The performance of UVPD is compared to EThcD and HCD in the present study with a focus on O-glycosite localization and differentiation of isomeric glycoforms. One O-glycoprotein targeted is TIM-1, a key member of the T-cell/transmembrane, immunoglobulin and mucin (TIM) gene family, whose mucin domain region contains 67 potential glycosites, many of which are adjacent to one another.