Phosphodiester backbone torsion angles are normally found in one od the three staggered conformation: gauche⁺, gauche^-, or trans. The beta torsion angle can be derived from the ³J_P5'-H5',  ³J_P5'-H5'' and ³J_P5'-C4' coupling constants and has been used for many years in the conformational analysis of the phosphodiester linkages in nucleotides. Karplus equation has been parametrizated in: 95TL1949 , 94NAR2658. In particular, for the beta angle, this three rotamers have unique J values:

Trans conformation: Both ³J_P-H5' are small and ³J_P5'-C4' is large.

If is not trans, either ³J_P-H5' is large and ³J_P5'-C4' is small. and stereospecific H5' assignment is required.

Some methods to measure them are:

• J_PH
• Simulation of cross-peaks patterns in ¹H-¹H COSY spectra (90BIO11161)
• 91QRB479
• ¹H-Selective 2D ³¹P J-resolved experiment (87JACS7525 and 91JB205 )
• 94JB595
• P-FIDS-CT-HSQC experiment (93JB479 and 94JB631).
• 95JB315
• 2D {³¹P} Spin-Echo Difference CT [¹H-¹³C]-HSQC experiment ( 95JACS7277 ).
• 2D ¹H-³¹P F1-J-scaled HMBC experiment ( 00MRC692 ).
• 2D and 3D PH-constant time heteronuclear COSY sequences ( 02JB65-22 )
• J_CP
• P-FIDS-CT-HSQC experiment (93JB479 and 94JB631).
• Quantitative evaluation of a 3D HCP experiment ( 98JB223).
• Intensity analysis in ³¹P spin-echo difference CT-HSQC ( 95FEBS156 ) and ³¹P spin-echo difference CT-HCCH ( 98JB423 ) experiments
• 2D {³¹P} Spin-Echo Difference CT [¹H-¹³C]-HMQC experiment ( 99JMR491-140 ).