Multidimensional nano-HPLC coupled with tandem mass spectrometry for analyzing biotinylated proteins

Multidimensional high-performance liquid chromatography (HPLC) is a key method in shotgun proteomics approaches for analyzing highly complex protein mixtures by complementary chromatographic separation principles. Here, we describe an integrated 3D-nano-HPLC/nano-electrospray ionization quadrupole time-of-flight mass spectrometry system that allows an enzymatic digestion of proteins followed by an enrichment and subsequent separation of the created peptide mixtures. The online 3D-nano-HPLC system is composed of a monolithic trypsin reactor in the first dimension, a monolithic affinity column with immobilized monomeric avidin in the second dimension, and a reversed phase C18 HPLC-Chip in the third dimension that is coupled to a nano-ESI-Q-TOF mass spectrometer. The 3D-LC/MS setup is exemplified for the identification of biotinylated proteins from a simple protein mixture. Additionally, we describe an online 2D-nano-HPLC/nano-ESI-LTQ-Orbitrap-MS/MS setup for the enrichment, separation, and identification of cross-linked, biotinylated species from chemical cross-linking of cytochrome c and a calmodulin/peptide complex using a novel trifunctional cross-linker with two amine-reactive groups and a biotin label.

Easy Preparation of 1,3-Di-tert-Butylbenzene and Some Derivatives Thereof

1,3-Di-tert-butylbenzene (4) can conveniently be prepared from 1-bromo-3,5-di-tert-butylbenzene (2) which, in turn, is obtained from the easily available 1,3,5-tri-tert-butylbenzene (1). The use of 4 is illustrated by the preparation of the arylphosphines 6 and 7.     

Molecular dynamics and conformational behaviour of mesogenic resorcinarenes

The dynamic and conformational behaviour of four mesogenic resorcinarenes exhibiting columnar mesophases have been studied by a combination of broadband dielectric spectroscopy and deuterium solid state NMR. Broadband dielectric spectroscopy provided evidence for two relaxation processes present both in the mesophase and in the isotropic liquid. The high frequency process II, common to all mesogens, has been assigned to the libration of the carbonyl groups of the ester junctions between the core and the side chains. The low frequency process I, present in conformationally mobile mesogens 1 and 2, has been attributed to the ring inversion process of the macrocyclic core associated with dipole inversion along the columnar axis. Deuterium solid state NMR performed on 4, the deuteriated analogue of 1, confirmed the molecular dynamics attribution for process I, assigning the ring inversion to the interconversion of the two equivalent crown conformations.     

Biologically Active 1-Aminodeoxy and 1-O-Alkyl Derivatives of The Powerful D-Glucosidase Inhibitor 2,5-Dideoxy-2,5-Imino-D-Mannitol

ABSTRACT

By an Amadori rearrangement of easily available 5-azido-5-deoxy-D-glucofuranose with dibenzylamine and subsequent catalytic hydrogenation of the resulting 5-azido-1-(N,N-dibenzyl)amino-1,5-dideoxy-D-fructopyranose, 1-amino-1,2,5-trideoxy-2,5-imino-D-mannitol was obtained in only two steps and in excellent overall yield. Likewise, other amines were employed to introduce extended side chains ultimately suitable for attachment of the inhibitor to solid supports. The reported rearrangement reaction is a high yielding, convenient and apparently general entry to 1-aminodeoxyketopyranoses modified at C-5, facilitated by the ring enlargement of the aldofuranose to the ketopyranose as an additional driving force. A range of selected chain extended analogues was prepared by acylation of N-1. Inhibitors obtained exhibit K _i-values with D-glucosidases in the micromolar range. Interestingly, 1-N-acylation resulted in superior inhibitory activities, as did the addition of a hexyl chain.