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The impact of N-terminal phosphorylation on LHCII conformation in state transition

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Acta Mechanica Sinica 2014年第3期30卷 447-456页

作者： Jin-Hong Ding Ning Li Man-Liu Wang Yan Zhang Shou-Qin Lü Mian Long Key laboratory of Microgravity(National Microgravity laboratory)and Center of biomechanics and Bioengineering Institute of MechanicsChinese Academy of Sciences

State transition is an important protection mechanism of plants for maintaining optimal efficiency through redistributing unbalanced excitation energy between photosystem II （PSII） and photosystem I （PSI）. This process depends on the reversible phosphorylation/dephosphorylation of the major light-harvesting complex II （LHCII） and its bi-directional migration between PSII and PSI. But it remains unclear how phosphorylation/dephosphorylation modulates the LHCII conformation and further regulates its reversible migration. Here molecular dynamics simulations （MDS） were employed to elucidate the impact of phosphorylation on LHCII conformation. The results indicated that N-terminal phosphorylation loosened LHCII trimer with decreased hydrogen bond （H-bond） interactions and extended the distances between neighboring monomers, which stemmed from the conformational ad- justment of each monomer itself. Global conformational change of LHCII monomer started from its stromal N- terminal （including the phosphorylation sites） by enhancing its interaction to lipid membrane and by adjusting the interaction network with surrounded inter-monomer andintra-monomer transmembrane helixes of B, C, and A, and finally triggered the reorientation of transmembrane helixes and transferred the conformational change to luminal side helixes and loops. These results further our understanding in molecular mechanism of LHCII migration during state transition from the phosphorylation-induced microstructural feature of LHCII.

关键词： State transition LHCII Phosphorylation Conformation

Is changing footstrike pattern beneficial to runners?

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Journal of Sport and Health Science 2017年第2期6卷 146-153页

作者： Joseph Hamill Allison H.Gruber biomechanics laboratory Department of KinesiologyUniversity of MassachusettsAmherstMA 01003USA biomechanics laboratory Department of KinesiologyIndiana UniversityBloomingtonIN 47405USA

Some researchers, running instructors, and coaches have suggested that the "optimal" footstrike pattern to improve performance and reduce running injuries is to land using a mid-or forefoot strike. Thus, it has been recommended that runners who use a rearfoot strike would benefit by changing their footstrike although there is little scientific evidence for suggesting such a change. The rearfoot strike is clearly more prevalent. The major reasons often given for changing to a mid-or forefoot strike are(1) it is more economical;(2) there is a reduction in the impact peak and loading rate of the vertical component of the ground reaction force; and(3) there is a reduction in the risk of a running-related injuries. In this paper,we critique these 3 suggestions and provide alternate explanations that may provide contradictory evidence for altering one's footstrike *** have concluded, based on examining the research literature, that changing to a mid-or forefoot strike does not improve running economy, does not eliminate an impact at the foot-ground contact, and does not reduce the risk of running-related injuries.

关键词： Epidemiology Footfall patterns Forefoot Ground reaction force Impacts Midfoot Rearfoot Running economy

Direct visualizations of air flow in the human upper airway using in-vitro models

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Science China(Life Sciences) 2019年第2期62卷 235-243页

作者： Haijun Wu Mengmeng Wang Jianxia Wang Yunqiang An Hui Wang Yaqi Huang School of Biomedical Engineering Capital Medical University Beijing Key laboratory of Fundamental research on biomechanics in Clinical Application Capital Medical University

A better understanding of airflow characteristics in the upper airway(UA) is crucial in investigating obstructive sleep apnea(OSA), particle sedimentation, drug delivery, and many biomedical problems. Direct visualization of air flow patterns in in-vitro models with realistic anatomical structures is a big challenge. In this study, we constructed unique half-side transparent physical models of normal UA based on realistic anatomical structures. A smoke-wire method was developed to visualize the air flow in UA models directly. The results revealed that the airflow through the pharynx was laminar but not turbulent under normal inspiration, which suggested that compared with turbulent models, a laminar model should be more suitable in numerical simulations. The flow predicted numerically using the laminar model was consistent with the observations in the physical models. The comparison of the velocity fields predicted numerically using the half-side and complete models confirmed that it was reasonable to investigate the flow behaviors in UA using the half-side model. Using the laminar model, we simulated the flow and evaluated the effects of UA narrowing caused by rostral fluid shift on pharyngeal resistance. The results suggested that fluid shift could play an important role in the formation of hypopnea or OSA during sleep.

关键词： air flow visualization upper airway model flow characteristic smoke-wire method flow simulation fluid shift

Effect of persistent high intraocular pressure on microstructure and hydraulic permeability of trabecular meshwork

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Chinese Physics B 2015年第5期24卷 606-613页

作者：梅曦任琳许强郑炜刘志成 School of Biomedical Engineering Capital Medical University Beijing Key laboratory of Fundamental research on biomechanics in Clinical Application Shenzhen Key laboratory for Molecular Imaging Shenzhen Institutes of Advanced Technology Chinese Academy of Sciences

As the aqueous humor leaves the eye, it first passes through the trabecular meshwork （TM）. Increased flow resistance in this region causes elevation of intraocular pressure （IOP）, which leads to the occurrence of glaucoma. To quantitatively evaluate the effect of high IOP on the configuration and hydraulic permeability of the TM, second harmonic generation （SHG） microscopy was used to image the microstructures of the TM and adjacent tissues in control （normal） and high IOP conditions. Enucleated rabbit eyes were perfused at a pressure of 60 mmHg to achieve the high lOP. Through the anterior chamber of the eye, in situ images were obtained from different depths beneath the surface of the TM. Porosity and specific surface area of the TM in control and high IOP conditions were then calculated to estimate the effect of the high pressure on the permeability of tissue in different depths. We further photographed the histological sections of the TM and compared the in situ images. The following results were obtained in the control condition, where the region of depth was less than 55 μm with crossed branching beams and large pores in the superficial TM. The deeper meshwork is a silk-like tissue with abundant fluorescence separating the small size of pores. The total thickness of pathway tissues composed of TM and juxtacanalicular （JCT） is more than 100 p.m. After putting a high pressure on the inner wall of the eye, the TM region progressively collapses and decreases to be less than 40 μm. Fibers of the TM became dense, and the porosity at 34 μm in the high IOP condition is comparable to that at 105 μm in the control condition. As a consequent result, the permeability of the superficial TM decreases rapidly from 120 μm2 to 49.6 μm2 and that of deeper TM decreases from 1.66 μm2 to 0.57 μm2. Heterogeneity reflected by descent in permeability reduces from 12.4 μm of the control condition to 3.74 μm of the high IOP condition. The persistently high IOP makes the TM region colla

关键词： trabecular meshwork hydraulic permeability intraocular pressure glaucoma

Mechanokinetics of receptor-ligand interactions in cell adhesion

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Acta Mechanica Sinica 2015年第2期31卷 248-258页

作者： Ning Li Shouqin Lü Yan Zhang Mian Long Key laboratory of Microgravity(National Microgravity laboratory) Center of Biomechanics and Bioengineeringand Beijing Key Laboratory of Engineered Construction and MechanobiologyInstitute of MechanicsChinese Academy of Sciences

Receptor-ligand interactions in blood flow are crucial to initiate such biological processes as inflammatory cascade,platelet thrombosis,as well as tumor *** mediate cell adhesion,the interacting receptors and ligands must be anchored onto two apposing surfaces of two cells or a cell and a substratum,i.e.,two-dimensional（2D）binding,which is different from the binding of a soluble ligand in fluid phase to a receptor,i.e.,three-dimensional（3D） *** numerous works have been focused on3 D kinetics of receptor-ligand interactions in the immune system,2D kinetics and its regulations have been less understood,since no theoretical framework or experimental assays were established until *** only does the molecular structure dominate 2D binding kinetics,but the shear force in blood flow also regulates cell adhesion mediated by interacting receptors and ***,we provide an overview of current progress in 2D binding and regulations,mainly from our *** issues of theoretical frameworks,experimental measurements,kinetic rates and binding affinities,and force regulations are discussed.

关键词： Receptor-ligand interactions Selectins β_2 integrins 2D binding kinetics

The effects of total ankle replacement on ankle joint mechanics during walking

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Journal of Sport and Health Science 2017年第3期6卷 340-345页

作者： Henry Wang Scott R.Brown biomechanics laboratory School of KinesiologyBall State University Sports Performance research Institute New Zealand(SPRINZ) Auckland University of Technology

Background:End-stage ankle arthritis impairs joint function and patients' *** ankle replacement is a surgical procedure to treat severe ankle *** Talaris Anatomic Ankle^(TM)(STAA) was designed to mimic the normal ankle anatomy and flexion/extension of the ankle *** purpose of this study was to examine the effect of an STAA ankle replacement on ankle joint function and mechanics during ***:Five patients with end-stage unilateral ankle arthritis were *** performed level walking in a laboratory setting on 2occasions,prior to and 3 months after the STAA ankle *** Orthopedic Foot and Ankle Society(AOFAS) hindfoot score was obtained.A 12-camera motion capture system was used to perform walking *** temporo-spatial parameters and ankle joint mechanics were *** Student's t tests and non-parametric Wilcoxon matched tests were performed to examine the differences in biomechanical variables between the pre-and post-surgery walking ***:Compared to the pre-surgical condition,at 3 months of post-STAA surgery,patients experienced greater improvement in AOFAS hindfoot score(p = 0.0001);the STAA ankle demonstrated a 31% increase in ankle joint excursion(p = 0.045),a 22% increase in ankle plantarflexor moment(p = 0.075),a 60% increase in ankle power absorption(p = 0.023),and a 68% increase in ankle power production(p = 0.039).Patients also demonstrated a 26% increase in walking speed(p = 0.005),a 20% increase in stride length(p = 0.013),a 15% decrease in double support time(p = 0.043),and a 5% decrease in total stance time(p = 0.055).Conclusion:Three months after surgeries,the STAA patients experienced improvements in ankle function and gait *** STAA ankle demonstrated improved ankle mechanics during daily activities such as walking.

关键词： Ankle mechanics AOFAS score Arthritis Gait analysis Total ankle replacement Walking

Effects of obesity on breast size,thoracic spine structure and function,upper torso musculoskeletal pain and physical activity in women

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Journal of Sport and Health Science 2020年第2期9卷 140-148页

作者： Julie R.Steele Celeste E.Coltman Deirdre E.McGhee biomechanics research laboratory School of MedicineUniversity of WollongongWollongongNSW 2522Australia research Institute for Sport and Exercise Faculty of HealthUniversity of CanberraCanberraACT 2601Australia

Purpose:This study investigated the effects of obesity on breast size,thoracic spine structure and function,upper torso musculoskeletal pain and physical activity participation in women living independently in the ***:A total of 378 women were divided into 3 groups(Not Overweight:body mass index(BMI)=22.5±0.2 kg/m^2(mean±SE);Overweight:BMI=27.4±0.3 kg/m^2;Obese:BMI=35.4±0.3 kg/m^2).Outcome variables of breast volume(mL),thoracic flexion torque(N·m),thoracic kyphosis(degrees),upper torso musculoskeletal pain(score) and time spent in physical activity(min) were calculated and compared among the 3 groups,adjusting for between-group differences in ***:There was a significant main effect of BMI on all outcome *** classified as Obese displayed significantly larger breasts,had greater thoracic flexion torques and reported less time participating in physical activity relative to the participants who were classified as Not Overweight and *** in the Obese group also displayed significantly more thoracic kyphosis and reported significantly more upper torso musculoskeletal pain compared to their counterparts who were classified as Not ***:This study is the first to demonstrate that increased obesity levels were associated with compromised kyphosis and loading of the thoracic spine,as well as increased symptoms of upper torso musculoskeletal pain and reduced time spent in physical activity in women living in the *** recommend further research to determine whether evidence-based interventions designed to reduce the flexion torque generated on the thoracic spine can improve these symptoms of upper torso musculoskeletal pain and the ability of women with obesity to participate in physical activity.

关键词： Breast volume Obesity Thoracic kyphosis Upper torso loading

Application of digital image correlation to full-field measurement of shrinkage strain of dental composites

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第1期14卷 1-10页

作者： Jian-ying LI Andrew LAU Alex S. L. FOK Minnesota Dental research Centre for Biomaterials and biomechanics School of Dentistry University of Minnesota Minneapolis MN 55455 USA

Objectives： Polymerization shrinkage of dental composites remains a major concern in restorative dentistry because it can lead to micro-cracking of the tooth and debonding at the tooth-restoration interface. The aim of this study was to measure the full-field polymerization shrinkage of dental composites using the optical digital image correlation （DIC） method and to evaluate how the measurement is influenced by the factors in experiment setup and image analysis. Methods： Four commercial dental composites, Premise Dentine, Z 100, Z250 and Tetric EvoCeram, were tested. Composite was first placed into a slot mould to form a bar specimen with rectangular-section of 4 mmx2 mm, followed by the surface painting to create irregular speckles. Curing was then applied at one end of the specimen while the other part were covered against curing light for simulating the clinical curing condition of composite in dental cavity. The painted surface was recorded by a charge-coupled device （CCD） camera before and after curing. Subsequently, the volumetric shrinkage of the specimen was calculated with specialist DIC software based on image cross correlation. In addition, a few factors that may influence the measuring accuracy, including the subset window size, speckle size, illumination light and specimen length, were also evaluated. Results： The volumetric shrinkage of the specimen generally decreases with increasing distance from the irradiated surface with a conspicuous exception being the composite Premise Dentine as its maximum shrinkage occurred at a subsurface distance of about 1 mm instead of the irradiated surface. Z100 had the greatest maximum shrinkage strain, followed by Z250, Tetric EvoCeram and then Premise Dentine. Larger subset window size made the shrinkage strain contour smoother. But the cost was that some details in the heterogeneity of the material were lost. Very small subset window size resulted in a lot of noise in the data, making it difficult to discern the g

关键词： Image correlation Dental composite Polymerization shrinkage Depth of cure

DYNAMIC MODEL AND SIMULATION OF THE PLATELETS'ROLE IN BLOOD COAGULATION

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Acta Mechanica Sinica 2002年第4期18卷 420-428页

作者：许传青曾衍钧 Hans Grgersen biomechanics research Center Beijing Polytechnic Univ.Beijing 100022China Armed Forced InstituteBeijing 100072China biomechanics research Center Beijing Polytechnic Univ.Beijing 100022China Center for Sensory-Motor Interaction Aalborg UniversityDenmark

In order to confirm which process is the most important in the blood coagulation cascade,a dynamic model on the function of platelets in blood coagulation is presented based on biochemical *** on qualitative analysis and mathematical simulation,a series of conclusions about the influence of the activation rate of factor VIII and factor IX on the generation of thrombin(IIa)are *** is evident that the pro-coagulation stimulus must exceed a threshold value to initiate the coagulation *** value is related to the binding constant d_2 of the platelet. The stability of the equilibrium value is also related to the pro-coagulation stimulus. This article also evaluates the influence of the stimulus strength and the activated rate parameter of platelets on *** proportion of platelets activated at any given time is designated *** each c,we obtain a maximum concentration of *** is evident that when the level of factor IX is below 1% of the normal level,the rate of thrombin generation reduces dramatically,resulting in severe bleeding tendency.

关键词： dynamic system numerical simulation biochemical process blood coagulation waterfall mechanism