, were analyzed retrospectively. The patients were divided into calcific aortic valve stenosis (CAS) group (112 cases) and non-calcific aortic valve stenosis (NCAS) group (18 cases) according to 3D volume-rendering reconstruction under multiple detector computed tomography before TAVR. The baseline clinical features, imageology results, procedural details, and clinical prognosis were compared between the 2 groups. Results: (1) Compared with CAS group, the patients in NCAS group were younger, had higher proportion of rheumatic heart disease, and less proportion of bicuspid aortic valve morphology (P<0.01 or 0.05). Except for minimum value of sinotubular junction (P=0.017), there were no significant differences in multiple detector computed tomography measurements of aortic valve annulus and aortic root structure between the 2 groups (all P>0.05). (2) Compared with CAS group, the proportions of valve release under rapid pacing and oversized valve release were larger than pre-procedural evaluation, and the proportion of post-dilation was lower in NCAS group (P<0.01 or 0.05). (3) Post-procedural transthoracic echocardiography revealed that left ventricular ejection fraction was higher than baseline level in CAS group (P<0.001), while which was similar in NCAS group (P=0.552). Compared with before TAVR, mean pressure gradient and maximum transvalvular velocity were significantly reduced, aortic valve orifice area was significantly increased, and proportion of moderate to severe aortic regurgitation was significantly reduced after the procedure in both groups (all P<0.01). There were no significant differences in left ventricular ejection fraction, mean pressure gradient, maximum transvalvular velocity, aortic valve orifice area, and proportion of moderate to severe aortic regurgitation after TAVR between the 2 groups (all P>0.05). (4) There were no significant differences in successful rate of device placement and cardiovascular related death within 30 days after TAVR between the 2 groups (105/112 vs. 17/18, P=0.909; 3/112 vs. 1/18, P=0.453, respectively). Conclusion: TAVR is safe and effective for patients with severe aortic valve stenosis.

[Application and evaluation of urine measurement at different times methods for estimating salt intake]

Salt reduction is the most cost-effective population strategy to prevent and control hypertension and cardiovascular disease. Accurate measurement of salt intake is an important basis for implementing salt reduction interventions, while the urine sodium measurement is the most objective method to evaluate salt intake. According to different time spans, it is mainly divided into 24-h urine, overnight urine and spot urine collection methods. This article reviewed the application and evaluation of these three urine measurement methods, and compared their advantages and disadvantages. According to the accuracy and feasibility of different urine measurement methods, it is suggested that the 24-h urine collection method can be applied to the correlation study with small sample size, and the overnight urine method and the spot urine method can be applied to the daily population salt reduction interventions and monitoring activities.

Interplay between the electrostatic membrane potential and conformational changes in membrane proteins

Transmembrane electrostatic membrane potential is a major energy source of the cell. Importantly, it determines the structure as well as function of charge-carrying membrane proteins. Here, we discuss the relationship between membrane potential and membrane proteins, in particular whether the conformation of these proteins is integrally connected to the membrane potential. Together, these concepts provide a framework for rationalizing the types of conformational changes that have been observed in membrane proteins and for better understanding the electrostatic effects of the membrane potential on both reversible as well as unidirectional dynamic processes of membrane proteins.

[HBV genotyping based on key epitopes of PreS1 antigen and its correlation with genotyping by full-length PreS1 sequencing]

Objective: The aim was to investigate the genotype distribution of two major epitopes of large surface protein (PreS1) of hepatitis B in Chinese patients and to explore the association between the genotypes of these two epitopes, and to determine whether PreS1 full-length genotype could be revealed according to the polypeptide sequence of key epitopes. Methods: HBV DNA was extracted from the serum of patients for PCR amplification. 278 samples amplified successfully were sequenced and compared with the known HBV sequences in Genbank to determine the two key epitopes of HBV PreS1 genotype (amino acid epitope 21-47 and 94-117, abbreviated as P21 and P94) and PreS1 full-length genotypes. The correlation among three genotyping approaches was analyzed by Cohen's kappa coefficient to verify the consistency between the key-epitope genotyping and the full-length preS1 genotyping. Results: 232 samples were successfully sequenced. The genotyping based on the kind of P21 epitope protein sequence, 201 cases for genotype C, 23 cases for genotype B and 8 cases for uncertain genotypes and genotyping based on the form of P94 epitope protein sequence, 199 cases for genotype C, 25 cases for genotype B and 8 cases for indeterminate genotypes. Lastly, the genotyping based on sequence of the full-length PreS1 sequence, 207 and 25 cases for genotype C and B. P21 or P94 epitope genotyping and PreS1 full length genotyping were highly consistent, respectively, 96.55% and 96.12%, and the two epitopes (P21and P94) genotyping have parallel consistency (93.10%). Conclusion: In this study, an innovatively genotyping method based on the amino acid sequence of key epitopes was proposed. The genotypes of HBV in china were mainly B and C genotypes, and the genotypes of key conserved epitopes of HBV PreS1 were highly consistent with the full-length genotyping ( > 96%). Moreover, genotyping with one or two key epitopes can be used in place of the full-length genotyping.

[Safety and efficacy of transcatheter aortic valve replacement through transcarotid approach for patients with severe aortic valve stenosis]

Objective: To investigate the safety and efficacy of transcatheter aortic valve replacement(TAVR) through transcarotid approach for patients with severe aortic valve stenosis. Methods: The clinical data of 9 symptomatic severe aortic valve stenosis patients who had high or prohibitive risk for surgery and not suitable for TAVR through femoral artery access,and thus received TAVR through transcarotid approach in our hospital from November 2015 to February 2017 were retrospectively analyzed.The patients were followed up to observe the safety and efficacy of the procedure. Results: There were 4 male and 5 female patients in this cohort, and age was (75.7±8.7) years old. The Society of Thoracic Surgery (STS) scores were (7.9±1.6)%. All patients were treated by left carotid artery approach. One patient experienced valve dislodgement during the procedure and received surgery, and TAVR procedure was successful in the rest 8 patients. Two patients were implanted with permanent pacemaker because of third degree atrioventricular block during the procedure.One patient had cardiac arrest during the procedure and recovered after external chest compression.One patient developed severe carotid stenosis,and there was no clinical manifestation of nerve function deficit after the procedure. All patients were followed up at (30±3) days after the procedure, and there were no adverse events. The modified Rankin scale score was 0. Echocardiography examination showed that the tranvalvular mean gradient was reduced from (63.0±19.2)mmHg(1 mmHg=0.133 kPa) on baseline to (18.1±4.9)mmHg(P<0.001), 4 cases had mild paravalvular leakage, and there was no moderate or severe paravalvular leakage.The NYHA classes was significantly improved at 30 days when compared with before the procedure(2 cases class Ⅱ, 4 cases class Ⅲ,3 cases class Ⅳ before the procedure,and 5 cases classⅠ, 4 cases class Ⅱ after the procedure, P=0.006) , and left ventricular ejection fraction increased from (55.9±13.1)% to (60.4±10.0)% (P=0.030). Conclusion: Our initial experience indicates that transcarotid TAVR is safe and effective for patients with severe aortic valve stenosis.

[Percutaneous renal access for percutaneous nephrolithotomy guided by contrast enhanced ultrasound: a single-center preliminary experience in China]

OBJECTIVE

Contrast enhanced ultrasound (CEUS) is an innovative technique that employs microbubble contrast agents to demonstrate parenchymal perfusion. Ultrasound contrast agent was reported to be directly used in human internal lumen to improve the observation capacity of ultrasound. However, CEUS has never been reported to be used in the guidance of percutaneous renal access in percutaneous nephrolithotomy (PCNL). This study aimed to assess the efficacy of CEUS-guided renal access in PCNL.

METHODS

In this retrospective study, percutaneous renal access was performed under real-time monitoring of CEUS during PCNL in a cohort of 20 patients with renal stones at Peking University First Hospital. Data regarding patients' demographic and clinical characteristics, therapeutic regimens, and postoperative information were collected from a comprehensive database containing comprehensive medical records of the patients undergoing PCNL. Briefly, the procedure was as follows. With the patient under general anesthesia, renal access was established by the guidance of CEUS. Afterwords, holmium laser, pneumatic or ultrasonic lithotripsy was used by the same urologist. The patient demographics, stone characteristics and procedure details were noted. Finally, appropriate statistical analyses were performed to evaluate the effectiveness and safety of the CEUS-guided percutaneous renal access in PCNL.

RESULTS

All the 20 patients underwent PCNL successfully with the help of CEUS guidance for tract creation. The collecting system was successfully accessed in all the patients, and only one patient underwent re-puncture. All the patients approached through a middle-pole percutaneous access. The median puncture time was 3.9 (2.9-4.6) min, and the median operating time was 112 (98.5-134.5) min. The preliminary stone-free rate of PCNL was 95.0% (19/20) as shown by the kidney, ureter, and bladder (KUB) radiographs 48 h postoperation, and the median decline in hemoglobin level was 10 (5.5-14.5) g/L. Two patients had transient postoperative fever and responded well to antibiotics. In addition, no other major complications were observed.

CONCLUSION

CEUS is a safe and effective alternative way of guidance for percuta-neous renal access for PCNL beginners. It makes this procedure more visualized and simpler, and produces clearer images than common ultrasonic ones. PCNL beginners might benefit from this method to shorten the learning curve of PCNL, while it warrants further comparative studies to clarify.

Thermodynamic secrets of multidrug resistance: A new take on transport mechanisms of secondary active antiporters

Multidrug resistance (MDR) presents a growing challenge to global public health. Drug extrusion transporters play a critical part in MDR; thus, their mechanisms of substrate recognition are being studied in great detail. In this work, we review common structural features of key transporters involved in MDR. Based on our membrane potential-driving hypothesis, we propose a general energy-coupling mechanism for secondary-active antiporters. This putative mechanism provides a common framework for understanding poly-specificity of most-if not all-MDR transporters.

Energy coupling mechanisms of AcrB-like RND transporters

Prokaryotic AcrB-like proteins belong to a family of transporters of the RND superfamily, and as main contributing factor to multidrug resistance pose a tremendous threat to future human health. A unique feature of AcrB transporters is the presence of two separate domains responsible for carrying substrate and generating energy. Significant progress has been made in elucidating the three-dimensional structures of the homo-trimer complexes of AcrB-like transporters, and a three-step functional rotation was identified for this class of transporters. However, the detailed mechanisms for the transduction of the substrate binding signal, as well as the energy coupling processes between the functionally distinct domains remain to be established. Here, we propose a model for the interdomain communication in AcrB that explains how the substrate binding signal from the substrate-carrier domain triggers protonation in the transmembrane domain. Our model further provides a plausible mechanism that explains how protonation induces conformational changes in the substrate-carrier domain. We summarize the thermodynamic principles that govern the functional cycle of the AcrB trimer complex.

Structural dynamics of Giα protein revealed by single molecule FRET

The heterotrimeric G proteins (Gαβγ) act as molecular switches to mediate signal transduction from G protein-coupled receptors to downstream effectors. Upon interaction with an activated receptor, G protein exchanges its bound GDP with GTP, stimulating downstream signal transmission. Release of GDP requires a structural rearrangement between the GTPase domain and helical domain of the Gα subunit. Here, we used single molecule fluorescence resonance energy transfer (smFRET) technique to study the conformational dynamics of these two domains in the apo state and in the binding of different ligands. Direct imaging of individual molecules showed that the G_iα subunit is highly dynamic, and at least three major conformations of G_iα could be observed in the apo state. Upon binding of GDP, G_iα becomes dramatically less dynamic, resulting in a closed conformation between the two domains. We postulate that changes between the three conformations are sequential, and the three conformations appear to have distinct affinities toward GDP.

Crystal structure of E. coli apolipoprotein N-acyl transferase

In Gram-negative bacteria, lipid modification of proteins is catalysed in a three-step pathway. Apolipoprotein N-acyl transferase (Lnt) catalyses the third step in this pathway, whereby it transfers an acyl chain from a phospholipid to the amine group of the N-terminal cysteine residue of the apolipoprotein. Here, we report the 2.6-Å crystal structure of Escherichia coli Lnt. This enzyme contains an exo-membrane nitrilase domain fused to a transmembrane (TM) domain. The TM domain of Lnt contains eight TM helices which form a membrane-embedded cavity with a lateral opening and a periplasmic exit. The nitrilase domain is located on the periplasmic side of the membrane, with its catalytic cavity connected to the periplasmic exit of the TM domain. An amphipathic lid loop from the nitrilase domain interacts with the periplasmic lipid leaflet, forming an interfacial entrance from the lipid bilayer to the catalytic centre for both the lipid donor and acceptor substrates.