Principles of light-induced charge transfer for optogenetics 

14-16 June 2021, online 

The “Principles of light-induced charge transfer for optogenetics” workshop was held online from June 14 to June 16, 2021. 

The workshop was attended by 81 participants The total number of participants is 81 coming from 16 countries, as specified: Italy: 42; United States of America: 8; Germany: 7; India: 6; United Kingdom: 3; Poland: 3; Netherlands: 2; Austria: 2; Hungary: 1; Czech Republic: 1; Cameroon: 1; China: 1; Belgium: 1; France: 1; Israel: 1; Egypt: 1.

14 participants were invited speakers, 17 were contributing speakers, 3 were members of the CT4OPTO scientific committee, and 3 of the organizing committee. The event was organized by the Institute Nanoscience of the National Research Council of Italy, the University of L’Aquila and the University of Southern California. The event was sponsored by Psi-k, received the patronage of Cecam-IT-Simul, and was supported by Gruppo Alchimie for technical assistance. 

The workshop focused on the discussion of state-of-the-art theoretical approaches to treat photoinduced charge transfer processes in light-sensitive proteins that are currently exploited in optogenetic tools. Attention was also devoted to the experimental probing of such events. 

Leading scientists from the fields of excited state properties of biological matter and charge transfer processes in proteins, and in particular in rhodopsins and flavin-containing domains, shared and discussed their theoretical and experimental approaches. 

Current optogenetic challenges were faced from a chemicophysical perspective, highlighting the main achievements and open questions in this timely and stimulating research field. 

Main CT4OPTO Topics were the following. 

  • Optical properties: A crucial point for the development of optogenetic tools is the tuning of their light sensitivity range. The investigation of the optical properties of photoactive proteins is therefore of paramount importance, as well as the comprehension of the variability, and possible tuning, of light absorption depending on the environmental conditions.
  • Excited state dynamics: Photoinduced charge transfer processes occur out of equilibrium, and the significant changes induced by the photoexcitation in both the electronic and nuclear structure of the reactants have to be considered to model the system dynamics. Strategies and challenges in the theoretical investigation of the excited state dynamics of complex systems were therefore discussed.
  • Proton and electron transfer reactions: Theoretical approaches to treat ET, PT and proton coupled electron transfer (PCET), based both on purely quantum and on QM/MM methods, were discussed. Experimental techniques to investigate the thermodynamics and kinetics of charge transfer events in photoreceptors were presented. The investigation of the protein role and response to charge transfer was also addressed.
  • Photoreceptors of current optogenetic interest: The first and most widely used optogenetic tools are light-controlled rhodopsins. More recently, blue-light photoreceptors with flavin chromophores, like LOV (Light Oxygen-Voltage) and BLUF (Blue Light Using Flavin) domains, have been also recruited for optogenetic applications.

Detailed Program and links to videos 

Monday, June 14, 2021 | video playlist
Session 1/1 – Investigating optical properties

  • Massimo Olivucci University of Siena & Bowling Green State University, “On the fluorescence enhancement of arch neuronal optogenetic reporters” | 
  • Dongping Zhong The Ohio State University, “Light-induced charge transfer triggers dimer dissociation of UVR8 photoreceptor for possible optogenetics”| video
  • Contributed speakers: 
    • Nadja K. Singer, University of Vienna, “From taco to banana: turn-on mechanism of a  fluorescent probe for imaging GABAA receptors” | video
    • Laura Pedraza-González, University of Siena, “Automated QM/MM model screening of rhodopsin variants  displaying enhanced fluorescence” | video
    • Volha Chukhutsina, Imperial College London, “The keto group in β2 of the carotenoid tunes the orange  carotenoid protein photocycle kinetics” |
    • Ciro A. Guido, University of Padova, “Exploring the spatial features of electronic transitions in biomolecular systems by swift electrons” | video

Session 1/2, Investigating optical properties

  • Igor Schapiro, The Hebrew University of Jerusalem, “Insight into the spectral tuning mechanism of retinal proteins”
  • Roberta Croce, Vrije Universiteit Amsterdam, “Breaking the red-limit: driving oxygenic photosynthesis with far-red light”

Tuesday, June 15, 2021 | video playlist
Session 2/1, Interplay between CT events and environmental factors

  • Petra Imhof, Freie Universität Berlin, “Interplay of hydration, water mobility, and proton transfer in cytochrome c oxidase” | video
  • Andrea Amadei, University of Rome “Tor Vergata”, “On the modeling of charge transfer processes in complex chemical systems” | video
  • Contributed talks: 
    • Puja Goyal State, University of New York, “Modulation of adenosylcobalamin photochemistry by the CarH photoreceptor protein” | video
    • Bryan Kudisch, Princeton University, “Active-site environmental factors customize the  photophysics of photoenzymatic old yellow enzymes” | video
    • Matteo Capone, University of L’Aquila, “Multiscale modelling of the photoactivation of electron donor acceptor complexes in ene reductases” | video
    • Ruibin Liang, Texas Tech University, “Light-activation mechanism of Channelrhodopsin 2” | video
    • Fulvio Perrella, University of Naples Federico II, “Proton transfer in fluorescent proteins: a dynamical viewpoint on hydrogen bonds networks” | video

Session 2/2, Excited states dynamics

  • Gregory Scholes, Princeton University, “Electron transfer reactions: vibration and dielectric tuning” | video
  • Benedetta Mennucci, University of Pisa, “From the light absorption by the embedded chromophore to the conformational change of the protein: can we simulate such a long travel in space and time?” | video

Wednesday, June 16, 2021 | video playlist
Session 3/1, Excited states dynamics

  • Nadia Rega, University Federico II of Napoli & Center for Advanced Biomaterials for Healthcare, “Probing relaxation mechanisms of photoinduced charge transfer phenomena: combining time-resolved vibrational analysis and ab-initio molecular dynamics” | video
  • Basile Curchod, Durham University, “In silico photochemical experiments with non-Born-Oppenheimer molecular dynamics” | video
  • Contributed talks: 
    • Uriel N. Morzan, International Centre for Theoretical Physics, “Optical signature of strong hydrogen bonds” | video
    • James Green, CNR-IBB, “A fragment based approach to the quantum dynamics of  multichromophoric systems: application to the GC DNA base pair” | video
    • Francesco Di Maiolo, Goethe Universität, “Quantum molecular dynamics in out of equilibrium  environments: redfield-smoluchowski and hydrodynamic approaches” | video
    • Pavel S. Rukin, CNR-S3 Institute of Nanoscience, “Theoretical study of internal conversion between B and Q bands in a functionalized porphyrin” | video

Session 3/2, Retinal and flavin based systems

  • Marco Garavelli, University of Bologna, “Modelling accurate photoinduced events and transient spectroscopies in biomolecules: the paradigmatic case of retinal systems” | 
  • Sharon Hammes-Schiffer, Yale University, “Nonequilibrium excited state dynamics of proton-coupled electron transfer in BLUF photoreceptor proteins” | video
  • Contributed talks:
    • Valeria Giliberti, Istituto Italiano di Tecnologia, “Conformational changes of light-sensitive membrane proteins determined by infrared difference nanospectroscopy” | video
    • Luca Bellucci, CNR-NEST Institute of Nanoscience, “Relating retinal isomerization and deprotonation mechanism in Channelrhodopsin-2” | video
    • Himanshu Bansal, Dayalbagh Educational Institute, “Improved optogenetic retinal prostheses with Chrmine” | video
    • Xiankun Li, Princeton University, “Ultrafast dynamics of light-induced charge transfer in Lactate Monooxygenase” | video

Session 3/3, Retinal and flavin based systems

  • Ana-Nicoleta Bondar, Freie Universität Berlin, “Proton transfers with dynamic hydrogen-bond networks” | video
  • Andreas Möglich, University of Bayreuth, “Interplay of signals in Light-Oxygen-Voltage receptors” | 

Best Oral Contribution Awards 

The two best flash presentations of the workshop were recognized with the “Best Oral Contribution Award“. 

The award recipients were selected under the following criteria: Excellence of the candidate and presentation; Relevance to the theme of the workshop; Juniority; Experimental/theoretical balance; Gender balance; Geographical balance. They were announced during the closing session. 

The winners are Laura Pedraza-González from the Department of Biotechnology, Chemistry and Pharmacy, University of Siena, and Bryan Kudisch, from the Department of Chemistry, Princeton University, with the following contributions.


The Scientific Committee of the CT4OPTO was composed by: 

  • Isabella Daidone | University of L’Aquila 
  • Rosa Di Felice | University of Southern California and CNR Nano Modena 
  • Laura Zanetti Polzi | CNR Nano Modena 

The organizers of the CT4OPTO workshop were: 

  • Laura Zanetti Polzi | CNR Nano Modena 
  • Mara Di Berardo | CNR Nano Modena 
  • Maria Bartolacelli | CNR Nano Modena 
  • Emanuela Bertini| Alchimie Digitali 

General remarks 

During the whole workshop all participants showed a very high level of interest and keen participation. Despite the online format, which does not facilitate the speakers-audience interaction, the discussion was always fruitful and lively, showing the high competence of the participants in the workshop topics. The invited speakers delivered very interesting and inspiring talks, but we were also impressed by the high quality of the contributed talks. Overall, the whole workshop was characterized by a fruitful exchange of ideas that will surely motivate new research on the topic. 

Conclusions and prospects 

The workshop was undoubtedly successful: the number of applicants exceeded our expectations, the invited speakers presented very well their excellent research work, the contributed speakers delivered well-prepared and interesting talks. We are sure that all the speakers gave very interesting inputs to the participants, but we also think that very interesting inputs from the audience came out as well. We noticed that research on these topics has reached impressive levels, both from an experimental and from a theoretical point of view. We also believe that some possible routes for further developments in the field emerged during the workshop.

Further details 

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