Curved laser-sheet for conformal surface flow diagnostics

Three-dimensional surface illumination using curved laser-sheet techniques is introduced for optical flow measurements in conformal curved surfaces. The illumination method is applicable to many different optical-based flow measurement techniques, with this paper focusing on application to flow visualization and particle image velocimetry. A brief discussion and example of curved laser-sheet generation is given followed by an example of the technique applied to PIV of low Reynolds number transitional flow around a low-pressure turbine blade.     

Alkaline phosphatase assay using a near-infrared fluorescent substrate merocyanine 700 phosphate

Alkaline phosphatase (ALP) is a phosphomonoester hydrolase that is commonly used as a conjugating enzyme in biological research. A wide variety of substrates have been developed to assay its activity. In this study, we developed an ALP assay method utilizing merocyanine 700 (MC700) based substrate MC700 phosphate (MC700p). MC700 is a near-infrared fluorescent merocyanine dye, and has excitation/emission maxima at 686 nm/722 nm in ALP assay buffer. Upon hydrolysis by ALP, MC700p is converted to MC700. The fluorescence of MC700 is dependent on the pH and detergent concentration in the buffer. The fluorescence signal produced by MC700p hydrolysis is linearly related to the ALP amount and substrate concentration. A stop solution containing EDTA could be used to stop the ALP/MC700p reaction. It was also demonstrated that MC700p could substitute pNpp as the ALP substrate in a commercial 17β-Estradiol enzyme immunoassay kit.     

Redox electron-transfer reactions: electrochemically mediated rearrangement, mechanism, and a total synthesis of daucene

The term "housane" refers to molecules possessing a bicyclo[2.1.0]pentane core. One was designed, synthesized, and used as a precursor of daucene, a member of the carotane class of sesquiterpenes. The total synthesis was completed, thereby marking the first time that housane-derived cation radicals have been used as the key intermediate in the synthesis of a natural product. The transformation used in the construction and featured in the text involves an oxidation to generate the cation radical via either a chemically or an electrochemically mediated electron transfer, the latter process using tris(p-bromophenyl)amine as the mediator. The two methods are compared, and guiding principles are formulated to assist in deciding how best to implement each. Both processes afford an unfavorable equilibrium state that is subsequently drained toward the product by two irreversible events, viz., a 1,2 carbon migration to the site that best stabilizes a positive charge and a second electron transfer, this time being a highly exothermic reduction of the rearranged species to generate the neutral product. A mechanistic proposal calling for the use of a catalytic quantity of the electrochemical mediator and the consumption of exceptionally small quantities of current is advanced. Experimental deviations from these predictions are noted, and a rationale to account for them is presented. Finally, significant differences were noted between the cyclic voltammograms of housanes bearing a CH2OR substituent rather than a methyl group at the bridgehead carbon. Those having the inductively withdrawing group displayed broad and ill-defined curves. The differences were investigated quantum mechanically, and a stereoelectronic argument is formulated stating that broadness of the curve for the ROCH2-substituted systems is the result of a time-averaged sampling of the HOMO energies over the distribution of conformers. The possible generality of the stereoelectronic effect is noted.     

DNA barcode identification of black cohosh herbal dietary supplements

Black cohosh (Actaea racemosa) herbal dietary supplements are commonly consumed to treat menopausal symptoms, but there are reports of adverse events and toxicities associated with their use. Accidental misidentification and/or deliberate adulteration results in harvesting other related species that are then marketed as black cohosh. Some of these species are known to be toxic to humans. We have identified two matK nucleotides that consistently distinguish black cohosh from related species. Using these nucleotides, an assay was able to correctly identify all of the black cohosh samples in the validation set. None of the other Actaea species in the validation set were falsely identified as black cohosh. Of 36 dietary supplements sequenced, 27 (75%) had a sequence that exactly matched black cohosh. The remaining nine samples (25%) had a sequence identical to that of three Asian Actaea species (A. cimicifuga, A. dahurica, and A. simplex). Manufacturers should routinely test plant material using a reliable assay to ensure accurate labeling.     

Synthesis, structure, and biological activity of ferrocenyl carbohydrate conjugates

Seven ferrocenyl carbohydrate conjugates were synthesized. Coupling reactions of monosaccharide derivatives with ferrocene carbonyl chloride produced {6-N-(methyl 2,3,4-tri-O-acetyl-6-amino-6-deoxy-alpha-D-glucopyranoside)}-1-ferrocene carboxamide (3), {1-O-(2,3,4,6-tetra-O-benzyl-D-glucopyranose)}-1-ferrocene carboxylate (4), and {6-O-(1,2,3,4-tetra-O-acetyl-beta-D-glucopyranose)}-1-ferrocene carboxylate (5). Similarly, 1,1'-bis(carbonyl chloride)ferrocene was coupled with the appropriate sugars to produce the disubstituted analogues bis{6-N-(methyl 2,3,4-tri-O-acetyl-6-amino-6-deoxy-alpha-D-glucopyranoside)}-1,1'-ferrocene carboxamide (8), bis{1-O-(2,3,4,6-tetra-O-benzyl-D-glucopyranose)}-1,1'-ferrocene carboxylate (9), and bis{6-O-(1,2,3,4-tetra-O-acetyl-beta-D-glucopyranose)}-1,1'-ferrocene carboxylate (10). {6-N-(Methyl-6-amino-6-deoxy-alpha-D-glucopyranoside)}-1-ferrocene carboxamide monohydrate (12) was synthesized via amide coupling of an activated ferrocenyl ester with the corresponding carbohydrate. All compounds were characterized by elemental analysis, 1H NMR spectroscopy, and mass spectrometry. X-ray crystallography confirmed the solid-state structure of three ferrocenyl carbohydrate conjugates: 2-N-(1,3,4,6-tetra-O-acetyl-2-amino-2-deoxy-D-glucopyranose)-1-ferrocene carboxamide (1), 1-S-(2,3,4,6-tetra-O-acetyl-1-deoxy-1-thio-D-glucopyranose)-1-ferrocene carboxylate (2), and 12. The above compounds, along with bis{2-N-(1,3,4,6-tetra-O-acetyl-2-amino-2-deoxy-D-glucopyranose)}-1,1'-ferrocene carboxamide (6), bis{1-S-(2,3,4,6-tetra-O-acetyl-1-deoxy-1-thio-D-glucopyranose)}-1,1'-ferrocene carboxylate (7), and 2-N-(2-amino-2-deoxy-D-glucopyranose)-1-ferrocene carboxamide (11) were examined for cytotoxicity in cell lines (L1210 and HTB-129) and for antimalarial activity in Plasmodium falciparum strains (D10, 3D7, and K1, a chloroquine-resistant strain). In general, the compounds were nontoxic in the human cell line tested (HTB-129), and compounds 4, 7, and 9 showed moderate antimalarial activity in one or more of the P. falciparum strains.     

Separation of beta2-microglobulin conformers by high-field asymmetric waveform ion mobility spectrometry (FAIMS) coupled to electrospray ionisation mass spectrometry

An investigation into the use of high-field asymmetric waveform ion mobility spectrometry (FAIMS) coupled to electrospray ionisation mass spectrometry (ESI-MS) for the differentiation of co-populated protein conformers has been conducted on the amyloidogenic protein beta(2)-microglobulin (beta(2)m). Accumulation of beta(2)m in vivo can result in the deposition of insoluble fibrils whose formation is thought to originate from partially folded protein conformers; hence, the folding properties of beta(2)m are of significant interest. We have analysed beta(2)m using ESI-FAIMS-MS under a range of pH conditions and have studied the effect of the ion mobility spectrometry parameters on the behaviour of the various protein conformers. The data show that different protein conformers can be detected and analysed by ESI-FAIMS-MS, the results being consistent with observations of pH denaturation obtained using complementary biophysical techniques. A variant of beta(2)m with different folding characteristics has been analysed for comparison, and the distinctions observed in the data sets for the two proteins are consistent with their folding behaviour. ESI-FAIMS-MS offers significant opportunities for the study of the conformational properties of proteins and thus may present valuable insights into the roles that different conformers play in diseases related to protein folding.     

Complete large-molecule high-resolution mass spectra from 50-femtomole microvolume injection

For electrospray ionization in Fourier-transform mass spectrometry, direct injection of 5×10^?14 mol (0.5 µL of 100 nM from a microvolume sample valve) of ubiquitin (8565 Da) into the flowing solvent stream yields a spectrum with 85:1 signal-to-noise ratio, 2-ppm mass accuracy, and isotopic resolution. Gated trapping for 100 µs from a 0.15-µL/min injection of 20-µM ubiquitin consumes 5×10^?18 mol, which produces a spectrum with 23:1 signal-to-noise ratio and τ;3×10⁵ resolving power.     

Identification of “Known Unknowns” Utilizing Accurate Mass Data and Chemical Abstracts Service Databases

In many cases, an unknown to an investigator is actually known in the chemical literature. We refer to these types of compounds as “known unknowns.” Chemical Abstracts Service (CAS) Registry is a particularly good source of these substances as it contains over 54 million entries. Accurate mass measurements can be used to query the CAS Registry by either molecular formulae or average molecular weights. Searching the database by the web-based version of SciFinder is the preferred approach when molecular formulae are available. However, if a definitive molecular formula cannot be ascertained, searching the database with STN Express by average molecular weights is a viable alternative. The results from either approach are refined by employing the number of associated references or minimal sample history as orthogonal filters. These approaches were shown to be successful in identifying “known unknowns” noted in LC-MS and even GC-MS analyses in our laboratory. In addition, they were demonstrated in the identification of a variety of compounds of interest to others.     

Non‐Brownian Particle‐Based Materials with Microscale and Nanoscale Hierarchy

Colloidal crystals are interesting materials owing to their customizable photonic properties, high surface area, and analogy to chemical structures. The flexibility of these materials has been greatly enhanced through mixing particles with varying sizes, compositions, and surface charges. In this way, distinctive patterns or analogies to chemical stoichiometries are produced; however, to date, this body of research is limited to particles with nanoscale dimensions. A simple method is now presented for bottom‐up assembly of non‐Brownian particle mixtures to create a new class of hierarchically‐ordered materials that mimic those found in nature (both in pore distribution as well as stoichiometry). Additionally, these crystals serve as a template to create particle‐based inverted crystalline structures with customizable properties.     

Spectra and structure of small ring compounds. Part L VIII: Structural parameters for chlorocyclobutane from combined microwave data and ab initio calculations

The structural parameters of chlorocyclobutane,c-C₄H₇Cl, have been obtained fromab initio Hartree-Fock calculations employing the 6–31G^* basis set for both the more stable equatorial and the high energy axial conformers. The determined carbonhydrogen distances were adjusted by 0.010 Å and held fixed while a weighted least-squares adjust was used to obtain all of the heavy atom parameters for the equatorial conformer by fitting the rotational constants of nine isotopic species. The determinedr ₀ parameters are:r(C - C) = 1.535(8) År(C - C) = 1.548(3) År(C - Cl) = 1.788(9) Å CCC, - CL = 132.0(2)°; CCC, = 89.7(6)°; CCC, = 87.1(2)°, and CCC, = 88.7(2)°. These results are compared to the calculated values as well as those obtained earlier from electron diffraction and microwave studies.For Part LVII, seeJ. Raman Spectrosc.,1990,21, 591.Taken in part from the thesis of M. J. Lee which will be submitted to the Department of Chemistry in partial fulfillment of the Ph.D. degree.