Experimental investigations of ice recrystallization inhibition (IRI) efficacy have been performed for a large number of different substances, including natural antifreeze proteins (AFP) and antifreeze glycoproteins (AFGP), several synthetic AFGP analogues, as well as synthetic polymers. Here we define IRI efficacy as that concentration at which the ice recrystallization rate is dominated by the IRI compound. The investigated 39 compounds show IRI efficacies from about 2 mmol L-1 for the least effective compound still showing activity to about 1 nmol L-1, which corresponds to the highest efficacy found for natural AFGP samples. Hence, the assay employed allows for a quantitative comparison of IRI efficacy over a range of at least 6 orders of magnitude, thereby enabling studies of distinguishing effects induced by even subtle structural variations in AFGP analogues that were synthesized. Our results show that AFGP are by far the most effective IRI agents in our assay, and we surmise that this particular efficacy may be due to their disaccharide moieties. This supposition is supported by the fact that IRI efficacy is strongly reduced for monosaccharide AFGP analogues, as well as for AFGP analogues with acetyl-protected monosaccharide moieties.

Glycosylation of proteins plays an important role in molecular recognition among proteins with implications for a variety of cellular processes. The large amount of glycan variants enables interactions of exquisite specificity. Glycoproteins often are partially or fully disordered and intrinsically unstructured regions in proteins are known for mediating many protein-protein or protein-nucleotide interactions during regulation of transcription, translation, and cellular signal transduction. The question arises how conjugated glycans influence protein and peptide conformational dynamics and by that modify their biological activity. We compare the conformational dynamics of unstructured polypeptides consisting of eight glycine-serine repeat units with and without glycosylated serine units. We synthesized glycine-serine repeats with O-conjugated beta-galactose at every serine residue by solid-phase synthesis with glycosylated dipeptides as building blocks. Introducing an organic oxazine dye and tryptophan at either end of these peptides allows measurements of end-to-end contact kinetics. Upon van-der-Waals contact between dye and tryptophan fluorescence is quenched by photo induced electron transfer (PET). Fluorescence intensity fluctuations are analyzed using fluorescence correlation spectroscopy (FCS) and contact formation rate constants are determined. We studied influences from solvent viscosity and temperature on end-to-end contact formation rates and found a decrease of rate constants upon glycosylation. Arrhenius analysis of end-to-end contact rates yields enhanced activation energy for the glycosylated sample. The viscosity dependence of the relaxation rates shows that contact formation still is viscosity controlled. This study confirms previous reports that glycosylation has a significant influence on peptide dynamics mostly through steric hindrance.

With a twist: The conformational dynamics of glycosylated glycine–serine peptides is studied using contact- induced fluorescence quenching analysed by fluorescence correlation spectroscopy. End-to-end contact rates on ns–μs timescales reveal enthalpic and entropic contributions to the reduction of contact formation rates in glycopeptides (see picture). Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

In Arctic and Antarctic marine regions, where the temperature declines below the colligative freezing point of physiological fluids, efficient biological antifreeze agents are crucial for the survival of polar fish. One group of such agents is classified as antifreeze glycoproteins (AFGP) that usually consist of a varying number (n = 4–55) of [AAT] n -repeating units. The threonine side chain of each unit is glycosidically linked to β-d-galactosyl-(1 → 3)-α-N-acetyl-d-galactosamine. These biopolymers can be considered as biological antifreeze foldamers. A preparative route for stepwise synthesis of AFGP allows for efficient synthesis. The diglycosylated threonine building block was introduced into the peptide using microwave-enhanced solid phase synthesis. By this versatile solid phase approach, glycosylated peptides of varying sequences and lengths could be obtained. Conformational studies of the synthetic AFGP analogs were performed by circular dichroism experiments (CD). Furthermore, the foldamers were analysed microphysically according to their inhibiting effect on ice recrystallization and influence on the crystal habit.

A simple one-pot azidochlorination for the preparation of nitrogen-containing Koenigs-Knorr glycosyl donors proceeds upon reaction of protected glycals with sodium azide, ferric chloride, and hydrogen peroxide. Different mono- and disaccharide galactals and glucals are converted in a highly α-selective manner to the 2-azido glycosyl chlorides. Starting from disaccharide galactals, building blocks for the synthesis of the T-antigen are obtained in a straightforward manner. The simplicity of the reaction conditions allows for an efficient and scalable α-selective synthesis of 2-azido substituted glycosyl chlorides.

AbstractA simple, efficient, and α‐selective method to prepare synthetically important 2‐azido glycosyl chlorides is reported.

This paper highlights recent advances in synthesis, self-assembly and sensing applications of monodisperse magnetic Co and Co-alloyed nanoparticles. A brief introduction to solution phase synthesis techniques as well as the magnetic properties and aspects of the self-assembly process of nanoparticles will be given with the emphasis placed on selected applications, before recent developments of particles in sensor devices are outlined. Here, the paper focuses on the fabrication of granular magnetoresistive sensors by the employment of particles themselves as sensing layers. The role of interparticle interactions is discussed.