A novel HBc-S230 protein chimeric VLPs induced robust immune responses against SARS-CoV-2.

Here, we report that four functional fragments of the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) spike protein including receptor binding motif (RBM), fusion peptide (FP), heptad repeat 1 (HR1) and heptad repeat 2 (HR2) were chosen to develop a recombinant S subunit protein vaccine. This recombinant protein consisting of S230 amino acids (aa) (S230) bound specifically to the antibody from COVID-19-patients serum, which showed very strong antigenicity. The S230 was then engineered to present on the surface of Hepatitis B core (HBc) virus-like particles (VLPs) to develop HBc-S230 chimeric VLPs vaccine. Both vaccines induced strong humoral and cellular immune responses in mice, however, HBc-S230 chimeric VLPs elicited significantly higher immunogenicity than the S230. HBc-S230 chimeric VLPs promoted to generate not only dramatically higher levels of S230-specific serum antibodies, but also marked higher CD4+/CD8 + T cells ratio and substantially higher yields of IFN-γ and IL-6. Furthermore, HBc-S230 chimeric VLPs induced serum antibodies that could effectively neutralize the infection with three SARS-CoV-2 pseudoviruses (Wild type, Delta and Omicron). Our results demonstrated that HBc-S230 chimeric VLPs immunization conveyed the humoral immunity, which lasted longer than six months. Clearly, HBc-S230 chimeric VLPs enhanced immunogenicity of the S230, which could provide potent and durable protection against SARS-CoV-2 infection, indicating that HBc-S230 chimeric VLPs possessed great potential for developing highly immunogenic vaccines against SARS-CoV-2.

Thiol-containing hyperbranched polysiloxane for scavenging reactive oxygen species.

Unconventional luminescent polymers have attracted considerable attention in the biological field due to their intrinsic fluorescence properties and excellent biocompatibility. However, exploring the luminescent properties of thiol-containing polymers and the mechanism of their scavenging of ROS remains unclear. In this work, we synthesised three kinds of hyperbranched polysiloxanes (HE, HP, and HB) with terminal thiol groups containing different chain lengths by the polycondensation reaction. Surprisingly, HP exhibits longer-wavelength emission at 480 nm with a quantum yield of 12.23% compared to HE and HB. Experiments and density functional theory (DFT) calculations have revealed that the rigidity of the conformation is enhanced by substantial hydrogen bonds and through-space O⋯O interactions in the polymer structure. These interactions, combined with the rigid carbon chains, balance the flexibility of the Si-O-C chain segments, which emerges as a critical factor contributing to the superior fluorescence performance of HP. In addition, HP exhibits excellent biocompatibility and ROS scavenging ability with a scavenging capacity of up to 35.095%. This work provides a new fluorescent polymer for scavenging ROS for the treatment of ROS-related diseases.

Achieving Controllable Thermochromic Fluorescence via Synergistic Intramolecular Charge Transfer and Molecular Packing.

Thermochromic fluorescent materials (TFMs) have attracted significant attention due to their unique fluorescent colorimetric response to temperature. However, existing TFMs still suffer from weak stimulus responsiveness, broad temperature response ranges, uncontrollable emission color changes, and low quantum yields. In this study, we address these issues by designing and synthesizing three diketone-boron complexes with distinct emission wavelengths (NWPU-(2-4)). Utilizing a molecular engineering strategy to manipulate intramolecular charge transfer transitions and molecular packing modes, our synthesized complexes exhibit efficient fluorescence emission in both solution and solid states. Moreover, their emission wavelengths are highly sensitive to environmental polarity. By incorporating these compounds into thermosensitive matrices of long-chain alkanes, we produced TFMs with varied fluorescence emission peak variation ranges. Notably, the TFM based on NWPU-4, owing to its strong charge transfer transitions and dense J-aggregate packing configuration, not only exhibits intense fluorescence emission spanning the deep red to near-infrared spectrum but also displays a remarkable 90 nm broad range of thermochromic properties. Ultimately, it was successfully applied to programmable, thermally controlled, multi-level information encryption.

Recent Advances of Organic-Inorganic Hybrid Fluorescent Hyperbranched Polymer: Synthesis, Performance Regulation Strategies and Applications.

The organic-inorganic hybrid fluorescent hyperbranched polymer, including hyperbranched polysiloxane and hyperbranched polyborate, have attracted much attention due to their excellent optical properties and wide range of applications. Hyperbranched polysiloxane and polyborates, prepared by introducing Si or B elements into organic polymer chains at the molecular level through rational molecular design and novel synthesis methods, exhibit outstanding photophysical properties as an indispensable branch of organic-inorganic hybrid fluorescent materials. Herein, this review highlights the recent research progress on hyperbranched polysiloxanes and hyperbranched polyborates, including strategies for regulating their emission wavelengths, quantum yields, and fluorescence lifetimes, potential emission mechanisms, and various applications. Finally, some challenges and promising future directions in the field of organic-inorganic hybrid fluorescent polymers are summarized.

Unconventional Luminescence Polymer with Color-Tunability based on Solvent-Induced Electrostatic Potential Distribution of Fluorophore.

Tuning full-color emission of polymers holds significant promise. However, preparing unconventional luminescence polymers with color-tunability in dilute solution and understanding the relationship between non-covalent interactions and luminescent behavior remains a great challenge. We report two emitters (P1 and P2) incorporating tetracoordinate boron. The P1 with non-conjugated D-π-A structure, exhibited red delayed fluorescence at 645 nm with quantum yield of 9.15 % in aggregates. Notably, the emission wavelength of P1 can be tuned from 418 to 588 nm at different solvent. Similarly, the emission wavelength of P2 can also be adjusted by manipulating the interactions between the solvent and fluorophore. Experimental characterization and theoretical calculations indicate that the B←N bond and electronic interactions between solvent and fluorophore significantly regulate the equilibrium the electrostatic potential (ESP) and the intramolecular O⋅⋅⋅O interactions of P1, thereby modulating its emission wavelength. Additionally, these polymers showed excellent potential in fluoride ions detection. This work provides new insights into the complex effects of intermolecular interactions on luminescent properties.

Regulation of Photophysical Behaviors in Hyperbranched Aggregation-Induced Emission Polymers for Reactive Oxygen Species Scavenging.

Developing nonconjugated materials with large Stokes shifts is highly desired. In this work, three kinds of hyperbranched aggregation-induced emission (AIE) polymers with tunable n/π electronic effects were synthesized. HBPSi-CBD contains alkenyl groups in the backbone and possesses a promoted n-π* transition and red-shifted emission wavelength with a large Stokes shift of 186 nm. Experiments and theoretical simulations confirmed that the planar π electrons in the backbone are responsible for the red-shifted emission due to the strong through-space n···π interactions and restricted backbone motions. Additionally, the designed HBPSi-CBD could be utilized as an ROS scavenger after coupling with l-methionine. The HBPSi-Met exhibits remarkable ROS scavenging properties with a scavenging capacity of 77%. This work not only gains further insight into the structure-property relationship of nonconjugated hyperbranched AIE polymers but also provides a promising ROS-scavenging biomaterial for the treatment of ROS-related diseases.

Modulation of Deep-Red to Near-Infrared Room-Temperature Charge-Transfer Phosphorescence of Crystalline "Pyrene Box" Cages by Coupled Ion/Guest Structural Self-Assembly.

Organic cocrystals obtained from multicomponent self-assembly have garnered considerable attention due to their distinct phosphorescence properties and broad applications. Yet, there have been limited reports on cocrystal systems that showcase efficient deep-red to near-infrared (NIR) charge-transfer (CT) phosphorescence. Furthermore, effective strategies to modulate the emission pathways of both fluorescence and phosphorescence remain underexplored. In this work, we dedicated our work to four distinct self-assembled cocrystals called "pyrene box" cages using 1,3,6,8-pyrenetetrasulfonate anions (PTS4-), 4-iodoaniline (1), guanidinium (G+), diaminoguanidinium (A2G+), and hydrated K+ countercations. The binding of such cations to PTS4- platforms adaptively modulates their supramolecular stacking self-assembly with guest molecules 1, allowing to steer the fluorescence and phosphorescence pathways. Notably, the confinement of guest molecule 1 within "pyrene box" PTSK{1} and PTSG{1} cages leads to an efficient deep-red to NIR CT phosphorescence emission. The addition of fuming gases like triethylamine and HCl allows reversible pH modulations of guest binding, which in turn induce a reversible transition of the "pyrene box" cage between fluorescence and phosphorescence states. This capability was further illustrated through a proof-of-concept demonstration in shrimp freshness detection. Our findings not only lay a foundation for future supramolecular designs leveraging weak intermolecular host-guest interactions to engineer excited states in interacting chromophores but also broaden the prospective applications of room-temperature phosphorescence materials in food safety detection.

Hyperbranched Dynamic Crosslinking Networks Enable Degradable, Reconfigurable, and Multifunctional Epoxy Vitrimer.

Degradation and reprocessing of thermoset polymers have long been intractable challenges to meet a sustainable future. Star strategies via dynamic cross-linking hydrogen bonds and/or covalent bonds can afford reprocessable thermosets, but often at the cost of properties or even their functions. Herein, a simple strategy coined as hyperbranched dynamic crosslinking networks (HDCNs) toward in-practice engineering a petroleum-based epoxy thermoset into degradable, reconfigurable, and multifunctional vitrimer is provided. The special characteristics of HDCNs involve spatially topological crosslinks for solvent adaption and multi-dynamic linkages for reversible behaviors. The resulting vitrimer displays mild room-temperature degradation to dimethylacetamide and can realize the cycling of carbon fiber and epoxy powder from composite. Besides, they have supra toughness and high flexural modulus, high transparency as well as fire-retardancy surpassing their original thermoset. Notably, it is noted in a chance-following that ethanol molecule can induce the reconstruction of vitrimer network by ester-exchange, converting a stiff vitrimer into elastomeric feature, and such material records an ultrahigh modulus (5.45 GPa) at -150 °C for their ultralow-temperature condition uses. This is shaping up to be a potentially sustainable advanced material to address the post-consumer thermoset waste, and also provide a newly crosslinked mode for the designs of high-performance polymer.

An ultra-sensitive ratiometric fluorescent thermometer based on monomer and excimer dual emission.

By leveraging natural saturated fatty acids with distinct melting points and swift reversible phase transitions, we correlated external thermal cues to monomer and excimer emissions of difluoroboron ß-diketonate fluorophores. This integration yielded a ratiometric fluorescent thermometer showcasing unparalleled sensitivity and thermochromism in the physiological temperature range.

Hyperbranched Polyborosiloxanes: Non-traditional Luminescent Polymers with Red Delayed Fluorescence.

Non-traditional fluorescent polymers have attracted significant attention for their excellent biocompatibility and diverse applications. However, designing and preparing non-traditional fluorescent polymers that simultaneously possess long emission wavelengths and long fluorescence lifetime remains challenging. In this study, a series of novel hyperbranched polyborosiloxanes (P1-P4) were synthesized. As the electron density increases on the monomer diol, the optimal emission wavelengths of the P1-P4 polymers gradually red-shift to 510, 570, 575, and 640 nm, respectively. In particular, P4 not only exhibits red emission but also demonstrates delayed fluorescence with a lifetime of 9.73 µs and the lowest critical cluster concentration (1.76 mg/mL). The experimental results and theoretical calculations revealed that the synergistic effect of dual heteroatom-induced electron delocalization and through-space O⋅⋅⋅O and O⋅⋅⋅N interaction was the key factor contributing to the red-light emission with delayed fluorescence. Additionally, these polymers showed excellent potential in dual-information encryption. This study provides a universal design strategy for the development of unconventional fluorescent polymers with both delayed fluorescence and long-wavelength emission.

Tuning the Emission of a Nonconventional Aggregation-Induced Emission Polymer via Silicon-Bridged Twisted Intramolecular Charge Transfer for Targeted Delivery and Visualized Drug Release.

The design of tunable luminescent biomaterials with large Stokes shifts is usually pursued by a twisted intramolecular charge transfer (TICT) effect with switchable emission colors in response to various external stimuli. However, such a strategy is usually realized in conjugated molecules containing benzene or its derivatives and consequently suffers from poor biocompatibility. In this work, a hyperbranched polysiloxane (HBPSi)-based non-conjugated fluorescent polymer with TICT and aggregation-induced emission (AIE) features is developed, and its luminescent properties, fluorescence mechanism, and potential applications are investigated. Initially, the non-conjugated HBPSi exhibits remarkable AIE characteristics due to the formation of through-space conjugation. With the introduction of the sulfur atom, a non-conjugated D-A type AIE material, HBPSi-Cys, that exhibits a dual-state emission with a large Stokes shift of 213 nm, is obtained. The correlation of the lower-energy emission band with solvent polarity suggests the existence of the TICT state. TICT and AIE characteristics direct different properties of HBPSi-Cys, with TICT regulating solvatochromic emission wavelengths and AIE manipulating the emission intensity with a compensation effect. Density functional theory calculations reveal that the non-conjugated D-A structure in HBPSi-Cys was formed across the silicon bridge, with auxochromic sulfhydryl groups and adjacent amide groups as acceptor units and amine and hydroxyl groups as donor units. Additionally, the AIE-active HBPSi could be utilized as a fluorescent probe for the analysis of metal ions. After grafting the AS1411 aptamer to HBPSi-Cys as the recognition motif, HBPSi-Apt possesses excellent targeted bioimaging, drug loading, pH/GSH dual-responsive drug release, and visualized drug delivery performance. This work provides a new way to design functional AIE polymers with tunable optical properties, and the synthesized HBPSi-Cys shows great potential as a smart fluorescent biomaterial.

Water-Soluble Cationic Eu3+-Metallopolymer with High Quantum Yield and Sensitivity for Intracellular Temperature Sensing.

Lanthanide-based (Ln3+) luminescent materials are ideal candidates for use in fluorescence intracellular temperature sensing. However, it remains a great challenge to obtain a Ln3+-ratiometric fluorescence thermometer with high sensitivity and quantum yield in an aqueous environment. Herein, a cationic Eu3+-metallopolymer was synthesized via the coordination of Eu(TTA)3·2H2O with an AIE active amphipathic polymer backbone that contains APTMA ((3-acrylamidopropyl) trimethylammonium) and NIPAM (N-isopropylacrylamide) units, which can self-assemble into nanoparticles in water solution with APTMA and NIPAM as the hydrophilic shell. This polymer exhibited highly efficient dual-emissive white-light emission (Φ = 34.3%). Particularly, when the temperature rises, the NIPAM units will transform from hydrophilic to hydrophobic in the spherical core of the nanoparticle, while the VTPE units are moved from inside the nanoparticle to the shell, activating its nonradiative transition channel and thereby decreasing its energy transfer to Eu3+ centers, endowing the Eu3+-metallopolymer with an extremely high temperature sensing sensitivity within the physiological temperature range. Finally, the real-time monitoring of the intracellular temperature variation is further conducted.

Novel Affibody Molecules Specifically Bind to SARS-CoV-2 Spike Protein and Efficiently Neutralize Delta and Omicron Variants.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has been an unprecedented public health disaster in human history, and its spike (S) protein is the major target for vaccines and antiviral drug development. Although widespread vaccination has been well established, the viral gene is prone to rapid mutation, resulting in multiple global spread waves. Therefore, specific antivirals are needed urgently, especially those against variants. In this study, the domain of the receptor binding motif (RBM) and fusion peptide (FP) (amino acids [aa] 436 to 829; denoted RBMFP) of the SARS-CoV-2 S protein was expressed as a recombinant RBMFP protein in Escherichia coli and identified as being immunogenic and antigenically active. Then, the RBMFP proteins were used for phage display to screen the novel affibody. After prokaryotic expression and selection, four novel affibody molecules (Z14, Z149, Z171, and Z327) were obtained. Through surface plasmon resonance (SPR) and pseudovirus neutralization assay, we showed that affibody molecules specifically bind to the RBMFP protein with high affinity and neutralize against SARS-CoV-2 pseudovirus infection. Especially, Z14 and Z171 displayed strong neutralizing activities against Delta and Omicron variants. Molecular docking predicted that affibody molecule interaction sites with RBM overlapped with ACE2. Thus, the novel affibody molecules could be further developed as specific neutralization agents against SARS-CoV-2 variants. IMPORTANCE SARS-CoV-2 and its variants are threatening the whole world. Although a full dose of vaccine injection showed great preventive effects and monoclonal antibody reagents have also been used for a specific treatment, the global pandemic persists. So, developing new vaccines and specific agents are needed urgently. In this work, we expressed the recombinant RBMFP protein as an antigen, identified its antigenicity, and used it as an antigen for affibody phage-display selection. After the prokaryotic expression, the specific affibody molecules were obtained and tested for pseudovirus neutralization. Results showed that the serum antibody induced by RBMFP neutralized Omicron variants. The screened affibody molecules specifically bound the RBMFP of SARS-CoV-2 with high affinity and neutralized the Delta and Omicron pseudovirus in vitro. So, the RBMFP induced serum provides neutralizing effects against pseudovirus in vitro, and the affibodies have the potential to be developed into specific prophylactic agents for SARS-CoV-2 and its variants.

Construction of hyperbranched polysiloxane-based multifunctional fluorescent prodrug for preferential cellular uptake and dual-responsive drug release.

Hyperbranched polymers hold great promise in nanomedicine for their controlled chemical structures, sizes, multiple terminal groups and enhanced stability than linear amphiphilic polymer assemblies. However, the rational design of hyperbranched polymer-based nanomedicine with low toxic materials, selective cellular uptake, controlled drug release, as well as real-time drug release tracking remains challenging. In this work, a hyperbranched multifunctional prodrug HBPSi-SS-HCPT is constructed basing on the nonconventional aggregation-induced emission (AIE) featured hyperbranched polysiloxanes (HBPSi). The HBPSi is a biocompatible AIE macromolecule devoid of conjugates, showing a high quantum yield of 17.88% and low cytotoxicity. By covalently grafting the anticancer drug, 10-hydroxycamptothecin (HCPT), to the HBPSi through 3,3'-dithiodipropionic acid, HBPSi-SS-HCPT is obtained. The HBPSis demonstrate obvious AIE features and it turned to aggregation-caused quenching (ACQ) after grafting HCPT owing to the FRET behavior between HBPSi and HCPT in HBPSi-SS-HCPT. In addition to on-demand HCPT release in response to changes in environmental pH and glutathione, a series of in vitro and in vivo studies revealed that HBPSi-SS-HCPT exhibits enhanced accumulation in tumor tissues through the enhanced permeation and retention (EPR) effect and preferential cancer cell uptake by charge reversal, thus resulting in apoptotic cell death subsequently. This newly developed multifunctional HBPSi-SS-HCPT prodrug provides a biocompatible strategy for controlled drug delivery, preferential cancer cell uptake, on-demand drug release and enhanced antitumor efficacy.

Nucleocapsid protein of SARS-CoV-2 is a potential target for developing new generation of vaccine.

BACKGROUND: SARS-CoV-2 has spread worldwide causing more than 400 million people with virus infections since early 2020. Currently, the existing vaccines targeting the spike glycoprotein (S protein) of SARS-CoV-2 are facing great challenge from the infection of SARS-CoV-2 virus and its multiple S protein variants. Thus, we need to develop a new generation of vaccines to prevent infection of the SARS-CoV-2 variants. Compared with the S protein, the nucleocapsid protein (N protein) of SARS-CoV-2 is more conservative and less mutations, which also plays a vital role in viral infection. Therefore, the N protein may have the great potential for developing new vaccines. METHODS: The N protein of SARS-CoV-2 was recombinantly expressed and purified in Escherichia coli. Western Blot and ELISA assays were used to demonstrate the immunoreactivity of the recombinant N protein with the serum of 22 COVID-19 patients. We investigated further the response of the specific serum antibodies and cytokine production in BALB/c mice immunized with recombinant N protein by Western Blot and ELISA. RESULTS: The N protein had good immunoreactivity and the production of IgG antibody against N protein in COVID-19 patients was tightly correlated with disease severity. Furthermore, the N protein was used to immunize BALB/c mice to have elicited strong immune responses. Not only high levels of IgG antibody, but also cytokine-IFN-γ were produced in the N protein-immunized mice. Importantly, the N protein immunization induced a high level of IgM antibody produced in the mice. CONCLUSION: SARS-CoV-2 N protein shows a great big bundle of potentiality for developing a new generation of vaccines in fighting infection of SARS-CoV-2 and its variants.

Hyperbranched Polyborate: A Non-conjugated Fluorescent Polymer with Unanticipated High Quantum Yield and Multicolor Emission.

Non-conjugated fluorescent polymers have attracted great attention due to their excellent biocompatibility and environmental friendliness. However, it remains a huge challenge to obtain a polymer with high fluorescence quantum yield (QY) and multicolor emission simultaneously. Herein, we reported three kinds of nonaromatic hyperbranched polyborates (P1-P3) with multicolor emission, surprisingly, P2 also exhibits an unanticipated high QY (54.1 %). The natural bond orbital (NBO) analysis and density functional theory (DFT) calculation results revealed that the synergistic effect of rigid BO3 planar and flexible carbon chain, as well as the through-space dative bond in supramolecular aggregate, were the key factors contributing to the ultrahigh QY of P2. Moreover, the applications of P2 in Fe3+ ions detection and cell imaging were also investigated. This work provides a new perspective for designing non-conjugated fluorescent polymers with both high QY and multicolor emission.

Sustained expression of HPV16 E7 oncoprotein promotes p-AKT(Ser473)/p-Src(Tyr527) signaling to drive precancerous lesions to invasive cervical cancer.

Human papillomavirus (HPV) E7 oncogene plays the most important role in cervical cancer. However, whether E7 oncoprotein is continuously expressed, associated with AKT(Ser473)/p-Src(Tyr527) signaling to trigger cervical carcinogenesis remains unclear. Here, we explored first if HPV16 E7 oncoprotein could be detected in clinical biopsies and is sustainedly expressed, and then investigated how this oncoprotein interacted with AKT(Ser473)/p-Src(Tyr527) signaling in cancer progression. We used ZHPV16E7384 affibody to detect E7 expression in HPV16-positive cervical cancer biopsies and animal tumors by immunohistochemistry (IHC). Results showed that ZHPV16E7384 affibody had intense and specific staining for E7 oncoprotein in the detected specimen. The E7 oncoprotein was continuously expressed to correspond with the development of precancerous lesions to invasive cervical cancer. IHC staining also revealed that AKT, p-AKT(Ser473), Src and p-Src(Tyr527) proteins were expressed in both patient biopsies and animal tumors, with the highest levels of p-AKT(Ser473)/p-Src(Tyr527) present in invasive cancer. Furthermore, siRNA experiments revealed that HPV16 E7 knockdown significantly impaired expression of p-AKT(Ser473)/p-Src(Tyr527) in both HPV16 E7-positive cancer cells and transformed cells. In addition, transient expression of HPV16 E7 protein promoted significantly expression of p-AKT(Ser473)/p-Src(Tyr527) in primary human keratinocytes. Finally, co-immunoprecipitation analysis proved that HPV 16 E7 protein interacted reciprocally with p-AKT(Ser473)/p-Src(Tyr527). In conclusion, we demonstrate that HPV16 E7 oncoprotein is continuously expressed to promote expression of p-AKT(Ser473)/p-Src(Tyr527) leading to drive the initiation and progression of cervical cancer. Our data provide a novel insight that HPV16 E7 activates p-AKT(Ser473)/p-Src(Tyr527) to establish a mechanistic link between the oncogene and the AKT/Src signaling to trigger cervical carcinogenesis.

Characterization of Episomal Replication of Bovine Papillomavirus Type 1 DNA in Long-Term Virion-Infected Saccharomyces Cerevisiae Culture.

We have previously reported that bovine papillomavirus type 1 (BPV-1) DNA can replicate its genome and produce infectious virus-like particles in short term virion-infected S. cerevisiae (budding yeast) cultures (Zhao and Frazer 2002, Journal of Virology, 76:3359-64 and 76:12265-73). Here, we report the episomal replications of BPV-1 DNA in long term virion-infected S. cerevisiae culture up to 108 days. Episomal replications of the BPV-1 DNA could be divided into three patterns at three stages, early active replication (day 3-16), middle weak replication (day 23-34/45) and late stable replication (day 45-82). Two-dimensional gel electrophoresis analysis and Southern blot hybridization have revealed further that multiple replication intermediates of BPV-1 DNA including linear form, stranded DNA, monomers and higher oligomers were detected in the virion-infected yeast cells over the time course. Higher oligomers shown as covalently closed circular DNAs (cccDNAs) are the most important replication intermediates that serve as the main nuclear transcription template for producing all viral RNAs in the viral life cycle. In this study, the cccDNAs were generated at the early active replication stage with the highest frequencies and then at late stable replication, but they appeared to be suppressed at the middle weak replication. Our data provided a novel insight that BPV-1 genomic DNA could replicate episomally for the long period and produce the key replication intermediates cccDNAs in S. cerevisiae system.

A model for long-term infection of bovine papillomavirus type 1 in Saccharomyces cerevisiae.

We have previously reported that bovine papillomavirus type 1 (BPV1) can replicate its genome and produces infectious virus-like particles in short-term BPV1 virion-infected Sacharomyces cerevisiae (Zhao and Frazer, 2002). Here, we report viral RNA transcription and L1 capsid protein expression in long-term BPV1 virion-infected S. cerevisiae culture. Northern blot hybridization showed that viral RNA was detected in long-term BPV1-infected S. cerevisiae cultures (82-108 days). The levels of the viral RNA transcription varied significantly over the long time period, which showed active transcription at an early stage (Day 3 to Day 16), weak transcription at a middle stage (Day 23 to Day 45) and stable transcription at the late stage of culture (Day 55 to Day 82/85/95). Three major BPV1 transcripts of 4.3, 2.6 and 1.8 Kb were identified, with 4.3 Kb a minor transcript and the 1.8 Kb the most prominent transcript compared with the 2.6 Kb species. Immunoblotting showed that L1 capsid protein was expressed, with its variable amounts corresponding to the levels of RNA transcription over the time period. 35S-methionine/cysteine labeling and immunoprecipitation proved that the detected L1 protein was newly synthesized in BPV1-infected S. cerevisiae cultures. 33.3-54.2% of the cell colonies expressed L1 protein. Thus, the S. cerevisiae system, as a promising model, may be used not only for the study of virus like particle formation of BPV1 in vitro, but also for further functional analysis of individual viral genes in BPV1 life cycle. Keywords: BPV1; viral RNA transcription; expression of L1 capsid protein; virion-infected Saccharomyces cerevisiae.

Progressive Folding and Adaptive Multivalent Recognition of Alkyl Amines and Amino Acids in p-Sulfonatocalix[4]arene Hosts: Solid-State and Solution Studies.

Invited for this month's cover is the group of Dr. Mihail Barboiu from the Institut Europeen des Membranes of Montpellier, France and the Lehn Institute of Functional Materials at Sun-yat Sen University in Guangzhou, China. The cover picture shows the molecular recognition of folded 1,ω-amino-acids guests within p-sulfonatocalix[4]arene host anions stabilized with alternating hydrated cations and water molecules. Read the full text of the article at 10.1002/cplu.202000232.