The CuAAC “click” reaction has developed as one of the most useful and widely employed reactions in ligation within polymer chemistry. This is due to the unique properties of the Cu(I) catalysis ...which renders the reaction quantitative even at low concentrations, orthogonal with other chemistries and extremely robust. The formed triazole on the other hand is of intermediate polarity and chemically and biochemically “invisible”, and the CuAAC provides the ideal “click” reaction for stitching together polymer architectures of unprecedended complexity as was it molecular LEGO. The CuAAC “clicking” in polymer chemistry is increasing exponentially and lead to highly defined polymer materials with novel properties.
The properties of biosensors, biomedical implants, and other materials based on immobilized proteins greatly depend on the method employed to couple the protein molecules to their solid support. ...Covalent, site-specific immobilization strategies are robust and can provide the level of control that is desired in this kind of application. Recent advances include the use of enzymes, such as sortase A, to couple proteins in a site-specific manner to materials such as microbeads, glass, and hydrogels. Also, self-labeling tags such as the SNAP-tag can be employed. Last but not least, chemical approaches based on bioorthogonal reactions, like the azide-alkyne cycloaddition, have proven to be powerful tools. The lack of comparative studies and quantitative analysis of these immobilization methods hampers the selection process of the optimal strategy for a given application. However, besides immobilization efficiency, the freedom in selecting the site of conjugation and the size of the conjugation tag and the researcher's expertise regarding molecular biology and/or chemical techniques will be determining factors in this regard.
Click into place: Tachyplesin‐I (TP‐I) analogues in which both disulfide bridges (1) have been replaced with triazoles (2) represent structural mimetics of TP‐I that display similar or slightly ...improved antibacterial activity. Optimized structures were obtained by replacing the cysteine residues in TP‐I by azido‐ and alkyno‐functionalized amino acids.
Transmission electron microscopic image of iron isomaltoside 1000.
The treatment of iron deficiency anemia with polynuclear iron formulations is an established therapy in patients with chronic kidney ...disease but also in other disease areas like gastroenterology, cardiology, oncology, pre/post operatively and obstetrics’ and gynecology. Parenteral iron formulations represent colloidal systems in the lower nanometer size range which have traditionally been shown to consist of an iron core surrounded by a carbohydrate shell. In this publication, we for the first time describe the novel matrix structure of iron isomaltoside 1000 which differs from the traditional picture of an iron core surrounded by a carbohydrate. Despite some structural similarities between the different iron formulations, the products differ significantly in their physicochemical properties such as particle size, zeta potential, free and labile iron content, and release of iron in serum. This study compares the physiochemical properties of iron isomaltoside 1000 (Monofer®) with the currently available intravenous iron preparations and relates them to their biopharmaceutical properties and their approved clinical applications. The investigated products encompass low molecular weight iron dextran (CosmoFer®), sodium ferric gluconate (Ferrlecit®), iron sucrose (Venofer®), iron carboxymaltose (Ferinject®/Injectafer®), and ferumoxytol (Feraheme®) which are compared to iron isomaltoside 1000 (Monofer®). It is shown that significant and clinically relevant differences exist between sodium ferric gluconate and iron sucrose as labile iron formulations and iron dextran, iron carboxymaltose, ferumoxytol, and iron isomaltoside 1000 as stable polynuclear formulations. The differences exist in terms of their immunogenic potential, safety, and convenience of use, the latter being expressed by the opportunity for high single-dose administration and short infusion times. Monofer is a new parenteral iron product with a very low immunogenic potential and a very low content of labile and free iron. This enables Monofer, as the only IV iron formulation, to be administered as a rapid high dose infusion in doses exceeding 1000
mg without the application of a test dose. This offers considerable dose flexibility, including the possibility of providing full iron repletion in a single infusion (one-dose iron repletion).
A method to express, purify and modify the Peptidyl-Lys metallopeptidase (LysN) ofArmillaria melleainPichia pastoriswas developed to enable functional studies of the protease. Based on prior work, we ...propose a mechanism of action of LysN. Catalytic residues were investigated by site-directed mutagenesis. As anticipated, these mutations resulted in significantly reduced catalytic rates. Additionally, based on molecular modelling eleven mutants were designed to have altered substrate specificity. The S1' binding pocket of LysN is quite narrow and lined with negative charge to specifically accommodate lysine. To allow for arginine specificity in S1', it was proposed to extend the S1' binding pocket by mutagenesis, however the resulting mutant did not show any activity with arginine in P1'. Two mutants, A101D and T105D, showed increased specificity towards arginine in subsites S2'-S4' compared to the wild type protease. We speculate that the increased specificity to result from the additional negative charge which attract and interact with positively charged residues better than the wild type.
Semiconductor nanowires (NWs) are gaining significant importance in various biological applications, such as biosensing and drug delivery. Efficient and controlled immobilization of biomolecules on ...the NW surface is crucial for many of these applications. Here, we present for the first time the use of the CuI‐catalyzed alkyne–azide cycloaddition and its strain‐promoted variant for the covalent functionalization of vertical NWs with peptides and proteins. The potential of the approach was demonstrated in two complementary applications of measuring enzyme activity and protein binding, which is of general interest for biological studies. The attachment of a peptide substrate provided NW arrays for the detection of protease activity. In addition, green fluorescent protein was immobilized in a site‐specific manner and recognized by antibody binding to demonstrate the proof‐of‐concept for the use of covalently modified NWs for diagnostic purposes using minute amounts of material.
Click on nanowires: A method for highly reproducible, covalent functionalization of oxidized semiconductor nanowires with peptides and proteins is reported. The method combines silanization with the CuI‐catalyzed and strain‐promoted alkyne–azide cycloaddition (CuAAC and SPAAC) reactions. A protease FRET substrate and green fluorescent protein were site‐specifically immobilized on GaAs nanowires.
UDP-GalNAc:polypeptide α-N-acetylgalactosaminyltransferases (GalNAc-Ts) constitute a family of up to 20 transferases that initiate mucin-type O-glycosylation. The transferases are structurally ...composed of catalytic and lectin domains. Two modes have been identified for the selection of glycosylation sites by GalNAc-Ts: confined sequence recognition by the catalytic domain alone, and concerted recognition of acceptor sites and adjacent GalNAc-glycosylated sites by the catalytic and lectin domains, respectively. Thus far, only the catalytic domain has been shown to have peptide sequence specificity, whereas the primary function of the lectin domain is to increase affinity to previously glycosylated substrates. Whether the lectin domain also has peptide sequence selectivity has remained unclear. Using a glycopeptide array with a library of synthetic and recombinant glycopeptides based on sequences of mucins MUC1, MUC2, MUC4, MUC5AC, MUC6, and MUC7 as well as a random glycopeptide bead library, we examined the binding properties of four different lectin domains. The lectin domains of GalNAc-T1, -T2, -T3, and -T4 bound different subsets of small glycopeptides. These results indicate an additional level of complexity in the initiation step of O-glycosylation by GalNAc-Ts.
The structure of D‐amino acid hexapeptides that promote cellular adhesion was determined by screening D‐amino acid hexapeptide libraries synthesized on otherwise inert beaded PEGA resin. These new ...adhesion molecules provide a completely stable cellular environment and facilitate the maintenance of a monolayer of cells on beads for extended periods. The presence of the peptides promotes spreading of the cells on the bead surface. Not surprisingly, the molecules contained a significant number of arginines and/or lysines. However, the exact structure of each peptide is quite important for the degree of adhesion observed, and a motif with three or four basic amino acids spaced within amino acids of intermediate polarity clearly prevailed, for example, k‐l/r‐h‐r‐i/v‐r‐a; this maintains a polar/hydrophobic balance.
Novel adhesion peptides for the growth of cell monolayers on inert surfaces were identified by screening D‐amino acid split‐mix combinatorial libraries. Peptide adhesion was superior to that of poly D‐lysine and allowed a monolayer of nonadhesive HEK293 cells to be established on the surface of PEG‐based polymer beads for on‐bead cellular screening.
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