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Cheryl 林談蜘蛛絲的壯麗

Cheryl Hayashi: The magnificence of spider silk

 

Photo of three lions hunting on the Serengeti.

講者: Cheryl 林(Cheryl Hayashi)

2010年 2月演講,2011年12月在TED2010上線

 

翻譯:甘貞珍博士

編輯:朱學恆、洪曉慧

簡繁轉換:洪曉慧

後製:洪曉慧

字幕影片後制:謝旻均

 

影片請按此下載

MAC及手持裝置版本請按此下載

閱讀中文字幕純文字版本

 

關於這場演講

Cheryl 林研究蜘蛛絲,它是大自然中一種最佳的高性能材料。每一個品種的蜘蛛能造出七種不同的絲。蜘蛛怎麼做到的?林女士以基因層面為我們解說-並講述從這種超強韌、超靈活的天然材料中所得到的啟發。

 

關於Cheryl 林

Cheryl 林研究蜘蛛網中纖細卻強韌的蜘蛛絲,發現蜘蛛絲具有可供人類使用的驚人潛力。

 

為什麼要聽她演講

生物學家Cheryl林有充分理由為蜘蛛和蜘蛛絲著迷。蜘蛛絲含有幾種千變萬化的絲蛋白;蜘蛛共有40,000多個品種,許多種蜘蛛能製造半打以上不同類別的絲蛋白。某些蜘蛛絲有像鋼鐵一樣強的韌性—通常比鋼鐵更有韌性—同時具有像空氣一般輕柔的特性。蜘蛛能用蜘蛛絲做很多事:築窩織網、獵食、遷移、求偶和保護蜘蛛蛋。

 

林女士在美國加州大學河濱校區實驗室研究蜘蛛絲的基因組成,及其演化和特殊的生物機械性質 (並於2007年穫得麥克阿瑟「天才」獎)。她的研究工作糢糊了生物學和材料科學的界限,在最精微的分子層面上尋找蜘蛛絲奇妙的原理,並探索人類能從蜘蛛絲的奧秘中學習到什麼。林女士的工作也許能針對各種不同用途激發出新的仿天然材料產品:從能夠自然分解的釣魚線,到手術縫線和超結實的繩索及防彈衣等等。

 

「蜘蛛是我的靈感。我總是能從蜘蛛那學些新的東西,那就是我繼續研究的動力。」

Cheryl

 

Cheryl 林的英語網上資料

Home: Cheryl Hayashi at UC Riverside

 

[TED科技‧娛樂‧設計]

已有中譯字幕的TED影片目錄(繁體)(簡體)。請注意繁簡目錄是不一樣的。

 

Cheryl 林談蜘蛛絲的壯麗

 

在此,我想談談蜘蛛的壯麗,以及我們能從牠們身上學到什麼。蜘蛛是真正的世界公民,蜘蛛可以棲息在陸地上每一個角落。這個紅點標明的是北美洲的大盆地。在那兒,我和幾位伙伴合作高山物種多樣性的研究計劃,這裡是我們做野外研究的地方,為了讓你瞭解一下情況,相片中這個糢糊的小藍點是我一個伙伴。這裡的地貌既崢嶸又貧瘠,但這裡有很多蜘蛛。翻開石頭,可以看到這隻蟹形蜘蛛正在和一隻甲蟲格鬥。

 
蜘蛛們不但無所不在,而且種類繁多。已知的蜘蛛有四萬多種。這個圖形代表四萬種蜘蛛相較於四百種靈長類動物的比例。蜘蛛比靈長類足足多了一百倍。蜘蛛也是一個歷史悠久的物種。圖表下方是地質年代表,這些數字是以百萬為單位的距今年數,零點代表的是現在。所以圖表告訴我們,蜘蛛大約在距今三億八千萬年已經存在了。以圖表來看,紅色直線標明的是七百萬年前人和黑猩猩才在演化過程中分道揚鏢。
 
所有蜘蛛在生命中某個階段都會吐絲,多數蜘蛛利用大量的絲求生保命和繁衍子孫,甚至連這化石中的蜘蛛都能造絲。從這張圖我們可以看見化石中蜘蛛的噴絲器,所以這說明了蜘蛛和蜘蛛絲兩者都已存在了三億八千萬年。研究蜘蛛後不須太久,就會發現蜘蛛絲是蜘蛛生活中的必須配備。蜘蛛絲有許多用途,包括為了安全用絲做攀繩、為了繁殖用絲包住卵,或利用絲來作防護性的撤退及捕捉獵物等等。
 
蜘蛛絲有許多種。譬如園蛛能造出七種不同的絲,當你看這張蜘蛛網時,事實上你觀察的是多種不同的絲纖維網。骨架和半徑線是用一種絲織成的,而捕獵螺旋線是由兩種絲組合而成:一種絲纖維加上另一種有黏性的珠液絲。一隻蜘蛛怎麼可能造出這麼多種不同的絲呢?為了回答這個問題,我們仔細研究了蜘蛛的噴絲器。絲由噴絲器中排出體外,對我們研究蜘蛛絲的生物學家來說,我們稱噴絲器為蜘蛛的業務部。(笑聲)。我們日以繼夜地…嘿!別笑!這是我的生活。(笑聲)。我們日以繼夜地觀察蜘蛛的這個部位,這就是我們看見的。你可以看見好幾縷絲從噴絲器中伸出,因為每個噴絲器上有多個閥門,每一縷絲都由閥門中吐出。如果你沿著蜘蛛絲追溯到蜘蛛體內,你將發現每一個噴絲閥門都通往它自己專用的絲腺。絲腺就像個囊袋,裡面塞滿了絲蛋白。如果你有機會解剖一隻圓蛛,我希望你有這種機會,你會看見許多美麗的半透明絲腺。
 
每隻蜘蛛體內都有幾百個絲腺,有時甚至有幾千個。這些腺體可分成七類,它們的形狀大小不同,有時甚至連顏色都不同。在一隻圓蛛體內你會發現七種絲腺,圖中畫的是-讓我從一點鐘位置說起:這是管狀絲腺,它製造卵囊外面那層絲;這是聚狀和鞭狀絲腺,共同製造蜘蛛網上的黏性捕獵螺旋線;梨狀絲腺可製造黏著劑,也就是將東西黏住的那種絲;還有葡萄狀腺絲,可用來包裹獵物;小壺狀腺絲可用來織網。其中研究最透徹的絲線是大壺狀腺絲,它可用來織網的骨架和半徑線及安全攀繩。
 
但蜘蛛絲究竟是什麼呢?蜘蛛絲幾乎全由蛋白質組成,幾乎所有絲蛋白都可用一個基因家族來解釋,也就是說,今天我們所見的各式各樣的蜘蛛絲都是由同一個基因家族編碼決定。所以假設蜘蛛的始祖只造一種絲,經過三億八千萬年後,那個造絲基因不停地複製,不停地變異並特異化,形成今天種類繁多的蜘蛛絲。所有蜘蛛絲都有幾個共同特質-它們都有相同的生物設計;譬如它們都很長,和其它蛋白質比起來,蜘蛛絲蛋白長的離譜;絲蛋白序列的重複性很高,並含有大量的甘氨酸和丙氨酸。為了讓你們進一步認識蜘蛛絲蛋白,這是從黑寡婦蜘蛛取得的一小段攀繩絲蛋白序列,這是一種我最愛日夜觀看的蛋白質序列。(笑聲)。
 
你看見的字母是氨基酸的簡寫,我用綠色標出了甘氨酸(glycine),紅色標出丙氨酸(alanine),所以你可以看到其中有許多G(甘氨酸)和A(丙氨酸),你也可以看出其中有很多簡短、一再出現的小段序列模式,例如它有很多所謂的聚丙氨酸(polyalanines),以AAAAA表示;還有GGQ和GGY。你可將這重複性高的小段序列看做句子中一再出現的單字。舉個例子,在這個句子中有綠色段落,也有紅色的聚丙氨酸,它們一再重複,在單一絲蛋白分子中就有千百次這樣的重複。
 
同一隻蜘蛛製造出的絲蛋白可以擁有非常不同的重複序列。在螢幕上方,你看見的是來自長圓金蛛攀繩絲的重複序列單元,相當短。螢幕下方顯示的是-這是同一隻蜘蛛製造的,卵囊外層管狀絲蛋白的重複序列。你可以看到這些絲蛋白大不相同,這就是蜘蛛絲基因家族多樣性的美妙之處。你可以看見重複序列的長短和排列順序都不同,所以我再次將甘氨酸用綠色、丙氨酸用紅色、絲氨酸(serine, S)用紫色來註明。你可以看見上方的重複序列幾乎全是紅和綠的組合,下方的重複序列則有大量的紫色。我們研究蜘蛛絲的生物學家們,試著了解這些胺基酸序列和絲蛋白機械性能之間的關係。
 
好在蜘蛛絲都在蜘蛛體外,使我們在實驗室進行測試時容易多了。因為我們事實上是在空氣中進行測試,正如蜘蛛使用絲蛋白的環境,這使我們藉由拉伸測量以量化蜘蛛絲的特性,基本上就是拉扯絲的一端,進行測量的工作能順利完成。這是一幅應力曲線圖,來自對同一隻蜘蛛製造出的五種不同絲蛋白進行拉伸測量的結果。你們可以看到五種絲的表現各有千秋。特別要提的是,如果你看縱軸,標示的是應力;如果你觀察每種絲蛋白的最大應力值,可以看見其中差異極大。事實上,其中韌性最佳的是攀繩絲和大壺狀腺絲,我們猜想這是因為攀繩絲用來製造網的骨架和半徑線,所以必須相當有韌性。
 
另一方面,如果你觀察伸展度,也就是絲能伸展多長;如果你觀察最大伸展值,同樣會發現其中有極大差異,最棒的是鞭狀腺絲或捕獵螺旋絲。事實上,鞭狀腺絲能伸展到原來長度的兩倍以上。所以絲纖維的強度不同,伸展性也不同。以捕獵螺旋絲為例,它須要能拉的很長,才能耐得住獵物飛來時的撞擊;如果絲無法拉得夠長,基本上當小蟲撞網時,牠會像掉到彈跳床上而被彈開。所以如果蜘蛛網全是用攀繩絲織成的,很可能昆蟲都會被彈跑了;但藉由伸展性超強的捕獵螺旋絲,蜘蛛網能吸收撲網小蟲帶來的衝撞。
 
單單一隻小蜘蛛就能造出這麼多性質不同的絲,我們稱它們為蜘蛛的工具箱。蜘蛛用它們來應付周圍的環境。但不同種蜘蛛之間的差異又如何呢?讓我們看看不同種蜘蛛所造出的同類型蜘蛛絲。這仍是一個相當新的研究領域,但我有少許研究數據跟你們分享。這是21種蜘蛛生產的攀繩絲韌性比較結果,其中有些是圓蛛,另一些是非圓蛛種類。我們假定像這隻屬於圓蛛類的長圓金蛛(argiope)應該擁有韌性最強的攀繩絲,因為牠們必須攔截獵物。從這張韌性圖中你可以看到,圖中黑點越高代表韌性越強。
 
這21種蜘蛛的排列是根據其演化史上的位置,圖下方的演化樹顯示了牠們的基因關係。黃色代表的是圓蛛,你們看這兩個紅箭頭,指出斑絡新婦蛛(nephila clavipes)和園圃蜘蛛(araneus diadematus)的攀繩絲韌度值,這兩種蜘蛛是人造蜘蛛絲研究中投注最多時間與財力的項目,目的在於複製牠們的攀繩絲蛋白。但牠們的攀繩絲不是韌性最強的。事實上,在我們的調查中,韌性最強的攀繩絲落在白色區域中。這是一種非圓蛛類蜘蛛,這種攀繩絲是由花皮蛛(scytodes)製造的,牠是一種毒蜘蛛。花皮蛛並不造網來捕獵小蟲,而是潛伏著靜待獵物靠近,吐出絲狀的毒液來固定那隻可憐蟲。想想用一根可笑的絲來捕獵,這就是花皮蛛的覓食方式。我們並不真正了解為何花皮蛛須要如此高韌性的攀繩絲,但正是這種意想不到的結果,使物種勘探工作如此精彩而值得一搏;這種意想不到的結果使我們能盡情發揮想像力。
 
現在讓我談談各種纖維的韌度值,包括尼龍纖維、桑蠶絲-或家蠶絲,羊毛、凱夫勒(Kevlar)纖維和碳纖維。你可以看到,幾乎所有蜘蛛攀繩絲的韌性都超過它們,因為它的強度、伸展度和韌度的結合優勢,使蜘蛛絲如此不同凡響,吸引了仿生科學家的注意,所以人們轉向大自然,試著尋找新的解決之道。蜘蛛絲的強度、伸展度和韌度,結合不會引起人體免疫反應的優點,使人們對蜘蛛絲的生醫應用價值產生了濃厚的興趣。舉例來說,用它做人工韌帶、引導神經再生或當做組織增生時的支架。
 
蜘蛛絲甚至在防彈領域也有被應用的潛力,蜘蛛絲可加在防彈衣和防彈設備中,使它們比現在的防彈設備更靈活輕便。除了以上這些蜘蛛絲仿生用途以外,我個人認為研究蜘蛛絲這件事本身就非常迷人有趣,我非常喜歡在實驗室裡收到新的蜘蛛絲序列,那感覺真是太棒了(笑聲),就像是蜘蛛和我分享一個古老的秘密,這就是為什麼我打算用一輩子來研究蜘蛛絲。下次你看見蜘蛛網時,請停下腳步仔細看看,你將看見已知高性能材料中一種最超級的材料。借用一句經典兒童讀物中蜘蛛夏綠蒂說的話-絲實在是太炫了。
 
謝謝各位。
 
(掌聲)
 

 

 

以下為系統擷取之英文原文

About this Talk

Cheryl Hayashi studies spider silk, one of nature's most high-performance materials. Each species of spider can make up to 7 very different kinds of silk. How do they do it? Hayashi explains at the DNA level -- then shows us how this super-strong, super-flexible material can inspire.

About the Speaker

Cheryl Hayashi studies the delicate but terrifically strong silk threads that make up a spider's web, finding startling applications for human use.
Full bio and more links

Transcript

I'm here to spread the word about the magnificence of spiders and how much we can learn from them. Spiders are truly global citizens. You can find spiders in nearly every terrestrial habitat. This red dot marks the Great Basin of North America, and I'm involved with an alpine biodiversity project there with some collaborators. Here's one of our field sites, and just to give you a sense of perspective, this little blue smudge here, that's one of my collaborators. This is a rugged and barren landscape, yet there are quite a few spiders here. Turning rocks over revealed this crab spider grappling with a beetle.

Spiders are not just everywhere, but they're extremely diverse. There are over 40,000 described species of spiders. To put that number into perspective, here's a graph comparing the 40,000 species of spiders to the 400 species of primates. There are two orders of magnitude more spiders than primates. Spiders are also extremely old. On the bottom here, this is the geologic timescale, and the numbers on it indicate millions of years from the present, so the zero here, that would be today. So what this figure shows is that spiders date back to almost 380 million years. To put that into perspective, this red vertical bar here marks the divergence time of humans from chimpanzees, a mere seven million years ago.

All spiders make silk at some point in their life. Most spiders use copious amounts of silk, and silk is essential to their survival and reproduction. Even fossil spiders can make silk, as we can see from this impression of a spinneret on this fossil spider. So this means that both spiders and spider silk have been around for 380 million years. It doesn't take long from working with spiders to start noticing how essential silk is to just about every aspect of their life. Spiders use silk for many purposes, including the trailing safety dragline, wrapping eggs for reproduction, protective retreats and catching prey.

There are many kinds of spider silk. For example, this garden spider can make seven different kinds of silks. When you look at this orb web, you're actually seeing many types of silk fibers. The frame and radii of this web is made up of one type of silk, while the capture spiral is a composite of two different silks: the filament and the sticky droplet. How does an individual spider make so many kinds of silk? To answer that, you have to look a lot closer at the spinneret region of a spider. So silk comes out of the spinnerets, and for those of us spider silk biologists, this is what we call the "business end" of the spider. (Laughter) We spend long days ... Hey! Don't laugh. That's my life. (Laughter) We spend long days and nights staring at this part of the spider. And this is what we see. You can see multiple fibers coming out of the spinnerets, because each spinneret has many spigots on it. Each of these silk fibers exits from the spigot, and if you were to trace the fiber back into the spider, what you would find is that each spigot connects to its own individual silk gland. A silk gland kind of looks like a sac with a lot of silk proteins stuck inside. So if you ever have the opportunity to dissect an orb-web-weaving spider, and I hope you do, what you would find is a bounty of beautiful, translucent silk glands.

Inside each spider, there are hundreds of silk glands, sometimes thousands. These can be grouped into seven categories. They differ by size, shape, and sometimes even color. In an orb-web-weaving spider, you can find seven types of silk glands, and what I have depicted here in this picture, let's start at the one o'clock position, there's tubuliform silk glands, which are used to make the outer silk of an egg sac. There's the aggregate and flagelliform silk glands which combine to make the sticky capture spiral of an orb web. Pyriform silk glands make the attachment cement -- that's the silk that's used to adhere silk lines to a substrate. There's also aciniform silk, which is used to wrap prey. Minor ampullate silk is used in web construction. And the most studied silk line of them all: major ampullate silk. This is the silk that's used to make the frame and radii of an orb web, and also the safety trailing dragline.

But what, exactly, is spider silk? Spider silk is almost entirely protein. Nearly all of these proteins can be explained by a single gene family, so this means that the diversity of silk types we see today is encoded by one gene family, so presumably the original spider ancestor made one kind of silk, and over the last 380 million years, that one silk gene has duplicated and then diverged, specialized, over and over and over again, to get the large variety of flavors of spider silks that we have today. There are several features that all these silks have in common. They all have a common design, such as they're all very long -- they're sort of outlandishly long compared to other proteins. They're very repetitive, and they're very rich in the amino acids glycine and alanine. To give you an idea of what a spider silk protein looks like, this is a dragline silk protein, it's just a portion of it, from the black widow spider. This is the kind of sequence that I love looking at day and night. (Laughter)

So what you're seeing here is the one letter abbreviation for amino acids, and I've colored in the glycines with green, and the alanines in red, and so you can see it's just a lot of G's and A's. You can also see that there's a lot of short sequence motifs that repeat over and over and over again, so for example there's a lot of what we call polyalanines, or iterated A's, AAAAA. There's GGQ. There's GGY. You can think of these short motifs that repeat over and over again as words, and these words occur in sentences. So for example this would be one sentence, and you would get this sort of green region and the red polyalanine, that repeats over and over and over again, and you can have that hundreds and hundreds and hundreds of times within an individual silk molecule.

Silks made by the same spider can have dramatically different repeat sequences. At the top of the screen, you're seeing the repeat unit from the dragline silk of a garden argiope spider. It's short. And on the bottom, this is the repeat sequence for the egg case, or tubuliform silk protein, for the exact same spider. And you can see how dramatically different these silk proteins are -- so this is sort of the beauty of the diversification of the spider silk gene family. You can see that the repeat units differ in length. They also differ in sequence. So I've colored in the glycines again in green, alanine in red, and the serines, the letter S, in purple. And you can see that the top repeat unit can be explained almost entirely by green and red, and the bottom repeat unit has a substantial amount of purple. What silk biologists do is we try to relate these sequences, these amino acid sequences, to the mechanical properties of the silk fibers.

Now, it's really convenient that spiders use their silk completely outside their body. This makes testing spider silk really, really easy to do in the laboratory, because we're actually, you know, testing it in air that's exactly the environment that spiders are using their silk proteins. So this makes quantifying silk properties by methods such as tensile testing, which is basically, you know, tugging on one end of the fiber, very amenable. Here are stress-strain curves generated by tensile testing five fibers made by the same spider. So what you can see here is that the five fibers have different behaviors. Specifically, if you look on the vertical axis, that's stress. If you look at the maximum stress value for each of these fibers, you can see that there's a lot of variation, and in fact dragline, or major ampullate silk, is the strongest of these fibers. We think that's because the dragline silk, which is used to make the frame and radii for a web, needs to be very strong.

On the other hand, if you were to look at strain -- this is how much a fiber can be extended -- if you look at the maximum value here, again, there's a lot of variation and the clear winner is flagelliform, or the capture spiral filament. In fact, this flagelliform fiber can actually stretch over twice its original length. So silk fibers vary in their strength and also their extensibility. In the case of the capture spiral, it needs to be so stretchy to absorb the impact of flying prey. If it wasn't able to stretch so much, then basically when an insect hit the web, it would just trampoline right off of it. So if the web was made entirely out of dragline silk, an insect is very likely to just bounce right off. But by having really, really stretchy capture spiral silk, the web is actually able to absorb the impact of that intercepted prey.

There's quite a bit of variation within the fibers that an individual spider can make. We call that the tool kit of a spider. That's what the spider has to interact with their environment. But how about variation among spider species, so looking at one type of silk and looking at different species of spiders? This is an area that's largely unexplored but here's a little bit of data I can show you. This is the comparison of the toughness of the dragline spilk spun by 21 species of spiders. Some of them are orb-weaving spiders and some of them are non-orb-weaving spiders. It's been hypothesized that orb-weaving spiders, like this argiope here, should have the toughest dragline silks because they must intercept flying prey. What you see here on this toughness graph is the higher the black dot is on the graph, the higher the toughness.

The 21 species are indicated here by this phylogeny, this evolutionary tree, that shows their genetic relationships, and I've colored in yellow the orb-web-weaving spiders. If you look right here at the two red arrows, they point to the toughness values for the draglines of nephila clavipes and araneus diadematus. These are the two species of spiders for which the vast majority of time and money on synthetic spider silk research has been to replicate their dragline silk proteins. Yet, their draglines are not the toughest. In fact, the toughest dragline in this survey is this one right here in this white region, a non orb-web-weaving spider. This is the dragline spun by scytodes, the spitting spider. Scytodes doesn't use a web at all to catch prey. Instead, scytodes sort of lurks around and waits for prey to get close to it, and then immobilizes prey by spraying a silk-like venom onto that insect. Think of hunting with silly string. That's how scytodes forages. We don't really know why scytodes needs such a tough dragline, but it's unexpected results like this that make bio-prospecting so exciting and worthwhile. It frees us from the constraints of our imagination.

Now I'm going to mark on the toughness values for nylon fiber, bombyx -- or domesticated silkworm silk -- wool, Kevlar, and carbon fibers. And what you can see is that nearly all the spider draglines surpass them. It's the combination of strength, extensibility and toughness that makes spider silk so special, and that has attracted the attention of biomimeticists, so people that turn to nature to try to find new solutions. And the strength, extensibility and toughness of spider silks combined with the fact that silks do not elicit an immune response, have attracted a lot of interest in the use of spider silks in biomedical applications, for example, as a component of artificial tendons, for serving as guides to regrow nerves, and for scaffolds for tissue growth.

Spider silks also have a lot of potential for their anti-ballistic capabilities. Silks could be incorporated into body and equipment armor that would be more lightweight and flexible than any armor available today. In addition to these biomimetic applications of spider silks, personally, I find studying spider silks just fascinating in and of itself. I love when I'm in the laboratory, a new spider silk sequence comes in. That's just the best. (Laughter) It's like the spiders are sharing an ancient secret with me, and that's why I'm going to spend the rest of my life studying spider silk. The next time you see a spider web, please, pause and look a little closer. You'll be seeing one of the most high-performance materials known to man. To borrow from the writings of a spider named Charlotte, silk is terrific.

Thank you. (Applause)

(Applause)
 


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絲在是太炫了

Anonymous, 2012-03-25 23:11:46
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私在是太炫了
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