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Flashcards in Final Exam Deck (48):
1

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

2

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

-initial 1JCH coupling in magnetization transfer pathways
-low sensitivity

3

best describes 1,1-ADEQUATE

developed prior to 1, n-ADEQUATE

4

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

5

disadvantage of running 1,n-ADEQUATE

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

6

JRES

2D NMR

7

f1 and f2 axes of JRES spectrum

-coupling on f1 axis, chemical shift on f2 axis

8

main use of JRES spectroscopy

-simplify 1D NMR spectra

9

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

True

10

JRES spectroscopy is limited to:

first order spin systems

11

What does WaterLOGSY stand for

Water-Ligand Observed via Gradient Spectroscopy

12

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

13

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

14

advantage of WaterLOGSY (3)

-detecting ligand binding due to high sensitivity and reliability
-provide structural information
-useful in developmental process of drugs

15

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

Gaussian-shaped saturation pulse

16

size limit of protein that STD-NMR assays

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

17

requirement for ligand size

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

18

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

19

What information can STD-NMR provide

-proximity of the ligand to the protein

20

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

21

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

22

3 methods used to produce sharp peaks in solid state

-Magic Angle Spinning
-Cross Polarization
-Combined Rotation and Multiple Pulse Sequence

23

Why do peaks appear split in solid state NMR

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

24

what is importance of eliminating spinning sidebands

-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