# AMBER Archive (2009)Subject: Re: [AMBER] MM_PBSA Problem (no radius for ion)

From: Scott Brozell (sbrozell_at_rci.rutgers.edu)
Date: Thu Dec 17 2009 - 21:07:21 CST

Hi,

Here's what i did to the mm_pbsa_calceneent.pm file a while back
for amber9:

sub generate_pqr(){
###################

# This implementation uses bondi radii

# Parameters: \$pdb,\$pqr,\$r_mol
my \$pdb = shift;
my \$pqr = shift;
my \$r_mol = shift;

# Bondi radii + 1.4A and probe radius of 0.0A yields SAS
# Bondi radii + 0.0A and probe radius of 1.4A yields molecular surface
# Bondi radii + 0.0A and probe radius of 0.0A yields vdW surface
# SRB Oct 3, 2008; add fluorine vdw radius; see ticket 18558
# SRB Oct 13, 2008; add zinc radius; see ticket 18993
my %exp_rad = (
"N" => 1.550 + 1.400,
"H" => 1.200 + 1.400,
"C" => 1.700 + 1.400,
"O" => 1.500 + 1.400,
"P" => 1.800 + 1.400,
"S" => 1.800 + 1.400,
"FE" => 1.300 + 1.400,
"Na+" => 1.200 + 1.400,
"Cl-" => 1.700 + 1.400,
"MG" => 1.180 + 1.400,
"F" => 1.470 + 1.400,
"Zn" => 1.100 + 1.400,
);

print " Generate PQR\n";
print " Warning: the fluorine radius is 1.47 Angstroms.\n";
print " Warning: the zinc radius is 1.10 Angstroms.\n";
print " These warning only applies to MS=1 calculations.\n";
}

I also modified sander/mdread.f
1209a1210,1218
> else if (atype == 'ZN' .or. atype == 'Zn') then
> ! SRB Oct 13, 2008. See ticket 18993
> write( 6,* ) 'Warning: Non standard sander behavior!'
> write( 6,* ) ' Using zinc radius of 1.10 Ang. for SA.'
> x(l165-1+i) = 1.10d0 + 1.4d0
> x(l170-1+i) = 0.00000d0
> x(l175-1+i) = 0.00000d0
> x(l180-1+i) = 0.00000d0
> x(l185-1+i) = 0.00000d0
1233a1243,1251
> else if (atype(1:1) == 'F' .or. atype(1:1) == 'f') then
> ! SRB Sep 11, 2008. See ticket 18558
> write( 6,* ) 'Warning: Non standard sander behavior!'
> write( 6,* ) ' Using VDW radius of fluorine for SA.'
> x(l165-1+i) = 1.47d0 + 1.4d0 ! VDW radius of fluorine + 1.4 Ang.
> x(l170-1+i) = 0.00000d0
> x(l175-1+i) = 0.00000d0
> x(l180-1+i) = 0.00000d0
> x(l185-1+i) = 0.00000d0

Naturally followed by rebuilding.
I did this for someone else and don't remember any details or gottchas.

good luck,
Scott

On Thu, Dec 17, 2009 at 07:39:49PM +0000, s. Bill wrote:
> Dear AMBER
> Today, I have encountered another problem during performing MM-PBSA for my system. My system contains Zinc ion and Calcium ion.
> During binding_energy.mmpbsa step, I got the following error:
>         No radius found for ZN    2647 in residue ZN  172
> I searched the AMBER archieve and I found that we should modify the mm_pbsa_calceneent.pm file.
> I did add the raidus for my ions, as following:
>
>  if(exists \$r_del->{"IVCAP"} && (\$r_del->{"IVCAP"} == 1 || \$r_del->{"IVCAP"} == 5)){
>     # Prepare for calc of molecular surface
>     %exp_rad = (
>            "N"    => 1.550,
>            "H"    => 1.200,
>            "C"    => 1.700,
>            "O"    => 1.500,
>            "P"    => 1.800,
>            "S"    => 1.800,
>            "FE"   => 1.300,
>            "Na+"  => 1.200,
>            "Cl-"  => 1.700,
>            "MG"   => 1.180,
>            "ZN"   => 0.740,
>            "CA"   => 0.990,
>            );
> Unfortunately, I still have the same error.
> Could any body tell me what should I do? and also are these Radii values for Zinc (0.74) and Calcium (0.99) right?

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