End Modification Research Articles

Robust correlated magnetic moments in end-modified graphene nanoribbons

We conduct a theoretical examination of the electronic and magnetic characteristics of end-modified 7-atom wide armchair graphene nanoribbons (AGNRs). Our investigation is performed within the framework of a single-band Hubbard model, beyond a mean-field approximation. First, we carry out a comprehensive comparison of various approaches for accommodating di-hydrogenation configurations at the AGNR ends. We demonstrate that the application of an on-site potential to the modified carbon atom, coupled with the addition of an electron, replicates phenomena such as the experimentally observed reduction of the bulk-states (BS) gap. These results for the density of states (DOS) and electronic densities align closely with those obtained through a method explicitly designed to account for the orbital properties of hydrogen atoms. Furthermore, our study enables a clear differentiation between magnetic moments already described in a mean-field (MF) approach, which are spatially confined to the same sites as the topological end-states (ES), and correlation-induced magnetic moments, which exhibit localization along all edges of the AGNRs. Notably, we show the robustness of these correlation-induced magnetic moments relative to end modifications, within the scope of the method we employ.

Motivation and Barriers to Postoperative Rehabilitation Exercise in Type 2 Diabetic Patients with Rotator Cuff Injuries: A Qualitative Study.

Postoperative rehabilitation is particularly important for Rotator cuff injury. However, type 2 diabetic patients with RCI (T2DM-RCI) are at an elevated risk of rehabilitation failure. The factors influencing the postoperative rehabilitation management of these patients have yet to be elucidated. The objective of this study was to investigate the factors influencing the postoperative rehabilitation of T2DM-RCI patients. Data was collected using a descriptive qualitative research design. The sample included 22 interviewees, who were recruited in Subei People's Hospital according to the purposive sampling method. Colaizzi's method was employed for the purpose of evaluation in the course of the data analysis. Thematic analysis of the postoperative rehabilitation views of the interviewees identified eight sub-themes connected to three main themes in accordance with the Behaviour Change Wheel Theory. These were capability-related, opportunity-related, and motivation-related factors. It is imperative to enhance the glycaemic control and health perception of T2DM-RCI patients. To this end, rehabilitation programmes, comprising exercise and dietary modifications, must be tailored to the specific needs of each patient. Furthermore, it is crucial to harness the potential of family and social support to motivate patients to maintain a positive outlook.

Effect of cellulose reducing ends and primary hydroxyl groups modifications on cellulose-cellulase interactions and cellulose hydrolysis.

Cellulose reducing ends are believed to play a vital role in the cellulose recalcitrance to enzymatic conversion. However, their role in insoluble cellulose accessibility and hydrolysis is not clear. Thus, in this study, reducing ends of insoluble cellulose derived from various sources were modified by applying reducing and/or oxidizing agents. The effects of cellulose reducing ends modification on cellulose reducing ends, cellulose structure, and cellulose accessibility to cellulase were evaluated along with the impact on cellulose hydrolysis with complete as well purified cellulase components. Sodium borohydride (NaBH4) reduction and sodium chlorite-acetic acid (SC/AA) oxidation were able to modify more than 90% and 60% of the reducing ends, respectively, while the bicinchoninic acid (BCA) reagent applied for various cycles oxidized cellulose reducing ends to various extents. X-ray diffractograms of the treated solids showed that these treatments did not change the cellulose crystalline structure and the change in crystallinity index was insignificant. Surprisingly, it was found that the cellulose reducing ends modification, either through selective NaBH4 reduction or BCA oxidation, had a negligible impact on cellulose accessibility as well on cellulose hydrolysis rates or final conversions with complete cellulase at loadings as low as 0.5 mg protein/g cellulose. In fact, in contrast to what is traditionally believed, modifications of cellulose reducing ends by these two methods had no apparent impact on cellulose conversion with purified cellulase components and their synergy. However, SC/AA oxidation resulted in significant drop in cellulose conversion (10%-50%) with complete as well purified cellulase components. Nonetheless, further research revealed that the cause for drop in cellulose conversion for the SC/AA oxidation case was due to primary hydroxyl groups (PHGs) oxidation and not the oxidation of reducing ends. Furthermore, it was found that the PHGs modification affects cellulose accessibility and slows the cellulase uptake as well resulting in significant drop in cellulose conversions.

Unraveling the interplay between choline chloride and collagen mimetic peptide with facile end modifications: A case study of Gly-Gly-(Pro-Hyp-Gly)8-Gly-Gly

Collagen mimetic peptides (CMPs) have garnered substantial interest in the field of regenerative medicine, tissue engineering, and biomaterials owing to their promising prospects for utilization within these domains. In the last few years, significant research efforts have been made to study how small CMPs can autonomously arrange themselves to create large scale collagen-like formations. These structures exhibit potential for advancing the field of next-generation biomaterials. In this investigation, we have synthesized a peptide named G-POG8, with the sequence Gly-Gly-(Pro-Hyp-Gly)8-Gly-Gly, and we have examined the behaviour of G-POG8 under different concentrations of choline chloride (ChCl) through various biophysical techniques. These methodologies include circular dichroism (CD), UV–vis, fluorescence and Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) transmission electron microscopy (TEM), and dynamic light scattering (DLS). The findings indicate that the presence of Gly at both terminals of the CMP, G-POG8, results in a significant influence on the stability and aggregation behaviour of CMP triple helices. It is plausible that ChCl may have established favourable interactions with the terminal residues of G-POG8, potentially disrupting the end-to-end process of triple helix aggregation. This investigation lays the basis for the development of innovative biomaterials based on collagen, featuring improved properties, and opens up possibilities for cutting-edge biomedical applications.

Trinucleotide mRNA Cap Analogue N6-Benzylated at the Site of Posttranscriptional m6Am Mark Facilitates mRNA Purification and Confers Superior Translational Properties In Vitro and In Vivo.

Eukaryotic mRNAs undergo cotranscriptional 5'-end modification with a 7-methylguanosine cap. In higher eukaryotes, the cap carries additional methylations, such as m6Am─a common epitranscriptomic mark unique to the mRNA 5'-end. This modification is regulated by the Pcif1 methyltransferase and the FTO demethylase, but its biological function is still unknown. Here, we designed and synthesized a trinucleotide FTO-resistant N6-benzyl analogue of the m6Am-cap-m7GpppBn6AmpG (termed AvantCap) and incorporated it into mRNA using T7 polymerase. mRNAs carrying Bn6Am showed several advantages over typical capped transcripts. The Bn6Am moiety was shown to act as a reversed-phase high-performance liquid chromatography (RP-HPLC) purification handle, allowing the separation of capped and uncapped RNA species, and to produce transcripts with lower dsRNA content than reference caps. In some cultured cells, Bn6Am mRNAs provided higher protein yields than mRNAs carrying Am or m6Am, although the effect was cell-line-dependent. m7GpppBn6AmpG-capped mRNAs encoding reporter proteins administered intravenously to mice provided up to 6-fold higher protein outputs than reference mRNAs, while mRNAs encoding tumor antigens showed superior activity in therapeutic settings as anticancer vaccines. The biochemical characterization suggests several phenomena potentially underlying the biological properties of AvantCap: (i) reduced propensity for unspecific interactions, (ii) involvement in alternative translation initiation, and (iii) subtle differences in mRNA impurity profiles or a combination of these effects. AvantCapped-mRNAs bearing the Bn6Am may pave the way for more potent mRNA-based vaccines and therapeutics and serve as molecular tools to unravel the role of m6Am in mRNA.

Synthesis of Polyesters Containing Long Aliphatic Methylene Units by ADMET Polymerization and Synthesis of ABA-Triblock Copolymers by One-Pot End Modification and Subsequent Living Ring-Opening Polymerization.

The synthesis of high-molecular-weight (Mn up to 62,000 g/mol) polyesters has been achieved by acyclic diene metathesis (ADMET) polymerization of α,ω-dienes prepared from biobased bis(undec-10-enoate) and diols [ethylene glycol (M1), propylene glycol (M2), 1,9-nonanediol (M3), 1,4-benzenedimethanol (M4), and hydroquinone (M5)] using ruthenium-carbene catalysts. Replacement of the solvent during the ADMET polymerization was effective for obtainment of the high-molecular-weight polymers (expressed as P1-P5). The melting temperatures (Tm) in the resultant polyesters were dependent upon the diol (middle) segment employed, and the polymer prepared from M5 exceeded 100 °C (a Tm value of 122.5 °C). The polymerization of M3 and M4 in the presence of 1,4-cis-diacetoxy-2-butene (DAB, as the chain transfer agent) afforded the telechelic polyesters [P3(OAc)2 and P4(OAc)2, respectively] containing acetoxy end groups exclusively. The resultant polymers containing hydroxy group termini [P3(OH)2 and P4(OH)2], prepared by the selective deprotection of the acetoxy end groups, were treated with AlEt3 followed by addition of ε-caprolactone to afford the ABA-type triblock copolymers exclusively, through a living ring-opening polymerization. The depolymerization (hydrolysis) under basic conditions (NaOH aqueous solution) of P3 was explored.

Substrate promiscuity of Dicer toward precursors of the let-7 family and their 3′-end modifications

The human let-7 miRNA family consists of thirteen members that play critical roles in many biological processes, including development timing and tumor suppression, and their levels are disrupted in several diseases. Dicer is the endoribonuclease responsible for processing the precursor miRNA (pre-miRNA) to yield the mature miRNA, and thereby plays a crucial role in controlling the cellular levels of let-7 miRNAs. It is well established that the sequence and structural features of pre-miRNA hairpins such as the 5′-phosphate, the apical loop, and the 2-nt 3′-overhang are important for the processing activity of Dicer. Exceptionally, nine precursors of the let-7 family (pre-let-7) contain a 1-nt 3′-overhang and get mono-uridylated in vivo, presumably to allow efficient processing by Dicer. Pre-let-7 are also oligo-uridylated in vivo to promote their degradation and likely prevent their efficient processing by Dicer. In this study, we systematically investigated the impact of sequence and structural features of all human let-7 pre-miRNAs, including their 3′-end modifications, on Dicer binding and processing. Through the combination of SHAPE structural probing, in vitro binding and kinetic studies using purified human Dicer, we show that despite structural discrepancies among pre-let-7 RNAs, Dicer exhibits remarkable promiscuity in binding and cleaving these substrates. Moreover, the 1- or 2-nt 3′-overhang, 3′-mono-uridylation, and 3′-oligo-uridylation of pre-let-7 substrates appear to have little effect on Dicer binding and cleavage rates. Thus, this study extends current knowledge regarding the broad substrate specificity of Dicer and provides novel insight regarding the effect of 3′-modifications on binding and cleavage by Dicer.

ChemRAP uncovers specific mRNA translation regulation via RNA 5′ phospho-methylation

5′-end modifications play key roles in determining RNA fates. Phospho-methylation is a noncanonical cap occurring on either 5′-PPP or 5′-P ends. We used ChemRAP, in which affinity purification of cellular proteins with chemically synthesized modified RNAs is coupled to quantitative proteomics, to identify 5′-Pme “readers”. We show that 5′-Pme is directly recognized by EPRS, the central subunit of the multisynthetase complex (MSC), through its linker domain, which has previously been involved in key noncanonical EPRS and MSC functions. We further determine that the 5′-Pme writer BCDIN3D regulates the binding of EPRS to specific mRNAs, either at coding regions rich in MSC codons, or around start codons. In the case of LRPPRC (leucine-rich pentatricopeptide repeat containing), a nuclear-encoded mitochondrial protein associated with the French Canadian Leigh syndrome, BCDIN3D deficiency abolishes binding of EPRS around its mRNA start codon, increases its translation but ultimately results in LRPPRC mislocalization. Overall, our results suggest that BCDIN3D may regulate the translation of specific mRNA via RNA-5′-Pme.

Identification and Expression Analysis of the Nucleotidyl Transferase Protein (NTP) Family in Soybean (Glycine max) under Various Abiotic Stresses.

Nucleotidyl transferases (NTPs) are common transferases in eukaryotes and play a crucial role in nucleotide modifications at the 3' end of RNA. In plants, NTPs can regulate RNA stability by influencing 3' end modifications, which in turn affect plant growth, development, stress responses, and disease resistance. Although the functions of NTP family members have been extensively studied in Arabidopsis, rice, and maize, there is limited knowledge about NTP genes in soybeans. In this study, we identified 16 members of the NTP family in soybeans, including two subfamilies (G1 and G2) with distinct secondary structures, conserved motifs, and domain distributions at the protein level. Evolutionary analysis of genes in the NTP family across multiple species and gene collinearity analysis revealed a relatively conserved evolutionary pattern. Analysis of the tertiary structure of the proteins showed that NTPs have three conserved aspartic acids that bind together to form a possible active site. Tissue-specific expression analysis indicated that some NTP genes exhibit tissue-specific expression, likely due to their specific functions. Stress expression analysis showed significant differences in the expression levels of NTP genes under high salt, drought, and cold stress. Additionally, RNA-seq analysis of soybean plants subjected to salt and drought stress further confirmed the association of soybean NTP genes with abiotic stress responses. Subcellular localization experiments revealed that GmNTP2 and GmNTP14, which likely have similar functions to HESO1 and URT1, are located in the nucleus. These research findings provide a foundation for further investigations into the functions of NTP family genes in soybeans.

Terminal modifications independent cell-free RNA sequencing enables sensitive early cancer detection and classification

Cell-free RNAs (cfRNAs) offer an opportunity to detect diseases from a transcriptomic perspective, however, existing techniques have fallen short in generating a comprehensive cell-free transcriptome profile. We develop a sensitive library preparation method that is robust down to 100 µl input plasma to analyze cfRNAs independent of their 5’-end modifications. We show that it outperforms adapter ligation-based method in detecting a greater number of cfRNA species. We perform transcriptome-wide characterizations in 165 lung cancer, 30 breast cancer, 37 colorectal cancer, 55 gastric cancer, 15 liver cancer, and 133 cancer-free participants and demonstrate its ability to identify transcriptomic changes occurring in early-stage tumors. We also leverage machine learning analyses on the differentially expressed cfRNA signatures and reveal their robust performance in cancer detection and classification. Our work sets the stage for in-depth study of the cfRNA repertoire and highlights the value of cfRNAs as cancer biomarkers in clinical applications.

Development of simple purification method for oligonucleotides synthesized using phosphoramidite for 5′-end modification as capping reagent

Oligonucleotide therapeutics are generally prepared via solid-phase synthesis, and many impurities derived from the synthesis process are present in crude oligonucleotides. Among the various impurities typical of oligonucleotide synthesis, shortmers, which lack a few residues from the desired oligonucleotide therapeutics, are difficult to remove using conventional high-performance liquid chromatography (HPLC) purification because they have similar structures and physical properties to the desired oligonucleotide. In this study, we developed a simple purification method for oligonucleotide therapeutics. In our strategy, the retention of shortmers on the reversed-phase HPLC column was increased by using a highly lipophilic phosphoramidite, which is a reagent for 5′-end modification of oligonucleotides, instead of acetic anhydride during solid-phase synthesis, and only the target oligonucleotide could be eluted from a reversed-phase HPLC pretreatment column.

De novo fabrication of custom-sequence plasmids for the synthesis of long DNA constructs with extrahelical features

DNA constructs for single-molecule experiments often require specific sequences and/or extrahelical/noncanonical structures to study DNA-processing mechanisms. The precise introduction of such structures requires extensive control of the sequence of the initial DNA substrate. A commonly used substrate in the synthesis of DNA constructs is plasmid DNA. Nevertheless, the controlled introduction of specific sequences and extrahelical/noncanonical structures into plasmids often requires several rounds of cloning on pre-existing plasmids whose sequence one cannot fully control. Here, we describe a simple and efficient way to synthesize 10.1-kb plasmids de novo using synthetic gBlocks that provides full control of the sequence. Using these plasmids, we developed a 1.5-day protocol to assemble 10.1-kb linear DNA constructs with end and internal modifications. As a proof of principle, we synthesize two different DNA constructs with biotinylated ends and one or two internal 3′ single-stranded DNA flaps, characterize them using single-molecule force and fluorescence spectroscopy, and functionally validate them by showing that the eukaryotic replicative helicase Cdc45/Mcm2-7/GINS (CMG) binds the 3′ single-stranded DNA flap and translocates in the expected direction. We anticipate that our approach can be used to synthesize custom-sequence DNA constructs for a variety of force and fluorescence single-molecule spectroscopy experiments to interrogate DNA replication, DNA repair, and transcription.

Electronic Nicotine Delivery Systems and E-Liquid Modifications to Vape Cannabis Depicted in Online Videos

Electronic nicotine delivery systems (ENDS) were created to vape nicotine e-liquids; however, social media demonstrates increased ENDS modifications to vape cannabis. Analysis of social media content helps with understanding ENDS modifications for cannabis use, overlapping markets for ENDS and cannabis, and the need for additional regulation. To analyze online videos for use, modification, and marketing of ENDS to vape cannabis. In this qualitative study, 10 searches were performed on YouTube on July 14, 2022, using different combinations of relevant search terms to identify videos depicting modifications to ENDS and e-liquids to vape cannabis. The first 40 videos from each search (400 videos total, 152 without duplicates) were extracted, of which 59 included depiction or discussion of cannabis vaping content. Content analysis of videos included iterative development of codes, consensus building across team members, and reliability checks. Metadata (ie, video length, number of likes, comments, and views) were extracted for included videos. Coding was performed for uploader type, modifications to ENDS and e-liquids, devices used, cannabis products vaped, age restriction, purchasing links, health claims, and discussion of warning messages and cannabis regulations. Of the 59 videos analyzed, 34 (58%) included tetrahydrocannabinol; 33 (56%), cannabidiol; and 8 (14%), both. A total of 21 videos (36%) were age-restricted, while 25 (42%) included purchasing links for cannabis products, 20 (34%) for ENDS, and 7 (12%) for nicotine e-liquids. Twenty-six videos (44%) made claims about health benefits of vaping cannabis. Forty-one videos (69%) demonstrated vaping manufacturer-made cannabis products (eg, cannabis concentrates) with no modifications needed. Eighteen videos (31%) depicted modifications to e-liquids or ENDS for cannabis use. The most frequent modification was mixing e-liquids with cannabis products to be compatible with ENDS. The most frequently reported reason for modifications was to vape cannabis in public by using the same devices used for nicotine. This qualitative study of online videos found high frequencies of statements about health benefits from vaping cannabis, frequent purchasing links, and inadequate age restrictions. Exposure to such content on social media platforms may increase risk of cannabis vaping among youth. Use of the same devices for multiple substances may also enable dual use and complicate the US Food and Drug Administration's regulation of ENDS.

Shortcut barcoding and early pooling for scalable multiplex single-cell reduced-representation CpG methylation sequencing at single nucleotide resolution.

DNA methylation is essential for a wide variety of biological processes, yet the development of a highly efficient and robust technology remains a challenge for routine single-cell analysis. We developed a multiplex scalable single-cell reduced representation bisulfite sequencing (msRRBS) technology. It allows cell-specific barcoded DNA fragments of individual cells to be pooled before bisulfite conversion, free of enzymatic modification or physical capture of the DNA ends, and achieves read mapping rates of 62.5± 3.9%, covering 60.0±1.4% of CpG islands and 71.6± 1.6% of promoters in K562 cells. Its reproducibility is shown in duplicates of bulk cells with close to perfect correlation (R=0.97-0.99). At a low 1 Mb of clean reads, msRRBS provides highly consistent coverage of CpG islands and promoters, outperforming the conventional methods with orders of magnitude reduction in cost. Here, we use this method to characterize the distinct methylation patterns and cellular heterogeneity of six cell lines, plus leukemia and hepatocellular carcinoma models. Taking 4 hof hands-on time, msRRBS offers a unique, highly efficient approach for dissecting methylation heterogeneity in a variety of multicellular systems.

Selective Characterization of mRNA 5' End-Capping by DNA Probe-Directed Enrichment with Site-Specific Endoribonucleases.

The N7-methyl guanosine cap structure is an essential 5' end modification of eukaryotic mRNA. It plays a critical role in many aspects of the life cycle of mRNA, including nuclear export, stability, and translation. Equipping synthetic transcripts with a 5' cap is paramount to the development of effective mRNA vaccines and therapeutics. Here, we report a simple and flexible workflow to selectively isolate and analyze structural features of the 5' end of an mRNA by means of DNA probe-directed enrichment with site-specific single-strand endoribonucleases. Specifically, we showed that the RNA cleavage by site-specific RNases can be effectively steered by a complementary DNA probe to recognition sites downstream of the probe-hybridized region, utilizing a flexible range of DNA probe designs. We applied this approach using human RNase 4 to isolate well-defined cleavage products from the 5' end of diverse uridylated and N1-methylpseudouridylated mRNA 5' end transcript sequences. hRNase 4 increases the precision of the RNA cleavage, reducing product heterogeneity while providing comparable estimates of capped products and their intermediaries relative to the widely used RNase H. Collectively, we demonstrated that this workflow ensures well-defined and predictable 5' end cleavage products suitable for analysis and relative quantitation of synthetic mRNA 5' cap structures by UHPLC-MS/MS.

Stable nuclear transformation methods for Euglena gracilis and its application to a related Euglenida

Euglenida is a taxonomic group of single-celled flagellates that have a variety of nutrient uptake strategies, making this an excellent model for studying the evolutionary acquisition of secondary chloroplasts. Among Euglenida, Euglena gracilis is the most extensively studied at the biochemical and molecular levels. However, the lack of a widely adopted method of nuclear genome transformation has hindered genetic studies in this organism. Herein, we present a novel nuclear transformation electroporation method that utilizes the 5′ adjacent region sequences of endogenous genes in E. gracilis. We used a NanoLuc reporter to evaluate promoter activity to identify four endogenous promoter candidates with superior luciferase transcriptional activity compared with the activity of the commonly used CaMV 35S promoter in E. gracilis nuclear transformation methods. We used G418 selection to obtain stable E. gracilis transformants harboring the transgene in their genomic DNA. Furthermore, we extended the applicability of our method to Rapaza viridis, a kleptoplastic species in Euglenida. Introduction of the DNA constructs developed for E. gracilis into R. viridis via electroporation generated stable G418-resistant strains exhibiting robust luciferase activity. The introduced promoter sequences functioned effectively, and accurate 5′ end modifications of mRNA were observed in both E. gracilis and R. viridis transformants. These findings demonstrate the broad applicability of our nuclear transformation method across multiple Euglenida species, facilitating molecular biology and genetic diversity studies in this taxonomic group.

Boosting stability and therapeutic potential of proteolysis-resistant antimicrobial peptides by end-tagging β-naphthylalanine.

Recently, much emphasis has been placed on solvingthe intrinsic defects of antimicrobial peptides (AMPs), especially their susceptibility to protease digestion for the systemic application of antibacterial biomaterials. Although many strategies have increased the protease stability of AMPs, antimicrobial activity was severely compromised, thereby substantially weakening their therapeutic effect. To address this issue, we introduced hydrophobic group modifications at the N-terminus of proteolysis-resistant AMPs D1 (AArIIlrWrFR) through end-tagging with stretches of natural amino acids (W and I), unnatural amino acid (Nal) and fatty acids. Of these peptides, N1 tagged with a Nal at N-terminus showed the highest selectivity index (GMSI=19.59), with a 6.73-fold improvement over D1. In addition to potent broad-spectrum antimicrobial activity, N1 also exhibited high antimicrobial stability toward salts, serum and proteases in vitro and ideal biocompatibility and therapeutic efficacy in vivo. Furthermore, N1 killed bacteria through multiple mechanisms, involving disruption of bacterial membranes and inhibition of bacterial energy metabolism. Indeed, appropriate terminal hydrophobicity modification opens up new avenues for developing and applying high-stability peptide-based antibacterial biomaterials. STATEMENT OF SIGNIFICANCE: To improve the potency and stability of proteolysis-resistant antimicrobial peptides (AMPs) without increasing toxicity, we constructed a convenient and tunable platform based on different compositions and lengths of hydrophobic end modifications. By tagging an Nal at the N-terminal, the obtained target compound N1 exhibited strong antimicrobial activity and desirable stability under multifarious environments in vitro (proteases, salts and serum), and also showed favorable biocompatibility and therapeutic efficacy in vivo. Notably, N1 exerted its bactericidal effect by damaging bacterial cell membranes and inhibiting bacterial energy metabolism in a dual mode. The findings provide a potential method for designing or optimizing proteolysis-resistant AMPs thus promoting the development and application of peptide-based antibacterial biomaterial.

Novel Chain-End Modification of Polymer Iodides via Reversible Complexation-Mediated Polymerization with Functionalized Radical Generation Agents.

The modification of polymer chain ends is important in order to produce highly functional polymers. A novel chain-end modification of polymer iodides (Polymer-I) via reversible complexation-mediated polymerization (RCMP) with different functionalized radical generation agents, such as azo compounds and organic peroxides, was developed. This reaction was comprehensively studied for three different polymers, i.e., poly (methyl methacrylate), polystyrene and poly (n-butyl acrylate) (PBA), two different functional azo compounds with aliphatic alkyl and carboxy groups, three different functional diacyl peroxides with aliphatic alkyl, aromatic, and carboxy groups, and one peroxydicarbonate with an aliphatic alkyl group. The reaction mechanism was probed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The combination of PBA-I, iodine abstraction catalyst and different functional diacyl peroxides enabled higher chain-end modification to desired moieties from the diacyl peroxide. The dominant key factors for efficiency in this chain-end modification mechanism were the combination rate constant and the amount of radicals generated per unit of time.

Engineered liposomes to deliver nucleic acid mimics in Escherichia coli.

Antisense oligonucleotides (ASOs) composed of nucleic acid mimics (NAMs) monomers are considered as potential novel therapeutic drugs against bacterial infections. However, bacterial envelopes are generally impermeable to naked oligonucleotides. Herein, liposomes loaded with NAMs-modified oligonucleotides (LipoNAMs) were evaluated to deliver ASOs in Escherichia coli. Specifically, we tested several surface modifications that included methoxyPEG conjugated to different lipid anchors or modification of the PEG distal ends with maleimide groups and antibodies. MethoxyPEG coated LipoNAMs showed low delivery efficiency for most bacteria, but maleimide-functionalized PEG LipoNAMs were able to deliver ASOs to nearly half of the bacterial population. Conjugation of antibodies to maleimide-functionalized PEG LipoNAMs increased 1.3-fold the delivery efficiency, enhancing the selectivity towards E. coli and biocompatibility. This work demonstrated for the first time that the coupling of antibodies to PEGylated liposomes can significantly improve the delivery of ASOs in E. coli, which might bring alternative routes for the treatment of bacterial infections in the future.

Tailoring the Chemical Structure of Cellulose Nanocrystals by Amine Functionalization

AbstractThe surface functionalization of cellulose nanocrystals is presently considered a useful and straightforward tool for accessing very reliable biocompatible and biodegradable nanostructures with tailored physical and chemical properties. However, to date the fine characterization of the chemical appendages introduced onto cellulose nanocrystals remains a challenge, due to the low sensitivity displayed by the most common techniques towards surface functionalization. In this paper, we demonstrate the easy functionalization of cellulose nanocrystals with aliphatic and aromatic amines, demonstrating the tunability of their properties in dependence on the selected functionality. Then, we apply to colloidal suspensions of modified nanocrystals 1H NMR analysis to elucidate their surface structure. To the best of our knowledge, this is the first report where such investigation was performed on cellulose nanocrystals presenting both surface and reducing end modification. These results involve interesting implications for the fields of cultural heritage and of materials chemistry.