********> bugfix.20
Author:   Bill Ross
Date:     6/6/95

Programs: nucgen

Severity: moderate

Problem:  Atom names for phosphate and sugar oxygens are not
          correct for residues in the 1994 force field.

Fix:  Make the following change to etc/nucgen.f
--------------------------------------------------------------------------
*** NEW nucgen.f
--- OLD nucgen.f
***************
*** 147,152
  C
        DIMENSION R(60),PHI(60),ZZ(60),NAMAT(60)
        DIMENSION IR1(9),IR2(9),JSEQ(9),HXREP(6),HXHT(6)
        DIMENSION NAME(6),IRDS(9,2),IRDE(9,2)
        DIMENSION LBRES(*),IPMOL(500)
        DIMENSION KSEQ(15),INDEXD(5,15),INDEXU(5,15)

--- 147,153 -----
  C
        DIMENSION R(60),PHI(60),ZZ(60),NAMAT(60)
        DIMENSION IR1(9),IR2(9),JSEQ(9),HXREP(6),HXHT(6)
+       DIMENSION KATN(3),NATN(3)
        DIMENSION NAME(6),IRDS(9,2),IRDE(9,2)
        DIMENSION LBRES(*),IPMOL(500)
        DIMENSION KSEQ(15),INDEXD(5,15),INDEXU(5,15)
***************
*** 157,162
        DATA IDNA,IRNA/4HD   ,4HR   /
        DATA JSEQ/4HHB  ,4HHE  ,4HPOM ,4HRIBO,4HADE ,4HGUA ,4HTHY ,
       +          4HCYT ,4HURA /
        DATA IRDS/   1,   2,   3,   6,  14,  26,  40,  50,   0,
       +             1,   2,   3,   6,  15,  27,   0,  41,  51/
        DATA IRDE/   1,   2,   5,  13,  25,  39,  49,  59,   0,

--- 158,165 -----
        DATA IDNA,IRNA/4HD   ,4HR   /
        DATA JSEQ/4HHB  ,4HHE  ,4HPOM ,4HRIBO,4HADE ,4HGUA ,4HTHY ,
       +          4HCYT ,4HURA /
+       DATA KATN/4HOA  ,4HOB  ,4HO1'  /
+       DATA NATN/4HO1P ,4HO2P ,4HO4'  /
        DATA IRDS/   1,   2,   3,   6,  14,  26,  40,  50,   0,
       +             1,   2,   3,   6,  15,  27,   0,  41,  51/
        DATA IRDE/   1,   2,   5,  13,  25,  39,  49,  59,   0,
***************
*** 448,453
                   else if (i.eq.nresh .and. k.eq.5 .and. ig.eq.iup) then
                     atnam = ' H3T'
                   else
  c
  c                  --- 3 char names start col. 14, 
  c                      4 char names start col 13. ---

--- 451,466 -----
                   else if (i.eq.nresh .and. k.eq.5 .and. ig.eq.iup) then
                     atnam = ' H3T'
                   else
+ c
+ c                  --- adjust phosphate & sugar names
+ c
+                    if (namat(ig).eq.katn(1)) then
+                      namat(ig) = natn(1)
+                    else if (namat(ig).eq.katn(2)) then
+                      namat(ig) = natn(2)
+                    else if (namat(ig).eq.katn(3)) then
+                      namat(ig) = natn(3)
+                    endif
  c
  c                  --- 3 char names start col. 14, 
  c                      4 char names start col 13. ---
--------------------------------------------------------------------------

Temporary workarounds:  substitute atom names manually:

			OA  -> O1P
			OB  -> O2P
			O1' -> O4'

--