Photoresponsive azo-combretastatin A-4 analogues

Green Approach Toward Triazole Forming Reactions for Developing Anticancer Drugs

Compounds containing triazole have many significant applications in the dye and ink industry, corrosion inhibitors, polymers, and pharmaceutical industries. These compounds possess many antimicrobial, antioxidant, anticancer, antiviral, anti-HIV, antitubercular, and anticancer activities. Several synthetic methods have been reported for reducing time, minimizing synthetic steps, and utilizing less hazardous and toxic solvents and reagents to improve the yield of triazoles and their analogues synthesis. Among the improvement in methods, green approaches towards triazole forming biologically active compounds, especially anticancer compounds, would be very important for pharmaceutical industries as well as global research community. In this article, we have reviewed the last five years of green chemistry approaches on click reaction between alkyl azide and alkynes to install 1,2,3-triazole moiety in natural products and synthetic drug-like molecules, such as in colchicine, flavanone cardanol, bisphosphonates, thiabendazoles, piperazine, prostanoid, flavonoid, quinoxalines, C-azanucleoside, dibenzylamine, and aryl-azotriazole. The cytotoxicity of triazole hybrid analogues was evaluated against a panel of cancer cell lines, including multidrug-resistant cell lines.

Photoresponsive peptide materials: Spatiotemporal control of self-assembly and biological functions

Peptides work as both functional molecules to modulate various biological phenomena and self-assembling artificial materials. The introduction of photoresponsive units to peptides allows the spatiotemporal remote control of their structure and function upon light irradiation. This article overviews the photoresponsive peptide design, interaction with biomolecules, and applications in self-assembling materials over the last 30 years. Peptides modified with photochromic (photoisomerizable) molecules, such as azobenzene and spiropyran, reversibly photo-controlled the binding to biomolecules and nanostructure formation through self-assembly. Photocleavable molecular units irreversibly control the functions of peptides through cleavage of the main chain and deprotection by light. Photocrosslinking between peptides or between peptides and other biomolecules enhances the structural stability of peptide assemblies and complexes. These photoresponsive peptides spatiotemporally controlled the formation and dissociation of peptide assemblies, gene expressions, protein-drug interactions, protein-protein interactions, liposome deformation and motility, cytoskeleton structure and stability, and cell functions by appropriate light irradiation. These molecular systems can be applied to photo-control biological functions, molecular robots, artificial cells, and next-generation smart drug delivery materials.

In-silico study on viability of MXenes in suppressing the coronavirus infection and distribution

Herein, based on the paramount importance of combating emerging diseases, through employing a detailed in-silico study, the possibility of using MXenes in suppressing the coronavirus infection was elucidated. To this end, first, interactions of MXene nanosheets (Mn₂C, Ti₂C, and Mo₂C) and spike protein (SP), the main infecting portion of the COVID-19, were investigated. It was found that the modeled MXenes were effective in attracting the SP, so that they can be exploited in filtering the coronavirus. In addition, the effect of the MXenes on the SP structure was assessed which demonstrated that the secondary structure of the SP could be changed. Therefore, the post-interactions of the SP/ACE2 (receptor of coronavirus in the body) could be interrupted, declaring the lower chance of coronavirus infecting. The in-silico studies revealed that the MXenes not only can be used to adsorb and hinder the distribution of the coronavirus but also affect the SP structure and the SP/ACE2 interactions to interrupt the COVID-19 threat. Therefore, MXenes can be exploited with simultaneous roles in physical inhibition and reactive weakening of the COVID-19. In this regard, the Mn₂C nanosheet was well suited, which is suggested as a promising candidate to combat the coronavirus.

Multiassay Profiling of a Focused Small Molecule Library Reveals Predictive Bidirectional Modulation of the lncRNA MALAT1 Triplex Stability In Vitro

The rapidly accelerating characterization of RNA tertiary structures has revealed their pervasiveness and active roles in human diseases. Small molecule-mediated modulation of RNA tertiary structures constitutes an attractive avenue for the development of tools for therapeutically targeting and/or uncovering the pathways associated with these RNA motifs. This potential has been highlighted by targeting of the triple helix present at the 3'-end of the noncoding RNA MALAT1, a transcript implicated in several human diseases. This triplex has been reported to decrease the susceptibility of the transcript to degradation and promote its cellular accumulation. While small molecules have been shown to bind to and impact the stability of the MALAT1 triple helix, the small molecule properties that lead to these structural modulations are not well understood. We designed a library utilizing the diminazene scaffold, which is underexplored but precedented for nucleic acid binding, to target the MALAT1 triple helix. We employed multiple assays to holistically assess what parameters, if any, could predict the small molecule affinity and effect on triplex stability. We designed and/or optimized competition, calorimetry, and thermal shift assays as well as an enzymatic degradation assay, the latter of which led to the discovery of bidirectional modulators of triple helix stability within the scaffold-centric library. Determination of quantitative structure-activity relationships afforded predictive models for both affinity- and stability-based assays. This work establishes a suite of powerful orthogonal biophysical tools for the evaluation of small molecule:RNA triplex interactions that generate predictive models and will allow small molecule interrogation of the growing body of disease-associated RNA triple helices.

Advances in the Structural Strategies of the Self-Assembly of Photoresponsive Supramolecular Systems

Photosensitive supramolecular systems have garnered attention due to their potential to catalyze highly specific tasks through structural changes triggered by a light stimulus. The tunability of their chemical structure and charge transfer properties provides opportunities for designing and developing smart materials for multidisciplinary applications. This review focuses on the approaches reported in the literature for tailoring properties of the photosensitive supramolecular systems, including MOFs, MOPs, and HOFs. We discuss relevant aspects regarding their chemical structure, action mechanisms, design principles, applications, and future perspectives.

Biomaterials-Mediated Tumor Infarction Therapy

Agents for tumor vascular infarction are recently developed therapeutic agents for the vascular destruction of tumors. They can suppress the progression of the tumor by preventing the flow of nutrition and oxygen to its tissues. Agents of tumor vascular infarction can be divided into three categories according to the differences in their pathways of action: those that use the thrombin-activating pathway, fibrin-activating pathway, and platelet-activating pathway. However, poor targeting ability, low permeation, and potential side-effects restrict the development of the corresponding drugs. Biomaterials can subtly avoid these drawbacks to suppress the tumor. In this article, the authors summarize currently used biomaterials for tumor infarction therapy with the goal of identifying its mechanism, and discuss outstanding deficiencies in methods of this kind.

Dithienylethene-Bridged Fluoroquinolone Derivatives for Imaging-Guided Reversible Control of Antibacterial Activity

The emerging field of photopharmacology has offered a promising alternative to guard against the bacterial resistance by effectively avoiding antibiotic accumulation in the body or environment. However, the degradation, toxicity, and thermal reversibility have always been an ongoing concern for potential applications of azobenzene-based photopharmacology. Developing novel photopharmacological agents based on a more matched switch is highly in demand and remains a major challenge. Herein, two novel dithienylethene-bridged dual-fluoroquinolone derivatives have been developed by introducing two fluoroquinolone drugs into both ends of the dithienylethene (DTE) switch, in which the fluoroquinolone acts as a fluorophore except for the pharmacodynamic component. For comparison, two monofluoroquinolone-DTE hybrids were also prepared by a similar strategy. As expected, these resultant DTE-based antibacterial agents displayed efficient photochromism and fluorescence switching behavior in dimethyl sulfoxide. Moreover, improved antibacterial activities compared to those of monofluoroquinolone derivatives and a maximum fourfold active difference against Escherichia coli (E. coli) for open and closed isomers and photoswitchable bacterial imaging for Staphylococcus aureus and E. coli were observed. The molecular docking to DNA gyrase gave a rationale for the discrepancies in antibacterial activity for both isomers. Therefore, these fluoroquinolone derivatives can act as interesting imaging-guided photopharmacological agents for further in vivo studies.

Photopharmacology of Antimitotic Agents

Antimitotic agents such as the clinically approved vinca alkaloids, taxanes and epothilone can arrest cell growth during interphase and are therefore among the most important drugs available for treating cancer. These agents suppress microtubule dynamics and thus interfere with intracellular transport, inhibit cell proliferation and promote cell death. Because these drugs target biological processes that are essential to all cells, they face an additional challenge when compared to most other drug classes. General toxicity can limit the applicable dose and therefore reduce therapeutic benefits. Photopharmacology aims to avoid these side-effects by introducing compounds that can be applied globally to cells in their inactive form, then be selectively induced to bioactivity in targeted cells or tissue during a defined time window. This review discusses photoswitchable analogues of antimitotic agents that have been developed by combining different photoswitchable motifs with microtubule-stabilizing or microtubule-destabilizing agents.

Reversible Regulation of Succinate Dehydrogenase by Tools of Photopharmacology

Succinate dehydrogenase (SDH) is extremely important in metabolic function and biological processes. Modulation of SDH has been reported to be a promising therapeutic target to SDH mutations. Current measures for the regulation of SDH are scarce, and precise and reversible modulation of SDH still remains challenging. Herein, a powerful tool for reversible optical control of SDH was proposed and evaluated utilizing the technology of photopharmacology. We reported photochromic ligands (PCLs), azobenzene-pyrazole amides (APAs), that exert light-dependent inhibition effects on SDH. Physicochemical property tests and biological assays were conducted to demonstrate the feasibility of modulating SDH. In this paper, common agricultural pathogens were used to develop a procedure by which our PCLs could reversibly and precisely control SDH utilizing green light. This research would help us to understand the target-ligand interactions and provide new insights into modulation of SDH.

Recent Approaches to the Identification of Novel Microtubule-Targeting Agents

Microtubules are key components of the eukaryotic cytoskeleton with essential roles in cell division, intercellular transport, cell morphology, motility, and signal transduction. They are composed of protofilaments of heterodimers of α-tubulin and β-tubulin organized as rigid hollow cylinders that can assemble into large and dynamic intracellular structures. Consistent with their involvement in core cellular processes, affecting microtubule assembly results in cytotoxicity and cell death. For these reasons, microtubules are among the most important targets for the therapeutic treatment of several diseases, including cancer. The vast literature related to microtubule stabilizers and destabilizers has been reviewed extensively in recent years. Here we summarize recent experimental and computational approaches for the identification of novel tubulin modulators and delivery strategies. These include orphan small molecules, PROTACs as well as light-sensitive compounds that can be activated with high spatio-temporal accuracy and that represent promising tools for precision-targeted chemotherapy.

Molecular photoswitches in aqueous environments

Molecular photoswitches enable dynamic control of processes with high spatiotemporal precision, using light as external stimulus, and hence are ideal tools for different research areas spanning from chemical biology to smart materials. Photoswitches are typically organic molecules that feature extended aromatic systems to make them responsive to (visible) light. However, this renders them inherently lipophilic, while water-solubility is of crucial importance to apply photoswitchable organic molecules in biological systems, like in the rapidly emerging field of photopharmacology. Several strategies for solubilizing organic molecules in water are known, but there are not yet clear rules for applying them to photoswitchable molecules. Importantly, rendering photoswitches water-soluble has a serious impact on both their photophysical and biological properties, which must be taken into consideration when designing new systems. Altogether, these aspects pose considerable challenges for successfully applying molecular photoswitches in aqueous systems, and in particular in biologically relevant media. In this review, we focus on fully water-soluble photoswitches, such as those used in biological environments, in both in vitro and in vivo studies. We discuss the design principles and prospects for water-soluble photoswitches to inspire and enable their future applications.

Pyrrole Hemithioindigo Antimitotics with Near-Quantitative Bidirectional Photoswitching that Photocontrol Cellular Microtubule Dynamics with Single-Cell Precision*

We report the first cellular application of the emerging near-quantitative photoswitch pyrrole hemithioindigo, by rationally designing photopharmaceutical PHTub inhibitors of the cytoskeletal protein tubulin. PHTubs allow simultaneous visible-light imaging and photoswitching in live cells, delivering cell-precise photomodulation of microtubule dynamics, and photocontrol over cell cycle progression and cell death. This is the first acute use of a hemithioindigo photopharmaceutical for high-spatiotemporal-resolution biological control in live cells. It additionally demonstrates the utility of near-quantitative photoswitches, by enabling a dark-active design to overcome residual background activity during cellular photopatterning. This work opens up new horizons for high-precision microtubule research using PHTubs and shows the cellular applicability of pyrrole hemithioindigo as a valuable scaffold for photocontrol of a range of other biological targets.

Recent Applications of Azo Dyes: A Paradigm Shift from Medicinal Chemistry to Biomedical Sciences

Azo molecules possess the characteristic azo bond (-N=N-) and are considered fascinating motifs in organic chemistry. Since the last century, these brightly colored compounds have been widely employed as dyes across several industries in applications for printing, food, paper, cosmetics, lasers, electronics, optics, material sciences, etc. The discovery of Prontosil, an antibacterial drug, propelled azo compounds into the limelight in the field of medicinal chemistry. Subsequent discoveries including Phenazopyridine, Basalazide, and Sulfasalazine enabled azo compounds to occupy a significant role in the drug market. Furthermore, azo compounds have been employed as antibacterial, antimalarial, antifungal, antioxidant, as well as antiviral agents. The metabolic degradation of many azo dyes can induce liver problems if ingested, posing a safety concern and limiting their application as azo dyes in medicinal chemistry. However, azo dyes remain particularly significant for applications in cancer chemotherapy. Recently, a paradigm shift has been observed in the use of azo dyes: from medicinal chemistry to biomedical sciences. The latter benefits from azo dye application are related to imaging, drug delivery, photo-pharmacology and photo switching. Herein, we have compiled and discussed recent works on azo dye compounds obtained so far, focusing on their medicinal importance and future prospects.

Targeted Cancer Therapy Using Compounds Activated by Light

Cancer chemotherapy is affected by a modest selectivity and toxic side effects of pharmacological interventions. Among novel approaches to overcome this limitation and to bring to therapy more potent and selective agents is the use of light for selective activation of anticancer compounds. In this review, we focus on the anticancer applications of two light-activated approaches still in the experimental phase: photoremovable protecting groups ("photocages") and photoswitches. We describe the structural considerations behind the development of novel compounds and the plethora of assays used to confirm whether the photochemical and pharmacological properties are meeting the stringent criteria for an efficient in vivo light-dependent activation. Despite its immense potential, light activation brings many challenges, and the complexity of the task is very demanding. Currently, we are still deeply in the phase of pharmacological tools, but the vivid research and rapid development bring the light of hope for potential clinical use.

Novel molecular hybrids of indoline spiropyrans and α-lipoic acid as potential photopharmacological agents: Synthesis, structure, photochromic and biological properties

Organic photochromic compounds are attracting great interest as photoswitchable components of various bioconjugates for using in photopharmacology, targeted drug delivery and bio-imaging. Here we report on the synthesis of two novel molecular hybrids of indoline spiropyrans and alpha-lipoic acid via an esterification reaction. Preliminary photochemical studies revealed photochromic activity of 5-methoxy-substituted spirocompounds in their acetonitrile solutions. Both hybrid spiropyrans along with their parent substances in the hybrids were tested for the short-term cytotoxicity on HeLa cell cultures. The results of cytotoxicity studies showed unpredictable biocompatibility of the hybrids in comparison with the parent hydroxyl-substituted spiropyrans and α-lipoic acid, especially at the relatively high concentration of 2 mM. Using flow cytometry, we demonstrated that the both hybrids induced antioxidant response in the model cells. After the 24 h treatment, the hybrids administered at lower (500 µM) concentration caused suppressed cytosolic ROS and/or induced cellular thiols. At higher concentration, one of the hybrids demonstrated properties qualitatively similar to alpha-lipoic acid, yet far more strong. Together, flow cytometry results suggested that both hybrids of spiropyrans possess emergent biochemical and signaling antioxidant properties, exceeding those of alpha-lipoic acid.

Development of novel derivatives of stilbene and macrocyclic compounds as potent of anti-microtubule factors

Microtubules (composed of α- and β-tubulin heterodimers) ubiquitous cellular polymers are important components of the cytoskeleton and play diverse roles within the cell, such as maintenance of cell structure, protein trafficking or chromosomal segregation during cell division. The polymers of tubulin play a pivotal role in mitosis and are regarded as an excellent target for chemotherapeutic agents to treat cancer. This review presents a brief overview of the synthesis and mechanism of action of new compounds targeting the dynamic of microtubule - tubulin polymerization/depolymerization. It is divided into the following parts: section I concerns targeting microtubules- tubulin-binding drugs derivatives of stilbene. In section II there are presented photoswitchable inhibitors of microtubule dynamics. Section III concerns using macrocyclic compounds as tubulin inhibitors. In this review, the authors focused primarily on reports produced inthe last five years and the latest strategies in this field.

Photoswitchable paclitaxel-based microtubule stabilisers allow optical control over the microtubule cytoskeleton

Small molecule inhibitors are prime reagents for studies in microtubule cytoskeleton research, being applicable across a range of biological models and not requiring genetic engineering. However, traditional chemical inhibitors cannot be experimentally applied with spatiotemporal precision suiting the length and time scales inherent to microtubule-dependent cellular processes. We have synthesised photoswitchable paclitaxel-based microtubule stabilisers, whose binding is induced by photoisomerisation to their metastable state. Photoisomerising these reagents in living cells allows optical control over microtubule network integrity and dynamics, cell division and survival, with biological response on the timescale of seconds and spatial precision to the level of individual cells within a population. In primary neurons, they enable regulation of microtubule dynamics resolved to subcellular regions within individual neurites. These azobenzene-based microtubule stabilisers thus enable non-invasive, spatiotemporally precise modulation of the microtubule cytoskeleton in living cells, and promise new possibilities for studying intracellular transport, cell motility, and neuronal physiology.

Light-based modulation of the microtubule (MT) cytoskeleton is an attractive goal for spatiotemporally-resolved MT studies. Here the authors develop a first generation photoswitchable small molecule MT stabiliser based on paclitaxel, allowing optical control over cellular MT dynamics.

Activation of Sirtuin 2 Inhibitors Employing Photoswitchable Geometry and Aqueous Solubility

Because isoenzymes of the experimentally and therapeutically extremely relevant sirtuin family show high similarity, addressing the unique selectivity pocket of sirtuin 2 is a promising strategy towards selective inhibitors. An unrelated approach towards selective inhibition of isoenzymes with varied tissue distribution is targeted drug delivery or spatiotemporal activation by photochemical activation. Azologization of two nicotinamide‐mimicking lead structures was undertaken to combine both approaches and yielded a set of 33 azobenzenes and azopyridines that have been evaluated for their photochemical behaviour and bioactivity. For some compounds, inhibitory activity reached the sub‐micromolar range in their thermodynamically favoured E form and could be decreased by photoisomerization to the metastable Z form. Besides, derivatization with long‐chain fatty acids yielded potent sirtuin 2 inhibitors, featuring another intriguing aspect of azo‐based photoswitches. In these compounds, switching to the Z isomer increased aqueous solubility and thereby enhanced biological activity by up to a factor of 21. The biological activity of two compounds was confirmed by hyperacetylation of sirtuin specific histone proteins in a cell‐based activity assay.

Photochromic meta-diamides for optical modulation of ligand activity and neuron function†

Photopharmacology offers facile solutions for spatiotemporal control over ligand activity and receptor function. The meta-diamide insecticide acts on insect GABA receptors (GABARs) as an antagonist that causes firing of a neuron. We present here photochromic GABAR ligands azobenzene-meta-diamides (ABMDAs) by incorporating photoswitchable azobenzene with meta-diamides. ABMDAs showed good isomerization efficiency and fatigue resistance. Among them, ABMDA7 shows a 1.5-fold insecticidal activity difference towards mosquito larvae (Aedes albopictus) before and after UV illumination. We translated this light-dependent activity difference to the optical modulation of the membrane potential of American cockroach (Periptaneta americana) DUM neurons. This light-responsive meta-diamide-based GABAR ligand allows for optical regulation of insecticidal activity and DUM neurons.

Strategies and considerations of G-protein-coupled receptor photopharmacology

G-protein-coupled receptor (GPCR) pharmacology tends to be complex and at times poorly understood. This has led to the development of GPCR-targeting agents that often demonstrate poor pharmacokinetic properties and poor selectivity for their target receptors. One approach that is emerging as a means of addressing these limitations is the use of molecules whose activity can be controlled by light. Photopharmacology involves the incorporation of a photoswitch into the structure of a given compound, cage or linker and following irradiation with light, undergoes a structural rearrangement, which changes its biological activity. The use of light-regulated ligands offers the opportunity to modulate and understand GPCR signaling in a more spatiotemporal manner than classical pharmacological approaches. In this chapter we will discuss some of the advancements that have been made in photopharmacology, particularly in developing photoswitchable ligands that target class A GPCRs, e.g., muscarinic acetylcholine receptors, class B GPCRs, e.g., glucagon-like peptide-1 receptor, and class C GPCRs, e.g., metabotrobic glutamate receptors. Given the intricacy of GPCR pharmacology, this chapter will also discuss some of the challenges the field faces when designing photopharmacological tools. Furthermore, it will propose that it is with a full appreciation of the spectrum of pharmacological and pharmacokinetic properties of photoswitchable ligands that research will be better placed to develop ligands with a reduced risk of failure during preclinical progression. This will likely enable photopharmacological approaches to continue to find novel applications and offer new perspectives in understanding (patho)physiology to ultimately inform future GPCR drug discovery efforts.

Colchicine-Binding Site Inhibitors from Chemistry to Clinic: A Review

It is over 50 years since the discovery of microtubules, and they have become one of the most important drug targets for anti-cancer therapies. Microtubules are predominantly composed of the protein tubulin, which contains a number of different binding sites for small-molecule drugs. There is continued interest in drug development for compounds targeting the colchicine-binding site of tubulin, termed colchicine-binding site inhibitors (CBSIs). This review highlights CBSIs discovered through diverse sources: from natural compounds, rational design, serendipitously and via high-throughput screening. We provide an update on CBSIs reported in the past three years and discuss the clinical status of CBSIs. It is likely that efforts will continue to develop CBSIs for a diverse set of cancers, and this review provides a timely update on recent developments.

Light-controlled inhibition of BRAFV600E kinase

Metastatic melanoma is amongst the most difficult types of cancer to treat, with current therapies mainly relying on the inhibition of the BRAF^V600E mutant kinase. However, systemic inhibition of BRAF by small molecule drugs in cancer patients results - paradoxically - in increased wild-type BRAF activity in healthy tissue, causing side-effects and even the formation of new tumors. Here we show the development of BRAF^V600E kinase inhibitors of which the activity can be switched on and off reversibly with light, offering the possibility to overcome problems of systemic drug activity by selectively activating the drug at the desired site of action. Based on a known inhibitor, eight photoswitchable effectors containing an azobenzene photoswitch were designed, synthesized and evaluated. The most promising inhibitor showed an approximately 10-fold increase in activity upon light-activation. This research offers inspiration for the development of therapies for metastatic melanoma in which tumor tissue is treated with an active BRAF^V600E inhibitor with high spatial and temporal resolution, thus limiting the damage to other tissues.

Mapping the Azolog Space Enables the Optical Control of New Biological Targets

Photopharmacology relies on molecules that change their biological activity upon irradiation. Many of these are derived from known drugs by replacing their core with an isosteric azobenzene photoswitch (azologization). The question is how many of the known bioactive ligands could be addressed in such a way. Here, we systematically assess the space of molecules amenable to azologization from databases of bioactive molecules (DrugBank, PDB, CHEMBL) and the Cambridge Structural Database. Shape similarity scoring functions (3DAPfp) and analyses of dihedral angles are employed to quantify the structural homology between a bioactive molecule and the cis or trans isomer of its corresponding azolog ("azoster") and assess which isomer is likely to be active. Our analysis suggests that a very large number of bioactive ligands (>40 000) is amenable to azologization and that many new biological targets could be addressed with photopharmacology. N-Aryl benzamides, 1,2-diarylethanes, and benzyl phenyl ethers are particularly suited for this approach, while benzylanilines and sulfonamides appear to be less well-matched. On the basis of our analysis, the majority of azosters are expected to be active in their trans form. The broad applicability of our approach is demonstrated with photoswitches that target a nuclear hormone receptor (RAR) and a lipid processing enzyme (LTA4 hydrolase).

Photoswitchable affinity reagents: Computational design and efficient red-light switching

Photo-controlled affinity reagents seek to provide modular spatiotemporal control of bioactivity by conferring photo-switchability of function on an affinity reagent scaffold. Here we used Rosetta-based computational methods to screen for sites on the Fynomer affinity reagent structure for attachment of photoswitchable cross-linkers. Both established UV-based cross-linkers (azobenzene-iodoacetamide (IAC)) and an azonium-based efficient red light switchable cross-linker, piperazino-tetra-ortho-methoxy azobenzene (PIP), were then tested experimentally. Several sites compatible with Fynomer function were identified, including sites showing rapid (<10s) red light (633 nm) modulation of function. While a range of overall target binding affinities were observed, the degree of photo-switchability of Fynomer function was generally small (<2-fold). Computational models suggest that local flexibility limits the degree of switching seen in these designs.