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C === RIBBON ===
C (extracted from frodo.tlb in CCP program package)
C
SUBROUTINE RIBBON(NRIB,RIBWID,NCHORD,OFFSET,NATOM)
C ==================================================
C
C Generate guide points for protein ribbon, based on ideas on
C Carson & Bugg, J.Molec.Graphics 4,121-122 (1986)
C
C Guide points for Bspline are generated along a line passing
C through each CA and along the average of the two peptide planes
C
C NRIB number of strands in ribbon (maximum=MAXRIB=15)
C RIBWID total ribbon width
C NCHORD number of chords/residue
C OFFSET amount to offset guide points away from CA positions
C NATOM number of atoms stored in arrays
C
PARAMETER (MAXRIB=5,MAXRES=1500)
PARAMETER (NOISE=0)
DIMENSION GUIDE(4,MAXRES,MAXRIB)
DIMENSION XCA(3,2),XO(3,2),A(3),B(3),C(3),D(3),E(3),F(3),
. G(3),H(3),P(3)
C
C Maximum CA-CA distance **2
PARAMETER (DISMAX=6.**2)
C
IF(NATOM.LE.0) THEN
WRITE(NOISE,1005)
1005 FORMAT(' No atoms selected')
RETURN
ENDIF
C
IF(NRIB.GT.MAXRIB) THEN
WRITE(NOISE,1001) NRIB,MAXRIB
1001 FORMAT(' Too many ribbon strands',I6,' reset to ',I6)
NRIB=MAXRIB
ENDIF
C
WRITE(NOISE,1002) NRIB,RIBWID,NCHORD,OFFSET
1002 FORMAT(' Ribbon drawn with',I4,' strands, width ',F6.2,
. 'A'/' Number of chords =',I3,', offset = ',F6.2,'A')
C
C Strand separation
DRIB=0.
IF(NRIB.GT.1) DRIB=RIBWID/(NRIB-1)
RIB2=FLOAT(NRIB+1)/2.
C
NAT=1
C
C Get first CA and O
1 CALL GETCAO(XCA(1,1),XO(1,1),NAT,NATOM,IERR)
CEAM IF(NAT.LE.0) RETURN
CEAM IF(IERR.NE.0) GO TO 1
IF(IERR.NE.0) RETURN
I=0
C
C Loop for residues
10 I=I+1
C Get CA and O for residue I+1
CALL GETCAO(XCA(1,2),XO(1,2),NAT,NATOM,IERR)
C Set LEND = 1 for end of chain under 3 conditions:
C (a) all atoms done; (b) one fo CA or O missing; (c) break in chain
IF(NAT.LT.0.OR.IERR.NE.0) THEN
LEND=1
ELSE
LEND=0
ENDIF
C
IF(LEND.EQ.0) THEN
C Not last one unless CA-CA distance too large
C A is vector CAi to Ci+1
CALL VDIF(A,XCA(1,2),XCA(1,1))
IF(DOT(A,A).GT.DISMAX) LEND=1
ENDIF
IF(LEND.EQ.0) THEN
C Not last one
C B is vector CAi to Oi
CALL VDIF(B,XO(1,1),XCA(1,1))
C C = A x B; D = C x A
CALL CROSS(A,B,C)
CALL CROSS(C,A,D)
CALL UNIT(D)
C
IF(I.EQ.1) THEN
C First peptide, no previous one to average with
CALL VSET(E,D)
C No offset for first CA
CALL ZEROI(P,3)
ELSE
C Not first, ribbon cross vector is average of peptide plane
C with previous one
CALL SCALEV(B,SIGN(1.,DOT(D,G)),D)
CALL VSUM(E,G,B)
C Offset is along bisector of CA-CA-CA vectors A (H is Ai-1)
CALL VDIF(P,H,A)
CALL UNIT(P)
ENDIF
ELSE
C Last one, just use last plane
CALL VSET(E,G)
C No offset for last CA
CALL ZEROI(P,3)
ENDIF
C Normalise vector E
CALL UNIT(E)
C WRITE(NOISE,1003) I,G,D,B,E
C1003 FORMAT(' I,G,D,B,E',I4,4(3X,3F8.2)/)
C
C
C Generate guide points
CALL SCALEV(P,OFFSET,P)
CALL VSUM(P,XCA(1,1),P)
C
DO 20,J=1,NRIB
FR=(FLOAT(J)-RIB2)*DRIB
CALL SCALEV(F,FR,E)
CALL VSUM(GUIDE(1,I,J),P,F)
C EAM - Maybe should be NAT-2 ??
guide(4,i,j) = NAT - 3
20 CONTINUE
C
C Store things for next residue
CALL VSET(XCA(1,1),XCA(1,2))
CALL VSET(XO(1,1),XO(1,2))
CALL VSET(G,E)
CALL VSET(H,A)
C
IF(LEND.EQ.0) GO TO 10
C
NPT=I
CALL RIBDRW(GUIDE,NRIB,MAXRES,NPT,NCHORD)
C
C Loop chains if required
CEAM IF(NAT.GT.0) GO TO 1
IF (IERR.EQ.0) GOTO 1
C
RETURN
END
C
C
SUBROUTINE pdb_GETCAO(XCA,XO,NAT,NATOM,IERR)
C ========================================
C
C Get coordinates of CA in XCA, O in XO,
C Modified to read sequential CA and O records in PDB format from file
C
C On exit: NAT next atom
C IERR =0 if succesfull, else = 1
C
DIMENSION XCA(3),XO(3)
C
integer PDBFILE
parameter (PDBFILE = 1)
character*1 a1, rescode(2)
character*3 resname(2)
character*4 reclabel, atname
integer resno(2)
C
ierr=0
read (pdbfile,2,end=100) reclabel, nat, atname, a1, resname(1),
1 a1, resno(1), rescode(1), xca(1), xca(2), xca(3)
read (pdbfile,2,end=100) reclabel, nat, atname, a1, resname(2),
1 a1, resno(2), rescode(2), xo(1), xo(2), xo(3)
2 format(a4,2x,i5,1x,a4,a1,a3,1x,a1,i4,a1,3x,5f8.3,2f6.2,1x,i3)
if (resname(1) .ne. resname(2)) ierr = 1
if (resno(1) .ne. resno(2)) ierr = 1
if (rescode(1) .ne. rescode(2)) ierr = 1
return
100 continue
ierr = 1
nat = -1
return
end
SUBROUTINE GETCAO(XCA,XO,NAT,NATOM,IERR)
C ========================================
C
C Get coordinates of CA in XCA, O in XO,
C modified to get coords from common /SPAM/
C
C On exit: NAT next atom
C IERR =0 if succesfull, else = 1
C
DIMENSION XCA(3),XO(3)
C
parameter (MAXATOM=10000)
common /SPAM/ natm, SPAM(4,MAXATOM), SCAM(MAXATOM)
integer SCAM
c
if ((nat .gt. natm) .or. (nat .gt. natom-1)) then
ierr = 1
CEAM nat = -1
return
end if
do i=1,3
xca(i) = spam(i,nat)
xo(i) = spam(i,nat+1)
end do
nat = nat + 2
ierr = 0
return
end
subroutine zeroi( a, nwords )
integer*4 a(nwords)
do i = 1,nwords
a(i) = 0
end do
return
end
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