Conformational properties of polysaccharides

INTRODUCTION

CONCEPT AND TERMINOLOGIES ABOUT CONFORMATIONS

DIHEDRAL ANGLES AND A MAP OF FAVORED CONFORMATIONS
 
CLASSES OF CONFORMATIONS WITH EXAMPLES
ORDERED CONFORMATION
DISORDERED CONFORMATION

IMPORTANCE OF CONFORMATIONAL PROPERTIES

CONCLUSIONS

REFERENCES

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

2. SYNOPSIS INTRODUCTION CONCEPT AND TERMINOLOGIES ABOUT CONFORMATIONS DIHEDRAL ANGLES AND A MAP OF FAVORED CONFORMATIONS   CLASSES OF CONFORMATIONS WITH EXAMPLES ORDERED CONFORMATION DISORDERED CONFORMATION IMPORTANCE OF CONFORMATIONAL PROPERTIES CONCLUSIONS REFERENCES  

3. INTRODUCTION Carbohydrates or saccharides (Greek: sakcharon , sugar) are the most abundant biological molecules. Polysaccharides , the polymers of sugars, have storage and structural role. In order to understand the molecular basis of polysaccharides in relation to their functional properties, it is important to appreciate higher levels of structures of polysaccharides based on the shape or conformation of these polymers in nature.

4. CONCEPTS AND TERMINOLOGIES BASIC TERMS ABOUT STRUCTURES ENANTIOMERS ; The enantiomers are mirror images of each other. The total number of isomers can be determined by using Vant Hoff’s rule ( 2 n ).

5. EPIMERS : SUGARS THAT DIFFER ONLY BY THE STEREOCHEMISTRY AT A SINGLE CARBON (NOT ANOMERIC CARBON ) ARE CALLED EPIMERS.

6. LINEAR AND CYCLIC FORM

7. ANOMERS: MUTAROTATION: - Mutarotation is the interconversion of the  and  anomer

8. CONCEPT OF DIFFERENT CONFORMATIONS The relative orientations between any two participating monosaccharide units are defined by two or three torsion angles around the glycosidic bonds. The conformation of any individual monosaccharide is relatively fixed in the polysaccharide chain, however, the sugar residues linked through glycosidic linkage will rotate around the glycosidic bond and often tend to adopt an orientation of lower or lowest energies.

9. Three dimensional structure can be described in terms of dihedral angles ф and ψ about glycosidic bond. DIHEDRAL ANGLES AND A MAP OF FAVORED CONFORMATIONS

10. A map of favored conformations for oligosaccharides and polysaccharides. red dot-least f favored conformation , blue dot -most favored conformation.

11. CLASSES OF CONFORMATION OF POLYSACCHARIDES Ordered conformation Ribbon-like type conformation Hollow helix like conformation Periodic type conformation Disordered conformation Random coiling

12. Cellulose cellulose Cellulose microfibrils in a plant cell wall

13. Starch Suspensions of amylose in water adopt a helical conformation . A model of a segment of amylose

14. (a) Starch: a plant polysaccharide (b) Glycogen: an animal polysaccharide Chloroplast Starch granules Mitochondria Glycogen granules Amylose Amylopectin Glycogen

15. The favored conformation of agarose in water is a double helix AGAROSE

16. DISORDERED CONFORMATION ALGINATE Like cellulose, chitin, mannan , and poly(D- mannuronate ) form extended ribbons and pack together efficiently, taking advantage of multiple hydrogen bonds . Poly( _ -L- guluronate ) strands dimerize in the presence of Ca2 _ , forming a structure known as an “egg carton.”

17. IMPORTANCE OF CONFORMATIONAL PROPERTIES In storage In protection In laboratories In transport

18. CONCLUSIONS Polymers with  glucose are helical. Polymers with  glucose are straight. In straight structures, H atoms on one strand can bond with OH groups on other strands. There is direct relationship between the three-dimensional structures of oligosaccharides and polysaccharides and their biological properties . The overall conformation of an oligosaccharide depends primarily on the orientation of the torsion angles ( ф and ψ ) between glycosyl residues.

19. REFERENCES LEHNINGER PRINCIPLE OF BIOCHEMISTRY BY DAVID L. NELSON AND MICHAEL M. COX - 5 TH EDITION. BIOCHEMISTER BY GARRET AND GRISHAM . BIOCHEMISTRY BY VOET AND VOET.