HNCACB

H_N, N(i), Cα(i), Cβ (i) and  H_N, N(i), Cα(i-1), Cβ (i-1) 3D correlation. Dimensions X=¹H, Y=¹³C and Z=¹⁵N. Peaks form Cβ(i) and Cα(i) are normally stronger than from Cβ(i-1) and Cα(i-1).

Cα and Cβ are in anti-phase (normally Cα are negative, but depends from phasing). Cα(i-1) and Cβ(i-1) can be invisible; Serine and Threonine Cβ’s have  higher chemical shifts between 60-70 ppm (more Informations)

HNCACB