You are welcome to attend the following satellite tutorials. Lunch and refreshments on Saturday and Sunday will be served (included in the separate registration fee).

 

• Visualizing soft materials using cryogenic electron microscopy
  Dr. Jefferson Bettini & Dr. Laura Silva (LNNano/CNPEM)
  
  Saturday (July 12, 2025) 8:30 am
  
  Cryogenic transmission electron microscopy (Cryo-TEM) is a technique used for the characterization of soft and beam-sensitive materials at the nanoscale, particularly in their native hydrated state. It uses the interaction between electrons and matter to form high-resolution images and presents specific challenges when applied to delicate systems, including radiation damage and low image contrast. This course will cover the fundamental principles of electron microscopy, focusing on electron–matter interactions and image formation mechanisms. Strategies to maximize contrast and minimize damage, such as low-dose imaging protocols and advanced contrast techniques, will be emphasized. Additionally, the course will address cryogenic sample preparation methods tailored to soft materials, with a focus on the vitrification of specimens across solid to semi-solid states, ensuring structural preservation and image quality.

 

• Magnetic resonance for the study of polyelectrolytes - charge, conformation, packing, and molecular dynamics
  Dr. Ulrich Scheler, Leibnitz Institute for Polymers, Dresden, Germany
  
  Saturday (July 12, 2025) 2:00 pm 
  
  The local nature of nuclear magnetic resonance (NMR) offers unique insight into molecular properties ranging from chemical structure, molecular arrangement, conformation, charge to molecular dynamics over many time scales. After introducing a few basic principles of modern NMR experiments the tutorial will focus on the information available from a variety of experiments. Most of the applications involve ¹H and ¹³C but examples of other nuclei will be demonstrated as well. The chemical shift in NMR spectra enables the identification of the structures involved as well as states of dissociation. Further information is obtained from distance-dependent properties like dipolar coupling. In solids this is used to probe proximity and thus packing in multilayers and complexes. Pulsed-field-gradient (PFG) NMR is used to probe translational motion like diffusion. From the diffusion coefficient the hydrodynamic radius as a measure of the size of molecules and thus the conformation is derived. This is used to investigate the impact of the charge on the conformation of polyelectrolytes. If an electric field is applied in situ charged molecules move as is measured by PFG NMR. From the combination of diffusion and electrophoretic NMR the effective charge of molecules and complexes is determined allowing to quantify counterion condensation and binding of ligands or formation of complexes. Dynamic NMR ranging from exchange spectra to different kinds of NMR relaxation probes molecular dynamics over a wide range of correlation times. The transverse relaxation time T 2 is sensitive to slow motion of polymer chains. Electron paramagnetic resonance (EPR) has significantly higher sensitivity than NMR but requires the presence of unpaired electrons that are introduced by stable spin labels. That in turn enables highly selective investigation of the local chain mobility and has been applied to polyelectrolyte complexes and multilayers.

 

• Single-molecule spectroscopy
  Prof. Ben Schuler, University of Zurich, Switzerland
  
  Sunday (July 13, 2025) 8:30 am
  
  Single-molecule fluorescence spectroscopy has evolved into a versatile method for probing distances, distance distributions, dynamics, and interactions of biopolymers such as proteins and nucleic acids. The chemical tools available for biopolymers facilitate their site-specific labeling with fluorophores, allowing the use of Förster resonance energy transfer (FRET) as a spectroscopic ruler in the nanometer range. I will present the basic concepts of single-molecule spectroscopy and FRET, and then show how these methods can be used to obtain information about biopolymers, especially polyelectrolytes, such as highly charged intrinsically disordered proteins and nucleic acids. In particular, I will show how the combination of such measurements with concepts from polymer physics allows us to quantify a number of interesting properties and processes, including (i) intrachain distance distributions and translational diffusion coefficients, which can be related to radii of gyration and hydrodynamic radii, respectively; (ii) intrachain distance dynamics, which can be related to chain relaxation times of the polymer and the phenomenon of internal friction; (iii) the formation of intermolecular complexes between polyelectrolytes, including the quantification of binding equilibria, kinetics, and the role of counterion release; (iv) the formation of complex coacervates and the conformational properties of biological polyelectrolytes within biomolecular condensates.