cryopreservation erythrocyte polyethylene glycol membrane reactive oxygen species еритроцит кріоконсервування мембрана поліетиленгліколь DMSO N-acetyl-L-cysteine N-ацетил-L-цистеин N-ацетил-L-цистеїн antioxidants cord blood nucleated cells cryoprotectant cryoprotectants cryoprotective agent cytoskeleton dimethyl sulfoxide geometric parameters human cord blood hydrophobic interactions nucleated cells orientation order of membrane proteins osmotic fragility protein stages of apoptosis sucrose trolox