Alpha helices have been mentioned in green colour and beta sheets
are blue in colour.
The chain folds back and forth on itself to create a structure, called a beta sheet, that resembles accordion pleats.
To make the more ordered beta sheet, the researchers found they had to use alanine and glycine at certain positions.
Instead of building the molecule piecemeal, he created a synthetic gene to manufacture beta sheets and spliced it into Escherichia coli bacteria.
Appropriately designed artificial proteins," Tirrell says, "represent a new class of macromolecular materials, with properties potentially quite different from those of the synthetic polymers currently available and in widespread use." For instance, from a carefully designed artificial gene sequence, Tirrell has successfully synthesized a layered crystal made up of stacked beta sheets.
As he did this, he began to realize that rather than forming an alpha helix, peptides with this amino acid sequence can arrange into a different protein structure known as a beta sheet
. In beta sheets
, peptides line up in parallel zigzags called beta strands.
Each unit's longest segment contains a nearly identical sequence of 15 amino acids, which arrange into the so-called beta sheets
that give the molecule its strength.
Several different proteins, such as immunoglobulins and the enzyme superoxide dismutase, have bell-shaped, slatted regions made up of an arrangement of amino acids called beta sheets. Erickson, in collaboration with Jane and David Richardson of Duke University in Durham, N.C., devised a sequence of amino acids that comprises a structure far more regular than any "beta barrels" seen in nature.
To form the beta sheets, he had to alternate small hydrophobic (water-shunning) and hyrophilic (water-loving) amino acids.
The extrusion parameters influenced changes in protein structure in the amide I and II regions and in beta sheet
and alpha helix composition.
Weak links connect these strands into a pleated structure called a beta sheet (SN: 5/15/93, p.316).
As with the development of amyloid plaques in people with Alzheimer's disease, certain molecules take on a seemingly sinister configuration -- the beta sheet -- and accumulate as plaques.