Fluorescence Studies of Metal-Humic Complexes with the Use of Lanthanide Ion Probe Spectroscopy

1996 ◽  
Vol 50 (3) ◽  
pp. 401-408 ◽  
Author(s):  
J. W. Thomason ◽  
W. Susetyo ◽  
L. A. Carreira
Keyword(s):  
Fluorescence Lifetime ◽  
Metal Binding ◽  
Binding Sites ◽  
Peak Shift ◽  
Binding Energies ◽  
Lanthanide Ion ◽  
Fluorescence Studies ◽  
Ion Probe ◽  
Humic Materials ◽  
Probe Spectroscopy

The acidic functional groups of humic materials are an abundant source of metal binding sites in the natural environment. Studies of metal binding to humics are of great environmental interest because the biological and physicochemical properties of metals are often changed dramatically as a result of complexation with humics. In order to understand how these heterogeneous organic macromolecules bind metals with such a large range of binding energies, lanthanide ion probe spectroscopy (LIPS) has been used to study changes in the fluorescence lifetime of the europium probe metal as it binds to these substances. A method developed by Horrocks and Sudnick for the determination of the number of water molecules bound to Eu3+ was used to calculate the coordination number of humic-bound Eu3+ from the fluorescence data. The peak shift of the Eu3+ hypersensitive emission band (616 nm) was used to calculate the change in charge of the complex. Equations based on Horrocks and Sudnick's method were also developed to calculate the distribution of metal associated with the different types of binding sites on humic substances by computer modeling of the fluorescence lifetime data.

Characterization of metal binding sites in fulvic acids by lanthanide ion probe spectroscopy

1989 ◽  
Vol 61 (5) ◽  
pp. 483-488 ◽  
Author(s):  
J. C. Dobbs ◽  
W. Susetyo ◽  
F. E. Knight ◽  
M. A. Castles ◽  
Lionel A. Carreira ◽  
...  
Keyword(s):  
Metal Binding ◽  
Binding Sites ◽  
Fulvic Acids ◽  
Lanthanide Ion ◽  
Metal Binding Sites ◽  
Ion Probe ◽  
Probe Spectroscopy

scholarly journals Serological and fluorescence studies of the heat stability of bovine lactoferrin

1979 ◽  
Vol 46 (1) ◽  
pp. 83-93 ◽  
Author(s):  
Augustin Baer ◽  
Marko Oroz ◽  
Bernard Blanc
Keyword(s):  
Metal Binding ◽  
Binding Sites ◽  
Complement Fixation ◽  
Heat Stability ◽  
Heat Denaturation ◽  
Bovine Lactoferrin ◽  
Iron Binding ◽  
Binding Ability ◽  
Fluorescence Studies ◽  
Tryptophan Residues

SUMMARYThe heat denaturation of Fe-saturated lactoferrin (If) and Fe-free lactoferrin (apo-lf) was studied using the methods of micro-complement fixation and fluorescence. It was established that the change in conformation of apo-lf, induced by iron binding, conferred a higher heat stability to the molecule: the changes were observed at temperatures above 40 °C for apo-lf and above 60 °C for If. The Fe-binding ability of the protein was partially independent of the degree of denaturation. Fluorescence analyses indicated that tryptophan residues were probably not directly involved in the metal binding. There was no evidence of antibodies interfering with the binding sites.

Lanthanide Ion Probe Spectroscopy for Metal Ion Speciation

2020 ◽  
pp. 103-138
Author(s):  
Wisnu Susetyo ◽  
Lionel A. Carreira ◽  
Leo V. Azarraga ◽  
David M. Grimm
Keyword(s):  
Metal Ion ◽  
Lanthanide Ion ◽  
Ion Probe ◽  
Probe Spectroscopy ◽  
Metal Ion Speciation

Competitive binding of protons and metal ions in humic substances by lanthanide ion probe spectroscopy

1989 ◽  
Vol 61 (14) ◽  
pp. 1519-1524 ◽  
Author(s):  
J. C. Dobbs ◽  
W. Susetyo ◽  
L. A. Carreira ◽  
L. V. Azarraga
Keyword(s):  
Metal Ions ◽  
Humic Substances ◽  
Competitive Binding ◽  
Lanthanide Ion ◽  
Ion Probe ◽  
Probe Spectroscopy

A Novel Approach to Metal-Humic Complexation Studies by Lanthanide Ion Probe Spectroscopy

1989 ◽  
Vol 37 (1) ◽  
pp. 1-17 ◽  
Author(s):  
J. C. Dobbs ◽  
W. Susetyo ◽  
F. E. Knight ◽  
M. A. Castles ◽  
L. A. Carreira ◽  
...  
Keyword(s):  
Lanthanide Ion ◽  
Complexation Studies ◽  
Novel Approach ◽  
Ion Probe ◽  
Probe Spectroscopy

scholarly journals Interactions of the lanthanide- and hapten-binding sites in the Fv fragment from the myeloma protein MOPC 315

1976 ◽  
Vol 155 (1) ◽  
pp. 37-53 ◽  
Author(s):  
R A Dwek ◽  
D Givol ◽  
R Jones ◽  
A C McLaughlin ◽  
S Wain-Hobson ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Metal Binding ◽  
Spin Label ◽  
Binding Sites ◽  
Binding Constants ◽  
Kinetic Scheme ◽  
Difference Spectrum ◽  
Protein Fluorescence ◽  
Myeloma Protein ◽  
Fluorescence Studies

1. The interactions of lanthanide metals and dinitrophenyl spin-label haptens with the Fv fragment of the mouse myeloma protein MOPC 315 were investigated by the techniques of fluorescence, e.s.r. (electron spin resonance) and high-resolution n.m.r. (nuclear magnetic resonance). 2. The protein fluorescence of Fv fragment at 340nm is quenched by the haptens (fluorescence enhancement, epsilon=0.15) and enhanced by Gd(III) (epsilon=1.14) and other lanthanides. The binding of the haptens studied here is insensitive to pH in the range 5.5-7.0 (dissociation constant KH=0.3-1.0 muM) and shows 1:1 stoicheiometry. The binding of Gd(III) also shows 1:1 stoicheiometry, but is pH-dependent; the binding constant (KM) varies from 10 muM at pH7.0 to 700 muM at pH4.8. La(III) binding is less sensitive to pH. The pH-dependences of the metal-binding constants imply that a group in the protein with pKa greater than or equal to 6.2 is involved in the binding, and probably also other groups with lower pKa values. 3. The apparent binding of the haptens is weakened about 20-fold by Gd(III), and vice versa. An equilibrium scheme involving a ternary complex with an interaction between the two binding sites is derived in Appendix I to explain the experimental results at two pH values. 4. Time-dependent fluorescence changes are observed in the presence of Gd(III) at pH5.5. A two-state kinetic scheme involving a ‘slow’ conformational change in the Fv fragment is derived in Appendix II to explain this time-dependence. This scheme is consistent with the antagonistic equilibrium behaviour. 5. The e.s.r. changes in the spin-label haptens on binding to Fv fragment and on the subsequent addition of lanthanides are consistent with the binding scheme for haptens and lanthanides proposed from the fluorescence studies. A difference between the limiting quenching of the e.s.r. signal from the bound haptens in the presence of saturating concentrations of Gd(III) and La(III) is attributed to dipolar interactions between bound Gd(III) and the nitroxide moiety of the bound hapten. The residual quenching with Gd(III) allows an estimate of 1.2nm to be made for the distance between the two paramagnetic centres. 6. The 270 MHz proton difference spectrum of the Fv fragment resulting from the addition of La(III) suggests that any metal-induced conformational changes are small and involve relatively few amino acid residues on the Fv fragment.

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