Therapeutic compounds and methods for modulating amyloid aggregation in a subject, whatever its clinical setting, are described. Amyloid aggregation is modulated by the administration to a subject of an effective amount of a therapeutic compound of the formula or a pharmaceutically acceptable salt or ester, such that modulation of amyloid aggregation occurs. R1 and R2 are each independently a hydrogen atom or a substituted or unsubstituted aliphatic or aryl group. Z and Q are each independently a carbonyl (C═O), thiocarbonyl (C═S), sulfonyl (SO2), or sulfoxide (S═O) group. “k” and “m” are 0 or 1, provided when k is 1, R1 is not a hydrogen atom, and when m is 1, R2 is not a hydrogen atom. In an embodiment, at least one of k or m must equal 1. “p” and “s” are each independently positive integers selected such that the biodistribution of the therapeutic compound for an intended target site is not prevented while maintaining activity of the therapeutic compound. T is a linking group and Y is a group of the formula -A X wherein A is an anionic group at physiological pH, and X is a cationic group.