TY - JOUR
T1 - Conformational differences of oxytocin and vasopressin as observed by fluorescence anisotropy decays and transient effects in collisional quenching of tyrosine fluorescence
AU - Gryczynski, Ignacy
AU - Szmacinski, Henryk
AU - Laczko, Gabor
AU - Wiczk, Wieslaw
AU - Johnson, Michael L.
AU - Kusba, Jozef
AU - Lakowicz, Joseph R.
PY - 1991/9
Y1 - 1991/9
N2 - We used gigahertz frequency-domain fluorometry to examine the tyrosyl fluorescence intensity and anisotropy decays of the single-tyrosine cyclic peptide hormones oxytocin and vasopressin. Acrylamide quenching and a distance-dependent quenching model for collisional quenching were used to evaluate the extent of tyrosyl exposure to the quencher and to provide increased resolution of the picosecond anisotropy decays. Analysis of the intensity decays using a lifetime distribution model shows different distributions for oxytocin and vasopressin. We found that the tyrosyl fluorescence of lysine-vasopressin, as revealed both by the lifetime Stern-Volmer plots and from the quenching analysis, is quenched more effectively than oxytocin. For N-acetyltyrosinamide (NATyrA), oxytocin, and lysine-vasopressin, we recovered apparent diffusion coefficients for quenching of 4.7×10-6, 0.44×10-6, and 4.3×10-6 cm2/s, respectively, the lower value for oxytocin suggesting a shielded environment for its tyrosyl residue. Tyrosyl anisotropy decays were recovered by global analysis of progressively quenched samples. Compared with oxytocin, vasopressin displayed a longer correlation time for overall rotational diffusion and a higher amplitude for picosecond segmented motions of its tyrosyl residue. All the data are consistent with a more extended and flexible solution structure for vasopressin than for oxytocin.
AB - We used gigahertz frequency-domain fluorometry to examine the tyrosyl fluorescence intensity and anisotropy decays of the single-tyrosine cyclic peptide hormones oxytocin and vasopressin. Acrylamide quenching and a distance-dependent quenching model for collisional quenching were used to evaluate the extent of tyrosyl exposure to the quencher and to provide increased resolution of the picosecond anisotropy decays. Analysis of the intensity decays using a lifetime distribution model shows different distributions for oxytocin and vasopressin. We found that the tyrosyl fluorescence of lysine-vasopressin, as revealed both by the lifetime Stern-Volmer plots and from the quenching analysis, is quenched more effectively than oxytocin. For N-acetyltyrosinamide (NATyrA), oxytocin, and lysine-vasopressin, we recovered apparent diffusion coefficients for quenching of 4.7×10-6, 0.44×10-6, and 4.3×10-6 cm2/s, respectively, the lower value for oxytocin suggesting a shielded environment for its tyrosyl residue. Tyrosyl anisotropy decays were recovered by global analysis of progressively quenched samples. Compared with oxytocin, vasopressin displayed a longer correlation time for overall rotational diffusion and a higher amplitude for picosecond segmented motions of its tyrosyl residue. All the data are consistent with a more extended and flexible solution structure for vasopressin than for oxytocin.
KW - Oxytocin
KW - collisional quenching
KW - fluorescence anisotropy decays
KW - fluorescence intensity
KW - tyrosine fluorescence
KW - vasopressin
UR - http://www.scopus.com/inward/record.url?scp=0343167639&partnerID=8YFLogxK
U2 - 10.1007/BF00865363
DO - 10.1007/BF00865363
M3 - Article
C2 - 24242994
AN - SCOPUS:0343167639
SN - 1053-0509
VL - 1
SP - 163
EP - 176
JO - Journal of Fluorescence
JF - Journal of Fluorescence
IS - 3
ER -