Modern Approaches to Protein structure Determination

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Modern Approaches to Protein structureDeterminati
on

• 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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Nuclear Spin
NMR properties of selected nuclei
Nucleus I ????s)-1 rad ?rel Natural Abundance
() 1H 1/2 2.6752 x 108 1.00 99.98 2H 1 4.107 x
107 0.15 0.02 13C 1/2 6.728 x 107 0.25 1.11 14N 1
1.934 x 107 99.64 15N 1/2 -2.712 x
107 0.1 0.36 17O 5/2 -3.628 x 107 0.04 19F 1/2 2.
5181x107 100 23Na 3/2 7.080 x 107 100 31P 1/2 1.
0841 x 108 0.41 100 113Cd 1/2 5.934 x 107 12.26
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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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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I1/2
I1
m-1/2
m-1
m 0
m1/2
m1
ground state no field

Zeeman splitting
ground state with field
The Zeeman splitting is therefore
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s-1 (Hz)
Larmor Frequency
rad s-1 T-1.
rad s-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
n0 - g Bo/2p
Larmor frequency in Hz ( cycles per second)
magnetic field in Tesla (T)
gyromagnetic ratio in rad s1 T1
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.htmWill
have Lecture 1 (overheads)Plus Notes on Basic
NMR.