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你可能喜欢First DH5a, then BL21(DE3), why?(诱导表达,质粒构建,蛋白,重组子)
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[First DH5a, then BL21(DE3), why?(诱导表达,质粒构建,蛋白,重组子)] 我们做一个蛋白的诱导表达时，有时会先将质粒构建好转入DH5a, 而后验证重组子，在转入BL21(DE3)诱导表达。for what?我同学说是DH5a不能用IPTG诱导，可是启动子不是在质粒里吗？如果是因为B表达得多，那为什么不已开始就转入B而要先D呢？具体的原理是什么呢？ 关键词:[诱导表达 蛋白 质粒构建 重组子 原理 质粒 启动子]…
我们做一个蛋白的诱导表达时，有时会先将质粒构建好转入DH5a, 而后验证重组子，在转入BL21(DE3)诱导表达。for what?我同学说是DH5a不能用IPTG诱导，可是启动子不是在质粒里吗？如果是因为B表达得多，那为什么不已开始就转入B而要先D呢？具体的原理是什么呢？
回复重点不是启动子而是操纵子吧……回复表达不是需要强的启动子吗和操纵子没关系的吧.这个我也一直想知道 .回复那么朋友的意思是BL21（DE3）基因组里有操纵子，而DH5a里和质粒里都没有？回复Molecular Cloning, A Laboratory Manual Volume 3:A3.6Table A3-2 Bacterial StrainsBL21 Remarks:A strain used for high-level epxression of genes cloned into expression vectors containing the bacteriophage T7 promoter (e.g. the pET series). The gene encoding bacteriophage T7 RNA polymerase is carried on the bateriophages lambdaDE3, which is integrated into the chromosome of BL21.DH5alpha Remarks:A recombinant-deficient amber suppressing strain used for plating and growth of plasmids and HsdR17 recA1 endA1 gyrA96 thi-1 relA1 cosmids. The phi80 lacZ deltaM15 mutation permits alpha-complementation with the amino terminus of beta-galactosidase encoded in pUC vectors.回复The phi80 lacZ deltaM15 mutation permits alpha-complementation with the amino terminus of beta-galactosidase encoded in pUC vectors.Thank u, now i understand bl21.顺便问，"phi80 lacZ deltaM15的突变允许pUC载体编码的β半乳糖苷酶氨基酸末端α互补。"是什么意思呢？回复DH5a这个菌种主要用来克隆，endA1 突变大大增加了转入质粒DNA的产量与质量，recA1的突变保证质粒DNA插入的稳定性，所以一般习惯用DH5a来抽提质粒。DH5 is a well-known, versatile strain that can be used in many everyday cloning applications. In addition to supporting blue/white screening, recA1 and endA1 mutations in DH5a increase insert stability and improve the quality of plasmid DNA prepared from minipreps. DH5a Cells offer the following benefits:
Greatly increased plasmid yield and quality due to endA1 mutation
Blue/white screening of recombinant clones due to lacZM15
Ensured insert stability due to recA1 mutationBL21（DE3）主要用来表达蛋白，含有DE3溶原基因，可以用IPTG来诱导产生T7 RNA ，转录含T7操纵子的PET系列质粒，表达目的蛋白 ，并且缺失lon, omp蛋白水解酶。 BL21 is the most widely used host background and has the advantage of being deficient in both lon and ompT proteases.
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频道本月排行用什么东西来形容美国文化会比较贴切呢？（English only）_百度知道
用什么东西来形容美国文化会比较贴切呢？（English only）
一种是salad bowl,一种是meltling pot,希望大家再帮我想出一种形容美国文化的事物，并简单解释一下。要用英语哦！
大家可能没看懂。老师给了我们一篇文章，关于美国文化的。一种观点认为美国文化是salad bowl:相互存在，但又有一定独立性。人们一起工作生活，但回到家就加入了属于自己的ethnic culture，使得各种文化在美国存在着。一种是melting pot:如同炖菜一样，越炖越香，各种文化越战献出自己的长处，并融合为一种美国大文化。要求再想一种比喻方式注意：重点应该放在美国的多元文化上，而不是美国的开放，自由，性！
提问者采纳
The American culture is like open source community. It is different from traditional close software, which is only developped by one company. The open source community consists of many many developpers from differnt countries, and produces various flexible and wonderful softwares. The American culture is such a thing, formed by various cultures. Different immigrants from different countries have their unique culture, but form a new complicated and united American culture. Compared to close software, the American culture is not developped by only one group of people.
提问者评价
我自己想的，pizza，不知道大家觉得怎么样。看得出来这位是自己写的，精神可嘉，呵呵。谢谢各位了
其他类似问题
美国文化的相关知识
其他15条回答
what?I don't know!
fullfill with passion
linear and polarized
blingblingmoneycarfreegirls听过N.W.A.的那首歌唱的:life ain't nothing but b1tchs and money!美国拜金,崇尚自由
i think the word & decacy' may help you.
multicultural society
英语不会，但你可以去翻译一下。美国人最大的特点两字：冒险。如果四个字气派一点，那就是：冒险精彩。
freedom ,open, active,fat
Why American Culture is Unique American culture is unique because it is nurtured, formed and developed under certain conditions, which are characteristically(特性)American. The major factors contributing to the making of this new nation and the forming of a new culture are the hard environment, ethnic diversity(多民族) and plural religion, which is quite different from other nations in the world. What is more, these elements are still influencing the American culture.1. Rough EnvironmentThe early immigrants who were English Puritans settled down in northeast part of American. The environment there was very rough but they believed the poor land could purify their mind so they chose the place along the coast. From 1607 to 1892, frontiers were pushed further west. The American frontier consisted of the relatively unsettled regions of the United States, usually found in the western part of the country. The frontiersmen looked for a land of rich resources and a land of promise, opportunity and freedom. Actually they looked for a better life. So individualism, self-reliance, and equality of opportunity have perhaps been the values most closely associated with the frontier heritage(遗产) of American.2. Ethnic Diversity The population of the United States includes a large variety of ethnic groups coming from many races, nationalities, and religions. People refer to the United States as &melting pot &and the dominant people are British. American is made up of WASP+MM, that is, White, Anglo Saxon, Protestants plus Middle Class and Male. In history, people from different countries in the world rushed to American three times. They brought their own culture to American and later on different cultures were mixed together. Thus the unique American culture is formed, a common cultural life with commonly shared values.3. Plural religionThe fundamental American belief in individual freedom and the right of individuals to practice their own religion is at the center of religious experience in the United States. The great diversity of ethnic backgrounds has produced almost all of the religions of the world are now practiced in the United States. Christianity(基督教) is the dominant religion in American and Protestant (新教)is predominate(主导). Any individuals are equal before God and they believe they can communicate directly to God so they can share the same idea. Under the protestant, many new ones are formed and different explanations produce different sect of religion. Churches are independent and American religion is no longer religion seculars. The institution permits the practice of religion and the political power is separate form religion. So there are more religions in American than in other countries. 4. Current influence:Nowadays, we can see the continual influence of the three elements in the current American society. American family is typically parents and their unmarried children. Middle-aged and elderly people generally do not live with their married children. Many Americans live in mobile homes whose homes are built with wheels. They can be moved. The people in American have a very strong desire to start a new life in a new place. Quite a number of people change residences(住所) every year. The average American moves fourteen times in his lifetime. The courage to try something new has been an American characteristic. American democracy means majority rule, but it also means protection of minority rights. There are certain freedom which the United States promises to all its citizens and members of minority group cannot be denied these rights by a vote of the majority. Americans also like to be involved in many challenge activities and sports to show their adventurous spirits. All of these are affected by the heritage of the American history.From the facts above, we can see American culture is unique which was cultivated, formed and developed by the main three factors, rough environment, ethnic diversity and plural religion and still is affected and determined by them now.
America has traditionally been referred to as a &melting pot,& welcoming people from many different countries, races, and religions, all hoping to find freedom, new opportunities, and a better way of life. E Pluribus Unum - From Many to OneAmerican history began with waves of immigrants, bringing their own cultures and traditions to a vast new country.
No other place in the world has such a diverse population.
It is this diversity that makes America what it is and, at the same time, creates the challenges it faces.But What is American Culture?Americans come from all over the world.
A recent search for &American Culture& on Yahoo! - Regional & Countries & United States & Society and Culture & Cultures and Groups & Cultures & turned up 47 categories!
Some of these include:
AfricanAsian Arabic Brazilian Chinese Danish German Hispanic/Latino Indian Iranian IrishItalian Japanese Korean Native Americans Norwegian Philippine Polish Scandinavian Scottish Vietnamese WelshStrictly speaking, the only indigenous Americans are the American Indians who were living here long before the first waves of settlers came over from Europe.
When Christopher Columbus discovered America in 1492, he called these natives &Indians& because he thought he had discovered a western route to India.Today the trend is toward multiculturalism, not assimilation.
The old &melting pot& metaphor is giving way to new metaphors such as &salad bowl& and &mosaic&, mixtures of various ingredients that keep their individual characteristics.
Immigrant populations within the United States are not being blended together in one &pot&, but rather they are transforming American Society into a truly multicultural mosaic.The American mosaic is one of different cultures and regional identities, each with unique characteristics and flavors.
Americans often think of themselves not only as coming from a particular ethnic heritage, but also of being part of a geographical region.
Understanding these regional characteristics and flavors is an excellent way to get to know Americans. The EastNew England - Early economic and cultural center for almost two centuries.
New Englanders are known for their self-reliance, and distinctive accent, particularly in the North and in Boston. The Middle Atlantic States -known historically for the &muscle& of the American economy, the region became the center for heavy industry.
Settlers were from many different cultural backgrounds, including Dutch, Swedes, English Catholics and Protestants, and Quakers.
The South Famous for &southern hospitality&, and a very distinctive accent, known as a &southern drawl&, the South is perhaps one of the most colorful and regions in the United States.
English Protestants, many becoming rich by raising tobacco and cotton on large southern plantations, originally settled this region. The Midwest This region has been called &America's cultural crossroads and breadbasket.&
Settlers came primarily from Germany, Sweden, and Norway.
The Mississippi River, lifeline of the region, inspired the world-famous Mark Twain book, Adventures of Huckleberry Finn.TopThe Great Lakes & Great Plains The Great Lakes region, named for its many lakes, played the part of the early industrial center in American.
It is the center of the American automobile industry and the development of mass production.
The Great Plains, so named because it covers over 1,000 miles of plains and prairies, reaches from Oklahoma and Kansas to North Dakota.
Wyatt Earp, and &Wild Bill& Hickok, two legendary lawmen, ruled the frontier towns of Dodge City and Abilene.The West The American West is a geographical region, the &last frontier& to be settled in a vast country.
Settlers moved west to find new opportunity, escape religious persecution, and create a new and better way of life. The American West is also, perhaps a state of mind.
This &Frontier Spirit&, and the move westward had a significant impact on the development of American culture. In 1893, Frederick Jackson Turner's wrote his Frontier Thesis, one of the most influential models of American culture.
He suggests that the frontier played a significant role in shaping American institutions, and the &expansion westward with its new opportunities, its continuous touch with the simplicity of primitive society, furnish the forces dominating American character.& The story of the American West has traveled the world with the help of Hollywood.
John Wayne may have been a Hollywood actor, but to many, he represents many characteristics associated with American culture...
Individualistic & self-reliant
Friendly, spontaneous, & informal
Confident, arrogant, logical & direct
Creative & innovative
Great talkers and debaters
Firm believers in the written word and contractual agreements
Uncomfortable with long periods of silence
Passionate about truth, justice, and equal opportunity&Every country in the world loved the folklore of the West--the music, the dress, the excitement, everything that was associated with the opening of a new territory. It took everybody out of their own little world. The cowboy lasted a hundred years, created more songs and prose and poetry than any other folk figure. The closest thing was the Japanese samurai.&
John Wayne
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出门在外也不愁Charge Up and Go? First Ask City Hall
来源：搜狐汽车
　　For all the talk of high-tech batteries and advanced electronics, the
success of
Motor Co.'s costly bet on electric vehicles may come
down to cities such as Raleigh, N.C., making changes to old-fashioned building
codes and permitting procedures.
　　 is lobbying cities to cut red tape that delays
installation of home-charging stations for electric cars.
　　's ambition to be the first mass-marketer of electric
cars depends on making it easier, quicker and cheaper for owners to install a
charging station in their garage. That means cutting through municipal red tape
that could delay installation by weeks or even months.
　　Though electric cars often are described as plug-in vehicles, connecting 's coming electric car, the , to a
standard 120-volt wall outlet would take more than 20 hours to fill up its
lithium-ion batteries.
　　Instead, to cut the recharge time to about eight hours―the overnight charge
that car makers believe owners will tolerate―requires the installation of a
special home charging dock that operates on 220 to 240 volts. And these devices
raise safety concerns and other issues for municipal building inspectors and
permit offices unused to dealing with them.
　　That's why
has embarked on a lobbying effort to educate building
departments and simplify regulations, in addition to prodding cities to invest
in public charging stations and offer incentives for electric vehicles such as
free parking.
　　All About the
　　 hopes to make its
mass-market electric car. Some facts about the battery-powered vehicle:
　　Due on the U.S. market: December
　　Price: $33,720, before a $7,500 federal tax credit
　　Home charging station cost: About $2,200 with installation, before tax
　　Expected driving range: up to 100 miles
　　Speed: up to 90 miles per hour
　　Source:
　　"The success is somewhat outside the hands of our company," said Mark
Perry, chief of product planning for
North America.
　　Mr. Perry has racked up more than 150,000 airline miles flying around the
country to form partnerships with more than 20 governments to prepare for 's electric-car push.
　　One target was Raleigh. After four visits and a half-dozen conference calls
with , North Carolina's capital
system that will let a homeowner get a 220-volt charging-dock permit in an hour
and installation and inspection the next day. Previously, it might have taken
several days to receive a permit and up to a week or longer to get an
installation and inspection, said Frank Olafson, permit administrator for
　　"Before, the office would have taken three days just to do research" before
granting a permit, Mr. Olafson said.
　　While General Motors Co., Daimler AG and Ford Motor Co. have made the
rounds at many of the same cities for its coming electric cars,
been making a greater push, in line with its high-volume expectations for its .
　　 is building a battery factory and renovating an
assembly plant near Nashville, Tenn., to start making the
2012. The facilities will be able to build 150,000 s a year.
The car, due out in December, will cost $33,720 and be eligible for a $7,500
federal tax credit.
being driving last month at a
track in Japan.
　　 estimates a home-charging station will cost $2,200,
with about $700 being the price for the dock itself and the rest for wiring and
installation. Such expenses can be offset by a federal tax credit covering 50%
of the cost of the dock and installation for up to a total of $2,000.
　　 has contracted with AeroVironment Inc. to ply the
docks, and the Japanese car maker plans to let buyers finance both the
installation and dock with a loan that can be rolled into the price of the .
　　Customers who intend to buy a
request an in-home inspection of their house's wiring before receiving a price
quote for the charging dock. The quote will vary based on the wiring and
condition of the home. Next, an electrician will be scheduled to install the
　　Finally, a municipal inspector likely would come to ensure the dock was
properly put in.
　　The goal is to complete the entire process within five days, Mr. Perry
　　That's a highly optimistic timetable, said Enid Joffe, whose company, Clean
Fuel Connection Inc., installed thousands of charging docks in the 1990s in
hundreds more last year for
Mini E electric-car program in New York, New Jersey and .
　　While installing docks in small towns in New York for the Mini E, municipal
departments would "take your information and say you'll hear from us in three
weeks, and you'll be lucky if you get that," Ms. Joffe said.
　　Another land mine is the potential cost. About 20% of houses in which Ms.
Joffe's company installed docks required an upgrade to their electrical service,
such as a higher-amperage electrical panel, which cost several thousand
　　 is trying to smooth out the process, in part because it
will be handling most of the dealings with municipalities instead of using a
contractor such as Clean Fuel Connection. Long waits for permits or inspections
could frustrate car buyers who are used to a "sign and drive" experience with
regular cars.
　　 has already zoomed through the first wave of cities
where electric-car enthusiasm is highest, including Portland, Ore., San
Francisco and San Diego, most of which have approved some form of streamlined or
standardized permitting.
　　The second wave of cities includes places like Raleigh, while after that
will target the East Coast.
　　"As you move further and further east of the Mississippi, there is less
interest," Mr. Perry said.
　　Still, there are signs of movement in the East. Connecticut, for one, is in
the process of changing state building codes to try to give guidance to
municipalities about charging stations, but each "town and village is their own
fiefdom with their own building codes," said Jamie Young, associate legal
council for Connecticut Gov. Jodi Rell.
　　" made it clear this is a priority," said Ms. Young.
"They didn't want to be set up for failure."
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