亲水性两性离子交联聚合物微球的制备及性能

水分散聚合是制备亲水性交联聚合物微球的新方法。为揭示水分散聚合体系中各组分及反应条件对产物结构与性能的影响规律,分别以硫酸铵水溶液和聚乙二醇水溶液为分散介质,丙烯酰胺、丙烯酸、甲基丙烯酰氧乙基三甲基氯化铵为共聚单体,过硫酸铵/亚硫酸氢钠为引发剂,N,N’-亚甲基双丙烯酰胺复配物为交联剂制备了亲水性两性离子交联聚合物微球,并对产物结构及在钻井液中的性能进行了研究。结果表明,聚合分散介质和反应组分对产物性能影响显著,分散介质为硫酸铵溶液时产物在钻井液中具有强增黏作用和降滤失作用,而以醇水溶液为分散介质制备的聚合物微球在钻井液中无明显增黏效应;随着聚合体系中丙烯酰胺和交联剂加量增加,微球粒径减小,对钻井液的增黏作用增强;增加引发剂加量会导致产物粒径减小,对钻井液的增黏作用下降。在适当条件下制得的聚合物微球可在升温条件下膨胀,对钻井液黏度影响小,热稳定性好,具有明显的封堵强化作用,可用于不稳定地层钻井施工。

基于不同水溶性聚合物制备的绒囊流体的性能特征

为揭示采用不同水溶性聚合物制备的绒囊流体性能特征,制备出具有优良耐酸性的高性能绒囊工作液。分别采用羟乙基纤维素(HEC)、羧甲基纤维素(CMC)、羟乙基淀粉(HES)、羧甲基淀粉(CMS)与非离子型表面活性剂制备了一系列绒囊流体,并研究所得绒囊流体的流变性能,考察了氯化钠、盐酸和温度对绒囊流体性能的影响。通过六速旋转黏度计测定绒囊流体流变性能可知,采用不同水溶性聚合物制备的绒囊流体的几种性能有明显差异。不同水溶性聚合物制备的绒囊流体表观黏度大小顺序为HEC>CMC>CMS>HES,剪切稀释能力大小顺序为HES>CMS>HEC>CMC;不同水溶性聚合物制备的绒囊流体抗盐性能顺序为HEC>HES>CMS>CMC;不同绒囊流体相应耐酸性顺序为HEC>HES>CMC>CMS;采用旋转流变仪测定绒囊流体的黏度与温度的变化关系可知,不同绒囊流体的黏度与温度之间呈现各自特有的变化关系,绒囊流体耐温性能顺序为HEC>HES>CMS>CMC;对比来看,采用HEC可制备出具有优良耐温耐酸抗盐性能的绒囊流体。

HPMC/P(AM-co-AA)-Zr^(4+)/NaCl导电水凝胶的制备与性能

为制备具有良好力学性能和导电性能的水凝胶,在羟丙基甲基纤维素(HPMC)存在的条件下,以丙烯酰胺(AM)和丙烯酸(AA)为共聚单体、Zr^(4+)为交联剂,通过原位自由基聚合制备了HPMC/P(AM-co-AA)-Zr^(4+)/NaCl双网络水凝胶,并对其力学性能、导电性能及相关传感性能进行了研究。结果表明,所制备的HPMC/P(AM-co-AA)-Zr^(4+)/NaCl水凝胶断裂应变达1820%、断裂强度为0.77 MPa、断裂能为4210 kJ/m^(3),电导率为8.44 S/m,可实现力学性能与导电性能的平衡。该水凝胶具有良好的回复能力和较高应变灵敏度,表现出宽的应变窗口(0%~800%),可望用于应变传感器。

Development of a potent benzonitrile-based inhibitor of glutaminyl-peptide cyclotransferase-like protein(QPCTL)with antitumor efficacy

Dear Editor,Immune checkpoint therapies manipulating the immune system to eliminate tumor cells have shown remarkable clinical efficacy in treating various cancers.CD47,an emerging efficient immune checkpoint,is crucial for cancer cells to evade macrophagemediated phagocytosis by interaction with signal-regulatory proteinα(SIRPα).Antibodies blocking the CD47/SIRPαinteraction have been effective to promote macrophage-mediated phagocytosis in various types of cancer in mice and humans.CD47 is not only highly expressed in tumor cells,but also normal cells,such as red blood cells(RBCs).Thus,during clinical trials involving cancer patients,anti-CD47 antibodies may promote the macrophagesmediated phagocytosis of RBCs,ultimately inducing undesirable anemia side effects.In contrast,small molecule inhibitors interrupting CD47/SIRPαaxis have shown potential to overcome the anemia,possibly due to their lower immunogenicity and shorter half-life compared to antibodies.1 Hence,developing the novel strategies,especially those without the anemia side effect,to intervene in CD47/SIRPαinteraction will benefit cancer immunotherapy.

基于结构的CRISPR蛋白xCas9的优化设计

酿脓链球菌(Streptococcus pyogenes Cas9,SpCas9)已成为强大的基因组编辑工具,但其可识别的前间隔序列临近基序(Protospacer adjacent motifs,PAMs)范围有限,且存在脱靶效应。为解决这些问题,文中提出一种对SpCas9的定向进化突变体xCas9进行优化的理性方法。首先,使用Rosetta程序进行能量最小化以优化Cas9的三维结构,获得其能量最低的构象;然后,对其定向进化所得氨基酸位点进行组合突变设计;最后,通过自由能排序从设计突变体中筛选出用于实验验证的最优变体。经DNA剪切实验验证,成功地获得了一个多PAM识别和低脱靶的新变体yCas9(262A/324R/409N/480K/543D/694L/1219T)。该变体可识别NG、GAA和GAT序列,且其由错配sgRNA引导的脱靶DNA剪切活性低,为生物医学领域提供了一个有潜在应用价值的基因编辑工具。同时,文中还对SpCas9、xCas9和yCas9进行了分子动力学模拟,揭示了其PAM识别和脱靶效应的机理,可为进一步的CRISPR/Cas9蛋白优化改造提供理论指导。

Effects of Angelica sinensis extracts on lipid oxidation in fish feeds and growth performance of juvenile Jian carp(Cyprinus carpio var. Jian)

The study was to explore the effect of the extracts of Angelica sinensis(EAs) on lipid oxidation in fish feeds compared with ethoxyquin(EQ) and the effect of dietary EAs on growth performance of carp(Cyprinus carpio var. Jian). Firstly, fish feeds were respectively added with EQ, and ethyl ether extract ethyl acetate extract(EAE), acetone extract, ethanol extract(EE) and aqueous extract(AQE) of Angelica sinensis, except for the control. The results showed that EAs and EQ inhibited lipid oxidation in fish feed(P < 0.05). Of all of the examined EAs, EAE showed the strongest protective effects against lipid oxidation(P < 0.05). Moreover, EAE at high concentrations showed a stronger effect on lipid oxidation compared with EQ(P < 0.05). Then, 7 experimental diets respectively supplemented with 0.0, 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0 g/kg of EAE were fed to the respective treatment groups for 30 d. Four replicates were performed for each treatment group; 20 carp(mean weight: 12.10 ± 0.13 g) were in each replicate. The result indicated that dietary EAE improved the growth performance in carp(P < 0.05). The appropriate con centration of EAE for carp growth was estimated to be 3.643 g/kg diet. Thus, EAE could be used as a natural antioxidant in feeds for Jian carp.

Effect of oxide film on nanoscale mechanical removal of pure iron

In this paper, the properties of an oxide film formed on a pure iron surface after being polished with an H2O-based acidic slurry were investigated using an atomic force microscope （AFM）, Auger electron spectroscopy （AES）, and angle-resolved X-ray photoelectron spectroscopy （AR-XPS） to partly reveal the material removal mechanism of pure iron during chemical mechanical polishing （CMP）. The AFM results show that, when rubbed against a cone-shaped diamond tip in vacuum, the material removal depth of the polished pure iron first slowly increases to 0.45 nm with a relatively small slope of 0.11 nm/μN as the applied load increases from 0 to 4 μN, and then rapidly increases with a large slope of 1.98 nm/μN when the applied load further increases to 10 μN. In combination with the AES and AR-XPS results, a layered oxide film with approximately 2 nm thickness （roughly estimated from the sputtering rate） is formed on the pure iron surface. Moreover, the film can be simply divided into two layers, namely. an outer layer and an inner layer. The outer layer primarily consists of FeOOH （most likely α-FeOOH） and possibly Fe2O3 with a film thickness ranging from 0.36 to 0.48 nm （close to the 0.45 nm material removal depth at the 4 μN turning point）, while the inner layer primarily consists of Fe304. The mechanical strength of the outer layer is much higher than that of the inner layer. Moreover, the mechanical strength of the inner layer is quite close to that of the pure iron substrate. However, when a real CMP process is applied to pure iron, pure mechanical wear by silica particles generates almost no material removal due to the extremely high mechanical strength of the oxide film. This indicates that other mechanisms, such as in-situ chemical corrosion-enhanced mechanical wear, dominate the CMP process.

Nucleolus localization of SpyCas9 affects its stability and interferes with host protein translation in mammalian cells

The CRISPR/Cas9 system,originally derived from the prokaryotic adaptive immune system,has been developed as efficient genome editing tools.It enables precise gene manipulation on chromosomal DNA through the specific binding of programmable sgRNA to target DNA,and the Cas9 protein,which has endonuclease activity,will cut a double strand break at specific locus.However,Cas9 is a foreign protein in mammalian cells,and the potential risks associated with its introduction into mammalian cells are not fully understood.In this study,we performed pull-down and mass spectrometry(MS)analysis of Streptococcus pyogenes Cas9(SpyCas9)interacting proteins in HEK293T cells and showed that the majority of Cas9-associated proteins identified by MS were localized in the nucleolus.Interestingly,we further discovered that the Cas9 protein contains a sequence encoding a nucleolus detention signal(NoDS).Compared with wild-type(WT)Cas9,NoDS-mutated variants of Cas9(mCas9)are less stable,although their gene editing activity is minimally affected.Overexpression of WT Cas9,but not mCas9,causes general effects on transcription and protein translation in the host cell.Overall,identification of NoDS in Cas9 will improve the understanding of Cas9's biological function in vivo,and the removal of NoDS in Cas9 may enhance its safety for future clinical use.

Three-dimensional DEM investigation of the stress-dilatancy relation of grain-cementing type methane hydrate-bearing sediment

In this study,the Discrete Element Method(DEM)was employed to investigate numerically the effects of hydrate cementation and intermediate principal stress on the stress-dilatancy relation of graincementing type methane hydrate-bearing sediment(MHBS)by conducting a series of conventional and true triaxial tests.A novel 3D thermo-hydro-mechanical-chemical(THMC)contact model for MHBS was employed.The numerical results show that with increasing hydrate saturation and back pressure,or decreasing confining pressure,temperature and salinity,the stress-dilation relation of grain-cementing type MHBS evolves from dilation-dominant to bond-dominant.For the clean sand samples,the relationship between the normalized stress ratio h/Mcr and the dilatancy rate d is close under different intermediate principal stress coefficients.However,for the MHBS samples,this relationship is still affected by the intermediate principal stress coefficient b,due to the effect of hydrate cementation.