The Use of Contactless Conductivity for the On-Column Characterisation and Visualisation of Packing Homogeneity and Band Broadening in Capillary LC

Capacitively coupled contactless conductivity is presented as a simple non-invasive tool for the visualisation and evaluation of the axial homogeneity of packing density in capillary LC columns. Irregularities in frit structure and gross column voids were readily identified, the latter of which was confirmed with digital photography. Relative homogeneity of packing density was compared for two packed columns by measuring the variation in conductive response per unit length and varied from 1.1 to 4.2%. The on-column scanning methodology was applied to real-time visualisation of in-situ buffering effects arising from a packed poly-iminodiacetic acid bonded resin. Finally, the scanning detection technique was applied to the pre-elution visualisation of on-column band broadening.     

Microbial transformation of the sesquiterpenoid (−)-maaliol by Mucor plumbeus

Microbial transformation of the sesquiterpenoid (?)-maaliol by the fungus Mucor plumbeus gave two metabolites, (+)-7,8-didehydro-9β-hydroxymaalioxide and (?)-7,8-didehydro-1β-hydroxymaalioxide. Both metabolites are new and their structures were established on the basis of their spectroscopic properties and chemical reactions.     

Osmium‐Mediated Oxidative Cyclizations: A Study into the Range of Initiators That Facilitate Cyclization

A general route to prepare substituted, saturated five‐membered heterocycles has been developed. The application of a wide range of starting materials to the osmium‐catalyzed oxidative cyclization reaction is described. Diols, hydroxy‐amides, hydroxy‐sulfonamides, and carbamates all cyclize in moderate to excellent yields to give cis‐tetrahydrofurans and pyrrolidines, depending upon the position of the heteroatoms in the starting materials. These cyclizations all proceed with near total selectivity for the cis‐heterocycles, and with stereospecific introduction of a hydroxy group adjacent to the ring. Moreover, routes to enantiopure starting materials are described, which give enantiopure products upon cyclization. Catalyst loadings of as low as one mol percent have been successfully employed for this transformation.     

Development of a rapid and sensitive method for determination of cysteine/cystine ratio in chemically defined media

Two rapid, sensitive and quantitative methods for the determination of the cysteine and cystine ratio in complex defined media feedstock using monolithic reversed-phase liquid chromatography (RPLC) and RPLC–MS are presented. Cysteine is pre-derivatised with purified 2-chloro-1-methylquinolinium tetrafluoroborate (CMQT) and separated from other derivatisation products on a narrow-bore 50 mm × 2 mm I.D. monolithic C₁₈ column with UV detection at 355 nm. For reversed-phase LC (RPLC) the separation is carried out isocratically using a mobile phase of 50 mM trichloroacetic acid (TCA) adjusted to pH 2.5 with lithium hydroxide (LiOH) and acetonitrile (83:14) pumped at 1.5 mL/min with an elevated column temperature. For RPLC–MS an ammonium acetate and acetonitrile gradient method was developed with a reduced flow rate of 0.3 mL/min. The treatment of the samples consisted of dividing them into two aliquots, the first aliquot is analysed for cysteine and the second aliquot is analysed for cystine after its quantitative reduction to cysteine using tris(2-carboxyethyl)phosphine (TCEP). Both methods are linear, with R² > 0.999 for 0.25–500 μM for cysteine and 0.25–250 μM for cystine using the LC–UV method, sensitive, with detection limit of 36 nM for cysteine, and precise, with ≤1.1% RSD for both retention time and peak area (n = 6). Samples (n = 31) of an industry standard and supplied chemically defined media feedstock were analysed, finding cysteine ranging from 1.56 to 2.26 μg/mL and cystine from 1062.02 to 1348.13 μg/mL.     

Validation and application of reporter gene assays for the determination of estrogenic and androgenic endocrine disruptor activity in sport supplements

Previously developed estrogen and androgen mammalian reporter gene assays (RGAs) were assessed for their potential use as a quantitative screening method in the detection of estrogenic and androgenic endocrine disruptors (EDs) in sport supplements. The validation of both RGAs coupled with dispersive solid phase extraction (dSPE) was performed in accordance with European Commission Decision EC/2002/6579 for biological screening methods. Decision limits (CCα) and detection capabilities (CCβ) were established for both the estrogen and androgen RGAs. All samples were compliant with CCα and CCβ in both bioassays. Recovery rates were 96 % for 17β-estradiol and 115 % for dihydrotestosterone as obtained in their corresponding RGA. Both estrogens and androgens were stable in samples for more than 3 weeks, when stored at -20 °C. Specificity, good repeatability (coefficients of variation (CV), 12-25 %), reproducibility and robustness of both bioassays were also observed. Four different ED modes of action were determined for estrogens and androgens in 53 sport supplements, using the validated RGAs. This study revealed that 89 % of the investigated sport supplements contained estrogenic EDs and 51 % contained androgenic compounds. In conclusion, both bioassays are suitable for sport supplement screening of estrogenic and androgenic EDs.     

Correction of ultrasonic array images to improve reflector sizing and location in inhomogeneous materials using a ray-tracing model

The use of ultrasonic arrays has increased dramatically within recent years due to their ability to perform multiple types of inspection and to produce images of the structure through post-processing of received signals. Phased arrays offer many advantages over conventional transducers in the inspection of materials that are inhomogeneous with spatially varying anisotropic properties. In this paper, the arrays are focused on austenitic steel welds as a representative inhomogeneous material. The method of ray-tracing through a previously developed model of an inhomogeneous weld is shown, with particular emphasis on the difficulties presented by material inhomogeneity. The delay laws for the structure are computed and are used to perform synthetic focusing at the post-processing stage of signal data acquired by the array. It is demonstrated for a simulated austenitic weld that by taking material inhomogeneity and anisotropy into account, superior reflector location (and hence, superior sizing) results when compared to cases where these are ignored. The image is thus said to have been corrected. Typical images are produced from both analytical data in the frequency domain and data from finite element simulations in the time domain in a variety of wave modes, including cases with mode conversion and reflections.     

Simple Methods for Preparing Oligonucleotides Containing 1) Thiol Groups at their 5′-Termini, 2) 5′-Phosphates

Abstract

A simple method has been developed for synthesising oligonucleotides containing a thiol group at their 5′-termini. The sequence required is prepared using standard solid phase phosphoramidite methods and an extra round of synthesis is then performed with S-triphenylmethyl O-methoxymorpholino-phosphinyl 3-mercaptopropan (1) ol. After normal deblocking this gives an oligonucleotide containing a tritylthiol group attached to the 5′-phosphate of an oligonucleotide via a 3-carbon spacer arm. The trityl group can be removed with AgNO₃ at pH 5 to give the free thiol. This compound is stable at pH 8 and reacts cleanly and rapidly with sulphydryl specific probes (eg fluorescent iodoacetates) at this pH value. This method can be used to prepare a wide variety of usefully labelled oligonucleotides and it is envisaged that fluorescent oligonucleotides will be useful in the study of protein nucleic acid interactions and to replace ³²P labelled hybridisation probes.     

Modification of photon states in photonic molecules with semiconductor nanocrystals

We report on the coherent coupling of whispering gallery modes (WGMs) in a photonic molecule formed from two melamine formaldehyde spherical microcavities coated with a thin shell of CdTe nanocrystals. Utilizing different excitation conditions, the splitting of the WGM resonances originating from bonding and antibonding branches of the photonic states is observed and a fine structure consisting of very sharp peaks resulting from lifting of the WGM degeneracy has been detected. Observation of optical wavelength switching with controllable spectral position and separation is reported.