CalcCterCoords.c

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/************************************************************************/
/**

   \file       CalcCterCoords.c
   
   \version    V1.4
   \date       07.07.14
   \brief      Calculates C-terminal oxygen coordinates.
   
   \copyright  (c) UCL / Dr. Andrew C. R. Martin 1994-6
   \author     Dr. Andrew C. R. Martin
   \par
               Institute of Structural & Molecular Biology,
               University College London,
               Gower Street,
               London.
               WC1E 6BT.
   \par
               andrew@bioinf.org.uk
               andrew.martin@ucl.ac.uk
               
**************************************************************************

   This code is NOT IN THE PUBLIC DOMAIN, but it may be copied
   according to the conditions laid out in the accompanying file
   COPYING.DOC.

   The code may be modified as required, but any modifications must be
   documented so that the person responsible can be identified.

   The code may not be sold commercially or included as part of a 
   commercial product except as described in the file COPYING.DOC.

**************************************************************************

   Description:
   ============


**************************************************************************

   Usage:
   ======

   BOOL CalcCterCoords(PDB *p, PDB *ca_p, PDB *c_p, PDB *o_p)

   Calculates the coordinates for a second oxygen (p) given the
   3 antecedent atoms. Normally called from FixCterPDB()

**************************************************************************

   Revision History:
   =================
-  V1.0  24.08.94 Original    By: ACRM
-  V1.1  05.10.94 Removed unused variables
-  V1.2  12.11.96 If any of the antecedant coordinates are undefined, set
                  the terminal oxygen to NULL coordinates
-  V1.3  13.11.96 Also checks for missing CA,C and O1 records
-  V1.4  07.07.14 Use bl prefix for functions By: CTP

*************************************************************************/
/* Doxygen
   -------
   #GROUP    Handling PDB Data
   #SUBGROUP Calculations
   #FUNCTION  blCalcCterCoords()
   Calculates CTER OT2 coordinates
*/
/************************************************************************/
/* Includes
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#include "SysDefs.h"
#include "MathType.h"
#include "pdb.h"
#include "macros.h"

/************************************************************************/
/* Defines and macros
*/
#define MAXBUFF      160

/************************************************************************/
/* Globals
*/

/************************************************************************/
/* Prototypes
*/

/************************************************************************/
/*>BOOL blCalcCterCoords(PDB *p, PDB *ca_p, PDB *c_p, PDB *o_p)
   ------------------------------------------------------------
*//**

   \param[in,out] *p     OT2 PDB record whose coords are to be fixed
   \param[in]     *ca_p  Antecedent CA PDB pointer
   \param[in]     *c_p   Antecedent C PDB pointer
   \param[in]     *o_p   Antecedent O PDB pointer
   \return                Success

   Calculates the CTER OT2 coords

-  15.07.90 Original
-  07.07.14 Use bl prefix for functions By: CTP
-  26.08.14 Removed unused d23  By: ACRM
*/
BOOL blCalcCterCoords(PDB *p, PDB *ca_p, PDB *c_p, PDB *o_p)
{
   REAL  gr    = 1.3,
         alpha = 120.0*PI/180.0,
         cosa,  sina,  scalpr,
         x21,   y21,   z21,   d21,
         x23,   y23,   z23,
         x32,   y32,   z32,
         xp23,  yp23,  zp23,  rp23,
         xh,    yh,    zh,
         xp,    yp,    zp,
         xv,    yv,    zv;
         
   if(ca_p==NULL || c_p==NULL || o_p==NULL)
   {
      return(FALSE);
   }
   
   x21 = c_p->x - ca_p->x;
   y21 = c_p->y - ca_p->y;
   z21 = c_p->z - ca_p->z;
   d21 = (REAL)sqrt((double)(x21*x21 + y21*y21 + z21*z21));
   
   x23 = c_p->x - o_p->x;
   y23 = c_p->y - o_p->y;
   z23 = c_p->z - o_p->z;

   cosa = (REAL)cos((double)alpha);
   sina = (REAL)sin((double)alpha);

   x32 = o_p->x - c_p->x;
   y32 = o_p->y - c_p->y;
   z32 = o_p->z - c_p->z;

   scalpr = (x21*x32 + y21*y32 + z21*z32)/d21;
   xh = x21 / d21;
   yh = y21 / d21;
   zh = z21 / d21;

   xp = scalpr * xh;
   yp = scalpr * yh;
   zp = scalpr * zh;

   xp23 = xp + x23;
   yp23 = yp + y23;
   zp23 = zp + z23;

   rp23 = (REAL)sqrt((double)(xp23*xp23 + yp23*yp23 + zp23*zp23));
   xv = xp23/rp23;
   yv = yp23/rp23;
   zv = zp23/rp23;

   p->x = c_p->x + gr*(-cosa*xh + sina*xv);
   p->y = c_p->y + gr*(-cosa*yh + sina*yv);
   p->z = c_p->z + gr*(-cosa*zh + sina*zv);
   
   return(TRUE);
}