in this presentation, one can see the structure, properties, function, binding capacity with Carbon dioxide and oxygen, co-ordination chemistry in myoglobin, difference and similarities with haemoglobin.

1. Presented By :Maryam Akhtar
Roll No : 19002067004

2. Introduction
Structure and bonding
Heme protein-ligand interaction.
Co-ordination geometry.
Formation of linear Fe-O-O bond.
Binding of CO.
Binding of O2
Function of myoglobin.
Role in cuisine.
Role in disease.
Comparison with Hb
1.Renal failure
2.Heart attack
3.Myoglobinuria
PRESENTATION
LAYOUT

3. INTRODUCTION

4. MYOGLOBIN FEATURES
Myoglobin facilitates oxygen diffusion.
It desaturates at the onset of muscle
activity.
It increases oxygen's diffusion gradient
from capillaries to the cytoplasm.
It has enzymatic functions.
It is necessary for the decomposition of
bioactive nitric oxide to nitrate.
Myoglobin is a red
protein containing
haem, which carries
and stores oxygen in
muscle cells.
Myoglobin was the first
protein to have its
three-dimensional
structure revealed by
X-ray crystallography.

5.  Myoglobin belongs to the globin
superfamily of proteins
 It consists of eight alpha
helices connected by loops.
 It contains family of heme-
containing globular polypeptides
with eight α -helices in their
protein fold.
 Myoglobin contains 154 amino
acids.
 It is similar to the structure of one
of the β subunits of hemoglobin.
STRUCTURE OF MYOGLOBIN

6.  BONDING IN MYOGLOBIN
Inset A shows enlarged view of the O2-bound heme.
Inset B illustrates the de-oxygenated heme.
Inset C shows reversible binding of O2 to the skeletal
structure of the heme prosthetic group.
STRUCTURE OF MYOGLOBIN.
The heme group, shown in stick
depiction (tan) with Fe shown as
an orange sphere, bound to a
O2 molecule (red ball-and-stick).

7. FUNCTION OF Mb
 Myoglobin facilitates oxygen
diffusion.
 Myoglobin desaturates at the onset of
muscle activity, which increases
oxygen's diffusion gradient from the
capillaries to the cytoplasm.
 Myoglobin has also been shown to
have enzymatic functions.
 It is necessary for the decomposition
of bioactive nitric oxide to nitrate.

8.  Heme is a square planar molecule containing four pyrrole groups, whose nitrogens form coordinate
covalent bonds with four of the iron's six available positions.
 One position is used to form a coordinate covalent bond with the side chain of a single histidine amino
acid of the protein, called the proximal histidine.
 The sixth and last orbital is used for oxygen. It is empty in the nonoxygenated forms of
myoglobin.
 When molecular oxygen encounters an isolated heme molecule, it rapidly converts the Fe(II) to Fe(III).
The oxidized heme binds oxygen very poorly. Obviously, if this happened to the Fe(II) groups of
myoglobin, the proteins would be less useful as oxygen carriers.
FORMATION OF LINEAR Fe-O-O bond
Oxidation of the heme iron is prevented by the presence of the distal histidine side chain, which prevents
the O2 from forming a linear Fe–O–O bond. The bond between Fe and O 2 is bent, meaning that this bond is
not as strong as it might be. Weaker oxygen binding means easier oxygen release.
HEME-PROTEIN LIGAND FORMATION
Ligands like CN–, CO, and O2 bind to myoglobin (Mb). It remains unclear whether any of these ligand-
bound forms can be observed by Electrospray ionization (ESI)-mass spectrometry (MS).
it provide information on protein–ligand interactions via detection of the corresponding complexes as
gaseous ions.
Role of Co-ordination chemistry

9. Data from infrared (IR) spectroscopy and magnetic measurements have lead scientists to propose
two different modes of oxygen binding to the iron ion.
Fe Oxidation State and Electronic Structure
Right: illustrates
the formation of
the superoxide
from the transfer
of electrons from
oxygen to iron
Left: illustrates the
iron oxide binding
of oxygen where
there is no transfer
of electrons from
the oxygen to the
iron ion.

10. IRON-OXYGEN COMPLEX
 The resulting iron-oxygen complex of heme becomes
diamagnetic as all electrons are paired in the resulting
molecular oritals .
 This suggests that oxygen binding to the Fe(II) ion
is favored because the complex becomes
diamagnetic.
 To assign an oxidation state to the bound iron or the
oxygen.
 The two extremes, where one is that Fe becomes an iron
superoxide by donating an electron from iron to the
oxygen, and the other that Fe becomes an iron oxide by
sharing the electrons are probably both incorrect.
 The molecular orbitals contain characteristics of both iron
superoxide and iron oxide.

11. BINDING OF OXYGEN TO MYOGLOBIN
• Myoglobin are hemeproteins whose physiological
importance is related to their ability
to bind molecular oxygen.
• The oxygen carried by myoglobin is bound directly to the
ferrous iron (Fe2+) atom of the heme prosthetic group.
• Each myoglobin molecule is capable of binding one
oxygen, because myoglobin contains one heme per
molecule.
MEASUREMENT
Reaction of myoglobin and oxygen takes place in solution, it
is convenient to measure the concentration of oxygen in
terms of its partial pressure, the amount of gas in the
atmosphere that is in equilibrium with the oxygen in solution.
The titration curve of myoglobin with oxygen is a hyperbola;
 FACTOR AFFECTING
BINDING
Whether myoglobin binds to
oxygen depends on the
presence of the prosthetic
group, heme. When
myoglobin is able to bind to
oxygen, it serves as the
primary oxygen-carrying
molecule in muscle tissue.
Normally, the iron group in
myoglobin has an oxidation
state of 2+.

12.  Y = fraction of oxygenated myoglobin.
 pO2= Partial pressure of O 2, expressed in torr.
 P0 = Partial pressure of O2 required to bind 50% of the myoglobin
molecules.
SPECIAL CASE
If Y is set at 0.5,
P50 = pO 2.

13. Figure: OXYGEN BINDING TO MYOGLOBIN
(a) .
(b) When O2 binds to deoxymyoglobin, the
iron is converted to low-spin Fe3+, which is
smaller, allowing the iron to move into the
plane of the four nitrogen atoms of the
porphyrin to form an octahedral complex
(a) The Fe2+ ion in
deoxymyoglobin is high spin,
which makes it too large to fit
into the “hole” in the center of
the porphyrin

14. HOW DOES MYOGLOBIN PREVENTS
THE BINDING OF CO?
 The distal imidazole is not bonded to the iron
but is available to interact with the substrate
O2.
 This interaction encourages the binding of O2,
but not carbon monoxide (CO), which still
binds about 240× more strongly than O2.
 The binding of O2 causes substantial structural
change at the Fe center, which shrinks in radius
and moves into the center of N4 pocket. O2-
binding induces "spin-pairing": the five-
coordinate ferrous deoxy form is high spin
and the six coordinate oxy form is low spin
and diamagnetic.

16. o Myoglobin contains hemes, pigments responsible for the colour of red
meat.
o The colour that meat takes is partly determined by the degree of
oxidation of the myoglobin.
o In fresh meat the iron atom is in the ferrous (+2) oxidation state bound
to an oxygen molecule (O2). Meat cooked well done is brown because
the iron atom is now in the ferric (+3) oxidation state, having lost an
electron.
o If meat has been exposed to nitrites, it will remain pink because the iron
atom is bound to NO, nitric oxide
o Grilled meats can also take on a reddish pink "smoke ring" that comes
from the heme center binding to carbon monoxide.
o Raw meat packed in a carbon monoxide atmosphere also shows this
same pink "smoke ring" due to the same principles.
ROLE IN CUISINE

17. DISEASE
CAUSED BY
MYOGLOBIN
ACUTE RENAL FAILURE
HEART ATTACK
MYOGLOBINURI
A

18. RENAL FAITURE
When muscle is damaged, a
protein called myoglobin is
released into the
bloodstream. It is then
filtered out of the body by
the kidneys. Myoglobin
breaks down into substances
that can damage kidney
cells.
MYOGLOBINURIA
It is the presence of
myoglobin in the urine,
which usually results from
rhabdomyolysis or
muscle injury.it may
occlude the kidney
filtration system to acute
tubular necrosis.
HEART ATTACK
Negative myoglobin result
effectively rules out a heart
attack, a positive result
must be confirmed by
testing for troponin.
Increased myoglobin levels
can occur after muscle
injections or strenuous
exercise.
ROLE
IN
DISEASES

19. DIFFERENCES
SIMILARITIES
Hb Mb

20. Thank You Folks For
listening me….!