dextran.martini3.ff

;
; Martini model for dextran
;
[ citations ]
Martini3
polyply
M3_sugars

[ moleculetype ]
; molname    nrexcl
  DEX   3

[ atoms ]
; nr type resnr residue    atom cgnr charge mass
  1  SP4r   1   DEX    A    1    0  54.0
  2  SP4r   1   DEX    B    2    0  54.0
  3  SP1r   1   DEX    C    3    0  54.0
  4  TC4    1   DEX    VS   4    0  0.00
[ bonds ]
; residue internal bonds
  A   B   1    0.345 10000 {"ifdef": "FLEXIBLE"}
  A   C   1    0.460 10000 {"ifdef": "FLEXIBLE"}
  B   C   1    0.368 10000 {"ifdef": "FLEXIBLE"}
[ constraints ]
; i  j  funct length
  A   B   1    0.345 {"ifndef": "FLEXIBLE"}
  A   C   1    0.460 {"ifndef": "FLEXIBLE"}
  B   C   1    0.368 {"ifndef": "FLEXIBLE"}
[ virtual_sitesn ]
VS A B C -- 1
[ exclusions ]
VS A B C
[ edges ]
A VS

;============================================================
;                   ALPHA 1,6 LINK
;============================================================

[ link ]
; alpha 1->6
resname "DEX"
[ atoms ]
A  { }
B  { }
C  {"replace": {"atype": "SN6r"}}
+A {"replace": {"atype": "SN6"}}
+B { }
+C { }

[ bonds ]
; i  j  funct  length  force constant
  C  +A   1      0.375  6500 {"group": "a16"}

[ angles ]
; i  j  k funct angle force con.
A   C  +A  10  115   160 {"group": "ACA - a16"}
C  +A  +C  10  68    320 {"group": "CAC - a16"}
C  +A  +B  2   100   180 {"group": "CAB - a16"}
B   C  +A  2   120    50 {"group": "BCA - a16"}

[ dihedrals ]
A C  +A  +C 9 0 12 1 {"version": "1", "group": "ACAC - a16"}
A C  +A  +C 9 0  8 2 {"version": "2", "group": "ACAC - a16"}

[ dihedral_restraints ]
A  C  +A  +C 1 -120 0.0 4.9 {"group": "ACAC - a16"}

[ link ]
resname "DEX"
[ dihedrals ]
C  +A  +C ++A 9 0   4 4 {"version": "1", "group": "CACA - a16"}
C  +A  +C ++A 9 90  4 6 {"version": "2", "group": "CACA - a16"}
[ dihedral_restraints ]
C  +A  +C  ++A 1 -135 0.0 1.5 {"version": "1", "group": "CACA - a16"}