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1 Modern Approaches to Protein structure Determination 1. Introduction to NMR. 2. Solving Protein Structures by NMR - The features of a 1D spectrum - what can we tell? The need for 2D 3. 2D NMR - How NMR works through space not just bonds - we need this to solve structures. The move to the third dimension 4-5. Modern methods for structure determination 6. Comparison of techniques and New developments

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2 Why study protein structure? The more we understand about a protein and its function, the more we can do with it. It can be used for a new specific purpose or even be redesigned too carry out new useful functions (biotechnology & industry). We can use this knowledge to help understand the basis of diseases and to design new drugs (medicine & drug design). The more knowledge we have how proteins behave in general, the more we can apply it to others (protein families etc) Structure determination of biomacromolecules by NMR -no crystal needed, native like conditions -bandshift assays -Dynamics -Size limitations Complex, could be the active form

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3 Nuclear Spin Atomic nuclei are composed of protons and neutrons which have a spin Protons spin neutrons spinnuclear spin Eveneven0 Evenodd1/2 Oddeven 1/2 Oddoddn NMR properties of selected nuclei NucleusI s) -1 rad rel Natural Abundance (%) 1 H1/22.6752 x 10 8 1.00 99.98 2 H14.107 x 10 7 0.150.02 13 C1/26.728 x 10 7 0.251.11 14 N11.934 x 10 7 99.64 15 N1/2-2.712 x 10 7 0.10.36 17 O5/2-3.628 x 10 7 0.04 19 F1/22.5181x10 7 100 23 Na3/27.080 x 10 7 100 31 P1/21.0841 x 10 8 0.41100 113 Cd1/25.934 x 10 7 12.26

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4 The gyromagnetic ratio determines the ratio of the nuclear magnetic moment to the nuclear spin. It is a fundamental property of each nuclear isotope Fundamental symmetry theorems predict that spin and magnetic moment are co-linear Gyromagnetic ratio The gyromagnetic ratio is also known as the magnetogyric ratio = I This equation tells us how much magnetism we get for a given spin.

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5 the energy of the state with quantum number I z is given by Zeeman splitting Planck constant gyromagnetic ratio Energy of interaction is given by E=-.B in a magnetic field B. The dot product tells us the energy depends on the size and relative orientation of B and. We take B o to be along the Z axis, so the dot product becomes E=- z B z(o) (i.e. x B z and y B z = 0)

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6 m=-1/2 m=+1/2 I=1/2 m=-1 m=+1 I=1 m= 0 The Zeeman splitting is therefore ground state; no field ground state; with field Zeeman splitting Energy

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7 rad s -1 rad s -1 T -1. T s -1 (Hz) Larmor Frequency

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8 A compass in a magnetic field

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9 A nuclear spin precesses in a magnetic field the circulating motion of the spin angular momentum is called precession Nuclear spins precess because: they are magnetic they have angular momentum this arrow denotes the direction of the spin angular momentum

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10 Precession frequency = Larmor frequency 0 = - B o /2π Larmor frequency in Hz (= cycles per second) gyromagnetic ratio in rad s – 1 T –1 magnetic field in Tesla (T) Compare with Zeeman Splitting Note – ignore sign difference – this arises from convention and the sign of the precession.

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14 http://www.chm.bris.ac.uk/polyketide/nmr.htm http://www.chm.bris.ac.uk/polyketide/nmr.htm Will have Lecture 1 (overheads) Plus Notes on Basic NMR.

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