Preparation and investigation of two-component silica-modified hydrophobic layer for minimizing retention loss of reversed-phase chromatographic columns using fully aqueous mobile phases.

Chromatographers often employ fully aqueous mobile phases to retain highly polar compounds in reversed-phase liquid chromatography (RPLC). However, when the flow rate is interrupted, either accidentally or intentionally, a substantial loss in retention occurs due to the spontaneous dewetting of water from the hydrophobic surface of conventional RPLC-C18 particles. Previous studies have shown that maintaining a low C18 surface coverage (approximately 1.5 µmol/m2) can mitigate water dewetting by increasing chain disorder, facilitating the intercalation of water clusters between the C18-bonded chains, and keeping the mesopores wetted. In this research, we explore the potential and additional benefits of using two-component surface bonding materials (C8/C18 and PhenylHexyl (PhHx)/C18) at a constant and low total surface coverage of 1.51 ± 0.15 µmol/m2. We synthesized seven one- and two-component modified silica particles with a volume average particle size of 5.22 µm and an average mesopore size of 104 Å. The surface coverage was increased from 0 to 0.54, 1.00, and to 1.66 µmol2 for C8 chains and from 0 to 0.52, 0.70, and to 1.65 µmol2 for PhHx ligands. To prevent interactions between water and any unreacted silanols, all seven derivatized particles were heavily endcapped with trimethylsilane (TMS) reagent. The fraction of the surface area remaining in contact with water was determined by measuring the retention times of weakly (thiourea) and strongly (thymine) retained compounds at intervals of 1, 2, 4, 8, 16, 32, and 64 minutes following the cessation of flow. Two distinct column temperatures, 24°C and 60°C, were employed in the experiments. Retention losses were found to be minimized in the presence of a small quantity of C8 chains (less than 40% of the total surface coverage). Additionally, it is essential to consider substantial fractions of PhHx chains, as long as the presence of the PhHx ligand does not significantly impact retention and selectivity. Combining mixed RPLC bondings with a low total surface coverage of approximately 1.5 µmol/m2 emerges as a viable solution for further minimizing retention loss in standard C18-bonded RPLC columns, particularly within the surface coverage range of 2.5-3.0 µmol/m2.

Therapeutically targeting type I interferon directly to XCR1+ dendritic cells reveals the role of cDC1s in anti-drug antibodies.

Conventional type 1 dendritic cells (cDC1s) are superior in antigen cross-presentation and priming CD8+ T cell anti-tumor immunity and thus, are a target of high interest for cancer immunotherapy. Type I interferon (IFN) is a potent inducer of antigen cross-presentation, but, unfortunately, shows only modest results in the clinic given the short half-life and high toxicity of current type I IFN therapies, which limit IFN exposure in the tumor. CD8+ T cell immunity is dependent on IFN signaling in cDC1s and preclinical studies suggest targeting IFN directly to cDC1s may be sufficient to drive anti-tumor immunity. Here, we engineered an anti-XCR1 antibody (Ab) and IFN mutein (IFNmut) fusion protein (XCR1Ab-IFNmut) to determine whether systemic delivery could drive selective and sustained type I IFN signaling in cDC1s leading to anti-tumor activity and, in parallel, reduced systemic toxicity. We found that the XCR1Ab-IFNmut fusion specifically enhanced cDC1 activation in the tumor and spleen compared to an untargeted control IFN. However, multiple treatments with the XCR1Ab-IFNmut fusion resulted in robust anti-drug antibodies (ADA) and loss of drug exposure. Using other cDC1-targeting Ab-IFNmut fusions, we found that localizing IFN directly to cDC1s activates their ability to promote ADA responses, regardless of the cDC1 targeting antigen. The development of ADA remains a major hurdle in immunotherapy drug development and the cellular and molecular mechanisms governing the development of ADA responses in humans is not well understood. Our results reveal a role of cDC1s in ADA generation and highlight the potential ADA challenges with targeting immunostimulatory agents to this cellular compartment.

Characterization of a highly stable zwitterionic hydrophilic interaction chromatography stationary phase based on hybrid organic-inorganic particles.

We have characterized a sulfobetaine stationary phase based on 1.7 µm ethylene-bridged hybrid organic-inorganic particles, which is intended for use in hydrophilic interaction chromatography. The efficiency of a column packed with this material was determined as a function of flow rate, demonstrating a minimum reduced plate height of 2.4. The batch-to-batch reproducibility was assessed using the separation of a mixture of acids, bases, and neutrals. We compared the retention and selectivity of the hybrid sulfobetaine stationary phase to that of several benchmark materials. The hybrid sulfobetaine material gave strong retention for polar neutrals and high selectivity for methyl groups, hydroxy groups, and configurational isomers. Large differences in cation and anion retention were observed among the columns. We characterized the acid and base stability of the hybrid sulfobetaine stationary phase, using accelerated tests at pH 1.3 and 11.0, both at 70°C. The results support a recommended pH range of 2-10. We also investigated the performance of columns packed with this material for metal-sensitive analytes, comparing conventional stainless steel column hardware to hardware that incorporates hybrid surface technology to mitigate interactions with metal surfaces. Compared to the conventional columns, the hybrid surface technology columns showed a greatly improved peak shape.

Characterization of a highly stable mixed-mode reversed-phase/weak anion-exchange stationary phase based on hybrid organic/inorganic particles.

We have characterized Atlantis ethylene-bridged hybrid C18 anion-exchange, a mixed-mode reversed-phase/weak anion-exchange stationary phase designed to give greater retention for anions (e.g., ionized acids) compared to conventional reversed-phase materials. The retention and selectivity of this stationary phase were compared to that of three benchmark materials, using a mixture of six polar compounds that includes an acid, two bases, and three neutrals. The compatibility of the ethylene-bridged hybrid C18 anion-exchange material with 100% aqueous mobile phases was also evaluated. We investigated the batch-to-batch reproducibility of the ethylene-bridged hybrid C18 anion-exchange stationary phase for 27 batches across three different particle sizes (1.7, 2.5, and 5 µm) and found it to be comparable to that of one of the most reproducible C18 stationary phases. We also characterized the acid and base stability of the ethylene-bridged hybrid C18 anion-exchange stationary phase and the results show it to be usable over a wide pH range, from 2 to 10. The extended upper pH limit relative to silica-based reversed-phase/weak anion-exchange materials is enabled by the use of ethylene-bridged hybrid organic/inorganic particles. The improved base stability allows Atlantis ethylene-bridged hybrid C18 anion-exchange to be used with a wider range of mobile phase pH values, opening up a greater range of selectivity options.

Any unique image biomarkers associated with COVID-19?

OBJECTIVE: To define the uniqueness of chest CT infiltrative features associated with COVID-19 image characteristics as potential diagnostic biomarkers. METHODS: We retrospectively collected chest CT exams including n = 498 on 151 unique patients RT-PCR positive for COVID-19 and n = 497 unique patients with community-acquired pneumonia (CAP). Both COVID-19 and CAP image sets were partitioned into three groups for training, validation, and testing respectively. In an attempt to discriminate COVID-19 from CAP, we developed several classifiers based on three-dimensional (3D) convolutional neural networks (CNNs). We also asked two experienced radiologists to visually interpret the testing set and discriminate COVID-19 from CAP. The classification performance of the computer algorithms and the radiologists was assessed using the receiver operating characteristic (ROC) analysis, and the nonparametric approaches with multiplicity adjustments when necessary. RESULTS: One of the considered models showed non-trivial, but moderate diagnostic ability overall (AUC of 0.70 with 99% CI 0.56-0.85). This model allowed for the identification of 8-50% of CAP patients with only 2% of COVID-19 patients. CONCLUSIONS: Professional or automated interpretation of CT exams has a moderately low ability to distinguish between COVID-19 and CAP cases. However, the automated image analysis is promising for targeted decision-making due to being able to accurately identify a sizable subsect of non-COVID-19 cases. KEY POINTS: • Both human experts and artificial intelligent models were used to classify the CT scans. • ROC analysis and the nonparametric approaches were used to analyze the performance of the radiologists and computer algorithms. • Unique image features or patterns may not exist for reliably distinguishing all COVID-19 from CAP; however, there may be imaging markers that can identify a sizable subset of non-COVID-19 cases.

Synthesis of Bioactive Side-Chain Analogues of TAN-2483B.

The fungal metabolite TAN-2483B has a 2,6-trans-relationship across the pyran ring of its furo[3,4-b]pyran-5-one core, which has thwarted previous attempts at its synthesis. We have now developed a chiral pool approach to this core and prepared side-chain analogues of TAN-2483B. The synthesis relies on ring expansion of a reactive furan ring-fused dibromocyclopropane and alkynylation of the resulting pyran. The furan ring is constructed by palladium-catalysed carbonylative lactonisation. Various side-chains are appended through Wittig-type chemistry. The prepared analogues showed micromolar activity towards cancer cell lines HL-60, 1A9 and MCF-7 and certain human disease-relevant kinases, including Bruton's tyrosine kinase (Btk).

Synthesis and Microtubule-Destabilizing Activity of N-Cyclopropyl-4-((3,4-dihydroquinolin-1(2H)-yl)sulfonyl)benzamide and its Analogs.

While clinically useful, microtubule-targeting agents are limited by factors that include their susceptibility to multidrug resistance. A series of aryl sulfonamides, terminally substituted with an amide or carboxylic acid, was synthesized and assayed for biological activity in two human cancer cell lines. The resulting antiproliferative activity data demonstrated that an amide was superior to a carboxylic acid in the para position. The most potent compound (3) had an IC50 for growth inhibition in the low micromolar range, caused cells to accumulate in G2 M of the cell cycle, and led to depolymerization of microtubules. It was also not susceptible to the P-glycoprotein drug efflux pump that underpins the resistance of cells to long-term drug treatment schedules.

Peloruside E (22-Norpeloruside A), a Pelorusane Macrolide from the New Zealand Marine Sponge Mycale hentscheli, Retains Microtubule-Stabilizing Properties.

A new peloruside congener, peloruside E (5), has been isolated in sub-milligram quantities from a specimen of the New Zealand marine sponge Mycale hentscheli. The structure of 5 differs from the parent compound peloruside A (1) by replacement of the C-10 gem-dimethyl moiety with a monomethyl substituent and represents the first structural deviation in the pelorusane scaffold. Peloruside E (5) is potently antiproliferative (HL-60, IC50 90 nM, cf. 1, 19 nM) and polymerizes purified tubulin, albeit at a rate lower than that of 1.

Divided disasters: examining the impacts of the conflict-disaster nexus for distanced crises in the Philippines.

'Divided disasters' are conflicts and natural hazard-induced disasters that occur simultaneously, but in different locations within the same national boundaries. They will place pressure on the same national governance structures, will draw on the same international and national humanitarian resources, and therefore can mutually reinforce the challenges and risks faced by affected populations. Yet, as this paper argues, the impacts do not originate in the direct interaction of these two variables. Rather, they derive, in part, from the management of humanitarian responses to them-namely, through the reprioritisation of attention and the redeployment of resources as driven by the imperatives of 'the good project'. Using a case study of the Philippines, and the parallel emergencies of Typhoon Haiyan (one of the strongest tropical cyclones on record) and the spike in violence in Mindanao in 2013, this paper explores the organisational motivators of humanitarian responses to divided disasters, and assesses their implications for affected populations.

Marine Invertebrate Natural Products that Target Microtubules.

Marine natural products as secondary metabolites are a potential major source of new drugs for treating disease. In some cases, cytotoxic marine metabolites target the microtubules of the eukaryote cytoskeleton for reasons that will be discussed. This review covers the microtubule-targeting agents reported from sponges, corals, tunicates, and molluscs and the evidence that many of these secondary metabolites are produced by bacterial symbionts. The review finishes by discussing the directions for future development and production of clinically relevant amounts of these natural products and their analogues through aquaculture, chemical synthesis, and biosynthesis by bacterial symbionts.

Zampanolide Binding to Tubulin Indicates Cross-Talk of Taxane Site with Colchicine and Nucleotide Sites.

The marine natural product zampanolide and analogues thereof constitute a new chemotype of taxoid site microtubule-stabilizing agents with a covalent mechanism of action. Zampanolide-ligated tubulin has the switch-activation loop (M-loop) in the assembly prone form and, thus, represents an assembly activated state of the protein. In this study, we have characterized the biochemical properties of the covalently modified, activated tubulin dimer, and we have determined the effect of zampanolide on tubulin association and the binding of tubulin ligands at other binding sites. Tubulin activation by zampanolide does not affect its longitudinal oligomerization but does alter its lateral association properties. The covalent binding of zampanolide to ß-tubulin affects both the colchicine site, causing a change of the quantum yield of the bound ligand, and the exchangeable nucleotide binding site, reducing the affinity for the nucleotide. While these global effects do not change the binding affinity of 2-methoxy-5-(2,3,4-trimethoxyphenyl)-2,4,6-cycloheptatrien-1-one (MTC) (a reversible binder of the colchicine site), the binding affinity of a fluorescent analogue of GTP (Mant-GTP) at the nucleotide E-site is reduced from 12 ± 2 × 105 M-1 in the case of unmodified tubulin to 1.4 ± 0.3 × 105 M-1 in the case of the zampanolide tubulin adduct, indicating signal transmission between the taxane site and the colchicine and nucleotide sites of ß-tubulin.

Zampanolide, a Microtubule-Stabilizing Agent, Is Active in Resistant Cancer Cells and Inhibits Cell Migration.

Zampanolide, first discovered in a sponge extract in 1996 and later identified as a microtubule-stabilizing agent in 2009, is a covalent binding secondary metabolite with potent, low nanomolar activity in mammalian cells. Zampanolide was not susceptible to single amino acid mutations at the taxoid site of ß-tubulin in human ovarian cancer 1A9 cells, despite evidence that it selectively binds to the taxoid site. As expected, it did not synergize with other taxoid site microtubule-stabilizing agents (paclitaxel, ixabepilone, discodermolide), but surprisingly also did not synergize in 1A9 cells with laulimalide/peloruside binding site agents either. Efforts to generate a zampanolide-resistant cell line were unsuccessful. Using a standard wound scratch assay in cell culture, it was an effective inhibitor of migration of human umbilical vein endothelial cells (HUVEC) and fibroblast cells (D551). These properties of covalent binding, the ability to inhibit cell growth in paclitaxel and epothilone resistant cells, and the ability to inhibit cell migration suggest that it would be of interest to investigate zampanolide in preclinical animal models to determine if it is effective in vivo at preventing tumor growth and metastasis.

Synthesis of a simplified triazole analogue of pateamine A.

Pateamine A is a naturally occurring metabolite extracted from the marine sponge Mycale hentscheli. It exhibits potent cytotoxicity towards cancer cell lines and has been shown to target protein translation initiation via inhibition of the function of eukaryotic initiation factor 4A proteins. We have synthesised a simplified analogue of pateamine A, consisting of the skeletal core of the natural product but with the thiazole heterocycle replaced by a triazole. The convergent design of the synthesis features a base-induced opening of a δ-valerolactone to access the Z,E-dienoate moiety, Julia-Kocienski olefination and copper-catalysed azide-alkyne cycloaddition. Bioactivity testing of the simplified pateamine A analogue (3) indicated a significant reduction in cytotoxicity, compared to natural pateamine A. We propose that this reduced activity is due mainly to the substitution of the thiazole for the triazole heterocycle. This supports the hypothesis that the thiazole of pateamine A is important for binding to its biological target.

Microtubule-stabilizing properties of the avocado-derived toxins (+)-(R)-persin and (+)-(R)-tetrahydropersin in cancer cells and activity of related synthetic analogs.

The avocado toxin (+)-R-persin (persin) is active at low micromolar concentrations against breast cancer cells and synergizes with the estrogen receptor modulator 4-hydroxytamoxifen. Previous studies in the estrogen receptor-positive breast cancer cell line MCF-7 indicate that persin acts as a microtubule-stabilizing agent. In the present study, we further characterize the properties of persin and several new synthetic analogues in human ovarian cancer cells. Persin and tetrahydropersin cause G2M cell cycle arrest and increase intracellular microtubule polymerization. One analog (4-nitrophenyl)-deshydroxypersin prevents cell proliferation and blocks cells in G1 of the cell cycle rather than G2M, suggesting an additional mode of action of these compounds independent of microtubules. Persin can synergize with other microtubule-stabilizing agents, and is active against cancer cells that overexpress the P-glycoprotein drug efflux pump. Evidence from Flutax-1 competition experiments suggests that while the persin binding site on ß-tubulin overlaps the classical taxoid site where paclitaxel and epothilone bind, persin retains activity in cell lines with single amino acid mutations that affect these other taxoid site ligands. This implies the existence of a unique binding location for persin at the taxoid site.

Polyhalogenated Indoles from the Red Alga Rhodophyllis membranacea: The First Isolation of Bromo-Chloro-Iodo Secondary Metabolites.

An unusual tetrahalogenated indole with the exceptionally rare inclusion of the three halogens bromine, chlorine, and iodine was found using mass spectrometry within a fraction of a semipurified extract obtained from the red alga Rhodophyllis membranacea. We report herein the isolation and structure elucidation, using a combination of NMR spectroscopy and mass spectrometry, of 11 new tetrahalogenated indoles (1-11), including four bromochloroiodoindoles (5-7, 10). Several were evaluated for cytotoxic and antifungal activities against the HL-60 promyelocytic cell line and Saccharomyces cerevisiae, respectively.

ßI-tubulin mutations in the laulimalide/peloruside binding site mediate drug sensitivity by altering drug-tubulin interactions and microtubule stability.

Peloruside A (PLA) and laulimalide (LAU) are potent microtubule-stabilizing natural products that are effective against a broad spectrum of cancer cells. The interactions of PLA and LAU with tubulin have attracted a great deal of attention, mainly because they bind to ß-tubulin at a site that is different from the classical taxoid site. Multiple ßI-tubulin amino acid residues have been predicted by computer modelling studies and more recently by protein crystallography to participate in the binding of PLA and LAU to tubulin. The relevance of these residues in determining cellular sensitivity to the compounds, however, remains largely uncertain. To determine the role of four binding site residues, Q291, D295, V333, and N337 on PLA and LAU activity, we introduced single mutations to these sites by site-directed mutagenesis and transfected each mutant tubulin separately into HEK and/or HeLa cells. We found that a Q291M ßI-tubulin mutation increased sensitivity of the cells to PLA, but not to LAU, paclitaxel (PTX), or vinblastine (VBL). In contrast, V333W and N337L mutations led to less stable microtubules, with the V333W causing resistance to PLA and PTX, but not LAU, and the N337L causing resistance to PLA, LAU, and PTX. Moreover, cells expressing either W333 or L337 were hypersensitive to the microtubule-destabilizing agent, VBL. The D295I mutation conferred resistance to both PLA and LAU without affecting microtubule stability or sensitivity to PTX or ixabepilone (IXB). This study identifies the first mammalian ßI-tubulin mutation that specifically increases sensitivity to PLA, and reports mutations at PLA and LAU binding site residues that can either reduce microtubule stability or impair drug-tubulin binding, conferring resistance to these microtubule-stabilizing agents. This information provides insights on ß-tubulin residues important for maintaining microtubule structural integrity and for sensitivity to microtubule-targeting agents, and suggests novel directions for rational structure-based design of new and more potent agents for cancer treatment that target the LAU/PLA site.

Synthesis of mycothiol conjugate analogues and evaluation of their antimycobacterial activity.

Drug-resistant Mycobacterium tuberculosis is a growing health problem. As proof of principle that the bacterial-specific metabolite mycothiol could be used as a delivery agent for antimycobacterial agents, simplified analogues of mycothiol were synthesised containing an S-trichloroethenyl substituted cysteine residue. It was envisaged that uptake of the mycothiol analogue would be followed by release of the known cytotoxin S-trichloroethenyl cysteine by the action of mycothiol S-conjugate amidase or its paralog, mycothiol deacetylase MshB. Promising activity was displayed against model Mycobacteria, although further development will be required to improve selectivity.

The Nitrogenous Hamigerans: Unusual Amino Acid-Derivatized Aromatic Diterpenoid Metabolites from the New Zealand Marine Sponge Hamigera tarangaensis.

The NMR-directed isolation and structure elucidation of nine new nitrogenous hamigeran diterpenoids from the New Zealand marine sponge Hamigera tarangaensis are described. Featured in this set are the oxazole-containing hamigeran M (4) and eight compounds (5a-6a and 7a-8c) related to the constitutional structure of hamigeran D (1). Moderate cytotoxicity in the low-micromolar range against the HL-60 promyeloid leukemic cell line is reported for seven of the new compounds. The structural nature of these compounds suggests that their adducts are derived from an amino acid source and has allowed for revision of the configuration about C-18 of the archetypal compound, hamigeran D, from 1a to 1b. The existence of three constitutionally identical forms of hamigeran Q (8a-8c) requires the involvement of an allo-isoleucine stereoisomer and suggests the intriguing possibility of partial prokaryotic biogenesis of these unusual secondary metabolites.

Tuning the selectivity of Gd3N cluster endohedral metallofullerene reactions with Lewis acids.

We demonstrate the manipulation of the Lewis acid strength to selectively fractionate different types of Gd3N metallofullerenes that are present in complex mixtures. Carbon disulfide is used for all Lewis acid studies. CaCl2 exhibits the lowest reactivity but the highest selectivity by precipitating only those gadolinium metallofullerenes with the lowest first oxidation potentials. ZnCl2 selectively complexes Gd3N@C88 during the first 4 h of reaction. Reaction with ZnCl2 for an additional 7 days permits a selective precipitation of Gd3N@C84 as the dominant endohedral isolated. A third fraction is the filtrate, which possesses Gd3N@C86 and Gd3N@C80 as the two dominant metallofullerenes. The order of increasing reactivity and decreasing selectivity (left to right) is as follows: CaCl2 < ZnCl2 < NiCl2 < MgCl2 < MnCl2 < CuCl2 < WCl4 ≪ WCl6 < ZrCl4 < AlCl3 < FeCl3. As a group, CaCl2, ZnCl2, and NiCl2 are the weakest Lewis acids and have the highest selectivity because of their very low precipitation onsets, which are below +0.19 V (i.e., endohedrals with first oxidation potentials below +0.19 V are precipitated). For CaCl2, the precipitation threshold is estimated at a remarkably low value of +0.06 V. Because most endohedrals possess first oxidation potentials significantly higher than +0.06 V, CaCl2 is especially useful in its ability to precipitate only a select group of gadolinium metallofullerenes. The Lewis acids of intermediate reactivity (i.e., precipitation onsets estimated between +0.19 and +0.4 V) are MgCl2, MnCl2, CuCl2, and WCl4. The strongest Lewis acids (WCl6, ZrCl4, AlCl3, and FeCl3) are the least selective and tend to precipitate the entire family of gadolinium metallofullerenes. Tuning the Lewis acid for a specific type of endohedral should be useful in a nonchromatographic purification method. The ability to control which metallofullerenes are permitted to precipitate and which endohedrals would remain in solution is a key outcome of this work.