Structural identification of N-glycan isomers using logically derived sequence tandem mass spectrometry.

N-linked glycosylation is one of the most important protein post-translational modifications. Despite the importance of N-glycans, the structural determination of N-glycan isomers remains challenging. Here we develop a mass spectrometry method, logically derived sequence tandem mass spectrometry (LODES/MSn), to determine the structures of N-glycan isomers that cannot be determined using conventional mass spectrometry. In LODES/MSn, the sequences of successive collision-induced dissociation are derived from carbohydrate dissociation mechanisms and apply to N-glycans in an ion trap for structural determination. We validate LODES/MSn using synthesized N-glycans and subsequently applied this method to N-glycans extracted from soybean, ovalbumin, and IgY. Our method does not require permethylation, reduction, and labeling of N-glycans, or the mass spectrum databases of oligosaccharides and N-glycan standards. Moreover, it can be applied to all types of N-glycans (high-mannose, hybrid, and complex), as well as the N-glycans degraded from larger N-glycans by any enzyme or acid hydrolysis.

Unusual transformation of the mechanically induced monodomain state to the polydomain one in polar nematic liquid crystals of aromatic polyesters.

We present an interesting phenomenon of the mechanically aligned monodomain state of polar nematic liquid crystals transforming into the polydomain one. This unusual transformation may result from mismatching of the dipolar vectors. By stretching or shear-flowing the polar nematic liquid crystal, the perfect orientation can be achieved with respect to the long molecular axis, but the misorientation exists with respect to the polar vector. After the prolonged annealing, then, the free energy of the molecules is minimized by producing new defects which satisfy the continuity of polar orientation, but lead to the loss of macroscopic molecular orientation.