Final Exam Flashcards

(48 cards)

1
Q

Best describes 1, n-ADEQUATE (4)

A
  • 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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What 1, n-ADEQUATE and 1,1- ADEQUATE have in common

A
  • initial 1JCH coupling in magnetization transfer pathways

- low sensitivity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

best describes 1,1-ADEQUATE

A

developed prior to 1, n-ADEQUATE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

advantage of running 1,n-ADEQUATE

A

-gives long-range heteronuclear correlation such as a psuedo-4JCH coupling which is especially useful for structure elucidation of proton-deficient molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

disadvantage of running 1,n-ADEQUATE

A

-sometimes leak 2JCH correlation into the spectra, making the data ambiguous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

JRES

A

2D NMR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

f1 and f2 axes of JRES spectrum

A

-coupling on f1 axis, chemical shift on f2 axis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

main use of JRES spectroscopy

A

-simplify 1D NMR spectra

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

True or False: JRES can involve either homonuclear couplings or heteronuclear couplings

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

JRES spectroscopy is limited to:

A

first order spin systems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does WaterLOGSY stand for

A

Water-Ligand Observed via Gradient Spectroscopy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

basic principle of WaterLOGSY (3)

A
  • 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 well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is Water LOGSY spectrum interpreted

A

-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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

advantage of WaterLOGSY (3)

A
  • detecting ligand binding due to high sensitivity and reliability
  • provide structural information
  • useful in developmental process of drugs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What pulse irradiates the protein-ligand complex in STD-NMR

A

Gaussian-shaped saturation pulse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

size limit of protein that STD-NMR assays

A

-no size limit – larger the protein, the more effective

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

requirement for ligand size

A

-has to be big enough to adequately be saturated by pulse sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

why STD-NMR is an improvement upon other NMR techniques

A
  • far more sensitive
  • doesn’t require a large sample
  • can be directly detected from a mixture
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What information can STD-NMR provide

A

-proximity of the ligand to the protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

2 main uses of solid state

A
  • useful when only small amount of sample available

- useful for samples that don’t go into solution very well

21
Q

most significant difference between solution NMR and solid state NMR

A
  • in solution molecule can be tumbled rapidly and randomly

- solid state unable to be tumbled

22
Q

3 methods used to produce sharp peaks in solid state

A
  • Magic Angle Spinning
  • Cross Polarization
  • Combined Rotation and Multiple Pulse Sequence
23
Q

Why do peaks appear split in solid state NMR

A

-split peaks indicate presence of two crystal environments in solid sample

24
Q

what is importance of eliminating spinning sidebands

A

-mistakenly read as peaks in spectra

25
main application of 1D and 2D H-P coupled NMR
-goal was to determine pH of cell tissue samples containing phosphorous compounds
26
issue in determination of pH using 1D H NMR spectrum of biological sample HepG2.2.15
- reagent peak of TMSP was overlapping significant peaks | - presence of water was still apparent and difficult to completely remove
27
how was pH value for hydrogen spectrum in HBV sample obtained
-using 2D H-P HMQC to single out the exact chemical shift value of AMP
28
reagent used to center NMR
3-trimethylsilyl propionic acid sodium salt (TMSP)
29
3 samples used in experiment
- HepG2.2.15 - Urine - Apple Juice
30
pathway for HNCA signal
Hydrogen-Nitrogen-alpha carbon
31
what kind of sample does HNCA examine
proteins
32
when was HNCA developed
1989
33
what dimension experiment is HNCA
3D
34
which is not a problem with the N nuclide that H-N HMBC overcame
short t1 relaxation time
35
what length of bonds between proton and nitrogen do you expect to see with the H-N HMBC
Both 2 and 3 bonds
36
is H-N HMBC proton detected or nitrogen detected
proton detected
37
what benefit did H-N HMBC have on alkaloid analysis
drastically reduced the number of possible structures for the alkaloids
38
why was H-N HMBC important for identifying nitrones rather than H NMR
proton NMR signal of nitrones is hidden under aromatic protons
39
why was there a need for NMR experiment to analyze large biomolecules when x-ray crystallography was already present
-X-ray crystallography only gives a snapshot of molecule and gives no details about interactions with the moelcule
40
How does TROSY help ratio of relaxation times in large biomolecules
-TROSY uses CSA and DD relaxation to its advantage to make T2 times longer to get better peak resolution
41
why were biomolecules over 30 kDa not being analyzed by NMR before 1997
large biomolecules give a lot of resonances which causes signal overlap and a large magnetic field is needed which causes problems with T2 relaxation times
42
Some methods to help the resolution of large biomolecule NMR are
isotope labeling deuteration TROSY NMR
43
TROSY stands for
Transverse Relaxation-Optimized Spectroscopy
44
What instruments does the LC-NMR-MS consist of
- HPLC - NMR - Mass Spec
45
benefits of using a cryoprobe
- increased signal-to-noise ratio - reduction in sample amount - increased sensitivity despite NMR limitations
46
what does a 4-fold increase to signal-to-noise ratio correspond to
-4-fold lower detection limit for a given amount of sample and the experiment time is reduced by a factor of 16
47
pulse wide utilized in APAP experiment using LC-NMR-MS
10.25 microseconds at 18 dB (90 degrees)
48
benefit to coupling an NMR to MS
Heteroatoms such as N, O, and Cl can be observed by MS data