Amino acid composition and sequence (especially hydrophobic ones) Type of bonding (hydrophobic, ionic, hydrogen) directs protein folding and conformations Association with membranes Rapid protein resynthesis Activation or denaturation energy required Ionic strength Presence of cations (Ca+2, Mg+2, K+, NH4+) Heat shock proteins, glycosylated proteins Salt bridges and aggregation Unique stabilizing factors Polyamines Polyols (glycerol) Trehalose