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/* Copyright (C) 2003 Damir Zucic */
/*=============================================================================
beta_membrane.c
Purpose:
Find the position and orientation of the membrane with respect to
the macromolecular structure. The structure in question should be
some membrane protein of beta barrel type. This function wil fail
to work properly for alpha helix bundle proteins.
Input:
(1) Pointer to MolComplexS structure, with the chosen structure.
(2) Pointer to RuntimeS structure.
(3) Pointer to ConfigS structure (stereo angle required).
(4) Pointer to GUIS structure.
Output:
(1) The membrane position and orientation will be calculated for
the first time or updated.
(2) Return value.
Return value:
(1) Positive on success.
(2) Negative on failure.
Notes:
(1) A short description of some tricks used in this function:
-------------------------------------------------------------
Step 1: Find the geometric center for CA atoms. Ignore hetero
atoms (water, lipids, cofactors etc.). Ignore all other atoms
too (C, N, O, side chain atoms etc.).
-------------------------------------------------------------
Step 2: Use the CA geometric center and some arbitrary vector
to create an axis in space. Associate a cylinder with this
axis. The length of this cylinder should be 120 angstroms and
the radius may be arbitrary. Divide the cylinder into patches
of equal size. The height of a single patch should be 3.0
angstroms (see the parameter CELL_LINEAR_WIDTH in defines.h)
and the patch angular width should correspond to the angular
range of 36 degrees. Note that the radius of the cylinder and
the width of a single patch are not important: what really
matters is the angular range of a single patch. Associate an
array of cells (data structures) with this cylinder. Scan the
protein structure, residue by residue. For a given residue,
check the CA-CB vector. If this vector points inwards with
respect to the given axis, ignore this residue. Otherwise,
project the CB atom position to the surface of the cylinder.
Identify the patch to which the CB atom was projected. Find
the distance between the CB atom and the axis. Check the
distance which was stored before to the cell associated with
the patch to which the CB atom was projected. If the current
CB is more distant from the axis than the CB atom which was
the most distant atom projected before to this patch, occupy
the cell with the current CB atom: store the hydrophobicity
of the current residue and the distance between CB and the
axis.
-------------------------------------------------------------
Step 3: Divide the cylinder surface into stripes, parallel to
the cylinder surface. For each cell in each stripe, calculate
the average hydrophobicity over a given number of neighboring
cells. These cells should belong to the same stripe. The
sliding window should be comparable to the membrane thickness
(or slightly smaller). The unused cells should be ignored. It
is possible that average hydrophobicity will not be available
for all cells after this step, but this should not cause any
major problems. Most of the cells in the central part of the
cylinder surface will be filled with average hydrophobicity.
-------------------------------------------------------------
Step 4: Divide the cylinder surface into rings. In this step,
the averaged hydrophobicities will be used to calculate the
second average, this time combining values from the cells
which belong to the same ring. This procedure is repeated for
each ring. Ignore cells which were skipped in the previous
step, i.e. which are missing the average hydrophobicity
value.
-------------------------------------------------------------
Step 5: Find the most hydrophobic ring. Store the second
average of hydrophobicity for later usage. The same procedure
is repeated for a number of axes, to cover the full space
angle of 4 PI steradijans. Find the axis which gives the
highest second average of hydrophobicity. Use the unit vector
of this axis as the initial unit vector perpendicular to the
membrane. Together with the CA center, this is just enough to
define the membrane.
-------------------------------------------------------------
Step 6: Refine the orientation of the normal vector. Look for
two rings of aromatic residues, PHE, TRP and TYR. Ignore HIS.
The transmembrane part of the beta barrel protein has a ring
of aromatic residues PHE, TRP and TYR at each end. Ignore all
residues pointing outwards with respect to the axis. Project
eacg CG atom to a number of cells, covering few angstroms.
-------------------------------------------------------------
Step 7: Refine the position of the membrane center. Up to now
the position of CA center was used as the membrane center but
this is obviously wrong. Project CG atoms of PHE, TRP and TYR
over a number of cells, so that each CG covers few angstroms.
-------------------------------------------------------------
(2) The minimal distance between the point (x, y, z) and the axis
passing through the point (x0, y0, z0), pointing in direction
(l, m, n) is:
1
d^2 = --------------- { [ (x - x0) m - (y - y0) l ]^2 +
l^2 + m^2 + n^2
[ (y - y0) n - (z - z0) m ]^2 +
[ (z - z0) l - (x - x0) n ]^2 }
Using x - x0 = dx, y - y0 = dy, z - z0 = dz, l = ex, m = ey
and n = ez, where ex, ey and ez are three components of the
axis unit vector, the equation looks simpler:
distance_squared = (dx * ey - dy * ex)^2 +
(dy * ez - dz * ey)^2 +
(dz * ex - dx * ez)^2 .
The formula was taken from the famous mathematical handbook
by I.N. Bronstein and K.A. Semendjajew. However, it was used
only for debugging and later it was removed. The distance is
now calculated using the absolute value of the perpendicular
component of the CA_center_CB_vectorS. The expression from
the book was used only to do one extra check.
(3) Two strange terms are used here: beta cells and simple cells.
The auxiliary cylinder is divided into "beta cells" and the
axis used for refinement is divided into "simple cells".
(4) Indentation is exceptionally 4 spaces.
========includes:============================================================*/
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/Xos.h>
#include <X11/Xatom.h>
#include "defines.h"
#include "typedefs.h"
/*======function prototypes:=================================================*/
int ExtractCA_ (VectorS *, AtomS *, size_t, size_t);
int ExtractCACB_ (VectorS *, VectorS *, AtomS *, size_t, size_t);
double ScalarProduct_ (VectorS *, VectorS *);
void VectorProduct_ (VectorS *, VectorS *, VectorS *);
double AbsoluteValue_ (VectorS *);
int ExtractCG_ (VectorS *, AtomS *, size_t, size_t);
/*======find membrane position (beta barrel version):========================*/
int BetaMembrane_ (MolComplexS *mol_complexSP,
RuntimeS *runtimeSP, ConfigS *configSP, GUIS *guiSP)
{
double membrane_thickness;
int simple_cells_along_axisN;
double simple_cell_width, recip_simple_width;
double projection_width;
int simple_window_width, half_simple_window_width;
double scan_half_width;
int simple_scan_half_width;
int max_simpleI, simple_thickness, half_simple_thickness;
int beta_cells_along_axisN, cells_in_ringN, half_cells_in_ringN;
double beta_cell_linear_width, recip_beta_lin_width;
double beta_cell_angular_width, recip_beta_ang_width;
int half_window_width, window_width;
int beta_index_offset, simple_index_offset;
size_t atomsN;
int residuesN, residueI;
ResidueS *residueSP;
int n;
VectorS CA_vectorS;
VectorS CA_center_vectorS;
int CA_atomsN;
double reciprocal_denominator;
int thetaI, max_thetaI, phiI, max_phiI;
double theta, theta_step, phi, phi_step;
VectorS axis_unit_vectorS;
VectorS aux_vectorS;
double scalar_product;
double abs_value, reciprocal_abs_value;
VectorS unit_vector2S, unit_vector3S;
int beta_cellI;
BetaCellS *beta_cellSP;
VectorS CB_vectorS;
VectorS CA_CB_vectorS;
VectorS CA_center_CB_vectorS;
VectorS parallel_vectorS;
VectorS perpendicular_vectorS;
double distance;
double sin_angle, cos_angle, angle;
int axialI, radialI;
int localI, combined_radialI;
AtomS *first_atomSP;
double hydrophobicity, average_hydrophobicity;
int cells_usedN;
int windowI;
int combined_axialI;
double second_average;
int best_second_average_foundF;
double best_second_average;
VectorS best_unit_vectorS;
VectorS i1_unit_vectorS, j1_unit_vectorS, k1_unit_vectorS;
int total_phe_trp_tyrN;
char *pure_residue_nameP;
double cos_theta, sin_theta, cos_phi, sin_phi;
int two_rings_count, best_two_rings_count;
int central_simpleI, start_simpleI, end_simpleI, simpleI;
int phe_trp_tyrNA[SIMPLE_CELLS_ALONG_AXIS];
VectorS CG_vectorS;
VectorS CA_center_CG_vectorS;
int start_pointI, end_pointI, pointI;
double shift, best_shift;
VectorS center_vectorS;
VectorS radius_vectorS;
double projection;
int ring1I, ring2I;
/*---------------------------------------------------------------------------*/
/* Copy the membrane thickness: */
membrane_thickness = mol_complexSP->membraneS.thickness;
/* Copy the number of simple cells along the axis: */
simple_cells_along_axisN = SIMPLE_CELLS_ALONG_AXIS;
/* Prepare the linear width of a single simple cell: */
simple_cell_width = SIMPLE_CELL_WIDTH;
recip_simple_width = 1.0 / simple_cell_width;
/* Prepare the projection width. The projection of */
/* CG atom will be smeared over a number of cells. */
projection_width = 5.0; /* angstroms. */
/* Prepare the width of a simple window. A single CG atom will */
/* be projected over a number of cells. The simple_window_width */
/* defines how many cells will be covered by a single CG atom. */
simple_window_width = recip_simple_width * projection_width;
half_simple_window_width = simple_window_width / 2;
/* During the refinement of the membrane center, a range of positions */
/* along the refined unit vector should be scanned. It is defined here: */
scan_half_width = 100.0;
simple_scan_half_width = (int) (scan_half_width * recip_simple_width);
/* The initial number of simple cells across the given membrane thickness. */
/* This value will be changed before the refinement of the membrane center. */
simple_thickness = (int) (membrane_thickness / simple_cell_width);
if (simple_thickness < 3) simple_thickness = 3;
half_simple_thickness = simple_thickness / 2;
/* Maximal value of the simple index. The simple index is */
/* used during the refinement. The maximal value set here */
/* should prevent the array overflow. Note that ten cells */
/* are wasted, to ensure there will be no array overflow. */
max_simpleI = simple_cells_along_axisN - 1 - simple_thickness - 10;
if (max_simpleI < 0) max_simpleI = 0;
/* Copy the number of beta cells along the axis of the auxiliary cylinder: */
beta_cells_along_axisN = BETA_CELLS_ALONG_AXIS;
/* Copy the number of cells in a single ring around the auxiliary cylinder: */
cells_in_ringN = BETA_CELLS_IN_RING;
half_cells_in_ringN = cells_in_ringN / 2;
/* Prepare the linear width of a single beta cell: */
beta_cell_linear_width = BETA_CELL_LINEAR_WIDTH;
recip_beta_lin_width = 1.0 / beta_cell_linear_width;
/* Prepare the angular width of a single beta cell: */
beta_cell_angular_width = 6.2831853 / (double) cells_in_ringN;
recip_beta_ang_width = 1.0 / beta_cell_angular_width;
/* Prepare the sliding window width. This number should */
/* be odd. It should not reach the hydrophilic residues. */
n = (int) (membrane_thickness / beta_cell_linear_width);
half_window_width = (n - 1) / 2;
if (half_window_width < 1) return -1;
window_width = 2 * half_window_width + 1;
/* The height of the CA center with respect to the base of the */
/* cylinder should reach the middle of the auxiliary cylinder. */
/* To ensure this, the axial index should be shifted properly: */
beta_index_offset = beta_cells_along_axisN / 2;
/* During the refinement, the CA center should be */
/* projected to the central cell along the axis. */
simple_index_offset = simple_cells_along_axisN / 2;
/* Copy and check the number of atoms: */
atomsN = mol_complexSP->atomsN;
if (atomsN == 0) return -2;
/* Copy and check the number of residues: */
residuesN = mol_complexSP->residuesN;
if (residuesN < window_width) return -3;
/*------(1) find the geometric center for CA atoms:-------------------------*/
/* Initialize the CA center: */
CA_center_vectorS.x = 0.0;
CA_center_vectorS.y = 0.0;
CA_center_vectorS.z = 0.0;
/* Initialize the number of CA atoms: */
CA_atomsN = 0;
/* Scan the macromol. complex, residue by residue, ignoring water molecules: */
for (residueI = 0; residueI < residuesN; residueI++)
{
/* Pointer to the current residue: */
residueSP = mol_complexSP->residueSP + residueI;
/* Try to extraxt the coordinates of CA atom: */
n = ExtractCA_ (&CA_vectorS, mol_complexSP->atomSP,
residueSP->residue_startI,
residueSP->residue_endI);
if (n < 1) continue;
/* Update the CA geometric center: */
CA_center_vectorS.x += CA_vectorS.x;
CA_center_vectorS.y += CA_vectorS.y;
CA_center_vectorS.z += CA_vectorS.z;
/* Update the counter of CA atoms: */
CA_atomsN++;
}
/* If there were no CA atoms at all, return error indicator: */
if (CA_atomsN == 0) return -4;
/* Calculate the geometric center of CA atoms: */
reciprocal_denominator = 1.0 / (double) CA_atomsN;
CA_center_vectorS.x *= reciprocal_denominator;
CA_center_vectorS.y *= reciprocal_denominator;
CA_center_vectorS.z *= reciprocal_denominator;
/* Take this point as the initial membrane center: */
mol_complexSP->membraneS.center_x = CA_center_vectorS.x;
mol_complexSP->membraneS.center_y = CA_center_vectorS.y;
mol_complexSP->membraneS.center_z = CA_center_vectorS.z;
/*------scan a number of directions in space:--------------------------------*/
/* Initialize the parameters which define a total number of directions: */
max_thetaI = 18;
max_phiI = 72;
/* Prepare the angular increments. Note that only half of the full theta */
/* angle is used: we do not distinguish two sides of the membrane here. */
theta_step = 1.5707963 / (double) max_thetaI;
phi_step = 6.2831853 / (double) max_phiI;
/* Initialize the flag which will be set to one if the */
/* best second average of hydrophobicity will be found: */
best_second_average_foundF = 0;
/* Initialize the best second average, just to avoid compiler complaints: */
best_second_average = -99999.00;
/* Initialize the best axis unit vector, for any case: */
best_unit_vectorS.x = 0.0;
best_unit_vectorS.y = 1.0;
best_unit_vectorS.z = 0.0;
/* Scan a number of directions in space. The spherical polar system is used. */
/* Theta scan: */
for (thetaI = 0; thetaI <= max_thetaI; thetaI++)
{
/* Prepare the angle theta: */
theta = (double) thetaI * theta_step;
/* Phi scan: */
for (phiI = 0; phiI <= max_phiI; phiI++)
{
/* Avoid to check too many directions close */
/* to the pole. If the theta angle is equal */
/* to zero, one phi value should be enough: */
if (thetaI == 0)
{
if (phiI != 0) continue;
}
/* If theta is too small, skip every second direction: */
if (thetaI <= 2)
{
n = phiI / 2;
if (n * 2 != phiI) continue;
}
/* Prepare the angle phi: */
phi = (double) phiI * phi_step;
/* The unit vector which defines the axis direction: */
axis_unit_vectorS.x = sin (theta) * cos (phi);
axis_unit_vectorS.y = sin (theta) * sin (phi);
axis_unit_vectorS.z = cos (theta);
/* Two additional vectors are associated with each axis: */
/* unit_vector2S and unit_vector3S. These two vectors will */
/* be used to define which cell is the first one in each */
/* ring of cells. Without these two vectors, it will be */
/* unclear to which cell the CB atom should be projected. */
/* To prepare the unit_vector2S, use the unit vector parallel */
/* to the x axis to define the plane. If it is too close to the */
/* cylinder axis use the unit vector parallel to the y axis. */
/* The first choice of auxiliary vector: */
aux_vectorS.x = 1.0;
aux_vectorS.y = 0.0;
aux_vectorS.z = 0.0;
/* Check the scalar product with the axis unit vector. Both */
/* vectors are normalized, so in the worst case the scalar */
/* product will be equal to one. A value above 0.9 is taken */
/* as a threshold to recognize the bad pair of unit vectors. */
if (ScalarProduct_ (&aux_vectorS, &axis_unit_vectorS) > 0.9)
{
/* The second choice: */
aux_vectorS.x = 0.0;
aux_vectorS.y = 1.0;
aux_vectorS.z = 0.0;
}
/* Now it is certain that axis_unit_vectorS and */
/* aux_vectorS are not parallel. Calculate and */
/* normalize the vector product of these vectors. */
VectorProduct_ (&unit_vector2S, &axis_unit_vectorS, &aux_vectorS);
abs_value = AbsoluteValue_ (&unit_vector2S);
if (abs_value == 0.0) continue; /* Yes, I am paranoic! */
reciprocal_abs_value = 1.0 / abs_value;
unit_vector2S.x *= reciprocal_abs_value;
unit_vector2S.y *= reciprocal_abs_value;
unit_vector2S.z *= reciprocal_abs_value;
/* Prepare the third unit vector. As both axis_unit_vectorS */
/* and unit_vector2S are normalized and mutually orthogonal, */
/* the vector product of these vectors will be normalized too. */
VectorProduct_ (&unit_vector3S, &axis_unit_vectorS, &unit_vector2S);
/* Reset the array of BetaCellS structures: */
for (beta_cellI = 0; beta_cellI < runtimeSP->beta_cellsN; beta_cellI++)
{
beta_cellSP = runtimeSP->beta_cellSP + beta_cellI;
beta_cellSP->cell_usedF = 0;
beta_cellSP->distance = 0.0;
beta_cellSP->hydrophobicity = 0.0;
beta_cellSP->cells_usedN = 0;
beta_cellSP->average_calculatedF = 0;
beta_cellSP->average_hydrophobicity = 0.0;
}
/*------(2) project surface CB atoms to cylinder surface:------------*/
/* Scan residues: */
for (residueI = 0; residueI < residuesN; residueI++)
{
/* Pointer to the current residue: */
residueSP = mol_complexSP->residueSP + residueI;
/* Try to extract the CA and CB coordinates: */
n = ExtractCACB_ (&CA_vectorS, &CB_vectorS,
mol_complexSP->atomSP,
residueSP->residue_startI,
residueSP->residue_endI);
if (n < 2) continue;
/* Prepare the vector from CA to CB: */
CA_CB_vectorS.x = CB_vectorS.x - CA_vectorS.x;
CA_CB_vectorS.y = CB_vectorS.y - CA_vectorS.y;
CA_CB_vectorS.z = CB_vectorS.z - CA_vectorS.z;
/* The vector from the CA geometric center */
/* to the CB atom of the current residue: */
CA_center_CB_vectorS.x = CB_vectorS.x - CA_center_vectorS.x;
CA_center_CB_vectorS.y = CB_vectorS.y - CA_center_vectorS.y;
CA_center_CB_vectorS.z = CB_vectorS.z - CA_center_vectorS.z;
/* The scalar product between this */
/* vector and the axis unit vector: */
scalar_product = ScalarProduct_ (&CA_center_CB_vectorS,
&axis_unit_vectorS);
/* The parallel component of the vector from the */
/* CA center to the CB atom of the current residue: */
parallel_vectorS.x = scalar_product * axis_unit_vectorS.x;
parallel_vectorS.y = scalar_product * axis_unit_vectorS.y;
parallel_vectorS.z = scalar_product * axis_unit_vectorS.z;
/* The perpendicular component: */
perpendicular_vectorS.x = CA_center_CB_vectorS.x -
parallel_vectorS.x;
perpendicular_vectorS.y = CA_center_CB_vectorS.y -
parallel_vectorS.y;
perpendicular_vectorS.z = CA_center_CB_vectorS.z -
parallel_vectorS.z;
/* Calculate and check the distance from the axis. */
/* Skip residues whose CB atoms are too close to */
/* the axis, they do not belong to the barrel wall. */
/* A limit of eight angstroms might be reasonable. */
distance = AbsoluteValue_ (&perpendicular_vectorS);
if (distance <= 8.0) continue;
/* Check the scalar product between the CA-CB vector and */
/* the perpendicular component of the vector from the CA */
/* center to the CB atom of the current residue. If it */
/* is negative the CA-CB vector points towards the axis. */
scalar_product = ScalarProduct_ (&CA_CB_vectorS,
&perpendicular_vectorS);
if (scalar_product < 0.0) continue;
/* If this point is reached, the CA-CB bond */
/* points outwards with respect to the axis. */
/* Project the CB coordinates to the */
/* surface of the auxiliary cylinder. */
/* To find the cell to which CB should be projected, */
/* two indices are required: axial and radial index. */
/* The parallel part of the vector from the CA center */
/* to the CB atom will be used to calculate the axial */
/* index of the cell to which the CB atom should be */
/* projected. The perpendicular component of the same */
/* vector will be used to calculate the radial index. */
/* Axial index is calculated from the projection of the */
/* parallel component of CA_center_CB_vectorS to the axis: */
scalar_product = ScalarProduct_ (¶llel_vectorS,
&axis_unit_vectorS);
axialI = (int) (recip_beta_lin_width * scalar_product) +
beta_index_offset;
/* Check the axial index, to avoid the arary overflow: */
if (axialI < 0) continue;
if (axialI >= beta_cells_along_axisN) continue;
/* The angle in radians is required to calculate the */
/* radial index. The angular range if from 0 to 2 PI. */
/* Calculate the arc cosine using the scalar product between the */
/* perpendicular component of the CA_center_CB_vectorS and the */
/* unit_vector2S. The result will be in the range from 0 to PI. */
scalar_product = ScalarProduct_ (&perpendicular_vectorS,
&unit_vector2S);
cos_angle = scalar_product / distance;
if (cos_angle <= -1.0) angle = 3.1415927;
else if (cos_angle >= 1.0) angle = 0.0;
else angle = acos (cos_angle);
/* The scalar product between the perpendicular */
/* component of the CA_center_CB_vectorS and the */
/* unit_vector3S is used to resolve the ambiguity. */
/* If it is negative, the angle should be fixed. */
scalar_product = ScalarProduct_ (&perpendicular_vectorS,
&unit_vector3S);
if (scalar_product < 0.0) angle = 6.2831853 - angle;
/* Now it is possible to calculate the radial index: */
radialI = recip_beta_ang_width * angle;
/* Check the radial index, to avoid the arary overflow: */
if (radialI < 0) continue;
if (radialI >= cells_in_ringN) continue;
/* Check the cell defined by the given pair */
/* of indices and two adjacent cells in the */
/* plane which is perpendicular to the axis. */
/* Scan the window of three cells: */
for (localI = -1; localI <= 1; localI++)
{
/* Prepare and check the combined index: */
combined_radialI = radialI + localI;
if (combined_radialI < 0)
{
combined_radialI = cells_in_ringN - 1;
}
else if (combined_radialI >= cells_in_ringN)
{
combined_radialI = 0;
}
/* Now the cell to which the CB atom should be */
/* projected is identified. Check was it used */
/* before. If not, just store the information */
/* about this CB atom. If it was used, compare */
/* the distance from the axis of this CB atom */
/* with the value which was stored before to */
/* the cell defined by the given axialI and */
/* combined_radialI. If this CB atom is not the */
/* most distant CB atom projected to this cell, */
/* ignore it. If it is, change the cell content. */
/* The index of BetaCellsS structure to */
/* which the CB atom should be projected. */
/* The array is indexed ring by ring. */
beta_cellI = axialI * cells_in_ringN + combined_radialI;
/* A true paranoic will make some extra checks: */
if (beta_cellI < 0) continue;
if (beta_cellI >= runtimeSP->beta_cellsN) continue;
/* The pointer to this BetaCellS structure: */
beta_cellSP = runtimeSP->beta_cellSP + beta_cellI;
/* If this cell was not used before, just fill it: */
if (beta_cellSP->cell_usedF == 0)
{
beta_cellSP->cell_usedF = 1;
beta_cellSP->distance = distance;
first_atomSP = mol_complexSP->atomSP +
residueSP->residue_startI;
hydrophobicity = first_atomSP->raw_atomS.hydrophobicity;
beta_cellSP->hydrophobicity = hydrophobicity;
}
/* If it was used before, compare the old and new distance: */
else
{
if (beta_cellSP->distance > distance) continue;
/* If this point is reached, the given CB atom is the */
/* most distant CB atom projected to the given cell. */
beta_cellSP->distance = distance;
first_atomSP = mol_complexSP->atomSP +
residueSP->residue_startI;
hydrophobicity = first_atomSP->raw_atomS.hydrophobicity;
beta_cellSP->hydrophobicity = hydrophobicity;
}
/* End of localI loop: */
}
/* End of residueI loop: */
}
/*------(3) calculate average hydrophob. (axial scan):---------------*/
/* Now comes the averaging. */
/* Scan the cylinder surface, stripe by stripe. All stripes are */
/* parallel to the axis. The sliding window width (used to calculate */
/* the average hydrophobicity with a given residue in the center) */
/* is set to cover the entire membrane thickness (but no more than */
/* that). For example, if membrane thickness is 30 angstroms the */
/* window width will be about 10, because in axis direction one cell */
/* covers 3 angstroms. Odd number is recommended, so the final width */
/* is 9. If 11 cells were used hydrophilic residues may be reached. */
/* The outermost loop scans the surface, stripe by stripe: */
for (radialI = 0; radialI < cells_in_ringN; radialI++)
{
/* The next loop scans the given stripe, cell by cell. The cells */
/* which are too close to either top or bottom edge are skipped. */
for (axialI = 0; axialI < beta_cells_along_axisN; axialI++)
{
if (axialI < half_window_width) continue;
if (axialI + half_window_width >= beta_cells_along_axisN)
{
continue;
}
/* Reset the number of useful cells in the sliding window: */
cells_usedN = 0;
/* Reset the average hydrophobicity: */
average_hydrophobicity = 0.0;
/* Somewhere above the flag average_calculatedF */
/* was cleared (set to zero) for all cells. It */
/* is not necessary to clear these flags again. */
/* The innermost loop scans the sliding */
/* window centered at the given cell: */
for (windowI = 0; windowI < window_width; windowI++)
{
/* Prepare the combined axial index: */
combined_axialI = axialI + windowI - half_window_width;
/* The cell array index: */
beta_cellI = combined_axialI * cells_in_ringN + radialI;
/* Pointer to the current cell: */
beta_cellSP = runtimeSP->beta_cellSP + beta_cellI;
/* If this cell was unused, skip it: */
if (beta_cellSP->cell_usedF == 0) continue;
/* If this point is reached, this cell is useful. */
/* Add the hydrophobicity of this cell to the total: */
average_hydrophobicity += beta_cellSP->hydrophobicity;
/* Update the counter: */
cells_usedN++;
}
/* If there were too many unused cells in this sliding */
/* window, the cell in the center of this sliding window */
/* should be treated as useless. The cell will be treated */
/* as useful if at least half_window_width + 1 cells in */
/* the sliding window associated with this cell were used. */
if (cells_usedN < half_window_width + 1) continue;
/* Divide the total hydrophobicity by the number of cells: */
average_hydrophobicity /= (double) cells_usedN;
/* Store the average hydrophobicity and the number */
/* of used cells and set the flag which says that */
/* average hydrophob. was successfully calculated. */
/* Store it to the cell which was in the middle */
/* of the sliding window which was just scanned. */
beta_cellI = axialI * cells_in_ringN + radialI;
beta_cellSP = runtimeSP->beta_cellSP + beta_cellI;
beta_cellSP->average_hydrophobicity = average_hydrophobicity;
beta_cellSP->cells_usedN = cells_usedN;
beta_cellSP->average_calculatedF = 1;
}
}
/*------(4) calculate average hydrophob. (radial scan):--------------*/
/* The outermost loop scans the surface, ring by ring: */
for (axialI = 0; axialI < beta_cells_along_axisN; axialI++)
{
/* Reset the number of useful cells in the ring: */
cells_usedN = 0;
/* Reset the second average of hydrophobicity: */
second_average = 0.0;
/* The next loop scans the entire ring at the */
/* given height defined by axialI, cell by cell: */
for (radialI = 0; radialI < cells_in_ringN; radialI++)
{
/* The cell array index: */
beta_cellI = axialI * cells_in_ringN + radialI;
/* Pointer to this cell: */
beta_cellSP = runtimeSP->beta_cellSP + beta_cellI;
/* If the average hydrophobicity is not */
/* available for this cell, skip it: */
if (beta_cellSP->average_calculatedF == 0) continue;
/* If this point is reached, this cell is useful. */
/* Add the hydrophobicity of this cell to the total: */
second_average += beta_cellSP->average_hydrophobicity;
/* Update the counter: */
cells_usedN++;
}
/* At least half of the cells in this ring should be */
/* useful, otherwise the second average is useless: */
if (cells_usedN < half_cells_in_ringN) continue;
/* Divide the total by the number of cells: */
second_average /= (double) cells_usedN;
/* If this is the first second average at all, just copy it: */
if (best_second_average_foundF == 0)
{
best_second_average = second_average;
best_second_average_foundF = 1;
best_unit_vectorS.x = axis_unit_vectorS.x;
best_unit_vectorS.y = axis_unit_vectorS.y;
best_unit_vectorS.z = axis_unit_vectorS.z;
continue;
}
/*------(5) check is it the most hydrophobic ring:---------------*/
/* Now check is there any chance that this value is the */
/* highest value of the second average up to now. If it */
/* is, update the best value and store theta and phi: */
if (second_average > best_second_average)
{
best_second_average = second_average;
best_second_average_foundF = 1;
best_unit_vectorS.x = axis_unit_vectorS.x;
best_unit_vectorS.y = axis_unit_vectorS.y;
best_unit_vectorS.z = axis_unit_vectorS.z;
}
}
/* End of phiI loop: */
}
/* End of thetaI loop: */
}
/*------store the normal vector (raw):---------------------------------------*/
/* Store (copy) the components of the normal */
/* vector because the refinement may fail. */
/* The normal vector of the first plane points to the same direction: */
mol_complexSP->membraneS.plane1S.normal_x[0] = best_unit_vectorS.x;
mol_complexSP->membraneS.plane1S.normal_y = best_unit_vectorS.y;
mol_complexSP->membraneS.plane1S.normal_z[0] = best_unit_vectorS.z;
/* The normal vector of the second plane points to the opposite direction: */
mol_complexSP->membraneS.plane2S.normal_x[0] = -best_unit_vectorS.x;
mol_complexSP->membraneS.plane2S.normal_y = -best_unit_vectorS.y;
mol_complexSP->membraneS.plane2S.normal_z[0] = -best_unit_vectorS.z;
/*------prepare stereo data (raw):-------------------------------------------*/
/* Prepare the stereo data for both normal vectors. */
/* This is useful because the refinement may fail. */
/* Prepare the sine and cosine of the stereo angle: */
sin_angle = sin (configSP->stereo_angle);
cos_angle = cos (configSP->stereo_angle);
/* Calculate the stereo data: */
mol_complexSP->membraneS.plane1S.normal_x[1] =
mol_complexSP->membraneS.plane1S.normal_x[0] * cos_angle +
mol_complexSP->membraneS.plane1S.normal_z[0] * sin_angle;
mol_complexSP->membraneS.plane1S.normal_z[1] =
-mol_complexSP->membraneS.plane1S.normal_x[0] * sin_angle +
mol_complexSP->membraneS.plane1S.normal_z[0] * cos_angle;
mol_complexSP->membraneS.plane2S.normal_x[1] =
mol_complexSP->membraneS.plane2S.normal_x[0] * cos_angle +
mol_complexSP->membraneS.plane2S.normal_z[0] * sin_angle;
mol_complexSP->membraneS.plane2S.normal_z[1] =
-mol_complexSP->membraneS.plane2S.normal_x[0] * sin_angle +
mol_complexSP->membraneS.plane2S.normal_z[0] * cos_angle;
/*------(6) search two rings of PHE, TRP and TYR:----------------------------*/
/* In this procedure, a new coordinate system will be used. Three axes */
/* of this system are defined by i1_unit_vectorS, j1_unit_vectorS and */
/* k1_unit_vectorS. The best unit vector found in the procedure above will */
/* be used to define the z axis, i.e. it will be used as k1_unit_vectorS. */
/* Prepare the unit vector which define the z axis of a new system: */
k1_unit_vectorS.x = best_unit_vectorS.x;
k1_unit_vectorS.y = best_unit_vectorS.y;
k1_unit_vectorS.z = best_unit_vectorS.z;
/* To prepare the unit vector which defines the y axis of a new */
/* system, use the unit vector parallel to the x axis of the main */
/* coordinate system to define the plane. If it is too close to new */
/* z axis use the unit vector parallel to y axis of the main system. */
/* The first choice of auxiliary vector: */
aux_vectorS.x = 1.0;
aux_vectorS.y = 0.0;
aux_vectorS.z = 0.0;
/* Check the scalar product with k1_unit_vectorS. Both these */
/* vectors are normalized, so in the worst case the scalar */
/* product will be equal to one. A value above 0.9 is taken */
/* as a threshold to recognize the bad pair of unit vectors. */
if (ScalarProduct_ (&aux_vectorS, &k1_unit_vectorS) > 0.9)
{
/* The second choice: */
aux_vectorS.x = 0.0;
aux_vectorS.y = 1.0;
aux_vectorS.z = 0.0;
}
/* Now it is certain that k1_unit_vectorS and aux_vectorS are */
/* not parallel. Calculate and normalize the vector product. */
VectorProduct_ (&j1_unit_vectorS, &k1_unit_vectorS, &aux_vectorS);
abs_value = AbsoluteValue_ (&j1_unit_vectorS);
if (abs_value == 0.0) return -5; /* Yes, I am paranoic! */
reciprocal_abs_value = 1.0 / abs_value;
j1_unit_vectorS.x *= reciprocal_abs_value;
j1_unit_vectorS.y *= reciprocal_abs_value;
j1_unit_vectorS.z *= reciprocal_abs_value;
/* The third unit vector, parallel to x axis of a new system: */
VectorProduct_ (&i1_unit_vectorS, &j1_unit_vectorS, &k1_unit_vectorS);
/* Initialize the total number of PHE, TRP and */
/* TYR residues in this macromolecular complex. */
total_phe_trp_tyrN = 0;
/* Scan the macromolecular complex, residue by residue. For each */
/* residue, check is it PHE, TRP or TYR. If it is, set auxiliaryI */
/* of the first atom to one. If not, set the auxiliaryI to zero. */
for (residueI = 0; residueI < residuesN; residueI++)
{
/* Pointer to the current residue: */
residueSP = mol_complexSP->residueSP + residueI;
/* Pointer to the first atom: */
first_atomSP = mol_complexSP->atomSP + residueSP->residue_startI;
/* The purified residue name (without spaces): */
pure_residue_nameP = first_atomSP->raw_atomS.pure_residue_nameA;
/* Check the purified residue name: */
if (strcmp (pure_residue_nameP, "PHE") == 0)
{
first_atomSP->auxiliaryI = 1;
total_phe_trp_tyrN++;
}
else if (strcmp (pure_residue_nameP, "TRP") == 0)
{
first_atomSP->auxiliaryI = 2;
total_phe_trp_tyrN++;
}
else if (strcmp (pure_residue_nameP, "TYR") == 0)
{
first_atomSP->auxiliaryI = 3;
total_phe_trp_tyrN++;
}
else first_atomSP->auxiliaryI = 0;
}
if (total_phe_trp_tyrN <= 1) return -6;
/* Scan a cone about the k1_unit_vectorS. */
/* The spherical polar system is used. */
/* Initialize the parameters which define a total number of directions: */
max_thetaI = 30;
max_phiI = 72;
/* Prepare the angular increments. The maximal allowed */
/* deviation from the initial vector is 45 degrees. */
theta_step = 0.7853982 / (double) max_thetaI;
phi_step = 6.2831853 / (double) max_phiI;
/* Reset the highest number of PHE, TRP */
/* and TYR residues in two selected rings: */
best_two_rings_count = 0;
/* Theta scan: */
for (thetaI = 0; thetaI <= max_thetaI; thetaI++)
{
/* Prepare the angle theta: */
theta = (double) thetaI * theta_step;
/* Phi scan: */
for (phiI = 0; phiI <= max_phiI; phiI++)
{
/* Avoid to check too many directions close */
/* to the pole. If the theta angle is equal */
/* to zero, one phi value should be enough: */
if (thetaI == 0)
{
if (phiI != 0) continue;
}
/* If theta is too small, skip every second direction: */
if (thetaI <= 2)
{
n = phiI / 2;
if (n * 2 != phiI) continue;
}
/* Prepare the angle phi: */
phi = (double) phiI * phi_step;
/* The unit vector which defines the axis direction: */
cos_theta = cos (theta);
sin_theta = sin (theta);
cos_phi = cos (phi);
sin_phi = sin (phi);
axis_unit_vectorS.x = sin_theta * cos_phi * i1_unit_vectorS.x +
sin_theta * sin_phi * j1_unit_vectorS.x +
cos_theta * k1_unit_vectorS.x;
axis_unit_vectorS.y = sin_theta * cos_phi * i1_unit_vectorS.y +
sin_theta * sin_phi * j1_unit_vectorS.y +
cos_theta * k1_unit_vectorS.y;
axis_unit_vectorS.z = sin_theta * cos_phi * i1_unit_vectorS.z +
sin_theta * sin_phi * j1_unit_vectorS.z +
cos_theta * k1_unit_vectorS.z;
/* Reset the array which counts PHE, TRP */
/* and TYR residues projected to the axis: */
for (simpleI = 0; simpleI < simple_cells_along_axisN; simpleI++)
{
phe_trp_tyrNA[simpleI] = 0;
}
/* Scan residues: */
for (residueI = 0; residueI < residuesN; residueI++)
{
/* Pointer to the current residue: */
residueSP = mol_complexSP->residueSP + residueI;
/* Pointer to the first atom of this residue: */
first_atomSP = mol_complexSP->atomSP + residueSP->residue_startI;
/* Check the auxiliaryI of the first atom; if */
/* it is equal to zero, ignore this residue. */
if (first_atomSP->auxiliaryI == 0) continue;
/* Try to extract the CA and CB coordinates: */
n = ExtractCACB_ (&CA_vectorS, &CB_vectorS,
mol_complexSP->atomSP,
residueSP->residue_startI,
residueSP->residue_endI);
if (n < 2) continue;
/* Prepare the vector from CA to CB: */
CA_CB_vectorS.x = CB_vectorS.x - CA_vectorS.x;
CA_CB_vectorS.y = CB_vectorS.y - CA_vectorS.y;
CA_CB_vectorS.z = CB_vectorS.z - CA_vectorS.z;
/* The vector from the CA geometric center */
/* to the CB atom of the current residue: */
CA_center_CB_vectorS.x = CB_vectorS.x - CA_center_vectorS.x;
CA_center_CB_vectorS.y = CB_vectorS.y - CA_center_vectorS.y;
CA_center_CB_vectorS.z = CB_vectorS.z - CA_center_vectorS.z;
/* The scalar product between this */
/* vector and the axis unit vector: */
scalar_product = ScalarProduct_ (&CA_center_CB_vectorS,
&axis_unit_vectorS);
/* The parallel component of the vector from the */
/* CA center to the CB atom of the current residue: */
parallel_vectorS.x = scalar_product * axis_unit_vectorS.x;
parallel_vectorS.y = scalar_product * axis_unit_vectorS.y;
parallel_vectorS.z = scalar_product * axis_unit_vectorS.z;
/* The perpendicular component: */
perpendicular_vectorS.x = CA_center_CB_vectorS.x -
parallel_vectorS.x;
perpendicular_vectorS.y = CA_center_CB_vectorS.y -
parallel_vectorS.y;
perpendicular_vectorS.z = CA_center_CB_vectorS.z -
parallel_vectorS.z;
/* Calculate and check the distance from the axis. */
/* Skip residues whose CB atoms are too close to */
/* the axis, they do not belong to the barrel wall. */
/* A limit of eleven angstroms might be reasonable. */
distance = AbsoluteValue_ (&perpendicular_vectorS);
if (distance <= 11.0) continue;
/* Check the scalar product between the CA-CB vector and */
/* the perpendicular component of the vector from the CA */
/* center to the CB atom of the current residue. If it */
/* is negative the CA-CB vector points towards the axis. */
scalar_product = ScalarProduct_ (&CA_CB_vectorS,
&perpendicular_vectorS);
if (scalar_product < 0.0) continue;
/* If this point is reached, the CA-CB bond */
/* points outwards with respect to the axis. */
/* Extract the coordinates of the CG atom: */
n = ExtractCG_ (&CG_vectorS,
mol_complexSP->atomSP,
residueSP->residue_startI,
residueSP->residue_endI);
if (n < 1) continue;
/* The CG atom will be projected over a number of cells. */
/* The index of the central cell will be calculated from */
/* parallel part of the vector from CA center to CG atom. */
/* The vector from the CA geometric center */
/* to the CG atom of the current residue: */
CA_center_CG_vectorS.x = CG_vectorS.x - CA_center_vectorS.x;
CA_center_CG_vectorS.y = CG_vectorS.y - CA_center_vectorS.y;
CA_center_CG_vectorS.z = CG_vectorS.z - CA_center_vectorS.z;
/* The scalar product between this */
/* vector and the axis unit vector: */
scalar_product = ScalarProduct_ (&CA_center_CG_vectorS,
&axis_unit_vectorS);
/* The parallel component of the vector from the */
/* CA center to the CG atom of the current residue: */
parallel_vectorS.x = scalar_product * axis_unit_vectorS.x;
parallel_vectorS.y = scalar_product * axis_unit_vectorS.y;
parallel_vectorS.z = scalar_product * axis_unit_vectorS.z;
/* The index of central simple cell is calculated */
/* from the projection of the parallel component of */
/* CA_center_CB_vectorS to the axis_unit_vectorS: */
scalar_product = ScalarProduct_ (¶llel_vectorS,
&axis_unit_vectorS);
central_simpleI = (int) (recip_simple_width * scalar_product) +
simple_index_offset;
/* The CG atom will be projected over a number of cells. */
/* The side chains which form the ring of aromatic */
/* residues are not perfectly aligned and for that */
/* reason the CG atom will be smeared over more cells. */
/* This should improve recognition of aromatic rings. */
start_simpleI = central_simpleI - half_simple_window_width;
end_simpleI = start_simpleI + simple_window_width;
/* Smear CG projection over a number of cells: */
for (simpleI = start_simpleI; simpleI <= end_simpleI; simpleI++)
{
/* Do not allow array overflow: */
if (simpleI < 0) continue;
if (simpleI >= simple_cells_along_axisN) break;
/* Update the number of PHE, TRP and TYR residues which */
/* were projected to the cell defined by this simpleI: */
phe_trp_tyrNA[simpleI]++;
}
/* End of residueI loop: */
}
/* For this orientation, check the total number of PHE, TRP and TYR */
/* residues in two rings separated by the given membrane thickness. */
for (simpleI = 0; simpleI < max_simpleI; simpleI++)
{
two_rings_count = phe_trp_tyrNA[simpleI] +
phe_trp_tyrNA[simpleI + simple_thickness];
if (two_rings_count > best_two_rings_count)
{
best_two_rings_count = two_rings_count;
best_unit_vectorS.x = axis_unit_vectorS.x;
best_unit_vectorS.y = axis_unit_vectorS.y;
best_unit_vectorS.z = axis_unit_vectorS.z;
}
}
/* End of phiI loop: */
}
/* End of thetaI loop: */
}
/*------store the normal vector (refined):-----------------------------------*/
/* Store (copy) the components of the normal vector. */
/* The normal vector of the first plane points to the same direction: */
mol_complexSP->membraneS.plane1S.normal_x[0] = best_unit_vectorS.x;
mol_complexSP->membraneS.plane1S.normal_y = best_unit_vectorS.y;
mol_complexSP->membraneS.plane1S.normal_z[0] = best_unit_vectorS.z;
/* The normal vector of the second plane points to the opposite direction: */
mol_complexSP->membraneS.plane2S.normal_x[0] = -best_unit_vectorS.x;
mol_complexSP->membraneS.plane2S.normal_y = -best_unit_vectorS.y;
mol_complexSP->membraneS.plane2S.normal_z[0] = -best_unit_vectorS.z;
/*------prepare stereo data (refined):---------------------------------------*/
/* Prepare the stereo data for both normal vectors. */
/* Prepare the sine and cosine of the stereo angle: */
sin_angle = sin (configSP->stereo_angle);
cos_angle = cos (configSP->stereo_angle);
/* Calculate the stereo data: */
mol_complexSP->membraneS.plane1S.normal_x[1] =
mol_complexSP->membraneS.plane1S.normal_x[0] * cos_angle +
mol_complexSP->membraneS.plane1S.normal_z[0] * sin_angle;
mol_complexSP->membraneS.plane1S.normal_z[1] =
-mol_complexSP->membraneS.plane1S.normal_x[0] * sin_angle +
mol_complexSP->membraneS.plane1S.normal_z[0] * cos_angle;
mol_complexSP->membraneS.plane2S.normal_x[1] =
mol_complexSP->membraneS.plane2S.normal_x[0] * cos_angle +
mol_complexSP->membraneS.plane2S.normal_z[0] * sin_angle;
mol_complexSP->membraneS.plane2S.normal_z[1] =
-mol_complexSP->membraneS.plane2S.normal_x[0] * sin_angle +
mol_complexSP->membraneS.plane2S.normal_z[0] * cos_angle;
/*------update auxiliaryI:---------------------------------------------------*/
/* In this section, the auxiliaryI for PHE, TRP and TYR will */
/* be set to zero for side chains which are pointing inwards. */
/* This should improve performance: the axis orientation during */
/* the membrane center refinement is not subject to change. */
for (residueI = 0; residueI < residuesN; residueI++)
{
/* Pointer to the current residue: */
residueSP = mol_complexSP->residueSP + residueI;
/* Pointer to the first atom of this residue: */
first_atomSP = mol_complexSP->atomSP + residueSP->residue_startI;
/* Check the auxiliaryI of the first atom; if */
/* it is equal to zero, ignore this residue. */
if (first_atomSP->auxiliaryI == 0) continue;
/* Try to extract the CA and CB coordinates: */
n = ExtractCACB_ (&CA_vectorS, &CB_vectorS,
mol_complexSP->atomSP,
residueSP->residue_startI,
residueSP->residue_endI);
if (n < 2) continue;
/* Prepare the vector from CA to CB: */
CA_CB_vectorS.x = CB_vectorS.x - CA_vectorS.x;
CA_CB_vectorS.y = CB_vectorS.y - CA_vectorS.y;
CA_CB_vectorS.z = CB_vectorS.z - CA_vectorS.z;
/* The vector from the CA geometric center */
/* to the CB atom of the current residue: */
CA_center_CB_vectorS.x = CB_vectorS.x - CA_center_vectorS.x;
CA_center_CB_vectorS.y = CB_vectorS.y - CA_center_vectorS.y;
CA_center_CB_vectorS.z = CB_vectorS.z - CA_center_vectorS.z;
/* The scalar product between this */
/* vector and the axis unit vector: */
scalar_product = ScalarProduct_ (&CA_center_CB_vectorS,
&axis_unit_vectorS);
/* The parallel component of the vector from the */
/* CA center to the CB atom of the current residue: */
parallel_vectorS.x = scalar_product * axis_unit_vectorS.x;
parallel_vectorS.y = scalar_product * axis_unit_vectorS.y;
parallel_vectorS.z = scalar_product * axis_unit_vectorS.z;
/* The perpendicular component: */
perpendicular_vectorS.x = CA_center_CB_vectorS.x - parallel_vectorS.x;
perpendicular_vectorS.y = CA_center_CB_vectorS.y - parallel_vectorS.y;
perpendicular_vectorS.z = CA_center_CB_vectorS.z - parallel_vectorS.z;
/* Calculate and check the distance from the axis. */
/* Skip residues whose CB atoms are too close to */
/* the axis, they do not belong to the barrel wall. */
/* A limit of eleven angstroms might be reasonable. */
distance = AbsoluteValue_ (&perpendicular_vectorS);
if (distance <= 11.0) continue;
/* Check the scalar product between the CA-CB vector and */
/* the perpendicular component of the vector from the CA */
/* center to the CB atom of the current residue. If it */
/* is negative the CA-CB vector points towards the axis. */
scalar_product = ScalarProduct_ (&CA_CB_vectorS, &perpendicular_vectorS);
if (scalar_product < 0.0) first_atomSP->auxiliaryI = 0;
}
/*------(7) refine the membrane center:--------------------------------------*/
/* Initialize the best shift: */
best_shift = 0.0;
/* Reset the highest number of PHE, TRP */
/* and TYR residues in two selected rings: */
best_two_rings_count = 0;
/* Scan a number of positions along the refined axis. The old CA */
/* center should fall in the middle of the array of simple cells. */
start_pointI = -simple_scan_half_width;
end_pointI = simple_scan_half_width;
for (pointI = start_pointI; pointI <= end_pointI; pointI++)
{
/* Shift, in angstroms: */
shift = (double) pointI * simple_cell_width;
/* Presumed membrane center position: */
center_vectorS.x = CA_center_vectorS.x + shift * best_unit_vectorS.x;
center_vectorS.y = CA_center_vectorS.y + shift * best_unit_vectorS.y;
center_vectorS.z = CA_center_vectorS.z + shift * best_unit_vectorS.z;
/* Reset the array which counts PHE, TRP */
/* and TYR residues projected to the axis: */
for (simpleI = 0; simpleI < simple_cells_along_axisN; simpleI++)
{
phe_trp_tyrNA[simpleI] = 0;
}
/* Scan the macromolecular complex, residue by residue: */
for (residueI = 0; residueI < residuesN; residueI++)
{
/* Pointer to the current residue: */
residueSP = mol_complexSP->residueSP + residueI;
/* Pointer to the first atom of this residue: */
first_atomSP = mol_complexSP->atomSP + residueSP->residue_startI;
/* Check the auxiliaryI of the first atom; if */
/* it is equal to zero, ignore this residue. It */
/* is either of wrong type or points inwards. */
if (first_atomSP->auxiliaryI == 0) continue;
/* Extract the coordinates of the CG atom: */
n = ExtractCG_ (&CG_vectorS, mol_complexSP->atomSP,
residueSP->residue_startI, residueSP->residue_endI);
if (n < 1) continue;
/* The parallel part of the vector from the presumed membrane */
/* center to the CG atom will be used to calculate the index */
/* of the cell to which the CG atom should be projected. */
/* The vector from the current center to */
/* the CG atom of the current residue: */
radius_vectorS.x = CG_vectorS.x - center_vectorS.x;
radius_vectorS.y = CG_vectorS.y - center_vectorS.y;
radius_vectorS.z = CG_vectorS.z - center_vectorS.z;
/* Projection of this vector to the axis: */
projection = ScalarProduct_ (&radius_vectorS, &best_unit_vectorS);
/* The index of the central simple cell: */
central_simpleI = (int) (recip_simple_width * projection) +
simple_index_offset;
/* The CG atom will be projected over a number of cells. */
/* The side chains which form the ring of aromatic */
/* residues are not perfectly aligned and for that */
/* reason the CG atom will be smeared over more cells. */
start_simpleI = central_simpleI - half_simple_window_width;
end_simpleI = start_simpleI + simple_window_width;
/* Smear CG projection over a number of cells: */
for (simpleI = start_simpleI; simpleI <= end_simpleI; simpleI++)
{
/* Do not allow array overflow: */
if (simpleI < 0) continue;
if (simpleI >= simple_cells_along_axisN) break;
/* Update the number of PHE, TRP and TYR residues which */
/* were projected to the cell defined by this simpleI: */
phe_trp_tyrNA[simpleI]++;
}
/* End of residueI loop: */
}
/* Check the count of PHE, TRP and TYR residues in two rings: */
ring1I = simple_index_offset - half_simple_thickness;
if (ring1I < 0) continue;
if (ring1I >= simple_cells_along_axisN) continue;
ring2I = ring1I + simple_thickness;
if (ring2I < 0) continue;
if (ring2I >= simple_cells_along_axisN) continue;
two_rings_count = phe_trp_tyrNA[ring1I] + phe_trp_tyrNA[ring2I];
if (two_rings_count > best_two_rings_count)
{
best_two_rings_count = two_rings_count;
best_shift = shift;
}
/* End of pointI loop: */
}
/*------update the membrane center:------------------------------------------*/
/* Update the membrane center: */
/* Update the membrane center: */
mol_complexSP->membraneS.center_x = CA_center_vectorS.x +
best_shift * best_unit_vectorS.x;
mol_complexSP->membraneS.center_y = CA_center_vectorS.y +
best_shift * best_unit_vectorS.y;
mol_complexSP->membraneS.center_z = CA_center_vectorS.z +
best_shift * best_unit_vectorS.z;
/*---------------------------------------------------------------------------*/
/* Return positive value on success: */
return 1;
}
/*===========================================================================*/
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