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 c...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.展开更多
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...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 ,展开更多
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 ...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.展开更多
噪音有害健康,那么,音乐则有益于身心。这似乎是一个简单的逻辑推理。我们强调前者有余,提倡后者不足。这是否有涉“国情”?是否要等到噪音污染被治理得差不多的时候,人们才有暇顾及问题的另一面?其实,本文所议已远远超出了“有益身心...噪音有害健康,那么,音乐则有益于身心。这似乎是一个简单的逻辑推理。我们强调前者有余,提倡后者不足。这是否有涉“国情”?是否要等到噪音污染被治理得差不多的时候,人们才有暇顾及问题的另一面?其实,本文所议已远远超出了“有益身心”的范畴。因为它所谈论的是其:Power to Heal！仅 Heal一词就足可让我们把玩一番。我们的汉语对付这个不起眼的小词显得有点吃力。不信请看外版词典对Heal的释义: Heal:to make sound,well,or healthy again;restore to health [heal thesisck] 从此释义观.它的涵义远甚于“有益身心”,而本文详有列举的音乐疗法的成功病例,便让我们大开眼界。 国人喜好晨练。笔者遍访美国时也不忘早起,在花园般的街头跑步、打拳.做功.但令我遗憾的是,除了偶见出来“遇狗”的当地居民之外,便绝少见到晨练者.我曾寻思:当噪音之害被治理得差不多的时候.国人是否会在注重晨练的同时.让“音乐疗法’也遍地开花? 西方人写作喜欢开门见topic sentence。而此文的结尾倒有那么一点提纲挚领的味道.勿忘细读。尤其是这一句: But in a hospital or at home,for young people or older ones.it can be apotent medicine that helps us all.展开更多
(一)A boy tells his friend,“The food was terrible at summer camp this year.My first day there,I threw mine in the lake.I got a big surprise when the fish didn’t throw it back.”一个男孩和他的朋友说:“今年夏令营的食...(一)A boy tells his friend,“The food was terrible at summer camp this year.My first day there,I threw mine in the lake.I got a big surprise when the fish didn’t throw it back.”一个男孩和他的朋友说:“今年夏令营的食物太糟糕了。我在那里的第一天就把我的饭菜扔到了湖里。当时鱼没把它扔回来,我还大吃一惊呢。”展开更多
O. Henry is a famous short stores writer who won fame abroad. His stories are known for their wit and twist endings. The thesis analyzes his representative work A Service Of Love from different points view. It is help...O. Henry is a famous short stores writer who won fame abroad. His stories are known for their wit and twist endings. The thesis analyzes his representative work A Service Of Love from different points view. It is helpful to understand O. Henry's work better.展开更多
As expats in Beijing,t h e r e a r e m a n yaspects of life thatseem surprising,orthat we may have trouble get-ting used to.The most visibleand concrete aspect of life inChina,its traffic,has provedto be a constant hu...As expats in Beijing,t h e r e a r e m a n yaspects of life thatseem surprising,orthat we may have trouble get-ting used to.The most visibleand concrete aspect of life inChina,its traffic,has provedto be a constant hurdle展开更多
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
There is an old Hindi proverb, it goes, "Language changes every eighteenor twenty miles". Despite the influence of television and radio, you canstill find a surprising number of regional varieties of spoken ...There is an old Hindi proverb, it goes, "Language changes every eighteenor twenty miles". Despite the influence of television and radio, you canstill find a surprising number of regional varieties of spoken English withinthe United States, Canada, Australia and especially within the BritishIsles.展开更多
Would you like to spend your holidays traveling by ballon? The first balloon trip took place in France in 1783. It was lasted for only 8 minutes. About a year years late, an American and a Franchman decided to cross t...Would you like to spend your holidays traveling by ballon? The first balloon trip took place in France in 1783. It was lasted for only 8 minutes. About a year years late, an American and a Franchman decided to cross the Channel by a balloon. High over the Channel, they discovered a hole on the balloon. The hole became bigger and bigger. The gas keeping the balloon up was escaped. The men threw all their belongs into the water make the balloon lighter. It started to rise higher agai, but it was still too close to water.展开更多
On December 19, 2021, Chile’s presidential election ended the suspense when Gabriel Boric, the candidate of the left-wing coalition Approve Dignity(Apruebo Dignidad), surprisingly won the second round of voting with ...On December 19, 2021, Chile’s presidential election ended the suspense when Gabriel Boric, the candidate of the left-wing coalition Approve Dignity(Apruebo Dignidad), surprisingly won the second round of voting with a 55.87% of the vote, being elected the 34th president of Chile.展开更多
Even twins can be identified through the tiny marks on the surface of the skin（Credit：Getty Images）.Scientists are finding many surprising ways of identifying you from the other seven billion people in the world....Even twins can be identified through the tiny marks on the surface of the skin（Credit：Getty Images）.Scientists are finding many surprising ways of identifying you from the other seven billion people in the world.生活中你有没有遇见过双胞胎？有的双胞胎相像地只有父母和他们本人才能分清楚,但科学家告诉我们他们可以从7个方面确定每一个人都是独一无二的。展开更多
Part One Ⅰ.TEXT COMPREHENSION There are 20 statements in this part.Some of them are true(T),and some are false(F),according tothe texts you have learned.Write T or F in the following brackets.(20 points,1 point for e...Part One Ⅰ.TEXT COMPREHENSION There are 20 statements in this part.Some of them are true(T),and some are false(F),according tothe texts you have learned.Write T or F in the following brackets.(20 points,1 point for each)1.After Rip Van Winkle had slept in the valley for anight,he found he had become a citizen of the United States.( )2.The Wrong House and New Applications are two stories With surprising endings.( )3.In Lady in the Dark,the old lady refused to give up her jewels because they told the past of her life.( )4.Helen Keller thought it would be a good thing for a small Child to be stricken blind and deaf for a few days.( )展开更多
Clay figurines known as tsa tsa have recently been exploding in popularity in various communities.As such,researchers are fascinated at what makes these things so enchanting and have surprisingly made significant achi...Clay figurines known as tsa tsa have recently been exploding in popularity in various communities.As such,researchers are fascinated at what makes these things so enchanting and have surprisingly made significant achievements in this regard.But there is relatively little research on the tsa tsa mold,and there are even fewer out there performing systematic research.展开更多
基金supported by the National Science Foundation of China ( 11772133, 11372116)
文摘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.
文摘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 ,
文摘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.
文摘噪音有害健康,那么,音乐则有益于身心。这似乎是一个简单的逻辑推理。我们强调前者有余,提倡后者不足。这是否有涉“国情”?是否要等到噪音污染被治理得差不多的时候,人们才有暇顾及问题的另一面?其实,本文所议已远远超出了“有益身心”的范畴。因为它所谈论的是其:Power to Heal！仅 Heal一词就足可让我们把玩一番。我们的汉语对付这个不起眼的小词显得有点吃力。不信请看外版词典对Heal的释义: Heal:to make sound,well,or healthy again;restore to health [heal thesisck] 从此释义观.它的涵义远甚于“有益身心”,而本文详有列举的音乐疗法的成功病例,便让我们大开眼界。 国人喜好晨练。笔者遍访美国时也不忘早起,在花园般的街头跑步、打拳.做功.但令我遗憾的是,除了偶见出来“遇狗”的当地居民之外,便绝少见到晨练者.我曾寻思:当噪音之害被治理得差不多的时候.国人是否会在注重晨练的同时.让“音乐疗法’也遍地开花? 西方人写作喜欢开门见topic sentence。而此文的结尾倒有那么一点提纲挚领的味道.勿忘细读。尤其是这一句: But in a hospital or at home,for young people or older ones.it can be apotent medicine that helps us all.
文摘(一)A boy tells his friend,“The food was terrible at summer camp this year.My first day there,I threw mine in the lake.I got a big surprise when the fish didn’t throw it back.”一个男孩和他的朋友说:“今年夏令营的食物太糟糕了。我在那里的第一天就把我的饭菜扔到了湖里。当时鱼没把它扔回来,我还大吃一惊呢。”
文摘O. Henry is a famous short stores writer who won fame abroad. His stories are known for their wit and twist endings. The thesis analyzes his representative work A Service Of Love from different points view. It is helpful to understand O. Henry's work better.
文摘As expats in Beijing,t h e r e a r e m a n yaspects of life thatseem surprising,orthat we may have trouble get-ting used to.The most visibleand concrete aspect of life inChina,its traffic,has provedto be a constant hurdle
文摘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
文摘There is an old Hindi proverb, it goes, "Language changes every eighteenor twenty miles". Despite the influence of television and radio, you canstill find a surprising number of regional varieties of spoken English withinthe United States, Canada, Australia and especially within the BritishIsles.
文摘Would you like to spend your holidays traveling by ballon? The first balloon trip took place in France in 1783. It was lasted for only 8 minutes. About a year years late, an American and a Franchman decided to cross the Channel by a balloon. High over the Channel, they discovered a hole on the balloon. The hole became bigger and bigger. The gas keeping the balloon up was escaped. The men threw all their belongs into the water make the balloon lighter. It started to rise higher agai, but it was still too close to water.
文摘On December 19, 2021, Chile’s presidential election ended the suspense when Gabriel Boric, the candidate of the left-wing coalition Approve Dignity(Apruebo Dignidad), surprisingly won the second round of voting with a 55.87% of the vote, being elected the 34th president of Chile.
文摘Even twins can be identified through the tiny marks on the surface of the skin（Credit：Getty Images）.Scientists are finding many surprising ways of identifying you from the other seven billion people in the world.生活中你有没有遇见过双胞胎？有的双胞胎相像地只有父母和他们本人才能分清楚,但科学家告诉我们他们可以从7个方面确定每一个人都是独一无二的。
文摘Part One Ⅰ.TEXT COMPREHENSION There are 20 statements in this part.Some of them are true(T),and some are false(F),according tothe texts you have learned.Write T or F in the following brackets.(20 points,1 point for each)1.After Rip Van Winkle had slept in the valley for anight,he found he had become a citizen of the United States.( )2.The Wrong House and New Applications are two stories With surprising endings.( )3.In Lady in the Dark,the old lady refused to give up her jewels because they told the past of her life.( )4.Helen Keller thought it would be a good thing for a small Child to be stricken blind and deaf for a few days.( )
文摘Clay figurines known as tsa tsa have recently been exploding in popularity in various communities.As such,researchers are fascinated at what makes these things so enchanting and have surprisingly made significant achievements in this regard.But there is relatively little research on the tsa tsa mold,and there are even fewer out there performing systematic research.
