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Author  |
Abbruzzetti, S.; Viappiani, C.; Small, J.R.; Libertini, L.J.; Small, E.W. |
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Title |
Kinetics of histidine deligation from the heme in GuHCl-unfolded Fe(III) cytochrome C studied by a laser-induced pH-jump technique |
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Journal Article |
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Year |
2001 |
Publication |
Journal of the American Chemical Society |
Abbreviated Journal |
J Am Chem Soc |
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Volume |
123 |
Issue |
27 |
Pages |
6649-6653 |
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Keywords |
Animals; *Bacterial Proteins; Cytochrome c Group/*chemistry; Guanidine/*chemistry; Heme/*chemistry; Histidine/*chemistry; Horses; Hydrogen-Ion Concentration; Kinetics; *Lasers; Ligands; Protein Folding |
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Abstract |
We have developed an instrumental setup that uses transient absorption to monitor protein folding/unfolding processes following a laser-induced, ultrafast release of protons from o-nitrobenzaldehyde. The resulting increase in [H(+)], which can be more than 100 microM, is complete within a few nanoseconds. The increase in [H(+)] lowers the pH of the solution from neutrality to approximately 4 at the highest laser pulse energy used. Protein structural rearrangements can be followed by transient absorption, with kinetic monitoring over a broad time range (approximately 10 ns to 500 ms). Using this pH-jump/transient absorption technique, we have examined the dissociation kinetics of non-native axial heme ligands (either histidine His26 or His33) in GuHCl-unfolded Fe(III) cytochrome c (cyt c). Deligation of the non-native ligands following the acidic pH-jump occurs as a biexponential process with different pre-exponential factors. The pre-exponential factors markedly depend on the extent of the pH-jump, as expected from differences in the pK(a) values of His26 and His33. The two lifetimes were found to depend on temperature but were not functions of either the magnitude of the pH-jump or the pre-pulse pH of the solution. The activation energies of the deligation processes support the suggestion that GuHCl-unfolded cyt c structures with non-native histidine axial ligands represent kinetic traps in unfolding. |
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Address |
Dipartimento di Fisica, Universita di Parma, Istituto Nazionale per la Fisica della Materia, 43100 Parma, Italy |
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0002-7863 |
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Notes |
PMID:11439052 |
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Call Number |
Equine Behaviour @ team @ |
Serial |
3788 |
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Author |
Reynhout, I.C.; Cornelissen, J.J.L.M.; Nolte, R.J.M. |
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Title |
Self-assembled architectures from biohybrid triblock copolymers |
Type |
Journal Article |
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Year |
2007 |
Publication |
Journal of the American Chemical Society |
Abbreviated Journal |
J Am Chem Soc |
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Volume |
129 |
Issue |
8 |
Pages |
2327-2332 |
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Keywords |
Horseradish Peroxidase/*chemistry; Micelles; Molecular Structure; Myoglobin/*chemistry; Particle Size; Polyethylene Glycols/*chemistry; Polymers/*chemical synthesis/chemistry; Polystyrenes/*chemistry; Surface-Active Agents/chemical synthesis/chemistry |
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Abstract |
The synthesis and self-assembly behavior of biohybrid ABC triblock copolymers consisting of a synthetic diblock, polystyrene-b-polyethylene glycol (PSm-b-PEG113), where m is varied, and a hemeprotein, myoglobin (Mb) or horse radish peroxidase (HRP), is described. The synthetic diblock copolymer is first functionalized with the heme cofactor and subsequently reconstituted with the apoprotein or the apoenzyme to yield the protein-containing ABC triblock copolymer. The obtained amphiphilic block copolymers self-assemble in aqueous solution into a large variety of aggregate structures. Depending on the protein and the polystyrene block length, micellar rods, vesicles, toroids, figure eight structures, octopus structures, and spheres with a lamellar surface are formed. |
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Institute for Molecules and Materials, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands |
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0002-7863 |
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PMID:17274615 |
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1832 |
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