An infrared study of 2H-bond variation in myoglobin revealed by high pressure.

摘要: A high-pressure Fourier-transform infrared technique was used to probe the evolution of 'H bonds inside helical segments myoglobin in relation p2H, Tris concentration medium and iron-ligand nature. The analysis focused on changes conformation-sensitive amide-I' band, reflecting peptide C = 0 group stretching vibrations coupled in-plane N-2H bending C=N modes. From data obtained under high pressure, strength 2H bonds, a-helical protein at atmospheric is not simply a function p2H salt concentration. At low (50 mM), these increases with p'H, whereas for higher (100 mM) this lower 7 than p'H 6.0 or 8.5. It also observed that azidometmyoglobin molecule exhibits tighter intrahelical interactions sensitivity pressure aquametmyoglobin. Information presented regarding interhelical solvent. Hydrogen play key role stability [l] dynamics [2, 31. However, comparison current knowledge about hydrogen gases, liquids crystal lattices, little known proteins. problem assignment collective modes proteins [4], factors determining intra-helical structure weak strong [5] are difficult classify. Notable successes among few studies were performed using band [6 - 81. This hand represents 0-stretching vibration amide groups N-H N-stretching [9]. energy C=O primarily determined by particular adopted chains. In case molecule, comprises main helix near 1650 cm- ' minor bands 1627- 1638 cm-' 1671 1675 cmreflecting [4]. Since H basically dipoles, it interesting study whether monomeric such as myoglobin, an invariant parameter affected pH Investigating hydrogen-bond network solution importance, since most our derives from crystallized protein. has been recently shown, ultraviolet Ramdn-resonance studies, electrical field dependent [lo]. would imply ions surrounding solvent should consequently modulate globular Moreover, contains heme-iron binding site. Many ligands bind heme iron, inducing slight