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SUMMARY:β-Amyloid\, Sub-terahertz Microwaves and the Magic Angle
DTSTART:20171214T163000
DTEND:20171214T173000
DTSTAMP:20260916T054244Z
UID:95235016bb621268e80f77afc3b40442fe226e675bc1e7daf93af6c2
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Robert Guy Griffin\nMIT Massachusetts Institute of Techn
 ology\nUSA\nThis presentation will selectively cover three closely related
  sets of experiments that employ magic angle spinning (MAS) NMR\, dynamic 
 nuclear polarization (DNP)\, and their application to structural determina
 tion of Ab1-42 amyloid fibrils.\nApproximately 110 years ago\, Auguste Det
 er\, the first patient diagnosed with Alzheimer’s disease (AD)\, passed 
 away and fibrils composed of the Ab1-42 protein\, the toxic species in AD\
 ,  were found postmortem in her brain.  Since that time there have been 
 numerous attempts to understand the structure of these fibrils with the go
 al of hastening a cure.  However\, since these species do not diffract to
  high resolution and are insoluble\, a true atomic resolution structure ha
 s been lacking. Accordingly\, we have developed a suite of MAS dipolar rec
 oupling experiments that permit the measurement of multiple 13C-13C and 13
 C-15N distances and the determination of atomic resolution structures of f
 ibrils. We demonstrate the methodology with a description of the high reso
 lution structure of fibrils of monomorphic Ab1-42\, constrained by measure
 ment of over 500 inter- and intramolecular distances.\nSecond\, in order t
 o increase the signal-to-noise in MAS spectra and to better determine mole
 cular structures\, we developed methods to perform high field dynamic nucl
 ear polarization (DNP) experiments. The experiments utilize sub-terahertz 
 microwaves (~150-600 GHz) generated by gyrotron microwave sources together
  with paramagnetic polarizing agents to enhance the sensitivity of MAS NMR
  experiments. Specifically\, we irradiate electron-nuclear transitions tha
 t transfer the large electron polarization to nuclear spins via the Overha
 user\, cross and solid effects. In addition\, we have recently initiated t
 ime domain DNP in order to circumvent the field dependence of CW DNP. We s
 how that spin locking the electrons and matching the NOVEL condition serve
 s as an effective approach to time domain DNP. Furthermore\, the spin lock
 ing microwave field can be amplitude and frequency modulated to increase t
 he efficiency of the polarization transfer.  Applications to Ab1-42 will 
 be presented.\n 
LOCATION:BCH 2201 https://plan.epfl.ch/?room==BCH%202201
STATUS:CONFIRMED
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