Different coordination modes of the dimethyldisulfide ligand in trimethylplatinum(IV) complexes

The reaction of [PtMe₃(bpy)(Me₂CO)](BF₄) (2) (prepared from [PtMe₃I(bpy)] (1) plus Ag(BF₄)) with MeSSMe resulted in the formation of [PtMe₃(bpy)(MeSSMe-κS)](BF₄) (3). A single-crystal X-ray diffraction analysis revealed in the octahedral Pt(IV) complex (configuration index: OC-6-33), a conformation of the monodentately κS bound MeSSMe ligand (C–S–S–C 92.7(4)°) being very close to that in non-coordinated MeSSMe, thus allowing some hyperconjugative interaction stabilizing the S–S bond. The reaction of [K(18C6)][(PtMe₃)₂(μ-I)(μ-pz)₂] (4; 18C6 = 18-crown-6, Hpz = pyrazole) with Ag(BF₄) and MeSSMe resulted in the formation of dinuclear complexes [(PtMe₃)₂(μ-pz)₂(μ-MeSSMe)] existing at room temperature in acetone solution as different fast interconverting isomers. At –40 °C, two isomers with a μ-1κS:2κS (5a) and a μ-1κS:2κS′ (5b) coordinated MeSSMe ligand in the ratio 2:1 could be identified ¹H NMR spectroscopically. DFT calculations of type 5 complexes revealed the existence of two conformers with a μ-MeSSMe-1κS:2κS ligand, which differ mainly in the C–S–S–C dihedral angle (66.4 vs. 180.0° 6a/6a′). They have essentially the same energy and a very low activation barrier in acetone as solvent (1.3 kcal/mol) for their mutual interconversion. A further equilibrium structure was identified to be an isomer having a μ-MeSSMe-1κS:2κS′ ligand (6b) that proved to be only 1.9 kcal/mol higher in energy than 6a/6a′.     

Ultrafast and high-throughput mass spectrometric assay for therapeutic drug monitoring of antiretroviral drugs in pediatric HIV-1 infection applying dried blood spots

Kaletra® (Abott Laboratories) is a co-formulated medication used in the treatment of HIV-1-infected children, and it contains the two antiretroviral protease inhibitor drugs lopinavir and ritonavir. We validated two new ultrafast and high-throughput mass spectrometric assays to be used for therapeutic drug monitoring of lopinavir and ritonavir concentrations in whole blood and in plasma from HIV-1-infected children. Whole blood was blotted onto dried blood spot (DBS) collecting cards, and plasma was collected simultaneously. DBS collecting cards were extracted by an acetonitrile/water mixture while plasma samples were deproteinized with acetone. Drug concentrations were determined by matrix-assisted laser desorption/ionization-triple quadrupole tandem mass spectrometry (MALDI-QqQ-MS/MS). The application of DBS made it possible to measure lopinavir and ritonavir in whole blood in therapeutically relevant concentrations. The MALDI-QqQ-MS/MS plasma assay was successfully cross-validated with a commonly used high-performance liquid chromatography (HPLC)–ultraviolet (UV) assay for the therapeutic drug monitoring (TDM) of HIV-1-infected patients, and it showed comparable performance characteristics. Observed DBS concentrations showed as well, a good correlation between plasma concentrations obtained by MALDI-QqQ-MS/MS and those obtained by the HPLC-UV assay. Application of DBS for TDM proved to be a good alternative to the normally used plasma screening. Moreover, collection of DBS requires small amounts of whole blood which can be easily performed especially in (very) young children where collection of large whole blood amounts is often not possible. DBS is perfectly suited for TDM of HIV-1-infected children; but nevertheless, DBS can also easily be applied for TDM of patients in areas with limited or no laboratory facilities.     

Assessment of cardiac iron by MRI susceptometry and R2* in patients with thalassemia

A magnetic resonance imaging cardiac magnetic susceptometry (MRI-CS) technique for assessing cardiac tissue iron concentration based on phase mapping was developed. Normal control subjects (n=9) and thalassemia patients (n=13) receiving long-term blood transfusion therapy underwent MRI-CS and MRI measurements of the cardiac relaxation rate R2*. Using MRI-CS, subepicardium and subendocardium iron concentrations were quantified exploiting the hemosiderin/ferritin iron specific magnetic susceptibility. The average of subepicardium and subendocardium iron concentrations and R2* of the septum were found to be strongly correlated (r=0.96, P<.0001), and linear regression analysis yielded CIC (μg Fe/g_{wet tissue})=(6.4±0.4)·R2* _septum (s⁻¹) − (120±40). The results demonstrated that septal R2* indeed measures cardiac iron level.     

Three-dimensional T1, T2 and proton density mapping with inversion recovery balanced SSFP

By combining a balanced steady-state free precession (bSSFP) readout with an initial inversion pulse, all three contrast parameters, T₁, T₂ and proton density (M₀), may be rapidly calculated from the signal progression in time. However, here it is shown that this technique is quite sensitive to variation in the applied transmit RF (B₁) field, leading to pronounced errors in calculated values. Two-dimensional (2D) acquisitions are taxed to accurately quantify the relaxation, as the short RF pulses required by SSFP's rapid TR contain a broad spectrum of excitation angles. A 3D excitation using a large diameter excitation coil was able to correctly quantify the parameters. While the extreme B₁ sensitivity was previously problematic and has precluded use of IR-bSSFP for relaxometry, in this work these obstacles were significantly reduced, allowing the rapid quantification of T₁, T₂ and M₀. The results may further be used to simulate image contrast from common sequences, such as a T₁-weighted or fluid-attenuated inversion recovery (FLAIR) examination.     

Quantitative problem structuring methods for multi-actor problems: an analysis of reported applications

Problem structuring methods (PSMs) are proposed as vital tools for coping with complex and unstructured problems that help decision-makers make decisions or come to a shared understanding of a problem situation. Despite their popularity, choosing a PSM for an unstructured problem situation is problematic as good categorization and evaluation of PSMs is lacking. As a first step we postulate a categorization of quantitative PSMs applied to multi-actor situations. We list the different application areas, the types of design that were used, and the type of outcomes the methods provide. To understand why and how certain PSMs are applied, we categorize applications of metagames/conflict analysis, hypergames, drama theory, Q-methodology, and transactional analysis. We find that method choice and validation of the applications are yet underdeveloped for this specific sub-field, and suggest further work on this as it will help to understand the added value of PSMs.     

Origins of life and biochemistry under high-pressure conditions

Life on Earth can be traced back to as far as 3.8 billion years (Ga) ago. The catastrophic meteoritic bombardment ended between 4.2 and 3.9 Ga ago. Therefore, if life emerged, and we know it did, it must have emerged from nothingness in less than 400 million years. The most recent scenarios of Earth accretion predict some very unstable physico-chemical conditions at the surface of Earth, which, in such a short time period, would impede the emergence of life from a proto-biotic soup. A possible alternative would be that life originated in the depth of the proto-ocean of the Hadean Earth, under high hydrostatic pressure. The large body of water would filter harmful radiation and buffer physico-chemical variations, and therefore would provide a more stable radiation-free environment for pre-biotic chemistry. After a short introduction to Earth history, the current tutorial review presents biological and physico-chemical arguments in support of high-pressure origin for life on Earth.