Basic HSQC sequence with States-TPPI quadrature detection 1H coupled HSQC-13C peaks are split by C-H couplings in /4.Jrs 中31 01=x,-=x States-TPPI 2=x,x,-6,x 1H decoupled HSQC-13C peaks are singlets in 01 at natural abundance, 031=K,一x,-x,x split by 13C-13C couplings in 13C labeled systems +States-TPP 12 4 1/4US Φ31 1/2 gradients must be of opposite signs to continue to dephase I spins not coupled to S
The duration (A)of S-spin chemical shift evolution during the first t1 increment(Ist two FIDs) dictates the extent of phase correction required in the o dimension. 1H coupled HSQC t红 pwx G △=2×(2pwx/π)+4(0) off-resonance effects 1 st order(lp1)=-360×sw1×△ zero order(rp1)=-phc1/2 1H decoupled HSOC 2xpw 1/4Js t1/2 2 G △=2×(2DwX/π)+2×Dw+t.(0)
If△=1/(2×sw1)or half the dwell time, 1 st order(lp1)=-360×sw1×1/(2×sw1)=-180 zero order(rp1)=90 there is no need to calculate the phase constants 1H decoupled HSQC 2xpw 1/4Us 1/4Js 1 1/2 t/2 G 4(0)= -2x(2×pwx/π)-2×pW (2×swl) △=2×(2×pwx/π)+2×pw+4(O) 1 (2×swI)
Another way to avoid phase corrections in is to introduce a 180s pulse at the end of the t period, followed by a delay 8,to refocus chemical shift precession during t(0) 1st order(Ip1)=zero order (rp1)=0 if t1(0)~0.0 1st order (Ip1)=-180,zero order(rp1)=90 if t1(0)=1/(2sw1) 1H decoupled HSQC 2xpw 02 1/2 t/2 δ=2×pw+t(0) the off-resonance effects of the two 90S pulses are refocused by the 180S pulse, so they do not have to be included in the phase constant calculation. The Jis coupling evolves for the period 8,but since 8~us,the effect is negligible