It's really not evident because your image uses pixels of variable size, sometimes 3x4, sometimes 5x4.
Here's a try, normalizing them all at 4x4 :

I made it in grafx2 by working in size 400%,  using the rotate tool, and at the end I used DawnBringer's "halfsmooth" script twice to reduce it back to 100%

edit: I had forgotten one of the frame, I used a flipped+90°-rotated version of another.



Edited by yrizoud - 18 December 2011 at 9:00am

Use it as you wish.
Note that it's no longer pixel art: it introduces intermediate colors for sub-pixels (using interpolation, not human-made choices)
You may especially want to clean up the 90° multiples, to make them sharper.