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**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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**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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**NMR properties of selected nuclei**

Nuclear Spin NMR properties of selected nuclei Nucleus I s)-1 rad rel Natural Abundance (%) 1H 1/ x 2H x 13C 1/ x 14N x 15N 1/ x 17O 5/ x 19F 1/ x 23Na 3/ x 31P 1/ x 113Cd 1/ x Atomic nuclei are composed of protons and neutrons which have a spin Protons spin neutrons spin nuclear spin Even even 0 Even odd 1/2 Odd even 1/2 Odd odd n

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**This equation tells us how much magnetism we get for a given spin.**

Gyromagnetic ratio The gyromagnetic ratio g 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 m m =gI This equation tells us how much magnetism we get for a given spin. The gyromagnetic ratio is also known as the magnetogyric ratio

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

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**The Zeeman splitting is therefore**

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

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

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**A compass in a magnetic field**

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**A nuclear spin precesses in a magnetic field**

the circulating motion of the spin angular momentum is called precession this arrow denotes the direction of the spin angular momentum Nuclear spins precess because: they are magnetic they have angular momentum

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**Precession frequency = Larmor frequency**

Larmor frequency in Hz (= cycles per second) n0 = - g Bo/2π magnetic field in Tesla (T) gyromagnetic ratio in rad s–1 T–1 Note – ignore sign difference – this arises from convention and the sign of the precession. Compare with Zeeman Splitting

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**http://www. chm. bris. ac. uk/polyketide/nmr**

Will have Lecture 1 (overheads) Plus Notes on Basic NMR.

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