The asialoglycoprotein receptor (ASGPR), an endocytotic cell surface receptor expressed by hepatocytes, is triggered by triantennary binding to galactose residues of macromolecules such as asialoorosomucoid (ASOR). The capacity of this receptor to import large molecules across the cellular plasma membrane makes it an enticing target for receptor-mediated drug delivery to hepatocytes and hepatoma cells via ASGPR-mediated endocytosis. This study describes the preparation and characterization of (125)I-ASOR, and its utility in the assessment of ASGPR expression by HepG2, HepAD38 and Huh5-2 human hepatoma cell lines. ASOR was prepared from human orosomucoid, using acid hydrolysis to remove sialic acid residues, then radioiodinated using iodogen. (125)I-ASOR was purified by gel column chromatography and characterized by SDS-PAGE electrophoresis. The ASOR yield by acid hydrolysis was 75%, with approximately 87 % of the sialic acid residues removed. Electrophoresis and gel chromatography demonstrated substantial differences in (125)I-ASOR quality depending on the method of radioiodination. ASGPR densities per cell were estimated at 76,000 (HepG2), 17,000 (HepAD38) and 3,000 (Huh-5-2). (125)I-ASOR binding to ASGPR on HepG2 cells was confirmed through galactose- and EDTA- challenge studies. It is concluded that (125)I-ASOR is a facilely-prepared, stable assay reagent for ASGPR expression if appropriately prepared, and that HepG2 cells, but not HepAD38 or Huh-5-2 cells, are suitable for studies exploiting the endocytotic ASGPR.

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On the basis of previous reports that the natural cofactor pyridoxal 5'-phosphate 1 appears to display cardioprotective properties, a series of novel mimetics of this cofactor were envisioned. As pyridoxal 5'-phosphate is a natural compound and is subject to biological degradation and elimination pathways, the objective was to generate active phosphonates that are potentially less light sensitive and more stable in vivo than the parent vitamer. Several phosphonates were designed and synthesized, and in particular, compounds 10 and 14 displayed similar biological traits to natural phosphate 1 in the rat model of regional myocardial ischemia and reperfusion. A reduction in infarct size was observed in animals treated with these compounds. In an effort to identify other relevant cardioprotective models in order to potentially define structure-activity relationships, these three compounds were tested in the rat working heart model. Compounds 1, 10, and 14 were compared to dichloroacetic acid (DCA) as positive control in this model. As with DCA, compounds 1, 10, and 14 were found to induce a shift from fatty acid oxidation toward glucose oxidation.

[reaction: see text]Because of the vast structural diversity encountered in the field of glycobiology, versatile methods for orthogonal oligosaccharide assembly are always of interest. Reported herein is the preparation of glycosyl chloride donors obtained by reaction of the corresponding thioglycoside precursors with chlorosulfonium chloride reagent 4. The crude chlorides thus obtained can be used directly in subsequent glycosylation reactions, and examples of the generality of this approach are provided.

Use of diethyl phosphorochloridate and Tl(I) thiolates constitutes a general, selective synthesis of thiol esters. Primary, secondary, and tertiary alkane- and arenethiols of various carboxylic acids, including those containing hydroxy groups have been prepared under mild conditions.

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. 58, 131 l(1980).The magnitudes of 180-induced isotope shifts in "C nmr spectra of ketones and aldehydes are dependent on structure and range from about 0.05 ppm to 0.03 ppm for the carbon attached to 180. An increase in negative charge density on the carbonyl oxygen o r conjugation to an aromatic ring reduces the size of the upfield shift. The shifts in [180]alcohols are solvent-dependent, range from 0.03 ppm to 0.01 ppm, and tend to decrease in the order tertiary 2 secondary L primary 2 phenols.

Acid hydrolysis of colominic acid, an a-( 2-»8)-linked oligomer of siaiic acid, yielded Neu5Ac a-( 2-48) Neu5Ac (di-Neu5Ac) 2 as one of the products. Starting from this disaccharide, it was possible to prepare two potential di-Neu5Ac donors, 5 and 8 , as their corresponding 2-chloro derivatives. Subsequent reaction of the donor 8 with methanol as a simple acceptor led to the a -and p-methyl Neu5Ac a-( 2-»8) Neu5Ac glycosides.