What are carbohydrates Classification of carbohydrate Monosaccharide configurations Carbohydrate conformation Homopolysaccharide folding Conformation and configuration of cellulose Conformation and configuration of starch Experimental determination of polysaccharides structure Conclusions References

1. Polysaccharide
Experimental study of conformational
properties
By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. Contents
• What are carbohydrates
• Classification of carbohydrate
• Monosaccharide configurations
• Carbohydrate conformation
• Homopolysaccharide folding
• Conformation and configuration of cellulose
• Conformation and configuration of starch
• Experimental determination of polysaccharides
structure
• Conclusions
• References

3. What are carbohydrates?
Carbohydrates are polyhydroxy aldehyde or
ketone or substance that yield such compound
on hydrolysis.
Carbohydrate have the empirical formula
(CH2O)n; some also contain nitrogen,
phosphorus, or sulfur.

4. Classification of carbohydrate
Carbohydrate are divided into three major classes
depending upon whether or not they undergo
hydrolysis and if they do, on the number of products
formed.
1) Monosaccharide – The term ‘Monosaccharide’ is
employed for such sugar that on hydrolysis yield
no further, lower sugar. It consist of a single
polyhydroxy aldehyde or ketone units.
Example – Glucose ,Fructose etc.

5. 2) Oligosaccharide – ‘’Oligosaccharide’’ consist
of short chain of monosaccharide unit, joined
by characteristic linkage called glycosidic
bond .
Example – Sucrose, Maltose, lactose etc.
3) Polysaccharide – ‘’Polysaccharides’’ are sugar
polymers containing more than 20 or so
monosaccharide unit, and some have
hundreds or thousands of units.
Example – Cellulose, Starch etc.

6. Monosaccharide configuration
Some of the monosaccharide can occur in either of
two structural configuration;
Open chain and cyclic or ring-
• Cyclic form that contain a six member ring are called
pyranose.
• And those that contain a five member ring are called
furanose.

8. • The Haworth projection of glucose in which the
member of the ring are all depicted as lying in the
same plane is not entirely accurate.
• Though carbon atom 2,3 and 5 and the oxygen atom
lie in the same plane (to form the corners of a
square), carbon atom 1 and 4 lie either slightly above
or below the plane.

9. • This gives rise to the so called boat and chair
form of glucose of which the chair form is
energetically favored.
• Chair form is more stable than boat form.

10. Optical activity
• Enantiomeric pair are identical they exhibit optical
activity. One member of the enantiometric pair will
rotate a plane polarized light in a clockwise direction
and is therefore said to be dextrorotatory.
• And the other enantiomer will rotate the plane of
polarized light to the counter clockwise direction is
known as levorotatory.

11. Epimers
• Sugars that differ only by the stereochemistry,
at single carbon are called epimers

12. Carbohydrate conformation
• Carbohydrate recognition is essential in many
biological function.
• To understand the mechanism for their interaction
knowledge of the carbohydrate 3D structure is of
vast important.
• The 3D structure of carbohydrate is described by its
configuration as well as conformation, the latter
which is defined mainly by the spatial arrangement
of the atom involved in the glycosidic linkage.

13. • Three torsion angle are of important for the
conformation of oligosaccharides, namely
Φ(phi), Ψ(psi),ω(omega) torsion angle.
Fig:- the torsion angle Φ, Ψ and ω for the
disaccharide β-D-glc p-(1—>3) –β-D- gal p.

14. • The ω torsion angle is the most flexible of the
three torsion angle.
• The main electronic effect, is the gauche
effect.
• The term gauche effect refer to
conformational isomers where two vicinal
groups are separated by a torsion angle of
60°.

15. Homopolysaccharide Folding
• The folding of polysaccharides in three
dimensions follows the same principle as
those governing polypeptide structure.
• The three dimensional macromolecular
structures are stabilized by weak interaction
within or between molecules like hydrogen
bond, hydrophobic and Vander Waal
interactions and electrostatic interactions.

16. • Glycogen , starch and cellulose are composed
of pyranoside subunit.
• Such molecules can be represented as a series
of rigid pyranose rings connected by an
oxygen atom bridging two carbon atoms
(glycosidic bond).
• The three dimensional structure of these
molecules can be described in terms of the
dihedral angles Φ and Ψ made with the
glycosidic bonds.

17. Conformation and Configuration of
cellulose
• Cellulose are found in the cell walls of plants.
• In cellulose the glucose residue have the β
configuration.
• The glucose residue in cellulose are linked by β
(1→4) glycosidic bonds.
• The most stable configuration is that in which
each chair is turned 180º relative to its
neighbors , yielding a straight extended chain.

18. • A stabilizing network of inter chain and intra
chain hydrogen bonds produces straight,
stable supra molecules fibers of great tensile
strength.
• It shows ribbon like conformation.
• This property of cellulose has made it a useful
substance like paper, cardboard etc.

20. Conformation and Configuration of
starch
• Starch is a complex carbohydrate present in
plants.
• A constituent of starch is amylose which is
polyglucose macromolecule with α (1→4)
linkage.
• The most stable three dimensional structure
of starch is tightly coiled helix.
• The helical structure has six residue per turn.

21. • The core of the helix is hollow which
accommodate iodine in the form I³- and this
interaction with iodine is a common
qualitative test for amylose.
• The helix is stabilized by interchain hydrogen
bonds.

22. Fig : Three dimensional structure of starch

25. Experimental determination of
polysaccharide structures
NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY :
• A valuable non- destructive and reasonably
sensitive technique for structural and
conformational determination.
X – RAY DIFFRACTION :
• It is one of the most important non destructive
tool to analyze all kind of matter ranging from
fluid to powder and crystals.

26. Conclusions
• The most stable arrangement of atoms in a
polysaccharides will be that which satisfies
both the intra molecular and inter molecular
forces.
• And the most stable three dimensional
structure for starch is a tightly coiled helix
stabilizing by interchain hydrogen bonds.
• Polysaccharide polymers with α glucose are
helical where as with β glucose are straight.

27. References
• Lehninger PRINCIPLES OF BIOCHEMISTRY
Fifth edition. By : DAVID L. NELSON and
MICHAEL M. COX.
• Research Paper:
1. Structural and conformational studies of oligo
and polysaccharides © MONA ZACCHEUS
department of organic chemistry, Stockholm
University 2012.