Rogue theory of smell gets a boost

1.A controversial theory of how we smell, which claims that our fine sense of odour depends on quantum mechanics, has been given the thumbs up by a team of physicists.

2.Calculations by researchers at University College London (UCL) show that the idea that we smell odour molecules by sensing their molecular vibrations makes sense in terms of the physics involved.

3.That's still some way from proving that the theory, proposed in the mid-1990s by biophysicist Luca Turin, is correct.But it should make other scientists take the idea more seriously.

4."This is a big step forward," says Turin, who has now set up his own perfume company Flexitral in Virginia.He says that since he published his theory, "it has been ignored rather than criticized."

5.Most scientists have assumed that our sense of smell depends on receptors in the nose detecting the shape of incoming molecules, which triggers a signal to the brain.This molecular 'lock and key' process is thought to lie behind a wide range of the body's detection systems: it is how some parts of the immune system recognise invaders, for example, and how the tongue recognizes some tastes.

6.But Turin argued that smell doesn't seem to fit this picture very well.Molecules that look almost identical can smell very different — such as alcohols, which smell like spirits, and thiols, which smell like rotten eggs.And molecules with very different structures can smell similar.Most strikingly, some molecules can smell different — to animals, if not necessarily to humans — simply because they contain different isotopes (atoms that are chemically identical but have a different mass).

7.Turin's explanation for these smelly facts invokes the idea that the smell signal in olfactory receptor proteins is triggered not by an odour molecule's shape, but by its vibrations, which can enourage an electron to jump between two parts of the receptor in a quantum-mechanical process called tunnelling.This electron movement could initiate the smell signal being sent to the brain.

8.This would explain why isotopes can smell different: their vibration frequencies are changed if the atoms are heavier.Turin's mechanism, says Marshall Stoneham of the UCL team, is more like swipe-card identification than a key fitting a lock.

9.Vibration-assisted electron tunnelling can undoubtedly occur — it is used in an experimental technique for measuring molecular vibrations."The question is whether this is possible in the nose," says Stoneham's colleague, Andrew Horsfield.

10.Stoneham says that when he first heard about Turin's idea, while Turin was himself based at UCL, "I didn't believe it".But, he adds, "because it was an interesting idea, I thought I should prove it couldn't work.I did some simple calculations, and only then began to feel Luca could be right." Now Stoneham and his co-workers have done the job more thoroughly, in a paper soon to be published in Physical Review Letters.

11.The UCL team calculated the rates of electron hopping in a nose receptor that has an odorant molecule bound to it.This rate depends on various properties of the biomolecular system that are not known, but the researchers could estimate these parameters based on typical values for molecules of this sort.

12.The key issue is whether the hopping rate with the odorant in place is significantly greater than that without it.The calculations show that it is — which means that odour identification in this way seems theoretically possible.

13.But Horsfield stresses that that's different from a proof of Turin's idea."So far things look plausible, but we need proper experimental verification.We're beginning to think about what experiments could be performed."

14.Meanwhile, Turin is pressing ahead with his hypothesis."At Flexitral we have been designing odorants exclusively on the basis of their computed vibrations," he says."Our success rate at odorant discovery is two orders of magnitude better than the competition." At the very least, he is putting his money where his nose is.

Questions 5-9

Complete the sentences below with words from the passage.Use NO MORE THAN THREE WORDS for each answer.

5.The hypothesis that we smell by sensing the molecular vibration was made by ______.

6.Turin's company is based in ______.

7.Most scientists believed that our nose works in the same way as our ______.

8.Different isotopes can smell different when ______ weigh differently.

9.According to Audrew Horsfield, it is still to be proved that ______ could really occur in human nose.

We have been importing and exporting all kinds of metals and minerals for 30 years and have many customers and friends in over 80 countries and regions.

Wearetooheavilycommittedtobeabletoentertainfreshorders.

----- What about the pen you bought yesterday?

-----It ____________ well.I like it very much .

Don't wash those fossils!

Standard museum practice can wash away DNA.

1.Washing, brushing and varnishing fossils — all standard conservation treatments used by many fossil hunters and museum curators alike — vastly reduces the chances of recovering ancient DNA.

2.Instead, excavators should be handling at least some of their bounty with gloves, and freezing samples as they are found, dirt and all, concludes a paper in the Proceedings of the National Academy of Sciences today.

3.Although many palaeontologists know anecdotally that this is the best way to up the odds of extracting good DNA, Eva-Maria Geigl of the Jacques Monod Institute in Paris, France, and her colleagues have now shown just how important conservation practices can be.This information, they say, needs to be hammered home among the people who are actually out in the field digging up bones.

4.Geigl and her colleagues looked at 3,200-year-old fossil bones belonging to a single individual of an extinct cattle species, called an aurochs.The fossils were dug up at a site in France at two different times — either in 1947, and stored in a museum collection, or in 2004, and conserved in sterile conditions at -20 oC.

5.The team's attempts to extract DNA from the 1947 bones all failed.The newly excavated fossils, however, all yielded DNA.

6.Because the bones had been buried for the same amount of time, and in the same conditions, the conservation method had to be to blame says Geigl."As much DNA was degraded in these 57 years as in the 3,200 years before," she says.

Wash in, wash out

7.Because many palaeontologists base their work on the shape of fossils alone, their methods of conservation are not designed to preserve DNA, Geigl explains.

8.The biggest problem is how they are cleaned.Fossils are often washed together on-site in a large bath, which can allow water — and contaminants in the form of contemporary DNA — to permeate into the porous bones."Not only is the authentic DNA getting washed out, but contamination is getting washed in," says Geigl.

9.Most ancient DNA specialists know this already, says Hendrik Poinar, an evolutionary geneticist at McMaster University in Ontario, Canada.But that doesn't mean that best practice has become widespread among those who actually find the fossils.

10.Getting hold of fossils that have been preserved with their DNA in mind relies on close relationships between lab-based geneticists and the excavators, says palaeogeneticist Svante P bo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.And that only occurs in exceptional cases, he says.

11.P bo's team, which has been sequencing Neanderthal DNA, continually faces these problems."When you want to study ancient human and Neanderthal remains, there's a big issue of contamination with contemporary human DNA," he says.

12.This doesn't mean that all museum specimens are fatally flawed, notes P bo.The Neanderthal fossils that were recently sequenced in his own lab, for example, had been part of a museum collection treated in the traditional way.But P bo is keen to see samples of fossils from every major find preserved in line with Geigl's recommendations — just in case.

Warm and wet

13.Geigl herself believes that, with cooperation between bench and field researchers, preserving fossils properly could open up avenues of discovery that have long been assumed closed.

14.Much human cultural development took place in temperate regions.DNA does not survive well in warm environments in the first place, and can vanish when fossils are washed and treated.For this reason, Geigl says, most ancient DNA studies have been done on permafrost samples, such as the woolly mammoth, or on remains sheltered from the elements in cold caves — including cave bear and Neanderthal fossils.

15.Better conservation methods, and a focus on fresh fossils, could boost DNA extraction from more delicate specimens, says Geigl.And that could shed more light on the story of human evolution.

(640 words nature )

Glossary

Palaeontologists 古生物学家

Aurochs 欧洲野牛

Neanderthal (人类学)尼安德特人，旧石器时代的古人类。

Permafrost (地理)永冻层

Questions 1-6

Answer the following questions by using NO MORE THAN THREE WORDS for each answer.

1.How did people traditionally treat fossils?

2.What suggestions do Geigl and her colleagues give on what should be done when fossils are found?

3.What problems may be posed if fossil bones are washed on-site? Name ONE.

4.What characteristic do fossil bones have to make them susceptible to be contaminated with contemporary DNA when they are washed?

5.What could be better understood when conservation treatments are improved?

6.The passage mentioned several animal species studied by researchers.How many of them are mentioned?

Questions 7-11

Do the following statements agree with the information given in the passage? Please write TRUE if the statement agrees with the writer FALSE if the statement does not agree with the writer NOT GIVEN if there is no information about this in the passage.

7.In their paper published in the Proceedings of the National Academy of Sciences，Geigl and her colleagues have shown what conservation practices should be followed to preserve ancient DNA.

8.The fossil bones that Geigl and her colleagues studied are all from the same aurochs.

9.Geneticists don't have to work on site.

10.Only newly excavated fossil bones using new conservation methods suggested by Geigl and her colleagues contain ancient DNA.

11.Paabo is still worried about the potential problems caused by treatments of fossils in traditional way.

Questions 12-13

Complete the following the statements by choosing letter A-D for each answer.

12.“This information” in paragraph 3 indicates:

[A] It is critical to follow proper practices in preserving ancient DNA.

[B] The best way of getting good DNA is to handle fossils with gloves.

[C] Fossil hunters should wear home-made hammers while digging up bones.

[D] Many palaeontologists know how one should do in treating fossils.

13.The study conducted by Geigl and her colleagues suggests:

[A] the fact that ancient DNA can not be recovered from fossil bones excavated in the past.

[B] the correlation between the amount of burying time and that of the recovered DNA.

[C] the pace at which DNA degrades.

[D] the correlation between conservation practices and degradation of DNA.