Equation relating tumbling and relaxivity

[eliseoquiroz]

I am wondering if there is an equation that shows the effects of the rotational correlation time of a contrast agent to its relaxivity? I am synthesizing a contrast agent for my master's project and I want to show that binding a protein with a two point attachment will effectively enhance the relaxivity by slowing the tumbling rate. If there is no equation, can you point me in the direction that shows changing the rotational correlation time parameter and how it can change the relaxivity.

Thank You