Proton transfer (PT) is at the heart of fundamental natural biochemical reactions, e.g. in bioenergetics, where proteins are the main proton mediators. PT between two specific points requires a change in the proton motive force via alteration of acid-base properties. Nature solved this problem primarily by modulating the protein structure during the PT process. Here, we introduce a light-triggered proton donor-bridge-acceptor approach for inducing and visualizing directional PT in biosystems, specifically peptides. To do so, we synthesize unnatural amino acids containing a light-triggered proton donor and acceptor and place them at the ends of peptide bridges that differ in their amino acid composition while creating a giant ΔpKa* gradient between them upon photoexcitation. Ultrafast optical spectroscopies allow for visualization of the PT process across the donor-bridge-acceptor system and extraction of the PT kinetics. Our results reveal the importance of side chains, peptide structure, and environment in promoting PT. We show that helical structures can promote PT even with hydrophobic side chains, whereas titratable oxo-amino-acids can promote PT via their side chains even in an aprotic environment. Our strategy for inducing and visualizing the PT process across any desired pathway can be extended to various peptide systems and into proteins, thus opening a new field of research.

Biological membranes play a major role in diffusing protons on their surfaces between transmembrane protein complexes. The retention of protons on the membrane's surface is commonly described by a membrane-associated proton barrier that determines the efficiency of protons escaping from surface to bulk, which correlates with the proton diffusion (PD) dimensionality at the membrane's surface. Here, we explore the role of the membrane's biophysical properties and its ability to accept a proton from a light-triggered proton donor situated on the membrane's surface and to support PD around the probe. By changing lipid composition and temperature, while going through the melting point of the membrane, we directly investigate the role of the membrane phase in PD. We show that the proton transfer process from the proton donor to the membrane is more efficient in the liquid phase of the membrane than in the gel phase, with very low calculated activation energies that are also dependent on the lipid composition of the membrane. We further show that the liquid phase of the membrane allows higher dimensionalities (close to 3) of PD around the probe, indicating lower membrane proton barriers. In the gel phase, we show that the dimensionality of PD is lower, in some cases reaching values closer to 1, thus implying specific pathways for PD, which results in a higher proton recombination rate with the membrane-tethered probe. Computational simulations indicate that the change in PD between the two phases can be correlated to the membrane's ‘stiffness’ and ‘looseness’ at each phase.

Brønsted photoacids and photobases are a unique class of molecules that undergo a major change in their pK_a values between their ground and excited states, resulting in donating or accepting a proton, respectively, but only after light excitation. This property of photoacids/photobases makes them an attractive tool for light-gating various dynamic processes. Here, we review the use of this property to manipulate functional dynamic systems with light. We discuss how a proton transfer event that can happen upon light excitation from a photoacid to a chemical moiety of a certain system or, vice versa, from the system to a photobase, can result in a shift in the equilibrium of the system, resulting in some dynamicity. We detail various systems, including self-assembly processes of nanostructures, self-propulsion of droplets, catalysis for hydrogen evolution or CO₂ capturing, nanotechnological devices based on enzymatic processes, and changes in proton-conducting ionophores and materials. We detail the basic guidelines for using Brønsted photoacids and photobases in a desired system and conclude with the current technological gaps in further using these molecules.

Plastics are an indispensable part of modern life. Due to the harmful environmental consequences of petroleum-based plastic usage, there is an urgent need to replace them with biodegradable bioplastics that meet the sustainability standards required for a low environmental footprint. Here, we use plant-derived proteins to produce bioplastics. Since most plant-derived proteins are not water-soluble, there has always been a need to use acidic or basic solutions or organic solvents with plasticizers and crosslinkers to produce bioplastic. Here, we present a counterintuitive approach for using water-insoluble plant-derived soy and pea proteins to manufacture large-scale bioplastics using only water as a solvent without common plasticizers or crosslinkers. We show that bioplastics can form via a self-assembly process initiated by a small molecular initiator while maintaining favourable mechanical properties. The lack of crosslinking and the protein nature of the bioplastic leads to a rapid biodegradation process under various conditions. Overall, the approach we present is highly attractive in terms of cost and time, and most importantly, it obeys all the relevant principles of green chemistry in bioplastics production.

In the twenty-first century, proton-exchange membrane fuel cells (PEMFCs) and water electrolyzers (PEMWEs) represent promising technologies for clean and efficient power generation. Proton exchange membranes (PEMs) are the key components in PEMFCs and PEMWEs. Currently, all proton exchange membranes (PEMs) employed in PEMFCs or PEMWEs are based on synthetic primarily sulfonated polymers. While these synthetic polymers have good proton conductivity, they are expensive and raise environmental concerns. As a result, there is growing interest in identifying suitable alternatives that are cost-effective, sustainable, and environmentally friendly. Biopolymers, which are naturally occurring alternatives to synthetic polymers, are linked by covalent bonds and include cellular components such as proteins, nucleotides, lipids, and polysaccharides. Proteins derived from sustainable sources offer potential advantages for polymer production due to their ability to self-heal and their higher water transport capabilities, particularly in fast-growing plants like cannabis, soybean, corn. In this study, we aim to: (i) develop proton exchange membranes based on plant-based proteins, (ii) fabricate membrane electrode assemblies (MEAs) with the protein membranes and assess their performance as PEM fuel cells and water electrolyzers, and (iii) optimize the polymerization procedures to comply with green chemistry principles and ensure high proton conductivity at temperatures ranging from 80°C to 150°C, making them suitable for use in PEMFCs and PEMWEs.

Electron transfer (ET) and proton transfer (PT) events are involved in most of the biochemical processes in biology, such as within the aerobic respiration system and photosynthesis. Whereas most of the ET and PT reactions in biology are short-range on the (sub-)nanometer scale, several biological systems are capable of long-range ET or PT on the hundreds of nanometers to micrometers. This perspective summarizes which biological or bioinspired systems are capable of long-range ET or PT, which suggested mechanisms might explain long-range ET or PT together with the needed molecular basis within the biological material to allow this transport for very long distances. The fundamental difference between long-range ET and PT is discussed as well as design guidelines for new electron- or proton-conductive biological materials.

Proton circuits within biological membranes, the foundation of natural bioenergetic systems, are significantly influenced by the lipid compositions of different biological membranes. In this study, we investigate the influence of mixed lipid membrane composition on the proton transfer (PT) properties on the surface of the membrane. We track the excited-state PT (ESPT) process from a tethered probe to the membrane with time-scales and length-scales of PT relevant to bioenergetic systems. Two processes can happen during ESPT: the initial PT from the probe to the membrane at short timescales, followed by diffusion of dissociated protons around the probe on the membrane, and the possible geminate recombination with the probe at longer timescales. Here, we use membranes composed of mixtures of phosphatidylcholine (PC) and phosphatidic acid (PA). We show that the changes in the ESPT properties are not monotonous with the concentration of the lipid mixture; at low concentration of PA in PC, we find that the membrane is a poor proton acceptor. Molecular dynamics simulations indicate that the membrane is more structured at this specific lipid mixture with the least defects. Accordingly, we suggest that the structure of the membrane is an important factor in facilitating PT. We further show that the composition of the membrane affects the geminate proton diffusion around the probe, whereas, on a time-scale of tens of nanoseconds, the dissociated proton is mostly lateral restricted to the membrane plane in PA membranes, while in PC, the diffusion is less restricted by the membrane.

The present invention discloses a slurry for electrode preparation, relevant to the field of electrode fabrication for various applications, which consists of an active material, a conductive additive, and a binder composition that includes a proteinaceous substance that may comprise amino acids, peptides, and/or proteins. The instantly disclosed slurry is useful in electrode fabrication, especially in the context of Li batteries. The process for preparing the electrode includes applying the slurry to a current collector and thermally treating the slurry, ensuring a durable and reliable electrode.

Light harvesting in nature is one of the most important processes, starting with the absorption of light by chromophores within proteins and the transfer of energy from one another via the Förster resonance energy transfer (FRET) mechanism. If the energy is transferred between identical chromophores, the resulting is Homo-FRET. Here, we introduce an artificial system that allows us to control the number of chromophores within a certain protein and to decipher the mechanism of Homo-FRET in proteins in ways not possible in biological systems. We follow Homo-FRET by ultrafast fluorescence anisotropy measurements. We show that for solvated proteins, the mechanism, rate, and efficiency of Homo-FRET are highly dependent on the number of chromophores within the protein. However, in the solid protein matrix, the mechanism remains the same as the number of chromophores increases, but the solid matrix allows long-range Homo-FRET, resulting in full depolarization. The observed higher-than-ideal Homo-FRET contribution to the observed fluorescence anisotropy decay together with the reduction in the limiting anisotropy suggest a mixed coherent-incoherent mechanism of energy transfer.

Lateral proton transport (PT) on the surface of biological membranes is a fundamental biochemical process in the bioenergetics of living cells, but a lack of available experimental techniques has resulted in a limited understanding of its mechanism. Here, we present a molecular protonics experimental approach to investigate lateral PT across membranes by measuring long-range (70 μm) lateral proton conduction via a few layers of lipid bilayers in a solid-state-like environment, i.e., without having bulk water surrounding the membrane. This configuration enables us to focus on lateral proton conduction across the surface of the membrane while decoupling it from bulk water. Hence, by controlling the relative humidity of the environment, we can directly explore the role of water in the lateral PT process. We show that proton conduction is dependent on the number of water molecules and their structure and on membrane composition, where we explore the role of the headgroup, the tail saturation, the membrane phase, and membrane fluidity. The measured PT as a function of temperature shows an inverse temperature dependency, which we explain by the desorption and adsorption of water molecules into the solid membrane platform. We explain our findings by discussing the role of percolating hydrogen bonding within the membrane structure in a Grotthuss-like mechanism.

Light-gated chemical reactions allow spatial and temporal control of chemical processes. Here, we suggest a new system for controlling pH-sensitive processes with light using two photobases of Arrhenius and Brønsted types. Only after light excitation do Arrhenius photobases undergo hydroxide ion dissociation, while Brønsted photobases capture a proton. However, none can be used alone to reversibly control pH due to the limitations arising from excessively fast or overly slow photoreaction timescales. We show here that combining the two types of photobases allows light-triggered and reversible pH control. We show an application of this method in directing the pH-dependent reaction pathways of the organic dye Alizarin Red S simply by switching between different wavelengths of light, i.e., irradiating each photobase separately. The concept of a light-controlled system shown here of a sophisticated interplay between two photobases can be integrated into various smart functional and dynamic systems.

Proton circuits within biological membranes are at the heart of natural bioenergetic systems, whereas different biological membranes are characterized by different lipid compositions. In this study, we investigate how the composition of mixed lipid membranes influences the proton transfer (PT) properties of the membrane by following the excited-state PT (ESPT) process from a tethered probe to the membrane with time-scales and length-scales of PT that are relevant to bioenergetic systems. Two processes can happen during ESPT: the initial PT from the probe to the membrane at short timescales, followed by diffusion of dissociated protons around the probe on the membrane, and the possible geminate recombination with the probe at longer timescales. Here, we use membranes that are composed of mixtures of phosphatidylcholine (PC) and phosphatidic acid (PA). We show that the changes in the ESPT properties are not monotonous with the concentration of the lipid mixture; at low concentration of PA in PC, we find that the membrane is a poor proton acceptor. Molecular dynamics simulations indicate that at this certain lipid mixture, the membrane has the least defects (more structured and unflawed). Accordingly, we suggest that defects can be an important factor in facilitating PT. We further show that the composition of the membrane affects the geminate proton diffusion around the probe, whereas, on a time-scale of tens of nanoseconds, the dissociated proton is mostly lateral restricted to the membrane plane in PA membranes, while in PC, the diffusion is less restricted by the membrane.

Light is an attractive source of energy for regulating stimulus-responsive chemical systems. Here, we use light as a gating source to control the redox state, the localized surface plasmonic resonance (LSPR) peak, and the structure of molybdenum oxide (MoO₃) nanosheets, which are important for various applications. However, the light excitation is not that of the MoO₃ nanosheets but rather that of pyranine (HPTS) photoacids, which in turn undergo an excited-state proton transfer (ESPT) process. We show that the ESPT process from HPTS to the nanosheets and the intercalation of protons within the MoO₃ nanosheets trigger the reduction of the nanosheets and the broadening of the LSPR peak, a process that is reversible, meaning that in the absence of light, the LSPR peak diminishes and the nanosheets return to their oxidized form. We further show that this reversible process is accompanied by a change in the nanosheet size and morphology.

The fluorescence efficiency of excited molecules can be enhanced by many external factors. Here, we showcase a surprising phenomenon whereby light is used as a gating source to increase the fluorescence efficiency of organic cages composed of biphenyl subunits. We show that the enhancement of fluorescence is not due to structural changes or ground-state events. Cryo-fluorescence measurements and kinetic studies suggest a restriction of the phenyl-based structures in the excited state, leading to increased fluorescence, which is also supported by time-resolved measurements. Through computational calculations, we propose that the planarization of the biphenyl units within the cages contributes to emission enhancement. This phenomenon offers insights into the design of optoelectronic structures with improved fluorescence properties.

Lateral proton transport (PT) on the surface of biological membranes is a fundamental biochemical process in the bioenergetics of living cells, but a lack of available experimental techniques has resulted in a limited understanding of its mechanism. Here, we introduce a new molecular protonics experimental approach to investigate lateral PT across membranes by measuring long-range lateral proton conduction via a few layers of lipid bilayers in a solid-state-like environment, i.e., without having bulk water surrounding the membrane. This configuration enables focusing on lateral proton conduction across the surface of the membrane while decoupling it from bulk water. Hence, by controlling the relative humidity of the environment, we can directly explore the role of water in the lateral PT process. We show that proton conduction is dependent on the amount of water and their structure, and on membrane composition, where we explore the role of the head group, the level of tail saturation, and the role of the membrane phase and fluidity. The measured PT as a function of temperature shows an inverse temperature dependency, which we explain by the desorption/adsorption of water molecules into the solid membrane platform. We explain our findings by discussing the role of percolating hydrogen bonding within the membrane structure in a Grotthuss-like mechanism.

Light-gated chemical reactions allow spatial and temporal control of chemical processes. Here, we suggest a new system for controlling pH-sensitive processes with light using two photobases of Arrhenius and Brønsted types. Only after light excitation do Arrhenius photobases undergo hydroxide ion dissociation, while Brønsted photobases capture a proton. However, none can be used alone to reversibly control pH due to the limitations arising from excessively fast or overly slow photoreaction timescales. We show here that combining the two types of photobases allows light-triggered and reversible pH control. We show an application of this method in directing the pH-dependent reaction pathways of the organic dye Alizarin Red S simply by switching between different wavelengths of light, i.e., irradiating each photobase separately. The concept of a light-controlled system shown here of a sophisticated interplay between two photobases can be integrated into various smart functional and dynamic systems.

Light-harvesting is at the heart of photocurrent generation devices, and it is also one of the most important natural phenomena of which photosynthesis is an example. Inspired by natural light-harvesting complexes, we present here a synthetic and artificial solid-state protein-based matrix that is molecularly doped with natural light-harvesting chlorophyll molecules. Such protein matrices are capable of photocurrent generation over a wide range of wavelengths in a source–drain configuration. We show that the photocurrent generation shows a switchable (flipping) behavior when (1) the magnitude of the applied bias is changed, (2) the location of the irradiated area is changed with respect to the electrodes, and (3) a gradient doping, enabled by the facile molecular doping approach, is formed. Finally, the synthetic artificial nature of the protein matrix allows the exploration of several light-harvesting cofactors not used in natural systems, where we further show photocurrent generation by doped, metal-free porphyrins.

Nanometer-scaled objects are known to have dimension-related properties, but sometimes the assembly of such objects can lead to the emergence of other properties. Here, we show the assembly of atomically precise gold nanoclusters into large fibrillar structures that are featuring excitation-dependent luminescence with an excitation-selective circularly polarized luminescence (CPL), even though all components are achiral. The origin of CPL in the assembly of atomic clusters has been attributed to the hierarchical organization of atomic clusters into fibrillar structures, mediated via a hydrogen bonding interaction with a surfactant. We follow the assembly process both experimentally and computationally showing the advance in the structural formation along with its chiroptical electronic properties, i.e., circular dichroism (CD) and CPL. Our study here can assist in the rational design of materials featuring chiroptical properties, thus leading to a controlled CPL activity.

Collagen is one of the most studied proteins due to its fundamental role in creating fibrillar structures and supporting tissues in our bodies. Accordingly, collagen is also one of the most used proteins for making tissue-engineered scaffolds for various types of tissues. To date, the high abundance of hydroxyproline (Hyp) within collagen is commonly ascribed to the structure and stability of collagen. Here, we hypothesize a new role for the presence of Hyp within collagen, which is to support proton transport (PT) across collagen fibrils. For this purpose, we explore here three different collagen-based hydrogels: the first is prepared by the self-assembly of natural collagen fibrils, and the second and third are based on covalently linking between collagen via either a self-coupling method or with an additional cross-linker. Following the formation of the hydrogel, we introduce here a two-step reaction, involving (1) attaching methanesulfonyl to the −OH group of Hyp, followed by (2) removing the methanesulfonyl, thus reverting Hyp to proline (Pro). We explore the PT efficiency at each step of the reaction using electrical measurements and show that adding the methanesulfonyl group vastly enhances PT, while reverting Hyp to Pro significantly reduces PT efficiency (compared with the initial point) with different efficiencies for the various collagen-based hydrogels. The role of Hyp in supporting the PT can assist in our understanding of the physiological roles of collagen. Furthermore, the capacity to modulate conductivity across collagen is very important to the use of collagen in regenerative medicine.