Date post: | 04-Jun-2018 |
Category: |
Documents |
Upload: | rahul-muttineni |
View: | 215 times |
Download: | 0 times |
of 37
8/14/2019 Bio Inorganic
1/37
D:
B C
/
/ &
/ /
8/14/2019 Bio Inorganic
2/37
8/14/2019 Bio Inorganic
3/37
Classification of Chemical Elements
1. Bulk Elements : H/H+, C, N, O2-/O2 /O2
-2, P, S/S-2
2. Macrominerals and Ions : Na/Na+, K/K+, Mg/Mg+, Ca/Ca+2,
Cl-, PO4-3, SO4
-2
. race ements : e e+ e+ e+ , n n+ ,
Cu/Cu+/Cu+2/Cu+3
4. Ultra Trace Elements
a. Nonmetal : F/F , I/I , Se/Se-2, Si/Si+4, As, B
b. Metals : Mn/Mn+2/Mn+3/Mn+4/Mn+5, Mo/Mo+4/Mo+5/
Mo+6, Co/Co+2/Co+3, Cr/Cr+3/Cr+6, V/V+3/V+4/V+5,
Ni+/Ni+2/Ni+3, Cd/Cd+2, Sn/Sn+2/Sn+4, Pb/Pb+2, Li/Li+
8/14/2019 Bio Inorganic
4/37
Percentage Composition of Selected Elements in Human Body
8/14/2019 Bio Inorganic
5/37
Role of Metal Ions in Biological Systems
Group I &II metals operate as structural elements or in maintenance of charge and osmotic balance
Metal ions that exist in single oxidation state functions as structural elements or as triggers. For ex.SOD, zinc fingers (Zn), Calmodulin or Troponin C (Ca+2)
8/14/2019 Bio Inorganic
6/37
Metal ions in multiple oxidation states serve as electron carriers. Ex. Cytochromes, Fe-S
clusters (Fe), Cytochrome C oxidase, azurin, plastocynin (Cu)
8/14/2019 Bio Inorganic
7/37
Metal ions in multiple oxidation states also play role in dioxygen transportation. Ex.
Hemoglobin (Fe), hemocynin (Cu)
8/14/2019 Bio Inorganic
8/37
Variable oxidation states of metals play vital role in enzymatic catalytic reactions.
8/14/2019 Bio Inorganic
9/37
Ligand preference and possible coordination geometries of the metal center are important
bioinorganic principles. Metal ligand preference is closely related to the hard soft acid
base nature of metals and their preferred ligands.
Hard cations can be
thought of as small dense
Hard ligands are usually
the small highly
electronegative elements
or ligand atoms within a
hard polyatomic ion (exoxygen)
8/14/2019 Bio Inorganic
10/37
B
There are 20 naturally occurring amino acids
In humans, 10 of these amino acids are essential
Every amino acid contains a central carbon, called alpha,
group NH2 (b) carboxylic group, -COOH (c) Hydrogenatom and (d) side chain (-R) group which is unique to each
amino acid. This R group defines the nature (polar, acidic,
basic) characteristics of the amino acid.
8/14/2019 Bio Inorganic
11/37
Non polar hydrophobic amino acids
8/14/2019 Bio Inorganic
12/37
polar neutral amino acids
8/14/2019 Bio Inorganic
13/37
polar acidic amino acids
8/14/2019 Bio Inorganic
14/37
polar basic amino acids
8/14/2019 Bio Inorganic
15/37
8/14/2019 Bio Inorganic
16/37
Iron Containing Enzymes
Those containing aporphyrin ligand system
An iron - bearing heme
moiet
Those not containingporphyrin ligands
non - heme iron -
containin roteins
Iron Sulphur Clusters
8/14/2019 Bio Inorganic
17/37
Four basic core structures which have been characterized:
Rubedoxins found only in bacteria, in which the [FeS] cluster consists of a single Fe atom
bound to four Cys residuesthe iron atom can be in the +2 or +3 valency
Rhombic two-irontwo-sulfide [Fe2S2] clusterstypical stable cluster oxidation states are
+1 and +2 (the charges of the coordinating cysteinate residues are not considered)
8/14/2019 Bio Inorganic
18/37
Cuboidal three-ironfour-sulfide [Fe3S4] clustersstable oxidation states are 0 and +1
Cubane four-ironfour-sulfide [Fe4S4] clustersstable oxidation states are +1 and +2 for
ferredoxin-type clusters and +2 and +3 for HIPIP clusters.
8/14/2019 Bio Inorganic
19/37
Heme Containing Iron Enzymes
Quaternary structure of
deoxyhemoglobin tetramer
subunits are in blue, and subunits in cyan
8/14/2019 Bio Inorganic
20/37
Comparision of the deoxy Y and oxy R states highlighting the shifts associated with the
quaternary transitions.
Deoxy T statesubunits are shown in blue while the deoxy T state subunits are shown in
cyan; oxy R state subunits are shown in red and oxy R state subunits are shown inorange. The T state hemes are colored in black while the R state hemes in gray
8/14/2019 Bio Inorganic
21/37
Cytochrome P 450cam
HH HH
D C 450
O
HH
O
HOH
8/14/2019 Bio Inorganic
22/37
Catalytic Cycle of Cytochrome P450
R-H
e O2
FeII
SCys
Cys
Fe
S
OO
-
e
Fe
III
SCys
III
-
H2O
R-HR-H
R-OH
R-OHR-H
H+H2O
Cys
HH
Fe
S
O
III
Cys
+Fe
S
O
IV
Resting state
H+
Fe
SCys
O OH
III
Cys
-
Fe
S
OIII
R-H
R-HR-H
Second Oxidant
-
8/14/2019 Bio Inorganic
23/37
450
(1) ,
,
(2) 450
AD 450
(3)
450 ,
(4) ()
(5)
(6) , ,
.
.
8/14/2019 Bio Inorganic
24/37
Spectroscopic Signature of P450
State UV-vis EPR
Resting state Fe(III) 418 nm 2.45, 2.26, 1.91
Resting state Fe(III) + substrate 396 nm 7.85, 3.97, 1.78
Reduced state Fe(II) 408 nm
Reduced state Fe(II) + CO 450 nm
Change of spin is due to change in coordination around Fe from hexa coordinate (with H2O) to pentacordinate
8/14/2019 Bio Inorganic
25/37
Haloperoxidases / Chloroperoxidase
Chloroperoxidase catalyse the formation of C-X bonds (X = I, Br, Cl) in the presence
of H2O2.
But it cannot catalyse the formation of C-F bond. Why???????
This is a 2 e- process.
They are classified as peroxide dependent oxidases.
Structurally quite similar to P450 class with a thiolate axial ligation
Biosynthesis of Caldariomycin
8/14/2019 Bio Inorganic
26/37
Spectroscopy
8/14/2019 Bio Inorganic
27/37
Where Differences End
CPO P450
Polar hydrophilic distal site non polar hydrophobic distal site
Heme edge is available for substrate substrates need to bind closely to FeIV=O
Interaction and e- transfer site.
P450 structure contains deep substrate binding pockets surrounding by hydrophobic
residues for stereo specific hydroxylations.
CPO active site combines the features of enzymes with polar active site and a channel
leading to FeIV=O pocket partly lines with hydrophobic residues
8/14/2019 Bio Inorganic
28/37
8/14/2019 Bio Inorganic
29/37
Phases of Energy Storage in Photosynthesis
Beginning with photon absorption and ending with the export of stable carbon products from the
chloroplast can be sub classified into 4 phases:
(1) Light absorption and energy delivery by antenna systems
(2) Primary electron transfer in reaction centers
(3) Energy stabilization by secondary processes
(4) Synthesis and export of stable products.
Antennas and Energy Transfer Processes
For light energy to be stored by photosynthesis, it must first be absorbed by one of
Photon absorption creates an excited state that eventually leads to charge separation in the reaction
center. The antenna system does not do any chemistry; it works by an energy transfer process that
involves the migration of electronic excited states from one molecule to another.
This is a purely physical process,which depends on a weak energetic coupling of the antenna
pigments.
In almost all cases, the pigments are bound to proteins in highly specific associations.
In addition to chlorophylls, common antenna pigments include carotenoids and open-chain
tetrapyrrole bilin pigments found in phycobilisome antenna complexes.
8/14/2019 Bio Inorganic
30/37
8/14/2019 Bio Inorganic
31/37
(a) General electron transfer scheme in photosynthetic reaction centers. Light excitation promotes a
pigment (P) to an excited state (P*),where it loses an electron to an acceptor molecule (A) to form an ion-
pair state P+A-.
Secondary reactions separate the charges, by transfer of an electron from an electron donor (D) and
from the initial acceptor A to a secondary acceptor (A). This spatial separation prevents the
recombination reaction.
(b) Schematic diagram of cyclic electron transfer pathway found in many anoxygenic photosynthetic
bacteria. The vertical arrow signifies photon absorption: P represents the primary electron donor:D, Aand C represent secondary electron donors, acceptors and carriers.
8/14/2019 Bio Inorganic
32/37
Stabilization by Secondary Reactions
The more familiar oxygen-evolving photosynthetic organisms have a different pattern of electron transfer.
They have two photochemical reaction center complexes that work together in a noncyclic electron transfer chain.
The two reaction center complexes are known as photosystems I and II.
Electrons are removed from water by photosystem II,oxidizing it to molecular oxygen, which is released as a waste
product.
The electrons extracted from water are donated to photosystem I and, after a second light-driven electron transfer step,
eventually reduce an intermediate electron acceptor, NADPH.
Protons are also transported across the membrane and into the thylakoid lumen during the process of the noncyclic
electron transfer,creating a pH difference.
The energy in this pH gradient is used to make ATP.
8/14/2019 Bio Inorganic
33/37
D ( )
D ( )
D1 (), D2 (), C47 (), C43 (), C 559 (),
33 D (), C 550 (), 12 D ( ).
C : C (), (), ( ), A B ,
(), , C (), C ().
8/14/2019 Bio Inorganic
34/37
C (), (), (), C (), & D ()
D1 D2
8/14/2019 Bio Inorganic
35/37
,
0, 1, 2, 3 4.
, 0 1, 1 2, 2 3, 3 4,
4 0 .
D . 0.4
, 0.1 23 .
( )
, (0 : 1 : 2 : 3 = 25% : 25% :
25% : 25%).
B 2 3 1 30100 , .. 0 1
. , 35 0 : 1 = 25% :75%.
8/14/2019 Bio Inorganic
36/37
8/14/2019 Bio Inorganic
37/37