protein filaments caught in the act
蛋白质细丝的行为。
grant j. jensen*
cells can be thought of as little chemical processing plants, but they also
细胞可以被看做小型化工加工工厂，但他们也能完成一些了不起的物。
accomplish some marvelous physical and mechanical tasks such as
理和机械工作，例如把自己塑造成特有的形状，朝营养素处移动，组。
shaping themselves into characteristic forms, moving toward nutrients,
织复杂的内部结构，复制、分离dna。
organizing their complex interiors, replicating and then segregating their dna, and dividing (1it has long been understood how in
人们很早就认识到真核细胞中的大部分工作是由它的细胞骨架细丝---一种细胞。
eukaryotes most of this work is done by cytoskeletal filaments –long
中的细丝网状或束状的长的蛋白质聚合物来担当的。
protein polymers that are used like cables, tracks, and bea ms in the machinery of the cellbut until about a decade ago, it was a
但是直到大约十年前，细菌细胞如何完成同样的工作仍是个谜团。
mystery as to how bacterial cells did the same tasks. none of the
当时任何一种科技，包括传统的电子显微学方法，都不能令人信服地。
existing technologies, including "traditional" electronmicroscopy
在细菌细胞中发现类似的细胞骨架细丝。
methods, had convincingly revealed analogou cytoskeletal filaments in bacteria. as a result, the lack of a cytoskeleton became widely
结果，缺乏细胞骨架被普遍认为是原核细胞的一个区别性特征。
regarded as a distinguishing characteristic of prokaryotic cells. now, on page 509 of this issue (2), salje et direct images of
关于本问题，在509页，salje等展示了与dna离析有关的一条细菌细胞骨架细。
an important bacterial cytoskeletal filament responsible for dna segregation 丝的图像。
the findings of salje et al. add to a series of discoveries that h**e firmly
salje等的发现坚定地反驳了原核生物细胞没有细胞骨架的观点。
debunked the idea that prokaryotes lack a cytoskeleton (3). first, improvements in light and immunoelectron microscopy led to
首先，光的改善和免疫电子显微镜的使用帮助确认了一些拉长成细丝形。
the identification of several bacterial proteins whose elongated location
的聚合物的细菌蛋白质的存在patterns suggested that they were polymerizing into filaments (4next, a series of stunning crystal structures showed that many of these其次，一系列惊人的晶状结构的存在表明了这些细丝形蛋白质中的
proteins had the same structures as known eukaryoticytoskeletal 许多与已知的真核状态的细胞骨架蛋白质有着相同的结构。
proteins.
in vitro biochemistry then demonstrated how some of these proteins did体外生物化学展示了其中一些蛋白质的确形成了具有完成所有。
in fact form dynamic filaments with all the properties required to 细胞骨架功能特性的动态细丝。
perform cytoskeletal functions (6but seeing is believing,
眼见为实，接下来的几年中，低温电子显微学（cryo-em）方法的发 development of cryoelectron microscopy (cryo-em) methods has in just
展使得大量的细菌细胞骨架细丝能够在细胞内部工作时直接成像。
the past few years allowed a number of bacterial cytoskeletal filaments to be imaged directly, inside cells, doing their jobs.
the key was that the development of cryo-em methods allowed samples 低温电子显微学方法的关键在于把要成像的样本冻结在一个它在与to be imaged frozen in a near-native, lifelike state, thus bypassing the
细胞内的生化环境相似的环境中，然后进行化学固定，脱水，塑料埋置，着色这。
harsh preparative procedures of chemical fixation, dehydration, plastic 些传统电子显微镜所苛求的准备性工作。
embedment, and staining required by traditional electron microscopy. because cytoskeletal filaments h**e now been seen frequently within 因为现在通过低温微电子显微法能够经常看到细菌中的细胞骨架细丝，看 bacteria through cryo-em techniques, it appears that the harsher 来更加苛刻的“传统”技术仅仅是没能较好的保存住这种结构。 "traditional" techniques simply failed to preserve such fine structuresas a second major recent advance, electron tomographic methods h**e 近年来另一个主要的进步是x线体层照相术的发展，它使得整个小细 been developed that allow entire small cells, not just sections of cells, to胞，而不是细胞的部分区域，能够在三维中成像。
be imaged in three dimensions (7this allows filaments that 这使得在二维中由于弯曲或卷曲而不能成像的细丝也可被发现和跟踪。 bend and curve, and therefore might be missed in a single planar section, to be recognized and followed.
unfortunately, although these advances h**e opened a completely new 不幸地是，这些对某些种类细菌的超微结构打开了全新窗口的技术发 window into the ultrastructure of several bacterial species (8), they 展并不能直接适用于大肠埃希氏菌。因为低温微电子显微技术使用的高能量电。
were not immediately applicable to the bacterium escherichia coli 子只能穿透生物材料的0.5m，而大肠埃希氏菌自外部约大于0.5m以内是because the high-energy electrons typically used in cryo-em can only 无弹性分散的结构（这会导致图像丢失），因此它属于过厚而无法正确成像。
penetrate about 0.5 m of biological material before being inelastically
scattered (and thus lost to the image). e. coli cells are, unfortunately, just larger than this, and are therefore problematically thickthis is a major disappointment, because e.
coli is by far the most studied 这对研究是一个很大的不利方面，因为大肠埃希氏菌是被研究最多的细菌 bacterium (and possibly the most studied cell of any type), and images of （可能还是所有类型细胞中研究最多的），而且由于它的很多复杂的生its putative cytoskeleton are in high demand, as so much is already 物学特征已被人所知，所以对它的细胞骨架成像要求很高。
科技英语作文翻译
生活中新的技术 众所周知，如今科技的发展给我们的日常生活带来极大的便利，那么到底有哪些便利呢？手机通信让我们在哪都能和朋友聊天。看书已经不是非得在纸质书上，还能在电子书上。手提式的电脑越做越薄，让我们在户外也能轻松上网。当然这些便利来自于先进的技术。比如超高的屏幕像素让我们体验更清晰的影像。更快的处...
科技英语翻译
unit 1 1.除非能以较低的 更好的质量以及更短的交货时间推出新产品，否则任何企业都无法在当今的国际竞争中立足。2.设计过程始于由市场人员认定的用户需求，止于对产品的完整描述，通常用制图来表现。3.例如 尺寸缩小，表示一张薄的材料可由具有厚度属性的等效曲面来代表，或一个细长区域可由具有截面特性的...
科技英语翻译
第一单元。电脑技术。引言。cad cam的核心部分是数字计算机。它固有的速度以及存储能力使得它能够在图像处理 实时过程控制以及很多因太复杂太费时而人工无法完成的其他重要功能方面获得进步。要想懂得cad cam，熟悉数字电脑的概念和技术是很重要的。现代数字电脑是一部能够根据预定的程序来完成数学和逻辑运...