Bovineserumalbumin牛血清白蛋白(BSA),又称第五组分，是牛血清中的一种球蛋白，包含583个氨基酸残基，分子量为66.430kDa,等电点为4.7牛血清白蛋白在生化实验中有广泛的应用，例如在westernblot中作为BlockingagentThefull-lengthBSAprecursorproteinis607aminoacids(AAs)inlength.AnN-terminal18-residuesignalpeptideiscutofffromtheprecursorproteinuponsecretion,hencetheinitialproteinproductcontains589aminoacidresidues.Anadditional4aminoacidsarecleavedtoyieldthematureBSAproteinthatcontains583aminoacids.PhysicalpropertiesofBSA:• Numberofaminoacidresidues:583• Molecularweight:66,463Da(=66.5kDa)• isoelectricpointinwaterat25°C:4.7[i]• Extinctioncoefficientof43,824M-icm-iat279nm〔2]• Dimensions:140x40x40A(prolateellipsoidwherea=b
0.733⑸⑷• Intrinsicviscosity,n：0.0413[5][4]• Frictionalratio,f/f0:1.30[5][4]• Refractiveindexincrement(578nm)x10-3：1.90[5][4]• Opticalabsorbance,A279nm】几:0.667[5][4]• Meanresiduerotation,[m']:8443[5][4]233• Meanresidueellipticity:21.1[0];20.1[0]⑸⑷209nm222nm• Estimateda-helix,%:54[5][4]• Estimatedb-form,%:18[5][4]BSAhasnumerousbiochemicalapplicationsincludingELISAs(Enzyme-LinkedImmunosorbentAssay),immunoblots,andimmunohistochemistry.Itisalsousedasanutrientincellandmicrobialculture.^itationneeded]Inrestrictiondigests,BSAisusedtostabilizesomeenzymesduringdigestionofDNAandtopreventadhesionoftheenzymetoreactiontubes,pipettips,andothervessels.mThisproteindoesnotaffectotherenzymesthatdonotneeditforstabilization.BSAisalsocommonlyusedtodeterminethequantityofotherproteins,bycomparinganunknownquantityofproteintoknownamountsofBSA(seeBradfordproteinassay).BSAisusedbecauseofitsstabilitytoincreasesignalinassays,itslackofeffectinmanybiochemicalreactions,anditslowcost,sincelargequantitiesofitcanbereadilypurifiedfrombovineblood,abyproductofthecattleindustry.。