CSA-DD Cross-Relaxation

The relaxation interference or cross-relaxation between chemical shift anisotropy (CSA) and dipolar-dipolar coupling (DD) causes the two lines of a scalar-coupled IS spin system doublet to have different line widths due to their different relaxation behavior. It has been demonstrated that such cross-correlation is directly proportional to the generalized order parameter S². Such effects have been succesfully applied in structural and dynamic studies of proteins ( 00JMR45-143 ) and can be utilized to obtain sharp linewidths for very large proteins (see the TROSY experiment).
 

Transverse Cross-Correlation Rates: R(S_x-->2S_xI_z) = 2ad{4J(0) +3J(w)}
Longitudinal Cross-Correlation Rates: R(S_z-->2S_zI_z)= 2ad {6J(w)}

The ratio between these rates allows to measure the correlation times of proteins:

J(0)/J(w) = (3/4)*[2( R(S_x-->2S_xI_z))/ R(S_z-->2S_zI_z))-1]

NMR Experiments:

• The basic pulse sequence to measure CSA-DD cross-correlation are slightly modified HSQC pulse trains with a cross-correlation period inserted before the typical S evolution period. More details can be found in: 96JACS6986 and 99JMR169-136 .
• Different approaches to access the CSA/dipolar interference interactions:
  Direct methods based on the ration of in-phase and antiphase components registered in two separate experiments
  Direct methods based on the different evolution of the doublet components
  Indirect methods which yield cross-correlation rates from an interative fitting procedure.

Applications of CSA-DD cross-correlation rates measurements:
 

CSA	DD	References	Observations
15N	15N-1H	96JACS6986 97JMR128-127 98JMR487-135 98JACS7905 98JACS10947 98JMR346-130 99JACS4242 00JMR175-144 00JMR280-144 01JMR137-150 03JB181-26 03MRC837 03JMR258-161 04JB133-30 05JB149-31	Determination of magnitude and orientation of 15N CSA Identify residues involved in conformational exchange Characterization of overall and local dynamics
15N	13CA-1HA	00JMR45-143 02JB291-24	Measurement of backbone dihedral angle phi
1H	15N-1H	97JMR128-127 97JACS8076 97JACS8985 01JMR149-149	Hydrogen Bonding
13CO	15 N-13CO	98JMR487-135 00JACS4841 04CPC807	Measurement of 13CO CSA
13CA	13CA-1HA	97JACS9576 99JMR169-136	3D (HA)CA(CO)NH experiment In CH3 groups ( 03JB351-27)
13C	13C-1H	04JB397-30	Measurement of 13C CSA in CH3 groups
1H	13C-1H	04JB397-30	Measurement of 13C CSA in CH3 groups
13CO	13CA-1HA	97JACS11938 98JB213 98JACS9880 99JACS6876 99JB277 00JB47 00JB265 01BIO9596 05ANG3232	Measurement of backbone dihedral angle phi
13CO	13CO-13CA	97JACS12629 00JMR280-144 00JACS4841 04CPC807 05JACS828 05ANG3232	Measurement of 13CO CSA
13CO	13CO-1HN	99JB297-14 00JACS4841 02JACS4050 04CPC807 05ANG3232	Measurement of 13CO CSA
13CO	15N-1H	00JACS12033 01JB347 01BIO9596	Discrimination between Type-I and Type-II beta-turns Refinement of the geometry of the metal coordinating sites in zinc-finger proteins
13CO	13CO-1HA	03JB159-27	Measurement of backbone dihedral angle phi

Also see CSA-DD cross-correlation in nucleic acids