TY - JOUR
T1 - Anisotropy decays of indole, melittin monomer and melittin tetramer by frequency-domain fluorometry and multi-wavelength global analysis
AU - Lakowicz, Joseph R.
AU - Gryczynski, Ignacy
AU - Cherek, Henryk
AU - Laczko, Gabor
N1 - Funding Information:
This work was supported by grants DMB-8804931, DMB-8502835 and DIR-8804831 from the National Science Foundation. J.R.L. and G.L. express appreciation for financial support from the Medical Biotechnology Center at the University of Maryland School Medicine.
PY - 1991/3
Y1 - 1991/3
N2 - We used frequency-domain fluorescence spectroscopy to measure the fluorescence lifetime and anisotropy decays of indole in propylene glycol, and of the tryptophan emission of melittin monomer and tetramer in water solutions at 5 °C. We obtained an increase in resolution of the anisotropy decays by using multiple excitation wavelengths, chosen to provide a range of fundamental anisotropy values. The multi-excitation wavelength anisotropy decays were analyzed globally to recover a single set of correlation times with wavelength-dependent anisotropy amplitudes. Simulated data and κ{script}R2 surfaces are shown to reveal the effect of multi-wavelength data on the resolution of complex anisotropy decays. For both indole and melittin, the anisotropy decays are heterogeneous and require two correlation times to fit the frequency-domain data. For indole in propylene glycol at 5°C we recovered correlation times of 0.59 and 4.10 ns, which appear to be characteristic of the rigid and asymmetric indole molecule. For melittin monomer the correlation times were 0.13 and 1.75 ns, and for melittin tetramer 0.12 and 3.96 ns. The shorter and longer correlation times of melittin are due to segmental motions and overall rotational diffusion of the polypeptide.
AB - We used frequency-domain fluorescence spectroscopy to measure the fluorescence lifetime and anisotropy decays of indole in propylene glycol, and of the tryptophan emission of melittin monomer and tetramer in water solutions at 5 °C. We obtained an increase in resolution of the anisotropy decays by using multiple excitation wavelengths, chosen to provide a range of fundamental anisotropy values. The multi-excitation wavelength anisotropy decays were analyzed globally to recover a single set of correlation times with wavelength-dependent anisotropy amplitudes. Simulated data and κ{script}R2 surfaces are shown to reveal the effect of multi-wavelength data on the resolution of complex anisotropy decays. For both indole and melittin, the anisotropy decays are heterogeneous and require two correlation times to fit the frequency-domain data. For indole in propylene glycol at 5°C we recovered correlation times of 0.59 and 4.10 ns, which appear to be characteristic of the rigid and asymmetric indole molecule. For melittin monomer the correlation times were 0.13 and 1.75 ns, and for melittin tetramer 0.12 and 3.96 ns. The shorter and longer correlation times of melittin are due to segmental motions and overall rotational diffusion of the polypeptide.
KW - Anisotropy decay
KW - Frequency-domain flourometry
KW - Indole
KW - Melittin
KW - Multi-wavelength global analysis
KW - Rotational diffusion
UR - http://www.scopus.com/inward/record.url?scp=0025976853&partnerID=8YFLogxK
U2 - 10.1016/0301-4622(91)80002-9
DO - 10.1016/0301-4622(91)80002-9
M3 - Article
C2 - 17014769
AN - SCOPUS:0025976853
VL - 39
SP - 241
EP - 251
JO - Biophysical Chemistry
JF - Biophysical Chemistry
SN - 0301-4622
IS - 3
ER -