Alterations in the ultraviolet absorption spectra of steroids upon binding to serum proteins.
Difference spectra of progesterone-binding globulin (PBG) complexes with progesterone and testosterone were measured. The contributions of steroid and protein to the difference spectra were resolved by use of 5alpha-pregane-3,20-dione and dihydrotestosterone to compensate for the perturbation of PBG. The absorption spectra of seven bound steroids all showed increased extinction coefficients, sharpened absorption bands, a small blue shift, and an increased area implying an enhanced transition moment. This is in contrast to the steroid complexes with the low affinity binders, human serum albumin, and alpha 1-acid glycoprotein, which exhibit decreased extinction coefficients and reduced transition moments.
D000510:Alpha-Globulins; D000818:Animals; D013196:Dihydrotestosterone; D005260:Female; D006168:Guinea Pigs; D008524:Medrogestone; D008968:Molecular Conformation; D009961:Orosomucoid; D011247:Pregnancy; D011277:Pregnanediones; D011374:Progesterone; D011376:Progesterone-Binding Globulin; D012709:Serum Albumin; D013056:Spectrophotometry, Ultraviolet; D013256:Steroids; D013739:Testosterone
D000510:Alpha-Globulins; D009961:Orosomucoid; D011277:Pregnanediones; D011376:Progesterone-Binding Globulin; D012709:Serum Albumin; D013256:Steroids; D008524:Medrogestone; D013196:Dihydrotestosterone; D013739:Testosterone; D011374:Progesterone