73 lines
1.9 KiB
C
73 lines
1.9 KiB
C
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#include "stride.h"
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/*************************************************
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Calculate the hydrogen bond energy as defined by
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Boobbyer et al., 1989
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**************************************************/
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void GRID_Energy(float *CA2, float *C, float *O, float *H, float *N, COMMAND *Cmd, HBOND *HBond)
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{
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float ProjH[3];
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/***** Distance dependence ( 8-6 potential ) ****/
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if( Cmd->Truncate && HBond->AccDonDist < RmGRID )
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HBond->AccDonDist = RmGRID;
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HBond->Er = CGRID/pow(HBond->AccDonDist,8.0) - DGRID/pow(HBond->AccDonDist,6.0);
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/************** Angular dependance ****************/
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/* Find projection of the hydrogen on the O-C-CA plane */
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Project4_123(O,C,CA2,H,ProjH);
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/* Three angles determining the direction of the hydrogen bond */
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HBond->ti = fabs(180.0 - Ang(ProjH,O,C));
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HBond->to = Ang(H,O,ProjH);
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HBond->p = Ang(N,H,O);
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/* Calculate both angle-dependent HB energy components Et and Ep */
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if( HBond->ti >= 0.0 && HBond->ti < 90.0 )
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HBond->Et = cos(RAD(HBond->to))*(0.9+0.1*sin(RAD(2*HBond->ti)));
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else
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if( HBond->ti >= 90.0 && HBond->ti < 110.0 )
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HBond->Et = K1GRID*cos(RAD(HBond->to))*
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(pow((K2GRID-pow(cos(RAD(HBond->ti)),2.0)),3.0));
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else
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HBond->Et = 0.0;
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if( HBond->p > 90.0 && HBond->p < 270.0 )
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HBond->Ep = pow(cos(RAD(HBond->p)),2.0);
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else
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HBond->Ep = 0.0;
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/******** Full hydrogen bond energy *********************/
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HBond->Energy = 1000.0*HBond->Er*HBond->Et*HBond->Ep;
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}
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#define Q -27888.0
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/********************************************************
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Calculate the energy of polar interaction as defined by
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Kabsch and Sander (1983)
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*********************************************************/
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void DSSP_Energy(float *Dummy, float *C, float *O, float *H, float *N, COMMAND *Cmd,
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HBOND *HBond)
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/* Dummy not used, for compatibility with GRID_Energy */
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{ HBond->Energy = Q/Dist(O,H) + Q/Dist(C,N) - Q/HBond->AccDonDist - Q/Dist(C,H); }
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