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CATEGORIES:MRC Mitochondrial Biology Unit Seminars
SUMMARY:Viscosity and macromolecular crowding affects size
 -dependent protein diffusion and conformation in t
 he mitochondrial matrix - Dr Werner Koopman | Radb
 ound Centre for Mitochondrial Medicine 
DTSTART;TZID=Europe/London:20191127T150000
DTEND;TZID=Europe/London:20191127T160000
UID:TALK120409AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/120409
DESCRIPTION:The mitochondrial matrix constitutes a biochemical
  reaction environment with a highly complex struct
 ure. During normal and pathological conditions\, t
 his mitochondrial compartment displays dynamic cha
 nges in its (ultra)structure and physicochemical p
 roperties\, which affect diffusion-limited reactio
 ns and molecular target finding. However\, there i
 s little quantitative information on how the visco
 sity of the mitochondrial matrix solvent (ηsolvent
 ) impacts on solute diffusion in living cells. Thi
 s precludes a proper understanding of how mitochon
 drial structural and functional dynamics affect mi
 tochondrial\, and thereby cellular\, functioning. 
 It was previously demonstrated that matrix-protrud
 ing folds (cristae) in the mitochondrial inner mem
 brane substantially hinder the free diffusion of f
 luorescent proteins (FPs). Using HeLa cell lines e
 xpressing matrix-targeted FP-concatemers of increa
 sing MW (AcGFP1\, AcGFP12\, AcGFP13\, AcGFP14) we 
 here provide evidence that: (i) ηsolvent equals 2.
 69-3.32 cP\, (ii) all FPs assume a molecular confo
 rmation of maximal size (“extended”)\, (iii) the m
 itochondrial matrix fluid modulates FP diffusion i
 n a MW-dependent manner via viscosity-dependent an
 d -independent mechanisms. Treatment with chloramp
 henicol (CAP)\, a mitochondrial protein synthesis 
 inhibitor that induces the mitochondrial unfolded 
 protein response (UPRmito)\, 2-fold reduced the nu
 mber of cristae and 24-fold increased ηsolvent (64
 .7-80.0 cP). Under these conditions AcGFP14 assume
 d its minimal size (“compact”)\, compatible with m
 acromolecular crowding. These findings support a m
 echanism in which (combined) changes in mitochondr
 ial nanostructure and matrix viscosity modulate mi
 tochondrial bioreactions by altering the diffusion
  and molecular conformation of matrix solutes in a
  MW-dependent manner.
LOCATION:Sackler Lecture Theatre (Level 7) The Keith Peters
  Building\, Cambridge Biomedical Campus
CONTACT:Hannah Burns
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