Welcome to the WHAT IF homepage. [WHAT IF] is a versatile molecular modelling package that is specialized on working with proteins and the molecules in their environment like water, ligands, nucleic acids, etc.

WHAT IF has been designed and written over a long period of time. It started on Dec 6 1987 in Groningen, continued from 1989-2000 at the EMBL in Heidelberg, from 2000-2006 at the CMBI of the Radboud University Nijmegen, and in 2006 it moved with the CMBI to the Radboud University Nijmegen Medical Centre (Radboudumc).

WHAT IF was created to do my science, and distribution was an afterthought. So, be happy that you can get the software. And, the best of it, for academics it is now shareware.

The money raised by selling WHAT IF goes to the WHAT IF foundation. This foundation pays the coffee in the lab, and pays people who help me with parts of the code that are outside my field of expertise.

If you use WHAT IF, please refer to:
WHAT IF: A molecular modeling and drug design program.
G.Vriend, J. Mol. Graph. (1990) 8, 52-56.

A screendump of the OpenGL version of WHAT IF. One of the large new things in WHAT IF 6.0 was the introduction of a few fancy graphics options, like these solid spheres.

Theory behind options

In the theory section you will find a small start of the theory behind WHAT IF options. Please do not expect too much yet. It is a lot of work, and comes with little glory...


WHAT IF is meant to run on LINUX systems. WHAT IF will run on a whole series of other computers, but we have no means to be sure about the performance (if any) on SUN, IBM, HP, etc. It ran on all those machines in the past, but that is all we can say now... Full-screen stereo is only supported on Linux machines, while side-by-side stereo is supported on all machines. I.e. if you manage to compile WHAT IF on SUN, HP, etc., then side-by-side stereo will also work on it. If you need WHAT IF on a Windows machine, well then you buy YASARA for Windows, and if you ask for it, you get the Twiset (that contains about 95% of all WHAT IF options) at no extra costs.