Recent developments in protein–ligand affinity mass spectrometry

This review provides an overview of direct and indirect technologies to screen protein–ligand interactions with mass spectrometry. These technologies have as a key feature the selection or affinity purification of ligands in mixtures prior to detection. Specific fields of interest for these technologies are metabolic profiling of bioactive metabolites, natural extract screening, and the screening of libraries for bioactives, such as parallel synthesis libraries and small combichem libraries. The review addresses the principles of each of the methods discussed, with a focus on developments in recent years, and the applicability of the methods to lead generation and development in drug discovery.     

Spectroscopic detection of DNA quadruplexes by vibrational circular dichroism

The four-stranded G-quadruplex motif is a conformation frequently adopted by guanine-rich nucleic acids that plays an important role in biology, medicine, and nanotechnology. Although vibrational spectroscopy has been widely used to investigate nucleic acid structure, association of particular spectral features with the quadruplex structure has to date been ambiguous. In this work, experimental IR absorption and vibrational circular dichroism (VCD) spectra of the model quadruplex systems d(G)(8) and deoxyguanosine-5'-monophosphate (5'-dGMP) were analyzed using molecular dynamics (MD) and quantum-chemical modeling. The experimental spectra were unambiguously assigned to the quadruplex DNA arrangement, and several IR and VCD bands related to this structural motif were determined. Involvement of MD in the modeling was essential for realistic simulation of the spectra. The VCD signal was found to be more sensitive to dynamical structural variations than the IR signal. The combination of the spectroscopic techniques with multiscale simulations provides extended information about nucleic acid conformations and their dynamics.     

A printed nanolitre-scale bacterial sensor array

The last decade has witnessed a significant increase in interest in whole-cell biosensors for diverse applications, as well as a rapid and continuous expansion of array technologies. The combination of these two disciplines has yielded the notion of whole-cell array biosensors. We present a potential manifestation of this idea by describing the printing of a whole-cell bacterial bioreporters array. Exploiting natural bacterial tendency to adhere to positively charged abiotic surfaces, we describe immobilization and patterning of bacterial "spots" in the nanolitre volume range by a non-contact robotic printer. We show that the printed Escherichia coli-based sensor bacteria are immobilized on the surface, and retain their viability and biosensing activity for at least 2 months when kept at 4 °C. Immobilization efficiency was improved by manipulating the bacterial genetics (overproducing curli protein), the growth and the printing media (osmotic stress and osmoprotectants) and by a chemical modification of the inanimate surface (self-assembled layers of 3-aminopropyl-triethoxysilane). We suggest that the methodology presented herein may be applicable to the manufacturing of whole-cell sensor arrays for diverse high throughput applications.     

PNO-CI and PNO-CEPA studies of electron correlation effects

Dipole moments and static dipole polarizabilities are calculated for neon and the molecules HF, H₂O, NH₃, CH₄ and CO from SCF and correlated wavefunctions.

The construction of appropriate gaussian-type basis sets is discussed and the convergence of the correlation contributions to the polarizability is analysed. The effect of vibrational averaging is also investigated. The polarizabilities as obtained from the coupled electron pair approximation (CEPA) with the most extended basis sets differ from experimental values by less than 1·5 per cent in all cases. The calculated polarizability anisotropies appear to be correct to about 5–15 per cent. The correlation contributions to the polarizabilities are found to vary from 3 to 12 per cent.     

A Simple Procedure for the Preparation of Chiral ‘Tris(hydroxymethyl)methane’ Derivatives

The aldol adducts 1a – 13a of R,R-2(tertbutyl)-6-methyl-1,3-dioxan-4-one (from 3-hydroxybutanoic acid) to aldehydes, single diastereoisomers obtained as described previously, are acetylated or benzoylated to the corresponding esters 1b – 5b and 6c – 13c , respectively, which in turn are reduced with LiAlH₄ to the title compounds 14 – 24 . The enantiomerically pure triols thus available may be useful as chiral building blocks, as auxiliaries for enantioselective reactions, and as center pieces for chiral dendrimers.     

Laser Based Techniques for Ultra Trace Isotope Production, Spectroscopy and Detection

A variety of research activities in the field of fundamental and applied nuclear physics has evolved in the last years using resonantly tuned radiation from powerful lasers. The technique of resonance ionization spectroscopy has delivered outstanding results and found broad acceptance in the last years as a particularly efficient and highly selective method for rare and exotic radioisotope studies. It is used for production, spectroscopy and detection of these species and provides complete isobaric, high isotopic and even some isomeric selection, which altogether is needed for on-line investigation of short lived species far off stability as well as for ultra trace determination. Good overall efficiency pushes the experimental limits of detection in elemental trace analysis down to below 10⁶ atoms per sample, and additionally isotopic selectivity as high as 3 × 10¹² has been demonstrated. The widespread potential of resonance ionization techniques is discussed, focusing on the experimental arrangements for applications in selective on-line isotope production, spectroscopy of rare radioisotopes and ultra trace determination of radiotoxic isotopes like ²³⁸Pu to ²⁴⁴Pu, ^135,137Cs, ^89,90Sr or ⁴¹Ca in environmental, technical and biomedical samples.