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TEXTONEMostcellsaretransparent—inotherwords,theyarenotverygoodatreflectingorabsorbinglight.Tolookatthemunderamicroscopethusrequirestrickery.Manyofthesetrickskillthecells,andeventhosethatkeepthemalivelookonlyatslicesthrougheachcell,ratherthanseeingthewholethinginthreedimensions.MichaelFeld,oftheMassachusettsInstituteofTechnology,andhiscolleagues,thinktheycanchangethat.Theyhaveinventedawaytolookatcellsthatarestillalive.Moreover,theycandosointhreedimensions.Theirmethodiscalledtomographicphasemicroscopy,anditisreportedinthisweek'sNatureMethods.Insteadofrelyingonabsorbedorreflectedlight,DrFeld'stechniquecelebratestransparencybylookingatlightthatgetsthroughunaltered.Itdoessobymeasuringapropertycalledtherefractiveindex.Thisindexmeasuresthespeedoflightinamaterial.(Lightzipsalongattheactual“speedoflight”,fasterthanwhichnothingcango,onlywhenitistravellingthroughavacuum.)Thedifferentcomponentsofacell,thoughtransparent,havedifferentrefractiveindices.DrFeldandhisteamthereforesetouttomapwhatthesedifferencesare,withaviewtousingthemtodistinguishbetweencellularcomponents.Tomeasuretherefractiveindicesofdifferentpartsofacelltheyuseatechniquecalledinterferometry,whichinvolvessplittingabeamoflightintwo.Onehalf,knownastheobjectbeam,passesthroughthecell;theotherisdirectedalongadifferentpathandactsasareference.Thelengthofthereferencepathissuchthatifnosampleispresent,thetwodaughterbeamswillbeasperfectlyinphasewhentheymeetastheywerewhentheywereseparated.Thecrestsandthetroughsoftheirwaveswillreinforceeachother,andtheresultwillbebrightness.Themorethatthelightpassingthroughthesampleissloweddown,however,themorethetwobeamswillbeoutofphase.Crestwillfallontrough,andtheresultwillbedarkness.ItisthisphaseshiftthatgivesDrFeld'snewformofmicroscopyitsname.Asinglepairofbeamsdoesnot,however,produceausefulimage.Todothatrequiresscanningtheobjectbeamthroughthetargetaboutahundreddifferentways.Fromtherefractiveindexofeachpathitispossible—withtheapplicationofsomesuitablycrunchycomputingpower—toproduceathree-dimensionalimage.Totesthisidea,DrFeldlookedatcervical-cancercells.Ifyouidentifythiscancerearly,thepatientwillprobablysurvive.Missit,andshewilldie.DrFeldwonderedifthechangesthatoccurduringcancerwouldshowupusinghisnewmethod.Theydid,inapartofthecellcalledthenucleolus.Thisistheplacewherethecomponentsofproteinfactoriesaremade.Sincecancercellsgrowrapidly,andthushaveahighdemandforproteins,itwasalikelyplacetoexpectchanges.DrFeldalsohasplanstousebeamsofdifferentcolours,sinceeachcolourhasaslightlydifferentrefractiveindexinagivenmaterial.Thatwouldprovideextradataforthecomputertochewon,andprobablyresultinbetterpictures.Withenoughpictures,DrFeld'stechniquemaymakebiologyastransparentasthecellsitstudies.参考译文：大多数的细胞都是透明的，也就是说，他们没有很强的反射或吸收光的能力强。因此，要在显微镜下看到它们就需要一定的技巧了。许多技巧都会杀死这些细胞，而那些能保证它们存活的技巧使人们看到细胞的切片，而不是从三维立体的角度来观察细胞。麻省理工大学的MichaelFeld及其同事认为他们可以改变这一点。他们发明了观察活细胞的方法，而且还可以从三维立体观察到。他们的方法叫做X线断层阶段显微镜方法，于本周刊登在《自然方法》上。Feld博士不是通过那些吸收或反射的光、而是利用了细胞的透明来观察穿过后细胞没有改变的光。该方法是通过测量折射率来实现的。折射率测量光在某种物质中的速度。（光只有通过真空时才以真正的“光速”来快速移动，没有别的物体比它更快了）细胞的不同成分虽然是透明的，但是却有不同的折射率。Feld博士及其小组因此开始寻找这些不同，希望可以通过不同的折射率来辨析细胞的成分。为了估测某一细胞不同组成部分的折射率，他们使用了一种将一束光线一分为二的干涉测量方法，其中一半叫做物体光束，能穿过细胞；另外一半则沿着不同的路线前进，作为参照。参照路线的长度一定，如果没有物体，那么这两个光束就会同相，与它们分开时的情况一样。两束光的波峰和波谷会互相加强，结果就是非常明亮的光。通过物体的光度减慢越多，两个光束异相的程度就越大。此时，波峰会落到波谷，最终结果就是黑暗。正是因为相的变化，Feld博士的新显微镜方法才有了自己的名称。但是单对光束不会创造出有用的图像来。图像的生成需要将物体光束以一百种不同的方式来通过物体并进行扫描。从每条路的折射率来看，通过运用一些适当的计算力量，就有可能可以生成三维图像。为了检测这种想法，Feld博士研究了子宫癌细胞。越早辨认出该细胞，病人存货的几率就越大。如果忽略了该细胞，病人就会死亡。Feld博士想知道使用自己的新方法是不能发现癌症期间的一些变化。他们在一种名为核仁的细胞中发现了这种变化。这种细胞是生产蛋白质工厂。因为癌症细胞生长过于迅速、需要大量的蛋白质，因此这里是发生改变最有可能的地方。Feld博士还计划使用不同颜色的光束，因为每种颜色的光束在某一物质中都有略微不同的折射率。这就为计算机运行提供了更多的数据，而且可能会有更好的图像。有了足够多的图像，Feld博士的技术就可以让生物学变得透明起来，就像他研究的那些透明细胞一样。TEXTTWOForaNobellaureate,themolecularbiologistMaxPerutzmadealotofmistakes.Hissciencewasstrewnwithassertionsthatwerenotsupportedbythesparseevidencehehadgathered.Nomatter.Hewaseventuallyrightabouttheimportantthings—andgentlemanenoughtoconcedehiserrors.Withbloody-mindedpersistence,Perutzmasteredthepainstakingtaskofanalysingimagesofhaemoglobin,thecomponentofbloodthatcarriesoxygen.Thiswasnomeanfeat:amoleculeofhaemoglobinconsistsofthousandsofatomsand,atthetime,onlysimplestructuresoftensofatomshadbeenmapped.ItwasforthisworkthatPerutzwasawardedtheNobelprizeinchemistryin1962.Buthistriumphalannouncementofthecorrectstructureofhaemoglobinwasbynomeanshisfirstsolutiontotheproblem:hehadpreviouslyclaimedallsortsofunlikelyarrangements,backingdowneachtimeacolleaguespottedafatalflaw.Evenwhenhedidfinallyholdthesecrettowhybloodsupportslife,hedidnotpiecetogethertheevidencetoproducetheultimateresult.Indeed,Perutzwasfuriouswhenajuniorresearchersawhowthefinalpiecefittedandcouldnotresistpoppingitintoitsslot,completingwhatPerutzviewedashisjigsawpuzzle.Nevertheless,itwasPerutzwhohadgatheredallthepiecesandwhoensured,intheend,thattheywerecorrectlyassembled.Perutzwaslongtheoutsider.OfJewishdescent,hewasalapsedCatholicbyreligion.HelefthisnativeAustriain1936,twoyearsbeforeHitlerannexedit.TheoutbreakofwarsawhimexpelledtoCanadaasa