<s>
Ribbon	B-Application
diagrams	I-Application
,	O
also	O
known	O
as	O
Richardson	B-Application
diagrams	I-Application
,	O
are	O
3D	O
schematic	O
representations	O
of	O
protein	O
structure	O
and	O
are	O
one	O
of	O
the	O
most	O
common	O
methods	O
of	O
protein	O
depiction	O
used	O
today	O
.	O
</s>
<s>
Ribbon	B-Application
diagrams	I-Application
are	O
generated	O
by	O
interpolating	O
a	O
smooth	O
curve	O
through	O
the	O
polypeptide	O
backbone	O
.	O
</s>
<s>
Ribbon	B-Application
diagrams	I-Application
are	O
simple	O
yet	O
powerful	O
,	O
expressing	O
the	O
visual	O
basics	O
of	O
a	O
molecular	O
structure	O
(	O
twist	O
,	O
fold	O
and	O
unfold	O
)	O
.	O
</s>
<s>
The	O
first	O
ribbon	B-Application
diagrams	I-Application
,	O
hand-drawn	O
by	O
Jane	O
S	O
.	O
Richardson	O
in	O
1980	O
(	O
influenced	O
by	O
earlier	O
individual	O
illustrations	O
)	O
,	O
were	O
the	O
first	O
schematics	O
of	O
3D	O
protein	O
structure	O
to	O
be	O
produced	O
systematically	O
.	O
</s>
<s>
In	O
1982	O
,	O
Arthur	O
M	O
.	O
Lesk	O
and	O
co-workers	O
first	O
enabled	O
automatic	O
generation	O
of	O
ribbon	B-Application
diagrams	I-Application
through	O
a	O
computational	O
implementation	O
that	O
uses	O
Protein	O
Data	O
Bank	O
files	O
as	O
input	O
.	O
</s>
<s>
This	O
conceptually	O
simple	O
algorithm	O
fit	O
cubic	O
polynomial	O
B-spline	B-Algorithm
curves	O
to	O
the	O
peptide	O
planes	O
.	O
</s>
<s>
Most	O
modern	O
graphics	O
systems	O
provide	O
either	O
B-splines	B-Algorithm
or	O
Hermite	O
splines	O
as	O
a	O
basic	O
drawing	O
primitive	O
.	O
</s>
<s>
To	O
give	O
the	O
right	O
radius	O
for	O
helical	O
spirals	O
while	O
preserving	O
smooth	O
β-strands	O
,	O
the	O
splines	O
can	O
be	O
modified	O
by	O
offsets	O
proportional	O
to	O
local	O
curvature	O
,	O
as	O
first	O
developed	O
by	O
Mike	O
Carson	O
for	O
his	O
Ribbons	O
program	O
and	O
later	O
adapted	O
by	O
other	O
molecular	O
graphics	O
software	O
,	O
such	O
as	O
the	O
open-source	O
Mage	O
program	O
for	O
kinemage	B-Application
graphics	O
that	O
produced	O
the	O
ribbon	O
image	O
at	O
top	O
right	O
(	O
other	O
examples	O
:	O
and	O
)	O
.	O
</s>
<s>
Since	O
their	O
inception	O
,	O
and	O
continuing	O
in	O
the	O
present	O
,	O
ribbon	B-Application
diagrams	I-Application
have	O
been	O
the	O
single	O
most	O
common	O
representation	O
of	O
protein	O
structure	O
and	O
a	O
common	O
choice	O
of	O
cover	O
image	O
for	O
a	O
journal	O
or	O
textbook	O
.	O
</s>
<s>
One	O
popular	O
program	O
used	O
for	O
drawing	O
ribbon	B-Application
diagrams	I-Application
is	O
Molscript	O
.	O
</s>
<s>
Jmol	B-Language
is	O
an	O
open-source	O
Java-based	O
viewer	O
for	O
browsing	O
molecular	O
structures	O
on	O
the	O
web	O
;	O
it	O
includes	O
a	O
simplified	O
"	O
cartoon	O
"	O
version	O
of	O
ribbons	O
.	O
</s>
<s>
UCSF	B-Application
Chimera	I-Application
is	O
a	O
powerful	O
molecular	O
modeling	O
program	O
that	O
also	O
includes	O
visualizations	B-Application
such	O
as	O
ribbons	O
,	O
notable	O
especially	O
for	O
the	O
ability	O
to	O
combine	O
them	O
with	O
contoured	O
shapes	O
from	O
cryo-electron	O
microscopy	O
data	O
.	O
</s>
<s>
PyMOL	B-Application
,	O
by	O
Warren	O
DeLano	O
,	O
is	O
a	O
popular	O
and	O
flexible	O
molecular	O
graphics	O
program	O
(	O
based	O
on	O
Python	B-Language
)	O
that	O
operates	O
in	O
interactive	O
mode	O
and	O
also	O
produces	O
presentation-quality	O
2D	O
images	O
for	O
ribbon	B-Application
diagrams	I-Application
and	O
many	O
other	O
representations	O
.	O
</s>
