Determination of imatinib and its active metabolite N-desmethyl imatinib in human plasma by liquid chromatography/tandem mass spectrometry

Imatinib is a first-line treatment for chronic myelogenous leukaemia (CML). The pharmacokinetics of imatinib in patients with CML are characterised by large interpatient variability. Concentration monitoring of imatinib and its active metabolite N-desmethyl imatinib (DMI) is considered necessary to enhance the safe and effective use of imatinib. A rapid, simple and sensitive liquid chromatography/tandem mass spectrometry assay was developed for the simultaneous determination of imatinib and its metabolite DMI in human plasma. After proteins were precipitated with acetonitrile, imatinib, DMI and the internal standard D8-imatinib were resolved on a Gemini-NX 3?μm C18 column using gradient elution of 0.05?% formic acid and methanol. The three compounds were detected using electrospray ionisation in the positive mode. Standard curves of imatinib and DMI were adequately fitted by quadratic equations (r?>?0.999) over the concentration range of 10 to 2,000?ng/mL which encompasses clinical concentrations. Bias was ≤±8.3?%, intra- and inter-day coefficients of variation (imprecision) were ≤8.0?% and the limit of quantification was 10?ng/mL for both imatinib and DMI. The assay is being used successfully in clinical practice to enhance the safe and effective use of imatinib.     

Low loss propagation in slow light photonic crystal waveguides at group indices up to 60

We have designed slow light photonic crystal waveguides operating in a low loss and constant dispersion window of Δλ = 2 nm around λ = 1565 nm with a group index of n_g = 60. We experimentally demonstrate a relatively low propagation loss, of 130 dB/cm, for waveguides up to 800 μm in length. This result is particularly remarkable given that the waveguides were written on an electron-beam lithography tool with a writefield of 100 μm that exhibits stitching errors of typically 10–50 nm. We reduced the impact of these stitching errors by introducing “slow–fast–slow” mode conversion interfaces and show that these interfaces reduce the loss from 320 dB/cm to 130 dB/cm at n_g = 60. This significant improvement highlights the importance of the slow–fast–slow method and shows that high performance slow light waveguides can be realised with lengths much longer than the writing field of a given e-beam lithography tool.     

Time-resolved chirp measurement for 100GBaud test systems using an ideal frequency discriminator

In this paper we present multi-channel chirp measurements of wide-band sources, using a programmable Fourier-domain optical processor (FDOP) as a near-perfect linear frequency discriminator element followed by a fast photodiode and electrical sampling oscilloscope. The electric field of a 10.7 Gbit/s phase-encoded data source and a directly modulated laser diode are simultaneously interrogated with this measurement system. The constellation diagram of the phase-encoded data source is demonstrated, and a comparison with another phase-sensitive measurement technique is performed. Additionally, an extension to this technique is demonstrated in which the time-resolved chirp of a picosecond-duration mode-locked laser diode with a 260 GHz spectral bandwidth is characterised using the FDOP and a high-bandwidth optical sampling oscilloscope. This measurement ensemble has sufficient temporal resolution to characterise random or repetitive data signals up to 100GBaud.     

Application of the lithiation-borylation reaction to the rapid and enantioselective synthesis of the bisabolane family of sesquiterpenes

The expedient enantioselective synthesis of 5 bisabolane sesquiterpenes has been achieved using a common, one-pot lithiation-borylation reaction of secondary benzylic carbamates and either protodeboronation or oxidation to give the natural products in fewer than 5 steps, with high yield and >94?:?6 er.     

cis‐Tetra­carbonyl­[(4‐fluoro­phenyl)di­phenyl­phosphine‐P](piperidine‐N)molybdenum(0)

The title mol­ecule, [Mo{P(C₆H₅)₂(C₆H₄F)}(HNC₅H₁₀)(CO)₄] or [Mo(C₁₈H₁₄FP)(C₅H₁₁N)(CO)₄], has irregular octahedral geometry about the Mo atom. The mol­ecules form a complicated hydrogen‐bonded network comprising C—H?O, C—H?F and C—H?π hydrogen bonds and π–π interactions. The C—H?π and π–π interactions form chains containing C—H?π/π–π dimers linked via C—H?π interactions and the chains are linked into a three‐dimensional network via C—H?O and C—H?F hydrogen bonds.     

Towards a total synthesis of the manadomanzamine alkaloids: the first asymmetric construction of the pentacyclic indole core

We report a highly diastereoselective approach for the synthesis of the pentacyclic indole core of the manadomanzamine alkaloid skeleton, with complete control over the relative and absolute stereochemistries at the three contiguous stereocentres at ring positions 1, 10, and 24, from a readily available chiral template.     

Complementary routes for the stereoselective synthesis of functionalized benzoquinolizidine targets

We report new and complementary routes for the highly stereoselective construction of functionalized benzoquinolizidine targets from readily available, non-racemic chiral templates. The methods developed allow us to predetermine relative product stereochemistries by judicious choice of substrate sub-structure, and provide ready access to alternative stereoisomers.     

High-resolution MALDI imaging mass spectrometry allows localization of peptide distributions at cellular length scales in pituitary tissue sections

Matrix assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) has been used to determine peptide distributions directly from rat, mouse and human pituitary tissue sections. Since these organs are small (10²–10³ μm) the spatial resolution of IMS is a key issue in molecular imaging of pituitary tissue sections. Here we show that high-resolution IMS allows localization of neuropeptide distributions within different cell clusters of a single organ of a pituitary tissue section. The sample preparation protocol does not result in analyte redistribution and is therefore applicable to IMS experiments at cellular length scales. The stigmatic imaging mass spectrometer used in this study produces selected-ion-count images with pixel sizes of 500 nm and a resolving power of 4 μm, yielding superior spatial detail compared to images obtained in microprobe imaging experiments. Furthermore, we show that with imaging mass spectrometry a distinction can be made between different mammalian tissue sections based on differences in the amino acid sequence of neuropeptides with the same function. This example demonstrates the power of IMS for label-free molecular imaging at relevant biological length scales.     

Photographie

Ohne Zusammenfassung