Department of Physics of Norwegian University of

Science and Technology

Department of Chemical Engineering,

University of California, Santa Barbara

Title

Co-assembly of functionally-active membrane proteins in mesostructured silica

Abstract
The physicochemical properties of membrane proteins, such as for selective catalysis, biosensing, or ion transport, are highly desirable for technological applications, although they are exceedingly challenging to harness in synthetic abiotic host materials. This is due, in part, to the challenges of incorporating relatively fragile protein molecules at sufficient concentrations in robust host environments in which the functionalities of the membrane proteins are retained. Nevertheless, judicious selections of self-assembling surfactants, solvent, silica precursors, and synthesis conditions enable high concentrations of functionally active membrane proteins to be stabilized in solution and in robust mesostructured inorganic-surfactant host matrices. Specifically, light-activated proteorhodopsin (PR), a transmembrane protein that pumps H+ ions in green light, has been incorporated at high loadings (>30 wt%) into transparent silica-surfactant films with high extents of mesostructural order. Small-angle X-ray scattering, solid-state NMR, and cryo-EM analyses yield detailed insights on the extent of mesoscale order and the nanoscale interactions of the protein, surfactant, and silica species in the materials.
The results point to the complicated and closely coupled relationships among the compositions, structures, and dynamics of proteorhodopsin in the mesostructured composite films. This is especially the case for the complicated influences that the stabilizing and structure-directing surfactants have on the function of PR and the formation of robust ordered host matrices. For example, the inclusion of certain phospholipids interestingly leads to improved mesostructural order, as well as enabling the pKa value of a key ion-channel residue to be tuned to extend the pH range over which proteorhodopsin molecules function. Transient UV−visible spectroscopy analyses furthermore show that the proteorhodopsin molecules in mesostructured silica-surfactant films exhibit native-like dynamics, as well as enhanced stability compared to surfactant or lipid environments. The results correlate the nano-scale compositions, structures and conformational dynamics of the proteorhodopsin molecules and surfactant-silica host materials with their macroscopic properties, leading to the establishment of key biomimetic design criteria. The light absorbance properties and light-activated conformational changes of the proteorhodopsin guest molecules in mesostructured silica films are consistent with those associated with the native H⁺_- pumping mechanism of these biomolecules, which have potential applications for solar-to-electrochemical energy conversion.

References

M.W. Berkow, et al., Co-assembly of functionally-active proteorhodopsin membrane protein molecules in mesostructured silica-surfactant films, Chem. Mater., 35, 8502–8516 (2023).
C.-T. Han, et al., Lipid membrane mimetics and oligomerization tune functional properties of proteorhodopsin, Biophys. J., 122, 1–12 (2023).
J.P. Jahnke, et al., Functionally active proteorhodopsin membrane proteins incorporated in mesostructured silica films, J. Am. Chem.Soc., 140, 3892–3906 (2018).
J.P. Jahnke, et al., Mesostructured Materials with Controllable Long-Range Orientational Ordering and Anisotropic Properties, Adv. Mater., 2306800 (2023).

Department of Chemistry, University of Oxford

Instituto de Investigaciones en Materiales, IIM (Materials Research Institute)

Physics and IFIMAC, Universidad Nacional Autónoma de México

Title

The versatility of Physical Vapor Deposition Techniques to obtain novel materials or out-of-equilibrium crystallographic phases

Abstract
Currently, thin film deposition techniques such as physical vapor deposition are widely used at an industrial level because they allow the modification of surfaces to provide new functionalities to solid materials. However, at the research level, they offer a wide range of possibilities for generating materials under non-equilibrium thermodynamic conditions, enabling the synthesis of alloys with compositions beyond solubility limits, metastable crystalline phases, highly doped semiconductors, high-entropy or multi-elemental alloys (including nitrides or oxides), etc. Quasi-diamond-like carbon or DLC (Diamond-Like Carbon) has been one of the great revelations in materials developed in thin films, with a wide range of current applications.
This discussion briefly overviews examples of non-thermodynamic stable materials developed by the PVD techniques, including cathodic arc, pulse laser ablation, or magnetron sputtering. Topics include the high-sp 3 bonded DLC films 1 and bismuth oxide films in the cubic phase 2,3,4 that is thermodynamically stable only at temperatures above 700 °C but can be synthesized as a thin film with properties of great technological interest. Another topic includes forming high-entropy metal nitrides 5 for mechanical-tribological applications.

References

1. A. C. Ferrari, A. Libassi, B. K. Tañer, V. Stolojan, L. M. Brown, S. E. Rodil, B. Kleinsorge and J. Robertson. Physics Review B 62, 11089-11103 (2000).
2. Celia L Gomez, Osmary Depablos-Rivera, Juan C Medina, Phaedra Silva-Bermudez, Stephen Muhl, Andreas Zeinert, Sandra E Rodil, Solid State Ionics 255, 147-152 (2014).
3. O. Depablos-Rivera, A. Martínez, S. E. Rodil, Journal of Alloys and Compounds 853, 157245 (2021).
4. SE Rodil, O Depablos-Rivera, JC Sánchez-López, Lubricants 11(5), 207 (2023)
5. Uriel Jirón-Lazos, Sandra E Rodil, Dalia Alejandra Mazón-Montijo, José Raúl Pérez-Higareda, David Torres-Torres, Andrés Manuel Garay-Tapia, Zeuz Montiel-González, Journal of Materials Science 58 (28), 11771-11787 (2023).

 Dipartimento di Fisica, Sapienza Università di Roma 

Special online talk

(the organizing committee recognizes Monica

Ledesma's efforts to make this possible) 

Title

Emergent collective behaviour and complexity

Abstract
I will discuss the general problem of studying the emergent collective behavior of an assembly of a large number of agents in the framework of statistical mechanics showing a few examples. I will discuss how complexity emerges in that framework.

I will present my viewpoints on complexity stressing the importance of multiple equilibria; I will then recall the genesis of the concept of multiple equilibria in natural sciences.
Finally, I will describe my contribution to the development of this concept in the framework of statistical mechanics and I will briefly mention the cornucopia of applications of these ideas both in physics and in other disciplines

Department of Physics and Astronomy of

University of Pennsylvania

Department of Physics, University of Oxford

Title

Biological shapes emerging from physics at the nanoscale

Abstract

Biological shape is central to many scientific and technological problems. Currently, the properties of complex, adaptive biological shapes and structures are studied diverse fields of biology, medicine, engineering, materials, computer science and biological physics. The shapes of biological tissues emerge from a complex interplay of physics, chemistry and genetics (evolution) that creates structures able to adapt to their environments and allow organisms to survive and process information across temporal and special scales. Shape and mechanical stability of living organisms rely on precise control in time and space of growth, which is achieved by dynamically tuning the mechanical properties of their hierarchically built structures from the nanometer up.

In my lab we use one of the main tools of nanotechnology, the atomic force microscope (AFM) to extract the physics underlying the emergence of biological shapes from the nanoscale. It is now well-established that cellular behaviour (including e.g. stem cell differentiation) crucially depends on the mechanical properties of the cells’ environment. Much attention has been directed towards the importance of the stiffness of the natural or artificial matrices where cells grow, with the purpose of either understanding mechanotransduction, or controlling the behaviour of cells in medical applications such as tissue engineering. While stiffness has been the focus of most experimental research, neither cells nor matrices are elastic. Biological systems dissipate energy (i.e. they are viscous), present different time responses at different spatial scales that characterise their responses to external stimuli. Measuring viscoelasticity at the nanoscale has remained experimentally challenging [1,2]. In my talk I will present AFM-based techniques to measure and map the viscoelasticity of living tissues, cells, membranes, collagen, extracellular matrices, and tissue engineering matrices across the spatial and temporal scales, and chirp-based spectroscopic techniques to assess viscoelasticity from Hz to 100s kHz at the nano and micro scale developed in my lab [3]. Our results have uncovered that extracellular matrices of both living plants and tumours present an almost perfect linear viscoelastic behaviour that is key to understand their growth and shape. I will present our work showing how the growth and shape of the roots, leaves and hypocotyl of living Arabidopsis thaliana living plants are related to the nanoscale viscoelasticity of plant cell walls [4] at the time scales probed by multifrequency AFM and how this can be understood using concepts and theories from non-equilibrium thermodynamics. I will also show how this knowledge can be used to create “smart” bioinspired materials, which progressively will harness biological properties, such as adaptation, and eventually learning [5].

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References

[1] “Multifrequency AFM reveals lipid membrane mechanical properties and the effect of cholesterol in modulating viscoelasticity” 2019. Z Al-Rekabi, S Contera; Proceedings of the National Academy of Sciences 115 (11), 2658-2663.

[2] “Mapping nanomechanical properties of live cells using multi-harmonic atomic force microscopy”2011 A Raman, S Trigueros, A Cartagena, APZ Stevenson, M Susilo, E Nauman, S Contera. Nature Nanotechnology 6 (12), 809.

[3] “Nanoscale rheology: Dynamic Mechanical Analysis over a broad and continuous frequency range using Photothermal Actuation Atomic Force Microscopy”. Alba Rosa Piacenti, Casey Adam, Nicholas Hawkins, Ryan Wagner, Jacob Seifert, Yukinori Taniguchi, Roger Proksch, Sonia Contera . ACS Macrocomolecules, in press, https://doi.org/10.1021/acs.macromol.3c02052

[4] “Mapping cellular nanoscale viscoelasticity and relaxation times relevant to growth of living Arabidopsis thaliana plants using multifrequency AFM” J Seifert, C Kirchhelle, I Moore, S Contera. Acta Biomaterialia, 2021;121:371-382.

[5] “Nano comes to life: How nanotechnology is transforming medicine and the future of biology” Sonia Contera, Princeton University Press 2019.

 Research Center for Computer Science and

Information Technologies,

Macedonian Academy of Sciences and Arts.