MacroModel Reference Manual - ISP

Chapter 4: Operation Codesarg2Clear prior constraints0 No (default)1 Yesarg5arg6Force constantDefault: 1000.Angular half-widthDefault: 60.FXHB — FiX Hydrogen BondsGenerates a series of distance (FXDI) and angle (FXBA) flat-bottomed constraints to constrainthe geometry of hydrogen bonds.arg1 Donor Atom0 Constrain all hydrogen bonds. Possible hydrogen bonds are restricted to:• Hydrogen - Acceptor distance < 2.5 A,• D-H-A angle < 90 degrees,• H-A-R angle < 60 degrees.> 0 Donor atom number. If arg1 > 0, then:arg2arg3Hydrogen atomAcceptor atomarg5H–A distance constraint valueThe half-width of the flat-bottomed constraint is set to 0.5 Å0 use 1.85 Å−1use the current value> 0 use this valuearg6D-H-A angle constraint valueThe half-width of the flat-bottomed constraint is set to 30°.MacroModel 9.7 Reference Manual 73