Языки программирования
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Samples of smaller volumes
Samples of smaller volumes
Samples of smaller volumes
Samples of smaller volumes
Samples of smaller volumes
Samples of smaller volumes
Tune and match the probe
Tune and match the probe
Recognizing Bruker probe types
Recognizing Bruker probe types
Recognizing Bruker probe types
Recognizing Bruker probe types
Recognizing Bruker probe types
Recognizing Bruker probe types
Understanding NMR
Understanding NMR
Chemical shifts
Chemical shifts
Chemical shifts of solvents/impurities
Chemical shifts of solvents/impurities
Example: aliasing
Example: aliasing
Scalar coupling (J)
Scalar coupling (J)
Scalar coupling (J)
Scalar coupling (J)
Scalar coupling: simulation helps
Scalar coupling: simulation helps
Example: satellites and spinning side-bands
Example: satellites and spinning side-bands
Lorentzian peak Integration
Lorentzian peak Integration
Lorentzian peak Integration
Lorentzian peak Integration
Multiple chemical environments: chemical or conformational exchange
Multiple chemical environments: chemical or conformational exchange
(N)H line-shape: influence of relaxation and scalar coupling
(N)H line-shape: influence of relaxation and scalar coupling
Examples of (N)H resonance
Examples of (N)H resonance
Examples of (N)H resonance
Examples of (N)H resonance
Examples of (N)H resonance
Examples of (N)H resonance
Improving sensitivity: Ernst angle
Improving sensitivity: Ernst angle
Missing a carbonyl carbon presumably due to insufficient relaxation
Missing a carbonyl carbon presumably due to insufficient relaxation
Solution: Use H2O
Solution: Use H2O
Shaped Pulse Examples
Shaped Pulse Examples
Shaped Pulse Examples
Shaped Pulse Examples
Shaped Pulse Examples
Shaped Pulse Examples
Example: Setting up a Sinc Pulse
Example: Setting up a Sinc Pulse
Example: Setting up a Sinc Pulse
Example: Setting up a Sinc Pulse
Example: a Sinc Pulse (cont’d)
Example: a Sinc Pulse (cont’d)
Example: a Sinc Pulse (cont’d)
Example: a Sinc Pulse (cont’d)
Pulse Simulation
Pulse Simulation
Pulse Simulation
Pulse Simulation
Pulse Simulation
Pulse Simulation
Pulse Simulation (cont’d)
Pulse Simulation (cont’d)
Pulse Simulation (cont’d)
Pulse Simulation (cont’d)
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1NMR Training for Advanced Users. 3731P and 13C can be observed directly on
Huaping Mo Summer, 2009 all PINMRF 300 and 400 MHz instruments
http://www.pinmrf.purdue.edu (please follow local PINMRF instructions)
http://people.pharmacy.purdue.edu/~hmo/ind 13C can be observed on higher fields (500
x.htm. MHz and above), without any cable change
2Overview. Our facility PINMRF: Purdue Drx500-2 with BBO probe offers higher
Interdepartmental Facility sensitivity for 31P, 13C, 15N and most
(http://www.pinmrf.purdue.edu) Staff other heteronuclei (19F excluded) Observed
include John Harwood (director, D.Sc), nucleus needs to be cabled to x-broadband
Huaping Mo (associate director, Ph.D.), pre-amplifier BBO tuning is needed for
Jerry Hirschinger (engineer) and other both proton and observed nucleus Double
members. Our capabilities 800MHz, 600MHz, check filters if re-cabled.
500 MHz (2), 400 MHz(2) and 300MHz (4) 38Direct observe: 31P, 13C or 15N.
Observe almost all NMR active nuclei Satellite peaks can frequently be
Detect as low as 1 mM to as high as 100 M indirectly observed in proton spectrum (so
proton concentrations VT from -80°C to that we know the less sensitive
above 100°C* Many problems can be heteronuclei are there to be observed
converted to and addressed by NMR directly!) Decoupling of proton may
observables! Our expertise Various 1D, 2D improve signal by Sharper peaks NOE Proton
and 3D experiments Novel pulse sequence channel has to be tuned!
development and simulations Structural 39Dipolar coupling: NOE. NOE depends on
determinations Quantitative analysis NMR correlation time (molecule size) and
hardware trouble shooting and repair Our resonance frequency NOE does not always
track record Mo, Harwood et al. J. Magn. enhance the observed signal. 13C. 31P. 1H.
Reson., in press; Ye, Mo et al. Anal. 15N. Molecule size. Temperature.
Chem. 2009; Mo & Raftery Anal. Chem. 40NOE implication in Quantification. The
2008; Bai, Mo, Shapiro, Bioorg Med Chem, observed nucleus should be free of
2008; Mo & Raftery J. Bio. NMR, 2008; interference from other nuclei
Mo & Raftery J. Magn. Reson. 2008 Pre-saturation in aqueous samples may not
Acknowledged in a number of publications be appropriate for accurate quantification
(Thank you!) Determined the structures for Small molecules tend to gain signal size
a series of novel natural products / due to positive NOE from saturated water
metabolites. Large molecules tend to lose signal size
3A schematic Diagram for NMR. R. g(RG). due to spin diffusion.
receiver gain function. receiving 41Improving sensitivity: receiver gain.
efficiency. NMR signal: A = A0 * h * c * V Receiver gain needs to be maximized which
*R *sin(q)*I(q)*g(RG). excitation. t90. frequently requires good water suppression
Mz. transmitter. probe tuning network. q. Avoiding excessive large receiver gain
receiver. observation. pulse sequence. (for signal clipping) Excessive
pulse calib/angle q. RF properties; I(q). acquisition time may end up with spending
spectral analysis. spectral processing. time collecting noise and down-grade
Shims; chemical shift; coupling; signal-to-noise ratio.
line-shape; relaxation; exchange; h, c 42Improving sensitivity: Ernst angle.
& V. © Huaping Mo, 2009. raw FID. FT. Acquire more scans in a given amount of
FID. ADC. time Use Ernst angle a for excitation: cos
4Insider scoops: a systematic approach a = exp(-Tc/T1) Increase concentration and
for NMR quantitation. Receiving efficiency lower the solvent / salt amount. Tc/T1.
(Mo et al. J. Magn. Reson. in press) sensitivity. Pulse angle (degrees).
conceptually, it is similar to extinction 43Missing a carbonyl carbon presumably
coefficient in UV spectroscopy in due to insufficient relaxation. About 5 mg
characterizing how efficient a unit in CD3OD. 2800 scans (~4 hrs). ? Missing a
magnetization can be detected Receiving carbonyl.
efficiency can be pre-calibrated as a 44Solution: Use H2O. Why it works:
function of 90° degree pulse length Carbonyl 13C is reduced due to presence of
receiving efficiency is the same for all a proton rich environment in H2O.
nuclei of the same type (indifferent to Potential intra-molecular hydrogen bond is
chemical shifts) in the same sample weakened or broken, and decoupled from
Receiver gain function (to be submitted) ring movement. In H2O:D2O (1:1). 1400
how much gain is actually achieved by the scans (~2 hrs).
receiver Solvent signal offers a universal 451D acquisition for very long hours.
and robust concentration internal standard Helpful Split long experiments into
(Mo & Raftery Anal. Chem. 2008) smaller blocks and save data regularly
Normalized NMR signal size is strictly (multiple data can always be summed if
proportional to the concentration for a needed): multizg Dissolve the compound in
given sample, regardless how concentrated water (H2O) might be helpful (shorter
or dilute the sample is Unit magnetization relaxation time) Lower sample temperature
generates the same amount of total NMR may help Not helpful Save several days’
response in the RF coil, which is data into one single FID Use 300 ul or
indifferent to chemical shift or less volatile solvent.
line-shape No need to make additional 46Chemical shift referencing. 1H
internal or external standard. chemical shift can be readily referenced
5Common Misconceptions. You need to by the solvent signal or TSP/TMS
prepare either an internal or external Heteronuclei can be indirectly referenced,
concentration reference for quantitative by PROTON chemical shift! No need to have
NMR You need a chemical shift referencing a separate internal or external reference.
compound in a hetero-nuclear spectrum A 47From 1D to 2D. FT. 1D. t2. w1. time
compound has to be in a deuterated solvent domain. frequency domain. FT(t2). FT(t1).
to be observed by NMR You need to separate 2D. w1. t1. t1. t2. w2. w2. frequency
the compound to find out if it is right or domains. time domains.
how much is there. 482D NMR. Correlate resonances through
6Outlines for this talk. Basic bond or space COSY: coupling Magnitude
preparations for NMR: safety, sample, mode recommended. 1 mg or less will do
lock, shim and tune Understanding NMR: Minutes to a couple of hours TOCSY:
excitation and observation RF pulse coupling network ~ 70 ms mixing time 1 mg
calibration Data acquisition: sweep width, or less will do An hour or longer NOESY /
carrier freq. and # of scans etc. NMR ROESY: distance / NOE Mixing time ranging
observables: Chemical shift, scalar from less than 100 ms (proteins) to 500 ms
couplings, NOE and relaxations Chemical (small molecules) 1 mg or more Hours or
shift referencing Introduction to basic longer HSQC/HMQC: proton correlation to X,
2D's Simulations for spin systems, pulses typically through one-bond scalar
and sequences Basic operation couplings (two or three bond correlation
demonstrations. possible) 1mg or less will do An hour or
7Sample. RF coil. Basic requirements: longer HMBC: proton correlation to X,
Proton observe: 1 uM or more Cabron through multiple bond scalar couplings 1
observe: 1 mg or more Volume: 300 ul or mg or more Hours or longer.
more Solvent: most solvents will do;10% 492D NMR. Resolve overlapping peaks
deuterated solvent is sufficient for Resolution is provided largely through the
locking Spectrometers can be run without indirect dimension No need to have highest
lock (deuterium). Rule #1: for Bruker NMR resolution in the direct detected
spectrometers, the NMR tube insert cannot dimension Limit direct acquisition time to
exceed max depth (19mm or 20mm) from the 100ms or less if heteronuclear decoupling
center of the RF coil Longer insert than is turned on Lower decoupling power if
recommended may present problems for the longer acquisition time is needed Change
probe, as well as cause frictions during in experimental conditions may help.
spinning Varian is more flexible in 502D NMR essentials: acquisition. Proton
allowing longer insert Rule #2: center of tuning and matching Calibration of proton
NMR sample should be as close as possible (90 degree) pulse length Standard pulse
to the center of RF coil. Normal sample lengths can be used if the solution is not
needs to about 500 ul or slight more Too highly ionic (< 50 mM NaCl equivalent)
much solvent is a waste! Too little All proton pulses are likely getting
solvent may make shim difficult, but it longer if the solution is ionic and/or the
does work! ~18mm. Coil Center. ? 20mm. probe is not tuned Modest receiver gain rg
8Samples of smaller volumes. Follow about half of what rga gives or less
rule # 1 and then rule #2 Shimming might Carrier frequency (center of spectrum in
be challenging due to air/glass and Hz) and SW (sweep width) in both
air/solution interfaces Bubbles should be dimensions (avoid aliasing unless intended
avoided Consider Shigemi tubes Be careful to) Number of scans (NS) The pulse program
with spinning Non-spinning is recommended recommends NS (a integer times 1, 2, 4, 8
for volume ~ 300 ul or less 500 ul is or 16) Needs some dummy scans, especially
sufficient for a regular tube. 300ul. with decoupling / tocsy Number of
400ul. 500ul. increments in the indirect dimension (td1)
9Sensitivity for smaller volumes. Larger td1 improves resolution in the
Volume less than 300 ul may not offer indirect dimension Rarely exceeds 512
additionally sensitivity improvement over (except occasionally in COSY Detection
that achieved by 300 ul, if the total method in the indirect dimension
amount of analyte is constant For a Determined by the pulse program Typically
regular tube, larger volume helps is either states (and/or TPPI) or
shims/line-shape, but not sensitivity echo-antiecho Acquisition time (aq) less
directly. than 100 ms with decoupling Modest
10Tune and match the probe. Why do we gradients (cannot be more than the full
need tune and match (wobb)? For best power of 100% and typically less than 2 ms
pulses and sensitivity Only higher fields in duration) Go through the pulse program
(500, 600 and 800 HMz) in our facility if you really care.
need tuning Lower field probes have been 512D processing. Window functions Allow
tuned! Most of the time only proton FID to approach zero at the end of the
requires tuning Drx500-2 with BBO needs acquisition time Sine bell functions with
special attention Proton always needs some shifts are recommended most of the
tuning BB (used for 13C or 31P etc) time Zero filling Typically double data
channel needs tuning, by first setting the points in each dimension Phasing Indirect
numbers to the pre-set values. RF dimension 0th and 1st order corrections
reflection. tune. match. Frequency. are recommended in the pulse program. If
Carrier frequency. not, use 0 for both to start with. First
11Significance of tuning/matching. data point is typically scaled by 1 or
Shorter 90° pulse More efficient use of RF 0.5, depending on the pulseprogram Direct
power Protects transmitter More uniform dimension’s 1st order phase is rarely more
excitation in high power Better than 50 degrees. 0th order can be anywhere
sensitivity Reciprocity: if excitation is from 0 to 360 degrees Phase in the 2D mode
efficient, then detection is equally for best appearance Referencing Can be
efficient Potentially quantitative: NMR done by picking a known resonance in the
signal size is about inversely spectrum by (external) protons.
proportional to the 90° pulse length. 52HSQC: a Block Diagram. Magnetization
12Recognizing Bruker probe types. transfer pathway: F1(H) -> F2(X) ->
magnet. BBO probe on drx500-2. TXI probe. F2(X,t1) -> F1(H) -> F1(H,t2). 90.
Side-view. Side-view. 1H tuning/matching 180. H. 90? 180. X. dec. acq. States: ?=x
rods are labeled as yellow. Bottom-view. and ?=y are acquired for same t1 and
Do not touch those! Dials for broadband treated as a complex pair in Fourier
(BB) tuning/matching. Tabulated values for transform. No need to change receiver
BB tuning/matching. BB Dialing stick. phase TPPI: ?=x, y, -x and –y are acquired
13Lock. Lock depends on shims: bad shims sequentially in t1, and receiver phase is
make bad lock Initialize shims by reading incremented too. Real Fourier transform.
a set of good shims (i.e. rsh shims.txi) 1/4J. 1/4J. 1/4J. 1/4J. t1/2. t1/2.
Inheriting a shim set from previous users 53HMQC or HSQC. Magnitude HMQC (9 mins)
may present difficulties Unusual samples Easy set up and slightly higher
(esp. small volumes) may need significant sensitivity. Phase sensitive HSQC (18
z1/z2 adjustments Use “lock_solvent” or mins) Better resolution. codeine. adapted
“lock” command The default (Bruker) from acornnmr.com.
chemical shift may appear as dramatically 54HMQC and HSQC comparison. HMQC Fewer
changed if the spectrometer assumes pulses More tolerant to pulse
another solvent Avoid excessive lock power mis-calibrations Allows homonuclear
Lock signal may go up and down if lock (proton) coupling in the indirect
power is too high due to saturation of dimension. HSQC More pulses Less tolerant
deuterium signal Apply sufficient lock to pulse mis-calibrations No homonuclear
power and gain so that lock does not drift (proton) coupling in the indirect
to another resonance (this may happen by dimension.
auto-lock if multiple deuterium signals 55Data Presentation. Processed data can
exist). be readily viewed, manipulated and printed
14Shims. The goal of shimming is to make by xwinplot (wysiwyg) Xwinplot can readily
the total magnetic field within the active output .png, .jpg or .pdf files for
volume homogeneous (preferably <1Hz). publications or presentations Files can be
Total magnetic field = static field transferred through secure ftp.
(superconductor) + cryoshim (factory set) 56Pulse sequence: the heart and soul of
+ RT shim (user adjust) + lock field NMR. 90x. 180x. 1H. 90-x. 90-x. G. On-res:
Shimming can be done either manually or by dephased by two gradients Off-res:
gradient, which can be very efficient and refocused by two gradients. Delay only; be
consistent if done properly Sample very careful with critical command in a
spinning may improve shims However, labeled line. label. Delay. define f1
spinning-side bands appear power level. 90° pulse on f1. Gradient
Recommendations: Start from a known good pulse. Shaped 90° pulse. Acq. and go to
shim set (by rsh on bruker or rts on label 2. Write to disc. And go to label 2.
varian). Do not inherit shims from other Phases. ;zggpwg ;this is a bruker sequence
users unless you know they’re good prosol relations=<triple> #include
Non-spinning and higher order (spinning) <Avance.incl> #include
shims should not change dramatically from <Grad.incl> "d12=20u" 1 ze
sample to sample for most applications. 2 30m d1 10u pl1:f1 p1 ph1 50u UNBLKGRAD
15Lock: lock gain. recommended. not p16:gp1 d16 pl0:f1 (p11:sp1 ph2:r):f1 4u
recommended. higher lock gain. Lower lock d12 pl1:f1 (p2 ph3) 4u d12 pl0:f1 (p11:sp1
level due to lower lock gain. may easily ph2:r):f1 46u p16:gp1 d16 4u BLKGRAD go=2
lose lock; change in lock level (during ph31 30m mc #0 to 2 F0(zd) exit ph1=0 2
shimming) is less visible. ph2=0 0 1 1 2 2 3 3 ph3=2 2 3 3 0 0 1 1
16Lock: avoid high lock power. Bad lock. ph31=0 2 2 0 ;comments for parameters…
Good lock. Lock power okay. Lock power too 57Where Things are: Bruker File
high. unstable and lower lock signal. Structure. User NMR data
17Evaluate shims. Look for a sharp peak /u/data/username/nmr Pulse programs
No clear distortion Full width at half /u/exp/stan/nmr/lists/pp Gradient programs
height should be about 1 Hz or less for /u/exp/stan/nmr/lists/gp Shaped pulses
small molecules Small (1% or smaller) or /u/exp/stan/nmr/lists/wave decoupling
free of spinning side-bands Check if peak /u/exp/stan/nmr/lists/cpd Frequency(f1)
distortions are individual or universal lists /u/exp/stan/nmr/lists/f1 Parameter
Make sure that phasing is not causing peak sets /u/exp/stan/nmr/par Shim sets
distortions Maximize the lock level Higher /u/exp/stan/nmr/lists/bsms Macros
lock level => better shim Lock level /u/exp/stan/nmr/mac.
does not drop significantly when spinning 58Gradients. Homospoil gradients Size of
is turned off Small (<1%) or no duration may not matter much Stronger ones
spinning side-bands. tend to clean up unwanted magnetization
18Shim by line-shape. make z4 smaller better Gradient echoes: Exact ratios
first. z4 too small. z4 too big. Plot made between multiple gradients must follow
by G. Pearson, U. Iowa, 1991. Diffusion loss must be considered for
19Understanding NMR. Modern NMR spectrum small molecules, especially during long
is an emission spectrum Equilibrium state echoes Log of signal size is proportional
Magnetization is along +z axis It is to -g2g2d2D.
desired to have the largest +z 59Simulations. Can be easily performed
magnetization prior to excitation for pulses, spin-systems or pulse
Excitation by a RF pulse A projection of sequences Save experimental time Enhance
magnetization is made on xy plane It is our understanding of NMR Most frequently
desired to have the largest xy plane used for shaped pulses.
project for observation Observation 60Shaped Pulse: What and Why. What
Precession of the projected xy- plane Narrow sense: amplitude modulation only,
magnetization. while phase is constant Broad sense:
20RF pulses. RF pulse manipulates spins amplitude and phase modulation Why To
Important in excitation and decoupling achieve perturbation over a certain
Defined by length, power and shape RF frequency range (uniform and selective)
power is expressed in decibels Bruker Narrow bandwidth: shaped pulse. e.g.
Power range: typically 0db (high power) to Gaussian Wide bandwidth: adiabatic pulse.
120db (low power) Varian: Coarse power: 61How is Shaped Pulse Different.
typically 60db (high) to 0db (low); 1 db Composite pulse is typically a block of
increment; absolute Fine power: 4095 square pulses with constant phases Pulse
(high) to 0 (low); default is 4095; integration does not correlate with pulse
relative e.g. 54.5db can be roughly angle Pulse calibration come from
achieved through setting coarse power to individual component Adiabatic pulse
55 and fine power to 3854. sweeps frequency (phase has strong time
21RF pulse calibration. Hard pulse (high dependence) Pulse integration does not
power pulse) can be calibrated directly or correlate with pulse angle Pulse
indirectly For best calibrations, pulses calibration depends on sweep range, and
need to be on resonance (know the chemical somewhat on adiabaticity too Simple shaped
shift or resonance frequency!) Soft or pulse can be calibrated by integration
shaped pulsed can be first calculated and Caveat: a 180° pulse is not necessarily
then fine-tuned to optimum Shapetool (by twice of a 90° pulse Some shaped pulses
Bruker) or Pbox (by Varian) can be used are good for 180° inversions (z -> -z)
for calculation and simulation Be aware of while others are good for 90° excitations
possible minute phase shift (several (z -> x/y).
degrees for soft pulses), which can be 62Shaped Pulse Examples. Square pulse:
critical in water flip back or watergate. simplest shaped pulse; good for simple
22Proton pulse calibration. Most hard hard excitation Gaussian and Sinc: good
(highest power) 90° pulses are typically selectivity; for proton Gaussian cascade:
from 5 us to 20 us. High power pulse for G4, G3, Q5 and Q3; for carbon G4 for
proton (or other heteronuclei if excitation G3 for inversion Q5 for 90° Q3
sensitivity is sufficient) is directly for 180°. Gauss. Sinc1. G4. G4: four
calibrated 360° method (not quite Gaussian lobes.
sensitive to radiation damping or 63Choosing Shaped Pulses. Define the
relaxation) 180° method. 90? 180? q. 270? goal excitation, inversion or refocusing
360? 90? 360? 450? 180? 270? First pulse length or power level Rule of thumb:
with 2 us; 2 us increment. bandwidth is ~ 1/P360 or RF strength (for
23NMR observables. Chemical shifts square pulses) shape Power requirement
Expressed in ppm; reflects chemical peak power may not exceed certain level
environment Scalar couplings Expressed in Length requirement Be aware of probe limit
Hz; causing splitting / broadenings in 1D on length in case of high power While
2D or nD bond correlations NOEs / longer pulses tend to have better
relaxation / line-shapes Reveals selectivity, relaxation / scalar coupling
distance/conformation information Peak may limit pulse length Run pulse
size Potentially useful in quantitative simulation and calculation Bandwidth needs
analysis. to be first satisfied Simulated frequency
24Chemical shifts. Reflects chemical profile is to have top-hat behavior Phase
environment: Ring current effect Outside: needs to be linear in the region of
high ppm Inside: low ppm Effect of interest.
electron withdrawing groups Donating: low 64Shaped Pulse Calculation. Rule of
ppm Withdrawing: high ppm. thumb: 6db change in power results two
25Chemical shifts of fold change in pulse length DdB = 20 log
solvents/impurities. Gottlieb et al. JOC (P90/P90ref) e.g. 10us @0db => 20us
1997. @6db for the sample pulse angle For a
26Example: aliasing. okay. sw=16ppm. shaped pulse with a imperfect linear
aliased. (from arx300) aliased from 0 ppm amplifier, DdB = 20 log
with phase distortion, because the peak is (P90*shape_integ/P90hard*comp_ratio)
out of the “detection window”. Oversampled Modern spectrometers have comp_ratio close
proton spectrum on higher fields (500 – to 1 Adiabatic pulses require different
800 MHz) does not have the aliasing issue: treatments.
peaks outside of sw will disappear. 65Example: Setting up a Sinc Pulse.
27Spectral aliasing (cont’d). In direct Within xwinnmr, launch shape tool by
observe dimension, spectral aliasing is typing “stdisp” or from menu Within shape
generally avoided by either increasing tool, choose shapes -> sinc. Change
spectral width (sw) or moving center lobe number to 1 and click “OK” On the
frequency (sfo1) Sometimes the indirect left is the amplitude profile (sinc shape)
detection dimension (in nD spectrum) may and (constant) phase is shown on the
intentionally adopt aliasing to improve right.
resolution in that dimension. 66Example: a Sinc Pulse (cont’d). Within
28Scalar coupling (J). Scalar coupling: shape tool, choose analyze -> integrate
proportional to gyromagnetic ratio through pulse. Make necessary updates. In this
bond/electrons split into 2nI + 1 lines. particular case, we assume the reference
29Scalar coupling: simulation helps! is 9.5 us @1.5db and you wish to calculate
pro-chiral! a. 8Hz. 12Hz. b. 8Hz. These for 1000us 90 degree pulse. Then click OK
are not impurities! ssb. Ha and Hb are not The power level is calculated as 35.8db
exactly equivalent, with chemical shift compared with the reference. Click “seen”
difference of 0.025ppm. simulated. If satisfied, you can save this shaped
Observed at 300 MHz. pulse under /u/exp/nmr/stan/lists/wave/.
30Example: satellites and spinning Go back to xwinnmr->ased, and update
side-bands. 6.6 Hz; 29Si satellites; 2.3% the sinc1 shaped pulse as pulse length of
each. ssb: 20 Hz or multiple of 20Hz from 1ms, and power level to be 35.8 + 1.5
center. ~120 Hz; 13C satellites; 0.55% (since reference 9.5us is @ 1.5db) =
each. TMS. 37.3db If needed, the shaped pulse power
31Relaxation. T1 relaxation allows can be fine tuned by gs, or a careful
magnetization to recover back to +z axis calibration.
Nuclei with larger gyromagnetic ratios 67Pulse Simulation. Within shape tool,
(resonance frequencies) tend to relax choose analyze -> simulate. Update the
faster 1H: 0.1 – 10 s (proteins have short length as 1000us and rotation angle as 90
T1’s) 13C, 15N, 31P: much longer than 1H (for sinc1 we just set up). Click “OK”. A
Nuclei in a proton rich environment tend new Bloch module will show default (x,y)
to relax faster T2 relaxation contributes profile for excitation. Click on z to view
to the observed resonance line-shape T2~T1 z profile. z.
for small molecules Line-width offers an 68Pulse Simulation (cont’d). If you
estimate of T2. decide that the starting magnetization is
32Line-shape. FWHM (2?). Lorentzian: x, you can click (in Bloch module)
A(w)= ? / (?2 + (?-?0)2) 2?=1/(pT2*). Full “calculate”->”excitation profile”.
Width at Half Maximum is 1/(pT2*) Hz, with Change initial Mx to 1 and Mz to 0. Click
T2* as apparent spin lattice relaxation “OK” and then the excitation profile will
time Magnetic inhomogeneity (shim) can be updated. If you wish to examine
increase FWHM (2l) or distort the trajectory (how a magnetization at a given
line-shape (reduce T2*) T1 > T2 > frequency responds to the sinc1 pulse),
T2* Small molecules 1H: T1 ~ T2 in the you can click “time evolution”, and update
order of seconds 13C: seconds to tens of initial values etc (may not allow too many
seconds; even longer if no proton attached steps). Click “OK”.
(CO and quaternary) Large molecules 1H: T1 69Demo. Sample preparation; Shigemi tube
~ T2 hundreds of mini-seconds or shorter Lock and shim Tune and match Calibration
13C: seconds or sub-seconds. of 90° pulse Water suppression Calculation
33Lorentzian peak Integration. / simulation of pulses Set up 1D and 2D’s:
integration. n. n (2l). -n (2l). 0. mutizg; COSY and HSQC Data processing:
34Multiple chemical environments: addition and subtraction Data
chemical or conformational exchange. presentation: xwinplot.
Fundamentally, chemical shift reflects 70Backup slides.
chemical environment surrounding a 71Safety. Personal safety Cryogens: do
nucleus’ Multiple chemical environments not lean on or push magnets Cryoprobes:
may alter chemical shift or even cause avoid contact with transfer line Magnetic
significant peak broadening. Fast and RF hazards Instrument safety Know the
exchange. slow exchange. Jin, Phy. Chem. limits of instruments and be conservative
Chem. Phys. (1999). Probe limits: avoid excessive long
35(N)H line-shape: influence of decoupling, hard pulses or their
relaxation and scalar coupling. In equivalents Double check pulse program and
addition to chemical exchange, (N)H proton parameters for any non-standard new
line-shape is also influenced by the experiment. Pay special attention to power
coupled nucleus 14N. Slow 14N relaxation switch statements in the pulseprogram Data
(compared to JNH). medium14N relxation. Safety Back up data promptly and regularly
Fast relaxation. JNH ~65 Hz. this might be Data processing or manipulation has no
the very reason why CHCl3 proton appears impact on the raw (FID) data Do not change
as a singlet though JH-35Cl and JH-37Cl parameters after data are acquired.
exist. 72Xwinnmr: Spectra addition/subtraction.
36Examples of (N)H resonance. 800MHz. Operations on processed data (spectra)
500MHz. 300MHz. 14N decoupling. no 14N have no impact on raw data edc2: define
decoupling. Hz. NH4Cl in DMSO. Triplet is 2nd dataset (to be compared) and 3rd
due to 14N coupling (52 Hz). Urea in water dataset (to save results into) dual: allow
(6% D2O). comparison.
37Direct observe: 31P, 13C or 15N. 19F,
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