Final Exam Flashcards
(48 cards)
Best describes 1, n-ADEQUATE (4)
- proton-detected
- “out and back” experiment
- correlates proton to carbon four bonds in a psuedo-4JCH coupling
- useful in structure elucidation of highly substituted aromatic ring molecule
What 1, n-ADEQUATE and 1,1- ADEQUATE have in common
- initial 1JCH coupling in magnetization transfer pathways
- low sensitivity
best describes 1,1-ADEQUATE
developed prior to 1, n-ADEQUATE
advantage of running 1,n-ADEQUATE
-gives long-range heteronuclear correlation such as a psuedo-4JCH coupling which is especially useful for structure elucidation of proton-deficient molecules
disadvantage of running 1,n-ADEQUATE
-sometimes leak 2JCH correlation into the spectra, making the data ambiguous
JRES
2D NMR
f1 and f2 axes of JRES spectrum
-coupling on f1 axis, chemical shift on f2 axis
main use of JRES spectroscopy
-simplify 1D NMR spectra
True or False: JRES can involve either homonuclear couplings or heteronuclear couplings
True
JRES spectroscopy is limited to:
first order spin systems
What does WaterLOGSY stand for
Water-Ligand Observed via Gradient Spectroscopy
basic principle of WaterLOGSY (3)
- one-dimensional NMR technique dependent on NOESY technique
- involves transfer of magnetization by an intramolecular NOE and spin diffusion caused by protein and ligand
- RF irradiation causes magnetization of bulk of water molecules to become excited
- transferred to bound ligand during NOESY mixing time
How is Water LOGSY spectrum interpreted
-positive resonances given by compounds that bind to target protein and negative resonance are given by compounds that have no interaction with the protein ligand
advantage of WaterLOGSY (3)
- detecting ligand binding due to high sensitivity and reliability
- provide structural information
- useful in developmental process of drugs
What pulse irradiates the protein-ligand complex in STD-NMR
Gaussian-shaped saturation pulse
size limit of protein that STD-NMR assays
-no size limit – larger the protein, the more effective
requirement for ligand size
-has to be big enough to adequately be saturated by pulse sequence
why STD-NMR is an improvement upon other NMR techniques
- far more sensitive
- doesn’t require a large sample
- can be directly detected from a mixture
What information can STD-NMR provide
-proximity of the ligand to the protein
2 main uses of solid state
- useful when only small amount of sample available
- useful for samples that don’t go into solution very well
most significant difference between solution NMR and solid state NMR
- in solution molecule can be tumbled rapidly and randomly
- solid state unable to be tumbled
3 methods used to produce sharp peaks in solid state
- Magic Angle Spinning
- Cross Polarization
- Combined Rotation and Multiple Pulse Sequence
Why do peaks appear split in solid state NMR
-split peaks indicate presence of two crystal environments in solid sample
what is importance of eliminating spinning sidebands
-mistakenly read as peaks in spectra
