Thiocyanate (SCN–) is known to be a naive ion abundant in biological fluids, blood, and urine. It is also used as a biomarker, as it can penetrate to the brain by crossing the blood brain barrier (BBB) and also gets into the cerebrospinal fluid (CSF) through the blood-CSF barrier. Considering its importance in human physiology, we examine the effect of SCN– ions on three model proteins: ovalbumin (Ova), bovine serum albumin (BSA), and lysozyme (Lys). We observe that an elevated level of SCN– (∼0.5 M) leads to an otherwise unusual instant fibrilization of all these proteins at pH 2 at ambient temperature. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) reveal two distinct initial amyloid-aggregated states: nucleus, protofibril, and two mature fibril states (upon 24 h of incubation): cross-linked network or matrix and bundle-like structures. Despite the structural variation of the …