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1、Theglassystateofwater:A”stopandgo”deviceforbiologicalprocessesS.E.PagnottaDipartimentodiMedicinaSperimentaleeScienzeBiochimiche,Universit`adegliStudidiRoma“TorVergata”,ViaMontpellier,00100Roma,ItalyF.Bruni∗DipartimentodiFisica”E.Amaldi”,Universit`adegliStudidiRomaTreViadellaVascaNavale84,00146Ro
2、ma,ItalyAbstract.Whatisuniqueaboutthepropertiesofintracellularwaterthatpreventitsreplacementbyanothercompound?Wetacklethisquestionbycombiningex-perimentaltechniquesasdiverseasElectronSpinResonance,ThermallyStimulatedDepolarizationCurrent,broadbanddielectricspectroscopy,andneutrondiffractiontoaset
3、ofsamples,namelyaglobularenzyme,intactplantseeds,andporoussilicaglasses,largelydifferingintermsofcompositionandcomplexity.Resultsindicatethatinterfacialandintracellularwaterisdirectlyinvolvedintheformationofamor-phousmatrices,withglass-likestructuralanddynamicalproperties.Weproposethatthisglassin
4、essofwater,geometricallyconfinedbythepresenceofsolidintracellularsurfaces,isakeycharacteristicthathasbeenexploitedbyNatureinsettingupamechanismabletomatchthequitedifferenttimescalesofproteinandsolventdynamics,namelytoslowdownfastsolventdynamicstomakeitoverlapwiththemuchslowerproteinturnovertimesin
5、ordertosustainbiologicalfunctions.Additionallyandequallyimportant,thesamemechanismcanbeusedtocompletelystoporslowdownbiologicalprocesses,asaprotectionagainstextremeconditionssuchaslowtemperatureordehydration.Keywords:Water;Glassyphase;Lysozyme;Anhydrobiosis1.IntroductionWaterisoneoftheessentialc
6、omponentsoflifeanditsfunctionsaremanifold.Isthatall?Itistakenasaxiomaticthatliferequireswater,andsostrongisthebeliefthatwaterisessential,thatithasbecomeadefiningparameterforlife-ifthereisnowatertherecanbenolife.But,ascleverlypointedoutbyarecentmeetingonthemolecularbasisoflife(Danieletal.,2004),if
7、alllifereallydependsonwater,weoughttobeabletosaywhy.Whatisuniqueaboutthepropertiesofwaterthatpreventitsreplacementbyanothercompound?Whatarethebiologicalfunctionsofwateratthemolecularlevel,andwhyisitnecessary?Waterisimplicate
