8. Lead(II) Complexes of Amino Acids, Peptides, and Other Related Ligands of Biological Interest
-
Etelka Farkas
Abstract
Lead(II) forms (NH2,COO-)-chelated mono- and bis-complexes with simple amino acids, while mono-complexes with pH-dependent coordination modes exist with simple dipeptides. These mostly hemidirected complexes have moderate stability. While a weak interaction of side chain imidazole and carboxylate in lead(II)-aminoacidato complexes is found, the thiolate group has an exceptionally high affinity to this metal ion. For example, tridentate (NH2,COO-,S-)-coordination of penicillamine (Pen) and cysteine (Cys) results in an extremely strong interaction with lead(II), but, owing to the sterical effect of the 6s2 pair, a second ligand is not able to coordinate in the above mentioned tridentate way. Although there is no example for a lead(II)-induced deprotonation and coordination of a peptide-amide and the side-chain thiolate in oligopeptides has a somewhat lower basicity compared to that of Pen or Cys, still the Cys-containing peptides interact rather strongly with lead(II). Interestingly, the position of Cys in the peptide influences significantly both the lead-binding ability via different bonding modes and the selectivity for lead(II) against other metal ions, like zinc(II) or cadmium(II). At high ligand excess, however, coordination of three sulfur donors to lead(II) is found with thiolate-containing amino acids and oligopeptides.
High basicity oxygens of hydroxamates, hydroxypyronates, and hydroxypyridinonates are also effective lead-binding donors. Some factors affecting the complexation of these ligands with lead(II) are: (i) A larger extent of delocalization along the ring in hydroxypyridinonate results in a more favored metal-binding ability over hydroxypyronate. (ii) Even monohydroxamates are good ligands and form mono- and bis-complexes with lead(II). (iii) In general, dihydroxamates and trihydroxamate-based siderophores, like desferrioxamine B (DFB) and desferricoprogen (DFC), are better binding agents for Pb(II) than the monohydroxamates, but the length and structure of linkers connecting the hydroxamate moieties have a significant impact on the complexation and selectivity for lead(II). (iv) The corresponding thio derivatives are significantly better ligands for lead than their parent oxo molecules, but polymeric complexes with poor water solubility are formed in most cases. (v) Out of the hydroxamate derivatives of amino acids the α-ones are the most effective ligands, provided polynuclear species involving the hydroxamate-oxygens, amino-N and hydroxamate-N can be formed.
Abstract
Lead(II) forms (NH2,COO-)-chelated mono- and bis-complexes with simple amino acids, while mono-complexes with pH-dependent coordination modes exist with simple dipeptides. These mostly hemidirected complexes have moderate stability. While a weak interaction of side chain imidazole and carboxylate in lead(II)-aminoacidato complexes is found, the thiolate group has an exceptionally high affinity to this metal ion. For example, tridentate (NH2,COO-,S-)-coordination of penicillamine (Pen) and cysteine (Cys) results in an extremely strong interaction with lead(II), but, owing to the sterical effect of the 6s2 pair, a second ligand is not able to coordinate in the above mentioned tridentate way. Although there is no example for a lead(II)-induced deprotonation and coordination of a peptide-amide and the side-chain thiolate in oligopeptides has a somewhat lower basicity compared to that of Pen or Cys, still the Cys-containing peptides interact rather strongly with lead(II). Interestingly, the position of Cys in the peptide influences significantly both the lead-binding ability via different bonding modes and the selectivity for lead(II) against other metal ions, like zinc(II) or cadmium(II). At high ligand excess, however, coordination of three sulfur donors to lead(II) is found with thiolate-containing amino acids and oligopeptides.
High basicity oxygens of hydroxamates, hydroxypyronates, and hydroxypyridinonates are also effective lead-binding donors. Some factors affecting the complexation of these ligands with lead(II) are: (i) A larger extent of delocalization along the ring in hydroxypyridinonate results in a more favored metal-binding ability over hydroxypyronate. (ii) Even monohydroxamates are good ligands and form mono- and bis-complexes with lead(II). (iii) In general, dihydroxamates and trihydroxamate-based siderophores, like desferrioxamine B (DFB) and desferricoprogen (DFC), are better binding agents for Pb(II) than the monohydroxamates, but the length and structure of linkers connecting the hydroxamate moieties have a significant impact on the complexation and selectivity for lead(II). (iv) The corresponding thio derivatives are significantly better ligands for lead than their parent oxo molecules, but polymeric complexes with poor water solubility are formed in most cases. (v) Out of the hydroxamate derivatives of amino acids the α-ones are the most effective ligands, provided polynuclear species involving the hydroxamate-oxygens, amino-N and hydroxamate-N can be formed.
Chapters in this book
- Frontmatter i
- About the Editors v
- Historical Development and Perspectives of the Series Metal Ions in Life Sciences vii
- Preface to Volume 17 ix
- Contents xiii
- Contributors to Volume 17 xix
- Titles of Volumes 1–44 in the Metal Ions in Biological Systems Series xxiii
- Contents of Volumes in the Metal Ions in Life Sciences Series xxv
- 1. The Bioinorganic Chemistry of Lead in the Context of Its Toxicity 1
- 2. Biogeochemistry of Lead. Its Release to the Environment and Chemical Speciation 21
- 3. Analytical Methods for the Determination of Lead in the Environment 49
- 4. Smart Capsules for Lead Removal from Industrial Wastewater 61
- 5. Lead Speciation in Microorganisms 79
- 6. Human Biomonitoring of Lead Exposure 99
- 7. Solid State Structures of Lead Complexes with Relevance for Biological Systems 123
- 8. Lead(II) Complexes of Amino Acids, Peptides, and Other Related Ligands of Biological Interest 201
- 9. Lead(II) Binding in Metallothioneins 241
- 10. Lead(II) Binding in Natural and Artificial Proteins 271
- 11. Complex Formation of Lead(II) with Nucleotides and Their Constituents 319
- 12. The Role of Lead(II) in Nucleic Acids 403
- 13. Historical View on Lead: Guidelines and Regulations 435
- 14. Environmental Impact of Alkyl Lead(IV) Derivatives: Perspective after Their Phase-out 471
- 15. Lead Toxicity in Plants 491
- 16. Toxicology of Lead and Its Damage to Mammalian Organs 501
- Subject Index 535
Chapters in this book
- Frontmatter i
- About the Editors v
- Historical Development and Perspectives of the Series Metal Ions in Life Sciences vii
- Preface to Volume 17 ix
- Contents xiii
- Contributors to Volume 17 xix
- Titles of Volumes 1–44 in the Metal Ions in Biological Systems Series xxiii
- Contents of Volumes in the Metal Ions in Life Sciences Series xxv
- 1. The Bioinorganic Chemistry of Lead in the Context of Its Toxicity 1
- 2. Biogeochemistry of Lead. Its Release to the Environment and Chemical Speciation 21
- 3. Analytical Methods for the Determination of Lead in the Environment 49
- 4. Smart Capsules for Lead Removal from Industrial Wastewater 61
- 5. Lead Speciation in Microorganisms 79
- 6. Human Biomonitoring of Lead Exposure 99
- 7. Solid State Structures of Lead Complexes with Relevance for Biological Systems 123
- 8. Lead(II) Complexes of Amino Acids, Peptides, and Other Related Ligands of Biological Interest 201
- 9. Lead(II) Binding in Metallothioneins 241
- 10. Lead(II) Binding in Natural and Artificial Proteins 271
- 11. Complex Formation of Lead(II) with Nucleotides and Their Constituents 319
- 12. The Role of Lead(II) in Nucleic Acids 403
- 13. Historical View on Lead: Guidelines and Regulations 435
- 14. Environmental Impact of Alkyl Lead(IV) Derivatives: Perspective after Their Phase-out 471
- 15. Lead Toxicity in Plants 491
- 16. Toxicology of Lead and Its Damage to Mammalian Organs 501
- Subject Index 535
