The Ramachandran diagram.
Allowed phi and psi torsion angles in proteins.
The Ramachandran diagram of Gly residues
in a polypeptide chain.
Cis/Trans Isomerization: Proline
C
O
N
N
O
C
trans
C
C
cis
Energy difference between these forms is small.
Nearly all Xaa-Pro linkages are biosynthesized in the trans form.
~10% of these peptide bonds are in the cis form in globular proteins.
Interconversion catalyzed by peptidyl prolyl cis-trans isomerases
Stereo space-filling representation of an  helical segment of
sperm whale myoglobin (its E-helix) as determined by X-ray crystal
structure analysis.
The hydrogen bonding pattern of several polypeptide helices.
Comparison of the two polypeptide helices that occasionally occur
in proteins with the commonly occurring  helix.
b pleated sheet: antiparallel orientation
b pleated sheets: parallel orientation
A two-stranded b antiparallel pleated sheet drawn to
emphasize its pleated appearance.
Stereo space-filling representation of the 6-stranded antiparallel b
pleated sheet in jack bean concanavalin A as determined by crystal
X-ray analysis.
Polypeptide chain folding in proteins illustrating the right-handed
twist of b sheets: bovine carboxypeptidase A.
Polypeptide chain folding in proteins illustrating the right-handed
twist of b sheets: chicken muscle triose phosphate isomerase.
(b barrel)
hairpin
out-of-plane
crossovers
Connections between adjacent polypeptide strands
in b pleated sheets.
Origin of a right-handed crossover connection.
Reverse turns in polypeptide chains.
Space-filling representation of an Ω loop comprising residues 40 to
54 of cytochrome c.
The structure of  keratin.
The two-stranded coiled coil: view down the coil axis showing the
interactions between the nonpolar edges of the  helices.
The two-stranded coiled coil: side view in which the polypeptide
back bone is represented by skeletal (left) and
space-filling (right) forms.
The amino acid sequence at the C-terminal end of the triple helical
region of the bovine 1(I) collagen chain.
The triple helix of collagen.
X-Ray structure of the triple helical collagen model peptide (ProHyp-Gly)10 in which the fifth Gly is replaced by Ala. (a) Ball and stick
representation.
X-Ray structure of the triple helical collagen model peptide (ProHyp-Gly)10 in which the fifth Gly is replaced by Ala. (b) View along
helix axis.
X-Ray structure of the triple helical collagen model peptide (ProHyp-Gly)10 in which the fifth Gly is replaced by Ala. (c) A schematic
diagram.
A biosynthetic pathway for
cross-linking Lys, Hyl, and
His side chains in collagen.
X-Ray diffraction photograph of a single crystal of
sperm whale myoglobin.
Electron density maps of proteins (heme of sperm whale
myoglobin) (2 angstrom resolution)
Electron density maps of proteins (sperm whale myoglobin)
(2.4 angstrom resolution)
Sections through the electron density map of diketopiperazine
calculated at the indicated resolution.
The 2D proton NMR structures of proteins: a NOESY spectrum of
a protein presented as a contour plot with
two frequency axes w1 and w2.
The 2D proton NMR structures of proteins: NMR structure of a 64residue polypeptide comprising the Src protein SH3 domain.
Representations of the X-ray structure of sperm whale myoglobin:
the protein and its bound heme are drawn in stick form.
8 helices
Representations of the X-ray structure of sperm whale myoglobin:
a diagram in which the protein is represented by its computergenerated C backbone.
Representations of the X-ray structure of sperm whale myoglobin:
a computer-generated cartoon drawing.
The X-ray structure of jack bean protein concanavalin A.
Human carbonic anhydrase.
The x-ray structure of horse heart cytochrome c.
(hydrophobic residues in red)
The x-ray structure of horse heart cytochrome c.
(hydrophilic residues in green)
H-helix
Representations of the x-ray structure of sperm whale myoglobin:
a diagram in which the protein is represented by its computergenerated C backbone.
The H helix of sperm whale myoglobin. (a) A helical wheel
representation in which the side chain positions about the  helix are
projected down the helix axis onto a plane.
The H helix of sperm whale myoglobin: a skeletal model.
(orange = nonpolar; purple = polar)
orange = nonpolar
purple = polar
The H helix of sperm whale myoglobin: a space-filling model.
red = nonpolar
purple = polar
A space-filling model of an antiparallel b sheet from
concanavalin A.
two domains
One subunit of the enzyme glyceraldehyde-3-phosphate
dehydrogenase from Bacillus stearothermophilus.
bb

b-hairpin
Schematic diagrams of supersecondary structures.
Greek key motif
Schematic diagrams of supersecondary structures.
directionality of helices
X-ray structures of 4-helix bundle proteins:
E. coli cytochrome b562.
directionality of helices
X-ray structures of 4-helix bundle proteins:
human growth hormone.
stacked 4-stranded and
3-stranded antiparallel
b-sheets
X-ray structure of the immunoglobulin fold.
Up-down b-barrel
X-ray structure of retinol
binding protein.
X-ray structure of the C-terminal domain of bovine g-b crystallin: a
topological diagram showing how its two Greek key motifs are
arranged in a b barrel.
X-ray structure of the C-terminal domain of bovine g-b crystallin:
the 83-residue peptide backbone displayed in ribbon form.
X-ray structure of the enzyme, peptide-N4-(N-acetyl-b-Dglucosaminyl)asparagine amidase F from Flavobacterium
meningosepticum.
X-ray structure of the enzyme, peptide-N 4-(N-acetyl-b-Dglucosaminyl)asparagine amidase F from Flavobacterium
meningosepticum.
The X-ray structure of the 247-residue enzyme triose phosphate
isomerase (TIM) from chicken muscle.
Topological diagrams of (a) carboxypeptidase A and (b) the Nterminal domain of glyceraldehyde-3-phosphate dehydrogenase.
X-ray structures of open b sheet-containing enzymes: dogfish
lactate dehydrogenase, N-terminal domain (residues 20-163 of this
330-residue protein).
X-ray structures of open b sheet-containing enzymes: porcine
adenylate kinase (195 residues).
Doubly wound sheets.
Graphical
Representation
and Analysis of
Surface
Properties
A GRASP diagram of human growth hormone
(helps predict protein interactions with charged molecules)
Thermodynamic changes for transferring hydrocarbons
from water to nonpolar solvents at 25°C.
Hydropathy Scale for Amino Acid Side Chains
Hydropathic index plot for bovine chymotrypsinogen.
Protein
denaturation
curve
strengthen hydrophobic
interactions
Hofmeister series
chaotropic
Weaken hydrophobic
interactions
Melting temperature of RNase A as a function
of the concentration of various salts.
The structural hierarchy in proteins.
The quaternary structure of hemoglobin
Some possible symmetries of proteins with identical protomers. (a)
Assemblies with the cyclic symmetries C2, C3, and C5.
Some possible symmetries of proteins with identical protomers. (b)
Assemblies with the dihedral symmetries D2, D4, and D3.
Some possible symmetries of proteins with identical protomers. (c)
Assemblies with T, O, and I symmetries.
A dimer of transthyretin as viewed down its twofold axis (red
lenticular symbol).
X-ray structure of glutamine synthetase from Salmonella
typhimurium - view down 6-fold symmetry axis
X-ray structure of glutamine synthetase from Salmonella
typhimurium - view down one of the 2-fold symmetry axes
actin, tubulin
A helical structure composed of a single kind of subunit.
Chemical cross-linking agents.
Structural Bioinformatics Websites (URLs)
Structural Bioinformatics Websites (URLs)
Structural Bioinformatics Websites (URLs)