Surface Functionalization Methods to Enhance Bioconjugation in Metal-Labeled Polystyrene Particles

Lanthanide-encoded polystyrene particles synthesized by dispersion polymerization are excellent candidates for mass cytometry based immunoassays, however they have previously lacked the ability to conjugate biomolecules to the particle surface. We present here three approaches to post-functionalize these particles, enabling the covalent attachment of proteins. Our first approach used partially hydrolyzed poly(N-vinylpyrrolidone) as a dispersion polymerization stabilizer to synthesize particles with high concentration of -COOH groups on the particle surface. In an alternative strategy to provide -COOH functionality to the lanthanide-encoded particles, we employed seeded emulsion polymerization to graft poly(methacrylic acid) (PMAA) chains onto the surface of these particles. However, these two approaches gave little to no improvement in the extent of bioconjugation. In our third approach, seeded emulsion polymerization was subsequently used as a method to grow a functional polymer shell (in this case, poly(glycidyl methacrylate) (PGMA)) onto the surface of these particles, which proved highly successful. The epoxide-rich PGMA shell permitted extensive surface bioconjugation of NeutrAvidin, as probed by an Lu-labeled biotin reporter (ca. 7 × 10(5) binding events per particle with a very low amount of non-specific binding) and analyzed by mass cytometry. It was shown that coupling agents such as EDC were not needed, such was the reactivity of the particle surface. These particles were stable and the addition of a polymeric shell was shown did not affect the narrow lanthanide ion distribution within the particle interior as analyzed by mass cytometry. These particles represent the most promising candidates for the development of a highly multiplexed bioassay based on lanthanide-labeled particles to date.     

Energy transfer from a fluorescent hydrogel to a hosted fluorophore

The fluorescent properties of a new 1,3,5-cyclohexyltricarboxamide-based low-molecular-weight hydrogelator (1) derivatized with one hydrophobic fluorophore and two hydrophilic substituents have been investigated. Gels of 1 are composed of long, nonbranched fibers of uniform diameter, as shown by cryo-transmission electron microscopy (cryo-TEM). The aggregation of the naphthalene fluorophore moieties of the gelator molecules in the gel fibers favors the occurrence of a fast energy migration process that allows a very efficient sensitization of the fluorescence of a hosted fluorophore. Such processes have been investigated by the addition of propyldansylamide (PDNS), at two different concentrations, to gels of 1. Around 30% of the total PDNS added to the gels was found to be incorporated in the gel fibers, as confirmed by deconvolution of the fluorescence spectrum, excited-state lifetime measurements, and steady-state and time-resolved fluorescence anisotropy measurements. Moreover, anisotropy measurements show that the fluorophore that is incorporated within the gel fibers is almost completely immobilized, indicating that the interactions of PDNS with the gelator moieties are very strong. This particular configuration of donor (1) and acceptor (PDNS) molecules leads to a very efficient antenna effect, where 50% of the absorbed photons are funneled through to the dansyl derivative when one PDNS molecule is incorporated in the gel fibers for every 100 gelator molecules. A 5-fold higher concentration of PDNS increases the percentage of funneled photons to 75%.     

A study of storage conditions and treatments for forensic bone specimens using thermogravimetric analysis

Bone provides an important source of forensic evidence. The storage conditions of bone have been recognised as a factor in maintaining the integrity of such evidence. Thermogravimetric analysis (TG) has been employed to examine the effects of storage environments and preparation methods on the structural properties of pig bones. A comparison of oven and freeze drying has been made to study the effect of storage conditions. A comparison has also been made of ground bone specimens with cut specimens. Freeze-dried hand ground specimens provided the most consistent results and, thus, this is the recommended method of preparation of bone specimens for TG analysis.     

Synthesis and characterization of BaZrO3-doped YBa2Cu3O7−δ microtapes with improved critical current densities

We have recently demonstrated that through a sol–gel route, superconductor crystallization in the presence of simple biopolymers results in a drastic alteration of morphology, producing technologically useful nanowires and porous architectures. Morphological control is of the utmost importance to bulk high-temperature superconductors, as grain boundaries act as weak links in limiting the achievable critical current density (J_c). Here we show that, as expected, the incorporation of nanoparticulate barium zirconate (BaZrO₃) species into a biopolymer-mediated synthetic protocol for YBa₂Cu₃O_7?δ (Y123) leads to a significantly improved in-field J_c compared to that observed in a sample without BaZrO₃ additions. To ameliorate degradation of the BaZrO₃ species in this protocol, we demonstrate that by drawing the precursor sol into fibers, a microtape architecture is able to be formed, leading to lengthy, anisotropic structures having enhanced J_c through the retention of the BaZrO₃ species.     

Surface forces,supramolecular polymers,and inversion symmetry

The effects of supramolecular equilibrium polymers on surface forces are studied by both a phenomenological Landau type analysis and a molecular model based on a Bethe-Guggenheim approximation. We point out that surface forces brought about by equilibrium polymers may be completely different from what can be found with "ordinary" polymers. The new feature is the role of inversion (a)symmetry or "directionality" of the associating unit molecules ("monomers"). Symmetric B-B monomers (where B denotes a self-complementary binding group) give rise to nondirectional chains and lead to attractive forces between similar surfaces. Asymmetric A-D monomers (where A and D denote complementary acceptor and donor groups, respectively) produce directional chains and can cause strong repulsion. The range of the attractive force has a maximum at intermediate concentration, while the range of the repulsive force increases over the whole concentration range.     

The Aqueous Ca2+ System,in Comparison with Zn2+, Fe3 +, and Al3 +: An Ab Initio Molecular Dynamics Study

Herein, we report on the structure and dynamics of the aqueous Ca²⁺ system studied by using ab initio molecular dynamics (AIMD) simulations. Our detailed study revealed the formation of well‐formed hydration shells with characteristics that were significantly different to those of bulk water. To facilitate a robust comparison with state‐of‐the‐art X‐ray absorption fine structure (XAFS) data, we employ a 1st principles MD‐XAFS procedure and directly compare simulated and experimental XAFS spectra. A comparison of the data for the aqueous Ca²⁺ system with those of the recently reported Zn²⁺, Fe³⁺, and Al³⁺ species showed that many of their structural characteristics correlated well with charge density on the cation. Some very important exceptions were found, which indicated a strong sensitivity of the solvent structure towards the cation′s valence electronic structure. Average dipole moments for the 2nd shell of all cations were suppressed relative to bulk water.     

Identification of diastereomeric chlorophyll allomers by atmospheric pressure chemical ionisation liquid chromatography/tandem mass spectrometry

Atmospheric pressure chemical ionisation liquid chromatography/mass spectrometry (APCI-LC/MS) has been used for identification of the epimers of hydroxy, methoxy and methoxylactone allomers of chlorophyll a (13(2)-HO-chl a, 13(2)-MeO-chl a and 15(1)-MeO-lact-chl a), the hydroxy allomer of bacteriochlorophyll a (13(2)-HO-bchl a) and the hydroxy and methoxylactone allomers of bacterioviridin a (13(2)-HO-bvir a and 15(1)-MeO-lact-bvir a). The APCI mass spectra show that facile fragmentations involve the methoxyl or hydroxyl groups at the C-13(2) or C-15(1) chiral centres. Losses involving the C-13(2) or C-15(1) hydroxyl or methoxyl groups occur more easily from the S-epimer than from the R-epimer due to the greater relief of the steric strain associated with interaction with the bulky C-17 substituent. The differences in mass spectrometric fragmentation can be used as a diagnostic tool for the assignment of the stereochemical configuration at the C-13(2) or C-15(1) chiral centres.     

Versatile and facile synthesis of diverse semisynthetic tetracycline derivatives via Pd-catalyzed reactions

A diverse collection of tetracycline derivatives has been synthesized utilizing Heck, Suzuki, and other palladium-coupling reactions via tetracycline arenediazonium and iodoarene salts. Large numbers of tetracyclines are now possible via these reactions, including numerous upper periphery derivatives of doxycycline, minocycline, sancycline, and methacycline modified at positions C7, C9, and C6-C13 on the tetracycline naphthacene ring. Application of palladium-coupling reactions to the tetracyclines has yielded new tetracycline classes with differing structural attributes, greatly increasing the structural diversity of this family of antibiotics, one of the last of the early antibiotic families to be expanded by organic and medicinal chemistry.     

Are J(Si-H) NMR coupling constants really a probe for the existence of nonclassical H-Si interactions?

A series of hydridosilyl complexes of tantalum, Cp(ArN)Ta(PMe3)(H)(SiClnR3-n) (n = 0-3), was prepared and studied by 29Si NMR, X-ray diffraction, and DFT calculations. An unprecedented increase of the J(Si-H) coupling constant between the hydride and silyl ligands from 14 Hz for n = 0 to 50 Hz n = 3 was observed, which however, according to DFT calculations, does not correspond to stronger bonding interaction between silicon and hydride ligands, with the strongest interaction being for n = 1.