Hi Thu,
> I am wondering how the charges for protonated histidine (HIP)
> are generated with tleap.
tleap does not generate any charges - the charges are read from the lib
files. In the case of FF03 for regular residues this would be:
all_amino03.lib
for n terminal it would be
all_aminont94.lib
and for c terminal it would be
all_aminoct94.lib
> After all, I checked charges of
> HIP in all_amino03.lib with those generated in the parm
> file(considering the conversion factor of 18.2223) and I
> found out that the charges are not the same. Here is how I
> processed tleap.
>
> source leaprc.ff03
> w = loadPdb file.pdb
> saveAmberParm w file.parm file.rst
> quit
>
> In the end of the leaprc.ff03 file, I have edited
> #
> # assumed that most often proteins use HIE
> #
> HIS = HIP
This is a somewhat weird way to approach the problem. In general you should
edit your pdb file and change the residue names to the protonation state you
want them to be.
Here is a quick test that I tried:
$AMBERHOME/exe/tleap
source leaprc.ff03
mymol = copy HIP
saveamberparm mymol prmtop inpcrd
Using ambpdb to extract the charges from the prmtop
$AMBERHOME/exe/ambpdb -pqr -p prmtop < inpcrd
I get
REMARK HIP
ATOM 1 N HIP 1 3.326 1.548 0.000 -0.4250 1.550
ATOM 2 H HIP 1 3.909 0.724 0.000 0.2859 1.200
ATOM 3 CA HIP 1 3.970 2.846 0.000 0.3750 1.700
ATOM 4 HA HIP 1 3.672 3.400 -0.890 -0.0146 1.200
ATOM 5 CB HIP 1 3.577 3.654 1.232 -0.3321 1.700
ATOM 6 2HB HIP 1 2.497 3.801 1.241 0.1077 1.200
ATOM 7 3HB HIP 1 3.877 3.116 2.131 0.1077 1.200
ATOM 8 CG HIP 1 4.201 5.026 1.321 0.1824 1.700
ATOM 9 ND1 HIP 1 3.943 5.885 2.383 -0.0876 1.550
ATOM 10 HD1 HIP 1 3.340 5.692 3.170 0.3051 1.200
ATOM 11 CE1 HIP 1 4.624 6.998 2.183 -0.0131 1.700
ATOM 12 HE1 HIP 1 4.563 7.812 2.905 0.2306 1.200
ATOM 13 NE2 HIP 1 5.294 6.891 1.062 -0.1488 1.550
ATOM 14 HE2 HIP 1 5.896 7.605 0.677 0.3773 1.200
ATOM 15 CD2 HIP 1 5.059 5.679 0.492 -0.1921 1.700
ATOM 16 HD2 HIP 1 5.538 5.418 -0.451 0.2352 1.200
ATOM 17 C HIP 1 5.486 2.705 0.000 0.5666 1.700
ATOM 18 O HIP 1 6.009 1.593 0.000 -0.5604 1.500
TER
END
Column 9 is the charge - read from the prmtop file by ambpdb and divided by
18.2223.
Which, allowing for round off matches the definition of HIP in
all_amino03.lib
!entry.HIP.unit.atoms table str name str type int typex int resx int
flags
int seq int elmnt dbl chg
"N" "N" 0 1 131072 1 7 -0.424967
"H" "H" 0 1 131072 2 1 0.285873
"CA" "CT" 0 1 131072 3 6 0.375022
"HA" "H1" 0 1 131072 4 1 -0.014621
"CB" "CT" 0 1 131072 5 6 -0.332123
"HB2" "HC" 0 1 131072 6 1 0.107725
"HB3" "HC" 0 1 131072 7 1 0.107725
"CG" "CC" 0 1 131072 8 6 0.182399
"ND1" "NA" 0 1 131072 9 7 -0.087602
"HD1" "H" 0 1 131072 10 1 0.305096
"CE1" "CR" 0 1 131072 11 6 -0.013105
"HE1" "H5" 0 1 131072 12 1 0.230635
"NE2" "NA" 0 1 131072 13 7 -0.148766
"HE2" "H" 0 1 131072 14 1 0.377295
"CD2" "CW" 0 1 131072 15 6 -0.192052
"HD2" "H4" 0 1 131072 16 1 0.235237
"C" "C" 0 1 131072 17 6 0.566646
"O" "O" 0 1 131072 18 8 -0.560417
So as far as I can tell this is working correctly. You should try taking a
clean amber tree (where leaprc files have not been modified etc) and then
edit your pdb to change the residue name from HIS to HIP and then repeat the
process and see what you get. I would also make sure you run the test cases
in $AMBERHOME/test to validate your compilation.
All the best
Ross
/\
\/
|\oss Walker
| Assistant Research Professor |
| San Diego Supercomputer Center |
| Tel: +1 858 822 0854 | EMail:- ross.rosswalker.co.uk |
|
http://www.rosswalker.co.uk | PGP Key available on request |
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Received on Sun Mar 16 2008 - 06:07:40 PDT
