Principles of Bioinorganic Chemistry - 2003
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Principles of Bioinorganic Chemistry - 2003
The grade for this course will be determined by a term exam (35%), a written research paper with oral presentation (45%), problem sets (12%) and classroom participation (8%). The oral presentations will be held in research conference style at MIT's Endicott House estate in Dedham, MA, on Saturday, October 18. Please reserve the date for there are no excused absences. Papers will be due
approximately one week earlier.WEB SITE: web.mit.edu/5.062/www/
Lecture Date Lecture Topic Reading Problems1 9/4 (Th) Intro; Choice, Uptake, Assembly of Mn+ Ions Ch. 5 Ch. 12 9/9 (Tu) Metalloregulation of Gene Expression Ch. 6 Ch. 23 9/11 (Th) Metallochaperones; Metal Folding, X-linking Ch. 7 Ch. 34 9/16 (Tu) Metals in Medicine; Cisplatin Ch. 8 Ch. 45 9/18 (Th) Electron Transfer; Fundamentals Ch. 9 Ch. 56 9/23 (Tu) Long-Distance Electron Transfer Ch. 9 Ch. 67 9/25 (Th) Hydrolytic Enzymes, Zinc, Ni, Co Ch. 10 Ch. 78 9/30 (MU) Model Complexes for Metallohydrolases Ch. 109 10/2 (MU) Dioxygen Carriers: Hb, Mb, Hc, Hr Ch. 1110 10/7 (Tu) O2 Activation, Hydroxylation: MMO, P-450, R2 Ch. 11 Ch. 811 10/9 (Th) Model Chemistry for O2 Carriers/Activators Ch. 11 Ch. 912 10/16 (Th) Complex Systems: cyt. oxidase; nitrogenase Ch. 12 Ch. 1013 10/21 (Tu) Metalloneurochemistry/Medicinal Inorg. Chem. Ch. 12 Ch. 1114 10/23 (Th) Term Examination Ch. 12 Ch. 12
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Principles of Bioinorganic Chemistry
Two Main Avenues of Study
•Understand the roles of naturally occurring inorganic elements in biology. By weight, > 50% of living matter is inorganic. Metal ions at the core of biomolecules control many key life processes.
•Use metals as probes and drugsExamples: Cisplatin, auranofin as pharmaceuticals Cardiolyte (99mTc) and Gd, imaging agents
MoS42-, Wilson’s disease; cancer??
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Respiration - Three O2 Carriers in Biology
oxyHb, MbdeoxyHb, Mb
deoxyHc oxyHc
oxyHrdeoxyHr
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The Heme Group; the Defining Example of a Bioinorganic Chip
Peripheral carboxylates and axial ligands matter!
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The Major Metal Units in ET Proteins
Iron-Sulfurclusters, electron transfer relay stations
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Structure of the Streptomyces lividans (KcsA) Potassium Channel(MacKinnon, et al., 1998)
Extracellular
Cytoplasm
Top view
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Cobalaminstructures
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Three Inorganic CompoundsUsed in Modern Medicine
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Course Organization
•What metals? How taken up? How assemble?•How do cells regulate metal ion concentrations? Homeostasis.•How do metal ions fold biopolymers?•How is the correct metal ion inserted into its site?•Electron transfer metalloproteins.•Substrate binding and activation, non-redox.•Atom and group transfer (main oxygen chemistry).•Protein tuning of active sites.
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Choice, Uptake and Assembly of Metal Ions in Cells
PRINCIPLES:•Relatively abundant metal ions used (geosphere/biosphere)•Labile metals used (nature works at a kilohertz)•Low abundance metals concentrated by ATP driven processes•Entry to the cell controlled by specific channels and pumps•Co-factors employed: bioinorganic chips (porphyrins)•Self-assembling units form - from geosphere•Metallochaperones assure that metal ions find their proteins
ILLUSTRATIONS:•The selectivity filter of the potassium channel•Uptake of iron
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Relative abundance of metal ions in the earth’s crust and seawater
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Iron Uptake in the Cell
•Iron is the second most abundant metal after aluminum•Its Fe(II) and Fe(III) redox states render it functionally useful•At pH 7, iron is insoluble (10-18 M)•The challenge: How to mobilize iron in the biosphere?
The Solutions:In bacteria, siderophoresIn humans, transferrin
The Challenge:
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Synthesis and Structure of Dinuclear Ferric Citrate Complexes
Fe(NO3)3.2H2O
Na3citrate
pyridine, H2O(Hpy)2[Fe2(cit)2(H2O)2]
.2H2O
Shweky et. al. Inorg. Chem. 1994, 33, 5161-5162.
“It will be interesting to determine whether solutions of 1 or 2 are taken up by living cells.”
Neocuproine hydrate[Fe3O(OAc)6(H2O)3](NO3)Citric acid, H2O
(Hneo)3[Fe2(Hcit)3].nH2O
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Ferric Citrate-Binding Site of Outer Membrane Transporter FecA
Ferguson et. al. Science, 2002, 295, 1715-1719.
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1.98 Å
2.01 Å
2.01 Å
1.96 Å2.00 Å
2.02 Å
2.05 Å
2.00 Å
2.00 Å
2.02 Å
Diiron Core of the Outer Membrane Transporter FecA
Fe Fe
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Enterobactin: a Bacterial Siderophore
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Enterobactin, a Cyclic Triserine Lactone
A specific cell membrane receptor exists for ferricenterobactin. Release in the cell can occur by hydrolysisof the lactone, reduction to Fe(II), and/or lowering the pH.
O
O
O
NHR
NHRRHN
O
O
O
Fe3+ + ent6- = [Fe(ent)]3-, Kf = 1049
At pH 7, Kd = 10-25 since the
6 catechol groups have to be
deprotonated. Only the Δ isomer
.is found in nature
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Structure of Vanadium(IV) Enterobactin
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Scheme showing the ATP-driven uptake of ferric enterobactin into E. coli cells through a specific
receptor in the cell membrane.
See Raymond, Dertz, and Kim, PNAS, 100, 3584.
outer membrane
cytoplasminmembrane
intracellular esterase; hydrolyzes Ent, releases iron
Does not distinguishΔ from