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SUMMARY:Tuning Protein Aggregation Pathways by Charges - Prof. Dr. Frank S
 chreiber\, Institute of Applied Physics\, University of Tuebingen\, German
 y
DTSTART:20140530T130000Z
DTEND:20140530T140000Z
UID:TALK52063@talks.cam.ac.uk
CONTACT:Dr Eileen Nugent
DESCRIPTION:The handling and manipulation of proteins is not only a biolog
 ical or chemical task\,\nbut also poses interesting challenges from a phys
 ics perspective.\nRemarkably\, protein crystallization\, despite being the
  dominating tool in structural biology\,\nis still more art than science.\
 nOther forms of protein aggregation are equally important\, but follow a d
 ifferent pathway\,\nwhich may lead to\, e.g.\, gelation.\nIn order to shed
  light on the underlying mechanisms of aggregation\, \nthe use of charges 
 and the tailoring of the electrostatic interactions of proteins turn out t
 o be extremely versatile.\nMultivalent counterions have been found to indu
 ce a rich phase behavior of protein solutions\, \nincluding a reentrant co
 ndensation and a metastable closed-loop liquid-liquid phase separation (LL
 PS) [1]. \nThe LLPS can be used to optimize conditions for protein crystal
 lization and play a role in its prediction [2\,3]. \nDifferent crystalliza
 tion processes can be identified throughout the phase diagram\, \nleading 
 to differing crystal morphologies [1\,4]. \nInterestingly\, high-resolutio
 n crystal structures show that trivalent ions act as ion-bridges \nbetween
  two proteins in the crystal [4]. \nCrystallization close to the first tra
 nsition seems to follow the classical one-step nucleation process directly
  \nfrom a homogeneous solution. Under other conditions around the LLPS\, \
 ncrystallization rather follows a two-step nucleation process with an inte
 rmediate precursor state. \nProtein clusters seem to play an important rol
 e for the nucleation [5]\, \nalthough possibly different from what is naiv
 ely expected.\nEvidence for the formation of protein clusters upon additio
 n of multivalent ions is provided \nby both small angle scattering and dyn
 amic light scattering [5\,6\,7]. \nFinally\, we will discuss opportunities
  of following the different types of aggregation phenomena\nand their asso
 ciated kinetics in situ by real time scattering experiments.\n[1] F. Zhang
  et al.\, Soft Matter 8 (2012) 1313-1316 \n    F. Zhang et al.\, Phys. Rev
 . Lett 101 (2008) 148101\n[2] P.R. ten Wolde\, D. Frenkel\, Science 277 (1
 997) 1975-1978 \n[3] P.G. Vekilov\, Cryst. Growth Des. 4 (2004) 671-685 \n
 [4] F. Zhang et al.\, J. Appl. Cryst. 44 (2011) 755-762 \n[5] F. Zhang et 
 al.\, Faraday Disc. 159 (2012) 313-325 \n[6] D. Soraruf et al.\, Soft Matt
 er 10 (2014) 894 \n[7] A. Sauter et al.\, in preparation \n
LOCATION:Small Lecture Theatre\, Cavendish Laboratory
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