SEARCH Articles Figures Tables Cinchona Alkaloid Derivatives with a Sulfonamide, Urea, Thiourea, Squaramide, or Guanidine Function Kidney function tests urea measurement Porphyrin Urea-functionalized Renal function tests urea measurement Urea cycle function Urea cycle function, primary Urea tertiary amine-functionalized Urea-based functional monomer Urethane/urea chemistry functional groups