Optimal Synthetic Glycosylation of a Therapeutic Antibody.

Glycosylation patterns in antibodies critically determine biological and physical properties but their precise control is a significant challenge in biology and biotechnology. We describe herein the optimization of an endoglycosidase-catalyzed glycosylation of the best-selling biotherapeutic Herceptin, an anti-HER2 antibody. Precise MS analysis of the intact four-chain Ab heteromultimer reveals nonspecific, non-enzymatic reactions (glycation), which are not detected under standard denaturing conditions.

Chemoenzymatic Synthesis of a Phosphorylated Glycoprotein.

The majority of lysosomal enzymes are targeted to the lysosome by post-translational tagging with N-glycans terminating in mannose-6-phosphate (M6P) residues. Some current enzyme replacement therapies (ERTs) for lysosomal storage disorders are limited in their efficacy by the extent to which the recombinant enzymes bear the M6P-terminated glycans required for effective trafficking. Chemical synthesis was combined with endo-β-N-acetylglucosaminidase (ENGase) catalysis to allow the convergent synthesis of glycosyl amino acids bearing M6P residues.

Optimal Synthetic Glycosylation of a Therapeutic Antibody.

Glycosylation patterns in antibodies critically determine biological and physical properties but their precise control is a significant challenge in biology and biotechnology. We describe herein the optimization of an endoglycosidase-catalyzed glycosylation of the best-selling biotherapeutic Herceptin, an anti-HER2 antibody. Precise MS analysis of the intact four-chain Ab heteromultimer reveals nonspecific, non-enzymatic reactions (glycation), which are not detected under standard denaturing conditions.

Modification of fulleropyrazolines modulates their cleavage by light.

The extraordinary electrochemistry and the tunability of their energy levels allows the use of fulleropyrazolines in photovoltaics and charge-transfer systems. Here we show that substitution in position 1 tunes photolytic stability; electron-donating groups facilitate 1,3-dipolar cycloreversion to fullerene. This discovery has implications not only for photovoltaic stability but also highlights a potential strategy for photo-controlled fullerene release systems ('photo-caged'/'photo-activated' fullerene).

Rationally designed short polyisoprenol-linked PglB substrates for engineered polypeptide and protein N-glycosylation.

The lipid carrier specificity of the protein N-glycosylation enzyme C. jejuni PglB was tested using a logical, synthetic array of natural and unnatural C10, C20, C30, and C40 polyisoprenol sugar pyrophosphates, including those bearing repeating cis-prenyl units. Unusual, short, synthetically accessible C20 prenols (nerylnerol 1d and geranylnerol 1e) were shown to be effective lipid carriers for PglB sugar substrates.

Total synthesis of kottamide E.

The first synthesis of kottamide E, a marine natural product containing a 5,6-dibromoindole linked via a (Z)-enamide to an unusual 1,2-dithiolane-containing amino acid, is reported.

Synthesis of the trans-hydrindane core of dictyoxetane.

A concise, stereoselective synthesis of the trans-hydrindane core of the marine natural product dictyoxetane is reported, starting from a Robinson annelation derived bicyclic enone. A phosphorane-mediated, pinacol-like rearrangement of a cis-diol, via a formal 1,2-hydride shift, is used to establish the requisite trans ring junction. (31)P NMR supports the formation of the intermediate phosphorane, generated in situ from the reaction of a diol with Ph(3)PCl(2).

Inhibition of the pneumococcal virulence factor StrH and molecular insights into N-glycan recognition and hydrolysis.

The complete degradation of N-linked glycans by the pathogenic bacterium Streptococcus pneumoniae is facilitated by the large multimodular cell wall-attached exo-β-D-N-acetylglucosaminidase StrH. Structural dissection of this virulence factor using X-ray crystallography showed it to have two structurally related glycoside hydrolase family 20 catalytic domains, which displayed the expected specificity for complex N-glycans terminating in N-acetylglucosamine but exhibited unexpected differences in their preferences for the substructures present in these glycans. The structures of the two catalytic domains in complex with unhydrolyzed substrates, including an N-glycan possessing a bisecting N-acetylglucosamine residue, revealed the specific architectural features in the active sites that confer their differential specificities.

Regioselective dibromination of methyl indole-3-carboxylate and application in the synthesis of 5,6-dibromoindoles.

Treatment of methyl indole-3-carboxylate with bromine in acetic acid gives methyl 5,6-dibromoindole-3-carboxylate regioselectively, from which the parent 5,6-dibromoindole can be accessed via a one-pot, microwave-mediated ester hydrolysis and decarboxylation. Application of these building blocks in syntheses of natural and non-natural 5,6-dibromoindole derivatives, including meridianin F and 5,6-dibromo-2'-demethylaplysinopsin, is reported.

Unique N-glycan moieties of the 66-kDa cell wall glycoprotein from the red microalga Porphyridium sp.

We report here the structural determination of the N-linked glycans in the 66-kDa glycoprotein, part of the unique sulfated complex cell wall polysaccharide of the red microalga Porphyridium sp. Structures were elucidated by a combination of normal phase/reverse phase HPLC, positive ion MALDI-TOF MS, negative ion electrospray ionization, and MS/MS. The sugar moieties of the glycoprotein consisted of at least four fractions of N-linked glycans, each composed of the same four monosaccharides, GlcNAc, Man, 6-O-MeMan, and Xyl, with compositions Man(8-9)Xyl(1-2)Me(3)GlcNAc(2).

Streptococcus pneumoniae endohexosaminidase D; feasibility of using N-glycan oxazoline donors for synthetic glycosylation of a GlcNAc-asparagine acceptor.

Endohexosaminidase D, a family 85 glycoside hydrolase from S. pneumoniae and the first endohexosaminidase to be discovered, is found to be capable of catalysing the glycosylation of a glycosyl amino acid bearing a GlcNAc residue using a variety of N-glycan oxazoline donors. Although enzyme-catalysed oxazoline hydrolysis is a significant competing reaction that is not countered by the addition of organic co-solvents or variation of reaction pH, a high yielding synthetic process can be achieved by the sequential addition of multiple equivalents of oxazoline donor, demonstrating the synthetic potential of this enzyme as a biocatalyst for the synthesis of defined glycoconjugates.

Endohexosaminidase-catalysed glycosylation with oxazoline donors: effects of organic co-solvent and pH on reactions catalysed by Endo A and Endo M.

The synthetic efficiency of endohexosaminidase-catalysed glycosylation reactions using N-glycan oxazolines as donors was investigated as two reaction parameters were varied. Both the addition of quantities of an organic co-solvent and modulation of reaction pH between 6.5 and 8.

Synthesis, structures, and DFT bonding analysis of new titanium hydrazido(2-) complexes.

The reaction of 1,1-diphenylhydrazine with Ti(NMe2)2Cl2 produced the monomeric terminal titanium hydrazido(2-) species Ti(NNPh2)Cl2(HNMe2)2 (1) in near-quantitative yield. The reaction of Ti(NMe2)2Cl2 with the less sterically demanding ligand precursors 1,1-dimethylhydrazine or N-aminopiperidine gave the dimeric mu-eta2,eta1-bridged compounds Ti2(mu-eta2,eta1-NNMe2)2Cl4(HNMe2)2 (2) and Ti2[mu-eta2,eta1-NN(CH2)5]2Cl4(HNMe2)3 (3). The X-ray structures of 2 and 3 showed the formation of N-H.