Dibenzothiophene Sulfone Derivatives as Plasma Membrane Dyes

Dibenzothiophene 5,5-dioxide (DBTOO) derivatives have recently been shown to processes utility as fluorescent cell dyes. In an effort to extend the functionality of DBTOO-based dyes to include the visualization of cellular membranes, two lipophilic DBTOO were synthesized and their ability to incorporate into the plasma membrane of HeLa cells was examined by fluorescent microscopy. The photophysical properties of the two new DBTOO derivatives were determined and both have good fluorescent quantum yields and a visible blue emission. Due to agreeable wavelengths of excitation and emission, a standard 4′,6-diamindino-2-phenylindole (DAPI) filter set worked well with these dyes. After co-staining, it was confirmed that both DBTOO dyes localized in the plasma membrane. The quality of the overlap was quantified using Pearson correlation coefficient, which indicated a strong overlap between the DBTOO dyes and the standard plasma membrane dye. The novel dyes also displayed relatively low toxicity to the HeLa cells with IC₅₀ between 10 and 100 µm . Thus, this work reports a new use of DBTOO derivatives as fluorescent microscopy stains.     

Biosynthesis of the N–N-Bond-Containing Compound l-Alanosine

The formation of a N−N bond is a unique biochemical transformation, and nature employs diverse biosynthetic strategies to activate nitrogen for bond formation. Among molecules that contain a N−N bond, biosynthetic routes to diazeniumdiolates remain enigmatic. We here report the biosynthetic pathway for the diazeniumdiolate-containing amino acid l -alanosine. Our work reveals that the two nitrogen atoms in the diazeniumdiolate of l -alanosine arise from glutamic acid and aspartic acid, and we clarify the early steps of the biosynthetic pathway by using both in vitro and in vivo approaches. Our work demonstrates a peptidyl-carrier-protein-based mechanism for activation of the precursor l -diaminopropionate, and we also show that nitric oxide can participate in non-enzymatic diazeniumdiolate formation. Furthermore, we demonstrate that the gene alnA, which encodes a fusion protein with an N-terminal cupin domain and a C-terminal AraC-like DNA-binding domain, is required for alanosine biosynthesis.     

Gas-phase reactions of CF2 with O(3P) to produce COF: Their significance in plasma processing

Reactions between CF₂ and O(³P) have been studied at 295 K in a gas flow reactor sampled by a mass spectrometer. The major reaction for CF₂ has been found to be $$CF_2 + O \to COF + F$$ with $$CF_2 + O \to CO + 2F(F_2 )$$ more than a factor of three slower. The rate coefficient for all loss processes for CF₂ on reaction with O is (1.8±0.4)×10^?11 cm³ s^?1. The COF produced in (18) undergoes a fast reaction with O to produce predominantly CO₂. $$COF + O \to CO_2 + F$$ It is uncertain from the results whether or not $$COF + O \to CO + FO$$ occurs, but in any event (19) is the major route. The rate coefficient for the loss of COF in this system [i.e., the combined rate coefficients for (19) and (20)] is (9.3±2.1)×10^?11 cm³ s^?1. Stable product analysis reveals that for each CF₂ radical consumed, the following distribution of stable products is obtained: COF₂ (0.04±0.02), CO (0.21±0.04), and CO₂ (0.75±0.05). Thus COF₂, which we assume is produced via $$CF_2 + O \xrightarrow{M} COF_2$$ is a very minor product in this reaction sequence. The measured rate coefficients demonstrate that reactions (18) and (19) are important sources of F atoms in CF₄/O₂ plasmas.     

Combination collectors in adsorption colloid flotation for multielement determination in waters by neutron activation

A method is described for the collection of small amounts of both anions and cations in water samples by adsorption colloid flotation with a combination collector, prior to quantitation by neutron activation. In the presence of 20 mg of iron(III) and 2 ml of 0.1 M ammonium pyrrolidinedithiocarbamate, As(V), Cd(II), Co(II), Cu(II), Hg(II), Mo(VI), Sn(IV), Sb(III), Te(VI), Ti(IV), U(VI), V(V) and W(VI) are quantitatively collected from 1 -l samples at a pH 5.8 ± 0.1; sodium dodecyl sulfate and sodium oleate are used as surfactant. Recoveries for all the elements tested are greater than 90%. Results for a number of elements in sea waer and an NBS water standard, SRM 1643a, are given.     

Use of Mass Spectrometry in the Characterization of Polymers Emphasizing Metal-Containing Condensation Polymers

Suitable structure characterization is assisted through the use of mass spectrometry. Polymer fragmentation can be achieved in many ways including application of heat and ionizing radiation. MALDI MS allows routine analysis of polymers allowing identification of several repeat units. Graphite as a matrix allows higher mass ions to be created with less interfering ion fragments formed in comparison to more utilized matrix materials.     

The use of Mosher derivatives for the determination of the absolute configuration of substituted isoxazolidines

Isoxazolidines serve as intermediates in the synthesis of natural products. In addition, they can display significant biological activity, much of which derives from their ability to act as nucleoside analogues. As a result, considerable effort has been applied toward the asymmetric synthesis of isoxazolidines. However, a rapid and straightforward method for determination of the absolute configuration of isoxazolidines has not yet been reported. Herein we report the application of Mosher derivatives for the determination of the absolute configuration of substituted isoxazolidines. The Mosher derivatives exhibit conformational behavior similar to the Mosher derivatives of cyclic secondary amines. Interpretation of the chemical shift anisotropy, with these conformational biases in mind, can be used for the assignment of the absolute configuration of substituted isoxazolidines.     

Hyperpolarization of Pyridyl Fentalogues by Signal Amplification By Reversible Exchange (SABRE)

Fentanyl, also known as ‘jackpot’, is a synthetic opiate that is 50–100 times more potent than morphine. Clandestine laboratories produce analogues of fentanyl, known as fentalogues to circumvent legislation regarding its production. Three pyridyl fentalogues were synthesized and then hyperpolarized by signal amplification by reversible exchange (SABRE) to appraise the forensic potential of the technique. A maximum enhancement of -168-fold at 1.4 T was recorded for the ortho pyridyl ¹H nuclei. Studies of the activation parameters for the three fentalogues revealed that the ratio of ligand loss trans to hydride and hydride loss in the complex [Ir(IMes)(L)₃(H)₂]⁺ (IMes=1,3-bis(2,4,6-trimethylphenyl)imidazole-2-ylidene) ranged from 0.52 to 1.83. The fentalogue possessing the ratio closest to unity produced the largest enhancement subsequent to performing SABRE at earth's magnetic field. It was possible to hyperpolarize a pyridyl fentalogue selectively from a matrix that consisted largely of heroin (97 : 3 heroin:fentalogue) to validate the use of SABRE as a forensic tool.     

Role of self‐assembly conditions and amphiphilic balance on nanoparticle formation of PEG‐PDLLA copolymers in aqueous environments

The production of well‐defined and reproducible polymeric nanoparticles (NPs), in terms of size and stability in biological environments, is undoubtedly a fundamental challenge in the formulation of novel and more effective nanomedicines. The adoption of PEGylated lactide (LA) block copolymers as biodegradable and biocompatible nanocarriers at different clinical stages has rendered these materials an attractive polymeric platform to be exploited and their formulation is further understood. In the present work, we synthesized a library of linear polyethylene glycol‐poly(D,L‐lactide) block copolymers with different lengths of LA (15, 25, 50, and 100 LA units) via simple and metal‐free ring‐opening polymerization, in order to alter the amphiphilic balance of the different macromolecules. The produced polymers were formulated into NPs while varying a series of key parameters in the solvent displacement process, including solvent:nonsolvent ratios and the nature of the two media, and the effect on size and stability was assessed. In addition, stability to protein–NPs interaction and aggregation was studied, highlighting the different NP final properties according to the nature of the amphiphilic balance and nanoformulation conditions. Therefore, we have illustrated a systematic and methodological process to optimize a series of NPs parameters balancing particle size, size distribution, surface charge, and stability to guide future works in the nanoformulation field. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1801–1810     

Organocatalytic strategy for hydrophenolation of gem-difluoroalkenes

Gem-difluoroalkenes are an easily accessed fluorinated functional group, and a useful intermediate for elaborating into more complex fluorinated compounds. Currently, most functionalization reactions of gem-difluoroalkenes, with or without a transition metal-based catalyst system, involve the addition or removal of a fluorine atom to generate trifluorinated or monofluorinated products, respectively. In contrast, we present a complementary “fluorine-retentive” reaction that exploits an organocatalytic strategy to add phenols across gem-difluoroalkenes to deliver β,β-difluorophenethyl arylethers. The products are produced in good to moderate yields and selectivities, thus providing a range of compounds that are underrepresented in the synthetic and medicinal chemistry literature.     

Elimination of autofluorescence in fluorescence correlation spectroscopy using the AzaDiOxaTriAngulenium (ADOTA) fluorophore in combination with time-correlated single-photon counting (TCSPC)

Fluorescence correlation spectroscopy (FCS) is a frequently applied technique that allows for the precise and sensitive analysis of molecular diffusion and interactions. However, the potential of FCS for in vitro or ex vivo studies has not been fully realized due in part to artifacts originating from autofluorescence (fluorescence of inherent components and fixative-induced fluorescence). Here, we propose the azadioxatriangulenium (ADOTA) dye as a solution to this problem. The lifetime of the ADOTA probe, about 19.4 ns, is much longer than most components of autofluorescence. Thus, it can be easily separated by time-correlated single-photon counting methods. Here, we demonstrate the suppression of autofluorescence in FCS using ADOTA-labeled hyaluronan macromolecules (HAs) with Rhodamine 123 added to simulate diffusing fluorescent background components. The emission spectrum and decay rate of Rhodamine 123 overlap with the usual sources of autofluorescence, and its diffusion behavior is well known. We show that the contributions from Rhodamine 123 can be eliminated by time gating or by fluorescence lifetime correlation spectroscopy (FLCS). While the pairing of ADOTA and time gating is an effective strategy for the removal of autofluorescence from fluorescence imaging, the loss of photons leads to erroneous concentration values with FCS. On the other hand, FLCS eliminates autofluorescence without such errors. We then show that both time gating and FLCS may be used successfully with ADOTA-labeled HA to detect the presence of hyaluronidase, the overexpression of which has been observed in many types of cancer.