Polysaccharides: Difference between revisions
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=== Branched chain, α(1→4) glycosidic bonds === | === Branched chain, α(1→4) glycosidic bonds === | ||
<scene name='Polysaccharides/9_5_amylopectin1/1'>Amylopectin</scene> is also a large glucose polymer that has α(1→4) glycosidic bonds connecting the glucose units, but it also contains α(1→ 6) glycosidic bonds. In this scene the main branch is colored yellow, the side branch is green and the oxygen atoms of the α(1→4) bonds are red. Rotate <scene name='Polysaccharides/9_5_amylopectin1a/ | <scene name='Polysaccharides/9_5_amylopectin1/1'>Amylopectin</scene> is also a large glucose polymer that has α(1→4) glycosidic bonds connecting the glucose units, but it also contains α(1→ 6) glycosidic bonds. In this scene the main branch is colored yellow, the side branch is green and the oxygen atoms of the α(1→4) bonds are red. Rotate <scene name='Polysaccharides/9_5_amylopectin1a/2'>Amylopectin</scene> to view the glucopyranosyl units on edge and verify that the bonds are α linkages. <scene name='Polysaccharides/9_5_amylopectin2/2'>Glucose unit four</scene>, branching point, colored yellow with the oxygen atom connecting C-6 of unit four to the C-1 of the side chain colored green. The green ring is the reducing end of the molecule. The chain that proceeds from the branching point is colored blue. The yellow rings are the non-reducing ends of the two branches. They just happen to be close to each other in this model. The structure is more open (helix is not wound as tight) than the amylose because more space is needed for the chain that is formed at the branching point. The native amylopectin having many more branching points would be more open than this structure, in fact it would have very little curvature. Rotating & zooming amylopectin gives a focused view of the α(1→ 6) bond. <scene name='Polysaccharides/20_5_10/1'>TextToBeDisplayed</scene> | ||
</StructureSection> | </StructureSection> | ||
Revision as of 20:38, 26 January 2012
The objective of this article is to illustrate and visualize the structures and concepts of common polysaccharides[1] that are difficult to visualize and illustrate by viewing two dimensional structures in textbooks. Structures with a 3D perspective are used to illustrate features of a molecule which can not be easily visualized using 2D structures.
Unbranched chain, α(1→4) glycosidic bondsAmylose is an example of a polysccharide which contains thousands of glucoses connected by α(1→4) glycosidic bonds. The initial view () shows an eleven unit segment of amylose with yellow halos marking some of the oxygens which form the 1→4 glycosidic bonds. Rotate to view the glucopyranosyl units on edge to see that the bonds are α linkages. (Remember: With the glucose providing C-1 on the left, the glucose providing C-4 on the right and C-6 of the glucoses projecting to the back of the screen both bonds of the oxygen of the α linkage project down.) From this perspective you are looking down the axis of a helix that is formed as a result of the angle that is form between the glucopyranosyl residues when they are connected by the α(1→4) bonds. This characteristic of the α(1→4) bond was seen when studying maltose. ends of the polymer yellow and green. with 20 glucose units; Branched chain, α(1→4) glycosidic bondsis also a large glucose polymer that has α(1→4) glycosidic bonds connecting the glucose units, but it also contains α(1→ 6) glycosidic bonds. In this scene the main branch is colored yellow, the side branch is green and the oxygen atoms of the α(1→4) bonds are red. Rotate to view the glucopyranosyl units on edge and verify that the bonds are α linkages. , branching point, colored yellow with the oxygen atom connecting C-6 of unit four to the C-1 of the side chain colored green. The green ring is the reducing end of the molecule. The chain that proceeds from the branching point is colored blue. The yellow rings are the non-reducing ends of the two branches. They just happen to be close to each other in this model. The structure is more open (helix is not wound as tight) than the amylose because more space is needed for the chain that is formed at the branching point. The native amylopectin having many more branching points would be more open than this structure, in fact it would have very little curvature. Rotating & zooming amylopectin gives a focused view of the α(1→ 6) bond.
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