**2.2. Donor eye tissue and phosphoprotein enrichment**

Human postmortem donor eye tissues were used following the tenets of the Declaration of Helsinki. Human AMD retinas (8 mm macular and peripheral punches), RPE (8 mm central and peripheral punches), and age-matched control eyes (*N* = 9, biological triplicate x technical triplicate) were provided by the Lions Eye Bank (Moran Eye Center, University of Utah). Phosphoproteome of macular (I), peripheral retina (II), central RPE (III), and peripheral RPE (IV) was compared to age-matched control donor eyes to determine region-specific senescence-associated molecular mechanisms during AMD progression. Phosphoproteins were enriched by charge-based spin column chromatography and resolved by 2D gel electrophoresis as previously reported [28]. In addition, trypsin digested phosphopeptides from whole lysates were enriched using Ga3+/TiO2 immobilized metal ion chromatography. Eluted phosphopeptides were analyzed using mass spectrometry including MALDI-TOF-TOF and ESI MS/MS.
