Covalent modification of plasma proteins by benzophenone-containing LPA analogues. Plasma (5% in PBS) from Sprague-Dawley (19.4 mg albumin/mL) A or Nagase rats (0.4 mg albumin/mL) B was incubated with compounds 1, 2, 4, 20P, or 27P (50 nM, DMSO 10% final concentration) in the dark for 30 min prior to UV irradiation for up to 10 min on ice. Samples were diluted with 2 × sample loading buffer and separated by SDS-PAGE. Gels were subsequently dried and radioactive bands were visualized by autoradiography.