An entirely carbohydrate-based immunogen consisting of a zwitterionic polysaccharide (ZPS) PS A1 and the well-known tumor antigen Tn has been designed, synthesized, and studied for immunological effects. The PS A1 motif was included to act as an MHCII elicitor for a T-cell-dependent immune response with increased immunogenicity against tumor-associated carbohydrate antigens, providing an alternative to carrier proteins. Through the use of C57BL/6 mice, it has been shown that chemical modification of PS A1 does not alter the recognition sequence responsible for an MHCII-mediated, T-cell-dependent immune response. The Tn-PS A1 conjugate construct confers specificity toward the Tn antigen alone, and specific carbohydrate immunoglobulins, namely, IgG3, are generated from intraperitoneal immunizations with or without adjuvant. The properties of the vaccine candidate are attributed to a site-specific linking strategy that incurs significant incorporation of Tn antigen.

Hypochlorous acid (HOCl) is generated by myeloperoxidase (MPO), using chloride and hydrogen peroxide as substrate. HOCl and its conjugate base (OCl−) bind to the heme moiety of hemoglobin (Hb) and generate a transient ferric species whose formation and decay kinetics indicate it can participate in protein aggregation and heme destruction along with subsequent free iron release. The oxidation of Hb heme moiety by OCl− was accompanied by marked heme destruction as judged by the decrease and subsequent flattening of the Soret absorbance peak at 405 nm. HOCl-mediated Hb heme depletion was confirmed by HPLC analysis and in-gel heme staining. Exposure of Hb to increasing concentrations of HOCl produced a number of porphyrin degradation products resulting from oxidative cleavage of one or more of the carbon-methene bridges of the tetrapyrrole ring, as identified by their characteristic HPLC fluorescence and LC-MS. A non-reducing denaturing SDS PAGE showed several degrees of protein aggregation. Similar, porphyrin degradation products were identified after exposure of red blood cells to increasing concentration of HOCl indicating biological relevance of this finding. This work provides a direct link between Hb heme destruction and subsequent free iron accumulation, as occurs under inflammatory conditions where HOCl is formed in substantial amounts.

With a view to reducing the notorious complexity and irreproducibility of glycosylation reactions, 12 guidelines for the choice of concentration, temperature, and counterions are adumbrated.

Here, we show that hypochlorous acid (HOCl), a potent neutrophil generated oxidant, can mediate destruction of free heme (Ht) and the heme precursor, protoporphyrin IX (PPIX). Ht display a broad Soret peak centered at 365 and 394 nm, indicative of the presence of monomer and μ-oxo-dimer. Oxidation of Ht by HOCl was accompanied by a marked decrease in the Soret absorption peak and release of free iron. Kinetic measurements showed that the Ht-HOCl reaction was triphasic. The first two phases were HOCl concentration dependent and attributable to HOCl binding to the monomeric and dimeric forms. The third phase was HOCl concentration independent, and attributed to Ht destruction with the release of free iron. HPLC and LC-ESIMS analyses of the Ht-HOCl reaction revealed the formation of a number of degradation products, resulting from the cleavage or modification of one or more carbon-methene bridges of the porphyrin ring. Similar studies with PPIX showed that HOCl also mediated tetra-pyrrole ring destruction. Collectively, this work demonstrates the ability of HOCl to modulate destruction of heme, through a process that occurred independent of the iron molecule that resides in the porphyrin center. This phenomenon may play a role in HOCl-mediated oxidative injury in pathological conditions.

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Cancer cells of diverse origins express extracellular tumor-specific carbohydrate antigens (TACAs) because of aberrant glycosylation. Overexpressed TACAs on the surface of tumor cells are considered biomarkers for cancer detection and have always been prioritized for the development of novel carbohydrate-based anti-cancer vaccines. In recent years, progress has been made in developing synthetic, carbohydrate-based antitumor vaccines to improve immune responses associated with targeting these specific antigens. Tumor cells also exhaust more energy for proliferation than normal cells, by consuming excessive amounts of glucose via overexpressed sugar binding or transporting receptors located in the cellular membrane. Furthermore, inspired by the Warburg effect, glycoconjugation strategies of anticancer drugs have gained considerable attention from the scientific community. This review highlights a small cohort of recent efforts which have been made in carbohydrate-based cancer treatments, including vaccine design and the development of glycoconjugate prodrugs, glycosidase inhibiting iminosugars, and early cancer diagnosis.

A catalytic asymmetric Passerini reaction using tridentate indan (pybox) Cu(II) Lewis acid complex 4 with substrates capable of bidentate coordination has been achieved. The reaction occurs via ligand-accelerated catalysis.Strategies, reagents, and catalysts that enable systematic stereochemical and skeletal variation are central to effective diversity-oriented syntheses (DOS). [1][2][3][4] The Passerini threecomponent coupling reaction (P-3CCR) (coupling of a carbonyl compound and an isocyanide with a carboxylic acid to form an α-acyloxycarboxamide) increases structural complexity; however, methods to control the stereochemical outcome of the carbon-carbon bond when simple achiral substrates are used are currently limited. Although several diastereoselective examples have been described that use chiral auxiliaries or chiral substrates to direct the α-addition of isocyanides, 5 analogous enantioselective examples using chiral catalysts, which involve only one step, are less common. 6,7 Herein, we report the development of a catalytic asymmetric P-3CCR giving rise to α-acyloxycarboxamides enantioselectively.Passerini reactions performed in organic solvents are often sluggish and afford products in low yields unless either highly acidic carboxylic acids or unusually electrophilic carbonyl compounds are used. In contrast, electrophilic iminium ions, formed in situ from the corresponding four-component Ugi reactions undergo a more facile α-isocyanide addition. Since these findings underscore the importance of carbonyl activation we initially sought to use chiral Lewis acid chelation control with Cu(II)-derived Lewis acids to control the © 2004 American Chemical Society Correspondence to: Stuart L. Schreiber, stuart_schreiber@harvard.edu. Supporting Information Available: General experimental procedures, characterization data, and an X-ray crystallographic file (CIF). This material is available free of charge via the Internet at http://pubs.acs.org. Our approach uses a Cu(II) complex and bidentate coordination with carbonyl substrates as a means to invoke stereocontrol of the newly formed C-C bond. Initial studies used bidentate (S,S)-bis(oxazolinyl) (box) (1 and 2)-Cu(II) and tridentate bis(oxazolinyl)pyridine (pybox) (3 and 4)-Cu(II) complexes. 8,10 The reactions were performed in the presence of benzoic acid (5), (benzyloxy)acetaldehyde (6), and p-methoxyphenyl isocyanide (7) ( Table 1). The ligand screen revealed that bispybox 4, derived from (1S,2R)-aminoindanol, was able to control the α-addition of the isocyanide with superior enantioselectivity and yield (entry 7, Table 1). NIH Public AccessThe Cu(II) complex was stirred in methylene chloride until a homogeneous solution was obtained. When the SbF 6 − complexes 1b, 2b, and 3b were used, a homogeneous solution was difficult to achieve, even after filtration through a GHP Acrodisc 13 0.20 μm filter.(Benzyloxy)acetaldehyde (6) was then added to the solution, which was cooled to 0 °C. AW-300 MS (molecular sieves) were added to this solution followed by c...

Carbohydrates are regarded as promising targets for vaccine development against infectious disease because cell surface glycans on many infectious agents are attributed to playing an important role in pathogenesis. In addition, oncogenic transformation of normal cells, in many cases, is associated with aberrant glycosylation of the cell surface glycan generating tumor associated carbohydrate antigens (TACAs). Technological advances in glycobiology have added a new dimension to immunotherapy when considering carbohydrates as key targets in developing safe and effective vaccines to combat cancer, bacterial infections, viral infections, etc. Many consider effective vaccines induce T-cell dependent immunity with satisfactory levels of immunological memory that preclude recurrence. Unfortunately, carbohydrates alone are poorly immunogenic as they do not bind strongly to the MHCII complex and thus fail to elicit T-cell immunity. To increase immunogenicity, carbohydrates have been conjugated to carrier proteins, which sometimes can impede carbohydrate specific immunity as peptide-based immune responses can negate antibodies directed at the targeted carbohydrate antigens. To overcome many challenges in using carbohydrate-based vaccine design and development approaches targeting cancer and other diseases, zwitterionic polysaccharides (ZPSs), isolated from the capsule of commensal anaerobic bacteria, will be discussed as promising carriers of carbohydrate antigens to achieve desired immunological responses.