ISSN:
1432-1017
Keywords:
Fluorescence
;
Energy transfor
;
Oxytocin
;
Vasopressin
;
Distance distribution
;
Time-resolved fluorescence
;
Frequency-domain fluorescence
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Physics
Notes:
Abstract We have examined the fluorescence intensity decays of oxytocin and [Arg8]-vasopressin resulting from the single tyrosyl residue in each peptide, and the intensity decay of the Asu 1,6-analogues in which the disulfide bridge is substituted by a CH2-CH2 bridge. Viscosity-dependent steady state and intensity decay measurements indicated that fluorescence resonance energy transfer (FRET) from tyrosyl phenol to the disulfide bridge is responsible for the decrease in fluorescence relative to the Asu-analogues. The frequency-domain phase and modulation data for the tyrosyl donor were interpreted in terms of fluorescence resonance energy transfer (FRET) to the weakly absorbing disulfide bridge and a distribution of donor-to-acceptor distances. Energy transfer efficiencies were determined from both time-resolved and steady-state measurements. Fitting the frequency-domain phase and modulation data to a Gaussian distance distribution indicated that the average inter-chromophoric distance (Rav) is similar in both compounds, Rav=7.94 Å for oxytocin and Rav = 8.00 Å for vasopressin. However, the width of the distance distribution is narrower for vasopression (hw =2.80 Å) than for oxytocin (hw =3.58 Å), which is consistent with restriction of the tyrosine phenol motion due to its stacking with the Phe3 side chain of vasopressin. Finally, the recovered distance distribution functions are compared with histograms describing the distance between the chromophores during the course of long, in vacuo, molecular dynamics runs using the computer program CHARMm and the QUANTA 3.0 parameters.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00180276
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