Speakers

Detection of an off-pathway intermediate to fibril formation in an RNA-recognition motif

Electricity from Acid-Base Chemistry.

Photoport: Harnessing Light for Efficient Ion Transport Across Lipid Membranes

Transporting ions through lipid-based membranes is a key biophysical activity existing in living organisms, which is highly significant for cellular communication, balance and energy expenditure. Recently developed light-activated systems have created new horizons for for controlling ion movement with spatial and temporal precision. This presentation explores the development of Photoport, a light-responsive platform designed to efficiently facilitate ion transport across lipid bilayers. By utilizing photoisomerization and photocleavage based processes, Photoport enables precise control over artificial ion transporters, mimicking natural processes while offering tunable external triggers. The molecular designs of different phototransporters shall be discussed, and it will include such aspects such as photoreversible ion gating and selective ion permeability. The effect of the light-mediated structural changes on transport properties will be treated in great detail. Applications of Photoport in membrane systems, such as cancer targeting, will also be discussed.

Ligands as Gatekeepers in Quantum Dot Photocatalysis.

High Entropy Half Heuslers for enhanced thermoelectric figure of merit: The case of ZrHfNiCoSnSb

Versatile Reactivity of Diazo Carbonyl Compounds Towards Metal Catalysts and Visible Light

Probing nucleic acid architecture and function using responsive nucleoside

DNA and RNA polymerases and nucleotide transferases are widely used in introducing functionalities that aid in the structural and functional analysis of nucleic acids. This process greatly relies on the ability of native and engineered enzymes to incorporate functionalized nucleotides into oligonucleotides. While polymerases can process a wide variety of structurally diverse nucleotide substrates, currently available data does not provide an adequate understanding of the underlying mechanism that enables the enzyme to accept such unnatural nucleotides. For a decade now, we have been developing microenvironment- sensitive nucleoside/nucleotide analogs that help in probing the structure and ligand binding properties of therapeutically relevant nucleic acid motifs. We have leveraged the microenvironment sensitivity of C5-heterocycle-modified dUTP substrates to probe the incorporation mechanism and chemical space tolerance of DNA polymerases. In this presentation, I will describe the development of a probe platform using our dual-functional nucleotide probes to study the polymerase activity in real time and at the atomic level by using a combination of fluorescence, 19F NMR and X-ray crystallography techniques. The findings from our studies further expand the limited knowledge on the interplay between the polymerases and chemically diverse substrates, and build a basis for developing nucleotide probes for advanced applications.

Development of Converging Chemical Biology Technologies : Towards Industry-Academia Collaboration and Deep Science Startups.

N-heterocyclic silylene supported coinage metal complexes: from bonding to application.

Mixed Surfactant Systems

Synthesis Characterization and Redox Chemistry of Open Shell Twisted Alkene

Reactive Phase Separated Droplets as Self-assembly Templates

Plasmonic Antenna-Reactor Photocatalysts Based on Anisotropic Gold-Rhodium Constructs for Biological Cofactor Regeneration

Plasmonic nanomaterials of Au, Ag, Cu, and Al have emerged as an important class of photocatalysts because of their exceptionally high light absorption capabilities, which enable them to carry out challenging chemical transformations. However, their low chemical affinity towards most of the reactant molecules presents fundamental limitations such as low yield and selectivity in sole plasmonic photocatalysis.3 In recent years, researchers have developed strategies to enhance the charge separation and extraction processes by modulating the catalyst-reactant interaction and designing plasmonic antenna-reactor systems. In an antenna-reactor system, a plasmonic component concentrates the light energy, and an attached non-plasmonic component extracts this energy to generate hot charge carriers to carry out chemical transformations.1 In this direction, our group has prepared antenna-reactor systems comprising gold-rhodium constructs (AuNP-Rh NFs and AuNR-Rh SSs) and precisely modified the surface chemistry to study the effect of shape anisotropy in carrying out the photocatalytic regeneration of nicotinamide cofactor (NAD(P)H). NAD(P)H is an essential cofactor used by oxidoreductase enzymes in various biocatalytic reactions, and its regeneration using light is an important area in biocatalysis. Functionalized AuNR-Rh SSs showed better photocatalytic activity compared to AuNP-Rh NFs as well as sole plasmonic photocatalysts towards the regeneration of NADH, which was attributed to the (i) enhanced catalyst-mediator interaction, (ii) antenna-reactor effect, and (iii) shape anisotropy. The photocatalytic performance was retained for at least five cycles, establishing Au-Rh constructs as a promising antenna-reactor system for future photocatalytic NAD(P)H regeneration.

Heparin Neutralization Using Guanidine-Heparan Sulfate

Heparin is a widely used anticoagulant in clinical settings, but its overuse or accidental overdose can lead to serious bleeding complications. Protamine sulfate has long served as the standard antidote; however, its potential for adverse effects such as anaphylaxis and thrombocytopenia has prompted the search for safer, more efficient alternatives. In this study, we report the discovery of guanidine-based heparan sulfate mimetics as novel antidotes for heparin. Guanidine's strong basicity and capacity for electrostatic interactions allow it to effectively bind to heparin's negatively charged sulfate groups, neutralizing its anticoagulant properties. By using structure-guided design, we synthesized and evaluated a series of guanidine HS trisaccharides for their heparin-binding affinity and neutralization capacity. In vitro assays demonstrated that guanidine compounds could rapidly neutralize various forms of heparin. The binding mechanism was confirmed through NMR, which revealed strong electrostatic and hydrogen-bonding interactions between guanidine groups and heparin's sulfate chains. These findings suggest that guanidine HS represent a promising new class of heparin antidotes with potential advantages over protamine in terms of safety, efficacy, and specificity. Further in vivo studies are warranted to explore their therapeutic applications and pharmacological profiles.

DNA Polymerase-Mediated Incorporation of Clickable Nucleotide Analogs for Post-Replication Functionalization of DNA

DNA polymerase-catalysed incorporation of modified nucleotides is employed in many biotechnological applications, such as next-generation sequencing, nucleic acid-based diagnostics, SELEX etc. Researchers have developed various modified nucleotides with reactive handles that are well accepted by DNA polymerases for deploying functional tags through post-synthetic DNA functionalization using biorthogonal chemistry. In this context, the widespread applications of click chemistry based post-synthetic DNA modification have been extensively employed for purposes such as visualization, imaging, and tagging etc. Azide modified nucleotides are important class of compounds utilized extensively for modifying DNA using copper catalysed and strain promoted click chemistry (CuAAC & SPAAC) for aforementioned application. In this context, we report a class of azide modified nucleotide analogs (dN*TPs) having different chain length modified at the C5 position of thymidine have been well accepted by family A (KlenTaq) and family B (Kod) DNA polymerases in PEX. Using these modifications we have also developed site specific DNA labeling technique for post synthetic click chemistry. Moreover, crystal structure of azide modified nucleotide bound to KlenTaq DNA polymerase and a primer•template complex provides insights into the incorporation of modified nucleotide analogs within the enzymatic cavity and reveals the interactions between the modified nucleotide and the amino acid residues.

Nano-springe Enriched Hierarchical Porous MOP/COF Hybrid Aerogel: Efficient Recovery of Gold from Electronic Waste.

Extraction of gold from secondary resources such as electronic waste (e-waste) has become crucial in recent times to compensate for the gradual scarcity of the noble metal in natural mines. However, designing and synthesizing a suitable material for highly efficient gold recovery is still a great challenge. Herein, we have strategically designed rapid fabrication of an ionic crystalline hybrid aerogel by covalent threading of an amino-functionalized metal-organic polyhedra with an imine-linked chemically stable covalent organic framework at ambient condition. The hierarchically porous ultra-light aerogel featuring imine-rich backbone, high surface area, and cationic sites have shown fast removal, high uptake capacity (2349 mg/g), and excellent selectivity towards gold sequestration. Besides, the aerogel can extract ultra-trace gold-ions from different terrestrial water bodies, aiming towards safe drinking water. This study demonstrates the great potential of the composite materials based on a novel approach to designing a hybrid porous material for efficient gold recovery from complex water matrices.

Mn (III) Catalyzed Synthesis of New Chroman and Chromeno-quinoline Molecules via Trans-annulation of 4-hydroxy Coumarins Using 2-hydroxy / Amino Benzyl Alcohols

Abstract: The chemistry of heterocyclic compounds holds a significant role in modern organic and medicinal chemistry. These heterocyclic compounds serve as key structural frameworks in various biologically active compounds. Moreover, 2H-chromene derivatives with oxygen-containing heterocycles exhibit a range of pharmacological effects. 2H-chromenes serve as precursors for creating various therapeutic agents, such as anti-HIV, antidiabetic, anticancer, antihypertensive, antioxidative, and antiviral. Additionally, they are utilized in the development of antitumor, antimicrobial, fungicidal, insecticidal, and cytotoxic substances, and play a key role as intermediates in the synthesis of many natural products and pharmaceuticals. The synthesis of 2H-chromene derivatives typically involves the condensation of phenols with α, β-unsaturated carbonyl compounds, such as aldehydes or ketones. One common method is the use of pechmann condensation, where a phenolic compound reacts with a β-ketoester in the presence of an acid catalyst, leading to the formation of chromene molecule. Herein, we developed a new approach for the synthesis of novel chromene derivatives via trans-annulation of 4-hydroxy coumarins using 2-hydroxy or amino-substituted benzyl alcohols in the presence of most abundant Mn (III) catalyst. The process typically involves dual C-H alkylation followed by ring opening and annulation to access chroman or chromeno-quinoline derivatives. The mechanistic investigation was done with

A Vitamin C Fuel Cell through Substrate-Ligand Interactions

In this work, we have investigated the crucial role of ligand in non-precious organometallic complexes in influencing the de-electronation kinetics of fuel molecules through a unique substrate-ligand synergistic interaction. This unique chemistry imparts electron deficiency at the catalytic metal center while simultaneously populating the ligand with an extensive proton charge assembly. This distinct substrate-ligand interaction enhances the DLFC (Direct liquid fuel cell) performance by coulombically dragging the substrate with a distinct amplification in its de-electronation kinetics. By integrating this approach with an outer-sphere half-cell reaction, a precious metal-free vitamin C fuel cell is developed, which is capable of generating an open circuit voltage of 950 mV, a peak power density of  97 mW/cm2 at a peak current density of  215 mA/cm2 with the performance metrics nearly 1.7 times higher than a precious metal based DLFC. This work contributes to the potential of substrate-ligand synergy in designing efficient molecular catalysts for energy conversion applications.

Unveiling C-C Coupling in Redox-Active Bis(α-Iminopyridine) Tin Complexes

Our group have been interested in low-valent Sn(II) chemistry stabilized within bis(imine) based redox-active ligand systems. We have obtained a bisstannylene from the reaction between the bis(-iminopyridine) ligand and the Sn[(NSiMe3)2]2 through ene-amide transformation.Such ene-amide stabilized stannylene exhibit dipolar behavior leading to the formation of Sn(II) di-cation. The ene-amide derivative has been utilized for the stabilization of a highly nucleophilic stannylene. We have now observed C-C coupling reactions in the ene-amide stabilized polystannylene systems via radical pathway. The C-C coupling occurs at the ligand backbone of the polystannylenes leading to the formation of intensely colored compounds. The compounds have been fully characterized using single crystal X-ray diffraction techniques in the solid-state and multi-nuclear NMR spectroscopy in the solution-state. The origin of the absorbance for such polystannylenes have been rationalized from time-dependent density functional theory of their optimized geometries. We have isolated intermediates which helps to rationalize the reaction mechanism for the coupling reaction. All these studies will be discussed in the talk.

The Reactivity of Acceptor-Acceptor Diazo Pyrazolones with Allyl Thioethers under Visible Light: Access to Homoallyl Sulfides, Spiropyrazolones - Pesticide Analogues and Photoflow Synthesis

The novel reactivity of a less selective and more reactive acceptor-acceptor kind of diazo pyrazolone (DIPOL) has been explored under visible light for the first time. We have successfully demonstrated the reaction of DIPOL and different allyl thioethers under blue light to construct a wide variety of products including a pesticidal analogue exclusively in excellent chemoselectivity in good to excellent yields. Moreover, possible side products emanating from ketene were not observed. This protocol works smoothly in an environmentally benign solvent under inert free conditions. The practicality of the protocol has been extended to a photoflow reaction, and also, the reaction works smoothly under the direct exposure of sunlight.

CO2-Selective Adsorption in a Zinc-Based Ultramicroporous Framework

Ultramicroporous metal-organic frameworks (MOFs) are uniquely suited for CO2 capture due to their ability to tightly pack active functional groups within their pores, enhancing selective guest–framework interactions. MOFs with pore surfaces lined with both methyl and amine groups are especially promising for efficient CO₂ sorption under humid conditions. In this study, a zinc-triazolato-acetate layered-pillared MOF demonstrates the potential of such functionalized ultramicropores, showcasing selective CO₂ capture capabilities. These findings emphasize the role of precisely engineered pore environments in developing next-generation materials for effective and selective CO₂ adsorption in challenging conditions.

Effect of pathogenic mutations on dynamics of the mouse prion protein

Prion proteins (PrPs) are implicated in a range of neurodegenerative diseases, and understanding their dynamic behavior is crucial for unraveling the mechanisms underlying prion pathology. In this study, we use Photoinduced Electron Transfer Fluorescence Correlation Spectroscopy (PET-FCS) to investigate the dynamics of prion proteins, focusing on how pathogenic mutations influence the protein's native state. PET-FCS provides high-resolution insights into protein conformational transitions by monitoring fluorescence fluctuations and utilizing photoinduced electron transfer to track molecular interactions. By comparing the dynamics of wild-type and mutant prion proteins, we examine how specific pathogenic mutations alter the protein's conformational stability and native state dynamics. Our results show that these mutations disrupt the native conformational equilibrium, affecting protein flexibility and potentially facilitating misfolding and aggregation. These findings offer new perspectives on how genetic variations in prion proteins may contribute to disease progression and provide a deeper understanding of the relationship between protein dynamics and prion-related neurodegenerative disorders.

Phosphine Stabilized Low Valent Tetrylene

The chemistry of the stable divalent Group 14 elements, called Tetrylene, has been the subject of extensive discussion and investigation for the past several decades. Tetrylenes, being the heavier analouge of carbene, have one lone pair of electrons and one vacant p orbital, hence, they require inter/intramolecular donation to provide thermodynamic stabilization.1 There are a lot of reports on the synthetic design and reactivity of low valent Germanium ( Germylene) and Tin ( Stannylene). Here, we designed a phosphine-stabilized Germylene and Stannylene in the Acenaphthene backbone. Interestingly, the electron push from the adjacent peri-substituted Phosphorous atom to the vacant p orbital of germylene and stannylene led to different kinds of bond activations5 at the germylene center based on the donating ability of the Phosphine, rendering the oxidation of the Germanium center from +2 to +4 oxidation state. However, when we placed a Germanium (II) cation6 adjacent to the Germylene, the electron push from the phosphine and simultaneous electron pull from the Ge (II) cation stabilized the Germylene via push-pull interaction. In other work, we investigated the coordination of Gold(I) chloride with a PNNP pincer ligand provided promising results with the synthesis of a monometallic and a bimetallic complex. The monometallic complex provided an open coordination site which was further exploited for the coordination of low-valent germanium. However, that led to the formation of an unprecedented Germanium (II) Gold (I) bimetallic complex.

Peptide binder design for Gankyrin inhibition

Gankyrin is an oncogenic protein overexpressed in cancers, notably hepatocellular carcinoma, and plays a key role in cell cycle dysregulation and tumorigenesis. It exerts its effects by binding to various protein partners, including retinoblastoma protein (pRb) and HDM2, enhancing the hyperphosphorylation and degradation of pRb and promoting p53 ubiquitination. These interactions activate pathways that favor cell proliferation and suppress apoptosis, making gankyrin a significant target for cancer therapeutics. However, gankyrin's flat, concave surface presents challenges for small-molecule targeting, suggesting the potential of peptide binders as effective inhibitors. In this work, we utilized advanced diffusion models, specifically RFdiffusion, to design peptide backbones capable of binding to gankyrin’s interaction interfaces. RFdiffusion incrementally denoises input data to generate structures that resemble target distributions. We paired RFdiffusion with ProteinMPNN, a graph neural network-based tool, to obtain optimized amino acid sequences for generated peptide backbones. Predicted structures for these peptides were refined using AlphaFold2, ensuring structural consistency and biological feasibility. To evaluate binding affinity, we performed free energy calculations through metadynamics, quantifying the binding free energies of top-ranking peptides.

Ligand Isomerization Driven Electrocatalytic Ammonia Synthesis

This study investigates a novel electro-synthetic method for ammonia production directly from agricultural digestate, leveraging ligand isomerization to enhance catalytic efficiency. Conventional ammonia synthesis, typically achieved via the Haber-Bosch process, is energy-intensive and relies on fossil fuels, resulting in high carbon emissions along with high energy consumption. By contrast, this process operates under ambient conditions with a custom catalyst that undergoes ligand isomerization, achieving approximately 90% conversion efficiency and a yield of ~0.64 mg of NH₃ per hour per cm². Agricultural digestate serves as a nitrogen-rich, renewable feedstock, aligning this method with sustainable waste utilization practices and circular economy principles. The selective activation of catalytic sites ensures consistent yield while minimizing energy input, offering economic and environmental benefits suitable for decentralized applications in agricultural sectors. However, challenges remain regarding catalyst stability and scalability due to variability in digestate composition. Future work will focus on enhancing catalyst durability, optimizing operational parameters, and adapting to diverse waste inputs to ensure viable large-scale implementation. This approach offers an efficient, low-emission pathway for ammonia production, potentially transforming waste management in agriculture. In summary, this ammonia electrosynthesis method offers a promising alternative to traditional production, transforming agricultural waste into valuable resources while contributing to cleaner, circular economy models and sustainable agriculture. This innovation has the potential to revolutionize the ammonia industry, offering economic and environmental benefits on a global scale.

Attenuating the Aβ42 Aggregation and Toxicity by Designing Peptides

Shorter 10- and 12-mer peptides exhibited only minimal aggregation inhibition, while the fully hydrophobic 15-mer analogue of the ααγ-hybrid peptide showed no aggregation inhibitory activity. In contrast, the 18- and 21-mer analogues demonstrated excellent inhibition compared to the 15-mer. Additionally, ααγ-hybrid peptide demonstrated resistance to trypsin digestion and proved nontoxic to neuronal cells. Circular dichroism analysis revealed that the peptide induces a helical conformation in Aβ42 upon interaction, which is a significant departure from the typical β-sheet conformation associated with Aβ42 aggregation. With increasing the length of the peptide enhances its ability to disrupt Aβ42 aggregation while maintaining non-toxicity to cells and exhibiting non-hemolytic properties.

Visible-Light Mediated Organophotoredox Catalyzed Synthesis of Tetraketones and Its Spirocyclisation

Eosin-Y catalyzed synthesis of diverse arrays of bioactive tetraketones using cyclic-1,3-diketones and tertiary amines as alkyl synthon under 18W blue LED have been accomplished. Diverse arrays of tertiary amines first undergo reductive quenching of excited photo catalyst to form iminium ion that upon subsequent attack by cyclic-1,3-diketones give rise to tetraketones. The tetraketones were cyclised further using I2/K2CO3 to afford spirocyclic products.

Metabolomic insights into the development of hyperglycemia in murine models of type 1 and type 2 diabetes mellitus

Background: The incidence of diabetes mellitus (DM) is increasing at alarming proportions worldwide. This necessitates the need to gain deeper insights into the establishment and development of the disease. Amongst the two major forms of DM, type 1 DM (T1DM) is autoimmune and involves the death of pancreatic -cells, while type 2 DM (T2DM) is associated with the development of insulin resistance. The development of murine models for both T1DM and T2DM has helped in elucidating disease mechanisms and in assessing the efficacy of various therapeutic agents. However, a dire need exists to identify early biomarkers for the two. Metabolomics, the study of metabolites the end-products of different biochemical pathways, has emerged as a major tool for the identification of specific and early biomarkers. This study is an attempt in this direction where a relationship between the development of hyperglycemia and metabolic disturbances that occur during the development of type 1 diabetes (T1DM) and type 2 diabetes (T2DM) is being evaluated using established animal models. Methods: Male C57BL/6 mice, aged six weeks, were subjected to streptozotocin (STZ) injections (55 mg/kg) in increasing numbers (0 to 5 injections). Mice were monitored for 15- and 60-day post-injection for T1DM development. For T2DM, eight-week-old male C57BL/6 mice were fed a high-fructose/high-fat diet (HF/HFD), with assessments at 4, 8, 12, and 16 weeks. An oral glucose tolerance test (OGTT) and insulin tolerance test (ITT) were performed to confirm the development of hyperglycemia and insulin resistance. Following these assessments, NMR spectroscopy was performed on the metabolites extracted from the collected adipose tissue samples. Briefly, 1H NMR spectra were recorded using the noesygppr1d pulse program. Metabolite concentrations were calculated for each adipose tissue sample using Chenomx NMR Suite 8.1 software. The normalized metabolite concentrations were analyzed using MetaboAnalyst to determine and identify the significantly perturbed metabolites. Results: Mice receiving three or more STZ injections exhibited significant hyperglycemia at both the early and late time points, indicating that small insults were adequate for inducing diabetic conditions. In the HF/HFD cohort, a progressive increase in insulin resistance and hyperglycemia was observed from 8 weeks onwards. A total of 51 abundant and aqueous metabolites were identified in the adipose tissues, with leucine and lysine emerging as potential early biomarkers for pancreatic β-cell death in T1DM. For T2DM, metabolites such as choline, glycerophosphocholine, and valine showed promise as early biomarkers for establishing hyperglycemia and insulin resistance. The common perturbed metabolic pathways included protein biosynthesis, propanoate metabolism, and valine, leucine, and isoleucine degradation. Conclusion: The metabolic perturbations identified from this study provide insights into the pathophysiology of T1DM and T2DM and suggest specific metabolites that can be proposed as potential early biomarkers for the identification of these conditions. Further exploration of these pathways may enhance understanding of diabetes progression and provide insights for different therapeutic strategies.

Unveiling Temperature-Induced Structural Phase Transition and Luminescence in Mn2+-Doped Cs2NaBiCl6 Double Perovskite

Doping metal ions into halide double perovskites introduces intriguing optical and optoelectronic properties. However, the double perovskites undergo structural phase transitions under varying temperature and pressure, raising questions about how such transitions affect the dopant's optoelectronic behavior. Also, can the dopants alter the phase transition behavior? Here we address these questions, with the example of Mn2+-doped Cs2NaBiCl6 double perovskite.1 Both the undoped and Mn2+-doped Cs2NaBiCl6 show a similar structural phase transition below 110 K. The samples remain in cubic phase between 300-110 K, transitioning to a tetragonal phase between 100-15 K. Importantly, this phase transition of the host does not influence the photoluminescence (PL) arising from Mn2+ d-d transitions. Similarly, electron paramagnetic resonance (EPR) spectra of Mn2+ dopants remain unchanged across the phase transition temperature. Both the PL and EPR data suggest that the local structure around Mn2+ dopant remains unchanged, ensuring a stable light emission, regardless of the transition of global structure of the host. These results suggest that the global structural phase transition of the host does not to influence the local structure and emission property of the dopant Mn2+ ion. The stability of dopant emission regardless of the structural phase transition bodes well for their potential applications in phosphor converted light emitting diodes.

Click-functionalized aptamer platform to detect c-Met overexpressing cancer cells

Hepatocyte growth factor (HGF) is a natural protein that binds to its high-affinity receptor, mesenchymal-epithelial transition factor (c-Met) which then activates several downstream cellular signaling such as tissue regeneration, growth and protection. overexpression of c-Met shows cancer metastasis. A DNA aptamer trcln3 is known to bind to c-Met target-specifically and inhibit HGF-induced c-Met signaling. Our hypothesis is to conjugate the aptamer to a probe leveraging click chemistry. The modified aptamer attaches to the cell membrane by receptor binding and via receptor-mediated endocytosis internalizes the probe attached at the 3’-end of the aptamer. This modified aptamer can be used as a tool for cellular imaging as well as a targeted drug delivery platform.

Conformer-Mediated Helical Chirality in 2D Hybrid Perovskites

Two-dimensional (2D) chiral organic-inorganic hybrid lead halide perovskites combines structural asymmetry, semiconducting charge transport and strong spin-orbit coupling paving the way for unique chiral optoelectronic and spin-based properties. Typically, chiral organic sublattice induces chirality into the inorganic sublattice through non-covalent interactions at organic-inorganic interface. However, the specific mechanisms driving this chirality induction remain unclear. In a novel approach, we propose using different conformers of a chiral organic ammonium ion to create asymmetry in these non-covalent interactions, thereby tailoring the chirality of the inorganic sublattice. We prepared (R-IAP)2PbI4 and (S-IAP)2PbI4 (IAP: 1-iodopropane-2-ammonium), which crystallize in the helical enantiomorphic space groups P43212 and P41212, respectively. Structural analysis shows that the gauche- and anti-conformers of IAP are arranged alternatively in the hybrid structure. Importantly, the anti-conformer of IAP ion have significantly stronger electrostatic, hydrogen bonding, and I-I halogen bonding interactions with the inorganic [PbI4] sublattice, compared to the gauche-conformer. This periodic asymmetry in non-covalent interactions caused by the alternative arrangement of gauche- and anti-conformers, induces chirality within the inorganic sublattice lattice, marked by rare four-fold screw axes (4₃ and 4₁). The two chiral enantiomers (R-/S-IAP)2PbI4 show mirror-image like circular dichroism spectra for excitonic absorption, which originates mainly from the inorganic sublattice. This conformer-mediated approach to design chiral hybrid perovskites in helical space groups expands the materials options for advanced optoelectronics.

Effect of film morphology on circular dichroism of chiral hybrid perovskites

Chiral hybrid perovskite films combine optical chirality with semiconducting charge transport properties leading to chiral optoelectronics like circularly polarized photodetectors or LEDs. A key component for such applications is the extent of chirality in the film. Circular dichroism (CD), particularly its anisotropic factor (gCD), is typically used to measure the extent of chirality of the material. In contrast, here we show that the CD and gCD depends strongly on an extrinsic parameter, namely film morpohology. We have prepared single crystals and spin-coated films of six chiral hybrid lead halides, 2D (R- and S-MBA)2PbI4, 1D (R- and S-MBA)PbI3 and 1D (R- and S-MBA)PbBr3, where MBA = methylbenzylammonium. Four samples, 2D (R- and S-MBA)2PbI4 and 1D (R- and S-MBA)PbI3 form homogenous non-textured films, and show isotropic CD signal with reliable gCD values. But other two samples, 1D (R- and S-MBA)PbBr3 form textured films, showing uncorrelated CD signals from different parts of the same film. Therefore, our results show that the role of film morphology needs to be verified, before designing and comparing chiroptic and chiral optoelectronic properties of hybrid perovskites.

Sulfation Patterns of Fluorinated Heparan Sulfate Encode Unprecedented Molecular Recognitions and Activities

Heparan sulfate (HS) are heterogenous polysaccharide that contributes to diverse biological processes. However, the synthetic challenges, selective protein binding and stability within biological systems impede medical applications of native HS ligands. In contrast, HS mimetics have emerged as a powerful tool in drug discovery. Herein, we present the design and synthesis of the first series of HS mimetics composed of fluorine atom at the C3 position of the glucuronic acid residue, aimed at modulating structure-activity relationships. The 19F-NMR confirmed that fluorine peaks are high sensitive to the sulfation patterns and maintained the 4C1 conformation in glucuronic acid. While, the microarray analysis, followed by SPR studies confirmed a single site substitution (OH to F) in HS drastically improve the N-acetate HS sequence binding affinity towards growth factors and chemokines. To our surprise, GlcNAc6S-GlcA(3F) and GlcuNS6S3S-GlcA(3F) showed remarkable strong binding to various growth factors and chemokines similar to highly sulfate N-sulfate native HS ligands. Further, these binding also regulate growth factors mediated fibroblast cells proliferation, demonstrating the importance of F-substitution in HS to modulate its activity