Agenetically engineered dis 岨 fide ・ deficient variant ef hen lysozyme ( OSS ) 1 in which the eight Cys residues are repluced by Ser or Ala, is i皿 t血 sically denatured in its monome 【ic state . The OSS is reported 駄)spontaneously fc )rm an a皿 yloid − like fiber under mild acidic eondi − tions with certain ionic strength ( Niraura ct all PNAS 101 , 4089, 2004 ). E ) tarnination by AFM reveals that the OSS fomns protefibrilS 〔 Kamatari et a1 . , J. MoL BioL, in press , 2005 ) . In the present

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... , we have studied the growth and the sive diStribut − ion of protofibrilS from OSS using ato 血 c f' 〕r microscepy ( AFM ) 、 Under a solution condition containing 20mM sodium acetate and 30mM NaC1 , pH4 . O , the OSS molecules at 5 mg ! mL form protofiblils which grows rapidly ( Within a few hours ) up to 150 nm . During this time , CD spec − tral changes take place from random − coil to bcta form . The length distribution of the protofibnl apProxh 皿 ately follcrws an ercponentially d reash 鳴 function of length as theoretically pred並 cted . Press旺 「 e jump Teal −t血 e IH NMR wa8 apphed to study tレe kinetic process of association and dissociation of OSS . The experiments show that the f(〕mation of the protofibrils 血Uy reversible under pressure , The proMe of the protofibril gmwth observed by AFM ε皿 d the kinetic process observed by NMR are cQns te皿t wlth the two growth med 夏 訃 niSms of the pretoribrils , i. e . , the addition of monomers t。 the temini of the protofibrils at the early phase ofthe groWth and the end − t〔Lend jo 血 ing Qf already gエown protefibrils at the ter phase of the gloWth,