Intra-operative optical diagnostics with vibrational spectroscopy

Established methods for characterization of tissue and diagnostics, for example histochemistry, magnetic resonance imaging (MRI), X-ray tomography, or positron emission tomography (PET), are mostly not suitable for intra-operative use. However, there is a clear need for an intra-operative diagnostics especially to identify the borderline between normal and tumor tissue. Currently, vibrational spectroscopy techniques (both Raman and infrared) complement the standard methods for tissue diagnostics. Vibrational spectroscopy has the potential for intra-operative use, because it can provide a biochemically based profile of tissue in real time and without requiring additional contrast agents, which may perturb the tissue under investigation. In addition, no electric potential needs to be applied, and the measurements are not affected by electromagnetic fields. Currently, promising approaches include Raman fiber techniques and nonlinear Raman spectroscopy. Infrared spectroscopy is also being used to examine freshly resected tissue ex vivo in the operating theater. The immense volume of information contained in Raman and infrared spectra requires multivariate analysis to extract relevant information to distinguish different types of tissue. The promise and limitations of vibrational spectroscopy methods as intra-operative tools are surveyed in this review.     

V-shaped nematogens with the "magic bent angle"

V-shaped nematogens 1a-c and 2a-b with benzodithiophene bending units have been synthesised. The derivatives 1a-c comprise a flat core with a bending angle of 109°, which is almost the tetrahedral angle proposed to be optimal in the realization of mesogens forming a biaxial nematic thermotropic mesophase.     

Predicting the influence of a p2-symmetric substrate on molecular self-organization with an interaction-site model

An interaction-site model can a priori predict molecular self-organisation on a new substrate in Monte Carlo simulations. This is experimentally confirmed with scanning tunnelling microscopy on Fréchet dendrons of a pentacontane template. Local and global ordering motifs, inclusion molecules and a rotated unit cell are correctly predicted.     

Charge as you like! Efficient manipulation of negative ion net charge in electrospray ionization of proteins and nucleic acids

Acidic proteins and nucleic acids such as RNA are most readily ionized in electrospray ionization (ESI) operated in negative-ion mode. The multiply deprotonated protein or RNA ions can be used as precursors in top- down mass spectrometry. Because the performance of the dissociation method used critically depends on precursor ion negative net charge, it is important that the extent of charging in ESI can be manipulated efficiently. We show here that (M - nH)(n-) ion net charge of proteins and RNA can be controlled efficiently by the addition of organic bases to the electrosprayed solution. Our study also highlights the fact that ion formation in ESI in negative mode is only poorly understood.