Chemical structures of mono-, di-, tri-, and tetraglycosyl glycerides in rice bran.

1. Monoglycosyl monoglyceride, mono-, di-, tri- and tetraglycosyl diglycerides were isolated from rice bran and characterized for their chemical structures. 2. Monoglycosyl monoglycerides were characterized as Gal(beta 1' leads to 3)-1- or 2-monoacyl-sn-glycerol and Glc(beta 1' leads to 3)-1- or 2-monoacyl-sn-glycerol. 3. The structures of monoglycosyl diglyceride were Gal(beta 1' leads to 3)-1,2-diacyl-sn-glycerol and Glc(beta 1' leads to 3)-1,2diacyl-sn-glycerol. Epimeric separation of the galactosyl and glucosyl glycerides was for the first time achieved by thin-layer chromatography. 4. The main diglycosyl diglyceride was shown to be Gal(alpha 1' leads to 6')-Gal(beta 1' leads to 3)-1,2-diacyl-sn-glycerol. 5. The major structure of triglycosyl diglyceride was characterized as Gal(alpha 1' leads to 6')-Gal(alpha 1' leads to 6')-Gal(beta 1' leads to 3)-1,2-diacyl-sn-glycerol. 6. The representative structure of tetraglycosyl diglyceride was for the first time established as Gal(alpha 1' leads to 6')-Gal(alpha 1' leads to 6')-Gal(a-pha 1' leads to 6')-Gal(beta1' leads to 3)-1,2-diacyl-sn-glycerol.     

Synthesis,photophysical properties and photocytotoxicity of mono-, di-, tri- and tetra-glucosylated fluorophenylporphyrins

In order to explore the effect of substitution patterns on the photocytotoxicity of glycoconjugated porphyrins, we synthesized and characterized a ‘complete set’ of tetrakis(perfluorophenyl)porphyrins having β-d-glucopyranosylthio groups on the phenyl ring. Among five possible derivatives, trans-substituted S-glucosylated porphyrin trans-2_OH exerted outstanding photocytotoxicity (EC₅₀ value was <5 nM) in HeLa cells. The excellent photocytotoxicity of trans-2_OH was found to be attributable to several factors, namely high optical transition probability in aqueous media, efficient type I photoreactions and enhanced cellular uptake.     

Synthesis of di-, tri-, and tetra-saccharides corresponding to receptor structures recognised by Streptococcus pneumoniae

Syntheses are described for methyl 2-acetamido-2-deoxy-4-O-β-d-galactopyranosyl-α-d-glucopyranoside, methyl 2-acetamido-2-deoxy-4-O-β-d-galactopyranosyl-β-d-glucopyranoside, methyl 3-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl-β-d-galactopyranoside, methyl 3-O-(2-acetamido-2-deoxy-4-O-β-d-galactopyranosyl-β-d-glucopyranosyl)-β-d-galactopyranoside, and methyl 4-O-[3-O-(2-acetamido-2-deoxy-4-O-β-d-galactopyranosyl-β-d-glucopyranosyl)-β-d-galactopyranosyl]- β-d-glucopyranoside.     

Diallyl di-, tri- and tetrasulphide from Adenocalymma alliaceae

The essential oil from flowers and leaves of Adenocalymma alliaceae (Bignoniaceae) consists almost entirely of diallyl di-, tri-and tetra-sulphide, a mixture formerly encountered within the Allium genus but never before convincingly recognized within the class of dicotyledonous angiosperms.     

Oxidized mono-, di-, tri-, and polysaccharides as potential hemoglobin cross-linking reagents for the synthesis of high oxygen affinity artificial blood substitutes

Various oxidized mono/di/tri/poly saccharides were studied as potential hemoglobin (Hb) cross-linkers in order to produce oxygen carriers with high oxygen affinities (low P(50)'s) and high molecular weights (therefore lower macromolecular diffusivities compared to tetrameric Hb). Such physical properties were desired to produce polymerized hemoglobins (PolyHbs) with oxygen release profiles similar to that of human blood, as was demonstrated in work by Winslow (1). In this present study, bovine hemoglobin was cross-linked with a variety of oxidized (ring-opened) saccharides, which resulted in cross-linked Hb species ranging in size from 64 to 6400 kDa (depending on the particular oxidized saccharide used in the reaction) and P(50)'s ranging from 6 to 15 mmHg. A parallel synthetic approach was used to synthesize these carbohydrate-hemoglobin conjugates, and asymmetric flow field-flow fractionation (AFFF) coupled with multi-angle static light scattering (MASLS) was used to measure the absolute molecular weight distribution of these PolyHb dispersions. Cross-linking reactions were conducted at two pHs (6 and 8), with larger cross-linked Hb species produced at pH 8 (where hydrolysis was most likely to occur between glycosidic bonds linking adjacent saccharide rings) rather than at pH 6. The largest molecular weight species formed from these reactions consisted of Hb cross-linked with ring-opened lactose, maltose, methylglucopyranoside, sucrose, trehalose, and 15 kDa and 71 kDa dextran at high pH (pH 8). The most promising Hb cross-linker was methylglucopyranoside, which resulted in very large cross-linked Hb species, with low P(50)'s and lower methemoglobin (metHb) levels compared to the other Hb cross-linking reagents.     

Syntheses and crystal structures of mono-, di- and trinuclear cobalt complexes of a salen type ligand

Three cobalt complexes containing the salen type ligand, bis(salicylidene)-meso-1,2-diphenylethylenediaminato (mdpSal²⁻), are reported. The complexes differ in nuclearity and include the mononuclear, Co(mdpSal) (1), which contains a Co(II) metal center bound to one mdpSal⁻² ligand frame in a square planar geometry. The second complex is the dinuclear [Co(mdpSal)Cl]₂ (2) in which both cobalt ions have been oxidized to the +3 oxidation state. The overall geometry of complex 2 is an edge-sharing bioctahedron with the coordination sphere around each cobalt metal center consisting of one mdpSal⁻² ligand and one Cl⁻ ion. The shared edge between the Co(III) ions contains two bridging phenolate groups, one from each ligand frame. Complex 3 is a linear, mixed valence, trinuclear species, [Co(mdpSal)(OAc)(μ-OAc)]₂Co, with the oxidation states of the metal centers assigned as Co(III)-Co(II)-Co(III). The terminal Co(III) centers are equivalent with the central Co(II) lying on the inversion center of the molecule. Each cobalt ion in 3 adopts an octahedral geometry with the terminal Co(III) ions being bound to one mdpSal²⁻ ligand each. All phenolate groups bridge to the central Co(II). The coordination sphere about each metal center in the trinuclear complex is completed by four acetate groups, two of which bind in a μ-fashion bridging from the terminal Co(III) metal centers to the central Co(II). The complexes have been characterized by X-ray crystallography as well as UV-Vis and IR spectroscopy.     

The mutation rates of di-, tri- and tetranucleotide repeats in Drosophila melanogaster

In a recent study, we reported that the combined average mutation rate of 10 di-, 6 tri-, and 8 tetranucleotide repeats in Drosophila melanogaster was 6.3 x 10(-6) mutations per locus per generation, a rate substantially below that of microsatellite repeat units in mammals studied to date (range = 10(-2)-10(-5) per locus per generation). To obtain a more precise estimate of mutation rate for dinucleotide repeat motifs alone, we assayed 39 new dinucleotide repeat microsatellite loci in the mutation accumulation lines from our earlier study. Our estimate of mutation rate for a total of 49 dinucleotide repeats is 9.3 x 10(-6) per locus per generation, only slightly higher than the estimate from our earlier study. We also estimated the relative difference in microsatellite mutation rate among di-, tri-, and tetranucleotide repeats in the genome of D. melanogaster using a method based on population variation, and we found that tri- and tetranucleotide repeats mutate at rates 6.4 and 8.4 times slower than that of dinucleotide repeats, respectively. The slower mutation rates of tri- and tetranucleotide repeats appear to be associated with a relatively short repeat unit length of these repeat motifs in the genome of D. melanogaster. A positive correlation between repeat unit length and allelic variation suggests that mutation rate increases as the repeat unit lengths of microsatellites increase.      

Mutagenicity of mono-, di- and tri-nitropyrenes in Chinese hamster ovary cells

1-Nitropyrene (1-NP), 1,3-dinitropyrene (1,3-DNP), 1,6-dinitropyrene (1,6-DNP), 1,8-dinitropyrene (1,8-DNP) and 1,3,6-trinitropyrene (1,3,6-TNP) were tested for mutagenicity in cultured Chinese hamster ovary (CHO) cells. Mutation at the hypoxanthine-guanine phosphoribosyl transferase gene locus was quantified. While 1-NP and 1,3-DNP had only marginal direct-acting mutagenicity, 1,6-DNP, 1,8-DNP and 1,3,6-TNP showed definite mutagenicity, with specific mutagenic activities of 8.1, 21 and 54 mutants/10⁶ survivors/μg·ml⁻¹ respectively. The mutagenicity of 1-NP increased with increasing concentrations of Aroclor-1254 induced liver homogenate (S9) in the treatment medium. However, S9 at all concentrations tested decreased the mutagenicity of 1,6-DNP and 1,8-DNP. S9 at low concentrations enhanced the mutagenicity of 1,3-DNP and 1,3,6-TNP and that at high concentrations decreased their mutagenicity. The positive mutagenic response of the nitropyrenes suggests that they are potentially carcinogenic, and that further research into their possible human health risk should be performed.     

Molecular species of mono-, di-, and triphosphoinositides of bovine brain

The mono-, di-, and triphosphoinositides of bovine brain were isolated by chromatography on columns of DEAE-cellulose, alumina, and silicic acid. The major molecular species in each phosphoinositide class were identified and quantitatively estimated by combined thin-layer and gas-liquid chromatography of the component diglycerides, which were released by hydrolysis with a specific brain phosphodiesterase. The diglycerides were treated with pancreatic lipase, and the positional distribution of the fatty acids was determined. Over 27 molecular species were identified, and these accounted for about 95% of each phosphoinositide class, but the 1-stearate 2-arachidonate derivative contributed more than 40% of the total in each class. The other molecular species also were qualitatively and quantitatively similar in the three phosphoinositide classes. All the long-chain and polyunsaturated acids were confined to the 2-position and were preferentially paired with stearic acid in the 1-position. Oleic acid in the 2-position was about equally divided between species with palmitic and stearic acids in the 1-position. These results suggest that the mono-, di-, and triphosphoinositides of the bovine brain have similar compositions and that the various molecular species may be metabolically related.     

Mutagenicity of mono-, di- and tri-nitropyrenes in Chinese hamster ovary cells

1-Nitropyrene (1-NP), 1,3-dinitropyrene (1,3-DNP), 1-6-dinitropyrene (1,6-DNP), 1,8-dinitropyrene (1,8-DNP) and 1,3,6-trinitropyrene (1,3,6-TNP) were tested for mutagenicity in cultured Chinese hamster ovary (CHO) cells. Mutation at the hypoxanthine-guanine phosphoribosyl transferase gene locus was quantified. While 1-NP and 1,3-DNP had only marginal direct-acting mutagenicity, 1,6-DNP, 1,8-DNP and 1,3,6-TNP showed definite mutagenicity, with specific mutagenic activities of 8.1, 21 and 54 mutants/10(6) survivors/micrograms . ml-1 respectively. The mutagenicity of 1-NP increased with increasing concentrations of Aroclor-1254 induced liver homogenate (S9) in the treatment medium. However, S9 at all concentrations tested decreased the mutagenicity of 1,6-DNP and 1,8-DNP. S9 at low concentrations enhanced the mutagenicity of 1,3-DNP and 1,3,6-TNP and that at high concentrations decreased their mutagenicity. The positive mutagenic response of the nitropyrenes suggests that they are potentially carcinogenic, and that further research into their possible human health risk should be performed.     

Stereochemistry of nucleic acids and their constituents. IV. Allowed and preferred conformations of nucleosides,nucleoside mono-, di-, tri-, tetraphosphates,nucleic acids and polynucleotides

A uniform notation and convention is suggested to describe the torsional angles in nucleic acids and their derivatives. The torsional angle χ, relating the stereochemistry of the base with respect to the sugar, shows more variation for the β-purine glycosides than for the β-pyrimidine glycosides. This variation is attributed to the fact that the β-purine derivatives may form intramolecular O(5′)-H…N(3) hydrogen bonding. The χ values for the α-purine and α-pyrimidine glycosides show preference for the –syn-clinal (or anti) conformation. The mode of puckering of the sugar also influences the χ value. The various possible conformations for the furanose ring are described by the torsional angles τ₀ τ₁, τ₂, τ₃, τ₄, about the five ring bonds. From an analysis of the torsional angles (ω, ?, ψ, ψ′, ?′, ω′) about the sugar phosphate bonds in the x-ray structures of the known nucleosides, nucleotides, phosphodiesters, nucleic acids, and related compounds, and from a consideration of molecular models, it is found that the possible conformations for the backbone of helical nucleic acids is strikingly limited. Most importantly, the preferred conformation of the nucleotide unit in poly nucleotides and nucleic acids turns out to be the same as that found for the nucleotide in the crystal structure. It is observed that base “stacking” is a consequence of the restricted backbone conformation. The torsional angles are illustrated in the form of conformational “wheels”. Interrelation between the torsion angles about successive pairs of sugar-phosphate bonds are presented in the form of conformational maps: ω,?; ?,ψ; ψ.ψ′; ψ′,?′; ?′,ω′; ω′,ω. The ω′,ω map shows the perferred conformations about the inter-nucleotide bonds of right- and left-handed helices and the possible conformations of phosphodiesters. The preferred conformation of the pyrophosphate and triphosphate is that in which the phosphate oxygens display a staggered arrangement when viewed along the P–P axis. A plausible structure and conformation for the ATPM^2? backbound complex is presented. This structure differs from that proposed by SzentGyorgi in that the metal (only transition metals are considered here) is not bound to the NH₂ nitrogen of adenine, but rather is simultaneously bound to N(7) of the ring and three phosphates (α, β, γ), or N(7) of the ring and two phosphates (β, γ). The remaining metal coordination may be satisfied by solvent–metal or enzyme–metal bonds.     

Autoxidation of mono-, di-, and trilinoleoyl glycerols at different concentrations

Mono-, di-, and trilinoleoyl glycerols were diluted with 1-undecanol or hexadecane to produce specific concentrations, and their oxidation processes were measured at 65 degrees C at 12% relative humidity. The rate constants for oxidation of the linoleoyl residue were proportional to the concentration for all substrates. This fact suggests that no intramolecular radical chain reaction between the linoleoyl residues occurred.     

Fused lacZ genes code for di-, tri- and tetra-beta-galactosidase in Escherichia coli.

Plasmids were constructed which carry two, three or four active lacZ genes of Escherichia coli fused head-to-tail in phase. The products of these oligomeric lacZ genes are shown to be polypeptides with expected subunit mol. wts. of 230 kd (di-beta-galactosidase), 350 kd (tri-beta-galactosidase) and 460 kd (tetra-beta-galactosidase). Di-beta-galactosidase has the same enzymatic activity as the wild-type enzyme. It subunits are practically not degraded proteolytically in vivo. It aggregates predominantly to a dimer which has the same sedimentation constant as the wild-type tetrameric enzyme. Furthermore, it is more heat stable than the wild-type enzyme. Tri- and tetra-beta-galactosidase have strongly reduced enzymatic activities and are largely degraded. Our experiments lead us to propose that covalent joining of two subunits through proper gene duplication may possibly be an intermediate in the evolution of self aggregation of homo-oligomeric proteins.     

Fractionation of the rice bran layer and quantification of vitamin E, oryzanol, protein, and rice bran saccharide

Value-added processing with respect to rice milling has traditionally treated the rice bran layer as a homogenous material that contains significant concentrations of high-value components of interest for pharmaceutical and nutraceutical applications. Investigators have shown that high-value components in the rice bran layer vary from differences in kernel-thickness, bran fraction, rice variety, and environmental conditions during the growing season. The objectives of this study were to quantify the amount of rice bran removed at pre-selected milling times and to correlate the amount of rice bran removed at each milling time with the concentration of vitamin E, gamma-oryzanol, rice bran saccharide, and protein obtained. The ultimate goal of this research is to show that rice bran fractionation is a useful method to obtain targeted, nutrient-rich bran samples for value-added processing. Two long grain rice cultivars, Cheniere and Cypress, were milled at discrete times between 3 and 40 seconds using a McGill mill to obtain bran samples for analysis. Results showed that the highest oryzanol and protein concentrations were found in the outer portion of the rice bran layer, while the highest rice bran saccharide concentration was found in the inner portion of the bran layer. Vitamin E concentration showed no significant difference across the bran layer within a variety, though the highest magnitude of concentration occurs within the first 10 seconds of milling for both varieties. To extract the higher concentration of oryzanol and protein only the outer portion of the bran layer requires processing, while to extract the higher concentration of rice bran saccharide, only the inner portion of the bran layer requires processing. Rice bran fractionation allows for the selective use of portions of the bran layer and is advantageous for two reasons: (1) bran fractions contain higher concentrations of components of interest with respect to the overall bran layer average, and (2) less bran needs to be processed to obtain components of interest.     

Characterization of mono-, di-, and tri-O-acetylated sialic acids on human cells

The presence of mono-, di-, and tri-O-acetylated sialic acids on human cells was demonstrated by using radiochromatographic and chemical techniques. Human melanoma cells and fresh colon tissue were biosynthetically labeled with 6- (3H) glucosamine. Radiolabeled sialic acids were hydrolytically removed from cellular glycoconjugates, purified by ion-exchange chromatography, and separated by paper chromatography on the basis of the number of O-substitutions on each sialic molecule. This analytical technique characterized radiolabeled sialic acids that migrated with the same Rf as synthetic mono-, di-, and tri-O-acetylated 14C-labeled sialic acids. The mono-O-acetylated sialic acids were characterized by their sensitivity to sodium periodate oxidation and a crude mouse liver esterase preparation. The di- and tri-O-acetylated sialic acids were characterized by their resistance to sodium periodate oxidation and sensitivity to the action of crude mouse liver esterase. Chromatographically separated di- and tri-O-acetylated sialic acids from normal human colon tissue were characterized by their respective ion molecular weights by using fast-atom bombardment-mass spectrometry. Using these methods, we chemically characterized mono, di-, and tri-O-acetylated sialic acids expressed on human cells. Aberrant expression of O-acetylated sialic acids was associated with adenocarcinoma of the colon, leading to a nearly complete loss of di- and tri-O-acetylated sialic acids.     

Antibacterial activities of mono-, di- and tri-substituted triphenylamine-based phosphonium ionic liquids

We report the synthesis of new mono, di and tri phosphonium ionic liquids and the evaluation of their antibacterial activities on both Gram-positive and Gram-negative bacteria from the ESKAPE-group. Among the molecules synthesized some of them reveal a strong bactericidal activity (MIC?=?0.5?mg/L) for Gram-positive bacteria (including resistant strains) comparable to that of standard antibiotics. A comparative Gram positive and Gram negative antibacterial activities shows that the nature of counter-ion has no significant effects. Interestingly, the increase of phosphonium lateral chains (from 4 to 8 carbons) results in a decrease of antibacterial activities. However, the increase of the spacer length has a positive influence on the activity on both Gram-positive and Gram-negative bacteria except for E. aerogenes. Finally, the increased charge density has no effect on the Gram-positive antibacterial activities (MIC between 2 and 4?mg/L) but seems to attenuate (except for P. aeruginosa) the discrimination between Gram-positive and Gram-negative. Overall these results suggest a unique mechanism of action of these triphenylamine-phosphonium ionic liquid derivatives.     

Comparative effects of mono-, di-, tri-, and tetrasulfides derived from plants of the Allium family: redox cycling in vitro and hemolytic activity and Phase 2 enzyme induction in vivo

Epidemiological evidence indicates that a high dietary intake of plants of the Allium family, such as garlic and onions, decreases the risk of cancer in humans. It has been suggested that this effect is due to the ability of the aliphatic mono-, di-, tri-, and tetrasulfides derived from these vegetables to increase tissue activities of Phase 2 detoxification enzymes. In contrast, toxic effects have been recorded in domestic and farm animals after the consumption of garlic or onions, involving oxidative damage to erythrocytes and consequent hemolytic anemia. This effect again has been attributed to the aliphatic sulfides. In the present study, the ability of sulfides derived from garlic and onions to generate "active oxygen" species and cause oxidative damage to erythrocytes in vitro has been compared, together with their ability to cause hemolytic anemia and increase the activity of the Phase 2 enzymes quinone reductase (QR) and glutathione S-transferase (GST) in rats. Monosulfides were without significant effect on any parameter. Di-, tri-, and tetrasulfides generated hydrogen peroxide in the presence of GSH and hemoglobin and caused oxidative damage to erythrocytes in vitro. The activity decreased in the order of tetra- > tri- > disulfide, with the allyl compounds being more potent than the propyl. In vivo, both allyl and propyl tri- and tetrasulfides were powerful hemolytic agents. In contrast, only the allyl sulfides increased the activities of QR and GST; the propyl derivatives were completely without effect. Allyl and propyl tri- and tetrasulfides, thus, may contribute to the toxic effects of Allium vegetables, while only the allyl derivatives are effective in increasing tissue activities of cancer-protective enzymes.     

Separation of common nucleotides,mono-, di- and triphosphates,by capillary electrophoresis

A capillary electrophoretic procedure for the separation of eleven nucleotides, 5′-mono-, di- and triphosphates of adenosine, guanosine, cytidine and uridine, has been developed. All eleven analytes can be separated in a fused-silica capillary (63 cm to the detector, I.D. 75 μm) at 20 kV in a 0.02 mol l⁻¹ phosphate-borate buffer (pH 8.0–9.0) with a separation factor ⩾1. The values of the Offord parameter calculated for individual nucleotides predict that monophosphates will migrate faster than triphosphates, and in turn triphosphates will precede diphosphates. By analogy, faster electroosmotic mobility (lower electromigration) of purine nucleotides (AP, GP) can be explained by a more voluminous structure of purine derivatives (two aromatic rings as compared to pyrimidines). Generally speaking, all compounds separated follow the Offord equation assuming that the triphosphate derivatives are ionized to the third degree forming HL³⁻ anions. This assumption is in agreement with the current knowledge about protolytic equilibria of polyphosphates. The only exception to this rule is faster migration of guanosine-5′-triphosphate (GTP) preceding uridine-5′-monophosphate (UMP) which is ascribed in part to the larger molecule of GTP and the two additional OH-groups bound to the pyrimidine ring of UMP.