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A
K-E Cross-Strand Pairing
B
V- A Cross-Strand Pairing
C
Q-Q Cross-Strand Pairing
D
Metal H-H Cross-Strand Pairing
Figure 1.7
The concept of programming peptide
-sheet organization
within molecular assemblies through incorporation of cross-
strand pairing interactions. (
β
A
) Salt bridge interactions
β
between K-E and (
-branched amino
acids preferably against less bulk amino acids. (
B
) packing of bulky
C
) Side-chain
hydrogen bonding via glutamine and (
) metal interactions
with peptides containing a single histidine can direct parallel
β
D
-sheet assemblies.
The initial tests for the contributions of cross-sheet interactions
involved the A
peptide fragment HHQALVFFA and metal binding
to the H-H dyad. In the absence of Zn(II), only fibril assemblies
were observed with this peptide; however, following the addition
of 1 molar equivalent of Zn(II), extended
β
-sheet lamination was
apparent in both ribbon and nanotube morphologies [88]. When
either of the two histidines was replaced with alanine, again
β
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