title: Behaviour of tyrosyl residues of calf-thymus histone F3. Difference-spectroscopy studies.
abstract: We have studied the behaviour of microenvironments containing tyrosine of calf thymus histone F3 (or histone H3) by using the difference spectroscopy techniques of thermal and solvent perturbation. By comparison of the parameters found for the models L-tyrosine methyl ester and N-acetyl-L-tyrosine ethyl ester with those for the protein at various conditions, several aspects of the tertiary structure of histone F3 become apparent. The raising of ionic strength produces a general burial of tyrosyl residues of the histone, whereas low pH or urea treatment causes a complete exposure of tyrosyl groups with respect to the solvent. Anomalously high values can also be observed of accessibility of the perturbants sucrose and ethylene glycol at low concentrations of phosphate buffer. The relevance of these findings towards a better understanding of the tertiary structure of histone F3  and of its interactions with DNA is discussed.
mesh_terms: D000818:Animals; D002417:Cattle; D006657:Histones; D011487:Protein Conformation; D012997:Solvents; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D013950:Thymus Gland; D014443:Tyrosine / Q000032:analysis
chemical_list: D006657:Histones; D012997:Solvents; D014443:Tyrosine