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David, Mac Support Specialist
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Experience:  BSc H.Dip Apple Certified Professional
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I have a Mac Book Pro 10.6.8 When I try to run an application

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I have a Mac Book Pro 10.6.8 When I try to run an application that I have installed, I get this error message:
dyld: Library not loaded: /opt/local/lib/libgtk-x11-2.0.0.dylib
Referenced from: /Users/617anick/PQS/PQSMOL/pqsmol.x
Reason: image not found
./bin/pqsview: line 18: 8434 Trace/BPT trap $PQS_ROOT/PQSMOL/pqsmol.x --view $1
I have tried all kinds of ways to find a package or program which will include the needed file, /libgtk-x11-2.0.0.dylib. Where does this reside and how can I get it? I have installed Xcode and gtk2, to no avail. Thanks so much!
Hi, my name is XXXXX XXXXX I will do whatever I possibly can to help answer your questions.

What application are you trying to load?

Customer: replied 4 years ago.

It is a program called PQSmol from a commercial developer, It is a molecular display program (chemistry). I downloaded and installed it OK. However when I try to run it I get the error message pasted above. I contacted for tech support, twice, and have heard not back from them in 10 days, so I am reaching out to see if anyone can help me. I do see a few other references to similar error messages on the Internet, so I get the impression that this is not specific to PQSmol and I need to get libgtk-x11-2.0.0.dylib from somewhere ... but where?


This could be a tricky one to solve, and could be a version mismatch. The version you have could be intended for a different version of OS X.

You may be able to install what you need using MacPorts. First go to and install the 10.6.8 version.

Let me know if you have any trouble installing MacPorts. Let me know when it is installed.

Customer: replied 4 years ago.

Hi David,


Sorry, I should have said that I had found that tip on the Internet and I have already installed MacPorts.


David A.

Hi David,

No problem. So you had no luck with it I guess. Did it all work as expected, and could you find the package that you were looking for with it?

Also have the developers told you the minimum system requirement for the software?

Customer: replied 4 years ago.

Hi David

MacPorts installation went smoothly. There was no error

message after many many lines of output.

I just checked again at the website for minimum system requirements (for this mac version of the program PQSmol). I am not seeing it now but I thought I had checked previously, that 10.6.8 would be enough.

BtW here is a link to someone who asked an identical question for the identical problem on an OS 10.6.8:

but they seem to have had more success than me!

David A.


Do you have the original install discs that came with your Mac?

Customer: replied 4 years ago.

Yes. Using Pacifist and the Install Disk, I installed the "optional" Xcode (the entire package) a few days ago, as well as the Developers' packages. This created some new folders including /opt/local/lib/ which is where libgtk-x11-2.0.0.dylib is supposed to reside, but it did not give me a file with a name anything like libgtk*



It is best at this point to run an Archive & Install with the original discs.

This doesn't affect the rest of your system, just reinstalls the OS, and hopefully any missing files.

After the Archive & Install you will need to run software update to avoid any software version mismatches.

Insert the install disc and begin the installation. The default options are what you want, and just follow the assistant.

When it is finished run Software Update from the Apple menu.

Following all that, reinstall the application again.

Please get back to me when you have that done.

Customer: replied 4 years ago.

OK, David, I did as you suggested and re-installed the OS from disk.

Then I got the outstanding software updates, rebooted, and re-installed the pqsmol program.


Sad to say, the same error occurs as before. The entire output is pasted below.


David A.


617-Anicks-MacBook:~ 617anick$ ./bin/pqsmol &
[1] 414
617-Anicks-MacBook:~ 617anick$ PQS_BASDIR not set!
Set to default: /Users/617anick/PQS/BASDIR
dyld: Library not loaded: /opt/local/lib/libgtk-x11-2.0.0.dylib
Referenced from: /Users/617anick/PQS/PQSMOL/pqsmol.x
Reason: image not found
./bin/pqsmol: line 18: 415 Trace/BPT trap $PQS_ROOT/PQSMOL/pqsmol.x --build $1

[1]+ Exit 133 ./bin/pqsmol ./PQS/test.coord
617-Anicks-MacBook:~ 617anick$

Hi David,

I notice this is user specific. Use System Preferences, create a test admin user, login and install the software there.

Then let me know what happens.

Customer: replied 4 years ago.

Oops, I'm not seeing a way to do that under System Preferences. The "Accounts" icon under "System" sounds like the logical way to do this but it does not give me any way to "create new account." In a Linux terminal window, "useradd" should do this but the command "useradd" is not recognized ("command not found").

Can you give me slightly more detailed instructions?


Sure sorry. I shouldn't have assumed you were used to Mac OS X.

Unlock the padlock in the Accounts pane, in the bottom left, and click the + above it, that starts the add account assistant. Change account type to Administrator. Chose test name and password. Log out from the Apple menu, and log into the test account.

Hope this clarifies, sorry for passing over it so quickly.

Customer: replied 4 years ago.

Sorry about that ... I found the answer on line too, after writing back. I did not realize the "+" meant something. OK, so I did it and I installed a copy of the PQSmol program as testadmin. No surprise, same error:


bash-3.2$ ./bin/pqsmol &
[1] 676
bash-3.2$ PQS_BASDIR not set!
Set to default: /Users/testadmin/PQS/BASDIR
dyld: Library not loaded: /opt/local/lib/libgtk-x11-2.0.0.dylib
Referenced from: /Users/testadmin/PQS/PQSMOL/pqsmol.x
Reason: image not found
./bin/pqsmol: line 18: 677 Trace/BPT trap $PQS_ROOT/PQSMOL/pqsmol.x --build $1

[1]+ Exit 133 ./bin/pqsmol


I can't find minimum requirements either. Have you tried both installer types? RPM, and Tar?

Customer: replied 4 years ago.

I had not tried the rpm method, so just now I downloaded it and tried to open it as you can see pasted below. The rpm command is not recognized. A quick on-line search makes it look complicated what to do instead, as there is no single command that replaces rpm, and most advice applies to Lion or Mtn Lion while I have Snow Leopard. I hope you don't mind my asking you to advise me what to do with the .rpm file.





617-Anicks-MacBook:~ 617anick$ sudo rpm -ivh pqsmol-trial-2.0-1.x86_64.rpm
sudo: rpm: command not found
617-Anicks-MacBook:~ 617anick$


You can try this though it doesn't say for leopard.

I think the problem here is the version of OS X. Do you have another Mac you can test on?

Customer: replied 4 years ago.

Hi David,

(1) OK, I downloaded and installed RPM5, now I am not sure how to use it! Is RPM now going to be a command accessible via my PATH? If so, is the option -ivh as before?

(2) I do not have another Mac. Would you be willing to look in the /opt/local/lib/ folders of any of the Macs you have there, and see which if any might contain a file called libgtk-x11-2.0.0.dylib or anything like it? Maybe that would tell us something.



Hi David,

No I'm not sure about using RPM, maybe that's a bad idea after all. Try using the same command line as before.

It's a real pity there is no better support for this software, even a min requirements.

I'm using Mountain Lion on all my Macs and there is no /Opt/ folder, so that doesn't help but it was good thinking.

Looking at the name of the missing library it looks like X11.

Try downloading and installing XLL from here:

Choose version 2.5.0

Then install and try launch the application.

Let me know how it goes.

Customer: replied 4 years ago.

Hmm, still getting the same error when I run pqsmol but we may be getting closer.


(1) I am pasting below, the new contents of dylib's among /opt/local/lib/. Could one of these be another name for libgtk-x11-2.0.0.dylib? If so I will set up a symbolic link to it. Maybe one of those other versions of quartz has the elusive file? If so how might we search for it?


Also, these instructions are on the quartz page:

Default X11 Server (Snow Leopard Only)

If this is your first time installing XQuartz on Snow Leopard, you may wish to logout and log back in. This will update your DISPLAY environment variable to point to rather than If you would prefer to keep using as your default server (you can still launch manually), you'll want to disable /Library/LaunchAgents/org.macosforge.xquartz.startx.plist using ​launchctl(1).


(2) Shall I do the logout-login thing that they recommend (above)?


(3) RPM experiment gives an error message:

617-Anicks-MacBook:~ 617anick$ sudo RPM -ivh pqsmol-trial-2.0-1.x86_64.rpm
error: Invalid number of transaction elements.
617-Anicks-MacBook:~ 617anick$





617-Anicks-MacBook:~ 617anick$ ls /opt/local/lib/lib*dylib
617-Anicks-MacBook:~ 617anick$

Hi David,

One of those may well be the right file. It seems to be looking for an earlier version of X11 though, which doesn't seem right.

I would definitely advise the log out and log in advice. Maybe editing Launchctl will be worth a try if that fails. If we need to try that then is the best thing for editing it. You can Google Lingon.

I will also test out the application on Mountain Lion.

It is 2:30 am here, so when you reply I will most likely be gone offline. I will be online for about another half an hour I think. I am in Ireland, GMT timezone, and will be back online early in the morning to take your reply.

I will test it on Mountain Lion in the morning and let you know if I can get it going.

Best regards,
Customer: replied 4 years ago.

Hi David,

Logging out and in did not change anything that I can see.

It still seems to me that either we have to find out where to get libgtk-x11-2.0.0.dylib, or give up.

It is good for you to get sleep. You have really worked hard on my problem and I appreciate it. Maybe I can find another program entirely that will do the same things that pqsmol would do. I am going to look into that. And I will call the company, maybe everyone is on vacation and that's why they're not replying.

At least I learned some interesting things and I know I am not missing something obvious. Tomorrow I will be busy all day and will not get to work on this.

Take care, David

Hi David,

You're very welcome. I can spend time on this tomorrow when you are doing other things. Those dynamic libraries can be a real headache, I've had problems before using macports and fink etc to get software working. Looking at the application itself it looks like it relies heavily on the X window system, so I think that we fix that we fix the issue.

I will work on getting it running on Mountain Lion, and on a solution for Leopard, talk to you tomorrow.

Best regards,
Hi David,

Can you try installing X11 2.6.3 from and then install and try launching the software again, thanks.

Let me know how it goes when you get a chance.


Customer: replied 4 years ago.

Hi David,


No luck. The list of files in /opt/local/lib is slightly different after v. 2.6.3, but still does not include a libgtk-x11-2.0.0.dylib. Installing and attempting to run pqsmol results in the same error.


Just curious if you tried downloading and installing and running pqsmol on your machines -- the "trial version" is the one I am after since it has everything I need ( If it works for you, do you think it would make sense for me to upgrade to Mtn Lion 10.8.4 (or whatever is current)? I believe I can do so for just $20. Would there be any danger in doing so? If I upgrade and subsequently re-install pqsmol, can you predict if pqsmol would work?



Hi David,

I installed it no problem, but it will not launch. I get 'pqsmol.x: cannot execute binary file'.

I'm not sure why, I checked and it is set as an executable. It is most likely to be that it is not the right type of binary for Mountain Lion, thus the software is not compatible with Mountain Lion.

Therefore I would not recommend upgrading to Mountain Lion just to try this software.

The support for this over the web is very poor, and you say you have been trying to contact them too. That's very bad.

I would recommend trying other software that performs the same functionality. I did a Google search on it and it threw up this Wikipedia page. There seems to be a lot of software in this area.

It is a long list, but looks fairly comprehensive. I think if you go through what's there, you will find something that does what you want, probably even more specifically than PQS.

Let me know what you think about this, and if you want I can try contacting PQS on your behalf. I feel there is no point in troubleshooting much more without knowing some basic facts about the software.

Kind regards,
Customer: replied 4 years ago.

Thanks David. I see that it is time to close out this query. I appreciate all your good efforts. Unfortunately we must list it as one of the small minority of inquiries that were not successfully resolved.

I spoke w PQS. As I suspected, the main tech guy there (Pawel Wolinski, whom I know from previous interactions) is on a month-long vacation to his native Poland. He will be returning in August and I will see if I can get a response then.

I can consider other molecular viewing software programs, but my requirements (automatic display of hydrogen bonding, particular graphical projections, recognition of certain input formats, etc) narrow the options a lot, which is why I may still hold out for this program if I can get it to work.

Thanks again,

David A.

Hi David,

I think it's great that you have access to the author of the software, that doesn't often happen.

I'm a bit disappointed I could get it fixed for you.

If we were to persevere I would try installing this on a clean Mac OS X install, etc. and it would end up taking a long time. I think it's much better to wait to speak to the software developer directly.

I hope it works out smoothly and I'm sure with access to the developer it will.

Please feel free to request me on any future Mac questions, I will be very happy to help.

Your sincerely,
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