Protein phosphorylation is a major post-translational modification and it plays a pivotal role in numerous cellular functions. We present a composition that includes a soluble nanopolymer core functionalized with groups having an affinity for either metal ion or metal oxides which can be used for phosphopeptide enrichment. Exemplary compounds including PolyMAC-Zr, PolyMAC-Fe and PolyMAC-Ti demonstrate outstanding reproducibility, exceptional sensitivity, fast chelation time, and high phosphopeptide recovery from standard mixtures that include phosphorylated peptides. The composition can be used for phosphoproteome isolation from samples of medicinal, diagnostic or biological interest such as malignant breast cancer cells. Such compositions were used for the quantitative analysis of the changes in the tyrosine phosphoproteome in highly invasive breast cancer cells after induction of Syk kinase, a potent suppressor of tumor growth and metastasis. The composition and method disclosed herein offers an efficient and widely applicable tool for phosphoproteomics.