The invention concerns a water soluble vinyl membrane-polymer protein amphiphilic complex, characterised in that said vinyl polymer corresponds to formula (I) in which: R.sub.1 is a group: COO.sup..crclbar. M.sup.+ M.sup.+ being an alkaline cation, COOR.sub.7, R.sub.7 being a sugar radical; polyoxyalkylene, polyoxyethylene; N-pyrrolidonyl; phenyl sulphonate; CONR.sub.8 R.sub.9, R.sub.8 and R.sub.9 identical or different being hydrogen atom, a sugar radical, polyoxyalkylene, in particular polyoxyethylene, a zwitterion radical; R.sub.4, R.sub.5, R.sub.6 identical or different are hydrogen atom, or methyl radical; R.sub.2 is a COOR.sub.12 or CONR.sub.13 R.sub.14 radical, R.sub.12 being a linear or branched alkyl or alkylene radical; R.sub.13, R.sub.14 identical or different have one of the meanings of R.sub.12, and moreover one of the two can correspond to hydrogen atom; R.sub.3 is a COOR.sub.15 or CONR.sub.16 R.sub.17 radical; R.sub.15 being a (C.sub.1 -C.sub.5) alkyl radical; R.sub.16, R.sub.17 having one if the meanings of R.sub.15 and moreover one of the two can correspond to hydrogen atom; x, y, z correspond to the respective percentages of units. The complex is applicable for producing reagent and diagnosis kits. ##STR1##
