his dataset examines the proteomic remodeling of phase-separated protein condensates in response to high-magnesium stimulation, utilizing discontinuous sucrose density gradient ultracentrifugation combined with ultra-low input mass spectrometry. RIPA cell lysates were layered onto a stepwise sucrose gradient (10%, 22.5%, and 35% from bottom to top) and centrifuged at 250,000 g for 4 hours at 4°C. Three fractions (top, middle, and bottom 35% dense layer) were collected post-centrifugation. To identify putative phase-separation candidates, we compared protein distribution in every density bottom fraction between human PASMC cells with low endogenous UBXN1 expression and human cells overexpressing UBXN1 under high-magnesium treatment (24–48 h).