Temporal and spatial resolution of distal protein motions that activate hydrogen tunneling in soybean lipoxygenase.

The enzyme soybean lipoxygenase (SLO) provides a prototype for deep tunneling mechanisms in hydrogen transfer catalysis. This work combines room temperature X-ray studies with extended hydrogen-deuterium exchange experiments to define a catalytically-linked, radiating cone of aliphatic side chains that connects an active site iron center of SLO to the protein-solvent interface. Employing eight variants of SLO that have been appended with a fluorescent probe at the identified surface loop, nanosecond fluorescence Stokes shifts have been measured. We report a remarkable identity of the energies of activation (Ea) for the Stokes shifts decay rates and the millisecond C-H bond cleavage step that is restricted to side chain mutants within an identified thermal network. These findings implicate a direct coupling of distal protein motions surrounding the exposed fluorescent probe to active site motions controlling catalysis. While the role of dynamics in enzyme function has been predominantly attributed to a distributed protein conformational landscape, the presented data implicate a thermally initiated, cooperative protein reorganization that occurs on a timescale faster than nanosecond and represents the enthalpic barrier to the reaction of SLO.

Polarization fading suppression in distributed interferometric sensing by matched interference between polarization-switched pulses.

A polarization fading suppression technique is proposed for distributed interferometric sensing systems, based on matched interference between polarization switched pulses. For each individual sensor, two sets of interferometric outputs are obtained, one corresponding to the interference between two pulses with initially parallel polarization, the other corresponding to that between two pulses with initially orthogonal polarizations. As such, at least one output presents visibility no less than 2/2. By selecting the one with higher visibility for demodulation, the influence of polarization fading can be suppressed significantly, leading to distributed acoustic sensing with notably improved robustness and reliability.

Analysis on vaccine hesitation and its associated factors among parents of preschool children in Songgang Street, Shenzhen.

China has the largest number of vaccinated population around the world. However, there has been few research on the prevalence and associated factors of vaccine hesitation among parents of preschool children. Therefore, we conducted this study to evaluate the status of vaccine hesitation and its associated factors among children's parents. A cluster random sampling method was adopted to select six community health service centers in Shenzhen, and parents of preschool children who were immunized in the vaccination outpatient department of the selected community health centers were surveyed using a structured self-administered questionnaire. Vaccine hesitation was assessed by the Parent Attitudes about Childhood Vaccines (PACV) scale. A multiple linear regression analysis was used to assess the associated factors for vaccine hesitance among children's parents. A total of 1025 parents (response rate, 93.18%) filled out the questionnaires. The average score of vaccine hesitancy was 43.37 (SD = 10.34) points. 23.61% of parents wanted children to get all the recommended shots, 53.76% of them did not believe that many of the illnesses shots prevent were severe, and 75.41% of them could not guarantee the information they receive about shots. The results of multiple linear regression showed that the number of children in the family (ß = -0.93, 95% CI: -1.31 to 0.54), health status of the child (ß = 0.47, 95% CI: 0.07 to 0.87), education level of the parents (Father: ß = -0.84, 95%CI: -1.37 to 0.31; Mother: = -1.59, 95%CI:-2.13 to -1.05), and annual family income (ß = 1.64, 95%CI: 1.13-2.16) were significantly associated with vaccine hesitation. The average score of parents' vaccine hesitation in Shenzhen was 43.37. The results showed that the number of children in the family, health status of the children, education level of the parents and annual family income were important factors associated with the parents' vaccine hesitation.

Comparison of obesity indices and triglyceride glucose-related parameters to predict type 2 diabetes mellitus among normal-weight elderly in China.

PURPOSE: Although a significant proportion of type 2 diabetes mellitus (T2DM) cases arose from normal-weight individuals, studies on indicators of T2DM in normal-weight people are limited. Accordingly, this study aims to investigate the predictive value of obesity indices and triglyceride glucose-related parameters (TyG-related parameters) in T2DM among normal-weight Chinese elderly. METHODS: A total of 24,215 normal-weight Chinese elderly (age ≥ 60 years) [body mass index-BMI (18.5-23.9 kg/m2)] were included. Obesity indices and triglyceride glucose-related parameters (TyG-related parameters) included waist circumference (WC), waist-to-height ratio (WHtR), visceral adiposity index (VAI), lipid accumulation product (LAP), and TyG-related parameters (TyG, TyG-BMI, TyG-WC, and TyG-WHtR). Multivariate logistic regression analysis was performed to examine the associations between obesity- and TyG-related indices and T2DM. The areas under the curve (AUC) of the receiver-operating characteristic (ROC) curve analyses were used to evaluate and compare the predictive value of the different indices. RESULTS: The prevalence of T2DM was 14.2% in normal-weight individuals. Among the indices, TyG was significantly associated with T2DM among men and women, respectively, (adjusted odds ratio-aOR per SD 3.46; 95% CI 3.23-3.71) and (aOR per SD 3.64; 95% CI 3.43-3.86). Compared with other indices, TyG had the highest AUC value for T2DM in men (AUC: 0.818, 95% CI 0.810-0.825) and women (AUC: 0.824, 95% CI 0.814-0.833). CONCLUSIONS: TyG is an effective marker and outperforms other indices when predicting T2DM in the normal-weight Chinese elderly population. LEVEL OF EVIDENCE: Level V: Opinions of authorities, based on descriptive studies, narrative reviews, clinical experience, or reports of expert committees.

Effects of sacubitril/valsartan in patients with heart failure and chronic kidney disease: A meta-analysis.

Sacubitril/valsartan (LCZ696) is recommended for ejection fraction reduction in heart failure. However, studies comparing the effects of sacubitril/valsartan in patients with heart failure and chronic kidney disease (CKD) with the inhibitor of renal angiotensin system (RAS) are limited. To further demonstrate the benefits of sacubitril/valsartan in patients with both heart failure and CKD, a meta-analysis of randomized controlled trials (RCTs) was conducted. The Cochrane Library, PubMed, Web of Science and ClinicalTrials.gov were searched for RCTs. A total of 3460 individuals with heart failure and CKD were included in this meta-analysis. Sacubitril/valsartan was compared with irbesartan, valsartan and enalapril. It was found that sacubitril/valsartan significantly increased estimated glomerular filtration rate [eGFR, MD = 1.90, 95% CI (0.30, 3.50), P = 0.02]. However, sacubitril/valsartan had no difference in urinary albumin/creatinine ratio [UACR, MD = -0.30, 95% CI (-1.38, 0.78), P = 0.59] compared to the control group. Sacubitril/valsartan showed dramatically decrease in systolic blood pressure [SBP, MD = -4.39, 95% CI (-6.11, -2.68), P < 0.001], diastolic blood pressure [DBP, MD = -2.69, 95% CI (-4.04, -1.35), P < 0.001], and N-terminal prohormone brain natriuretic peptide [NT-proBNP, MD = -45.34, 95% CI (-46.63, -44.06), P < 0.001]. There was no significant difference in the incidence of adverse reactions between sacubitril/valsartan and the control group. Compared with the RAS inhibitor, sacubitril/valsartan significantly increased eGFR and decreased BP and NT-proBNP, which indicates that it might have cardiovascular and renal benefits in patients with heart failure and CKD.

Detecting and Characterizing the Kinetic Activation of Thermal Networks in Proteins: Thermal Transfer from a Distal, Solvent-Exposed Loop to the Active Site in Soybean Lipoxygenase.

The rate-limiting chemical reaction catalyzed by soybean lipoxygenase (SLO) involves quantum mechanical tunneling of a hydrogen atom from substrate to its active site ferric-hydroxide cofactor. SLO has emerged as a prototypical system for linking the thermal activation of a protein scaffold to the efficiency of active site chemistry. Significantly, hydrogen-deuterium exchange-mass spectrometry (HDX-MS) experiments on wild type and mutant forms of SLO have uncovered trends in the enthalpic barriers for HDX within a solvent-exposed loop (positions 317-334) that correlate well with trends in the corresponding enthalpic barriers for kcat. A model for this behavior posits that collisions between water and loop 317-334 initiate thermal activation at the protein surface that is then propagated 15-34 Å inward toward the reactive carbon of substrate in proximity to the iron catalyst. In this study, we have prepared protein samples containing cysteine residues either at the tip of the loop 317-334 (Q322C) or on a control loop, 586-603 (S596C). Chemical modification of cysteines with the fluorophore 6-bromoacetyl-2-dimethylaminonaphthalene (Badan, BD) provides site-specific probes for the measurement of fluorescence relaxation lifetimes and Stokes shift decays as a function of temperature. Computational studies indicate that surface water structure is likely to be largely preserved in each sample. While both loops exhibit temperature-independent fluorescence relaxation lifetimes as do the Stokes shifts for S596C-BD, the activation enthalpy for the nanosecond solvent reorganization at Q322C-BD (Ea(ksolv) = 2.8(0.9) kcal/mol)) approximates the enthalpy of activation for catalytic C-H activation (Ea(kcat) = 2.3(0.4) kcal/mol). This study establishes and validates the methodology for measuring rates of rapid local motions at the protein/solvent interface of SLO. These new findings, when combined with previously published correlations between protein motions and the rate-limiting hydride transfer in a thermophilic alcohol dehydrogenase, provide experimental evidence for thermally induced "protein quakes" as the origin of enthalpic barriers in catalysis.

Glassy dynamics of nanoparticles in semiflexible ring polymer nanocomposite melts.

By employing molecular dynamics simulations, we explore the dynamics of NPs in semiflexible ring polymer nanocomposite melts. A novel glass transition is observed for NPs in semiflexible ring polymer melts as the bending energy (Kb) of ring polymers increases. For NPs in flexible ring polymer melts (Kb = 0), NPs move in the classic diffusive behavior. However, for NPs in semiflexible ring polymer melts with large bending energy, NPs diffuse very slowly and exhibit the glassy state in which the NPs are all irreversibly caged be the neighbouring semiflexible ring polymers. This glass transition occurs well above the classical glass transition temperature at which microscopic mobility is lost, and the topological interactions of semiflexible ring polymers play an important role in this non-classical glass transition. This investigation can help us understand the nature of the glass transition in polymer systems.

Aggregation-Dispersion Transition for Nanoparticles in Semiflexible Ring Polymer Nanocomposite Melts.

By employing molecular dynamics simulations, we explored the conformation transition of nanoparticles (NPs) in semiflexible ring polymer nanocomposite melts. A novel aggregation-dispersion transition for NPs in ring polymer nanocomposites occurs when the bending energy of ring chains increases. The conformations of flexible ring chains near NPs are radial distribution, and the entropic depletion interactions between a pair of NPs in flexible ring polymer nanocomposite melts are attractive, however, the rod-like ring chains wrap around the NPs and the entropic depletion interactions between NPs in rod-like ring polymer melts are repulsive. The aggregation-dispersion transition for NPs induced by chain topology in polymer nanocomposites can provide a new access to achieve miscibility in producing high-performance polymer-nanoparticle composites by simply varying the topological structure of polymers.

The adsorption-desorption transition of double-stranded DNA interacting with an oppositely charged dendrimer induced by multivalent anions.

The adsorption-desorption transition of DNA in DNA-dendrimer solutions is observed when high-valence anions, such as hexavalent anions, are added to the DNA-dendrimer solutions. In the DNA-dendrimer solutions with low-valence anions, dendrimers bind tightly with the V-shaped double-stranded DNA. When high-valence anions, such as pentavalent or hexavalent anions, are added to the DNA-dendrimer solutions, the double-stranded DNA chains can be stretched straightly and the dendrimers are released from the double-stranded DNA chains. In fact, adding high-valence anions to the solutions can change the charge spatial distribution in the DNA-dendrimer solutions, and weaken the electrostatic interactions between the positively charged dendrimers and the oppositely charged DNA chains. Adsorption-desorption transition of DNA is induced by the overcharging of dendrimers. This investigation is capable of helping us understand how to control effectively the release of DNA in gene/drug delivery because an effective gene delivery for dendrimers includes non-covalent DNA-dendrimer binding and the effective release of DNA in gene therapy.

Omega-3 polyunsaturated fatty acids reduce vascular endothelial growth factor production and suppress endothelial wound repair.

Long-chain polyunsaturated omega-3 fatty acids (n-3 PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have diverse beneficial effects on cardiovascular diseases and have been used widely as supplements in reducing the risk of cardiovascular diseases. The beneficial effects are believed to be related to the anti-inflammatory and antioxidant action of n-3 PUFA. EPA and DHA can inhibit inflammatory cytokine-induced endothelial activation and reduce endothelial migration and proliferation. Revascularisation is the major therapeutic approach for end-stage cardiovascular diseases, and endothelial migration and proliferation are essential for the success of revascularisation. The aim of this study was to investigate the role of n-3 PUFAs on vascular endothelial wound repair. A scratch-wound repair assay was carried out in cultured human microvascular endothelial cells (HMEC-1) with and without different concentrations of DHA or EPA. The effect of DHA and EPA on HMEC-1 proliferation was examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The effect of DHA and EPA on vegf mRNA expression was detected by real-time RT-PCR and vascular endothelial growth factor (VEGF) protein secretion by enzyme-linked immunosorbent assay. DHA and EPA dose-dependently suppressed HMEC-1 cell proliferation and wound repair. DHA and EPA treatment did not induce significant HMEC-1 cell death. The treatment, however, significantly suppressed vegf mRNA expression and protein secretion in both normoxia and hypoxia culture conditions. The addition of exogenous VEGF prevented DHA- and EPA-mediated suppression of HMEC-1 cell proliferation. DHA and EPA have anti-angiogenic effect partially through vegf suppression. The use of DHA and EPA may benefit angiogenic diseases, but may have potential side effects to patients undergoing revascularisation therapy. Further studies will be required to confirm the effect of n-3 PUFAs on vascular repair.

[Transplantation of autologous myoblasts transfected with VEGF165 improves heart function after myocardial infarction in rabbits].

OBJECTIVE: To determine the improvements of post-infarction heart function after transplantation of autologous skeletal myoblasts transfected with VEGF165 in rabbits. METHODS: Myocardium infarction was induced in rabbits by left anterior descending coronary artery ligation. At 2 weeks, 1.75×10(7) autologous skeletal myoblasts transfected with pcDNA3.1-VEGF165 were infused into the region of MI via direct intramuscular injection; pcDNA3.1 served as a control. RESULTS: The DAPI-labeled and Desmin-positive immunostained skeletal myofibers were found throughout the infracted areas and border zones, and the density of blood capillary in the MI region transplanted by myoblasts with VEGF165 was increased (measured 4 weeks later and compared with controls). Heart function was examined by the Buxco system and demonstrated that maximum dp/dt [(1607.23±102.67) mmHg/s vs (1217.77±89.91) mmHg/s] and minimum dp/dt [(-1535.09 ± 81.34) mmHg/s vs (1174.58 ± 91.5) mmHg/s] were improved in the heart transplanted with the transfected myoblasts(P<0.05). CONCLUSION: Autologous skeletal myoblasts transfected with VEGF165 could ameliorate the blood supply in the MI region, and aid recovery of heart function more quickly in post-infarction hearts. This suggests an effective treatment for myocardium infarction.

Autologous myoblasts transplantation improves heart function after myocardiac infarction.

OBJECTIVE: To determine whether autologous skeletal myoblasts implantation improves the cardiac function after myocardial infarction and the possible mechanism. METHODS: Myocardial infarction was induced by ligation of the left anterior descending coronary artery in rabbits. At 2 weeks, 1.34 10(7) to 1.75 10(7) autologous skeletal myoblasts were infused into the lesion via direct intramuscular injection. In the control group, the postinfarction hearts were infused with medium alone. Buxco invasive cardiac function testing and histopathological examination were utilized to evaluate the functional and structural changes in the myocardium 4 weeks later. RESULTS: Both maximum rising rate of the left intraventricular pressure [+dp/dtmax,(1 217.77±89.91)mmHg/s vs. (897.83±70.04) mmHg/s] and maximum falling rate of the left intraventricular pressure [-dp/dtmax,(-1 174.58±91.5)mmHg/s vs. (-753.67±69.66)mmHg/s] were improved in the myoblast transplanted group compared with medium infusion group. The positive desmin immunostaining skeletal myofibers in the myocardium were found throughout the infracted areas and the border zone. CONCLUSION: Autologous skeletal myoblasts can establish muscle tissue when transplanted into postinfarction hearts, and this mucle can treat myocardiac infarction effectively.