Biochemistry exam 1

3.6 aa per turn
5.4 Å per turn
no Gly or Pro
psi is 0 to -70 degrees
rich in Ala and Leu as they are small and fit into the hydrophobic inside
large dipole moment

psi between 90 and 180 degrees
parallel: weaker H bonds (6.5 Å)
antiparallel: more direct/stronger H bonds (7 Å)

Pro is 2nd aa out of 4
carbonyl of 1st aa hydrogen bonds with nitrogen's hydrogen of the 4th aa

6% of Pro is in cis, most of which are in these beta turns

Gly is 3rd aa out of 4
1st aa's carbonyl hydrogen bonds with hydrogen on amine of 4th aa

-- 2 right-handed alpha helices wrapped in parallel, forming a left-handed helix overall
-- 5.2Å per turn instead of the alpha helix 5.4Å
-- hydrophobic interface
-- rich in hydrophobic residues (Ala, Val, Leu, Ile, Met, Phe)
-- disulfide bonds increase strength (rhino horn has 18% aa involved in disulfide bonds)

phi -51, psi 153
right-handed twist overall of 3 left-handed alpha chains
rich in Gly, Ala, Pro, 4-Hyp
Gly-X-Y
X often Pro
Y often 4-Hyp

Beta sheets with hydrogen bonding and extensive van der Waals interactions between sheets
doesn't stretch because B conformation is already highly extended, but it is flexible because the van der Waals interactions can scoot over a few amino acids
antiparallel beta sheets rich in Ala and Gly (often alternating), help stack the sheets tightly