# total charge

User 00698d4375

14-04-2007 19:53:59

Hi,

I would like to calculate the total charge of a set of molecules at pH=7.4.

I've used Instant JChem and the chemical term: sum (charge("7.4")) but the result is always a low negative value. Apparently, the hydrogen charges are not being summed.

Any suggestion to solve this problem?

Thanks

ChemAxon e08c317633

16-04-2007 17:29:52

 macneves wrote: Hi, I would like to calculate the total charge of a set of molecules at pH=7.4. I've used Instant JChem and the chemical term: sum (charge("7.4")) but the result is always a low negative value. Apparently, the hydrogen charges are not being summed. Any suggestion to solve this problem? Thanks
Hi,

You are right, the hydrogen charges are not being summed. Chemical Terms expression to calculate the charges with hydrogens:

 Code: sum(charge("7.4")) + sum(charge("implh", "7.4"))

Unfortunately, the

 Code: sum(charge("implh", "7.4"))

part of the expression does not return the result (it is a bug!), so the whole expression will not return the correct result.

We will fix this bug in the next version.

Best regards,

Zsolt

ChemAxon d76e6e95eb

16-04-2007 20:17:47

I suppose, that the current solution is a bit confusing, so we will change this function to include the charges of all atoms (either implicit or explicit). Thanks for drawing our attention to this problem!

ChemAxon e08c317633

17-04-2007 16:38:36

In the next JChem version (JChem 3.2.6) a new function will be available for calculating the total charge of a molecule:

 Code: totalCharge()

To get the total charge of major microspecies at pH 7.4 this expression can be used (from JChem version 3.2.6):

 Code: totalCharge(majorms("7.4"))

The

 Code: sum(charge("7.4")) + sum(charge("implh", "7.4"))

will also work (we have fixed the bug), but we recommend to use the totalCharge() function (it is faster).

Best regards,

Zsolt