Lecture23

Lecture23 - Lecture 23 11/28/11 Background reading: Berg,...

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Lecture 23 11/28/11 Background reading: Berg, et al: Pages 345 – 350 Garrett and Grisham: Pages 247 – 251; 261 - 263 Outline: Examples of biologically relevant glycans Biological roles of glycans Lectins Lipids Fatty acids Triglycerides Steroids
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Examples of biologically relevant glycans (Continued) Nod factors: Lipopolysaccharide signals made by rhizobial strains of bacteria that initiate the process of the nitrogen-fixing symbiosis between rhizobia and the roots of leguminous plants. O O O O R 6 HO NH C=O CH 3 CH 2 O HO O O NH C=O CH 3 N CH 2 OH CH 2 O R 7 O O R 5 R 4 R 3 R 1 R 2 n They signal the roots to make a new organ, called the nodule, and then enter this organ where they exist in symbiosis with the plant. Backbone is polymer of 3 – 5 GlcNAc β -1,4-GlcNAc residues. A fatty acid is usually present at R 2 . The symbiosis is strain specific where only certain Nod factors can stimulate certain species of legumes. This specificity is due to the fact that the different rhizobial strains add different substituents at the R1 – R7 positions above and different species of legumes have receptors that recognize the specific Nod factors.
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± Biological Roles of Glycans It is now clear that a complex array of glycans exists in nature and may be adapted for a wide variety of roles essential to the that are essential for the living organism. These roles can be divided into two main categories: 1) Structural and modulatory roles. Examples: Maintain a substantial physical barrier for membranes. Help to organize and maintain tissue structure, porosity and integrity.
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This note was uploaded on 01/15/2012 for the course BIS 102 taught by Professor Hilt during the Fall '08 term at UC Davis.

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Lecture23 - Lecture 23 11/28/11 Background reading: Berg,...

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