Is there a formula that would suggest a reasonable starting value for the mixing time based on the molecular weight, magnet field strength and solvent viscosity? Would anyone recommend some publication on the subject? Thanks!
asked
Evgeny Fadeev |

A mixing time that is about 1/3 to 1/2 of T1 will give maximum NOE. To estimate distances you need to be in the linear region of the transfer, or fit an entire mixing series. To get data in the linear region us a mixing time that is about 5% of T1. Since there is no hard relationsip betwen T1 and Mw or viscosity there is no equation such as the one you are asking for. There may be approximations which are true within a limited family of polymers, but there is no general realationship.
answered
dare |

There IS a relationship between The relationship between rotational correlation time and
The correlation time can be estimated from knowledge of MW and viscosity as follows: Assuming a spherical shape, the radius of hydration Use this radius, According to the Stokes-Einstein relation, the rotational diffusion coefficient And Rotational correlation time Therefore, rotational correlation
References: Cantor and Schimmel : Biophysical Chemistry M.Goldman : Quantum description of high-resolution NMR in liquids.
answered
sekhar Talluri Dr. Talluri, I've added little fixes to formatting so that equations show better. - Evgeny Fadeev (Feb 12 '10 at 12:33) |