生物大分子波谱学原理 吴委辉 Strategy for Assigning Spin Systems of Peptides/Proteins using 2D TOCSY and 2D DOF-COSY Methods use TOCSY to group all protons within a spin system then use COSY to "order"the protons within the group: 兰 兰 9 尘 坐 -N-Ca-C- 至 Cg Hg HN Ha Hg Hb HN Ha Hg Hb 2D long-mix TOCSY 2D DQF-COSY
生物大分子波谱学原理 吴季辉
生物大分子波谱学原理 A Strategy for Assigning the Spin Systems of Peptides/Proteins Using 2D Proton Homonuclear NMR Experiments Try to determine as many spin systems as possible by identifying through bond connections obtained from COSY and TOCSY spectra.Start with "fingerprint region" (HN-Ha)of DQFCOSY to "anchor"each spin system (note that glycines will often show two HN-Ha crosspeaks). Use TOCSY crosspeak pattern in "amide towers"(vertical slice through each HN position)to "type"each spin system: Glycines will have no more than 1 or 2 crosspeaks in the HN tower,even in long-mix TOCSY.Also,the aCH2 group usually gives an"AX"spectrum with a large doublet splitting from the geminal proton coupling constant of 15 hz. ·Identify aCH-BCH2“AMX”spin systems of those spin systems that haveβ proton chemical shifts in the 2.5-4.0 ppm range and no additional crosspeaks even in long-mix TOCSY: Ser,Asp,Asn,Cys,Trp,Phe,Tyr,His Note:Ser B is often found around 4.0 ppm close to a shift
生物大分子波谱学原理 吴季辉