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--- glossary:beta_helix [2008/08/12 15:24]
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+++ glossary:beta_helix [2008/09/17 10:31] (current)
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+{{tag>beta}}
+======  Beta Helix =======
+In this mainly beta fold, the polypeptide chain is wound into a large right-handed coil (or super helix).
+There are two different types of beta helix, one with two [[glossary:beta_sheet | beta sheets]], and one with three beta
+sheets. In our classification scheme we describe these as 2-solenoid and 3-solenoid beta
+[[glossary:architecture | architectures]], respectively.
+__2-solenoid__
+This architecture comprises of two flat beta sheets
+packed tightly against one another. It has a highly
+distinctive and repetitive [[glossary:beta_strand | strand]] connectivity,
+which distinguishes it from the two layer sandwich architecture.
+The chain continually alternates between the two sheet layers whilst progressing in a
+spiraling motion from one end of the structure to the other, hence the
+term 'solenoid.' This could also be classified as a 2-layer beta sandwich but
+its unusual lack of curvature and its unusual topology have led to it being
+identified separately.
+__3-solenoid__
+Structures with this architecture comprise three beta sheets which
+have a distinctive strand connectivity. The chain visits each sheet
+in turn and is progressively wound around the principal axis in
+the same direction.
+===== References =====
+{{pubmed>long:8081735}}
+{{pubmed>long:8081738}}

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