Lecture 1 Zhenming (Jimmy) Du GSU Chem 4050/6050 Lecture 1 Zhenming (Jimmy) Du

Round Robin Instructor: Dr. Zhenming (Jimmy) Du NSC 134A Email: zdu@gsu.edu Phone: 404-413-5538 Website: sites.gsu.edu/zdu Students:

Scope of Chem 4050/6050: Level I Chem 4050/6050. Introduction to Fourier-Transform NMR Spectroscopy. Prerequisites: demonstrated research need and approval of the departmental chair. Introduction to techniques of Fourier-Transform Nuclear Magnetic Resonance Spectroscopy

Next step: Level II Fall Semester Chem 8450, NMR Spectroscopy (4) Prerequisite:  Chem 6050 or consent of the instructor.  Theory and application of NMR spectroscopy for the characterization and elucidation of organic and biological molecules.

Next step: Level III Spring semester: Chem 8540. Biomolecular Nuclear Magnetic Resonance. (3) Prerequisite: Introductory courses in spectroscopy, such as Chem 4050/6050 and Chem 4190/6190 or equivalent. Some experience in the application of quantum mechanics in spectroscopy is useful, but not essential. Experimental design and interpretation of nuclear magnet resonance data, particulary with respect to applications in structural biology.

Textbook required Edition: 2nd ISBN-13: 978-0198703419

Helpful Books This text is aimed at people who have some familiarity with high-resolution NMR and who wish to deepen their understanding of how NMR experiments actually ‘work’. This revised and updated edition takes the same approach as the highly-acclaimed first edition. The text concentrates on the description of commonly-used experiments and explains in detail the theory behind how such experiments work. The quantum mechanical tools needed to analyse pulse sequences are introduced set by step, but the approach is relatively informal with the emphasis on obtaining a good understanding of how the experiments actually work. The use of two-colour printing and a new larger format improves the readability of the text. 

Helpful Books This work-book will guide you safely, in step-by-step descriptions, through every detail of the NMR experiments within, beginning with 1D routine experiments and ending with a series of advanced 3D experiments on a protein:

Topics today NMR Basics: Theory for NMR detection; Concerns during NMR detection. Reading assignment: Lecture 1 notes; Chapter 1 & 2; Read gsuNMR guide before lab 1; Reading NMR operation procedures before lab 1.

1. What is NMR? NMR = Nuclear Magnetic Resonance

About MRI (N)MRI = (Nuclear) Magnetic Resonance Imaging

NMR Applications

NMR Applications

Organic Structure Illustration:Heparin Proton NMR profiles: (a) Oversulfated heparan sulfate. (b) 30% oversulfated heparan sulfate + 70% heparin. (c) Heparin. (d) Contaminated heparin lot 2004-5, which had both oversulfated heparan sulfate and 5% galactosamine-containing GAGs that were undetectable by NMR. (e) Oversulfated heparin by-product. (f) A mixture of 50% oversulfated heparin by-product and 50% heparin. (g) Contaminated heparin lot 2007-26. OSHS, heparin oversulfated by chemical sulfation; OSDS, dermatan oversulfated by chemical sulfation; OSCS, chondroitin oversulfated by chemical sulfation; *, oversulfated heparan sulfate.

Protein Structure Illustration 2LCJ CFPGDTRILVQIDGVPQKITLRELYELFEDERYENMVYVRKKPKREIKVYSIDLETGKVVLTDIEDVIKAPATDHLIRFELEDGRSFETTVDHPVLVYENGRFIEKRAFEVKEGDKVLVSELELVEQSSSSQDNPKNENLGSPEHDQLLEIKNIKYVRANDDFVFSLNAKKYHNVIINENIVTHQ Du, Z.,  Liu, J.,  Albracht, C.D.,  Hsu, A.,  Chen, W.,  Marieni, M.D.,  Colelli, K.M.,  Williams, J.E.,  Reitter, J.N.,  Mills, K.V.,  Wang, C. Journal: (2011) J.Biol.Chem. 286: 38638-38648

Nuclear=? Atoms are made of electrons and nuclei. Each atomic nucleus has four important physical properties: mass, electric charge, magnetism, and spin. Mass, electric charge: more sensible Nuclear magnetism and spin: less tangible ( but need to understand here)

Quantum mechanics treatment Nucleus have four quantum numbers(n,l,ms,s) n: Principle quantum number(n): the size of the orbital (1,2,3,…,n) l: Angular quantum number (l): the shape of the orbital (0, 1, …, n-1)(s,p,d,f,…) ms: Magnetic quantum number(m):orientation in space of a particular orbital [-l, …,-2,-1,0,1,2,…,l] s: Nucleus has an intrinsic spin angular momentum ( hence spin quantum number, I).

Nuclear Spin Some nuclei possess an intrinsic angular momentum Nuclear spin angular momentum is quantized in integer multiples of h/2π(or h is Planck’s constant) Maximum observable component p of nuclear spin angular momentum is p= I * h/2 π I = nuclear spin quantum number I varies as a result of the interactions between protons and neutrons

Nuclear spin differs from electron spin both quantized, I ≠ 0: Nmrable

Nuclear spin differs from electron spin both quantized, I ≠ 0: Nmrable Nuclide 12C 16O 1/2 1H 13C 15N 19F 29Si, 31P 1 2H 14N 3/2 11B 23Na 35Cl 37Cl 5/2 17O 27Al 3 10B

Example: ν = γ * B0/ 2π For proton , γ = 26.7519 * 107 rad T-1 S-1 For carbon, γ = 6.73 * 107 rad T-1 S-1 T: Telsa = 10,000 Gauss B0= 9.40T, corresponds to 400MHz NMR for proton. corresponds to NMR for carbon. B0= 11.45T, corresponds to NMR; Bo = , corresponds to 600 MHz NMR; Commercially available magnetic field 1.4T------23.5T 60MHz-1GHz This lies on the radiofrequency range (RF) of the electromagnetic spectrum.

Resonance along is not enough Detecting the resonance is the key!

Low energy range! Radio frequency range!

At room temp, the number of spins in the lower energy level (N+)is slightly greater than the number in the upper level (N-).

The Boltzmann Factor and Partition Functions The Boltzmann factor tells us that if a system has states with energies E1, E2, E3,. …, the probability Pj that the system will be in the state with energy Ej depends exponentially on the energy of that state, or Pj ∝ 𝑒 −𝐸𝑖/𝐾𝑏𝑡 At room temp, the number of spins in the lower energy level (N+)is slightly greater than the number in the upper level (N-).

NMR Detection Key Elements A strong magnetic field; RF pulse to excite nuclei in the sample; Detection of the feedback (NMR signal).

A strong magnetic field; Superconducting solenoid;

2. RF pulse Δ𝐸=ℎ𝑣=γ ℏ𝐵 0 Twist between 𝑣 and 𝐵 0 to achieve balance; For protons, if you supply a magnetic field B0, then all protons will appear in the same frequency 𝑣 as γ 𝑎𝑛𝑑 ℏ 𝑎𝑟𝑒 𝑎𝑙𝑙 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡𝑠?.

• 1926 Pauli’s prediction of nuclear spin! Two or more identical fermions cannot occupy the same quantum state within a quantum system simultaneously. It is impossible for two electrons to have the same values of the four quantum numbers: n, ℓ, angular momentum quantum number, mℓ, the magnetic quantum number, and ms, the spin quantum number.

• 1932 Detection of nuclear magnetic moment by Stern using molecular beam!

– 1936 First theoretical prediction of NMR by Gorter; his attempt to detect the first NMR did not work (LiF &K[Al(SO4)2]12H2O) at low temp.

– 1938 Isidor Rabi discovered NMR.

• 1945 First NMR of solution (Bloch et al for H2O) and solids (Purcell et al for parafin)!

• 1949 Discovery of chemical shifts!

2014 Varian is gone after 50 years.

2014 Varian is gone after 50 years.

2014 Varian is gone after 50 years.

2014 Varian is gone after 50 years.

Relative sensitivity S/N ∝ γ3 Absolute Sensitivity S/N ∝ γ3 * C NMR Sensitivity. Relative sensitivity S/N ∝ γ3 Absolute Sensitivity S/N ∝ γ3 * C C stands for natural abundance.

Pulse NMR is fast 20ppm at 400MHz= 8000Hz, 125us for 360 pulse

What about a spectrum between 40ppm and -10 ppm? Exercises Now you are running NMR on 500Mhz NMR, and you found your 90 pulse for proton is 12 μs long. Your lab mate told you he has peaks that appears between 5 ppm and 0 ppm. Is the pulse strong enough to cover that range? What about a spectrum between 40ppm and -10 ppm?

RF Pulses

3. Chemical Shift Earth’s magnetic field 0.6 Gauss at equator Refrigerator magnet 100 - 150 Gauss MRI medical scanners 0.3 - 1.5 Tesla (3 - 15,000 G) High field NMR magnet 200 MHz 4.7 Tesla (47,000 G) 400 MHz 9.4 Tesla (94,000 G) 500 MHz 11.7 Tesla (117,000 G) 800 MHz 18.8 Tesla (181,000 G)

Proton peaks are isolated

Chemical Shift 𝐵 𝑙𝑜𝑐 = 𝐵 0 (1-σ) More electron, less Bloc, smaller frequency.

Chemical Shift

Chemical Shift

Chemical Shift CH4 CH3Cl CH2Cl2 CHCl3 δ=0.23 δ=3.05 δ=5.33 δ=7.26 CH3I CH3Br CH3F δ=2.16 δ=2.68 3.05 4.26

Chemical Shift

Chemical Shift

Advantage of FT-NMR vs. CW Faster speed. No sweeping needed. 1 s/ scan vs. 4500s / scan Multiple scan to improve S/N; Spin Manipulation for complicated NMR experiments, such as water suppression, NOESY, and HMBC.