生物系统中的相变现象及其力学研究进展

近年来实验研究发现生物系统中存在着与金属类似的相变现象,因此该文探讨生物力学中一个新的研究方向:生物系统中的相变力学.介绍3种发生在生物系统中的相变力学现象:DNA分子在拉伸作用下和噬菌体的尾鞘在噬菌体感染细菌的过程中所发生的两种相变力学现象,另外一种我们要着重介绍的是发生在细菌运动中的细菌鞭毛细丝的多相相变.涉及到的内容包括细菌鞭毛的组成结构以及细菌鞭毛细丝的相变在细菌运动中所起的作用、细菌鞭毛细丝的宏观和微观结构、相变机理以及相关的相变实验现象,描述细菌鞭毛细丝从左螺旋状态到右螺旋状态相变的一维Ginzburg-Landau相变理论模型.最后,讨论一些在生物相变方面的心得体会.

Analysis on the Essential Characters and Biological Yield Change of Purple-fleshed Sweetpotato Xuzishu 3

Objective] This study was performed to investigate the trait changes and their correlations as wel as the dynamic changes of biological yield of Xuzishu 3, which wil help to enhance the yield and anthocyanin content of sweetpotato by cul-tivation. [Method] We systematical y measured the agronomic traits, qualitative char-acters and biological yield of Xuzishu 3 during six growing periods to investigate the dynamic changes of its essential characters and yield accumulation. [Result] The characters of Xuzishu 3 appeared most prosperous after the 90th d except for an-thocyanin content. Extremely significant positive correlations were found between ev-ery two of the dry matter rates of above-ground parts （including leaf petioles, leaves and stems）, reducing sugar content and potato weight per plant. Assimilated product distributed more in stems and leaves than in storage roots before the 90th d in growing period. Photosynthetic capacity and net assimilation rate gradual y de-creased after the 90th d, but the assimilated product distributing to storage roots in-creased quickly and maximized in the 135th d. [Conclusion] Xuzishu 3 is a late ma-turing variety requiring more fertilizer, and the accumulation of anthocyanin fluctuates during the growth period of Xuzishu 3. So yield of Xuzishu 3 can be increased by applying more fertilizer and extending the growth period reasonably, meanwhile the anthocyanin content can be increased by means of control ing temperature, light, water and phytohormone within 60 d after planting.

Effect of temperature-induced phase transitions on bioleaching of chalcopyrite

The phase transformation of chalcopyrite and the effect of its phase status on bacterial leaching were studied. Under the protection of high-purity argon, different temperatures(203, 382 and 552℃) were applied to natural chalcopyrite to complete the phase change. In addition, the chalcopyrite was bioleached before and after the phase change. The results show that the chalcopyrite heated at 203 and 382℃ remained in the α phase, whereas the chalcopyrite changed from α to β phase at 552℃. The leaching rates of chalcopyrite after the phase transitions at 203, 382 and 552℃ were 32.9%, 40.5% and 60.95%, respectively. Further, the crystal lattice parameters of chalcopyrite increased and lattice energy decreased, which were the fundamental reasons for the significant increase in leaching rate. Electrochemical experiments demonstrated that with increasing annealing temperature, the polarization resistance decreased and corrosion current density increased. The higher the oxidation rate was, the higher the leaching rate was.

Numerical study on freezing-thawing phase change heat transfer in biological tissue embedded with two cryoprobes

A two-dimensional model for freezing and thawing phase change heat transfer in biological tissue embedded with two cryoprobes was established.In this model,the blood vessels were considered as tree-like branched fractal network,and the effective flow rate and effective thermal conductivity of blood were obtained by fractal method.The temperature distribution and ice crystal growth process in biological tissue embedded with two cryoprobes during freezing-thawing process were numerically simulated.The results show that the growth velocity of ice crystal in freezing process from 200 to 400 s is more rapid than that from 400 to 600 s. Thawing process of frozen tissue occurs in the regions around cryoprobes tips and tissue boundary simultaneously,and the phase interfaces are close to each other until ice crystal melts completely.The distance of two cryoprobes has a more profound effect on the temperature distribution in freezing process at 400 s than at 800 s.

Seasonal changes in TC and WSOC and their ^13C isotope ratios in Northeast Asian aerosols： land surface–biosphere–atmosphere interactions

In order to understand the relative importance of anthropogenic and biological sources of carbonaceous aerosols in Northeast Asia,we measured total carbon(TC)and water-soluble organic carbon(WSOC)and their stable carbon isotope ratios(d^(13)C)in total suspended particulates collected from Sapporo,northern Japan(43.07°N,141.36°E)over a 1-year period(during 2 September 2009and 5 October 2010).Temporal variations of TC showed a gradual decrease from mid-autumn to winter followed by a gradual increase to growing season with a peak in early summer.Both d^(13)C_(TC)and d^(13)C_(WSOC)showed very similar temporal trends with a gradual enrichment of^(13)C from mid-autumn to winter followed by a depletion in the^(13)C to early summer and thereafter it remained stable,except for few cases.Based on the results obtained together with the air mass trajectories,we found that biogenic emissions including biological particles(e.g.,pollen)and secondary organic aerosol formation from biogenic volatile organic compounds are the important sources of carbonaceous aerosols in spring/summer whereas fungal spores from soil and biomass burning and enhanced fossil fuel combustion contribute significantly in autumn/winter and in winter,respectively,in Northeast Asia.

Ecological Responses to Holocene Millennial-Scale Climate Change at High Altitudes of East and Central Asia: A Case Study of Picea/Abies Pollen Changes in Lacustrine Sediments

Ecosystem response to climate change in high-altitude regions is a focus on global change research. Picea/Abies forests are widely distributed at high altitudes of East and Central Asia, and their distribution changes are sensitive to climate change. Humidity is an important climatic factor that affects high-altitude ecosystems; however, the relationship between distribution changes of Picea/Abies forests and millennial-scale variability of humidity is still not dear. Palynological records can provide insights into millennial-scale paleovegetation changes, which have been successfully used to reconstruct past climate change in East and Central Asia. In this study, we synthesized 24 Picea/Abies pollen and humidity/moisture changes based upon Holocene lake records in East and Central Asia in order to explore the response of high-latitude ecosystem to millennial-scale climate change. The changing pattern of Holocene lacustrine Picea/Abies pollen in arid Central Asia differs from that of monsoonal East Asia, which can be due to different millennial-scale climate change patterns between monsoonal and arid Central Asia. Then, the relationship between changes in Picea/Abies pollen and humidity/moisture conditions was examined based on a comparison of pollen and humidity/moisture records. The results indicate that millennial-scale Picea/Abies distribution changes aremainly controlled by moisture variability at high altitudes, while the temperature effect plays a minor role in Picea/Abies distribution changes. Moreover, this research proves that lacustrine Picea/Abies pollen can be used as an indicator of millennial-scale humidity/moisture evolution at high altitudes in East and Central Asia.

细胞内生物大分子的相分离研究进展

细胞内生物大分子的相分离(Phase separation)现象是近几年受到极大关注的新兴研究领域。作为一种细胞生化反应的聚集分割机制,其在自然界中广泛存在,参与基因转录调控,影响生物体对外界刺激的应答等重要生理过程。相分离失调可能导致一些重大疾病的发生,诸多交叉领域的研究者正试图通过相分离这个全新角度来审视老年痴呆等相关疾病,探索其发生的分子机制以及通过相分离进行干预和治疗的潜在可能性。文中拟介绍该领域最新研究进展,从生物相分离现象的发现、生化基础及其与疾病发生的联系等方面,综述目前的主要研究方向,并对该领域拟解决的关键问题进行展望。

Coastal blue carbon： Concept, study method, and the application to ecological restoration

Coastal blue carbon refers to the carbon taken from atmospheric CO2; fixed by advanced plants(including salt marsh,mangrove, and seagrass), phytoplankton, macroalgae, and marine calcifiers via the interaction of plants and microbes; and stored in nearshore sediments and soils; as well as the carbon transported from the coast to the ocean and ocean floor. The carbon sequestration capacity per unit area of coastal blue carbon is far greater than that of the terrestrial carbon pool. The mechanisms and controls of the carbon sink from salt marshes, mangroves, seagrasses, the aquaculture of shellfish and macroalgae, and the microbial carbon pump need to be further studied. The methods to quantify coastal blue carbon include carbon flux measurements, carbon pool measurements, manipulative experiments, and modeling. Restoring, conserving, and enhancing blue carbon will increase carbon sinks and produce carbon credits, which could be traded on the carbon market. The need to tackle climate change and implement China's commitment to cut carbon emissions requires us to improve studies on coastal blue carbon science and policy. The knowledge learned from coastal blue carbon improves the conservation and restoration of salt marshes,mangroves, and seagrasses; enhances the function of the microbial carbon pump; and promotes sustainable aquaculture, such as ocean ranching.

Interactive effect of climate warming and nitrogen deposition may shift the dynamics of native and invasive species

Aims Projections of invasive species expansion under a warmer world often do not explicitly consider the concurring nitrogen(N)deposition.It remains largely unknown how the convoluted effect of climate warming and N deposition will shift the native and invasive species dynamics.Here,we hypothesize that the concurring in creases in N and temperature would promote growth of invasive species greater than that of native species.Methods A controlled greenhouse experiment was conducted to quantify the growth response of an invasive species(Solidago canadensis L.)and a co-existing native species(Artemisia argyi Levi,et Van)under the effects of climate warming,N deposition and their interactions.Important Findings Due to the strong positive effect of N addition,the interactive effect of temperature increase and N addition resulted in an overall significant increase in growth of both in vasive and native species,demonstrating that these manipulations may make microhabitats more favorable to plant growth.However,the relative increases in biomass,height and diameter of invasive S.canadensis were signifiesntly lower than those of native A.argyi.This suggests that the vegetative growth superiority of invasive S.canadensis over the native species A.argyi is reduced by the enhanced N availability in the warmer world.Therefore,the inclusion of N deposition may mitigate the projection of invasive species S.canadensis expansion under climate warming.

Future biomass carbon sequestration capacity of Chinese forests

Chinese forests, characterized by relatively young stand age, represent a significant biomass carbon （C） sink over the past several decades. Nevertheless, it is unclear how forest biomass C sequestration capacity in China will evolve as forest age, climate and atmospheric CO2 concentration change continuously. Here, we present a semi-empirical model that incorporates forest age and climatic factors for each lbrest type to estimate the effects of forest age and climate change on total forest biomass, under three different sce-narios based on the fifth phase of the Coupled Model Intercomparison Project （CMIPS）. We estimate that age-related forest biomass C sequestration to be 6.69 Pg C （~0.17 Pg C a^-1） from the 2000s to the 2040s. Climate change induces a rather weak increase in total forest biomass C sequestration （0.52-0.60 Pg C by tile 2040s）. We show that rising CO2 concentrations could further increase tile total forest biomass C sequestration by 1.68-3.12 Pg C in the 2040s across all three scenarios. Overall, the total forest biomass in China would increase by 8.89-10.37 Pg C by the end of 2040s. Our findings highlight the benefits of Chinese afforestation programs, continued climate change and increasing CO2. concentration in sustaining the forest biomass C sink in the near future, and could therefore be useful for designing more realistic climate change mitigation policies such as continuous forestation programs and careful choice of tree species.

Climate change and infectious diseases of wildlife： Altered interactions between pathogens, vectors and hosts

Infectious diseases result from the interactions of host, pathogens, and, in the case of vector-borne diseases, also vec- tors. The interactions involve physiological and ecological mechanisms and they have evolved under a given set of environmental conditions. Environmental change, therefore, will alter host-pathogen-vector interactions and, consequently, the distribution, in- tensity, and dynamics of infectious diseases. Here, we review how climate change may impact infectious diseases of aquatic and terrestrial wildlife. Climate change can have direct impacts on distribution, life cycle, and physiological status of hosts, pathogens and vectors. While a change in either host, pathogen or vector does not necessarily translate into an alteration of the disease, it is the impact of climate change on the interactions between the disease components which is particularly critical for altered disease risks. Finally, climate factors can modulate disease through modifying the ecological networks host-pathogen-vector systems are belonging to, and climate change can combine with other environmental stressors to induce cumulative effects on infectious dis- eases. Overall, the influence of climate change on infectious diseases involves different mechanisms, it can be modulated by phenotypic acclimation and/or genotypic adaptation, it depends on the ecological context of the host-pathogen-vector interactions, and it can be modulated by impacts of other stressors. As a consequence of this complexity, non-linear responses of disease sys- tems under climate change are to be expected. To improve predictions on climate change impacts on infectious disease, we sug- gest that more emphasis should be given to the integration of biomedical and ecological research for studying both the physio- logical and ecological mechanisms which mediate climate change impacts on disease, and to the development of harmonized methods and approaches to obtain more comparable results, as this would support the discrimination of case-specific versus gen- eral mechanisms .

A molecular dynamics and computational study of human KAT3 involved in KYN pathway

Kynurenine aminotransferases （KATs） catalyze the transamination of kynurenine （KYN） pathway and endogenous KYNs have been suggested to highly correlate to abnormal brain diseases. HKAT3 is a key member of KAT family, while the binding mechanism of KYN and cofactor with HKAT3 has not been determined yet. In this study, we focus on the structure-function relationship among KYN, cofactor and HKAT3. The binding models of KYN complex and KYN＆cofactor complex were ob- tained and were studied by molecular dynamics （MD） simulations. We identified several critical residues and influence of conformational changes in human kynurenine aminotransferase 3 （HKAT3） complexes. The cofactor may contribute largely not only to the catalysis, but also to the binding. In addition, a hypothesis is proposed that a strong hydrophobic interaction between Tyr159 and Lys280 may influence the binding mode and the binding region of the substrate and the cofactor. Our re- suits will be a good starting point for further determination of the biological role.

A skin-like stretchable colorimetric temperature sensor

Wearable and stretchable physical sensors that can conformally contact on the surface of organs or skin provide a new opportunity for human-activity monitoring and personal healthcare. Particularly, various attempts have been made in exploiting wearable and conformal sensors for ther- mal characterization of human skin. In this respect, skin- mounted thermochromic films show great capabilities in body temperature sensing. Thermochromic temperature sensors are attractive because of their easy signal analysis and optical recording, such as color transition and fluorescence emission change upon thermal stimuli. Here, desirable mechanical properties that match epidermis are obtained by physical crosslinking of polydiacetylene （PDA） and transparent elas- tomeric polydimethylsiloxane （PDMS） networks. The result- ing PDA fdm displayed thermochromic and thermo- fluorescent transition temperature in the range of 25-85℃, with stretchability up to 300% and a skin-like Young＇s mod- ulus of -230 kPa. This easy signal-handling provides excellent references for further design of convenient noninvasive sen- sing systems.