Force Spectrum of Single CsgA Nanofiber Reveal Surprising Properties

CsgA protein monomers consist of aβ-helix of five repeat units possessing several conservative residues and thus,inherently fibrillate.CsgA protein monomers could self-assemble into hierarchical nanofiber structure cross multiple scales after expression and secretion by E.Coli cells.Previous researches show that CsgA nanofibers could provide adhesion,stiffness,and mechanical homogeneity for the biofilms,host cells’fibronectin binding for internalization,or protection against phage attack.CsgA nanofibers have obtained various applications in material science and synthetic biology.To illustrate,CsgA nanofibers have characteristics of intrinsic hierarchical structures across multiple scales,robustness in harsh environments and programmable functionality via biological tools.Studying the force spectrum or mechanical properties of the nanofiber can provide fundamental information of self-assembly process and ultra-stability in extreme conditions.Single molecule techniques such as atomic force microscopy,optical tweezers,and magnetic tweezers have been widely applied to study proteins.In these studies,proteins are usually chemically conjugated or genetically constructed to have a tag such as histidine,cysteine or biotin.Genetic engineering requires modification of the plasmids encoding the specific protein,and also involve special protein expression and purification.Such study needs collaboration from multi-disciplinary.It normally studies one protein at a time which gives out clear signal but lacks throughput and efficiency.Here we have established a simple method to measure all kinds of proteins without labels.The carboxyl terminus of a protein is attached to the amine group on a magnetic bead,and the amine terminus of the protein is attached to glutaraldehyde on the glass slide.Then we used magnetic tweezers to manipulate and stretched the bead and protein.Extension versus rotation relation was used to identify a single protein or protein fibril.The fiber under tension is also observed by Scanning Electronic Microcopy which convinces that single CsgA-His fibril is linked to a microbead.The peak of diameter distribution is around 15 nm.The fracture of fibers was observed in real time on SEM.Force-extension curves of single fibers are obtained in real time.The force-extension curves generally agree with the worm like chain model.The persistence lengths from the fitting are from 0.9 to 49.8 nm.The elongation ratio increases gradually with force until reaches a plateau.The maximum elongation ratio of 78 nanofibers were made into an elongation ratio distribution diagram,more than half of CsgA-His nanofibers has an elongation ratio from 0 to 2,some are distributed in 2~10,and a few are distributed in 10~18.The maximum elongation ratio of CsgA-His nanofibers is 17.1,indicating that the fibril’s flexibility is much higher than DNA or silk fiber.For forces less than 20 pN,the extension was reversible.With a 42.1 pN holding force,the extension jumped in steps of from 30 to 365 nm and was irreversible.At the scale tested,the jumps corresponded to the unfolding of multiple beta sheets in the fiber.Work for CsgA-His nanofibers during stretching increase with the normalized strain fractions.The experimental data agree with a theoretical prediction for a single CsgA protein from a SMD calculation.Therefore,our results provide key information for the understandings of CsgA protein nanofiber assembly and biofilm robustness.

A surprising visual improvement following a prolonged 5-month retained subfoveal perfluorocarbon liquid

Dear Sir,I am Dr.Daniel Ting,from the Department of Ophthalmology,Singapore National Eye Centre,Singapore.I write to present a case of a surprising significant visual improvement following a prolonged 5-month retained subfoveal perfluorocarbon liquid.Retained perfluorocarbon liquid（PFCL）has been shown to cause decreased visual acuity,retinal pigment epithelial（RPE）toxicity,retinal degeneration and gravity deformation ,

Eight Surprising Foods You’ve Never Tried to Grill Before

With summer in full swing,it’s time to fire up the grill.About 80%of American households own a grill,according to a 2013 study by the Hearth,Patio&Barbecue Association.The survey also found that those folks love grilling because cooking outdoors feels satisfactory,and the food'tastes so good.'But if you think grills are exclusively reserved for chicken wings and baby back ribs,you’re wrong.Add some of these foods to your next barbecue’s menu and get ready to become a bona fide grill master.

基于显著场景Bayesian Surprise的移动机器人自然路标检测

移动机器人在未知非结构化环境下的自然路标检测是层次化环境建模的基础.文中提出一种基于显著场景Bayesian Surprise的自然路标检测方法.通过计算场景的视觉注意图,引导SURF特征采样聚集在显著区域内,提出融合空间关系的词袋模型构造场景表观的模式向量,建立基于该特征描述的地点Multivariate Polya模型,并通过度量传感器观测的Surprise来获取显著场景对应的路标.实验验证自然路标检测方法在大规模复杂室内环境中具有较低的漏检率和误检率,结合层次化SLAM方法验证路标检测器对生成拓扑节点的有效性.

Spring a Surprise on Someone

Felix had just drifted off to sleep when the bed shook andsprung a surprise on him.“Ha,ha,” Chadwick laughed.“Thatsure woke you up.”Felix frowned.“You be careful or

be surprised,in surprise和to one’s surprise

我们在初中英语学习了be surprised,in surprise和to one s surpris。它们的区别是什么呢? 一、be surprised,其后常跟介词at连用,是“对某人或某事感到惊讶”,这里的surprised是个过去分词,相当于形容词,作表语,表示主语所处的状态,例如:

Market Reactions to Zero or Small Positive Sales Surprise

This paper studies how the stock market reacts to zero or small positive sales surprise.Using data from firms listed in the U.S.,the paper shows that before 2003 investors react more to positive earnings surprises while after 2003 they react more to the opposite.When sales forecasts are first reported,investors believe in sales numbers and favor firms that meet or beat sales forecasts,but after 2003,investors grow skeptical,realize the possibility of sales management and trust more in negative sales surprises.One thing in common for both two samples is that Sales Response Coefficients of extreme sales surprises are smaller than those of moderate sales surprises.

Small Surprise

My husband and I had just finished tucking(使上床安睡)our four young ones into bed one evening when we heard sobbingcoming from three-year-old Eric’s room.Rushing to his side,wefound him crying hysterically(歇斯底里地).He had

An Analysis of Surprise Markers in Linguistic Research Articles

To have a better understanding of surprise makers in linguistic Research Articles(RAs),this research selects 85 articles published in Applied Linguistics,analyzes 93 adjective surprise markers according to surprise frame,and explores readers’understanding of surprise markers in terms of the Immersed Experiencer Frame(IEF).The results show that,the Experiencers are activated at the lexical level and 78.49%Experiencers of them are implied,which encourages readers better immersed in the surprise motion.At the clause level,96.77%Triggers are new information,which attracts readers’attention to the information obtained in the present study in the process of Construal.Besides,the Degrees(90.32%are neutral),the Explanations(75.27%are unidentified),and the Resolutions(41.94%do not exist)are also construed at the clause level,which allows readers to make little effort to interpret surprise.In the process of Integration,readers proceed to the Resolutions by new information(34.41%),prior knowledge(20.43%),and speculation(3.23%)at the discourse level.It seems that the surprise markers are mainly used by authors as a means to attract readers and to promote their research.This research validates surprise frame as well as sheds light on emotion words using and comprehending in RAs.

LOOK BACK WITH SURPRISE,WASTE LAND BECAME HOT LAND

What the economic and technological development district reallymean?It is easy for today’s people to answer this question.However,twelve years ago,many Chinese did not know what the "newbornbaby"would be like.The general architect of China’s reform and opening,Mr.

浅谈to one's surprise结构种种

介词 to 是英语中常用词之一。它的主要含义为“到,往,对于,倾向”等等。如 go to the pub 到酒馆去;To whom it may concern.致有关负责人(正式信函的开头使用语);She’s so kind to me.她对我非常友好。然而,介词 to 还有一种特殊意义,相当于 so as to cause(esp.a feel-ing)(致使……),例如 to one’s surprise(使某人吃惊的是)。

A Surprise

Mr Dodds works in a bank (银行), and lives alone.He has a family in the next town: his sister lives there with her husband,and her son,Mark.Mr Dodds does not see his sister or her family from one year to the next,but he sends them Christmas cards,and he has

A Surprise

Mr Dodds works in a bank(银行), and lives aloile. He has a family in the next town: his sister lives there with her husband, and her son, Mark. Mr Dodds does not see his sister or her family from one year to the next,

意外充分性引导的深度神经网络测试样本生成

由于深度神经网络(deep neural network,DNN)模型的复杂性和不确定性等属性,对模型的一般行为和边界行为进行充分的测试是保障模型质量的重要手段.当前的研究主要基于制定的覆盖准则,结合模糊测试技术生成衍生测试样本,从而提升测试充分性,但较少综合考虑测试样本的多样性及个体揭错能力.意外充分性指标量化测试样本与训练集在神经元输出方面的差异,是测试充分性评估的重要指标,目前缺乏基于此指标的测试样本生成方法.因此,提出了一种意外充分性引导的深度神经网络测试样本生成方法,首先,筛选对于决策结果贡献较大的重要神经元,以其输出值为特征,改进意外充分性指标;其次,基于测试样本的意外充分性度量筛选具有揭错能力的种子样本;最后,利用覆盖引导的模糊测试思想,将测试样本的意外充分性值和DNN模型预测的类别概率差异作为联合优化目标,利用梯度上升算法计算扰动,迭代生成测试样本.为了验证所提方法的有效性,选取5个DNN模型作为被测对象,涵盖4种不同的图像数据集,实验结果表明,改进的意外充分性指标能够有效捕捉异常的测试样本,同时减少计算时间开销.在测试样本生成方面,与方法DeepGini和RobOT相比,基于所提的种子样本选择策略生成的衍生测试集的意外覆盖率最高提升了5.9个百分比和15.9个百分比.相比于方法DLFuzz和DeepXplore,所提方法的意外覆盖率最高提升了26.5个百分比和33.7个百分比.

基于汉语孤岛现象的大语言模型语言能力评估

基于概率来预测下一词的生成式大语言模型因其在语言生成方面的出色性能,使得不少人认为这种模型本质上就是人类语言官能的模型。然而,基于语法规则研究语言的学者则认为,大语言模型并不能洞察人类语言官能的本质。研究以汉语孤岛效应为切入点,评估了以GPT-2和Gemma 2为代表的大语言模型对这一语言现象的理解能力。我们设计了两组实验。实验一通过量化孤岛效应的影响因子,测试了汉语母语者对孤岛效应的认知。结果表明,母语者能够清晰地察觉出汉语中的孤岛效应,准确判别出汉语不合语法的句式。实验二通过计算最小对比对中违反孤岛和遵守孤岛句子的概率,测试了以上两种模型对孤岛效应的反应。结果表明,GPT-2和Gemma 2虽然可以甄别出两类句子在概率分布上存在差异;但其并不理解概率分布较低,即违反孤岛限制的句子,实际上是母语者根本不会产出的句子。对比以上两组实验,我们认为尽管大语言模型在语言生成方面表现出色,但在理解和判断特定语言现象方面仍然存在局限性,尚未达到人类语言能力水平。

竞争对手的负面盈余意外:一损俱损还是此消彼长?

以2011-2021年A股上市公司为研究样本,聚焦高集中度的垄断行业,以负面盈余意外作为关键事件,以事件公司同行业其他公司作为焦点公司,采用事件研究法探究竞争对手负面盈余意外对焦点公司市场反应的影响。研究发现,在垄断行业中,竞争对手发生负面盈余意外的两天内(竞争对手发布盈余公告的当天和接下来一天),焦点公司的累计超额收益显著为正,且竞争对手的负面盈余意外程度越大,焦点公司的累计超额收益越高,说明竞争对手负面盈余意外在行业内产生了显著的竞争效应。进一步研究发现,产品可替代性以及焦点公司与竞争对手的相似度均会加剧正面溢出,而行业增长对正面溢出具有显著的缓解作用。

汉语惊讶语步结构的多样性及其理据

现代汉语中,惊讶表达的语步结构主要分为七种:反应型、提问型、评论型、反应-提问型、反应-评论型、提问-评论型、反应-提问-评论型;其中,反应型的使用频率最高,反应-提问-评论型的使用频率最低。根据程度划分的不同惊讶种类倾向采用特定的语步结构:惊骇多用反应型,惊愕多用提问型或评论型,惊叹多用反应-评论型,惊奇多用提问型。汉语惊讶表达的语步结构是惊讶产生-延续机制的语言显现,并受到汉语言特点、上下文连贯等因素的影响。