Effects of Hydrogen Bonding and Temperature Upon the Near Ultraviolet Circular Dichroism and Absorption Spectra of Tyrosine and O-Methyl Tyrosine Derivatives

摘要: Abstract To gain information about the properties of tyrosyl residues buried within proteins, circular dichroism (CD) and absorption spectra tyrosine derivatives have been investigated in nonpolar solvents. N-Stearyl-l-tyrosine n-hexyl ester dissolved methylcyclohexane (O—O band at 283 nm) was used to measure effects hydrogen-bonding agents. Adding low concentrations dioxane, N,N-dimethylacetamide, 1-butanol, or methanol causes a 1- 4-nm red shift spectrum 10 25% increase dipole strength. The results with N,N-dimethylacetamide suggest that hydrogen bond between hydroxy group carbonyl oxygen peptide backbone may be one mechanism for producing large proteins. CD were recorded after N-stearyl-l-tyrosine had bonded. Dioxane cause intensify same extent as do spectra. Evidently bonding these compounds does not alter conformation this derivative. In contrast, butanol 50% loss rotatory strength, suggesting an altered conformation. dependence upon alcohol concentration is both alterations (halfmaximal effect 30 mm alcohol). Evidence presented polymeric form simultaneously amide atom ester. At greater than 15 µm, partially aggregated methylcyclohexane, causing changes aggregate proposed mainly dimer which each residue bonded other (K ≈ 1000 m-1). minimize aggregation, N-acetyl-O-methyl-l-tyrosine ethyl (N-Ac-O-Me-l-Tyr ester) N-stearyl-Omethyl-l-tyrosine studied. O-Methyl vibronic structure tyrosine, but wave length position much shifted by polar organic solvents 283.5 ± 0.5 nm). strengths O-methyl-l-tyrosine are nearly identical those l-tyrosine corresponding For N-Ac-O-Me-l-Tyr 297 K, strength especially (1.3 x 10-40 c.g.s. Δe = 0.75 m-1 cm-1 277 Upon cooling (dissolved ether-isopentane-ethanol solvent) from 140 negative rotational intensified 10-fold. These interpreted terms temperature shifting equilibrium distribution various conformers variable technique provide way detect motility side chains