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Discuss the feasibility of using methylation analysis to distinguish between each of the following pairs of carbohydrates:
A) Maltose and Trehalose
B) Maltose and Amylose
C) Amylose and Cellulose

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Methylation analysis is the classic approach to determine the linkage pattern in linked saccharides.

Essentially, there are four steps to the process:

1. methylation of free hydroxyl groups
2. hydrolysis to yield methylated monosaccharides
3. reduction to alditols
4. acetylation

All of this chemistry is followed up by analysis by GC or GC/MS.

What does this accomplish? Free hydroxyl groups on the sugar residues end up being methylated and the rest of the oxygens become acetylated.

You'll need to take a look at the structure of these di/polysaccharides to see this analysis make sense.


In maltose, you have a 1,4 linked disaccharide with two glucose residues. Therefore, the terminal (nonreducing) glucose will end up being 2,3,4,6-tetramethylated (with the 1 and 5 positions being acetylated). The 1 ...

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BIOCHEM GRE Subject Question

You have been investigating a membrane protein that appears to have seven 24 residue transmembrane Alpha helices. Assume that each helix is perpendicular to the plane of the membrane and goes exactly from side of the membrane to the other. Also assume that each helix is linked to the next by a loop with a minimun of 12 amino acid residues.

A) From typical helix parameters and the information given, estimate the thickness of the membrane?

B) What is the minimum number of residues in this protein?

C) Using the result of B) estimate the molecular weight of this protein?

D) How many mainchain H-bonds are in each helix?

E) What types of amino acids residues do you expect to make up the bulk of each transmembrane helix?

F) What types of amino acids residues might you expect to find at the ends of each transmembrane helix?

G) Are the NH2-terminus and COOH terminus on the same side or opposite sides of the membrane?

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