Molecular insights into impacts of EDTMPA on membrane fouling caused by transparent exopolymer particles (TEP).

While ethylenediamine tetramethylenephosphonic acid (EDTMPA) has been emerged as a stronger chelating agent than ethylene diamine tetraacetic acid (EDTA) for fouling mitigation, and transparent exopolymer particles (TEP) is a major foulant in membrane-based water treatment process, effects of EDTMPA on TEP fouling and the underlying mechanism have been not yet studied. In this study, Flory-Huggins lattice theory was combined with density functional theory (DFT) technology to explore this subject at molecular level. Filtration experiments showed a unimodal pattern of specific filtration resistance (SFR) of TEP sample with Ca2+ concentration in range of 0-3 mM. For the TEP sample with the peak SFR value at 1.5 mM Ca2+, continuous addition of EDTMPA (from 0 to 100 mg·L-1) resulted in a sustained decrease in SFR. Energy dispersive spectroscopy (EDS) mapping characterization showed the continuing decline of calcium content in the TEP layer with increase of EDTMPA addition, indicating that EDTMPA successfully captured Ca2+ from alginate­calcium ligation (TEP), and then disintegrated the TEP structure. DFT simulation showed that Ca2+ preferentially coordinated with the terminal carboxyl groups of alginate chains to form a coordination configuration that is conducive to stretch the three-dimensional polymer network. Such a network corresponded to an extremely high SFR according to Flory-Huggins theory. EDTMPA addition caused disintegration of the coordination configuration of Ca2+ binding to terminal carboxyl groups, which further resulted in collapse and flocculation of TEP gel network structure, thus leading to a continuous SFR decrease. This work provided deep thermodynamic insights into effects of EDTMPA on TEP-associated fouling at molecular level, facilitating to better understanding and mitigation of membrane fouling.

Bioremediation of Petroleum Hydrocarbons Using Acinetobacter sp. SCYY-5 Isolated from Contaminated Oil Sludge: Strategy and Effectiveness Study.

Biodegradation has been considered as an ideal technique for total petroleum hydrocarbon (TPH) contamination, but its efficiency is limited by its application in the field. Herein, an original TPH-degrading strain, SCYY-5, was isolated from contaminated oil sludge and identified as Acinetobacter sp. by 16S rDNA sequence analysis. The biological function of the isolate was investigated by heavy metal tolerance, carbon, and nitrogen source and degradation tests. To enhance its biodegradation efficiency, the response surface methodology (RSM) based on a function model was adopted to investigate and optimize the strategy of microbial and environmental variables for TPH removal. Furthermore, the performance of the system increased to 79.94% with the further addition of extra nutrients, suggesting that the RSM and added nutrients increased the activity of bacteria to meet the needs of the co-metabolism matrix during growth or degradation. These results verified that it is feasible to adopt the optimal strategy of combining bioremediation with RSM to improve the biodegradation efficiency, for contaminated oil sludge.

Disorder of Iron Metabolism Inhibits the Recovery of Unloading-Induced Bone Loss in Hypomagnetic Field.

Exposure of humans and animals to microgravity in spaceflight results in various deleterious effects on bone health. In addition to microgravity, the hypomagnetic field (HyMF) is also an extreme environment in space, such as on the Moon and Mars; magnetic intensity is far weaker than the geomagnetic field (GMF) on Earth. Recently, we showed that HyMF promoted additional bone loss in hindlimb unloading-induced bone loss, and the underlying mechanism probably involved an increase of body iron storage. Numerous studies have indicated that bone loss induced by mechanical unloading can be largely restored after skeletal reloading in GMF conditions. However, it is unknown whether this bone deficit can return to a healthy state under HyMF condition. Therefore, the purpose of this study is to examine the effects of HyMF on the recovery of microgravity-induced bone loss, and illustrates the changes of body iron storage in this process. Our results showed that there was lower bone mineral content (BMC) in the HyMF reloading group compared to the GMF reloading group. Reloaded mice in the HyMF condition had a worse microstructure of femur than in the GMF condition. Femoral mechanical properties, including elastic modulus, stiffness, and ultimate stress, were poorer and toughness was higher in the HyMF group compared with the GMF group. Simultaneously, more iron content in serum, the tibia, liver, and spleen was found under HyMF reloading than GMF reloading. The iron chelator deferoxamine mesylate (DFO) decreased the iron content in the bone, liver, and spleen, and significantly relieved unloading-induced bone loss under HyMF reloading. These results showed that HyMF inhibits the recovery of microgravity-induced bone loss, probably by suppressing the elevated iron levels' return to physiological level. © 2019 American Society for Bone and Mineral Research.

Unraveling the Potential Role of Glutathione in Multiple Forms of Cell Death in Cancer Therapy.

Glutathione is the principal intracellular antioxidant buffer against oxidative stress and mainly exists in the forms of reduced glutathione (GSH) and oxidized glutathione (GSSG). The processes of glutathione synthesis, transport, utilization, and metabolism are tightly controlled to maintain intracellular glutathione homeostasis and redox balance. As for cancer cells, they exhibit a greater ROS level than normal cells in order to meet the enhanced metabolism and vicious proliferation; meanwhile, they also have to develop an increased antioxidant defense system to cope with the higher oxidant state. Growing numbers of studies have implicated that altering the glutathione antioxidant system is associated with multiple forms of programmed cell death in cancer cells. In this review, we firstly focus on glutathione homeostasis from the perspectives of glutathione synthesis, distribution, transportation, and metabolism. Then, we discuss the function of glutathione in the antioxidant process. Afterwards, we also summarize the recent advance in the understanding of the mechanism by which glutathione plays a key role in multiple forms of programmed cell death, including apoptosis, necroptosis, ferroptosis, and autophagy. Finally, we highlight the glutathione-targeting therapeutic approaches toward cancers. A comprehensive review on the glutathione homeostasis and the role of glutathione depletion in programmed cell death provide insight into the redox-based research concerning cancer therapeutics.

Safety of exposure to high static magnetic fields (2 T-12 T): a study on mice.

OBJECTIVES: We aimed to evaluate the biological effects of high static magnetic field (HiSMF, 2-12 Tesla [T]) exposure on mice in a stable and effective breeding environment in the chamber of a superconducting magnet. METHODS: C57BL/6 mice were bred in the geomagnetic field and HiSMF with different magnetic field strengths (2-4 T, 6-8 T, and 10-12 T) for 28 days. The body weight, blood indices, organ coefficients, and histomorphology of major organs were analyzed. RESULTS: The results showed that the HiSMF had no significant effect on the body weight, organ coefficients, or histomorphology of major organs in mice. The HiSMF had no effect on most routine blood and biochemical indices, but the value of the mean corpuscular hemoglobin (MCH) was increased in the 2-4 T group compared with that of the other groups, and the uric acid level (UA) was decreased in the three HiSMF groups compared with that of the control group. CONCLUSION: The C57BL/6 mice were not affected when they were exposed to different HiSMF environments for 28 days. KEY POINTS: • No physiological problems were observed in mice with long-term whole-body exposure to HiSMF.

Iron and magnetic: new research direction of the ferroptosis-based cancer therapy.

Ferroptosis is an iron depend cell death which caused by lipid peroxidation. Abnormal iron metabolism and high intracellular iron content are the characteristics of most cancer cells. Iron is a promoter of cell growth and proliferation. However, iron also could take part in Fenton reaction to produce reactive oxygen species (ROS). The intercellular ROS could induce lipid peroxidation, which is necessary for ferroptosis. Iron metabolism mainly includes three parts: iron uptake, storage and efflux. Therefore, iron metabolism-related genes could regulate intercellular iron content and status, which can be involved ferroptosis. In recent years, the application of nanoparticles in cancer therapy research has become more and more extensive. The iron-based nanoparticles (iron-based NPs) can release ferrous (Fe2+) or ferric (Fe3+) in acidic lysosomes and inducing ferroptosis. Magnetic field is widely used in the targeted concentration of iron-based NPs related disease therapy. Furthermore, multiple studies showed that magnetic fields can inhibit cancer cell proliferation by promoting intracellular ROS production. Herein, we focus on the relationship of between ferroptosis and iron metabolism in cancer cells, the application of nanoparticles and magnetic field in inducing ferroptosis of cancer cells, and trying to provide new ideas for cancer treatment research.

Mutual promotion of electrochemical-localized surface plasmon resonance on nanochip for sensitive sialic acid detection.

Localized surface plasmon resonance (LSPR) induced charge separation were concentrated on the metal nanoparticles surface, which made it sensitive to the surface refractive index changes during optical sensing. Similarly, electrochemical detection was based on the electron transformation on the electrode surface. Herein, we fabricated a nanochip by decorating a nanocone-array substrate with gold nanoparticles and silver nanoparticles for dynamic electro-optical spectroscopy. Mercaptophenyl boronic acid (MPBA) was immobilized firmly on the nanochip by the metal-S bond for sensitive sialic acid sensing. Owing to the high stability of gold nanoparticles and the high sensitivity of silver nanoparticles, the nanochip showed good performance in LSPR detection with rich and high responses. Besides, the nanochip also showed sensitive electrical signals during electrochemical detection due to the excitation of the energetic charges from the nanoparticles surface to the reaction system. The dynamic electro-optical spectroscopy was based on a unique combination of LSPR and linear sweep voltammetry (LSV). On the one hand, electrochemical signals activated the electrons on the nanochip to promote the propagation and resonance of surface plasmon. On the other hand, LSPR concentrated the electrons on the nanochip surface, which made the electrons easily driven to enhance the current in electrochemical detection. Results showed that mutual promotion of electrochemical-LSPR on nanochip covered a linear dynamic range from 0.05 mM to 5 mM on selective sialic acid detection with a low detection limit of 17 µM. The synchronous amplification of the electro-optical response during electrochemical-LSPR, opened up a new perspective for efficient and sensitive biochemical detection.

Preparation and Characterization of Highly Ordered Mercapto-Modified Bridged Silsesquioxane for Removing Ammonia-Nitrogen from Water.

In acidic conditions, mesoporous molecular sieves SBA-15 and SBA-15-SH were synthesized. Structural characterization was carried out by powder X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), 13C CP MAS-NMR, 29Si CP MAS-NMR and nitrogen adsorption⁻desorption (BET). The results showed that in SBA-15-SH, the direct synthesis method made the absorption peak intensity weaker than that of SBA-15, while the post-grafted peak intensity did not change. Their spectra were different due to the C-H stretching bands of Si-O-Si and propyl groups. But their structure was still evenly distributed and was still hexangular mesoporous structure. Their pore size increased, and the H-SBA-15-SH had larger pore size. The adsorption of ammonia-nitrogen by molecular sieve was affected by the relative pressure and the concentration of ammonia-nitrogen, in which the adsorption capacity of G-SBA-15-SH was the largest and the adsorption capacity of SBA-15 was the smallest.

Adsorption of Reactive Blue 19 from aqueous solution by chitin nanofiber-/nanowhisker-based hydrogels.

Physical hydrogels prepared from partially deacetylated chitin nanofibers/nanowhiskers (DEChNs) were prepared and evaluated as a new adsorbent for Reactive Blue 19 (RB19) solutions. The effects of pH, initial dye concentration, contact time and temperature were investigated. The optimum pH value for the adsorption experiments was found to be 1.0; as pH increases, the dye adsorption capacity decreases gradually. The adsorption of RB19 onto partially deacetylated chitin nanofiber-/nanowhisker-based hydrogels (DEChNs-Gels) was relatively fast, as the equilibrium could be reached in almost 20 min. The maximum adsorption capacity was found to be 1331 mg g-1 at pH = 1 (degree of deacetylation (DDA) = 23%, dye concentration = 1000 mg L-1), considering the practical applications, the adsorption capacity in pH = 5 (838 mg g-1) was believed to have more practical significance. A pseudo-second-order kinetics model agreed very well with the experimental results. Equilibrium data also fitted well to the Freundlich adsorption isotherm model in this study. The DEChNs-Gels exhibited a high efficiency for removing RB19 from aqueous solutions as a result of their nanofibrillar network and excellent pore structure accompanied by the presence of amino groups. Even when the DDA was lowered to 15%, the adsorption capacity reached 940 mg g-1 due to its nanostructural assembly of nanofibers/nanowhiskers, which showed great advantages compared to highly deacetylated chitosan-based adsorbents (DDA > 70%). Considering the issue of environmental protection and adsorption efficiency, DEChNs-Gels have become a potential substitute for chitosan-based adsorbents due to the milder deacetylation process and superior performance, making this material an attractive adsorbent for textile dyes.

Robust Self-Standing Chitin Nanofiber/Nanowhisker Hydrogels with Designed Surface Charges and Ultralow Mass Content via Gas Phase Coagulation.

Partially deacetylated α-chitin nanofibers/nanowhiskers mixtures (DEChNs) and TEMPO-oxidized α-chitin nanowhiskers (TOChNs) that had positive and negative charges, respectively, were transformed into hydrogels with mass concentrations of 0.2, 0.4, 0.6, 0.8, and 1.0% under ammonium hydroxide or hydrochloric acid "gas phase coagulation". To the best of our knowledge, 0.2% is the lowest mass content reported for the successful preparation of physical self-standing hydrogels based on chitin nanofibers/nanowhiskers. The even and uniform coagulation under "gas phase" is one of the key aspects of preparing hydrogels with quite low mass content. The storage modulus achieved the highest value of 8.35 and 3.73 KPa for DEChN and TOChN hydrogels, respectively, at the mass concentration of 1.0%, and these are known to be the highest values reported in the literature for hydrogels at the same mass concentration of chitin nanofibers/nanowhiskers. The equilibrium swelling ratio (ESR) of both DEChN and TOChN hydrogels decreased with increasing mass content at neutral pH. As the pH increased from 2 to 10, the swelling degree of DEChN hydrogels decreased from 268 to 130, whereas the swelling degree of TOChN hydrogels increased from 128 to 242. Additionally, due to the electrostatic attraction between the hydrogels and dyes, DEChN hydrogels had significant adsorption of Reactive Blue 19, while TOChN hydrogels had effective adsorption of Basic Green 4. The different pH-dependent swelling behavior and adsorption affinity of the DEChN and TOChN hydrogels were related to their designed opposite surface charges corresponding to the surface amino groups on the DEChNs and carboxyl groups on the TOChNs.

Mechanisms of Competitive Adsorption Organic Pollutants on Hexylene-Bridged Polysilsesquioxane.

Hexylene-bridged periodic mesoporous polysilsesquioxanes (HBPMS) are a promising new class of adsorbent for the removal of organic contaminants from aqueous solutions. These hybrid organic-inorganic materials have a larger BET surface area of 897 m2·g-1 accessible through a cubic, isotropic network of 3.82-nm diameter pores. The hexylene bridging group provides enhanced adsorption of organic molecules while the bridged polysilsesquioxane structure permits sufficient silanols that are hydrophilic to be retained. In this study, adsorption of phenanthrene (PHEN), 2,4-Dichlorophenol (DCP), and nitrobenzene (NBZ) with HBPMS materials was studied to ascertain the relative contributions to adsorption performance from (1) direct competition for sites and (2) pore blockage. A conceptual model was proposed to further explain the phenomena. This study suggests a promising application of cubic mesoporous BPS in wastewater treatment.

Genetic structure and hierarchical population divergence history of Acer mono var. mono in South and Northeast China.

Knowledge of the genetic structure and evolutionary history of tree species across their ranges is essential for the development of effective conservation and forest management strategies. Acer mono var. mono, an economically and ecologically important maple species, is extensively distributed in Northeast China (NE), whereas it has a scattered and patchy distribution in South China (SC). In this study, the genetic structure and demographic history of 56 natural populations of A. mono var. mono were evaluated using seven nuclear microsatellite markers. Neighbor-joining tree and STRUCTURE analysis clearly separated populations into NE and SC groups with two admixed-like populations. Allelic richness significantly decreased with increasing latitude within the NE group while both allelic richness and expected heterozygosity showed significant positive correlation with latitude within the SC group. Especially in the NE region, previous studies in Quercus mongolica and Fraxinus mandshurica have also detected reductions in genetic diversity with increases in latitude, suggesting this pattern may be common for tree species in this region, probably due to expansion from single refugium following the last glacial maximum (LGM). Approximate Bayesian Computation-based analysis revealed two major features of hierarchical population divergence in the species' evolutionary history. Recent divergence between the NE group and the admixed-like group corresponded to the LGM period and ancient divergence of SC groups took place during mid-late Pleistocene period. The level of genetic differentiation was moderate (FST  = 0.073; G'ST  = 0.278) among all populations, but significantly higher in the SC group than the NE group, mirroring the species' more scattered distribution in SC. Conservation measures for this species are proposed, taking into account the genetic structure and past demographic history identified in this study.

Computational and experimental determinations of the UV adsorption of polyvinylsilsesquioxane-silica and titanium dioxide hybrids.

Sunscreens that absorb UV light without photodegradation could reduce skin cancer. Polyvinyl silsesquioxanes are known to have greater thermal and photochemical stability than organic compounds, such as those in sunscreens. This paper evaluates the UV transparency of vinyl silsesquioxanes (VS) and its hybrids with SiO2(VSTE) and TiO2(VSTT) experimentally and computationally. Based on films of VS prepared by sol-gel polymerization, using benzoyl peroxide as an initiator, vinyltrimethoxysilane (VMS) formulated oligomer through thermal curing. Similarly, VSTE films were prepared from VMS and 5-25 wt-% tetraethoxysilane (TEOS) and VSTT films were prepared from VMS and 5-25 wt-% titanium tetrabutoxide (TTB). Experimental average transparencies of the modified films were found to be about 9-14% between 280-320 nm, 67-73% between 320-350nm, and 86-89% between 350-400nm. Computation of the band gap was absorption edges for the hybrids in excellent agreement with experimental data. VS, VSTE and VSTT showed good absorption in UV-C and UV-B range, but absorbed virtually no UV-A. Addition of SiO2 or TiO2 does not improve UV-B absorption, but on the opposite increases transparency of thin films to UV. This increase was validated with molecular simulations. Results show computational design can predict better sunscreens and reduce the effort of creating sunscreens that are capable of absorbing more UV-B and UV-A.

Delivery of doxorubicin in vitro and in vivo using bio-reductive cellulose nanogels.

A methacrylation strategy was used to functionalize carboxymethyl cellulose and prepare redox-sensitive cellulose nanogels which contained disulfide bonds. Dynamic light scattering, zeta potential and electron microscopy were utilized to characterize these nanogels. It was found that these nanogels had a spherical morphology with a diameter of about 192 nm, and negative surface potential. These redox-sensitive nanogels were stable against high salt concentration but de-integrated in the reducing environment containing glutathione. When doxorubicin (DOX) was loaded into the nanogels, a high drug loading content (36%) and a high encapsulation efficiency (83%) were achieved. Confocal laser scanning microscopy and co-localization images showed that DOX-loaded nanogels were internalized by the cancer cells through endocytosis and the DOX could be delivered into the nucleus. Near-infrared fluorescence imaging biodistribution examination indicated that the nanogels could passively target to the tumor area by the EPR effect and had a significantly prolonged circulation time. In vivo antitumor evaluation found that DOX-loaded nanogels exhibited a significantly superior antitumor effect than the free DOX by combining the tumor volume measurement and the examination of cell apoptosis and proliferation in tumor tissues.

Synthesis and characterization of cubic mesoporous bridged polysilsesquioxane for removing organic pollutants from water.

Hexane, octane, phenyl, and biphenyl-bridged bis(triethoxysilyl) precursors were used in synthesizing cubic mesoporous bridged polysilsesquioxane (BPS) copolymers. Structural characterization was carried out by FTIR, small angle XRD, Brunauer-Emmett-Teller-N2 sorption, (1)H NMR, and TEM. We successfully synthesized both "rigid" and "soft" 3D cubic mesoporous BPS with high surface area and pore volume, as attested by the comprehensive characterization data. Adsorption of pyrene, phenanthrene, nitrobenzene, and 2,4-dichlorophenol on BPS was greatly affected by adsorbate properties, i.e., Kow, solvation properties and molecular size. Hydrophobic interaction dominantly controlled organic pollutants' sorption on BPS. Other interactions, e.g., π-π and H-bond interactions, also have effects on sorption as indicated by Kow normalized sorption isotherms. Rigid aromatic BPS (phenyl and biphenyl) showed a higher sorption capacity than soft aliphatic BPS (hexane and octane). A conceptual model was proposed to further explain the phenomena. This study suggests a promising application of cubic mesoporous BPS in wastewater treatment.

[Application and development of quantum dots in the imaging of lymph node metastasis].

Quantum dots(QDs) are semiconductor nanocrystals composed of element from the periodic groups of II(-IIIIII( or III(-IIIII(, which possess wide excitation spectra and narrow emission spectra. The maximum emission wavelength of QDs can be controlled in a relatively simple manner by variation of particle size and composition. QDs can be tuned at a variety of precise wavelengths from ultraviolet(UV) to near infrared(NIR). QDs can be conjugated to a wide range of biological targets, including monoclonal antibodies, proteins, polymers and nucleic acid probes. These characteristics make it not only for revealing interaction of nucleic acids, proteins and other biological macromolecules, by biological imaging but also for detection of lymph node metastasis through preoperative and introperative lymphatic imaging. Along with the continuously improvement of observation techniques and quantum dot structure optimization in recent years, the research on lymph node imaging is ongoing.

[Static magnetic fields and its biomedical effects].

Nowadays, health care products based on static magnetic fields (SMF) and merchandise of magnetic therapy are popular around the world. But the biomedical effects of SMF to animals or human beings remain a widely concerned controversy. In this paper, the recent researches in China and abroad about the biomedical effects of SMF were reviewed in three levels: the cellular, animal and human levels. Nevertheless, these data were not consistent with each other and even some contradicts others' researches. So, it is necessary to do more and further studies on SMF dosing regiman, sham control magnetic device and blinding procedures to obtain the optimal magnetic intensity, the desired therapeutic effects in practical cases and prepare for applying the SMF in biomedical fields more effectively in the future.

Study of three-dimensional configurations of (γ-methacryloxypropyl)-silsesquioxanes by ultraviolet laser matrix-assisted desorption/ionization time-of-flight mass spectrometry and quantum chemical calculation.

[(3-Methacryloxy)propyl]silsesquioxanes (MSSO) were prepared from the hydrolytic condensation of [(3-methacryloxy)-propyl]trimethoxysilane (MPMS) in the presence of an acid catalyst (HCOOH). The proposed MSSO structures were characterized with Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) ((1)H, (13)C and (29)Si), and were assigned by ultraviolet laser matrix-assisted desorption/ionization time-of-flight mass spectrometry (UV-MALDI-TOF MS). The large organic group connected to silicon was simplified for the quantum chemical calculation (QCC), and the correlation of the calculated total energies (E(T)) before and after simplification was analyzed by multiple linear regression, verifying no significant influence on the final conclusions of the research of structural formulas by a correlation coefficient (r). The geometric parameters (Si-O bond length and Si-O-Si, O-Si-O bond angles) and E(T) of the simplified MSSO were calculated by QCC to determine the relative stability of various MSSO structures. The structural geometry (silicon ring), the fraction of intramolecular cycles (f) and the number of the silicon rings (F) were also employed to qualitatively determine the relative stability. The results of the calculation showed that almost all of the cage structures had a lower E(T) than the isomeric ladder structures; therefore, most MSSO structures are of the cage type.

Nuclear DNA microsatellites reveal genetic variation but a lack of phylogeographical structure in an endangered species, Fraxinus mandshurica, across North-east China.

BACKGROUND AND AIMS: The widely accepted paradigm that the modern genetic structure of plant species in the northern hemisphere has been largely determined by recolonization from refugia after the last glacial maximum fails to explain the presence of cold-tolerant species at intermediate latitudes. Another generally accepted paradigm is that mountain ridges act as important barriers causing genetic isolation of species, but this too has been challenged in recent studies. The aims of the work reported here were to determine the genetic diversity and distribution patterns of extant natural populations of an endangered cool temperate species, Faxinus mandshurica, and to examine whether these two paradigms are appropriate when applied to this species over a wide geographical scale. METHODS: 1435 adult individuals were sampled from 30 natural populations across the main and central range of the species, covering major mountain ranges across North-east China (NEC). Genetic variation was estimated based on nine polymorphic nuclear microsatellite loci. Phylogeographical analyses were employed using various approaches, including Bayesian clustering, spatial analysis of molecular variance, Monmonier's algorithm, neighbor-joining trees, principal co-ordinate analysis and isolation by distance. KEY RESULTS: Genetic diversity within populations was relatively high, and no significant recent bottlenecks were detected in any of the populations. A significant negative correlation between intra-population genetic diversity and latitude was identified. In contrast, genetic differentiation among all the populations examined was extremely low and no clear geographic genetic structure was identified, with the exception of one distinct population. CONCLUSIONS: The modern genetic structure in this species can be explained by extensive gene flow, an absence of mountains acting as barriers, and the presence of a wide refuge across NEC rather than multiple small refugia. Intra-population genetic variation along latitudes is probably associated with the systematically northward shifts of forest biomes in eastern China during the mid-Holocene. To determine important genetic patterns and identify resources for conservation, however, it will be necessary to examine differentially inherited genetic markers exposed to selection pressures (e.g. chloroplast DNA) and to investigate different generations.