The relevance of the aldehyde bisulfite toluidine blue reaction and its variants in the submicroscopic carbohydrate research

Exploration of the Sialic Acid World

Sialic acids are cytoprotectors, mainly localized on the surface of cell membranes with multiple and outstanding cell biological functions. The history of their structural analysis, occurrence, and functions is fascinating and described in this review. Reports from different researchers on apparently similar substances from a variety of biological materials led to the identification of a 9-carbon monosaccharide, which in 1957 was designated "sialic acid." The most frequently occurring member of the sialic acid family is N-acetylneuraminic acid, followed by N-glycolylneuraminic acid and O-acetylated derivatives, and up to now over about 80 neuraminic acid derivatives have been described. They appeared first in the animal kingdom, ranging from echinoderms up to higher animals, in many microorganisms, and are also expressed in insects, but are absent in higher plants. Sialic acids are masks and ligands and play as such dual roles in biology. Their involvement in immunology and tumor biology, as well as in hereditary diseases, cannot be underestimated. N-Glycolylneuraminic acid is very special, as this sugar cannot be expressed by humans, but is a xenoantigen with pathogenetic potential. Sialidases (neuraminidases), which liberate sialic acids from cellular compounds, had been known from very early on from studies with influenza viruses. Sialyltransferases, which are responsible for the sialylation of glycans and elongation of polysialic acids, are studied because of their significance in development and, for instance, in cancer. As more information about the functions in health and disease is acquired, the use of sialic acids in the treatment of diseases is also envisaged.

Polarization optical-histochemical characterization and supramolecular structure of carbohydrate fibrils

Topo-optical staining reactions were used to investigate the structures of bacterial cellulose, insect chitosan and alginic acid from brown algae. Polysaccharide complexes, glycosaminoglycans and sulfate groups were presented and demonstrated selectively. Chitosan and alginic acid are structurally similar to glycosaminoglycans (GAGs), which are constituents of human amyloid fibrils. The staining sequences shown can be used as reliable methods for histochemistry with light and polarization microscopy. They will help to clarify the complex protein-polysaccharide structure of amyloid fibrils.

Simple and high yielding method for preparing tissue specific extracellular matrix coatings for cell culture

BACKGROUND

The native extracellular matrix (ECM) consists of a highly complex, tissue-specific network of proteins and polysaccharides, which help regulate many cellular functions. Despite the complex nature of the ECM, in vitro cell-based studies traditionally assess cell behavior on single ECM component substrates, which do not adequately mimic the in vivo extracellular milieu.

METHODOLOGY/PRINCIPAL FINDINGS

We present a simple approach for developing naturally derived ECM coatings for cell culture that provide important tissue-specific cues unlike traditional cell culture coatings, thereby enabling the maturation of committed C2C12 skeletal myoblast progenitors and human embryonic stem cells differentiated into cardiomyocytes. Here we show that natural muscle-specific coatings can (i) be derived from decellularized, solubilized adult porcine muscle, (ii) contain a complex mixture of ECM components including polysaccharides, (iii) adsorb onto tissue culture plastic and (iv) promote cell maturation of committed muscle progenitor and stem cells.

CONCLUSIONS

This versatile method can create tissue-specific ECM coatings, which offer a promising platform for cell culture to more closely mimic the mature in vivo ECM microenvironment.

Confocal fluorescence detected linear dichroism imaging of isolated human amyloid fibrils. Role of supercoiling

Amyloids are highly organized insoluble protein aggregates that are associated with a large variety of degenerative diseases. In this work, we investigated the anisotropic architecture of isolated human amyloid samples stained with Congo Red. This was performed by fluorescence detected linear dichroism (FDLD) imaging in a laser scanning confocal microscope that was equipped with a differential polarization attachment using high frequency modulation of the polarization state of the laser beam and a demodulation circuit. Two- and three-dimensional FDLD images of amyloids provided information on the orientation of the electric transition dipoles of the intercalated Congo Red molecules with unprecedented precision and spatial resolution. We show that, in accordance with linear dichroism imaging (Jin et al. Proc Natl Acad Sci USA 100:15294, 2003), amyloids exhibit strong anisotropy with preferential orientation of the dye molecules along the fibrils; estimations on the orientation angle, of around 45°, are given using a model calculation which takes into account the helical organization of the filaments and fibrils. Our data also show that FDLD images display large inhomogeneities, high local values with alternating signs and, in some regions, well identifiable µm-sized periodicities. These features of the anisotropic architecture are accounted for by supercoiling of helically organized amyloid fibrils.