Highly biased agonism for GPCR ligands via nanobody tethering.

Ligand-induced activation of G protein-coupled receptors (GPCRs) can initiate signaling through multiple distinct pathways with differing biological and physiological outcomes. There is intense interest in understanding how variation in GPCR ligand structure can be used to promote pathway selective signaling ("biased agonism") with the goal of promoting desirable responses and avoiding deleterious side effects. Here we present an approach in which a conventional peptide ligand for the type 1 parathyroid hormone receptor (PTHR1) is converted from an agonist which induces signaling through all relevant pathways to a compound that is highly selective for a single pathway. This is achieved not through variation in the core structure of the agonist, but rather by linking it to a nanobody tethering agent that binds with high affinity to a separate site on the receptor not involved in signal transduction. The resulting conjugate represents the most biased agonist of PTHR1 reported to date. This approach holds promise for facile generation of pathway selective ligands for other GPCRs.

Surface-normal illuminated pseudo-planar Ge-on-Si avalanche photodiodes with high gain and low noise.

Germanium-on-Silicon (Ge-on-Si) avalanche photodiodes (APDs) are of considerable interest as low intensity light detectors for emerging applications. The Ge absorption layer detects light at wavelengths up to ≈ 1600 nm with the Si acting as an avalanche medium, providing high gain with low excess avalanche noise. Such APDs are typically used in waveguide configurations as growing a sufficiently thick Ge absorbing layer is challenging. Here, we report on a new vertically illuminated pseudo-planar Ge-on-Si APD design utilizing a 2 µm thick Ge absorber and a 1.4 µm thick Si multiplication region. At a wavelength of 1550 nm, 50 µm diameter devices show a responsivity of 0.41 A/W at unity gain, a maximum avalanche gain of 101 and an excess noise factor of 3.1 at a gain of 20. This excess noise factor represents a record low noise for all configurations of Ge-on-Si APDs. These APDs can be inexpensively manufactured and have potential integration in silicon photonic platforms allowing use in a variety of applications requiring high-sensitivity detectors at wavelengths around 1550 nm.

Intratumoral delivery of the chitin-derived C100 adjuvant promotes robust STING, IFNAR, and CD8+ T cell-dependent anti-tumor immunity.

Stimulator of IFN genes (STING) is a promising target for adjuvants utilized in in situ cancer vaccination approaches. However, key barriers remain for clinical translation, including low cellular uptake and accessibility, STING variability necessitating personalized STING agonists, and interferon (IFN)-independent signals that can promote tumor growth. Here, we identify C100, a highly deacetylated chitin-derived polymer (HDCP), as an attractive alternative to conventional STING agonists. C100 promotes potent anti-tumor immune responses, outperforming less deacetylated HDCPs, with therapeutic efficacy dependent on STING and IFN alpha/beta receptor (IFNAR) signaling and CD8+ T cell mediators. Additionally, C100 injection synergizes with systemic checkpoint blockade targeting PD-1. Mechanistically, C100 triggers mitochondrial stress and DNA damage to exclusively activate the IFN arm of the cGAS-STING signaling pathway and elicit sustained IFNAR signaling. Altogether, these results reveal an effective STING- and IFNAR-dependent adjuvant for in situ cancer vaccines with a defined mechanism and distinct properties that overcome common limitations of existing STING therapeutics.

CSF neurofilament light chain profiling and quantitation in neurological diseases.

Neurofilament light chain is an established marker of neuroaxonal injury that is elevated in CSF and blood across various neurological diseases. It is increasingly used in clinical practice to aid diagnosis and monitor progression and as an outcome measure to assess safety and efficacy of disease-modifying therapies across the clinical translational neuroscience field. Quantitative methods for neurofilament light chain in human biofluids have relied on immunoassays, which have limited capacity to describe the structure of the protein in CSF and how this might vary in different neurodegenerative diseases. In this study, we characterized and quantified neurofilament light chain species in CSF across neurodegenerative and neuroinflammatory diseases and healthy controls using targeted mass spectrometry. We show that the quantitative immunoprecipitation-tandem mass spectrometry method developed in this study strongly correlates to single-molecule array measurements in CSF across the broad spectrum of neurodegenerative diseases and was replicable across mass spectrometry methods and centres. In summary, we have created an accurate and cost-effective assay for measuring a key biomarker in translational neuroscience research and clinical practice, which can be easily multiplexed and translated into clinical laboratories for the screening and monitoring of neurodegenerative disease or acute brain injury.

Effects of Age on Cross-Cultural Differences in the Neural Correlates of Memory Retrieval.

Culture can shape memory, but little research investigates age effects. The present study examines the neural correlates of memory retrieval for old, new, and similar lures in younger and older Americans and Taiwanese. Results show that age and culture impact discrimination of old from new items. Taiwanese performed worse than Americans, with age effects more pronounced for Taiwanese. Americans activated the hippocampus for new more than old items, but pattern of activity for the conditions did not differ for Taiwanese, nor did it interact with age. The engagement of left inferior frontal gyrus (LIFG) differed across cultures. Patterns of greater activity for old (for Americans) or new (for Taiwanese) items were eliminated with age, particularly for older Americans. The results are interpreted as reflecting cultural differences in orientation to novelty vs. familiarity for younger, but not older, adults, with the LIFG supporting interference resolution at retrieval. Support is not as strong for cultural differences in pattern separation processes. Although Americans had higher levels of memory discrimination than Taiwanese and engaged the LIFG for correct rejections more than false alarms, the patterns of behavior and neural activity did not interact with culture and age. Neither culture nor age impacted hippocampal activity, which is surprising given the region's role in pattern separation. The findings suggest ways in which cultural life experiences and concomitant information processing strategies can contribute to consistent effects of age across cultures or contribute to different trajectories with age in terms of memory.

Transforming Otolaryngology-Head and Neck Surgery: The Pivotal Role of Artificial Intelligence in Clinical Workflows.

Use of artificial intelligence (AI) is expanding exponentially as it pertains to workflow operations. Otolaryngology-Head and Neck Surgery (OHNS), as with all medical fields, is just now beginning to realize the exciting upsides of AI as it relates to patient care but otolaryngologists should also be critical when considering using AI solutions. This paper highlights how AI can optimize clinical workflows in the outpatient, inpatient, and surgical settings while also discussing some of the possible drawbacks with the burgeoning technology.

Protocol for the development of mRNA lipid nanoparticle vaccines and analysis of immunization efficiency in mice.

Here, we present a protocol for the development of mRNA-loaded lipid nanoparticle (LNP) vaccines for target antigen sequences of interest. We describe key steps required to design and synthesize mRNA constructs, their LNP encapsulation, and mouse immunization. We then detail quality control assays to determine RNA purity, guidelines to measure RNA immunogenicity using in vitro reporter systems, and a technique to evaluate antigen-specific T cell responses following immunization.

Sortase-mediated labeling: Expanding frontiers in site-specific protein functionalization opens new research avenues.

New applications for biomolecules demand novel approaches for their synthesis and modification. Traditional methods for modifying proteins and cells using non-specific labeling chemistry are insufficiently precise to rigorously interrogate the mechanistic biological and physiological questions at the forefront of biomedical science. Site-specific catalytic modification of proteins promises to meet these challenges. Here, we describe recent applications of the enzyme sortase A in facilitating precise biomolecule labeling. We focus on describing new chemistries to broaden the scope of sortase-mediated labeling (sortagging), the development of new probes for imaging via enzymatic labeling, and the modulation of biological systems using probes and reactions mediated by sortase.

Amyloid pathology and vascular risk are associated with distinct patterns of cerebral white matter hyperintensities: A multicenter study in 3132 memory clinic patients.

INTRODUCTION: White matter hyperintensities (WMH) are associated with key dementia etiologies, in particular arteriolosclerosis and amyloid pathology. We aimed to identify WMH locations associated with vascular risk or cerebral amyloid-ß1-42 (Aß42)-positive status. METHODS: Individual patient data (n = 3,132; mean age 71.5 ± 9 years; 49.3% female) from 11 memory clinic cohorts were harmonized. WMH volumes in 28 regions were related to a vascular risk compound score (VRCS) and Aß42 status (based on cerebrospinal fluid or amyloid positron emission tomography), correcting for age, sex, study site, and total WMH volume. RESULTS: VRCS was associated with WMH in anterior/superior corona radiata (B = 0.034/0.038, p < 0.001), external capsule (B = 0.052, p < 0.001), and middle cerebellar peduncle (B = 0.067, p < 0.001), and Aß42-positive status with WMH in posterior thalamic radiation (B = 0.097, p < 0.001) and splenium (B = 0.103, p < 0.001). DISCUSSION: Vascular risk factors and Aß42 pathology have distinct signature WMH patterns. This regional vulnerability may incite future studies into how arteriolosclerosis and Aß42 pathology affect the brain's white matter. HIGHLIGHTS: Key dementia etiologies may be associated with specific patterns of white matter hyperintensities (WMH). We related WMH locations to vascular risk and cerebral Aß42 status in 11 memory clinic cohorts. Aß42 positive status was associated with posterior WMH in splenium and posterior thalamic radiation. Vascular risk was associated with anterior and infratentorial WMH. Amyloid pathology and vascular risk have distinct signature WMH patterns.

Nanobody-Mediated Dualsteric Engagement of the Angiotensin Receptor Broadens Biased Ligand Pharmacology.

Dualsteric G protein-coupled receptor (GPCR) ligands are a class of bitopic ligands that consist of an orthosteric pharmacophore, which binds to the pocket occupied by the receptor's endogenous agonist, and an allosteric pharmacophore, which binds to a distinct site. These ligands have the potential to display characteristics of both orthosteric and allosteric ligands. To explore the signaling profiles that dualsteric ligands of the angiotensin II type 1 receptor (AT1R) can access, we ligated a 6e epitope tag-specific nanobody (single-domain antibody fragment) to angiotensin II (AngII) and analogs that show preferential allosteric coupling to Gq (TRV055, TRV056) or ß-arrestin (TRV027). While the nanobody itself acts as a probe-specific neutral or negative allosteric ligand of N-terminally 6e-tagged AT1R, nanobody conjugation to orthosteric ligands had varying effects on Gq dissociation and ß-arrestin plasma membrane recruitment. The potency of certain AngII analogs was enhanced up to 100-fold, and some conjugates behaved as partial agonists, with up to a 5-fold decrease in maximal efficacy. Nanobody conjugation also biased the signaling of TRV055 and TRV056 toward Gq, suggesting that Gq bias at AT1R can be modulated through molecular mechanisms distinct from those previously elucidated. Both competition radioligand binding experiments and functional assays demonstrated that orthosteric antagonists (angiotensin receptor blockers) act as non-competitive inhibitors of all these nanobody-peptide conjugates. This proof-of-principle study illustrates the array of pharmacological patterns that can be achieved by incorporating neutral or negative allosteric pharmacophores into dualsteric ligands. Nanobodies directed toward linear epitopes could provide a rich source of allosteric reagents for this purpose. SIGNIFICANCE STATEMENT: Here we engineer bitopic (dualsteric) ligands for epitope-tagged angiotensin II type 1 receptor by conjugating angiotensin II or its biased analogs to an epitope-specific nanobody (antibody fragment). Our data demonstrate that nanobody-mediated interactions with the receptor N-terminus endow angiotensin analogs with properties of allosteric modulators and provide a novel mechanism to increase the potency, modulate the maximal effect, or alter the bias of ligands.

Cross-cultural comparison of the neural correlates of true and false memory retrieval.

Prior work has shown Americans have higher levels of memory specificity than East Asians. Neuroimaging studies have not investigated mechanisms that account for cultural differences at retrieval. In this study, we use fMRI to assess whether mnemonic discrimination, distinguishing novel from previously encountered stimuli, accounts for cultural differences in memory. Fifty-five American and 55 Taiwanese young adults completed an object recognition paradigm testing discrimination of old targets, similar lures and novel foils. Mnemonic discrimination was tested by comparing discrimination of similar lures from studied targets, and results showed the relationship between activity in left fusiform gyrus and behavioural discrimination between target and lure objects differed across cultural groups. Parametric modulation analyses of activity during lure correct rejections also indicated that groups differed in left superior parietal cortex response to variations in lure similarity. Additional analyses of old vs. new activity indicated that Americans and Taiwanese differ in the neural activity supporting general object recognition in the hippocampus, left inferior frontal gyrus and middle frontal gyrus. Results are juxtaposed against comparisons of the regions activated in common across the two cultures. Overall, Americans and Taiwanese differ in the extent to which they recruit visual processing and attention modulating brain regions.

Semi-synthetic nanobody-ligand conjugates exhibit tunable signaling properties and enhanced transcriptional outputs at neurokinin receptor-1.

Antibodies have proven highly valuable for therapeutic development; however, they are typically poor candidates for applications that require activation of G protein-coupled receptors (GPCRs), the largest collection of targets for clinically approved drugs. Nanobodies (Nbs), the smallest antibody fragments retaining full antigen-binding capacity, have emerged as promising tools for pharmacologic applications, including GPCR modulation. Past work has shown that conjugation of Nbs with ligands can provide GPCR agonists that exhibit improved activity and selectivity compared to their parent ligands. The neurokinin-1 receptor (NK1R), a GPCR targeted for the treatment of pain, is activated by peptide agonists such as Substance P (SP) and neurokinin A (NKA), which induce signaling through multiple pathways (Gs , Gq and ß-arrestin). In this study, we investigated whether conjugating NK1R ligands with Nbs that bind to a separate location on the receptor would provide chimeric compounds with distinctive signaling properties. We employed sortase A-mediated ligation to generate several conjugates consisting of Nbs linked to NK1R ligands. Many of these conjugates exhibited divergent and unexpected signaling properties and transcriptional outputs. For example, some Nb-NKA conjugates showed enhanced receptor binding capacity, high potency partial agonism, prolonged cAMP production, and an increase in transcriptional output associated with Gs signaling; whereas other conjugates were virtually inactive. Nanobody conjugation caused only minor alterations in ligand-induced upstream Gq signaling with unexpected enhancements in transcriptional (downstream) responses. Our findings underscore the potential of nanobody conjugation for providing compounds with advantageous properties such as biased agonism, prolonged duration of action, and enhanced transcriptional responses. These compounds hold promise not only for facilitating fundamental research on GPCR signal transduction mechanisms but also for the development of more potent and enduring therapeutics.

Rational design of polymer-based particulate vaccine adjuvants.

Vaccination is considered one of the major milestones in modern medicine, facilitating the control and eradication of life-threatening infectious diseases. Vaccine adjuvants are a key component of many vaccines, serving to steer antigen-specific immune responses and increase their magnitude. Despite major advances in the field of adjuvant research over recent decades, our understanding of their mechanism of action remains incomplete. This hinders our capacity to further improve these adjuvant technologies, so addressing how adjuvants induce and control the induction of innate and adaptive immunity is a priority. Investigating how adjuvant physicochemical properties, such as size and charge, exert immunomodulatory effects can provide valuable insights and serve as the foundation for the rational design of vaccine adjuvants. Most clinically applied adjuvants are particulate in nature and polymeric particulate adjuvants present advantages due to stability, biocompatibility profiles, and flexibility in terms of formulation. These properties can impact on antigen release kinetics and biodistribution, cellular uptake and targeting, and drainage to the lymphatics, consequently dictating the induction of innate, cellular, and humoral adaptive immunity. A current focus is to apply rational design principles to the development of adjuvants capable of eliciting robust cellular immune responses including CD8+ cytotoxic T-cell and Th1-biased CD4+ T-cell responses, which are required for vaccines against intracellular pathogens and cancer. This review highlights recent advances in our understanding of how particulate adjuvants, especially polymer-based particulates, modulate immune responses and how this can be used as a guide for improved adjuvant design.

The Past, Present, and Future of the Brain Imaging Data Structure (BIDS).

The Brain Imaging Data Structure (BIDS) is a community-driven standard for the organization of data and metadata from a growing range of neuroscience modalities. This paper is meant as a history of how the standard has developed and grown over time. We outline the principles behind the project, the mechanisms by which it has been extended, and some of the challenges being addressed as it evolves. We also discuss the lessons learned through the project, with the aim of enabling researchers in other domains to learn from the success of BIDS.

Microbiome and plant cell transformation trigger insect gall induction in cassava.

Several specialised insects can manipulate normal plant development to induce a highly organised structure known as a gall, which represents one of the most complex interactions between insects and plants. Thus far, the mechanism for insect-induced plant galls has remained elusive. To study the induction mechanism of insect galls, we selected the gall induced by Iatrophobia brasiliensis (Diptera: Cecidomyiidae) in cassava (Euphorbiaceae: Manihot esculenta Crantz) as our model. PCR-based molecular markers and deep metagenomic sequencing data were employed to analyse the gall microbiome and to test the hypothesis that gall cells are genetically transformed by insect vectored bacteria. A shotgun sequencing discrimination approach was implemented to selectively discriminate between foreign DNA and the reference host plant genome. Several known candidate insertion sequences were identified, the most significant being DNA sequences found in bacterial genes related to the transcription regulatory factor CadR, cadmium-transporting ATPase encoded by the cadA gene, nitrate transport permease protein (nrtB gene), and arsenical pump ATPase (arsA gene). In addition, a DNA fragment associated with ubiquitin-like gene E2 was identified as a potential accessory genetic element involved in gall induction mechanism. Furthermore, our results suggest that the increased quality and rapid development of gall tissue are mostly driven by microbiome enrichment and the acquisition of critical endophytes. An initial gall-like structure was experimentally obtained in M. esculenta cultured tissues through inoculation assays using a Rhodococcus bacterial strain that originated from the inducing insect, which we related to the gall induction process. We provide evidence that the modification of the endophytic microbiome and the genetic transformation of plant cells in M. esculenta are two essential requirements for insect-induced gall formation. Based on these findings and having observed the same potential DNA marker in galls from other plant species (ubiquitin-like gene E2), we speculate that bacterially mediated genetic transformation of plant cells may represent a more widespread gall induction mechanism found in nature.

Identification and high-throughput genotyping of single nucleotide polymorphism markers in a non-model conifer (Abies nordmanniana (Steven) Spach).

Single nucleotide polymorphism (SNP) markers are powerful tools for investigating population structures, linkage analysis, and genome-wide association studies, as well as for breeding and population management. The availability of SNP markers has been limited to the most commercially important timber species, primarily due to the cost of genome sequencing required for SNP discovery. In this study, a combination of reference-based and reference-free approaches were used to identify SNPs in Nordmann fir (Abies nordmanniana), a species previously lacking genomic sequence information. Using a combination of a genome assembly of the closely related Silver fir (Abies alba) species and a de novo assembly of low-copy regions of the Nordmann fir genome, we identified a high density of reliable SNPs. Reference-based approaches identified two million SNPs in common between the Silver fir genome and low-copy regions of Nordmann fir. A combination of one reference-free and two reference-based approaches identified 250 shared SNPs. A subset of 200 SNPs were used to genotype 342 individuals and thereby tested and validated in the context of identity analysis and/or clone identification. The tested SNPs successfully identified all ramets per clone and five mislabeled individuals via identity and genomic relatedness analysis. The identified SNPs will be used in ad hoc breeding of Nordmann fir in Denmark.

Spatial distributions of white matter hyperintensities on brain MRI: A pooled analysis of individual participant data from 11 memory clinic cohorts.

INTRODUCTION: The spatial distribution of white matter hyperintensities (WMH) on MRI is often considered in the diagnostic evaluation of patients with cognitive problems. In some patients, clinicians may classify WMH patterns as "unusual", but this is largely based on expert opinion, because detailed quantitative information about WMH distribution frequencies in a memory clinic setting is lacking. Here we report voxel wise 3D WMH distribution frequencies in a large multicenter dataset and also aimed to identify individuals with unusual WMH patterns. METHODS: Individual participant data (N = 3525, including 777 participants with subjective cognitive decline, 1389 participants with mild cognitive impairment and 1359 patients with dementia) from eleven memory clinic cohorts, recruited through the Meta VCI Map Consortium, were used. WMH segmentations were provided by participating centers or performed in Utrecht and registered to the Montreal Neurological Institute (MNI)-152 brain template for spatial normalization. To determine WMH distribution frequencies, we calculated WMH probability maps at voxel level. To identify individuals with unusual WMH patterns, region-of-interest (ROI) based WMH probability maps, rule-based scores, and a machine learning method (Local Outlier Factor (LOF)), were implemented. RESULTS: WMH occurred in 82% of voxels from the white matter template with large variation between subjects. Only a small proportion of the white matter (1.7%), mainly in the periventricular areas, was affected by WMH in at least 20% of participants. A large portion of the total white matter was affected infrequently. Nevertheless, 93.8% of individual participants had lesions in voxels that were affected in less than 2% of the population, mainly located in subcortical areas. Only the machine learning method effectively identified individuals with unusual patterns, in particular subjects with asymmetric WMH distribution or with WMH at relatively rarely affected locations despite common locations not being affected. DISCUSSION: Aggregating data from several memory clinic cohorts, we provide a detailed 3D map of WMH lesion distribution frequencies, that informs on common as well as rare localizations. The use of data-driven analysis with LOF can be used to identify unusual patterns, which might serve as an alert that rare causes of WMH should be considered.

Semi-synthetic nanobody-ligand conjugates exhibit tunable signaling properties and enhanced transcriptional outputs at neurokinin receptor-1.

Antibodies have proven highly valuable for therapeutic development; however, they are typically poor candidates for applications that require activation of G protein-coupled receptors (GPCRs), the largest collection of targets for clinically approved drugs. Nanobodies (Nbs), the smallest antibody fragments retaining full antigen-binding capacity, have emerged as promising tools for pharmacologic applications, including GPCR modulation. Past work has shown that conjugation of Nbs with ligands can provide GPCR agonists that exhibit improved activity and selectivity compared to their parent ligands. The neurokinin-1 receptor (NK1R), a GPCR targeted for the treatment of pain, is activated by peptide agonists such as Substance P (SP) and neurokinin A (NKA), which induce signaling through multiple pathways (Gs, Gq and ß-arrestin). In this study, we investigated whether conjugating NK1R ligands with Nbs that bind to a separate location on the receptor would provide chimeric compounds with distinctive signaling properties. We employed sortase A-mediated ligation to generate several conjugates consisting of Nbs linked to NK1R ligands. Many of these conjugates exhibited divergent and unexpected signaling properties and transcriptional outputs. For example, some Nb-NKA conjugates showed enhanced receptor binding capacity, high potency partial agonism, prolonged cAMP production, and an increase in transcriptional output associated with Gs signaling; whereas other conjugates were virtually inactive. Nanobody conjugation caused only minor alterations in ligand-induced upstream Gq signaling with unexpected enhancements in transcriptional (downstream) responses. Our findings underscore the potential of nanobody conjugation for providing compounds with advantageous properties such as biased agonism, prolonged duration of action, and enhanced transcriptional responses. These compounds hold promise not only for facilitating fundamental research on GPCR signal transduction mechanisms but also for the development of more potent and enduring therapeutics.

Highly biased agonism for GPCR ligands via nanobody tethering.

Ligand-induced activation of G protein-coupled receptors (GPCRs) can initiate signaling through multiple distinct pathways with differing biological and physiological outcomes. There is intense interest in understanding how variation in GPCR ligand structure can be used to promote pathway selective signaling ("biased agonism") with the goal of promoting desirable responses and avoiding deleterious side effects. Here we present a new approach in which a conventional peptide ligand for the type 1 parathyroid hormone receptor (PTHR1) is converted from an agonist which induces signaling through all relevant pathways to a compound that is highly selective for a single pathway. This is achieved not through variation in the core structure of the agonist, but rather by linking it to a nanobody tethering agent that binds with high affinity to a separate site on the receptor not involved in signal transduction. The resulting conjugate represents the most biased agonist of PTHR1 reported to date. This approach holds promise for facile generation of pathway selective ligands for other GPCRs.

Anomalous photochromism and mechanochromism of a linear naphthopyran enabled by a polarizing dialkylamine substituent.

In contrast to common angular naphthopyrans that exhibit strong photochromic and mechanochromic behavior, constitutionally isomeric linear naphthopyrans are typically not photochromic, due to the putative instability of the completely dearomatized merocyanine product. The photochemistry of linear naphthopyrans is thus relatively understudied compared to angular naphthopyrans, while the mechanochromism of linear naphthopyrans remains completely unexplored. Here we demonstrate that the incorporation of a polarizing dialkylamine substituent enables photochromic and mechanochromic behavior from polymers containing a novel linear naphthopyran motif. In solution phase experiments, a Lewis acid trap was necessary to observe accumulation of the merocyanine product upon photochemical and ultrasound-induced mechanochemical activation. However, the same linear naphthopyran molecule incorporated as a crosslinker in polydimethylsiloxane elastomers renders the materials photochromic and mechanochromic without the addition of any trapping agent. This study provides insights into the photochromic and mechanochromic reactivity of linear naphthopyrans that have conventionally been considered functionally inert, adding a new class of naphthopyran molecular switches to the repertoire of stimuli-responsive polymers.