分子生物学48742850

MolecularBiology大连理工大学Non-covalentinteractionsthatdeterminethethree-dimensionalstructureofmacromolecules•Thebiologicalpropertiesofmacromoleculearemainlydeterminedbyactivatinginteractionsthatresultsineachmoleculeacquiringauniquethree-dimensionalstructure.•Thesenoncovalentinteractionsaremuchweakerthantypicalcovalentbonds,andforanygiventypeofmacromolecule,severaloftheseweakerinteractionsmayplayaroleindeterminingthree-dimensionalstructure.MolecularBiology大连理工大学Noncovalentinteractions•TheRandomcoil缠绕–Linearpolypeptideandpolynucleotidechainscontainbondsaboutwhichthereisfreerotation.–Intheabsenceofanyintrastrand（分子内）interactions,eachmonomerwouldbefreetorotatewithrespecttoitsadjacentmonomers–Few,ifany,nucleicacidorproteinmoleculesexistinnatureasrandomcoilsbecauseofmanyinteractionsbetweenelementsofthechains–Noncovalentinteractions•Hydrogenbonds氢键•Thehydrophobicinteraction疏水作用•Ionicbonds离子键•Vanderwaalsattraction范德华力MolecularBiology大连理工大学effectsofnoncovalentinteractions•Determinethethreedimensionalstructuresofmacromolecules.–Constrain(约束)alinearchaintofoldinsuchawaythatdifferentregionsofthechain,arebroughttogether.•Disulfidebonds(二硫键;covalent)alsoaffectsthemolecularpropertiesofproteins.MolecularBiology大连理工大学Macromoleculeisolationandcharacterization•Proteins–Molecularsieves分子筛:molecularweight–Chromatography层析:charge(positivelyornegativelycharged)oraffinityproperties–Electrophoresis电泳：SDS-PAGE,chargeandsize;mostconvenientmethod–Ultracentrifugation超离心–Aminoacidsequencing–X-raycrystallographyx射线晶体学–Electronmicroscopy电子显微镜MolecularBiology大连理工大学Macromoleculeisolationandcharacterization•Nucleicacid–Genecloning–PCR:polymerasechainreaction–Molecularsieves:molecularweight–Electrophoresis:Agarosegel,mostconvenientmethod–Ultracentrifugation–Nucleotidesequencing–ElectronmicroscopyMolecularBiology大连理工大学Summary•Structuralcharacteristicsofmacromolecules•Componentsofmacromolecules•Noncovalentinteractions•Covalentbonds•Bondsfordeterminingthree-dimensionalstructure•MethodsforisolationandcharacterizationofproteinandnucleicacidsMolecularBiology大连理工大学Importantconceptsandaspectsyouarerequiredtounderstand•SmallMoleculesvsMacromolecules•Monomers,PolymersandMacromolecules•CommonMonomersinCells•WhatAAhaveincommon?Exception•WhatmakeAAunique?•DifferentcategoriesofAAandtheirspecialfeatures:formHbonds,saltbridges,disulfidebond,responsibleforUVabsorbance,etc•DandLformsofAA•4differentlevelsofproteinstructuresandtheirfeatures:basisofstructures,bondsinvolved•ChemicalcomponentsofDNAandtheirpositionsindoublehelixstructure•ImportantforcesinmaintainingDNAstibilization•DifferencebetweenDNAandRNA•DandLsugars•Monosaccharides•Disaccharides•Polysaccharides•Polysaccharides’majorroles•Peptidebond•Disulfidebond•glycosidicbond•Structuralcharacteristicsoflipids•Noncovalentinteractions•Methodsforproteinisolationandcharacterization•MethodsfornucleicacidisolationandcharacterizationTheendofchapter2MolecularBiology大连理工大学Chapter6TheGeneticMaterial遗传物质MolecularBiology大连理工大学Studyobjectives•Backgroundinformationonthemechanismsofheredity.•ExperimentalevidencethatidentifiedDNAasthegeneticmaterial.•PropertiesofDNAasthegeneticmaterial,includingstorage,transmission,stability,andmutation.MolecularBiology大连理工大学TheKeyExperimentsContributestoIdentifyingDNAasthePrimaryGeneticMaterial•1928F.Griffith/Transformation•1944O.T.Avery/FurtherConfirmation•1952A.D.HersheyandM.Chase/PhageLabelingMolecularBiology大连理工大学1928F.GriffithTransformation•Streptococcuspneumoniae(pneumococci)growingascoloniesonthesurfaceofaculturemedium.–Left:Thepresenceofacapsule(包膜）aroundthebacterialcellsgivesthecoloniesaglistening（发亮）,smooth(S)appearance.–Right:Pneumococcilackingcapsuleshaveproducedtheserough(R)colonies.MolecularBiology大连理工大学TheExperiments•Somethingintheheat-killedScellstransformedtheR-typebacteriaintoS-typecells.MolecularBiology大连理工大学TheConclusions•Therewasatransformingagentinthetheheattreatedwildtypebacteria(smooth)whichtransformedthelivemutant(rough)typebacteriatobeabletoproducewildtypebacteriacapsule.MolecularBiology大连理工大学O.T.Avery’sTestify•Background:–In1944,OswaldAveryandhiscolleaguesatTheRockefellerInstituteinNewYorkCityeventuallyshowedthatthesomethingwasDNA.–Averyextractedrelativelypurenucleicacids(DNA+RNA)frompneumococcustodeterminewhatwasthetransformingagentobservedinGriffith'sexperimentsMolecularBiology大连理工大学Avery’sTransformationExperiment-1944DeterminedthatDNAwasthegeneticmaterialresponsibleforGriffith’sresults(notRNA).MolecularBiology大连理工大学•In1952,A.D.HersheyandM.ChaseperformedanotherexperimentthatprovidedfurtherevidencethatgenesweremadeofDNA.PhageLabelingMolecularBiology大连理工大学Background•T2phageisaviruswhichinfectsthebacteriaE.coli.Thephagelookslikeatinylunarlandingmodule.•Inanycase,about20minafterthephageadsorbstothesurfaceofthebacteria,thebacteriaburstsopen(lysis)andreleasesamultitudeofprogeny(子代）virus.MolecularBiology大连理工大学LifecycleofT2phageMolecularBiology大连理工大学TheExperimentalIdea•NormalDNAcontainsonlyhydrogen,nitrogen,carbon,oxygenandphosphorousatoms–Ifthemediainwhichthebacteriagrew(an