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A S Perlin

Publications and source records attributed to A S Perlin.

At least 37 records · Page 2Linked to original sources
PubMed1987

A relationship between 13C-chemical-shift displacements and counterion-condensation theory, in the binding of calcium ion by heparin.

Characteristics of the interaction between heparin and calcium ion in the presence of sodium ion have been examined by monitoring the 13C-chemical shift changes as a function of the calcium ion concentration and the total ionic strength. The results indicated that the association between the polyanion and the divalent cation is a delocalized process, as opposed to one involving specific binding. The correspondence found between chemical shift and the number of Ca2+ ions bound per charged group, as derived from the Manning counterion-condensation model, showed that the stoichiometry is not a constant quantity but, rather, varies throughout the titration, and approaches a limiting value of 2 at high dilution. Additional measurements of T1 and line-width were consistent with an intramolecular order-disorder conformational process induced by the binding of calcium ion. Moreover, binding does not occur or is relatively weak with N-desulfated heparin, or chondroitin 4-sulfate and 6-sulfate, each of which possesses fewer sulfate groups than heparin. These differences serve to emphasize the importance of the charge-density parameter in the control of counterion condensation according to the Manning model, and suggest that the spacing between the negatively charged groups is an associated factor.

Animals↗
PubMed1987

Structural features of sulfated glycans from the tunic of Styela plicata (Chordata-Tunicata). A unique occurrence of L-galactose in sulfated polysaccharides.

The sulfated polysaccharides in the tunic of Styela plicata occur as three fractions that differ markedly in molecular mass and chemical composition. The high-molecular-mass fraction has a high galactose content and a strong negative optical rotation while the low-molecular-mass fractions have a higher proportion of amino sugars and glucose. The galactose occurs in these polysaccharides entirely in the L-enantiomeric form. Although L-galactose is a constituent of several polysaccharides, this is the first report of sulfated polysaccharides that contain high amounts of L-galactose, and that lack the D enantiomorph of this sugar. Furthermore, the structure of the high-molecular-mass fraction, which is composed mainly of a core of alpha-L-galactopyranose residues, sulfated at position 3, linked glycosidically though position 1----4, and with non-sulfated L-galactopyranose non-reducing end-units, is unique among other previously described sulfated glycans. These data are of considerable interest as they show an unusual example of possible variants of polyanionic glycans with structure function in living tissues.

Animals↗
PubMed1986

N.m.r. spectroscopic observations related to the function of sulfate groups in heparin. Calcium binding vs. biological activity.

Chemically-modified heparins containing different combinations of N- and O-sulfate groups were prepared. Characterized by high field 1H- and 13C-n.m.r. spectroscopy, the polymers exhibited chemical shift variations in general accord with shielding differences expected on removal of sulfate substituents, and additional variations that probably arose from conformational changes in the polymers. Whereas the anticoagulant activity of heparins, as measured by USP, anti-Xa, and thrombin-time assays, was invariably reduced by the chemical transformations effected, the ability of heparin to bind calcium ions was found to be dependent on retention of the 2-sulfamino group, whether or not O-sulfate groups were present. The results suggest that the 2-sulfamino group is essential for maintaining a molecular conformation consistent with the ability for the L-iduronic acid residues to complex with calcium ions. Also, they show that although the anticoagulant and calcium-binding properties of heparin may be interdependent, they are not determined by the same structural entities in the polymer.

Animals↗
PubMed1977

Adenosine-5'-d: rotational conformation of the 5'-carbinol group.

A synthesis of adenosine-5'-d (4), and its p.m.r. spectral characteristics, are described. The presence of deuterium in 4 gives rise to a 2:1 mixture of R and S configurations at C-5, thereby permitting specific assignments for the resonances of the residual 5'-protons. From the observed spin-spin coupling between the latter and H-4', an estimate has been made of the rotamer population of the exocyclic 5'-carbinol group. It is shown that the gauche-gauche rotamer is preponderant (approximately 70%) and the gauche-trans one of minor importance (approximately 20%) in aqueous solution, which contrasts markedly with the preference for the latter rotamer exhibited by adenosine in the solid state.

Adenosine↗
PubMed1976

The isolation and characterization of bilirubin diglucuronide, the major bilirubin conjugate in dog and human bile.

The chemical structure of the major conjugate of bilirubin was unequivocally elucidated by structural analysis. The conjugated bilirubins were first separated from the lipid components of human duodenal aspirates or dog gall-bladder bile, and then resolved by t.l.c. into a series of tetrapyrroles. The major tetrapyrrole was then converted into its more stable dipyrrolic azo derivative for further analysis. The conjugated moiety of the azopigment was characterized after methanolysis with sodium methoxide. This reaction yields two types of product, those soluble in water and those soluble in organic solvents. The organic-soluble fraction was shown by t.l.c. and mass spectrometry to contain the methyl esters of the dipyrrolic azo derivatives of bilirubin. The water-soluble materials were analysed by enzymic procedures, t.l.c., n.m.r. spectrometry and combined g.l.c. and mass spectrometry. This analysis showed that the only water-soluble product resulting from the methanolysis was glucuronic acid. The structure was identical with that of pure standards, on both mass spectrometry and n.m.r. spectroscopy. No contaminating moieties were found. Quantitative measurement indicated that the glucuronic acid had been released in a 1:1 molar ratio with the resulting methyl esters of the dipyrrolic azo derivatives of bilirubin. This unequivocally establishes bilirubin diglucuronide as the major pigment present in bile. Past problems with identification of bilirubin diglucuronide were shown to originate from procedures which resulted in incomplete separation and isolation of the azopigments of the conjugated bilirubins, owing to contamination by biliary lipids.

Animals↗
PubMed1976

A 13C-N.M.R. spectral study of chondroitin sulfates A, B, and C: evidence of heterogeneity.

Chondroitin sulfates A, B, and C produce well-resolved 13C-n.m.r. spectra which allow for a more complete characterization than that available from their p.m.r. spectra. The 13C data fully support earlier evidence as to the main structural features of these glycosaminoglycans, but they also show that many chondroitin preparations are substantially heterogeneous in composition. Thus, spectra of chondroitin A and C have the appearance of composites representative of both types of polymer: specimens of A may contain 25% of the C-type of structural sequence, and C,30% of the A-type of sequence; 10-20% of unidentified constituents, including a residue bearing a 6-sulfate group, are present in the specimens of chondroitin B. Chemical-shift and 1JC-H values found for the L-iduronic acid residues of chondroitin B, as well as the effect of gadolinium nitrate on the relaxation properties of its 13C nuclei, indicate that this moiety possesses the alpha configuration and favors the 1C4(L) conformation. Corresponding data for the acetamidodeoxy-D-galactose and D-glucuronic acid residues of the chondroitins are consistent with the beta-anomeric configuration and 4C1(D) conformation in all instances.

Acetylgalactosamine↗
PubMed1974

The isolation of an azobilirubin beta-D-monoglucoside from dog gall-bladder bile.

An ethyl anthranilate azopigment of bilirubin conjugated to beta-d-monoglucoside was isolated from dog gall-bladder bile. Glucose was cleaved from the azopigment by treatment with beta-glucosidase and beta-glucuronidase. Mild alkaline hydrolysis of the compound by sodium methoxide yielded two kinds of compounds, water-soluble and organic-soluble. The former were shown, by enzymic analysis, t.l.c., nuclear magnetic resonance, and combined g.l.c. and mass spectrometry, to contain glucose. No evidence was obtained from these data that a disaccharide was present in this fraction. The organic-soluble compounds formed during this methanolysis were shown, by t.l.c. and mass spectrometry, to be the isomeric dipyrrole azopigments of bilirubin. These findings contribute further evidence to the controversy surrounding the nature of conjugated bilirubin.

Animals↗