scholarly journals Fusion of phospholipid vesicles produced by the anti-tumour protein α-sarcin

1990 ◽  
Vol 265 (3) ◽  
pp. 815-822 ◽  
Author(s):  
M Gasset ◽  
M Oñaderra ◽  
P G Thomas ◽  
J G Gavilanes
Keyword(s):  
Energy Transfer ◽  
Ionic Strength ◽  
Freeze Fracture ◽  
Molar Ratio ◽  
Phospholipid Vesicles ◽  
Fluorescence Energy Transfer ◽  
Molar Ratios ◽  
Binding Stoichiometry ◽  
Fracture Electron ◽  
Fluorescence Energy

The anti-tumour protein alpha-sarcin causes fusion of bilayers of phospholipid vesicles at neutral pH. This is demonstrated by measuring the decrease in the efficiency of the fluorescence energy transfer between N-(7-nitro-2-1,3-benzoxadiazol-4-yl)-dimyristoylphosphatidylethano lamine (NDB-PE) (donor) and N-(lissamine rhodamine B sulphonyl)-diacylphosphatidylethanolamine (Rh-PE) (acceptor) incorporated in dimyristoylphosphatidylcholine (DMPG) vesicles. The effect of alpha-sarcin is a maximum at 0.15 M ionic strength and is abolished at basic pH. alpha-Sarcin promotes fusion between 1,6-diphenylhexa-1,3,5-triene (DPH)-labelled DMPG and dipalmitoyl-PG (DPPG) vesicles, resulting in a single thermotropic transition for the population of fused phospholipid vesicles. Bilayers composed of DMPC and DMPG, at different molar ratios in the range 1:1 to 1:10 PC/PG, are also fused by alpha-sarcin. Freeze-fracture electron micrographs corroborate the occurrence of fusion induced by the protein. alpha-Sarcin also modifies the permeability of the bilayers, causing the leakage of calcein in dye-trapped PG vesicles. All of the observed effects reach saturation at a 50:1 phospholipid/protein molar ratio, which is coincident with the binding stoichiometry previously described.

scholarly journals Mechanism of interaction of Dictyostelium severin with actin filaments.

1982 ◽  
Vol 95 (3) ◽  
pp. 711-719 ◽  
Author(s):  
K Yamamoto ◽  
J D Pardee ◽  
J Reidler ◽  
L Stryer ◽  
J A Spudich
Keyword(s):  
Energy Transfer ◽  
Actin Filaments ◽  
Exchange Process ◽  
Molar Ratio ◽  
Fluorescence Energy Transfer ◽  
Dependent Manner ◽  
Emission Anisotropy ◽  
Subunit Exchange ◽  
Fluorescence Energy

Severin, a 40,000-dalton protein from Dictyostelium that disassembles actin filaments in a Ca2+ -dependent manner, was purified 500-fold to greater than 99% homogeneity by modifications of the procedure reported by Brown, Yamamoto, and Spudich (1982. J. Cell Biol. 93:205-210). Severin has a Stokes radius of 29 A and consists of a single polypeptide chain. It contains a single methionyl and five cysteinyl residues. We studied the action of severin on actin filaments by electron microscopy, viscometry, sedimentation, nanosecond emission anisotropy, and fluorescence energy transfer spectroscopy. Nanosecond emission anisotropy of fluoresence-labeled severin shows that this protein changes its conformation on binding Ca2+. Actin filaments are rapidly fragmented on addition of severin and Ca2+, but severin does not interact with actin filaments in the absence of Ca2+. Fluorescence energy transfer measurements indicate that fragmentation of actin filaments by severin leads to a partial depolymerization (t1/2 approximately equal to 30 s). Depolymerization is followed by exchange of a limited number of subunits in the filament fragments with the disassembled actin pool (t1/2 approximately equal to 5 min). Disassembly and exchange are probably restricted to the ends of the filament fragments since only a few subunits in each fragment participate in the disassembly or exchange process. Steady state hydrolysis of ATP by actin in the presence of Ca2+-severin is maximal at an actin: severin molar ratio of approximately 10:1, which further supports the inference that subunit exchange is limited to the ends of actin filaments. The observation of sequential depolymerization and subunit exchange following the fragmentation of actin by severin suggests that severin may regulate site-specific disassembly and turnover of actin filament arrays in vivo.

Red Laser-Induced Fluorescence Energy Transfer in an Immunosystem

2000 ◽  
Vol 280 (2) ◽  
pp. 272-277 ◽  
Author(s):  
Bernhard Oswald ◽  
Frank Lehmann ◽  
Lydia Simon ◽  
Ewald Terpetschnig ◽  
Otto S. Wolfbeis
Keyword(s):  
Energy Transfer ◽  
Laser Induced Fluorescence ◽  
Fluorescence Energy Transfer ◽  
Fluorescence Energy

scholarly journals Fluorescence energy transfer in quantum dot/azo dye complexes in polymer track membranes

2013 ◽  
Vol 8 (1) ◽  
pp. 452 ◽  
Author(s):  
Yulia A Gromova ◽  
Anna O Orlova ◽  
Vladimir G Maslov ◽  
Anatoly V Fedorov ◽  
Alexander V Baranov
Keyword(s):  
Energy Transfer ◽  
Quantum Dot ◽  
Azo Dye ◽  
Fluorescence Energy Transfer ◽  
Track Membranes ◽  
Fluorescence Energy
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