Preferential Recognition Research Articles

Pathogenic relevance of antibodies against desmoglein3 inpatients with oral lichen planus.

Oral lichen planus (OLP) is a Tcell driven disorder that significantly impairs patients' quality of life. Previous reports suggest that both cellular and humoral activities against desmoglein (dsg) 1 and 3 may be involved in OLP pathogenesis. Here, we aim to analyze the frequency of occurrence and pathological significance of anti-dsg antibodies in a large cohort of OLP patients. OLP patients were screened for anti-dsg antibodies by enzyme-linked immunosorbent assay in three tertiary referral centers. OLP sera with anti-dsg antibodies were further analyzed by Western blot and dispase-based keratinocyte dissociation assay (DDA) to identify the targeted dsg ectodomains and to assess their pathogenicity. Of 151-screened individuals with OLP, only four patients (2.6%) with erosive OLP showed serum IgG against dsg1/3. Western blot analysis with recombinant dsg3 ectodomains revealed preferential recognition of the extracellular domain 5. By DDA with spontaneously immortalized human keratinocytes, none of the sera from these four patients induced acantholysis. Activation of humoral immunity occurs prevalently in patients with erosive OLP, probably due to epitope spreading. OLP serum antibodies are unable to induce loss of intercellular adhesion in vitro, strongly suggesting that they are not disease causing but rather an epiphenomenon.

Sequence Matters: Primary COVID-19 Vaccination after Infection Elicits Similar Anti-spike Antibody Levels, but Stronger Antibody Dependent Cell-mediated Cytotoxicity than Breakthrough Infection.

Infection before primary vaccination (herein termed "hybrid immunity") engenders robust humoral immunity and broad Ab-dependent cell-mediated cytotoxicity (ADCC) across SARS-CoV-2 variants. We measured and compared plasma IgG and IgA against Wuhan-Hu-1 and Omicron (B.1.1.529) full-length spike (FLS) and receptor binding domain after three mRNA vaccines encoding Wuhan-Hu-1 spike (S) and after Omicron breakthrough infection. We also measured IgG binding to Wuhan-Hu-1 and Omicron S1, Wuhan-Hu-1 S2 and Wuhan-Hu-1 and Omicron cell-based S. We compared ADCC using human embryonic lung fibroblast (MRC-5) cells expressing Wuhan-Hu-1 or Omicron S. The effect of Omicron breakthrough infection on IgG anti-Wuhan-Hu-1 and Omicron FLS avidity was also considered. Despite Omicron breakthrough infection increasing IgG and IgA against FLS and receptor binding domain to levels similar to those seen with hybrid immunity, there was no boost to ADCC. Preferential recognition of Wuhan-Hu-1 persisted following Omicron breakthrough infection, which increased IgG avidity against Wuhan-Hu-1 FLS. Despite similar total anti-FLS IgG levels following breakthrough infection, 4-fold higher plasma concentrations were required to elicit ADCC comparable to that elicited by hybrid immunity. The greater capacity for hybrid immunity to elicit ADCC was associated with a differential IgG reactivity pattern against S1, S2, and linear determinants throughout FLS. Immunity against SARS-CoV-2 following Omicron breakthrough infection manifests significantly less ADCC capacity than hybrid immunity. Thus, the sequence of antigenic exposure by infection versus vaccination and other factors such as severity of infection affect antiviral functions of humoral immunity in the absence of overt quantitative differences in the humoral response.

Enhanced binding of guanylated poly(A) RNA by the LaM domain of LARP1

ABSTRACT La-related proteins (LARPs) are a family of RNA-binding proteins that share a conserved La motif (LaM) domain. LARP1 plays a role in regulating ribosomal protein synthesis and stabilizing mRNAs and has a unique structure without an RNA binding RRM domain adjoining the LaM domain. In this study, we investigated the physical basis for LARP1 specificity for poly(A) sequences and observed an unexpected bias for sequences with single guanines. Multiple guanine substitutions did not increase the affinity, demonstrating preferential recognition of singly guanylated sequences. We also observed that the cyclic di-nucleotides in the cCAS/STING pathway, cyclic-di-GMP and 3‘,3’-cGAMP, bound with sub-micromolar affinity. Isothermal titration measurements were complemented by high-resolution crystal structures of the LARP1 LaM with six different RNA ligands, including two stereoisomers of a phosphorothioate linkage. The selectivity for singly substituted poly(A) sequences suggests LARP1 may play a role in the stabilizing effect of poly(A) tail guanylation.

Exploring galectin interactions with human milk oligosaccharides and blood group antigens identifies BGA6 as a functional galectin-4 ligand

Galectins (Gals), a family of multifunctional glycan-binding proteins, have been traditionally defined as β-galactoside binding lectins. However, certain members of this family have shown selective affinity towards specific glycan structures including human milk oligosaccharides (HMOs) and blood group antigens. In this work, we explored the affinity of human galectins (particularly Gal-1, -3, -4, -7 and -12) towards a panel of oligosaccharides including HMOs and blood group antigens using a complementary approach based on both experimental and computational techniques. While prototype Gal-1 and Gal-7 exhibited differential affinity for type I vs. type II Lac/LacNAc residues and recognized fucosylated neutral glycans, chimera-type Gal-3 showed high binding affinity towards poly-LacNAc structures including LNnH and LNnO. Notably, the tandem-repeat human Gal-12 showed preferential recognition of 3-fucosylated glycans, a unique feature among members of the galectin family. Finally, Gal-4 presented a distinctive glycan-binding activity characterized by preferential recognition of specific blood group antigens, also validated by saturation transfer difference nuclear magnetic resonance (STD-NMR) experiments. Particularly, we identified oligosaccharide blood group A type 6 (BGA6) as a biologically relevant Gal-4 ligand, which specifically inhibited IL-6 secretion induced by this lectin on human peripheral blood mononuclear cells. These findings highlight unique determinants underlying specific recognition of HMOs and blood group antigens by human galectins, emphasizing the biological relevance of Gal-4-BGA6 interactions, with critical implications in the development and regulation of inflammatory responses.

Temperature sensitivity of bat antibodies links metabolic state of bats with antigen-recognition diversity

The bat immune system features multiple unique properties such as dampened inflammatory responses and increased tissue protection, explaining their long lifespan and tolerance to viral infections. Here, we demonstrated that body temperature fluctuations corresponding to different physiological states in bats exert a large impact on their antibody repertoires. At elevated temperatures typical for flight, IgG from the bat species Myotis myotis and Nyctalus noctula show elevated antigen binding strength and diversity, recognizing both pathogen-derived antigens and autoantigens. The opposite is observed at temperatures reflecting inactive physiological states. IgG antibodies of human and other mammals, or antibodies of birds do not appear to behave in a similar way. Importantly, diversification of bat antibody specificities results in preferential recognition of damaged endothelial and epithelial cells, indicating an anti-inflammatory function. The temperature-sensitivity of bat antibodies is mediated by the variable regions of immunoglobulin molecules. Additionally, we uncover specific molecular features of bat IgG, such as low thermodynamic stability and implication of hydrophobic interactions in antigen binding as well as high prevalence of polyreactivity. Overall, our results extend the understanding of bat tolerance to disease and inflammation and highlight the link between metabolism and immunity.

Molecular recognition on the surface of concentrated hydrochloric acid: Hydration configuration-driven preferential recognition of Rh (III) anions with inner-coordinated water molecules

Comprehension of selective recognition of anions is confined to a phenomenological list of solvents, hardly surpassing Pedersen’s empirical observations of cationic-crown ether binding. In this work, a novel strategy employing thin-layer oil membrane extraction (TOMX) on the surface of concentrated hydrochloric acid is proposed for controllable recognition and separation of anions with different hydration configurations. Four typical chloric-complexing anions, RhCl63−, PdCl42−, PtCl62− and FeCl4−, usually coexisting in the concentrated hydrochloric acid leaching solutions of precious metal concentrates were focused. A surprising phenomenon was noticed that the octahedral RhCl5(H2O)2− anions with inner-coordinated water molecules were preferentially recognized by 18C6 macrocyclic molecule. However, the planar quadrilateral Pd (II) chloric-complexing anions with a hydration configuration via water molecules attacking the central Pd (II) atoms along the Z-axis direction can be separated subsequently. The Pt (IV) and Fe (III) chloric-complexing anions respectively with an octahedral and tetrahedral outer-coordinated hydration shell configuration were the last to be recognized. Such an order in extracting Rh (III) > Pd (II) > Pt (IV) > Fe (III) anions depends on their hydration capacity and the preferential affinity towards the interface, which is almost impossible during the conventional stirring and oil droplet dispersed extraction. Because of a lower concentration of dissociated hydrogen ions on the surface of concentrated hydrochloric acid compared to its bulk concentrations, the hydration of those chloric-complexing anions was enhanced. The Rh (III) anions with inner-coordinated water molecules exhibit a higher interfacial affinity than other anions. The water molecules entering the inner coordination layer of Rh (III) chloric-complexing anions, cooperating with its outer-coordinated hydration shell, act as a hydrogen bond “water bridge” to interact with 18C6 molecules, which makes it easier to feel the influence from the aqueous laminar shear flow under the thin-layer oil membrane, thereby driving the preferential recognition of easily hydrated Rh (III) anions at the interface. The controllable “water bridge” interactions driven by shear flow can be activated or deactivated on the surface of concentrated hydrochloric acid by adjusting the shear flow rate. This work lays a foundation for the future development of a controllable flexible molecular recognition technology at liquid–liquid interfaces.

A simple and low cost thiadiazole-based receptor as a multi-ion optical chemosensor for Cu2+, Hg2+ and CN‾ in water

The chemosensing ability of a low-cost commercially available thiadiazole-based receptor (TAZ-1) was explored. In an aqueous solution, the receptor TAZ-1 showed exceptional selectivity and sensitivity towards Cu2+ and Hg2+ over twenty-two metal cations (Ag+, Al3+, Ba2+, Ca2+, Cd2+, Co2+, Cr3+, Cs+, Cu2+, Fe2+, Fe3+, Hg2+, K+, Li+, Mg2+, Mn2+, Na+, Ni2+, Pb2+, Sr2+, Zn2+ and Zr3+). TAZ-1 also has a preferential recognition ability for CN‾ over fifteen anions (AcO‾, Br‾, Cl‾, ClO4‾, CN‾, CO32‾, F‾, H2PO4‾, HCO3‾, HSO4‾, I‾, NO2‾, NO3‾, SO32‾ and SO42‾). For Cu2+, Hg2+ and CN‾ ions, the limit of detection (LOD) based on 3 × δblank/k was 0.58 μM, 0.15 μM and 0.25 μM respectively.

N4BP1 functions as a dimerization-dependent linear ubiquitin reader which regulates TNF signalling

Signalling through TNFR1 modulates proinflammatory gene transcription and programmed cell death, and its impairment causes autoimmune diseases and cancer. NEDD4-binding protein 1 (N4BP1) is a critical suppressor of proinflammatory cytokine production that acts as a regulator of innate immune signalling and inflammation. However, our current understanding about the molecular properties that enable N4BP1 to exert its suppressive potential remain limited. Here, we show that N4BP1 is a novel linear ubiquitin reader that negatively regulates NFκB signalling by its unique dimerization-dependent ubiquitin-binding module that we named LUBIN. Dimeric N4BP1 strategically positions two non-selective ubiquitin-binding domains to ensure preferential recognition of linear ubiquitin. Under proinflammatory conditions, N4BP1 is recruited to the nascent TNFR1 signalling complex, where it regulates duration of proinflammatory signalling in LUBIN-dependent manner. N4BP1 deficiency accelerates TNFα-induced cell death by increasing complex II assembly. Under proapoptotic conditions, caspase-8 mediates proteolytic processing of N4BP1, resulting in rapid degradation of N4BP1 by the 26 S proteasome, and acceleration of apoptosis. In summary, our findings demonstrate that N4BP1 dimerization creates a novel type of ubiquitin reader that selectively recognises linear ubiquitin which enables the timely and coordinated regulation of TNFR1-mediated inflammation and cell death.

Abstract 2738: XON7, a new Glyco-Humanized Polyclonal Antibody, first in class immunotherapy against several solid tumors

Abstract Introduction: Cancer immunotherapy has recently generated much excitement after the success of the immunomodulating anti-CTLA-4 and anti-PD-1 antibodies against various types of cancers. However, for many cancers, there is still a lack of effective treatment that can result in long-term cancer-free survival and lower metastatic and relapse risks. The emergence of cancer resistance could be minimized by drug combination or by multi-targeting of tumor cells. Polyclonal antibodies can target several tumor-associated antigens simultaneously and would be more efficient than a conventional mAbs. Here we evaluate the safety and efficacy of XON7, a first in class glyco-humanized polyclonal antibody (GH-pAb), in cancer preclinical models. Material and Methods: XON7 ability to induce Complement Dependent Cytotoxicity (CDC) and apoptosis was tested in a panel of cancer cell lines and PBMC. XON7 was also evaluated in sphere formation assay to predict its effects on cancer resistant. Specific binding to human tumors and healthy tissues was assessed by immunochemistry on tissue micro-array. Cross-cancer activity was evaluated on biopsies from patients with solid tumor such as CRC, NSCLC, osteosarcoma, and breast cancers. In vivo XON7 efficacy was evaluated in NMRI nude mice using A549: NSCLC, HCT-116: colon cancer, LNCaP: prostate cancer and MDA-MB-231: breast cancer cells. A human NSCLC chorio-allantoic membrane (CAM) model was used to evaluate the efficacy of XON7 + anti PD-1 on tumor growth and metastasis. Pharmacokinetics and safety of this drug were assessed in marmoset after single and repeated IV dosing up to 60mg/kg. Results: XON7 showed a potent in vitro antitumor activity in a panel of cancer cell lines, it induced specific tumor cell CDC (EC50=50ug/mL) and apoptosis (IC50= 100ug/mL). it was able to kill up to 100% of the cancer cells without affecting PBMC. In addition, it induced a striking decrease of tumor sphere formation in HCT116, A549 and MDA-MB-231 cancer cell lines. XON7 showed preferential recognition of tumor cells as compared to normal cells, it demonstrated cross-reaction to tumor patient biopsy without staining of the healthy tissues. In vitro XON7 potency was translated into in vivo efficacy in different mice xenograft models. XON7 induced a significant reduction of tumor growth ranging from 40 to 90% across several tested tumors. Furthermore, it showed, significant increase of anti-tumor response rate and decrease of metastasis when it is associated with anti PD-1 in vivo CAM model (>90%, p=0.001). XON7 was also characterized by high tolerance and satisfactory exposure in marmoset. Conclusion: Based on its safe toxicity profile and potent activity, XON7 appeared as a novel and promising cancer immunotherapy to fight against recurrent solid tumor, it is now aimed to reach clinical development, FIH in patients is planned to start before the end of 2023. Citation Format: Carine Ciron, Gwenaelle Evanno, Pierre Morice, Pierre-Joseph Royer, Françoise Shneiker, Odile Duvaux, Bernard Vanhove, Firas Bassissi. XON7, a new Glyco-Humanized Polyclonal Antibody, first in class immunotherapy against several solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2738.

Autoreactive T cells target peripheral nerves in Guillain–Barré syndrome

Guillain–Barré syndrome (GBS) is a rare heterogenous disorder of the peripheral nervous system, which is usually triggered by a preceding infection, and causes a potentially life-threatening progressive muscle weakness1. Although GBS is considered an autoimmune disease, the mechanisms that underlie its distinct clinical subtypes remain largely unknown. Here, by combining in vitro T cell screening, single-cell RNA sequencing and T cell receptor (TCR) sequencing, we identify autoreactive memory CD4+ cells, that show a cytotoxic T helper 1 (TH1)-like phenotype, and rare CD8+ T cells that target myelin antigens of the peripheral nerves in patients with the demyelinating disease variant. We characterized more than 1,000 autoreactive single T cell clones, which revealed a polyclonal TCR repertoire, short CDR3β lengths, preferential HLA-DR restrictions and recognition of immunodominant epitopes. We found that autoreactive TCRβ clonotypes were expanded in the blood of the same patient at distinct disease stages and, notably, that they were shared in the blood and the cerebrospinal fluid across different patients with GBS, but not in control individuals. Finally, we identified myelin-reactive T cells in the nerve biopsy from one patient, which indicates that these cells contribute directly to disease pathophysiology. Collectively, our data provide clear evidence of autoreactive T cell immunity in a subset of patients with GBS, and open new perspectives in the field of inflammatory peripheral neuropathies, with potential impact for biomedical applications.

Molecular Recognition of Aromatics in Spherical Nanocages.

In general, due to the lack of efficient specific molecular interactions, achieving host-guest molecular recognition inside large and neutral metal organic cages (MOCs) is challenging. Preferential molecular recognition of aromatics using the internal binding sites of interlocked icosahedral (i.e., spherical) M12L8MOCs within poly-[n]-catenane (1) is reported. The guest absorption has been monitored directly in the solid-state by consecutive single-crystal-to-single-crystal (SCSC) reactions in a gas-solid environment, using single-crystal X-ray diffraction (SC-XRD) experiments. The preferential guest uptake is corroborated by Density Functional Theory (DFT) calculations by determining the host-guest interaction energy (Ehost-guest) with the nitrobenzene (NB) >> p-xylene (p-xy) >> o-dichlorobenzene (o-DCB) trend (i.e., from 44 kcal/mol to 25 kcal/mol), assessing the XRD outcomes. Combining SC-XRD, DFT and solid-state 13C NMR, the exceptional stability of the M12L8 cages, together with the guest exchange/release properties are rationalized by the presence of mechanical bonds (efficient π-π interactions) and by the pyridine's rotor-like behaviour (with 3 kcal/mol rotational energy barrier). The structure-function properties of M12L8 makes 1 a potential candidate in the field of molecular sensors.

Structural insight into H4K20 methylation on H2A.Z-nucleosome by SUV420H1

DNA replication ensures the accurate transmission of genetic information during the cell cycle. Histone variant H2A.Z is crucial for early replication origins licensing and activation in which SUV420H1 preferentially recognizes H2A.Z-nucleosome and deposits H4 lysine 20 dimethylation (H4K20me2) on replication origins. Here, we report the cryo-EM structures of SUV420H1 bound to H2A.Z-nucleosome or H2A-nucleosome and demonstrate that SUV420H1 directly interacts with H4 N-terminal tail, the DNA, and the acidic patch in the nucleosome. The H4 (1-24) forms a lasso-shaped structure that stabilizes the SUV420H1-nucleosome complex and precisely projects the H4K20 residue into the SUV420H1 catalytic center. Invitro and invivo analyses reveal a crucial role of the SUV420H1 KR loop (residues 214-223), which lies close to the H2A.Z-specific residues D97/S98, in H2A.Z-nucleosome preferential recognition. Together, our findings elucidate how SUV420H1 recognizes nucleosomes to ensure site-specific H4K20me2 modification and provide insights into how SUV420H1 preferentially recognizes H2A.Z nucleosome.

Selective removal of sulfamethoxazole by a novel double Z-scheme photocatalyst: Preferential recognition and degradation mechanism

Sulfamethoxazole (SMX) is a significant environmental concern due to its adverse effects and ecological risks. SMX elimination in aquatic environments via photocatalysis presents a viable solution, given its high oxidation potential. However, such a solution remains controversial, primarily due to a lack of selectivity. Here we introduce a molecularly imprinted TiO2@Fe2O3@g-C3N4 (MFTC) photocatalyst designed for the selective degradation of SMX. To assess MFTC's selectivity, we applied it to degrade synthetic wastewater containing SMX alongside interfering species sulfadiazine (SDZ), ibuprofen (IBU), and bisphenol A (BPA). The results demonstrated a selective degradation efficiency rate of 96.8%, nearly twice that of competing pollutants. The molecularly imprinted sites within the catalyst played a crucial role by selectively capturing SMX and enhancing its adsorption, thereby improving catalytic efficiency. The degradation process involved •OH and •O2− free radicals, with a newly proposed double Z-scheme mechanism and potential pathway for SMX degradation by the MFTC photocatalytic system. This study enriches the application of photocatalysis using molecularly imprinted nanocomposite materials for treating complex pollutant mixtures in water.

Computational studies on glycosaminoglycan recognition of sialyl transferases.

Despite decades of research, glycosaminoglycans (GAGs) have not been known to interact with sialyl transferases (STs). Using our in-house combinatorial virtual library screening (CVLS) technology, we studied seven human isoforms, including ST6GAL1, ST6GAL2, ST3GAL1, ST3GAL3, ST3GAL4, ST3GAL5, and ST3GAL6, and predicted that GAGs, especially heparan sulfate (HS), are likely to differentially bind to STs. Exhaustive CVLS and molecular dynamics studies suggested that the common hexasaccharide sequence of HS preferentially recognized ST6GAL1 in a site overlapping the binding site of the donor substrate CMP-Sia. Interestingly, CVLS did not ascribe any special role for the rare 3-O-sulfate modification of HS in ST6GAL1 recognition. The computational predictions were tested using spectrofluorimetric studies, which confirmed preferential recognition of HS over other GAGs. A classic chain length-dependent binding of GAGs to ST6GAL1 was observed with polymeric HS displaying a tight affinity of ~65nM. Biophysical studies also confirmed a direct competition between CMP-Sia and an HS oligosaccharide and CS polysaccharide for binding to ST6GAL1. Overall, our novel observation that GAGs bind to ST6GAL1 with high affinity and compete with the donor substrate is likely to be important because modulation of sialylation of glycan substrates on cells has considerable physiological/pathological consequences. Our work also brings forth the possibility of developing GAG-based chemical probes of ST6GAL1.

Peptide microarray-based identification of dormancy-associated Mycobacterium tuberculosis antigens inducing immune responses among latent tuberculosis infection individuals in Thailand

Multi-stage tuberculosis (TB) vaccines composed of active- and dormancy-associated antigens are promising to trigger the immune protection against all TB stages. However, scientists are still in quest of the suitable vaccine candidates. In this study, we identified the potential targets for this vaccine in a high TB burden country, Thailand. Peptide microarray was applied to gauge IgA and IgG antibodies specific to 16,730 linear epitopes of 52 dormancy-associated Mycobacterium tuberculosis (M. tb) proteins in three study groups: active tuberculosis (ATB), latent tuberculosis infection (LTBI) and endemic healthy control (EHC). Preferential IgA recognition against epitopes of dormancy-associated proteins was identified in LTBI group. Validation of these findings revealed that LTBI subjects exhibited the greater levels of Rv2659c- and Rv1738-specific IgA than those of household contacts, but less than did ATB subjects. Frequencies of IFNγ-producing CD4+ and CD8+ T cells induced by proteins Rv2659c and Rv1738 were higher in LTBI than ATB individuals. The results indicated that LTBI group in a high TB burden country demonstrated cell-mediated immune response to proteins Rv2659c and Rv1738 stronger than those of ATB. These immune responses likely contribute to natural protection against dormant M. tb and might be potential targets for a multi-stage TB vaccine.

Oxygen modulates iron homeostasis by switching iron sensing of NCOA4

To ensure proper utilization of iron and avoid its toxicity, cells are equipped with iron-sensing proteins to maintain cellular iron homeostasis. We showed previously that nuclear receptor coactivator 4 (NCOA4), a ferritin-specific autophagy adapter, intricately regulates the fate of ferritin; upon binding to Fe3+, NCOA4 forms insoluble condensates and regulates ferritin autophagy in iron-replete conditions. Here, we demonstrate an additional iron-sensing mechanism of NCOA4. Our results indicate that the insertion of an iron-sulfur (Fe-S) cluster enables preferential recognition of NCOA4 by the HERC2 (HECT and RLD domain containing E3 ubiquitin protein ligase 2) ubiquitin ligase in iron-replete conditions, resulting in degradation by the proteasome and subsequent inhibition of ferritinophagy. We also found that both condensation and ubiquitin-mediated degradation of NCOA4 can occur in the same cell, and the cellular oxygen tension determines the selection of these pathways. Fe-S cluster-mediated degradation of NCOA4 is enhanced under hypoxia, whereas NCOA4 forms condensates and degrades ferritin at higher oxygen levels. Considering the involvement of iron in oxygen handling, our findings demonstrate that the NCOA4-ferritin axis is another layer of cellular iron regulation in response to oxygen levels.

Students with Special Needs Online Learning Experiences during the COVID-19 Pandemic at the University of Ghana

Since the upsurge of online learning in higher educational institutions due to the COVID-19 pandemic, it is imperative to explore students’ active involvement, their challenges encountered, and how these challenges were resolved in the online environment. Using semi-structured interviews, we thus explored the online experiences of 17 Students With Special Needs (SWSNs) at the University of Ghana during the Covid-19 pandemic. Findings show that all participants were actively involved in online learning during the pandemic as they participated in scheduled online lectures and were self-directed in their learning. However, there were challenges met that include an uncustomised LMS platform, a struggle to meet online task deadlines and a lack of relevant digital skills. The lecturers’ collaboration and negotiation with SWSNs curtailed some of the challenges for the visually impaired as resource persons were asked to convert reading materials into braille for them. In addition, SWSNs had preferential treatment and recognition by lecturers to fully benefit from the online learning environment. The study recommends the provision of well-trained online technical support staff at the university to assist SWSNs and introduce a blended learning model to address these challenges. Such a step will lead to a positive experience of blended learning and inclusive education for all students, consequently, giving rise to a successful online learning environment.

Preferential molecular recognition of heterochiral guests within a cyclophane receptor

The discrimination of enantiomers by natural receptors is a well-established phenomenon. In contrast the number of synthetic receptors with the capability for enantioselective molecular recognition of chiral substrates is scarce and for chiral cyclophanes indicative for a preferential binding of homochiral guests. Here we introduce a cyclophane composed of two homochiral core-twisted perylene bisimide (PBI) units connected by p-xylylene spacers and demonstrate its preference for the complexation of [5]helicene of opposite helicity compared to the PBI units of the host. The pronounced enantio-differentiation of this molecular receptor for heterochiral guests can be utilized for the enrichment of the P-PBI-M-helicene-P-PBI epimeric bimolecular complex. Our experimental results are supported by DFT calculations, which reveal that the sterically demanding bay substituents attached to the PBI chromophores disturb the helical shape match of the perylene core and homochiral substrates and thereby enforce the formation of syndiotactic host-guest complex structures. Hence, the most efficient substrate binding is observed for those aromatic guests, e. g. perylene, [4]helicene, phenanthrene and biphenyl, that can easily adapt in non-planar axially chiral conformations due to their inherent conformational flexibility. In all cases the induced chirality for the guest is opposed to those of the embedding PBI units, leading to heterochiral host-guest structures.

Development of a Eudragit-Chitosan Nanosystem for the pH-Dependent Transport of Duloxetine to the Brain: Synthesis, Characterization and In Silico Modeling Analysis

The purpose of this study was to synthesize duloxetine (DLX)- loaded Eudragit-Chitosan (Eud-CHT) nanoparticles enclosed in an oral gelatin capsule and to evaluate the potential to transport DLX to the blood-brain barrier (BBB)for improved neuro-availability. The utilization of Eudragit® with chitosan offers a pH-dependent controlled drug release. The physicochemical properties of the formulated DLX-loaded Eud-CHT nanosystem were confirmed using various characterization techniques. SEM confirmed the nanoparticle morphology and pore size distribution. The particle size was 100 ± 73,41 nm, with a polydispersity index (PDI) of 0,283 and zeta potential of 16±2,79 mV. Drug entrapment efficacy (DEE) of 72% was attained, and molecular modelling predicted an efficient and controllable drug delivery system. The release of DLX from the nanosystem was evaluated at pH1.2, pH 6.8 and pH 7.4. At a pH of 6.8, 40 % of DLX was released, with only 20 % at pH 1.2 and 35% at pH 7.4. This demonstrated DLX's pH-dependent release and the Eud-CHT nanosystem's shielding effect at gastric pH. In addition, HEK 293 neural cells confirmed the non-toxicity of the DLX-Eud-CHT nanosystem. In silico modelling revealed a DLX-Eud-CHT composite with an outer cationic surface attributable to the EUD moieties on nanoparticles for preferential cell recognition and uptake at the anionic cell interface. The combined trials and results from the synthesis of DLX-Eud-CHT nanoparticles showed that these nanoparticles could be utilized as a potentially invaluable formulation for oral drug delivery of duloxetine with improved neuro-availability.

Human telomeric G-quadruplex DNA enabled preferential recognition of copper (II) and Iron (III) ions sensed by a red emissive probe

Metal ions regulate several cellular processes in humans and other life forms and their balance in the body is essential for a healthy life. Specific detection of metal ions is important from both physiological and environmental perspectives. We report here the discovery of human telomeric G-quadruplex DNA enabled selective recognition of Cu2+ and Fe3+ ions using a molecular rotor that displays emission in the red region of the spectrum. This probe selectively senses Cu2+ and Fe3+ ions among a pool of other metal cations (monovalent, divalent, trivalent) and its sensing efficiency is maintained even at nanomolar levels of the DNA-probe complex. Circular dichroism and UV–visible spectroscopy-based studies revealed that the metal recognition abilities are linked to selective interaction of compound 1 with the human telomeric G-quadruplex DNA and its subsequent displacement upon binding of certain metal ions. The probe also shows robust sensing performance in the presence of other metal ions. Between Cu2+ and Fe3+, the recognition of Cu2+ is more sensitive with 3 ppb limit of detection.