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The microstructure of an unmodified AlSi9Mg alloy comprises large primary α phase dendrites, eutectic β phase crystals and eutectic α phase. This composition is responsible for the alloy’s low strength parameters, and it limits the extent of practical applications. The mechanical properties of hypoeutectic silumins can be improved through chemical modification as well as traditional or technological processing. Modification improves the mechanical properties of alloys through grain refinement. This study presents the results of double modification of an AlSi9Mg alloy with strontium, boron and titanium. The influence of the analyzed modifiers on the microstructure and mechanical properties of the processed alloy was presented in graphs. The modification of a hypoeutectic AlSi9Mg alloy improved the alloy’s properties. The results of the tests indicate that the mechanical properties of the modified alloy are determined by the sequence in which the components are introduced to the alloy.

The article discusses the effect of distance between submicroscopic oxide impurities (up to 2 μm in size) on the fatigue resistance coefficient of structural steel during rotary bending. The study was performed on 21 heats produced in an industrial plant. Fourteen heats were produced in 140 ton electric furnaces, and 7 heats were performed in a 100 ton oxygen converter. All heats were desulfurized. Furthermore seven heats from electrical furnaces were refined with argon, and heats from the converter were subjected to vacuum circulation degassing.

The article discusses the results of a study investigating the effect of the number of fine non-metallic inclusions (up to 2 µm in size) on the fatigue strength of structural steel during rotary bending. The study was performed on 21 heats produced in an industrial plant. Fourteen heats were produced in 140 ton electric furnaces, and 7 heats were performed in a 100 ton oxygen converter. All heats were desulfurized. Seven heats from electrical furnaces were refined with argon, and heats from the converter were subjected to vacuum circulation degassing.

Non-metallic inclusions found in steel can affect its performance characteristics. Their impact depends not only on their quality, but also, among others, on their size and distribution in the steel volume. The literature mainly describes the results of tests on hard steels, particularly bearing steels. The amount of non-metallic inclusions found in steel with a medium carbon content melted under industrial conditions is rarely presented in the literature. The tested steel was melted in an electric arc furnace and then desulfurized and argonrefined. Seven typical industrial melts were analyzed, in which ca. 75% secondary raw materials were used. The amount of non-metallic inclusions was determined by optical and extraction methods. The test results are presented using stereometric indices. Inclusions are characterized by measuring ranges. The chemical composition of steel and contents of inclusions in every melts are presented. The results are shown in graphical form. The presented analysis of the tests results on the amount and size of non-metallic inclusions can be used to assess them operational strength and durability of steel melted and refined in the desulfurization and argon refining processes.

Lanthanide doped nanoparticles (Ln:NPs) hold promise as novel luminescent probes for numerous applications in nanobiophotonics. Despite excellent photostability, narrowband photoluminescence, efficient anti-Stokes emission and long luminescence lifetimes, which are needed to meet the requirements of multiplexed and background free detection at prolonged observation times, concern about their toxicity is still an issue for both in vivo and in vitro applications. Similar to other chemicals or pharmaceuticals, the very same properties that are desirable and potentially useful from a biomedical perspective can also give rise to unexpected and hazardous toxicities. In engineered bionanomaterials, the potentially harmful effects may originate not only from their chemical composition but also from their small size. The latter property enables the nanoparticles to bypass the biological barriers, thus allowing deep tissue penetration and the accumulation of the nanoparticles in a number of organs. In addition, nanoparticles are known to possess high surface chemical reactivity as well as a large surface-to-volume ratio, which may seriously affect their biocompatibility. Herein we survey the underlying mechanisms of nanotoxicity and provide an overview on the nanotoxicity of lanthanides and of upconverting nanoparticles.

Selective strategies for the construction of novel three component glycoconjugate vaccines presenting Candida albicans cell wall glycan (β-1,2 mannoside) and polypeptide fragments on a tetanus toxoid carrier are described. The first of two conjugation strategies employed peptides bearing an N-terminal thiopropionyl residue for conjugation to a trisaccharide equipped with an acrylate linker and a C-terminal S-acetyl thioglycolyl moiety for subsequent linking of neoglycopeptide to bromoacetylated tetanus toxoid. Michael addition of acrylate trisaccharides to peptide thiol under mildly basic conditions gave a mixture of N- and C- terminal glyco-peptide thioethers. An adaptation of this strategy coordinated S-acyl protection with anticipated thioester exchange equilibria. This furnished a single chemically defined fully synthetic neoglycopeptide conjugate that could be anchored to a tetanus toxoid carrier and avoids the introduction of exogenous antigenic groups. The second strategy retained the N-terminal thiopropionyl residue but replaced the C-terminal S-acetate functionality with an azido group that allowed efficient, selective formation of neoglycopeptide thioethers and subsequent conjugation of these with propargylated tetanus toxoid, but introduced potentially antigenic triazole linkages., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Conjugation of synthetic oligosaccharides and native polysaccharides to proteins is an important tool in glycobiology to create vaccines and antigens to screen lectins, toxins, and antibodies. A novel approach to potentiate and profile the immune response to vaccines involves targeting antigens directly to dendritic cells (DCs), the key cells engaged in the immunization process. Inclusion of a carbohydrate ligand recognized by C-type lectins expressed on their cell surface ensures targeting of vaccines to DCs and improved immunological responses. Here we describe a strategy that permits three sequential orthogonal conjugation reactions to prepare glycoconjugates and apply them to the synthesis of a conjugate vaccine that is targeted for uptake by DCs. The carrier protein is treated with an azo-transfer reagent to convert accessible amino groups to azide and then amide bond formation via reaction with carboxylic acid side chains is used to attach amino tether groups of a ligand to the protein. Azide-alkyne Huisgen cycloaddition conjugation, "click chemistry" is used to attach a second ligand equipped with a propargyl group or an analogous terminal alkyne, and following reduction of protein azide groups back to amine, these amino acid side chains can be subjected to amide formation such as reaction with succinimide esters or homobifunctional coupling reagents such as dialkyl squarate.

In a previous attempt to generate a protective vaccine against Candida albicans, a β-mannan tetanus toxoid conjugate showed poor immunogenicity in mice. To improve the specific activation toward the fungal pathogen, we aimed to target Dectin-1, a pattern-recognition receptor expressed on monocytes, macrophages, and dendritic cells. Laminarin, a β-glucan ligand of Dectin-1, was incorporated into the original β-mannan tetanus toxoid conjugate providing a tricomponent conjugate vaccine. A macrophage cell line expressing Dectin-1 was employed to show binding and activation of Dectin-1 signal transduction pathway by the β-glucan-containing vaccine. Ligand binding to Dectin-1 resulted in the following: 1) activation of Src family kinases and Syk revealed by their recruitment and phosphorylation in the vicinity of bound conjugate and 2) translocation of NF-κB to the nucleus. Treatment of immature bone marrow-derived dendritic cells (BMDCs) with tricomponent or control vaccine confirmed that the β-glucan-containing vaccine exerted its enhanced activity by virtue of dendritic cell targeting and uptake. Immature primary cells stimulated by the tricomponent vaccine, but not the β-mannan tetanus toxoid vaccine, showed activation of BMDCs. Moreover, treated BMDCs secreted increased levels of several cytokines, including TGF-β and IL-6, which are known activators of Th17 cells. Immunization of mice with the novel type of vaccine resulted in improved immune response manifested by high titers of Ab recognizing C. albicans β-mannan Ag. Vaccine containing laminarin also affected distribution of IgG subclasses, showing that vaccine targeting to Dectin-1 receptor can benefit from augmentation and immunomodulation of the immune response.

A disaccharide-chicken serum albumin conjugate vaccine against Candida albicans infections has been developed by reverse engineering a protective monoclonal antibody, C3.1. The binding site of C3.1 binds short oligosaccharides of β1,2-linked mannopyranose residues present in the fungal cell wall phosphomannan. By delineating the fine detail of the molecular recognition of the cell wall β-mannan antigen, a disaccharide epitope was deduced to be the minimum size epitope that should induce the formation of protective antibody. Sequential functional group replacement of disaccharide hydroxyl groups to yield a series of monodeoxy and mono-O-methyl β1,2-linked mannobioside congeners established that three hydroxyl groups are essential for binding. Two of these, O-3 and O-4, are located on the internal mannose residue of the disaccharide, and a third, O-3', is located on the terminal mannose. Synthesis of a series of trisaccharides that mandate binding of either the reducing or nonreducing disaccharide epitopes provided the final indication that a disaccharide protein conjugate should have the potential to induce protective antibody. When disaccharide was conjugated to chicken serum albumin this vaccine produced antibodies in rabbits that recognized the native cell wall phosphomannan. In proof of concept protection experiments, three immunized rabbits showed a reduction in fungal burden when challenged with live C. albicans.

A β-(1 → 2)-linked mannose trisaccharide epitope that is the optimal inhibitor of two protective monoclonal antibodies specific for the Candida albicans cell wall phosphomannan was used to create a synthetic conjugate vaccine. Two injections of the trisaccharide-tetanus toxoid conjugate administered with alum induced a robust secondary antibody response in rabbits with trisaccharide specific IgG ELISA titers in excess of 1:100,000. Fluorescent labeling studies demonstrated these antibodies (i) recognized the cell wall β-mannan of C. albicans on hyphae and budding cells and (ii) C. albicans incubated with immune sera bound complement factor C3. The synthetic conjugate vaccine but not the carrier protein, tetanus toxoid reduced Candida load in vaccinated rabbits subsequently rendered leukocytopenic by injection of cyclophosphamide and then challenged with live C. albicans. These data support the contention that antibody mediated immunity plays a role in combating C. albicans infections and suggests that a surprisingly simple, readily accessible synthetic conjugate vaccine may have therapeutic potential., (Copyright © 2012. Published by Elsevier Ltd.)

The tether employed to covalently attach β-mannan disaccharide glycoconjugates influences the specificity of rabbit antibodies that protect against Candida albicans. Two glycoconjugates containing (1 → 2)-β-mannan disaccharides linked to chicken serum albumin (CSA) either via a structurally uniform or via a stereodiversified spacer were prepared and evaluated in immunization trials in mice and rabbits. Immunization with conjugate vaccine possessing a structurally diversified linker induced higher IgG titers against Candida albicans cell wall phosphomannan than a conjugate with a structurally uniform linker. These results suggest that affinity maturation and the specific antibody response can be shifted towards recognition of the desired hapten by employing a linker with diversified configuration.

A protective β-mannan trisaccharide epitope from the Candida albicans cell wall phosphomannan has been synthesized and activated for copolymerization with acrylamide. The resulting glycopolymer displayed 33 trisaccharide haptens and was derivatized for conjugation to the immunogenic carrier protein, chicken serum albumin. The resulting conjugate achieves a high degree of oligosaccharide substitution while limiting the sites of substitution on the protein. The murine immune response against this conjugate was compared with the response to a trisaccharide-tetanus toxoid conjugate vaccine. The glycopolymer was shown to induce a more robust immune response with higher trisaccharide-specific antibody titers and with a significantly larger proportion of responding mice developing antibodies that bound the target, native cell wall antigen of C. albicans.

Zwitterionic polysaccharides (ZPSs) from Bacteroides fragilis and Streptococcus pneumoniae display unique T-cell activities. The first synthesis of a hexasaccharide representing two repeating units of the zwitterionic capsular polysaccharide from S. pneumoniae type 1 (Sp1) is reported. Key elements of the approach are stereoselective construction of 1,4-cis-alpha-galactose linkages based on a reactive trichloroacetimidate donor that incorporates a 6-O-acetyl group, which may contribute to the high alpha selectivity in glycosylation. After assembly of the fully protected hexasaccharide from five monosaccharide synthons 2-4, 24 and 25, selective deprotection of the primary hydroxyl groups of the four galactose residues followed by oxidation to the corresponding uronic acids provides hexasaccharide 19. The trisaccharide counterpart 1 was synthesized in similar fashion from three synthons, 2-4. This approach employed both conventional and dehydrative glycosylation methodologies and avoids the use of poorly reactive uronic acid derived glycosyl donors and acceptors.

We demonstrate that interactions between multimeric receptors and multivalent ligands are dramatically enhanced by recruiting a complementary templating receptor such as an endogenous multimeric protein but only when individual ligands are attached to a polymer as preorganized, covalent, heterobifunctional pairs. This effect cannot be replicated by a multivalent ligand if the same recognition elements are independently arrayed on the scaffold. Application of this principle offers an approach to create high-avidity inhibitors for multimeric receptors. Judicious selection of the ligand that engages the templating protein allows appropriate effector function to be incorporated in the polymeric construct, thereby providing an opportunity for therapeutic applications. The power of this approach is exemplified by the design of exceptionally potent Escherichia coli Shiga toxin antagonists that protect transgenic mice that constitutively express a human pentraxin, serum amyloid P component.

Replacement of the glycosidic oxygen atom by a sulphur atom is a promising technique for creating glycoconjugates with increased resistance to hydrolysis by endogenous glycosidases. The synthesis and antigenic properties of two distinct (1-->2)-beta-mannan trisaccharides with inter residue-S-linked mannopyranose residues are described. Syntheses were based on an oxidation-reduction strategy to construct the O-linked beta-mannopyranoside bonds and a SN2 inversion to provide 1-thio-beta-mannopyranoside residues. Subsequently the allyl trisaccharide glycosides were subjected to photo addition with cysteine amine and coupled to tetanus toxoid and bovine serum albumin with good efficiency via an adipic acid tether. Rabbit immunization studies revealed that the antibodies elicited by the two glycoconjugates were able to recognize the corresponding O-linked trisaccharide epitope conjugated to BSA and the native cell wall antigen of Candida albicans.

The immunoprotective beta-mannan of Candida albicans occurs as part of the cell wall phosphomannan N-linked glycoprotein. This macromolecule is composed of an extended alpha1,6 linked mannopyranan backbone containing alpha1,2 mannopyranan branches, to which beta1,2 mannopyranan epitopes are attached. The synthesis of beta1,2-mannan disaccharides clustered on a glucose core has been achieved as a way to imitate the multipoint display of beta-mannans in the native glycoprotein. The clustered epitopes were conjugated to tetanus toxoid and bovine serum albumin. Rabbits immunized with tetanus toxoid cluster glycoconjugate gave good antibody titres for the disaccharide cluster or simple trisaccharide epitope (coupled to BSA). The anti-sera also showed strong cross-reactivity with a Candida albicansbeta-mannan cell wall extract. These immunochemical results are compared with data obtained with non-cluster disaccharide and trisaccharide glycoconjugate antigens. The same conjugates gave substantially lower antibody levels when used to immunize mice.

GTP, in physiologic concentration (10(-4) mol/L), enhances cAMP binding to an Mr 57,000 binding protein (BP) in hepatic cytosol, which probably is the phosphorylated receptor subunit of protein kinase II (PK II). When we attempted to separate PK II from other hepatic cytosol proteins by DEAE-cellulose chromatography, we observed that GTP caused little stimulation of [3H]cAMP binding in an eluate fraction (110 to 170 mmol/L KCI), which was rich in PK II but did stimulate cAMP binding to the 210 to 325 mmol/L KCI fraction, which also contains PK II. This suggested that the latter fraction might contain a cofactor necessary for GTP stimulation of cAMP binding, which was lacking in the 110 to 170 mmol/L KCI fraction. Cyclic AMP BP in the 210 to 325 mmol/L fraction was removed by absorption onto cAMP agarose in the presence of 325 mmol/L KCI. When an aliquot of the BP-poor fraction, containing the putative cofactor, was added to the 110 to 170 mmol/L fraction containing PK II, the addition of 10(-4) mol/L GTP to the mixture increased [3H]cAMP binding by more than 80%. Cofactor activity could be extracted from the 210 to 325 mmol/L eluate by adsorption onto cAMP agarose in the presence of 10 mmol/L K phosphate, and eluted with 100 mmol/L KCI, suggesting that the cofactor may bind to the cAMP BP under appropriate circumstances. Addition of this eluted cofactor fraction to the 110 to 170 mmol/L fraction in the presence of 10(-4) mol/L GTP, increased the specific binding of [3H] cAMP more than twofold. Pretreatment of the cofactor fraction with trypsin eliminated this effect.(ABSTRACT TRUNCATED AT 250 WORDS)