Subject: Mopac93 does not like my Zwitter ion

From: "Ed E. Moret" <[email-masked]>
Date: Thu, 08 Jul 1999 13:44:07 +0200

Hi CCL

While optimising my extended amino acid, 6-amino-hexanoic-acid, from
this particular (attached file 6-AHA.mol2 or appended 6-AHA.dat)
starting
conformation with Mopac93 (AM1 PRECISE), the molecule folds and a proton
jumps
>from the amino-terminus to the carboxy-terminus.

This result is rather dependent on the current starting geometry, so
should
not be considered too reliable, but still:
is it possible that 6-AHA is not a Zwitter ion and the computation is
correct?
What experimental data to consult?

Hopefully someone wants to have a look at these files and share his/her
thoughts on this.

With best regards
Ed Moret
PS 6-AHA.dat is appended below
-- 
| Ed E. Moret	(@more@)	Department of Medicinal Chemistry
| Faculty of Pharmacy	Utrecht University	The Netherlands
| Tel.: +31 30 2536979(2536958)	Fax: +31 30 2536655 
| E-mail: [email-masked]	WWW: http://wwwcmc.pharm.uu.nl/moret/

T=3600 AM1 NOINTER BONDS PRECISE 
/mnt/edu/moret/6-AHA.dat
 
0001 5.1982    0001 0.3053    0001 -8.9626   0001 0000 0000 0000
0006 4.5965    0001 0.6742    0001 -8.1320   0001 0000 0000 0000
0001 4.8952    0001 1.6948    0001 -7.8928   0001 0000 0000 0000
0001 2.8093    0001 -0.3674   0001 -8.7654   0001 0000 0000 0000
0006 3.1080    0001 0.6532    0001 -8.5262   0001 0000 0000 0000
0001 2.9533    0001 1.2900    0001 -9.3972   0001 0000 0000 0000
0001 6.4582    0001 -0.8408   0001 -5.6370   0001 0000 0000 0000
0006 6.3035    0001 -0.2039   0001 -6.5080   0001 0000 0000 0000
0001 6.6022    0001 0.8167    0001 -6.2689   0001 0000 0000 0000
0001 4.2133    0001 0.1440    0001 -6.0716   0001 0000 0000 0000
0006 4.8150    0001 -0.2249   0001 -6.9023   0001 0000 0000 0000
0001 4.5163    0001 -1.2456   0001 -7.1414   0001 0000 0000 0000
0001 6.8555    0001 -1.7456   0001 -7.9203   0001 0000 0000 0000
0006 7.1530    0001 -0.7248   0001 -7.6808   0001 0000 0000 0000
0001 6.9994    0001 -0.0882   0001 -8.5522   0001 0000 0000 0000
0008 9.0112    0001 -0.2659   0001 -6.0538   0001 0000 0000 0000
0006 8.6404    0001 -0.7038   0001 -7.2868   0001 0000 0000 0000
0008 9.5843    0001 -1.1231   0001 -8.1717   0001 0000 0000 0000
0001 2.5728    0001 2.1184    0001 -7.1728   0001 0000 0000 0000
0001 2.4368    0001 0.5522    0001 -6.5758   0001 0000 0000 0000
0001 1.2961    0001 1.1397    0001 -7.6629   0001 0000 0000 0000
0007 2.2917    0001 1.1537    0001 -7.3992   0001 0000 0000 0000

#
#	  Creating user name:		hermel InsightII
#	  Creation time:     		Tue Jun 22 17:15:28 1999

@<TRIPOS>MOLECULE
AHA
   22    21     5     0     0                                                  
SMALL
USER_CHARGES
@<TRIPOS>ATOM
      1 H22         5.1982    0.3053   -8.9626 H         1 ETHL1      0.1000 ****               
      2 C2          4.5965    0.6742   -8.1320 C.3       1 ETHL1     -0.2000 ****               
      3 H21         4.8952    1.6948   -7.8928 H         1 ETHL1      0.1000 ****               
      4 H11         2.8093   -0.3674   -8.7654 H         1 ETHL1      0.1000 ****               
      5 C1          3.1080    0.6532   -8.5262 C.3       1 ETHL1      0.2200 ****               
      6 H12         2.9533    1.2900   -9.3972 H         1 ETHL1      0.1000 ****               
      7 H21         6.4582   -0.8408   -5.6370 H         2 ETHL2      0.1000 ****               
      8 C2          6.3035   -0.2039   -6.5080 C.3       2 ETHL2     -0.2000 ****               
      9 H22         6.6022    0.8167   -6.2689 H         2 ETHL2      0.1000 ****               
     10 H11         4.2133    0.1440   -6.0716 H         2 ETHL2      0.1000 ****               
     11 C1          4.8150   -0.2249   -6.9023 C.3       2 ETHL2     -0.2000 ****               
     12 H12         4.5163   -1.2456   -7.1414 H         2 ETHL2      0.1000 ****               
     13 H12         6.8555   -1.7456   -7.9203 H         3 METH3      0.1000 ****               
     14 C1          7.1530   -0.7248   -7.6808 C.3       3 METH3     -0.2000 ****               
     15 H11         6.9994   -0.0882   -8.5522 H         3 METH3      0.1000 ****               
     16 O3          9.0112   -0.2659   -6.0538 O.2       4 CBXM4     -0.5700 ****               
     17 C1          8.6404   -0.7038   -7.2868 C.2       4 CBXM4      0.1400 ****               
     18 O2          9.5843   -1.1231   -8.1717 O.2       4 CBXM4     -0.5700 ****               
     19 H13         2.5728    2.1184   -7.1728 H         5 AMN45      0.3600 ****               
     20 H12         2.4368    0.5522   -6.5758 H         5 AMN45      0.3600 ****               
     21 H11         1.2961    1.1397   -7.6629 H         5 AMN45      0.3600 ****               
     22 N1          2.2917    1.1537   -7.3992 N.3       5 AMN45     -0.5000 ****               
@<TRIPOS>BOND
    1     2     1 1
    2     5     2 1
    3     2    11 1
    4     2     3 1
    5     5     4 1
    6     5    22 1
    7     5     6 1
    8     8     7 1
    9    11     8 1
   10     8    14 1
   11     8     9 1
   12    11    10 1
   13    11    12 1
   14    14    13 1
   15    14    17 1
   16    14    15 1
   17    17    16 ar
   18    17    18 ar
   19    22    19 1
   20    22    20 1
   21    22    21 1
@<TRIPOS>SUBSTRUCTURE
      1 ETHL1              1 ****               0 ****  ****    
      2 ETHL2              7 ****               0 ****  ****    
      3 METH3             13 RESIDUE            0 ****  ****    
      4 CBXM4             16 ****               0 ****  ****    
      5 AMN45             19 ****               0 ****  ****