Urea reduction ratio: For the Scottish river see: Urr WaterRenal functionAmmonia transporterDodecameric protein: A dodecameric protein has a quaternary structure consisting of 12 protein subunits in a complex. Dodecameric complexes can have a number of subunit 'topologies', but typically only a few of the theoretically possible subunit arrangements are observed in protein structures.Nitrogen deficiencyDenaturation midpoint: Assuming two-state protein folding, denaturation midpoint is defined as that temperature (Tm) or denaturant concentration (Cm) at which both the folded and unfolded states are equally populated at equilibrium. Tm is often determined using a thermal shift assay.Renal medullaTripartite ATP-independent periplasmic transporter: Tripartite ATP-independent periplasmic transporters (TRAP transporters) are a large family of solute transporters found in bacteria and archaea, but not in eukaryotes, that appear to be specific for the uptake of organic acids. They are unique in that they utilize a substrate binding protein (SBP) in combination with a secondary transporter.CreatinineProtein toxicity: Protein toxicity with proteinuria can result in those with preexisting kidney disease, or those who have lost kidney function due to age.ArginaseKidney: The kidneys are bean-shaped organs that serve several essential regulatory roles in vertebrates. They remove excess organic molecules from the blood, and it is by this action that their best-known function is performed: the removal of waste products of metabolism.Ligase: In biochemistry, ligase (from the Latin verb ligāre — "to bind" or "to glue together") is an enzyme that can catalyze the joining of two large molecules by forming a new chemical bond, usually with accompanying hydrolysis of a small pendant chemical group on one of the larger molecules or the enzyme catalyzing the linking together of two compounds, e.g.Proteinogenic amino acid: Proteinogenic amino acids are amino acids that are precursors to proteins, and are incorporated into proteins cotranslationally — that is, during translation. There are 23 proteinogenic amino acids in prokaryotes (including N-Formylmethionine, mainly used to initiate protein synthesis and often removed afterward), but only 21 are encoded by the nuclear genes of eukaryotes.