[gmx-users] Help with Error Message

[The One And Only]

So I started following some tutorials online since I didn't get a response
last time. the tutorial I'm using is:
http://nmr.chem.uu.nl/%7Etsjerk/course/molmod/
I followed that tutorial to the second page and got stuck at the step where
it asks you to input: pdb2gmx -f protein.pdb -o protein.gro -p protein.top
-ignh
I picked GROMOS96 45a3 force field(11) for the force field and spc(1) for
the water model but got the following error message:
Opening force field file
/usr/local/gromacs/share/gromacs/top/gromos45a3.ff/aminoacids.r2b
Reading protein.pdb...

-------------------------------------------------------
Program pdb2gmx, VERSION 4.6.3
Source code file:
/Users/christinalin/wget-1.14/gromacs-4.6.3/src/gmxlib/futil.c, line: 593

File input/output error:
protein.pdb
For more information and tips for troubleshooting, please check the GROMACS
website at http://www.gromacs.org/Documentation/Errors

Help please?