A method of preparing molecules of interest for delivery to eukaryotic cells is shown, wherein a ricin B chain subunit not having a ribosome inactivating subunit and retaining lectin activity is modified by modifying the first cysteine residue to be absent or substituted with an amino acid other than cysteine, or removing a protease sensitive site at the N-terminal of the subunit, or adding an endoplasmic reticulum retrieval signal, and operatively associating the subunit with a molecule of interest. Methods of operatively associating the subunit and molecule of interest include chemical conjugation at primary amines, conjugation with N-glycans of the subunit, a disulfide bond, and assembly of immunoglobulin domains. The invention provides for operatively associating multiple molecules of interest with a ricin B chain subunit, and delivery into targeted cells, cell components, and combination of cells.