Structure of the d-galactan isolated from aloe barbadensis miller

Hot-water extraction of the pulp obtained by dehydrating the jelly of the fleshy leaves of Aloe barbadensis furnished a mixture of polysaccharides containing mainly pectic acid, along with a d-galactan, a glucomannan, and an arabinan. The pectic acid was partly removed by treatment with calcium chloride, and the resulting, hexose-enriched, polysaccharide mixture was fractionated through a column of DEAE-cellulose to yield a d-galactan containing d-galactose (92.9% and d-galacturonic acid (3.8%). Hydrolysis of the permethylated d-galactan furnished 2,3,4,6-tetra-, 2,3,6-tri-, and 2,3-di-O-methylgalactose in the molar ratios of 1:26:1. On periodate oxidation, the d-galactan reduced 0.95 molar equivalent of the oxidant per hexosyl residue, and liberated one molar equivalent of formic acid per 26 galactosyl residues. Smith degradation of the d-galactan afforded mainly threitol. From these results, a structure has been assigned to the repeating unit of the d-galactan. The number-average, molecular weight of the peracetylated galactan has been found to be 3.74 x 10⁴.     

Purification of monoterpenyl glycosides by gel-permeation and hydrophobic-interaction chromatography on polyacrylamide (Bio-Gel P-2)

Hydrophobic interaction of the aglycone of monoterpenyl glycosides with the polyacrylamide matrix of Bio-Gel P-2 greatly retards the elution of these substances when chromatographed in dilute aqueous sodium chloride. This hydrophobic interaction is eliminated by inclusion of 15% acetonitrile in the eluant, thereby permitting conventional gel-permeation chromatography. Combination of these techniques by sequential chromatography on the same Bio-Gel column, in the hydrophobic interaction mode followed by the gel-permeation mode, provides a simple, yet mild and highly selective procedure for the purification of monoterpenyl glycosides from crude plant extracts. Examination of the chromatographic properties of beta-D-glucopyranosides and beta-D-galactopyranosides of a number of acyclic, monocyclic, and bicyclic monoterpenols indicates that the extent of hydrophobic interaction is of diagnostic value in determining the nature of the aglycone.     

On the mRNA induced conformational change of AA-tRNA exposing the T-pse-C-G sequence for binding to the 50S ribosomal subunit

A model is proposed which assumes that the codon-anti-codon interaction induces a conformational change in the tertiary structure of AA-tRNA exposing the hidden T-Ψ-C-G sequence for binding to the C-G-A-A sequence in the 5S RNA of the 50S ribosomal subunit. The model is supported by binding experiments with C-G-(³H)A-(³H)A and by the inhibition of poly(Phe) synthesis by C-G-A-A. The process is dependent on the 30S subunit, the template, and the AA-tRNA × EF-T_u × GTP complex.     

Structure of the D-fructan isolated from garlic (Allium sativum) bulbs

Extraction of defatted garlic bulbs with hot water yielded a mixture of polysaccharides containing pectic acid, a D-galactan, and a fructan component. The pectic acid was partially removed as calcium pectate, and the galactan-enriched portion was separated by fractional precipitation with alcohol; on concentration and several fractionations, the supernatant liquor furnished the fructan component, which contained fructose (94.4%) and glucose (4.3 %). Methanolysis and hydrolysis of the permethylated fructan gave (a) 1,3,4,6-tetra-O-methyl-D-fructose, (b) 2,3,4,6-tetra-O-methyl-D-glucose, (c) 2,4,6-tri-O-methyl-D-glucose, and (d) 3.4,6-tri-O-methyl-D-fructose in the ratio (a + b): (d) = 1:20.3. On periodate oxidation, the fructan reduced one molar equivalent of the oxidant per hexosyl residue, and liberated one molar equivalent of formic acid per 51 hexosyl residues. On Smith degradation, the major product was glycerol, and ～2 % of the glucose survived. From these results, and from the fact that the fructan is hydrolyzed by β-D-fructofuranosidase, a linear, inulin-type of structure is suggested for it.     

Structural studies on Klebsiella type 61 capsular polysaccharide

The capsular polysaccharide from klebsiella type 61 was found to contain d-galactose, d-glucose, d-mannose, and d-glucuronic acid in the ratios 1:2:1:1. Acid hydrolysis of the polysaccharide gave one aldobiouronic acid, whose structure was established. Methylation analysis of the polysaccharide provided information about the linkages in the polysaccharide. The polysaccharide is composed of a pentasaccharide repeating unit for which structures are proposed.     

The isolation and partial characterization of a glycoprotein isolated from human gastric aspirates and from extracts of gastric mucosae

The isolation and partial characterization of a glycoprotein isolated from individual gastric aspirates and extracts of gastric mucosae solubilized with N-acetylcysteine is described.The isolated glycoproteins and the glycoproteins from proteolysed gastric aspirates showed virtually the same carbohydrate and amino acid composition. The results indicate that they consist of a protein core to which are attached carbohydrate side-chains composed of four sugars: N-acetylgalactosamine N-acetylglucosamine, galactose, fucose showing a ratio of 1 : 3 : 4 : 2. Superimposed on this basic structure were additional sugar residues, the blood-group determinants. The results also suggest that the carbohydrate side-chains are linked by an alkali-labile O-glycosidic linkage to the threonine and serine residues of the protein core, N-acetylgalactosamine forming the link.     

Anticytokinin activity of 4-furfurylamino-7-(beta-D-ribofuranosyl)pyrrolo(2,3)pyrimidine

4-Furfurylamino-7-(β-D-ribofuranosyl)pyrrolo[2,3-d]-pyrimidine, the 7-deaza analog of kinetin riboside, has been synthesized and found to be a potent anticytokinin in the tabacco callus bioassay.     

1,5-anhydro-2-deoxy-3-O-(2-deoxy-beta-D-arabino-hexopyranosyl)-D-arabino-hex-1-enitol, the by-product in the enzymic hydration of D-glucal by beta-D-glucosidase from emulsin.

The by-product (3) in the hydration of D-glucal (1) catalyzed by emulsin beta-D-glucosidase has been identified as 1,5-anhydro-2-deoxy-3-O-(2-deoxy-beta-D-arabino-hexopyranosyl)-D-arabino-hex-1-enitol. Two models for the formation of 3 are discussed, involving transfer of a 2-deoxy-D-arabino-hexopyranosyl cation to HO-3 of D-glucal (glycon transfer) and transfer of an allylic D-pseudoglucal cation to HO-1 of 2-deoxy-D-arabino-hexopyranose (aglycan transfer). The enzymic production of 3 is highly regiospecific, which lends support to the second model and implies the presence of a specific binding-site for the aglycon moiety.     

Structure of periodated ribonucleosides and ribonucleotides]

Periodate oxidation converted adenosine, guanosine, cytidine, and uridine into the corresponding dialdehydes. No free dialdehydes are present in solution, but several hydrated species occur (i.r. and n.m.r.). In the solid state, the dialdehydes are completely polymerized. The m.s. molecular peaks corresponding to the free daildehydes were of very low intensity. The c.d spectra of adenosine- and cytidinedialdehyde showed heavily diminished Cotton effects in comparison to the parent nucleosides. For uridine-dialdehyde, the signal intensity of the strongest transition was diminished by about one half, indicating a looser structure allowing free rotation of the base. By contrast, the c.d. signal of guanosine-dialdehyde was increased, indicating self-association of oligomers. The nucleoside-dialdehydes gave, with hydrazides, morpholine derivatives, which posses rigid, stable structures (c.d).     

An arabinogalactan from the fibres of cotton (Gossypium arboreum L.)

An acidic arabinogalactan has been isolated from fibres of the cotton plant (Gossypium arboreum L.) at the stage of intensive secondary-wall formation. The polysaccharide contains arabinose, galactose, rhamnose, and glucuronic acid residues in the molar ratios 1:1.2:0.1:0.2. Periodate oxidation and methylation studies showed that there is a main chain of (1→3)-linked galactopyranosyl residues to which side chains are attached at O-6. The side chains consist of (1→6)-linked galactopyranosyl residues substituted at O-3 by (1→5)-linked arabinofuranosyl chains. Terminal galactopyranosyl, rhamnopyranosyl, and glucopyranuronosyl groups are also present. Enzymic hydrolysis showed that the configurations of the galactose and arabinose residues are d and l, respectively.     

The synthesis of oligosaccharide-asparagine compounds. V. O- -D-mannopyranosyl-(1 leads to 6)-O-(2-acetamido-2-deoxy- -D-glucopyranosyl)-(1 leads to 4)-2-acetamido-N-(L-aspart-4-oyl)-2-deoxy- -D-glucopyranosylamine

O-α-d-Mannopyranosyl-(1→6)-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1→4)-2-acetamido-N-(l-aspart-4-oyl)-2-deoxy-β-d-glucopyranosylamine (12), used in the synthesis of glycopeptides and as a reference compound in the structure elucidation of glycoproteins, was synthesized via condensation of 2,3,4,6-tetra-O-acetyl-α-d-mannopyranosyl bromide with 2-acetamido-4-O-(2-acetamido-3-O-acetyl-2-deoxy-β-d-glucopyranosyl)-3,6-di-O-acetyl-2-deoxy-β-d-glucopyranosyl azide (5) to give the intermediate, trisaccharide azide 7. [Compound 5 was obtained from the known 2-acetamido-4-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)-3,6-di-O-acetyl-2-deoxy-β-d-glucopyranosyl azide by de-O-acetylation, condensation with benzaldehyde, acetylation, and removal of the benzylidene group.] The trisaccharide azide 6 was then acetylated, and the acetate reduced in the presence of Adams' catalyst. The resulting amine was condensed with 1-benzyl N-(benzyloxycarbonyl)-l-aspartate, and the O-acetyl, N-(benzyloxycarbonyl), and benzyl protective groups were removed, to give the title compound.     

A synthesis of (plus or minus)-myo-inositol 1-phosphate

Condensation of 2-amino-2-deoxy-D-galactopyranose with D-glucuronic acid or D-mannurono-6,3-lactone gave, after ion-exchange chromatography, the 2-deoxy-2-(D-glycofuranosylurono-6,3-lactone)amino-D-galactose derivatives 1 or 2, respectively, characterized as crystalline hexaacetates.     

Multiple Smith-degradations of carcinoembryonic antigen (CEA) and of asialo CEA

Carcinoembryonic antigen (CEA) and asialo CEA were subjected to multiple Smith-degradation (i.e., for each degradation, application in sequence of periodate oxidation, borohydride reduction, and mild hydrolysis with acid; borohydride-t was substituted for unlabelled borohydride). High yields of modified glycoproteins were obtained at each stage. After three complete degradations and a further periodate-borohydride-t treatment, the carbohydrate content of CEA and of asialo CEA had decreased from 45–50% to 11–12% (i.e., 90% removal of carbohydrate). Glycerol was always one of the products obtained after each degradation, but threitol and erythritol were not detected. The second degradation caused a substantial loss of 2-acetamido-2-deoxyglucose, which is consistent with the location of some of this monosaccharide towards the terminal (non-reducing) end of the oligosaccharides. The “core” region of the oligosaccharides is composed of galactose, mannose, and 2-acetamido-2-deoxyglucose. After the fourth oxidation, 2-acetamido-2-deoxyglucose was 50–60% of the total content of residual carbohydrate. After the first degradation, there was a progressive loss in antigenic activity, but this was associated with a small amount of hydrolysis of the protein moiety of CEA.     

Enzymatic isomerization (Δ7 → Δ8) of the nuclear double bond of 14α-alkyl substituted sterol precursord of cholesterol

The catalysis by rat liver microsomes under anaerobic conditions, of the conversion of [3α-³H]14α-methyl-5α-cholest-7-en-3β-ol and of [2,4-³H]14α-hydroxymethyl-5α-cholest-7-en-3β-ol to labeled 14α-methyl-5α-cholest-8-en-3β-ol and 14α-hydroxymethyl-5α-cholest-8-en-3β-ol, respectively, has been demonstrated. This finding is of importance in evaluating past research in this area and in consideration of pathways and mechanisms involved in enzymatic removal of carbon atom 32 of 14α-methyl sterols. Also described herein are syntheses of [2,4-³H]14α-hydroxymethyl-5α-cholest-7-en-3β-ol and 3β-acetoxy-14α-methyl-5α-cholest-8-ene.     

Overestimates of the size of poly(A) segments.

Poly(A) molecules containing on average 25, 45 and 90 nucleotide residues are all eluted from DEAE-Sephadex in the presence of 7 M urea by approximately the same NaCl concentration which is higher than that required to elute 4 S and 5 S RNA. The same poly(A) molecules have electrophoretic mobilities on 12% polyacrylamide gels which are proportional to the logarithm of the number of nucleotide residues they contain but not to the number found in 4 S and 5 S RNA, even after denaturation of the RNA and performing electrophoresis in the presence of 2.2 M formaldehyde. As a result, many reported estimates of poly(A) size derived from such techniques are probably too large and need re-evaluation. Corrections are suggested for the use of 4 S and 5 S RNA as molecular weight markers for electrophoresis on 12% polyacrylamide gels.     

Preparation of acetylenic sugar derivatives by way of 2-(N-nitroso)acetamido sugars

N-Nitrosation with dinitrogen tetraoxide was used to convert 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-α-D-glucopyranose (1) and 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-β-D-galactopyranose (4) in high yield into the N-nitroso derivatives 2 and 5, respectively. Similarly, 3-acetamido-1,2,4,6-tetra-O-acetyl-3-deoxy-β-D-glucopyranose (12) and methyl 2-acetamido-3,4,5,6-tetra-O-acetyl-2-deoxy-D-gluconate (15) gave their respective, crystalline N-nitroso derivatives 13 and 16. Various other 2-acetamido sugar derivatives were likewise nitrosated. In ethereal solution, compounds 2 and 16 reacted with potassium hydroxide in isopropyl alcohol to give the C₅ acetylene, 1,2-dideoxy-D-erythro-pent-1-ynitol, isolated as the known triacetate 3. By the same procedure, the galacto derivative 5 was converted in high yield into the 3-epimeric C₅ acetylene, 1,2-dideoxy-D-threo-pent-1-ynitol, isolated as its triacetate 6 and characterized by conversion into the known, crystalline 1,2-dideoxy-3-O-(3,5-dinitrobenzoyl)-4,5-O-isopropylidene-D-threo-pent-1-ynitol (7).