Biomaterial Database

Conformational substates and dynamic properties of carbonmonoxy hemoglobin. 2003

Antonio Cupane, and Maurizio Leone, and Valeria Militello

Istituto Nazionale per la Fisica della Materia and Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo, Via Archirafi, 36, 90123 Palermo, Italy. cupane@fisicia.unipa.it

Heme pocket dynamics of human carbonmonoxy hemoglobin (HbCO) is studied by Fourier transform infrared spectroscopy. The CO stretching band at various temperatures in the interval 300-10 K is analyzed in terms of three taxonomic A substates; however, in HbCO the band attributed to the A(1) taxonomic substate accounts for approximately 90% of the total intensity in the pH range 8.8-4.5. Two different regimes as a function of temperature are observed: below 160 K, the peak frequency and the bandwidth of the A(1) band have constant values whereas, above this temperature, a linear temperature dependence is observed, suggesting the occurrence of transitions between statistical substates within the A(1) taxonomic substate in this protein. The relationship between the heme pocket dynamics (as monitored by the thermal behavior of the CO stretching band), the overall dynamic properties of the protein matrix (as monitored by the thermal behavior of Amide II and Amide I' bands) and the glass transition of the solvent (as monitored by the thermal behavior of the bending band of water) is also investigated. From this analysis, we derive the picture of a very soft heme pocket of hemoglobin characterized by rather large anharmonic terms and strongly coupled to the dynamic properties of the solvent.

UI	MeSH Term	Description	Entries
D008024	Ligands	A molecule that binds to another molecule, used especially to refer to a small molecule that binds specifically to a larger molecule, e.g., an antigen binding to an antibody, a hormone or neurotransmitter binding to a receptor, or a substrate or allosteric effector binding to an enzyme. Ligands are also molecules that donate or accept a pair of electrons to form a coordinate covalent bond with the central metal atom of a coordination complex. (From Dorland, 27th ed)	Ligand
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D002263	Carboxyhemoglobin		Carbomonoxyhemoglobin,Carbonmonoxyhemoglobin,Carbonylhemoglobin,Carboxyhemoglobin A,Carboxyhemoglobin C
D006418	Heme	The color-furnishing portion of hemoglobin. It is found free in tissues and as the prosthetic group in many hemeproteins.	Ferroprotoporphyrin,Protoheme,Haem,Heme b,Protoheme IX
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D000577	Amides	Organic compounds containing the -CO-NH2 radical. Amides are derived from acids by replacement of -OH by -NH2 or from ammonia by the replacement of H by an acyl group. (From Grant & Hackh's Chemical Dictionary, 5th ed)	Amide
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
D013696	Temperature	The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.	Temperatures
D017550	Spectroscopy, Fourier Transform Infrared	A spectroscopic technique in which a range of wavelengths is presented simultaneously with an interferometer and the spectrum is mathematically derived from the pattern thus obtained.	FTIR,Fourier Transform Infrared Spectroscopy,Spectroscopy, Infrared, Fourier Transform