The biochemical behavior and mechanism of uranium(Ⅵ)bioreduction induced by natural Bacillus thuringiensis

For a broader understanding of uranium migration affected by microorganisms in natural anaerobic environment,the bioreduction of uranium(Ⅵ)(U(Ⅵ))was revealed in Bacillus thuringiensis,a dominant bacterium strain with potential of uranium-tolerant isolated from uranium contaminated soil.The reduction behavior was systematically investigated by the quantitative analysis of U(Ⅳ)in bacteria,and mechanism was inferred from the pathway of electron transmission.Under anaerobic conditions,appropriate biomass and sodium lactate as electron donor,reduction behavior of U(Ⅵ)induced by B.thuringiensis was restricted by the activity of lactate dehydrogenase,which was directly affected by the initial pH,temperature and initial U(Ⅵ)concentration of bioreduction system.Bioreduction of U(Ⅵ)was driven by the generation of nicotinamide adenine dinucleotide(NADH)from enzymatic reaction of sodium lactate with various dehydrogenase.The transmission of the electrons from bacteria to U(Ⅵ)was mainly supported by the intracellular NADH dehydrogenase-ubiquinone system,this process could maintain the biological activity of cells.

Unusual uranium biomineralization induced by green algae: Behavior investigation and mechanism probe

As a biosorbent,algae are frequently used for the biotreatment or bioremediation of water contaminated by heavymetal or radionuclides.However,it is unclear that whether or not the biomineralization of these metal or radionuclides can be induced by algae in the process of bioremediation and what the mechanism is.In this work,Ankistrodsemus sp.has been used to treat the uranium-contaminated water,and more than 98%of uranium in the solution can be removed by the alga,when the initial uranium concentration ranges from 10 to 80 mg/L.Especially,an unusual phenomenon of algae-induced uranium biomineralization has been found in the process of uranium bioremediation and its mineralization mechanism has been explored bymultiple approaches.It is worth noticing that the biomineralization of uranium induced by Ankistrodsemus sp.is significantly affected by contact time and pH.Uranium is captured rapidly on the cell surface via complexation with the carboxylate radical,amino and amide groups of themicroalgae cells,which provides nucleation sites for the precipitation of insolubleminerals.Uranium stimulates Ankistrodsemus sp.to metabolize potassium ions(K+),which may endow algae with the ability to biomineralize uranium into the rose-like compreignacite(K_(2)[(UO_(2))6O_(4)(OH)_(6)]•8H_(2)O).As the time increased,the amorphous gradually converted into compreignacite crystals and a large number of crystals would expand over both inside and outside the cells.To the best of our knowledge,this is the first investigated microalgae with a time-dependent uranium biomineralization ability and superior tolerance to uranium.This work validates that Ankistrodsemus sp.is a promising alga for the treatment of uranium-contaminated wastewater.

加速器生产医用同位素^(211)At及单抗标记

^(211)At,半衰期7.2 h,发射的α粒子具有很高的线性传能密度,是一种理想的靶向α治疗核素.利用中国科学院近代物理研究所强流超导直线加速器提供的α束流辐照Bi靶生产^(211)At,系统考察了加速器生产^(211)At的整个流程,包括加速器辐照、干蒸馏分离、质量分析以及单抗标记.研究结果表明,干蒸馏分离^(211)At的总收率最高达78.53%,获得的固体^(211)At产品具有极高的比活度、核纯度以及化学纯度,其中杂质元素Bi、Cu、Zn、Al含量均低于100 ng/GBq,且入射粒子能量低于28.2 MeV时,N(210At)/N(^(211)At)值低于10-5,研究也实现了^(211)At在尼妥珠单抗上的标记,标记率高达94.86%.基于以上研究我们确立了一套简单、高效的分离方法,为后续我国^(211)At的生产和应用奠定了良好基础.

Microbial reduction of uranium(Ⅵ)by Bacillus sp.Dwc-2:A macroscopic and spectroscopic study

The microbial reduction of U（VI） by Bacillus sp. dwc-2, isolated from soil in Southwest China, was explored using transmission electron microscopy （TEIVI）, X-ray photoelectron spectros- copy （XPS） and X-ray absorption near edge spectroscopy （XANES）. Our studies indicated that approximately 16.0% of U（VI） at an initial concentration of 100 mg/L uranium nitrate could be reduced by Bacillus sp. dwc-2 at pH 8.2 under anaerobic conditions at room temperature. Additionally, natural organic matter （NOM） played an important role in enhancing the bioreduction of U（VI） by Bacillus sp. dwc-2. XPS results demonstrated that the uranium presented mixed valence states （U（VI） and U（IV）） after bioreduction, which was subse- quently confirmed by XANES. Furthermore, the TEM and high resolution transmission electron microscopy （HRTEM） analysis suggested that the reduced uranium was bioaccumulated mainly within the cell and as a crystalline structure on the cell wa11. These observations implied that the reduction of uranium may have a significant effect on its fate in the soil environment in which these bacterial strains occur.

Bioaccumulation characterization of uranium by a novel Streptomyces sporoverrucosus dwc-3

The biosorption mechanisms of uranium on an aerobic bacterial strain Streptomyces sporoverrucosus dwc-3,isolated from a potential disposal site for（ultra-）low uraniferous radioactive waste in Southwest China,were evaluated by using transmission electron microscopy（TEM）,energy dispersive X-ray（EDX）analysis,Fourier transform infrared spectroscopy（FT-IR）,X-ray photoelectron spectroscopy（XPS）,proton induced X-ray emission（PIXE）and enhanced proton backscattering spectrometry（EPBS）.Approximately60% of total uranium at an initial concentration of 10 mg/L uranium nitrate solution could be absorbed on 100 mg S.sporoverrucosus dwc-3 with an adsorption capacity of more than3.0 mg/g（wet weight）after 12 hr at room temperature at p H 3.0.The dynamic biosorption process of S.sporoverrucosus dwc-3 for uranyl ions was well described by a pseudo second-order model.S.sporoverrucosus dwc-3 could accumulate uranium on cell walls and within the cell,as revealed by SEM and TEM analysis as well as EDX spectra.XPS and FT-IR analysis further suggested that the absorbed uranium was bound to amino,phosphate and carboxyl groups of the cells.Additionally,PIXE and EPBS results confirmed that ion exchange also contributed to the adsorption process of uranium.

Recent progress of astatine-211 in endoradiotherapy:Great advances from fundamental properties to targeted radiopharmaceuticals

Astatine-211(^(211)At,t_(1/2)=7.21 h)emitting twoαparticles with energies of 5.87 and 7.45 MeV,can lead to a high linear energy transfer(LET=98.84 ke V/μm)and short tissue range(50~90μm).Since the 1950s,^(211)At had stepped into endoradiotherapy and has always been regarded as one of the most promisingα-emitters for targeted-alpha therapy(TAT)in various malignancies.In the past two decades,^(211)At related radiopharmaceuticals have achieved great progress in the studies of basic physicochemical properties of astatine,^(211)At labeling strategies,preclinical and clinical studies,producing profound effects in nuclear medicine.This work will give a panorama of^(211)At-related researches in the recent 20 years,which will cover both the fundamental insights of^(211)At radiochemistry and applied labeling compounds.It can provide some important hints for the studies of TAT and other radiopharmaceuticals applied in tumor radiotherapy.

Phosphorous-Based Pillar[5]arenes for Uranyl Extraction

One phosphine oxide-based pillar[5]arene 1a and two novel phosphorous-based pillar[5]arenes 1b and 1c were synthesized for use as extractants in solvent extraction of 22UO+.The results from host-guest interactions pertinent to the extracted complexes of 1a-1c revealed a significant difference in complexation capability between 1a and 1b(or 1c)by using 1H NMR,31P NMR and FT-IR techniques.The extraction of 22UO+in separate extraction sys-tem and in simulated nuclear industry effluent containing 12 competing ions demonstrated the superior efficiency and selectivity of 1a towards 22UO+over other cations in acidic feed.Log-log plot analysis indicated the 1∶1 stoichiometry(ligand/metal)for the extracted complex formed between the ligand and 22UO+.