POF

Question 1

HSQC and HMQC link 13C and 1H or 15N and 1H

Answer 1

• Linking two nuclei provides valuable structural information
• Links can be over one or several bonds
• HSQC = Heteronuclear Single Quantum Coherence
• Builds on INEPT buidling blocks
• Can be extended to multiple nuclei, e.g. HCN or HNCA in proteins – then often acquired as three-dimensional spectra
• HMQC = Heteronuclear Multiple Quantum Coherence
• The HMQC was known first
• Different relaxation properties

Question 2

INEPT

Answer 2

Insensitive nuclei enhancement by polarization transfer (INEPT) is a signal enhancement method used in NMR spectroscopy. It involves the transfer of nuclear spin polarization from spins with large Boltzmann population differences to nuclear spins of interest with lower Boltzmann population differences.[1] INEPT uses J-coupling for the polarization transfer in contrast to Nuclear Overhauser effect (NOE), which arises from dipolar cross-relaxation. This method of signal enhancement was introduced by Ray Freeman in 1979. Due to its usefulness in signal enhancement, pulse sequences used in heteronuclear NMR experiments often contain blocks of INEPT or INEPT-like sequences.

Question 3

COSY - Pulsfolge

Answer 3

90° -> t1 -> 90° (x) (Kohärenztransfer von Spin1 auf Spin2) -> t2 (detection)

Question 4

DQF COSY -> resolves the line-shape problems

Answer 4

90° -> t1 -> 90° -> 90° -> t2 (detection)