principles of bioinorganic chemistry - 2004 the grade for this course will be determined by a term...
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Principles of Bioinorganic Chemistry - 2004
The grade for this course will be determined by a term exam (35%), a written research paper with oral presentation (55%), and problem sets (10%). The oral presentations will be held in research conference style at an all-day symposium at MIT on Saturday, October 30th. Please reserve the date for there are no excused absences. Papers are due October 28th.
WEB SITE: web.mit.edu/5.062/www/
Lecture Date Lecture Topic Reading Problems1 9/9 (Th) Intro; Choice, Uptake, Assembly of Mn+ IonsCh. 5 Ch. 12 9/14 (Tu) Metalloregulation of Gene Expression Ch. 6 Ch. 23 9/16 (Th) Metallochaperones; Metal Folding, X-linking.Ch. 7 Ch. 34 9/21 (Tu) Med. Inorg. Chem./MetalloneurochemistryCh. 8 Ch. 45 9/23 (Th) Mössbauer, EPR, IR Spectral FundamentalsCh. 9 Ch. 56 9/28 (Tu)Electron Transfer; Fundamentals Ch. 9 Ch. 67 9/30 (Th)Long-Distance Electron Transfer Ch. 10 Ch. 78 10/5 (Tu)Hydrolytic Enzymes, Zinc, Ni, Co Ch. 109 10/7 (Th)CO and Bioorganometallic Chemistry TBA Ch. 810 10/12 (Tu)Dioxygen Carriers: Hb, Mb, Hc, Hr Ch. 11 Ch. 911 10/14 (Th)O2 Activation, Hydroxylation: MMO, ToMOCh. 11 Ch. 1012 10/19 (Tu)Model Chemistry for O2 Carriers/ActivatorsCh. 12 Ch. 1113 10/21 (Th)Complex Systems: cyt. oxidase; nitrogenaseCh. 12 Ch. 1214 TBA Term Examination
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??
The Heme Group; the Defining Example of a Bioinorganic Chip
Peripheral carboxylates and axial ligands matter!
Structure of the Streptomyces lividans (KcsA) Potassium Channel(MacKinnon, et al., 1998)
Extracellular
Cytoplasm
Top view
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?•What physical methods are used and how do they work?•Electron transfer metalloproteins.•Substrate binding and activation, non-redox.•Bioorganometallic chemistry is now established.•Atom and group transfer (mainly oxygen chemistry).•Protein tuning of active sites.
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
Relative abundance of metal ions in the earth’s crust and seawater
Kinetics of H2O exchange:108 sec-1, labile10-3-10-6 sec-1, inert
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:
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
Ferric Citrate-Binding Site of Outer Membrane Transporter FecA
Ferguson et. al. Science, 2002, 295, 1715-1719.
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
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