METHOD1: Formaldehydepreservative–2%formaldehydesolutioninprotein-freephosphate-bufferedsaline(PBS). Prepareasfollows: Add2gparaformaldehydepowder(e.g.,Sigma,St.Louis,MO)to100mlof1XPBS.Heatto70°C(donotexceedthistemperature)inafumehooduntiltheparaformaldehydegoesintosolution(notethatthishappensquicklyassoonasthesUSPensionreaches70°C).Allowthesolutiontocooltoroomtemperature.AdjusttopH7.4using0.1MNaOHor0.1MHCl,ifneeded.Filterandstoreat4°Cprotectedfromlight. METHOD2: Formaldehydepreservative–2%formaldehydesolutioninprotein-free PBS. Prepareasfollows: 10%formaldehyde* 20ml10xPBS 10mlDistilledwater 70ml *10%formaldehydesolution(e.g.,polysciences,Warrington,PA,ultrapure,Cat.#04018),depolymerizedparaformaldehyde,EMgrade,methanol-freesolution.