Tat-NR2B9c is a 20-aa peptide, which acts as a postsynaptic density-95 (PSD-95) inhibitor, with an EC50 of 6.7 nM for PSD-95d2 (PSD-95 PDZ domain 2), and 670 nM for PSD-95d1; Tat-NR2B9c also reduces NMDA-induced p38 activation, and possesses neuroprotective efficacy.