Highly Isoselective Ring-Opening Polymerization of -β-Butyrolactone: Access to Synthetic Poly(3-hydroxybutyrate) with Polyolefin-like Material Properties.

We report the highly isoselective ring-opening polymerization (ROP) of racemic β-butyrolactone (β-BL) using -generated catalysts based on Y[N(SiHMe)](THF) and salan-type pro-ligands. The catalyst system produces isotactic poly(3-hydroxybutyrate) (PHB) with record productivity (TOF up to 32 000 h) and the highest isoselectivity ( up to 0.89) in ROP of β-BL achieved to date.

Absolute content determination by quantitative NMR (qNMR) spectroscopy: a curious case of aldosterone.

Quantitative NMR spectroscopy has been utilized to calculate the absolute content (g g) of aldosterone, which is necessary for electrolyte balance and blood pressure regulation, in commercially available materials. Explanations have been provided for many signals observed in the HNMR spectrum, false interpretation of which can have significant effects if such a value is utilized for the primary calibrators in ID-LC-MS/MS ('gold standard') reference methods in clinical chemistry.

Quantitative NMR (qNMR) spectroscopy based investigation of the absolute content, stability and isomerization of 25-hydroxyvitamin D2/D3 and 24(R),25-dihydroxyvitamin D2 in solution phase.

Vitamin D is an important parameter, in serum/plasma based diagnostic analysis, for the determination of optimal regulation of calcium and phosphate homeostases in the human body, vital for the monitoring/progression of osteomalacia and rickets. Particularly, the quantification of 25-hydroxyvitamin D2, 25-hydroxyvitamin D3 and 24R,25-dihydroxyvitamin D in blood is an excellent indicator for the vitamin D status of a patient. For this purpose, LC-MS/MS methods, based on appropriate vitamin D reference standards, are considered to be 'gold standard' for such measurements.

An isotope dilution LC-MS/MS-based candidate reference method for the quantification of androstenedione in human serum and plasma.

The accurate measurement of androstenedione in human serum and plasma is required for steroid profiling to assure the appropriate diagnosis and differential diagnosis of hyperandrogenism. In this work, we introduce an isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) candidate reference measurement procedure for the quantification of androstenedione in human serum and plasma. The performance of the procedure enables its use in the evaluation and standardization of routine assays and for the evaluation of patient samples to ensure the traceability of individual patient results.

An isotope dilution LC-MS/MS based candidate reference method for the quantification of cyclosporine A, tacrolimus, sirolimus and everolimus in human whole blood.

An isotope dilution LC-MS/MS based candidate reference measurement procedure for the quantification of cyclosporine A, tacrolimus, sirolimus and everolimus in human whole blood is presented to be used for evaluation and standardization of routine assays applied for therapeutic drug monitoring. The assay allows baseline separation of the four immunosuppressive drugs within a total runtime of 9 minutes using a C4 reversed phase column. Sample preparation is based on protein precipitation with zinc sulphate followed by purification with solid phase extraction.

An LC-MS/MS based candidate reference method for the quantification of carbamazepine in human serum.

A validated LC-MS/MS-based candidate reference measurement procedure for the quantification of carbamazepine is presented in order to be used for standardization and harmonization of routine assays applied for therapeutic drug monitoring. Sample preparation was based on protein precipitation using acetonitrile followed by sample dilution. Since the previously listed certified reference material (CRM) SRM 1599 (anticonvulsant drug level assay standard) is no longer available, an ISO certified calibration material was used in this assay.

An LC-MS/MS based candidate reference method for the quantification of total gentamicin in human serum and plasma using NMR characterized calibrator material.

Background: Accurate measurement of gentamicin concentration in serum and plasma is required for therapeutic drug monitoring to ensure appropriate treatment of patients. In this work, we present a validated LC-MS/MS-based candidate reference measurement procedure for total gentamicin quantification to be used for standardization and harmonization of routine assays applied for therapeutic drug monitoring of this compound. Total gentamicin is the sum of the concentrations of five known congeners C1, C1a, C2, C2a and C2b.

Simultaneous quantification of four vitamin D metabolites in human serum using high performance liquid chromatography tandem mass spectrometry for vitamin D profiling.

Objectives: For quantification of 25-hydroxyvitamin D(3) (25OH-D(3)), 25-hydroxyvitamin D(2) (25OH-D(2)), 3-epi-25-hydroxyvitamin D(3) (3-epi-25OH-D(3)) and 24R,25-dihydroxyvitamin D(3) (24R,25(OH)(2)-D(3)) in human serum a high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method was developed and validated.

Design And Methods: After protein precipitation further purification is achieved with on-line sample preparation using a reversed phase (RP) C-4 column. Chromatographic separation is realized by a RP-column with core shell material and pentafluorophenyl (PFP) selectivity.

Treatment of pruritus in chronic liver disease with the 5-hydroxytryptamine receptor type 3 antagonist ondansetron: a randomized, placebo-controlled, double-blind cross-over trial.

Background: Recently, the serotonin antagonist ondansetron has been reported to have a positive effect on cholestasis-associated pruritus.

Objectives: To study the effect of orally administered ondansetron on pruritus in chronic liver disease in a randomized, placebo-controlled, double-blind, cross-over study.

Methods: Subjective severity of pruritus was assessed using a visual analogue scale (VAS) recorded four times daily by the patients.

Increased gastric and intestinal permeability in patients with Crohn's disease.

Objectives: Patients with Crohn's disease exhibit marked changes in intestinal permeability that can be assessed by lactulose and mannitol. Sucrose is a novel marker for gastric permeability. We combined these three sugars to investigate whether patients with Crohn's disease demonstrate changes in gastric permeability and if so, whether these changes are matched with altered intestinal permeability.

Comparison of iodine-123 low-density lipoprotein (LDL) and indium-111 LDL binding to mononuclear cells of healthy normolipaemic controls and patients with heterozygous familial hypercholesterolaemia.

The binding of radiolabelled lipoproteins, iodine-123-labelled low-density lipoprotein (LDL) and indium-111-labelled LDL, to peripheral blood mononuclear cells (MNCs) was compared in normolipaemic subjects and in patients with heterozygous familial hypercholesterolaemia (FH). 123I-LDL and 111In-LDL binding to MNCs exhibited high-affinity, highly specific, time- and temperature-dependent binding reaching saturation at concentrations above 50 nM. The number of LDL binding sites (Bmax) was significantly (P < 0.