Spider silk is remarkably strong, its tensile strength is superior to that of steel and it is extremely lightweight: a strand of spider-silk long enough to circle the earth would weigh less than 500 g. In a typical spider silk strand, crystalline beta-sheet regions, which are rich in glycine- and alanine, alternate with amorphous segments. The latter are responsible for the sticky or non-sticky properties, depending on the kind of spider silk. Why are glycine and alanine especially suited for the formation of beta-sheet regions?
I. Glycine and alanine are hydrophobic and cause the hydrophobic sticking of neighboring polymer strands.
II. Glycine and alanine feature very little or no steric hindrance for the formation of hydrogen bonds between neighboring protein strands.
III. Glycine and alanine feature very little or no steric hindrance for the formation of hydrogen bonds within a protein strands.
IV. Glycine and alanine are polar. They allow ionic interactions between neighboring polymer chains.

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The Answer of Spider silk is remarkably strong, its tensile strength is superior to that of steel and it is extremely lightweight: a strand of spider-silk long enough to circle the earth would weigh less than 500 g. In a typical spider silk strand, crystalline beta-sheet regions, which are rich in glycine- and alanine, alternate with amorphous segments. The latter are responsible for the sticky or non-sticky properties, depending on the kind of spider silk. Why are glycine and alanine especially suited for the formation of beta-sheet regions?
I. Glycine and alanine are hydrophobic and cause the hydrophobic sticking of neighboring polymer strands.
II. Glycine and alanine feature very little or no steric hindrance for the formation of hydrogen bonds between neighboring protein strands.
III. Glycine and alanine feature very little or no steric hindrance for the formation of hydrogen bonds within a protein strands.
IV. Glycine and alanine are polar. They allow ionic interactions between neighboring polymer chains.

Spider Silk Is Remarkably Strong, Its Tensile Strength Is Superior