Cover Story：Oligomers, rather than polymers and fibrils, of protein aggregates are thought to be cytotoxic, which is a milestone in the study of protein misfolding and aggregation. Abnormally high level of uric ribose in type 2 diabetic patients and ribosylated animal models indicate that diabetes is not only correlated with metabolic dysfunction in glucose but also ribose. Here, using ribosylation of bovine serum albumin (BSA), we show that ribosylated BSA aggregates and proceeds from a monomer and onto an oligomer and polymer, observed with fluorescence spectrophotometer, atomic force microscopy, transmission electron microscopy and size exclusion chromatography. Ribosylated monomer showed severely cytotoxic to SH-SY5Y cells (a human neuroblastoma cell line) under the observations by assays of CCK-8, LDH activity, TUNEL staining, caspase-3 activity and flow-cytometry, whereas ribosylated oligomer and polymer did not. The cytotoxic effect of the ribosylated monomer likely occurs by inducing neuronal apoptosis through activation of the receptor of AGEs (RAGE) associated with mitogen-activated protein kinases (MAPK) pathways.