How does Foldit decide which residues are in the core?
| Case number: | 845833-2012050 |
| Topic: | Game: Display |
| Opened by: | jeff101 |
| Status: | Open |
| Type: | Suggestion |
| Opened on: | Monday, September 13, 2021 - 19:30 |
| Last modified: | Tuesday, September 14, 2021 - 19:10 |
I have a design that keeps giving 0's for the Core Existence: Monomer
and Core Complex Objectives. If you check the Show box for one of these
Objectives, each segment appears blue (protein exterior), green (border
between exterior and core), or orange (core). I think the # of orange
(core) residues determines the scores for the Core Objectives.
That being said, how does Foldit decide which residues to color blue
vs green vs orange? Does Foldit use the Packing or Hiding subscores for
each residue? Does Foldit consider the # of voids near each residue?
Does Foldit consider how many hydrogen bonds each residue has or how
many BUNS are near the residue? Does Foldit consider the hydrophobic
vs hydrophilic nature of each residue? For example, are the amino acids
vwylmpiacfg (orange in the Selection Interface's Mutate Tool) more likely
to be treated as core residues than the amino acids stnqrhkde (blue in
the Selection Interface's Mutate Tool) ? The amino acids w & y are odd
in that they are colored orange in the Mutate Tool even though they can
form hydrogen bonds. Are w & y more likely to be in the protein interior
or on the surface of the protein?
If there are web pages or articles that answer these questions, please
post links here. Also, if there are recipes folks have found helpful for
raising the Core Objectives' scores, please let me know.
Thanks,
Jeff»
Tue, 09/14/2021 - 18:37
#2
The post you cited above says:
The classification of a residue is based on the number of
neighboring Cα atoms that lie within some distance of its
sidechain—or rather, within a cone that radiates out along
the sidechain's Cα-Cβ axis (we usually want to ignore atoms
"behind" the residue that do not interact with the sidechain).
The neighbor "counting" is actually continuous (a residue can
have 3.46 neighbors, for example), but the layer classification
is applied on a hard threshold of this neighbor count.
Below are some questions about this.
What are the neighbor count thresholds for blue/green/orange
or surface/boundary/core residues?
Since glycine doesn't have a Cβ, does it always give 0 for
its neighbor count?
When viewed from the side, a cone looks like a triangle.
I think for the neighbor counting, this triangle will be
isosceles with 2 sides the same length L and a third side
of length B. Is the angle b between the 2 equal sides the
same for all amino acids with Cβ? Using trigonometry, the
triangle should have a height H that obeys:
H/L=cos(b/2) or H=L*cos(b/2).
Similarly, the base B should obey:
B/(2*L)=sin(b/2) or B=2*L*sin(b/2)
as well as:
B/(2*H)=tan(b/2) or B=2*H*tan(b/2).
Do larger amino acids have larger B, H, & L values, making
their cones larger and giving larger neighbor counts? Do
you have a table of the angle b and the lengths B, H, & L
for each of the 20 amino acid types?
Thanks!
Tue, 09/14/2021 - 19:10
#3
Another question is how partial neighbor counts occur.
Does Foldit find the volume of the intersection of the
cone with each nearby Cα atom? Does it divide this
volume by the volume of a Cα atom to get what fraction
of the Cα atom's volume is inside the cone? What is
the Cα atom radius it uses to find these volumes?
Thanks again,
Jeff
The Core Existence Objective classifies each residue as surface/boundary/core based roughly on the number of residues nearby. See a previous explanation here.