简介：Stableisotopesofmostimportantbiologicalelements,suchasC,H,NandO,affectlivingorganisms.Inrapidlygrowingspecies,deuteriumandtoalesserextentotherheavyisotopesreducethegrowthrate.Atleastfordeuteriumitisknownthatitsdepletionalsonegativelyimpactsthespeedofbiologicalprocesses.Asarule,livingorganisms'resist'changesintheirisotopicenvironment,preferringnaturalisotopicabundances.Thispreferencecouldbeduetoevolutionaryoptimization;anadditionaleffectcouldbeduetothepresenceofthe'isotopicreso-nance'.Theisotopicresonancephenomenonhasbeenlinkedtothechoiceofearliestaminoacids,andthusaffectedtheevolutionofgeneticcode.Totesttheisotopicresonancehypothesis,literaturedatawereanalyzedagainstquantitativeandqualitativepredictionsofthehypothesis.Fourstudiesprovidedfiveindependentdatasets,eachinverygoodquantitativeagreementwiththepredictions.Thus,theisotopicresonancehypothesisisnolongersimplyplausible;itcannowbedeemedlikely.Additionaltestingisneeded,however,beforefullacceptanceofthishypothesis.

简介：Thesurfaceglycoproteinhemagglutinin(HA)helpstheinfluenzaAvirustoevadethehostimmunesystembyantigenicvariationandisamajordrivingforceforviralevolution.Inthisstudy,theselectionpressureonHAofH5N1influenzaAviruswasanalyzedusingbioinformaticsalgorithms.Mostoftheidentifiedpositiveselection(PS)siteswerefoundtobewithinoradjacenttoepitopesites.SomeoftheidentifiedPSsitesareconsistentwithpreviousexperimentalstudies,providingfurthersupporttothebiologicalsignificanceofourfindings.ThehighestfrequencyofPSsiteswasobservedinrecentstrainsisolatedduring2005–2007.PhylogeneticanalysiswasalsoconductedonHAsequencesfromvarioushosts.Viraldriftisalmostsimilarinbothavianandhumanspecieswithaprogressivetrendovertheyears.OurstudyreportsnewmutationsinfunctionalregionsofHAthatmightprovidemarkersforvaccinedesignorcanbeusedtopredictisolatesofpandemicpotential.