Biomaterial Database

Bilirubin. Solubility and interaction with albumin and phospholipid. 1979

R Brodersen

Bilirubin is generally considered a lipophilic substance, and its neurotoxicity is ascribed to an affinity for lipids in the central nervous system. In the present paper, it is shown that the solubility of bilirubin in apolar solvents and in triglycerides is low and increases with solvent polarity. Consequently, bilirubin should not be characterized as lipophilic. The solubility in aqueous buffers was studied under exclusion of light and was found lower than previously reported, about 7 nM at pH 7.4, temperature 37 degrees C, increasing with higher pH, approximately in inverse proportion with the squared hydrogen ion concentration. Binding of bilirubin to human serum albumin was studied by the rate of oxidation with peroxidase of the free ligand at equilibrium. The stoichiometry of proton involvement in the binding process was investigated by acidimetric titration. It is concluded that precipitation of bilirubin in vivo is thermodynamically possible. It was further demonstrated by light absorption spectroscopy that bilirubin forms a complex with phosphatidylcholine in diethyl ether and that an aqueous suspension of phosphatidylcholine enhanced aggregation of bilirubin. Transfer of bilirubin dianion from its complex with plasma albumin and precipitation of bilirubin acid with phosphatidylcholine in membranes of nerve cells is therefore possible and may account for the neurotoxicity.

UI	MeSH Term	Description	Entries
D010743	Phospholipids	Lipids containing one or more phosphate groups, particularly those derived from either glycerol (phosphoglycerides see GLYCEROPHOSPHOLIPIDS) or sphingosine (SPHINGOLIPIDS). They are polar lipids that are of great importance for the structure and function of cell membranes and are the most abundant of membrane lipids, although not stored in large amounts in the system.	Phosphatides,Phospholipid
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
D002621	Chemistry	A basic science concerned with the composition, structure, and properties of matter; and the reactions that occur between substances and the associated energy exchange.
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001663	Bilirubin	A bile pigment that is a degradation product of HEME.	Bilirubin IX alpha,Bilirubin, (15E)-Isomer,Bilirubin, (4E)-Isomer,Bilirubin, (4E,15E)-Isomer,Bilirubin, Calcium Salt,Bilirubin, Disodium Salt,Bilirubin, Monosodium Salt,Calcium Bilirubinate,Hematoidin,delta-Bilirubin,Bilirubinate, Calcium,Calcium Salt Bilirubin,Disodium Salt Bilirubin,Monosodium Salt Bilirubin,Salt Bilirubin, Calcium,delta Bilirubin
D012709	Serum Albumin	A major protein in the BLOOD. It is important in maintaining the colloidal osmotic pressure and transporting large organic molecules.	Plasma Albumin,Albumin, Serum
D012995	Solubility	The ability of a substance to be dissolved, i.e. to form a solution with another substance. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Solubilities
D012997	Solvents	Liquids that dissolve other substances (solutes), generally solids, without any change in chemical composition, as, water containing sugar. (Grant & Hackh's Chemical Dictionary, 5th ed)	Solvent
D013053	Spectrophotometry	The art or process of comparing photometrically the relative intensities of the light in different parts of the spectrum.
D055598	Chemical Phenomena	The composition, structure, conformation, and properties of atoms and molecules, and their reaction and interaction processes.	Chemical Concepts,Chemical Processes,Physical Chemistry Concepts,Physical Chemistry Processes,Physicochemical Concepts,Physicochemical Phenomena,Physicochemical Processes,Chemical Phenomenon,Chemical Process,Physical Chemistry Phenomena,Physical Chemistry Process,Physicochemical Phenomenon,Physicochemical Process,Chemical Concept,Chemistry Process, Physical,Chemistry Processes, Physical,Concept, Chemical,Concept, Physical Chemistry,Concept, Physicochemical,Concepts, Chemical,Concepts, Physical Chemistry,Concepts, Physicochemical,Phenomena, Chemical,Phenomena, Physical Chemistry,Phenomena, Physicochemical,Phenomenon, Chemical,Phenomenon, Physicochemical,Physical Chemistry Concept,Physicochemical Concept,Process, Chemical,Process, Physical Chemistry,Process, Physicochemical,Processes, Chemical,Processes, Physical Chemistry,Processes, Physicochemical