PPIB and dementia: Although the soluble oligomeric component of these extracts may play a role in cognitive decline, the fact that the proportion of extractable (SDS, guanidine hydrochloride, formic acid) to freely soluble Αβ is extremely high 27, 41 suggests that the less soluble forms requiring dissolution in guanidine hydrochloride are likely to be of significance in the dementia process.