Insights into cell membranes via dish detergent - Ethan Perlstein

Transcriber: Andrea McDonough Reviewer: Bedirhan Cinar

翻译人员: Wenting Xu 校对人员: Cissy Yun

Every cell in your body

你身体里的每个细胞

is separated from those around it

隔离它与外界环境的

by its outermost layer,

是它最外面的一层膜

its membrane.

它叫做细胞膜

A cell membrane must be both sturdy and flexible.

细胞膜必须兼具坚固性和柔韧性

Imagine a membrane made of metal -

想象一层由金属做成的细胞膜

great at keeping the cell's guts inside,

它可以很好地保护细胞内部

but horrible at letting materials flow in and out.

却不能让物质轻松进出细胞

But a membrane made of fishnet stocking

但是如果细胞膜由网眼丝袜做成

would go too far in the opposite direction -

将可能会有完全相反的性质

leaky, but easily torn.

容易渗漏，但也易被损坏

So, the ideal membrane falls somewhere in the middle.

所以理想的细胞膜介于这两种之间。

Over the past few centuries,

在过去的几个世纪中

we've learned a lot about the way membranes work.

我们了解了很多关于细胞膜运作的方式

The tale starts in the late 1800's

故事要从17世纪晚期说起

when, according to legend,

根据传说，那个时候

a German woman named Agnes Pockels was doing dishes.

一个叫 Agnes Pockels 的德国女人正在洗盘子。

Her observation, that not all detergents

她发现，并不是所有的去污剂

dissolve grease in the same way,

都通过同一种方式溶解油脂，

piqued her curiosity,

这种发现激起了她的好奇心，

so she made careful measurements

所以她仔细测量了

of the size of soapy films

金属盘中的

that formed on the surface

水表面的

of a metal tray filled with water.

肥皂层的厚度

Later, in the 1920's, GE scientists

接着，在18世界20年代，两位通用电气科学家

Irving Langmuir and Katharine Blodgett

Irving Langmuir 和 Katharine Blodgett

reexamined the problem with a more elaborate contraption

通过更精良的设备重新检视了这个问题

and found that those tiny slicks

他们发现那一层浮层

were in fact a single layer of oil molecules.

实际上是一个单层的油分子层

Each oil molecule has one side

每个油分子有一段

that loves water and floats on the surface,

亲水并与水的表面接触，

and one side that loathes water

和另一侧疏水的部分

and protrudes into the air.

面对空气

So what does it have to do with cell membranes?

那么这跟细胞膜有什么关系呢？

Well, at the turn of the 20th century,

在20世纪初的时候，

chemists Charles Overton and Hans Meyer

化学家 Charles Overton 和 Hans Meyer

demonstrated that the cell membrane

表明细胞膜

is composed of substances that,

是有某种结构的物质组成，

like oil,

像油分子，

have a water-loving part

有亲水的部分

and a water-loathing part.

和疏水的部分。

We now call these substances lipids.

我们现在叫这个物质脂质

In 1925, two scientists,

在1925年，有两位科学家

Evert Gorter and Francois Grendel,

Evert Gorter 和 Francois Grendel

pushed our understanding further.

帮我们更近一步理解了这个问题

They designed an experiment meant to test

他们设计了一个实验来测定

whether cell membranes

细胞膜是否

are made of only one layer of lipids,

是由一层脂质组成

a monolayer,

即单层膜

or two layers stacked on top of one another,

还是双层 -- 就是一层叠加在另一层上面，

called a bilayer.

叫做双层膜

Gorter and Grendel drew blood

Gorter 和 Grendel 抽取了各种来源的血液

from a dog,

包括狗、

a sheep,

羊、

a rabbit,

兔子、

a goat,

a guinea pig,

山羊、

豚鼠、

and human volunteers.

还有人类志愿者

From each of these samples,

在这些血液样品中

they extracted all the lipids

他们把所有的脂质

from all the red blood cells

从所有的红血球中萃取出来

and placed a few drops of this extract

然后滴了几滴萃取液

on a tray of water.

到盛着水的盘子里

True to form, the lipids, like oil,

不出所料，脂质，就像油分子

spread out into a monolayer,

分散开来形成一个单层膜

whose size Gorter and Grendel could measure.

Gorter 和 Grendel 能够测定它的面积

If they compared the surface area of that monolayer

如果他们把单层膜的表面积和

to the surface area to the intact red blood cells,

红细胞表面积比较

they'd be able to tell

他们就能得出

whether the red blood cell membrane

是否红细胞的细胞膜

is one or two layers thick.

是一层还是两层

To understand the design of their experiment,

为了理解他们实验的设计

imagine looking down at a sandwich.

想象你正俯视着一个三明治

If you measure the surface area of what you see,

如果测量你看到部分的表面积

you'll get the dimensions of a single slice of bread

你将会得到一片面包的大小

even though there are two slices,

即使三明治是由两片面包组成的

one stacked perfectly atop the other.

上面的一片完全遮住在下面一片

But, if you open the sandwich

但是如果你分开三明治，

and place the two slices side by side,

把这两片面包并排放后测量

you get twice the surface area.

你得到的面积是刚才的两倍。

The Gorter and Grendel experiment

Gorter 和 Grendel 的实验

is basically the same idea.

是同一道理

The open sandwich is the monolayer formed

分开的三明治就如同

by extracted cellular lipids spreading out into a sheet.

萃取的脂质分散开来形成的单分子层

The closed sandwich is the intact red blood cell membrane.

未分开的三明治代表红血球细胞的细胞膜

Low and behold, they observed a two-to-one ratio,

他们惊奇地发现了2：1的比例

proving beyond the shadow of a doubt

证明了

that a cell membrane is a bilayer,

细胞膜是双分子层

which when unstacked,

当打开它时

yields a monolayer twice its size.

得到一个其双倍的面积

So almost 30 years before the double-helix structure

三十年前，DNA双螺旋结构

of DNA was elucidated,

还未被弄清前

a single experiment

一个涉及

involving fancy versions of household materials

家居日常用品的实验

enabled deep insight

使人们对细胞

into the basic architecture of the cell.

基本结构有了深刻的认识