A new polymorph of tetraphenyldiboroxane

A new polymorph of tetraphenyldiboroxane [or oxybis(diphenylborane)], C₂₄H₂₀B₂O, (Ia), has been found. It is monoclinic, like the already known form, (Ib), and can be refined in the same space group, namely P2₁/c, or in the equivalent setting P2₁/n. The molecular conformations of the two polymorphs differ in the rotations of two of the phenyl rings about the B—C bonds, leading to markedly different packing patterns and cell dimensions.     

Encapsulation of Indomethacin in PVP: Solid-State NMR Studies

Summary: ¹³C solid-state NMR and ¹H relaxation time measurements have been used to determine the structure of the crystalline and amorphous forms of the pharmaceutical drug indomethacin. Cross-polarization dynamics parameters were calculated for individual NMR resonances providing an insight into the mobility of functional groups in two forms of indomethacin. The changes of mobility in indomethacin/polyvinylpyrrolidone (PVP) formulation have been investigated via¹H-¹³C solid-state NMR methods. Differences between the amorphous material and its crystalline counterpart have been observed. The γ-amorphous indomethacin rapidly crystallizes with time. It has been shown that encapsulation in the PVP stabilizes the amorphous form of the drug by preventing crystallization due to reduced mobility of the guest in the formulation.     

Sequence‐based separation of single‐stranded DNA at high salt concentrations in capillary zone electrophoresis

DNA separation by fragment length can be readily achieved using sieving gels in electrophoresis. Separation by sequence has not been as simple, generally requiring adequate differences in native or induced conformation between single or hybridized strands or differences in thermal or chemical stability of hybridized strands. Previously, it was shown that four single‐stranded DNA (ssDNA) 76‐mers that differ by only a few A‐G substitutions could be separated based solely on sequence by adding guanosine‐5’‐monophosphate to the running buffer in capillary zone electrophoresis (CZE). The separation was attributed to interactions of the ssDNA with self‐assembled guanine‐tetrad structures; however, subsequent studies of an expanded set of ten 76‐mers showed that the separation was a more general phenomenon that occurred at high salt concentrations. With the long‐term goal of using experimental and computational methods to provide insight into the basis of the separation, a set of ssDNA 15‐mers was designed including a poly(dT) 15‐mer and nine variants. Separations were performed using fluorescent‐labeled ssDNA in CZE with laser‐induced fluorescence detection. Results show that separation improves with increasing buffer concentration and decreasing temperature, due at least in part to longer separation times. Migration times increase with increasing purine content, with A having a much larger effect that G. Circular dichroism spectra of the mixtures of the strands suggest that the separation is not due to changes in conformation of the ssDNA at high salt concentrations.     

Stability and state of aggregation of aqueous fibrinogen and dipalmitoylphosphatidylcholine lipid vesicles

The stability and state of aggregation of aqueous fibrinogen (FB) and dipalmitoylphosphatidylcholine (DPPC) vesicles in water or buffer at 25 degrees C were studied with dynamic light scattering (DLS), UV-vis spectroturbidimetry (ST), and cryo-transmission electron microscopy (cryo-TEM). In water, when 1000 ppm (0.10 wt %) DPPC dispersions were prepared with a protocol including extensive sonication, they contained mostly vesicles and were quite clear, transparent, and stable for at least 30 days. FB mixtures with water (0.075 wt %) were quite unstable and biphasic. They formed large aggregates which eventually precipitated. The addition of DPPC vesicles into these unstable FB dispersions reversed FB aggregation and precipitation and produced stable translucent microdispersions. The inferred lipid/protein aggregates were limited in size, with average diameters ranging from 200 to 300 nm. In buffer, DPPC dispersions were also clear and quite stable, with average dispersed particles diameter of ca. 90 nm. FB dissolved in aqueous buffer and formed transparent and stable solutions. Adding salt to an aggregated FB dispersion in water reversed the aggregation. FB aggregated and redissolved in the presence of the citrate and after the citrate was removed. There was no effect of citrate (present in FB initially) in the FB aggregation or redissolution. FB molecules in buffer form dimers or higher aggregates. Their average aggregation number is 2, determined with Rayleigh scattering analysis of turbidity data. The average hydrodynamic diameter of FB solutions from DLS was 30 nm. Mixing a stable FB solution in buffer and a stable DPPC dispersion in buffer produced highly unstable mixtures, in which large aggregates precipitated. These results have implications in understanding the interactions of lipids and proteins in many biological applications and food processing applications.     

Determination of wavelength-specific UV protection factors of sunscreens in intact skin by EPR measurement of UV-induced reactive melanin radical

There remains an unmet need for skin tissue-based assays for the measurement of the UVA protection and efficacy of sunscreens. Here we describe development of a novel electron paramagnetic resonance assay that uses the photogeneration of reactive melanin radical as a measure of UV light penetration to melanocytes in situ in skin. We have used areas of focal melanocytic hyperplasia in the skin of Monodelphis domestica to model the human nevus. We show that we are able to use this assay to determine the monochromatic protection factors (mPF) of research and commercial sunscreens at specific narrow wavebands of UVB, UVA and blue visible light. Both commercial sunscreens, a sun protection factor (SPF) 4 and an SPF 30 product, had mPFs in the UVB range that correlated well with their claimed SPF. However, their mPF in the UVA ranges were only about one-third of claimed SPF. This technique can be used to design and assay sunscreens with optimally balanced UVA and UVB protection.     

A Single Methylene Group in Oligoalkylamine‐Based Cationic Polymers and Lipids Promotes Enhanced mRNA Delivery

The development of chemically modified mRNA holds great promise as a new class of biologic therapeutics. However, the intracellular delivery and endosomal escape of mRNA encapsulated in nanoparticles has not been systematically investigated. Here, we synthesized a diverse set of cationic polymers and lipids from a series of oligoalkylamines and subsequently characterized their mRNA delivery capability. Notably, a structure with an alternating alkyl chain length between amines showed the highest transfection efficiency, which was linked to a high buffering capacity in a narrow range of pH 6.2 to 6.5. Variation in only one methylene group resulted in enhanced mRNA delivery to both the murine liver as well as porcine lungs after systemic or aerosol administration, respectively. These findings reveal a novel fundamental structure–activity relationship for the delivery of mRNA that is independent of the class of mRNA carrier and define a promising new path of exploration in the field of mRNA therapeutics.     

Closo → nido cage degradation of 1-(substituted-phenyl)-1,2-dicarbadodecaborane(12)s in wet DMSO under neutral conditions

1-(2-Nitrophenyl)-1,2-dicarba-closo-dodecaborane(12) shows C-H?O intramolecular hydrogen bonding in chloroform. The reaction of isomeric 1-(nitrophenyl)-1,2-dicarba-closo-dodecaborane(12)s and of 1-(4-fluorophenyl)-1,2-dicarba-closo-dodecaborane(12) with wet DMSO causes the removal of 3-B or 6-B, leading cleanly to nido-carboranes. The rank order of rates of these deboronations is consistent with developing negative charge in the rate-determining step.     

Isolation of flavonoids from aspen knotwood by pressurized hot water extraction and comparison with other extraction techniques

Pressurized hot water extraction (PHWE) conditions (time, temperature, pressure) were optimized for the extraction of naringenin and other major flavonoids (dihydrokaempferol, naringin) from knotwood of aspen. Extracts were analysed by GC-FID, GC-MS, HPLC-UV and HPLC-MS. The results were compared with those obtained by Soxhlet, ultrasonic extraction and reflux in methanol. Flavonoids were most efficiently extracted with PHWE at 150 °C and 220 bar with 35 min extraction time. Soxhlet with methanol gave slightly higher recoveries, but an extraction time of 48 h was required. Naringenin concentration was highest in knotwood (1.15% dry weight) and much lower in the sapwood. PHWE proved to be cheap, fast and effective for the isolation of biofunctional flavonoids from aspen knotwood, producing higher recoveries than 24 h Soxhlet extraction, sonication or 24 h reflux.     

Multiplexing fibre optic near infrared (NIR) spectroscopy as an emerging technology to monitor industrial bioprocesses

The application of near infrared spectroscopy in bioprocessing has been limited by its dependence on calibrations derived from single bioreactor at a given time. Here, we propose a multiplexed calibration technique which allows calibrations to be built from multiple bioreactors run in parallel. This gives the flexibility to monitor multiple vessels and facilitates calibration model transfer between bioreactors. Models have been developed for the two key analytes: glucose and lactate using Chinese hamster ovary (CHO) cell lines and using analyte specific information obtained from the feasibility studies. We observe slight model degradation for the multiplexed models in comparison to the conventional (single probe) models, decrease in r² values from 89.4% to 88% for glucose whereas for lactate from 92% to 91.8% and a simultaneous increase in the number of factors as the model incorporates the inter-probe variability, nevertheless the models were fit for purpose. The results of this particular application of implementing multiplexed-NIRS to monitor multiple bioreactor vessels are very encouraging, as successful models have been built on-line and validated externally, which proffers the prospect of reducing timelines in monitoring the vessels considerably, and in turn, providing improved control.     

19F fast magic-angle spinning NMR studies of perfluoroalkanoic acid self-assembled monolayers

The bonding and dynamic properties of perfluoroalkanoic acid self-assembled monolayers (SAMs) on zirconia and titania powders were characterized by Fourier transform infrared and solid-state 19F magic-angle spinning NMR spectroscopy. The perfluoro fatty acids investigated included C(n)F(2n+1)CO2H, n = 7, 13, 15 and 17. The acids bind to both metal oxides via ionic carboxylate bonds, but complete monolayers are only formed on the zirconia. The shift of the CF3 group from -83 ppm in the bulk state to -85 ppm for the adsorbed monolayers is assigned to CF3 groups located at the air/monolayer interface. With the exception of the perfluorooctanoic acid, 19F spin lattice relaxation measurements indicate that the fluorocarbon chains of the adsorbed acids, even in the case of densely packed monolayers, are significantly more mobile than those in the bulk state. The motions associated with the enhanced mobility of the adsorbed acids are proposed to involve reorientations along the long chain axes. No evidence for chain melting in the fluorocarbon SAMs is found for temperatures well above the melting temperature of the bulk acids.