I was reading an article the other day about smoked meats and the smoke ring.
http://amazingribs.com/tips_and_technique/mythbusting_the_smoke_ring.html
and
http://www.genuineideas.com/ArticlesIndex/sratlas.html
I have always followed the idea of 140 degrees F is about as far as smoke can be applied to meat.
The 140 degree may apply to pork but not red muscle meat like beef and venison.
Like Chef Jacob, the articles go into the detail of what is happening with the process.
The process is myoglobin in the meat.
An interesting set of articles to form your own idea.
Chris