Chemical Motifs Research Articles

Supradecoration induced novel Properties: A comparative study of Ferrocene and Ferrocenyl α-aminophosphonate

Decorating chemical motifs with appropriate functional groups capable of supramolecular interactions hold key in modulating these novel systems for targeted applications. This work by means of a comparative study of Ferrocene and Ferrocenyl α- aminophosphonate highlight supradecoration induced multi paradigm properties across materials to medicine. The observed results indicate an increase in crystal framework energy with induction of mechanochromism and aggregation-induced emission in case of Ferrocenyl-α-amino phosphonate as novel supra decorated Ferrocene motif. Comparative BSA and BLC studies indicated improved biocompatibility with enhancement of catalase enzyme activity in case of Ferrocenyl-α- aminophosphonate compared to pristine Ferrocene. The relative quantification of intermolecular non covalent interactions of Ferrocene and Ferrocenyl-α- aminophosphonate evaluated using Quantum crystallographic methods and non-covalent interaction analysis were used to corroborate the supramodulation effects. The observed influence of Ferrocenyl α-aminophosphonate on the enzymatic activity of catalase was also examined using a comparative molecular docking analysis. The docking results corroborated influence of supradecoration on binding affinity and binding site, which are vital for designing ligands of enhanced catalase activity and also helpful in prediction of newer regulatory sites on enzyme. Taken together this work signifies how supra decoration of Ferrocene motif with functionalities capable of diverse intermolecular non-covalent interactions modulate molecular properties for newer applications.

DSSBU: A novel mass spectrometry-cleavable analogue of the BS3 cross-linker

Protein cross-linking has assumed an irreplaceable role in structural proteomics. Recently, significant efforts have been made to develop novel mass spectrometry (MS)-cleavable reagents. At present, only water-insoluble MS-cleavable cross-linkers are commercially available. However, to comprehensively analyse the various chemical and structural motifs making up proteins, it is necessary to target different protein sites with varying degrees of hydrophilicity. Here we introduce the new MS-cleavable cross-linker disulfodisuccinimidyl dibutyric urea (DSSBU), which we have developed in-house for this purpose. DSSBU contains an N-hydroxysulfosuccinimide (sulfo-NHS) reactive group, so it can serve as a water-soluble counterpart to the widely used cross-linker disuccinimidyl dibutyric urea (DSBU). To investigate the applicability of DSSBU, we compared the efficacy of four similar cross-linkers: bis[sulfosuccinimidyl] suberate (BS3), disuccinimidyl suberate (DSS), DSBU and DSSBU with bovine serum albumin. In addition, we compared the efficacy of DSBU and DSSBU with human haemoglobin. Our results demonstrate that the sulfo-NHS group ensures the superior water solubility of DSSBU and thus negates the need for organic solvents such as dimethyl sulfoxide while preserving the effectivity of urea-based MS-cleavable crosslinkers such as DSBU. Additionally, it makes it possible to target polar regions in proteins. The data gathered are available via ProteomeXchange under identifier PXD055284. SignificanceWe have synthesized the novel protein cross-linker DSSBU, which combines sulfo-NHS ester chemistry with a mass spectrometry-cleavable urea group. This makes DSSBU a water-soluble, MS-cleavable cross-linker that reacts with amino groups. To our knowledge, it is the first cross-linker which combines all three of these characteristics. We have tested the performance of our novel cross-linker on bovine serum albumin, a model widely used by the cross-linking mass spectrometry community, and on human haemoglobin. We have comprehensively assessed the performance of DSSBU and compared its efficacy with that of three other cross-linkers in current use (BS3, DSS and DSBU). We conclude that our novel cross-linker surpasses its MS-non-cleavable analogue BS3 in performance and that its water solubility eliminates the need for organic solvents while its hydrophilicity allows for the targetting of polar regions in proteins. Therefore, it will likely become a significant addition to the portfolio of N-hydroxysuccinimide ester cross-linkers.

Boron-Nitrogen-Containing Benzene Valence Isomers.

Benzene is one of the most ubiquitous structural motifs in chemistry. The valence isomers of benzene have also attracted synthetic chemists' attention due to their unique structures, bonding, and reactivity. We have been investigating boron-nitrogen-containing benzene valence isomers via photoisomerization of 1,2-azaborines. In this contribution, we summarize recent developments of these highly strained BN-heterocyclic compounds including their synthesis, characterization, proposed mechanism of formation, and their potential applications.

Antioxidant activity of Zuccagnia-type propolis: A combined approach based on LC-HRMS analysis of bioanalytical-guided fractions and computational investigation

This study reports a combined approach to assess the antioxidant activity of Zuccagnia-type propolis. Fractions exhibiting the highest antioxidant activities evidenced by DPPH, a β-carotene bleaching and superoxide radical scavenging activity-non-enzymatic assays, were processed by LC-HRMS/MS to characterize the relevant chemical compounds. A computational protocol based on the DFT calculations was used to rationalize the main outcomes. Among the 28 identified flavonoids, caffeic acids derivatives were in the fraction exhibiting the highest antioxidant activity, with 1-methyl-3-(4′-hydroxyphenyl)-propyl caffeic acid ester and 1-methyl-3-(3′,4′-dihydroxyphenyl)-propyl caffeic acid ester as major components. Results clearly showed roles of specific chemical motifs, which can be supported by the computational analysis.This is the first report ascribing the antioxidant ability of Zuccagnia-type propolis to its content in specific caffeic acid derivatives, a potential source of radical scavenging phytochemicals. The proposed protocol can be extended to the study of other plant-products to address the most interesting bioactive compounds.

Photocatalytic Three-Component Acylcarboxylation of Alkenes with CO2.

γ-Keto acid is a valuable chemical motif in a wide range of fields including organic, biological, and medicinal chemistry. However, its single-step synthesis is challenging because of the mismatch of the carbonyl polarity and low tolerance of carboxylic acids. Herein, we report the single-step syntheses of γ-keto acids using alkenes and CO2. Our photocatalytic system enabled the transformation of alkenes under mild conditions in high yields (up to 95%) with broad substrate generality (35 examples).

Oxygen-Promoted on-Surface Synthesis of Polyboroxine Molecules.

We present a protocol for the on-surface synthesis of polyboroxine molecules derived from boroxine molecules precursors. This process is promoted by oxygen species present on the Au(111) surface: oxygen atoms facilitate the detachment of naphthalene units of trinaphthyl-boroxine molecules and bridge two unsaturated boroxine centers to form a boroxine-O-boroxine chemical motif. X-ray spectroscopic characterization shows that, as the synthesis process proceeds, it progressively tunes the electronic properties of the interface, thus providing a promising route to control the electron level alignment.

Regioselective Annulation of 6-Carboxy-Substituted Pyrones as a Two-Carbon Unit in Formal [4 + 2] Cycloaddition Reactions.

Heterocycles serve as a critical motif in chemistry, but despite being present in more than 85% of pharmaceuticals, there are limited methods for their construction. Here, we describe the incorporation of intact pyrone (2H-pyran-2-one) into larger ring systems via annulation. In a formal [4 + 2] cycloaddition, the pyrone regioselectively accepts a benzylic anion as a nucleophile in a conjugate addition fashion, with the subsequent pyrone-derived enolate attaching to a pendant ester on the initial nucleophile. Subsequent base-driven enolate formation and elimination establish aromaticity of the newly formed ring. After optimization of this process using an NMR-based assessment to overcome solubility and separation challenges, the reaction was successfully applied to a library of 6-ester and -amide-substituted pyrones and using a phenyl ester and other substituted sulfoxides. This technology enables the incorporation of intact pyrone rings into more complex systems, such as for the total synthesis of the natural product thermorubin.

Iron‐Catalyzed Site‐Selective α‐C−H Functionalization in N‐Benzyl Tetrahydroisoquinolines: Enabling Tertiary Amine Transformations

AbstractThis article presents a catalytic approach for site‐selective α‐C−H functionalization of N‐benzyl tetrahydroisoquinolines, which are important tertiary amine derivatives. Using iron salt as a catalyst, we have selectively functionalized carbon‐hydrogen bonds of tertiary amine molecules with diverse moieties, such as imidazopyridine, indoles, and phenylacetylenes. The method offers a broad substrate scope and excellent functional group tolerance, making it a valuable tool for the synthesis of complex molecules. A mechanism is also proposed based on control experiments, which explains the probable reason for selectivity. This iron‐catalyzed C−H functionalization represents a significant advancement in the field of organic synthesis, showcasing the potential of iron catalysis for the construction of valuable chemical motifs.

An anti-mitotic compound, (+)-6-tuliposide A, isolated from the Canadian glacier lily, Erythronium grandiflorum

The Canadian prairie ecosystem is subjected to abiotic and biotic conditions that induce plants to produce secondary metabolites that affect mammalian physiology. Extracts prepared from certain plant species native to Canadian prairie and montane cordillera ecosystems have previously been shown to have anti-mitotic activity on human cancer cell lines. In this study, we investigated the glacier lily, Erythronium grandiflorum (Liliaceae), in which the species was the most phylogenetically distant from Asteraceae and had anti-mitotic activity. When added to cell lines, E. grandiflorum extracts induced rounded cell morphology and arrested cells in the G2/M phase of the cell cycle. Of the cells that displayed a rounded phenotype, all were positive for phospho-histone H3 and contained a distorted mitotic spindle. This anti-mitotic activity was distinct from that of the compound colchicine, which has been previously isolated from the Liliaceae family. By biology-guided fractionation, we isolated the natural product (+)-6-tuliposide A and are the first to report its anti-mitotic activity. These results reveal a chemical motif in secondary metabolites and expand the range of Canadian prairie plants with anti-mitotic activity that can become new scientific tools or used in the development of anti-proliferative medicines.

Evaluating Pigments as a Biosignature: Abiotic/Prebiotic Synthesis of Pigments and Pigment Mimics in Planetary Environments.

Pigments serve a multitude of functions in biology including light harvesting for photosynthesis, radiation protection, membrane support, and defense. The ubiquity of pigments-especially within extremophiles found in high-radiation, high-salinity, and dry environments-and their detectability via mission-ready techniques have elevated these molecules as promising targets in the search for evidence of life elsewhere. Moreover, the detection of pigments has been proposed as a "smoking gun" for extraterrestrial life as it has been suggested that these molecules cannot be generated abiotically. However, while pigments may hold promise as a biosignature, current understanding of their possible prebiotic origins remains understudied and uncertain. Better understanding of the abiotic synthesis of pigments is critical for evaluating the biogenicity of any pigment detected during missions, including by the Mars Perseverance rover or from returned samples. Compounding this uncertainty is the broad definition of pigment as it includes any compound capable of absorbing visible light and by itself does not specify a particular chemical motif. While not experimentally verified, there are promising prebiotic routes for generating pigments including hemes, chlorophylls, and carotenoids. Herein, we review the biochemistry of pigments, the inherent assumptions made when searching for these molecules in the field, their abiotic synthesis in industry and prebiotic reactions, prebiotically relevant molecules that can mimic their spectral signatures, and implications/recommendations for future work.

Chemical Derivatization Leads to the Discovery Of Novel Analogs of Azotochelin, a Natural Siderophore, as Promising Anticancer Agents.

Siderophores are structurally unique medicinal natural products and exhibit considerable therapeutic potential. Herein, we report the design and synthesis of azotochelin, a natural siderophore, and an extensive library of azotochelin analogs and their anticancer properties. We modified the carboxylic acid and the aromatic ring of azotochelin using various chemical motifs. We evaluated the cytotoxicity of the compounds against six different cancer cell lines (KB-3-1, SNB-19, MCF-7, K-562, SW-620, and NCI-H460) and a non-cancerous cell line (HEK-293). Among the twenty compounds tested, the IC50 values of nine compounds (14, 32, 35-40, and 54) were between 0.7 and 2.0 μM against a lung cancer cell line (NCI-H460). Moreover, several compounds showed good cytotoxicity profile (IC50 <10 μM) against the tested cancer cell lines. The flow cytometry analysis showed that compounds 36 and 38 induced apoptosis in NCI-H460 in a dose-dependent manner. The cell cycle analysis indicated that compounds 36 and 38 significantly arrested the cell cycle at the S phase to block cancer cell proliferation in the NCI-H460 cell line. The study has produced various novel azotochelin analogs that are potentially effective anticancer agents and lead compounds for further synthetic and medicinal chemistry exploration.

Synthetic Antifreeze Glycoproteins with Potent Ice-Binding Activity.

Antifreeze glycoproteins (AFGPs) are produced by extremophiles to defend against tissue damage in freezing climates. Cumbersome isolation from polar fish has limited probing AFGP molecular mechanisms of action and limited development of bioinspired cryoprotectants for application in agriculture, foods, coatings, and biomedicine. Here, we present a rapid, scalable, and tunable route to synthetic AFGPs (sAFGPs) using N-carboxyanhydride polymerization. Our materials are the first mimics to harness the molecular size, chemical motifs, and long-range conformation of native AFGPs. We found that ice-binding activity increases with chain length, Ala is a key residue, and the native protein sequence is not required. The glycan structure had only minor effects, and all glycans examined displayed antifreeze activity. The sAFGPs are biodegradable, nontoxic, internalized into endocytosing cells, and bystanders in cryopreservation of human red blood cells. Overall, our sAFGPs functioned as surrogates for bona fide AFGPs, solving a long-standing challenge in accessing natural antifreeze materials.

Abstract 4494: Cryo-EM structure-based small molecule inhibitor drugs targeting CSPG4/NG2 in glioblastoma

Abstract Background: Glioblastoma (GBM) is the most malignant primary brain tumor with a median survival of 15 months despite aggressive multimodal treatment. There is an urgent need for novel drug discovery for GBM. CSPG4/NG2 transmembrane proteoglycan is a validated target, upregulated in 50% of GBM patient tumours, drives malignant progression and is independently prognostic for poor survival. We have recently identified a cancer specific 13 bp frameshift deletion in the CSPG4/NG2 gene (CSPG4/NG2del13), which leads to reduced protein expression and slowed cell growth in vitro and tumor take in vivo. The 3D structure of CSPG4/NG2 has not yet been solved, and unsuited for structure prediction by AlphaFold2 due to its size and PTMs. The structure of CSPG4/NG2 domain 1 (residues 411-547), containing the site of the 13 bp deletion, has been solved using cryo-EM and can be useful for new drug design. We hypothesize that a small-molecule inhibitor that binds to this 13 bp region of the CSPG4/NG2 proteoglycan, might induce the same phenotype as the 13 bp deletion. Methods: Using the published structure of domain 1, we performed in silico analysis to predict binding sites and docked 1280 compounds from the Prestwick Chemical library’s database of FDA-approved drugs to these sites. The high ranked hits were further tested in vitro in GBM cells. Clonogenic survival, cell proliferation and scratch-wound assays were performed in patient derived P3, A172 and in CSPG4/NG2del13 heterozygous (HZ) GBM cells, that served as controls. Results: Three binding sites were found in the close proximity to the 13 bp deletion region within the N-terminal domain 1 of CSPG4/NG2. Docking analysis revealed multiple drug candidates bound to the predicted binding site, three of which were further analyzed. Dopamine is found to closely interact with CSPG4/NG2 domain 1, near the 13 bp deletion site, forming hydrogen bonds with Glu413 and Glu521. Pyrazinamide forms two hydrogen bonds with Glu521. 5-Azacytidine fits well into active site 1, establishing hydrogen bonds with key residues Gly475, Glu482, Val472 and Thr473. The in vitro functional assays showed that the top hits have a dose dependent negative effect on colony formation and cell proliferation in P3 and A172 GBM cells (P &amp;lt; 0.0001). The treatment with the same drug IC50 doses led to a growth rescue in the CSPG4/NG2del13 HZ cells compared to the WT cells (P &amp;lt; 0.001). 5-Azacytidine showed a significant inhibitory effect (P &amp;lt; 0.0001) on cell migration in P3, A172 GBM cells and also in HZ cells, (P &amp;lt; 0.001). Conclusion: The residues spanning the site of 13 bp deletion have chemical motifs that are salient for docking small molecule inhibitors that disrupt CSPG4/NG2 function. N-terminus domain 1 and full-length CSPG4/NG2 proteins for Cryo-EM 3D structure determination are being used to interrogate biochemical kinetics and identify new target regions. Citation Format: Lasse Neset, Mia Kristin Nilsen, Victoria Smith Arnesen, Kazi Asraful Alam, Martha Chekenya, Mohummad Aminur Rahman. Cryo-EM structure-based small molecule inhibitor drugs targeting CSPG4/NG2 in glioblastoma [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 4494.

Engineered Metal‐Loaded Biohybrids to Promote the Attachment and Electron‐Shuttling between Enzymes and Carbon Electrodes

AbstractThe inorganic content and the catalytic performance pose metal‐loaded enzyme nanoflowers as promising candidates for developing bioelectrodes capable of functioning without the external addition of a redox mediator. However, these protein‐inorganic hybrids have yet to be successfully applied in combination with electrode materials. Herein, the synthesis procedure of these bionanomaterials is reproposed to precisely control the morphology, composition, and performance of this particular protein‐mineral hybrid, formed by glucose oxidase and cobalt phosphate. This approach aims to enhance the adherence and electron mobility between the enzyme and a carbon electrode. The strategy relies on dressing the protein in a tailored thin nanogel with multivalent chemical motifs. The functional groups of the polymer facilitate the fast protein sequence‐independent biomineralization. Furthermore, the engineered enzymes enable the fabrication of robust cobalt‐loaded enzyme inorganic hybrids with exceptional protein loads, exceeding 90% immobilization yields. Notably, these engineered biohybrids can be readily deposited onto flat electrode surfaces without requiring chemical pre‐treatment. The resulting bioelectrodes are robust and exhibit electrochemical responses even without the addition of a redox mediator, suggesting that cobalt complexes promote electron wiring between the active site of the enzyme and the electrode.

Redox-Active Ruthenium-Organic Polyhedra with Tunable Surface Functionality and Porosities.

Dinuclear ruthenium paddlewheel complexes exhibit high structural stability in redox reactions. The use of these chemical motifs for the construction of Ru-based metal-organic polyhedra (RuMOPs) provides a route for redox-active porous materials. However, there are few studies on the synthesis and characterization of RuMOPs due to the difficulty in controlling the assembly process via the ligand-exchange reaction of equatorial acetates of the diruthenium tetraacetate precursors with dicarboxylic acid ligands. In this study, we synthesized three novel cuboctahedral RuMOPs based on the Ru2(II/III)-paddlewheel units with different alkyl functionalizations on the benzene-1,3-dicarboxylate moieties. We evaluated the effect of external functionalization on the molecular packing and the porous and redox properties. The electrochemical measurements revealed the multielectron transferred redox process where the electron-donating/-withdrawing nature of the functional groups allows the control of the redox behavior.

LAP: Liability Antibody Profiler by sequence & structural mapping of natural and therapeutic antibodies.

Antibody-based therapeutics must not undergo chemical modifications that would impair their efficacy or hinder their developability. A commonly used technique to de-risk lead biotherapeutic candidates annotates chemical liability motifs on their sequence. By analyzing sequences from all major sources of data (therapeutics, patents, GenBank, literature, and next-generation sequencing outputs), we find that almost all antibodies contain an average of 3-4 such liability motifs in their paratopes, irrespective of the source dataset. This is in line with the common wisdom that liability motif annotation is over-predictive. Therefore, we have compiled three computational flags to prioritize liability motifs for removal from lead drug candidates: 1. germline, to reflect naturally occurring motifs, 2. therapeutic, reflecting chemical liability motifs found in therapeutic antibodies, and 3. surface, indicative of structural accessibility for chemical modification. We show that these flags annotate approximately 60% of liability motifs as benign, that is, the flagged liabilities have a smaller probability of undergoing degradation as benchmarked on two experimental datasets covering deamidation, isomerization, and oxidation. We combined the liability detection and flags into a tool called Liability Antibody Profiler (LAP), publicly available at lap.naturalantibody.com. We anticipate that LAP will save time and effort in de-risking therapeutic molecules.

Accurate, Uncertainty-Aware Classification of Molecular Chemical Motifs from Multimodal X-ray Absorption Spectroscopy.

Accurate classification of molecular chemical motifs from experimental measurement is an important problem in molecular physics, chemistry, and biology. In this work, we present neural network ensemble classifiers for predicting the presence (or lack thereof) of 41 different chemical motifs on small molecules from simulated C, N, and O K-edge X-ray absorption near-edge structure (XANES) spectra. Our classifiers not only achieve class-balanced accuracies of more than 0.95 but also accurately quantify uncertainty. We also show that including multiple XANES modalities improves predictions notably on average, demonstrating a "multimodal advantage" over any single modality. In addition to structure refinement, our approach can be generalized to broad applications with molecular design pipelines.

Comprehensive analysis of the aldehyde dehydrogenase gene family in Phaseolus vulgaris L. and their response to saline-alkali stress.

Aldehyde dehydrogenase (ALDH) scavenges toxic aldehyde molecules by catalyzing the oxidation of aldehydes to carboxylic acids. Although ALDH gene family members in various plants have been extensively studied and were found to regulate plant response to abiotic stress, reports on ALDH genes in the common bean (Phaseolus vulgaris L.) are limited. In this study, we aimed to investigate the effects of neutral (NS) and basic alkaline (AS) stresses on growth, physiological and biochemical indices, and ALDH activity, ALDH gene expression of common bean. In addition, We used bioinformatics techniques to analyze the physical and chemical properties, phylogenetic relationships, gene replication, collinearity, cis-acting elements, gene structure, motifs, and protein structural characteristics of PvALDH family members. We found that both NS and AS stresses weakened the photosynthetic performance of the leaves, induced oxidative stress, inhibited common bean growth, and enhanced the antioxidative system to scavenge reactive oxygen species. Furthermore, we our findings revealed that ALDH in the common bean actively responds to NS or AS stress by inducing the expression of PvALDH genes. In addition, using the established classification criteria and phylogenetic analysis, 27 PvALDHs were identified in the common bean genome, belonging to 10 ALDH families. The primary expansion mode of PvALDH genes was segmental duplication. Cis-acting elemental analysis showed that PvALDHs were associated with abiotic stress and phytohormonal responses. Gene expression analysis revealed that the PvALDH gene expression was tissue-specific. For instance, PvALDH3F1 and PvALDH3H1 were highly expressed in flower buds and flowers, respectively, whereas PvALDH3H2 and PvALDH2B4 were highly expressed in green mature pods and young pods, respectively. PvALDH22A1 and PvALDH11A2 were highly expressed in leaves and young trifoliates, respectively; PvALDH18B2 and PvALDH18B3 were highly expressed in stems and nodules, respectively; and PvALDH2C2 and PvALDH2C3 were highly expressed in the roots. PvALDHs expression in the roots responded positively to NS-AS stress, and PvALDH2C3, PvALDH5F1, and PvALDH10A1 were significantly (P < 0.05) upregulated in the roots. These results indicate that AS stress causes higher levels of oxidative damage than NS stress, resulting in weaker photosynthetic performance and more significant inhibition of common bean growth. The influence of PvALDHs potentially modulates abiotic stress response, particularly in the context of saline-alkali stress. These findings establish a basis for future research into the potential roles of ALDHs in the common bean.

Genome-Wide Identification and Expression Analysis of Auxin Response Factor (ARF) Gene Family in Betula pendula

As the key transcription factors regulating auxin responsive genes expression, auxin response factors (ARFs) play critical roles in diverse aspects of plant growth and development. Betula pendula is a valuable ornamental tree, and the information on ARF gene family of B. pendula is needed for better understanding. The publication of the genome sequence of B. pendula enable to analyze the bioinformatics information and expression pattern of BpeARF gene family on the genome-wide basis. In this study, physical and chemical properties, chromosome location, phylogenetic relationship, gene structure, conserved domain, motif composition, and cis-acting element of BpeARF gene family were analyzed, and expression patterns of BpeARF genes were investigated using completely random design in different tissues and under exogenous NAA and drought treatments. A total of 17 BpeARF genes was identified from B. pendula genome, which were unevenly distributed on 13 chromosomes and encoded adequate proteins ranging from 613 to 1135 amino acids in length. Three BpeARF gene pairs were formed by segmental duplication, and the Ka/Ks values of these BpeARF gene pairs were less than 1. According to the phylogenetic relationship among B. pendula, Betula platyphylla, Populus trichocarpa, and Arabidopsis thaliana, the BpeARF genes were divided into four classes, and the intron/exon structure, conserved domain, and motif composition showed high similarity among the BpeARF genes within the same class. The cis-acting elements in the promoter regions of BpeARF genes were related to tissue development, hormone response, and stress resistance. Quantitative real-time PCR exhibited diverse expression patterns of BpeARF genes in different tissues and in response to exogenous auxin treatment and drought stress. The expressions of one, ten, seven, and three BpeARF genes were the high levels in buds, young leaves, stems, and roots, respectively. Under exogenous NAA treatment, six BpeARF genes in stems and roots were upregulated expression at all timepoints. Under drought stress, BpeARF7 and BpeARF15 were upregulated in stems and roots, and BpeARF5 and BpeARF6 were downregulated in leaves, stems, and roots. Our results provided valuable information for the classification and putative functions of BpeARF gene family, which may be helpful for selecting candidate genes and verifying gene function in the genetic engineering of birch trees in further research.

Ortho-Boronic Acid Carbonyl Compounds and Their Applications in Chemical Biology.

Iminoboronates and diazaborines are related classes of compounds that feature an imine ortho to an arylboronic acid (iminoboronate) or a hydrazone that cyclizes with an ortho arylboronic acid (diazaborine). Rather than acting as independent chemical motifs, the arylboronic acid impacts the rate of imine/hydrazone formation, hydrolysis, and exchange with competing nucleophiles. Increasing evidence has shown that the imine/hydrazone functionality also impacts arylboronic acid reactivity toward diols and reactive oxygen and nitrogen species (ROS/RNS). Untangling the communication between C=N linked functionalities and arylboronic acids has revealed a powerful and tunable motif for bioconjugation chemistries and other applications in chemical biology. Here, we survey the applications of iminoboronates and diazaborines in these fields with an eye toward understanding their utility as a function of neighboring group effects.