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PubMed1996

Individual differences in sugar consumption following systemic or intraaccumbens administration of low doses of amphetamine in nondeprived rats.

Rats exhibit individual differences in their propensity to ingest sucrose and in their feeding response to low doses of amphetamine (AMP). Rats with high baseline sugar intake (HIGH) show a decrease in sugar consumption in response to AMP, while rats with low baseline sugar intake (LOW) show an increase in consumption (33,34). At present, it is not known whether LOW and HIGH rats would be differentially responsive to higher, anorexigenic doses of AMP. Thus, the present study was developed to further determine the dose-response curve for AMP's effects on sugar consumption in LOW and HIGH rats. One group of rats received IP injections of 0.05, 0.1, and 0.2 mg/kg AMP, while a second group was administered 0.25, 0.5, and 1.0 mg/kg AMP. A third group of rats received intranucleus accumbens (Acc) microinjections of low to moderate (2.0-8.0 micrograms) doses of AMP, because evidence indicates that this may be an important site of action for AMP's effects on feeding in LOW and HIGH rats. Results showed that at low doses (< or = 0.25 mg/kg), AMP stimulated sugar consumption in LOW rats and either had no effect or inhibited consumption in HIGH rats. At doses greater than 0.25 mg/kg, AMP inhibited sugar consumption in both LOW and HIGH rats. Furthermore, intra-Acc administration of AMP stimulated sugar intake in LOW rats and produced a slight, but nonsignificant, decrease in consumption in HIGH rats. Taken together, these results show that LOW and HIGH rats exhibit individual differences in their feeding response to low but not moderate to high doses of AMP. Furthermore, the evidence indicates that the Ace is an important site for AMP's facilitatory effect on sugar consumption in LOW rats.

Amphetamine↗

PubMed1987

Antibody response to haptenic sugar antigen: immunodominancy of protein-bound lactose formed by amino-carbonyl reaction.

Several reducing sugars with structural analogy (glucose, galactose, lactose, melibiose, maltose and cellobiose) were bound to a carrier protein ovalbumin by amino-carbonyl reaction, and the non-enzymatically glycosylated proteins were injected into mice (BALB/c, C57BL/6, DBA/2 and C3H/He strains) with Freund's adjuvant. Antibody responses to the haptenic sugar antigens were analyzed quantitatively by enzyme-linked immunosorbent-assay using each sugar-bovine serum albumin complex. The haptenic sugar antigen from lactose induced a markedly higher response of specific antibody as compared with the haptenic sugar antigens from the other sugars. The antibody raised against the lactose adduct reacted well with lactulose (4-o-beta-D-galactopyranosyl-D-fructose) or alpha-N-acetyl-epsilon-N-deoxylactulosyl-L-lysine. The results suggested that immunogenicity of haptenic sugar antigens was remarkably different in sugar chemical structure, and that the lactose adduct formed by lactose-protein amino-carbonyl reaction could be an immunodominant antigenic determinant.

Amino Acids↗

PubMed1987

Membrane transport of sugar donors to the glycosylation sites.

The assembly of N-linked glycoproteins in eukaryotic cells begins with the segregation of these molecules within the lumen of intracellular vesicles. Since the sugar nucleotides are cytoplasmic molecules, translocation of the sugar moiety across the membrane appears as a crucial event in the glycoprotein synthesis. This N-glycosylation process occurs in two different cytological sites: in the rough endoplasmic reticulum, the stepwise synthesis of a large lipid-linked oligosaccharide takes place, as well as its transfer to protein; then after trimming the immature glycoprotein is further elongated in the Golgi apparatus. In this paper, a brief review will be given of the present knowledge on the sugar donor transport across the membrane barrier to the glycosylation site. Based upon the transmembrane orientation of oligosaccharide lipid intermediates and on the localization of the glycosyltransferase active sites, the different processes required to translocate the sugar moieties during the preassembly of the dolichyl-pyrophosphate-oligosaccharides will be examined. Combining the different results, obtained in several laboratories, it is suggested that the Man5-GlcNAc2-lipid is synthesized on the cytoplasmic side directly from the sugar-nucleotides and then translocated to the lumenal face where the Glc3-Man9-GlcNAc2-lipid is completed using Man-P-Dol and Glc-P-Dol as transmembrane carriers of these sugars. Concerning the elongation process leading to assembly of the antennae of N-acetyllactosamine type oligosaccharides, specific carriers for sugar nucleotides have been described as Golgi markers. Several authors have characterized such carriers for UDP-Gal, GDP-Fuc, CMP-NeuAc, UDP-GlcNAc and UDP-Glc using microsomal vesicles and similar results have been obtained in our laboratory using plasma membrane permeabilized cells. This carrier-mediated process leads to the formation of an intralumenal pool whose biological significance will be discussed. The translocation process of sugar donors occurring in the rough endoplasmic reticulum via lipid intermediates as well as in the Golgi apparatus via specific carriers would represent a regulation step based on the availability of the substrates for the glycosylation.

Animals↗

PubMed2006

Re-introducing bacteria in mosquitoes--a method for determination of mosquito feeding preferences based on coloured sugar solutions.

In this study, sugar-feeding was investigated as a possible means of re-introducing bacteria into mosquito midguts with the aim of identifying bacteria that are suitable for creating paratransgenic mosquitoes. In a paratransgenic approach, bacteria are utilised to deliver effector molecules capable of inhibiting pathogen development in the midgut of the vector. To determine if mosquitoes discriminate between sterile sugar solutions and sugar solutions with bacteria, a method for screening mosquito feeding preferences was developed. This method was tested for Aedes aegypti, Anopheles arabiensis and An. gambiae s.s. mosquitoes and is based on a dual-choice test of solutions labelled with food dyes. Three different tests (dye/colour detection, sugar detection and sugar-concentration detection) were performed to evaluate the method, after which bacteria previously isolated from mosquitoes were used in the experiments. It was shown that mosquitoes do not discriminate between sugar solutions with or without these bacteria indicating that sugar-feeding is a possible means to introduce bacteria into mosquitoes. Furthermore, two different setups of the method were used, enabling us to differentiate between tactile/taste and olfactory responses. The method described in this paper is easy to use, cost-effective and allows broad screening of mosquito sugar-feeding preferences.

Aedes↗

PubMed2006

Sugar malabsorption in functional abdominal bloating: a pilot study on the long-term effect of dietary treatment.

BACKGROUND: Functional abdominal bloating is a functional bowel disorder dominated by a feeling of abdominal fullness without sufficient criteria for another functional gastrointestinal disorder. Gas-related complaints (i.e., passage of flatus), which are present in a subgroup of these patients, might be associated with carbohydrate malabsorption. AIM: To evaluate the presence of lactose and/or fructose plus sorbitol malabsorption, and the long-term efficacy of malabsorbed sugar-free diets, in patients with Rome II criteria of functional abdominal bloating and gas-related symptoms. METHODS: Thirty-six consecutive patients (age, 51+/-3.1 years; sex, 12 M, 24 W) with Rome II criteria of functional abdominal bloating and gas-related symptoms were included in a pilot study. In all cases, the presence of malabsorption of both lactose (20 g) and fructose plus sorbitol (20+3.5 g) was assessed by means of hydrogen breath test. Patients with sugar malabsorption were put on a malabsorbed sugar-free diet. Follow-up visits were scheduled at both 1 and 12 months after starting the diet. Global rating scales of change as compared to the beginning of the study were used to assess symptom changes. RESULTS: Twenty-six of 36 patients (72.2%) presented sugar malabsorption (six lactose, 12 fructose plus sorbitol, and eight both). Seventeen of the 26 (65%) patients with malabsorption had symptoms of sugar intolerance during the 3-h breath testing period. All 26 were put on malabsorbed sugar-free diets. Eighty-one per cent of patients referred clinical improvement at 1-month visit, which was maintained at 12 months in 67% of them (complete improvement in 50% and partial improvement in 16.7%). CONCLUSIONS: Sugar malabsorption and intolerance seem to be frequent in patients with functional abdominal bloating and gas-related complaints. A malabsorbed sugar-free diet might be a long-term effective therapy in a high percentage of patients. Further controlled clinical trials are warranted.

Breath Tests↗

PubMed2006

School vending machine use and fast-food restaurant use are associated with sugar-sweetened beverage intake in youth.

OBJECTIVE: To examine associations between use of school vending machines and fast-food restaurants and youth intake of sugar-sweetened beverages. DESIGN: A cross-sectional observational study. SUBJECTS/SETTING: From a group randomized obesity intervention, we analyzed baseline data from 1,474 students in 10 Massachusetts middle schools with vending machines that sold soda and/or other sweetened drinks. MAIN OUTCOME MEASURES: Daily sugar-sweetened beverage consumption (regular soda, fruit drinks, and iced tea), purchases from school vending machines, and visits to fast-food restaurants in the preceding 7 days were estimated by self-report. STATISTICAL ANALYSES PERFORMED: Chi(2) and nonparametric tests were performed on unadjusted data; multivariable models adjusted for sex, grade, body mass index, and race/ethnicity, and accounted for clustering within schools. RESULTS: Among 646 students who reported using school vending machines, 456 (71%) reported purchasing sugar-sweetened beverages. Overall, 977 students (66%) reported eating at a fast-food restaurant. Sugar-sweetened beverage intakes averaged 1.2 servings per day. In adjusted models, relative to no vending machine purchases, servings per day increased by 0.21 for one to three purchases per week (P=0.0057), and 0.71 with four or more purchases (P<0.0001). Relative to no fast-food restaurant visits, sugar-sweetened beverage servings per day increased by 0.13 with one visit per week (P=0.07), 0.49 with two to three visits (P=0.0013), and by 1.64 with four or more visits (P=0.0016). CONCLUSIONS: Among students who use school vending machines, more report buying sugar-sweetened beverages than any other product category examined. Both school vending machine and fast-food restaurant use are associated with overall sugar-sweetened beverage intake. Reduction in added dietary sugars may be attainable by reducing use of these sources or changing product availability.

Adolescent↗

PubMed2004

Anomalous dissolution behaviour of tablets prepared from sugar glass-based solid dispersions.

In this study, anomalous dissolution behaviour of tablets consisting of sugar glass dispersions was investigated. The poorly aqueous soluble diazepam was used as a lipophilic model drug. The release of diazepam and sugar carrier was determined to study the mechanisms governing dissolution behaviour. The effect of carrier dissolution rate and drug load was tested with four different sugars, in the order of decreasing dissolution rates: sucrose, trehalose and two oligo-fructoses; inulinDP11 and inulinDP23 having a number average degree of polymerization (DP) of 11 and 23, respectively. Diazepam was incorporated in these sugar glasses in the amorphous state by means of freeze drying using water and tertiary butyl alcohol (TBA) as solvents. None of the tablets disintegrated during dissolution. Dissolution of 80% of the lipophilic drug within 20 min was found when diazepam and sugar dissolution profiles coincided. The sugar carrier and diazepam dissolved at the same rate, which was constant in time and fast. This condition was met for relatively slow dissolving carriers like the inulins or for low drug loads. For relatively fast dissolving carriers like sucrose or trehalose with high drug loads, release profiles of diazepam and sugar did not coincide: diazepam dissolved much more slowly than the sugars. In case of non-coinciding release profiles, diazepam release was split into three phases. During the first phase non-steady-state dissolution was observed: diazepam release accelerated and a drug rich layer consisting of crystalline diazepam was gradually formed. This first phase determined the further release of diazepam. During the second phase a steady-state release rate was reached: zero-order release was observed for both drug and carrier. During this phase, the remaining (non-crystallised) solid dispersion is dissolved without the further occurrence of crystallisation. The third phase, starting when all carrier is dissolved, involved the very slow dissolution of crystallised diazepam, which was present either as the skeleton of a tablet resulting in a zero-order release profile or as separate particles dispersed in the dissolution medium resulting in a first-order release. To understand the anomalous dissolution behaviour, a model is proposed. It describes the phenomena during dissolution of amorphous solid dispersion tablets and explains that fast dissolution is observed for low drug loads or slow dissolving carriers like inulin.

Diazepam↗

PubMed2001

Role of the sugar moiety in the pharmacological activity of anthracyclines: development of a novel series of disaccharide analogs.

The sugar moiety is an essential component of anthracycline antibiotics for their topoisomerase poisoning activity and antitumor efficacy. Since the sugar interacts with the minor groove, modifications in this moiety could enhance the recognition potential of the drug at the target level. Based on this hypothesis, novel anthracyclines, disaccharides lacking the amino group in the first (aglycone-linked) sugar, were designed. The 3'-amino group in the first sugar was replaced by an hydroxyl group, and the second sugar residue was bound to the first sugar via an alpha (1-4) linkage. The cytotoxic and antitumor activities of disaccharide analogs of idarubicin were critically dependent on the optimal (axial) orientation of the second sugar residue. Although configurational requirements of the sugar moiety for optimal drug activity support a critical role of the external (non-intercalating) drug domains in the interaction of anthracyclines with the DNA-topoisomerase (ternary complex), the antitumor efficacy of disaccharide analogs is not fully explained by effects mediated by the nuclear enzyme target. The development of this novel disaccharide series may provide insights for a rational synthesis of anthracycline analogs with improved pharmacological profile.

Anthracyclines↗

PubMed2003

Protein in sugar films and in glycerol/water as examined by infrared spectroscopy and by the fluorescence and phosphorescence of tryptophan.

Sugars are known to stabilize proteins. This study addresses questions of the nature of sugar and proteins incorporated in solid sugar films. Infrared (IR) and Raman spectroscopy was used to examine trehalose and sucrose films and glycerol/water solvent. Proteins and indole-containing compounds that are imbedded in the sugar films were studied by IR and optical (absorption, fluorescence, and phosphorescence) spectroscopy. Water is able to move in the sugar films in the temperature range of 20-300 K as suggested by IR absorption bands of HOH bending and OH stretching modes that shift continuously with temperature. In glycerol/water these bands reflect the glass transition at approximately 160 K. The fluorescence of N-acetyl-L-tryptophanamide and tryptophan of melittin, Ca-free parvalbumin, and staphylococcal nuclease in dry trehalose/sucrose films remains broad and red-shifted over a temperature excursion of 20-300 K. In contrast, the fluorescence of these compounds in glycerol/water solvent shift to the blue as temperature decreases. The fluorescence of the buried tryptophan in Ca-bound parvalbumin in either sugar film or glycerol/water remains blue-shifted and has vibronic resolution over the entire temperature range. The red shift for fluorescence of indole groups exposed to solvent in the sugars is consistent with the motion of water molecules around the excited-state molecule that occurs even at low temperature, although the possibility of static complex formation between the excited-state molecule and water or other factors is discussed. The phosphorescence yield for protein and model indole compounds is sensitive to the matrix glass transition. Phosphorescence emission spectra are resolved and shift little in different solvents or temperature, as predicted by the small dipole moment of the excited triplet state molecule. The conclusion is that the sugar film maintains the environment present at the glass formation temperature for surface Trp and amide groups over a wide temperature excursion. In glycerol/water these groups reflect local changes in the environment as temperature changes.

Biophysical Phenomena↗

PubMed1999

The role of O-linked sugars in determining the very low density lipoprotein receptor stability or release from the cell.

The very low density lipoprotein receptor is a member of the low density lipoprotein receptor supergene family for which two isoforms have been reported, one lacking and the other containing an O-linked sugar domain. In order to gain insight into their functionality, transient and stable transformants separately overexpressing previously cloned bovine variants were analyzed. We report evidence that the variant lacking the O-linked sugar domain presented a rapid cleavage from the cell and that a large amino-terminal very low density lipoprotein receptor fragment was released into the culture medium. As only minor proteolysis was involved in the other very low density lipoprotein receptor variant, the clustered O-linked sugar domain may be responsible for blocking the access to the protease-sensitive site(s). To test this hypothesis, a mutant Chinese hamster ovary cell line, ldlD, with a reversible defect in the protein O-glycosylation, was used. The instability of the O-linked sugar-deficient very low density lipoprotein receptor on the cell surface was comparable to that induced by the proteolysis of the variant lacking the O-linked sugar domain. Moreover, our data suggest that the O-linked sugar domain may also protect the very low density lipoprotein receptor against unspecific proteolysis. Taken together, these results indicate that the presence of the O-linked sugar domain may be required for the stable expression of the very low density lipoprotein receptor on the cell surface and its absence may be required for release of the receptor to the extracellular space. The exclusive expression of the variant lacking the O-linked sugar domain in the bovine aortic endothelium opens new perspectives in the physiological significance of the very low density lipoprotein receptor.

Animals↗

PubMed1998

Dietary specific sugars for serum protein enzymatic glycosylation in man.

All glycoprotein sugars can theoretically derive from glucose. However, dietary specific sugars could represent preferential substrates or have regulatory roles in enzymatic glycosylation. This hypothesis was tested in man using stable isotopes. Healthy subjects ingested different amounts (150, 300, or 550 mg) of artificially 13C-enriched sugar (galactose, mannose, or glucose) diluted in 200 mL water containing 50 g 13C-poor sucrose. 13C enrichment of expired CO2 was monitored for 8 hours during indirect calorimetry. Serum glycoproteins were precipitated and delipidated at various intervals. Glycoprotein neutral sugars were obtained by acidic hydrolysis, purified by ion-exchange chromatography, derivatized to alditol acetates, and analyzed by gas chromatography-isotope ratio mass spectrometry. The oxidation rate for galactose and mannose was slower than the rate for glucose. Total oxidation over the 8-hour period was less than 10% of the ingested amount of galactose or mannose. Galactose and mannose were readily incorporated into glycoprotein glycans, in the native form or after interconversion, despite ingestion of a large excess of sucrose: glycoprotein sugar 13C enrichment was strongly higher after 13C-galactose or 13C-mannose than after 13C-glucose. Thus, the metabolism of these three sugars appears to be different. Specific dietary sugars could represent a new class of non essential nutrients displaying interesting metabolic roles. This could have practical consequences especially in parenteral nutrition, where glucose is currently the only sugar available for metabolism.

Adult↗

PubMed1998

Availability of specific sugars for glycoconjugate biosynthesis: a need for further investigations in man.

We review the metabolism of specific sugars used for protein glycosylation, focusing on the fate of exogenously provided sugars. Theoretically, all glycoprotein sugars can derive from glucose, but previous studies show that other exogenous sugars can be incorporated into glycoproteins. From data obtained in congenital galactosemia, exogenous galactose may be important for correct glycosylation. Contrary to galactose, the metabolism of other sugars seems to depend on insulin regulation: stimulation of their endogenous production in diabetic subjects might participate in some diabetic complications, precluding the need for an exogenous supply. The metabolic fate of these sugars is different according to the administration route and exogenous supply may be important either in enteral nutrition or in some clinical situations as has been suggested for sialic acid in the newborn. Data in man are too sparse to reach firm conclusions, implying a need for further investigations. Our preliminary results in animals and man demonstrate that stable isotope methodology allows one to trace glycoprotein sugar metabolism in nutritionally relevant conditions with accuracy and sensitivity, using doses of specific sugars well below toxic levels.

Animals↗

PubMed2000

The use of different sugars as fine and coarse carriers for aerosolised salbutamol sulphate.

The aim of this study was to investigate the dispersion and deaggregation of a model drug, salbutamol sulphate (SS), using lactose, mannitol or sorbitol as coarse and fine carriers. Binary and tertiary formulations containing micronised salbutamol sulphate (SS) and sieved (63-90 microm) coarse sugar crystals or salbutamol sulphate (SS) with a mixture of coarse and fine sugar particles were prepared. Factorial design was employed to investigate the effects of three variables, i.e. the chemical entity of the coarse sugar carrier, the chemical entity of the fine sugar and the concentration of fine sugar, on the dispersion and deaggregation of salbutamol sulphate after aerosolisation at 60 l/min via a Rotahaler(R) into a twin stage liquid impinger (TSI). The binary formulations containing the different sugar entities produced differences in the fine (<6.4 microm) particle fraction (FPF) of SS in a decreasing order of mannitol >sorbitol >lactose, but failed to produce efficient dispersion of SS since the FPF was <10%. Adding fine sugar particles and increasing their concentration to the binary mixtures generally resulted in an increase in the FPF of salbutamol sulphate. The chemical nature of the fine carriers was found to play a less important role in determining respirable fraction of the drug than the coarse carriers. In conclusion, other sugars such as mannitol or sorbitol, besides lactose, may be employed as coarse and/or fine carriers for incorporation into dry powder aerosol formulations to increase FPF.

Aerosols↗

PubMed1975

Studies on the fortification of cane sugar with iron and ascorbic acid.

1. The feasibility of improving iron nutrition by fortifying cane sugar with Fe and ascorbic acid was studied. 2. It was found to be possible to add a number of Fe salts together with ascorbic acid to sugar without affecting its appearance or storage properties. 3. The absorption of Fe from fortified sugar eaten with maize-meal porridge or made into jam or biscuits was measured in ninety-four volunteer multiparous Indian women using the 59-Fe erythrocyte utlization method. 4. The absorption of Fe from sugar fortified with ascorbic acid and ferrous sulphate and eaten with maize-meal porridge was increased about twofold in the ratio, ascorbic acid:Fe was 10:1 by weight. If the ratio was increased to 20:2, Fe absorption was increased a further threefold. 5. Sugar fortified with soluble Fe salts, including FeSO4.7H2O, discoloured both tea and coffee; sugar fortified with ferric orthophosphate did not have this effect. 6. Fe from FePO4.H2O was poorly absorbed when added with sugar to maize-meal porridge, and also when added with adequate quantities of ascorbic acid. This form of Fe was absorbed much less well than was the intrinsic Fe present in the maize. 7. When sugar fortified with FePO4.H2O and ascorbic acid was added to maize-meal porridge before cooling or was made into jam there was a several-fold increase in the amount of Fe absorbed.

Adult↗

PubMed1991

Structural study of the sugar chains of human leukocyte cell adhesion molecules CD11/CD18.

Leu-CAMs (CD11/CD18) consisting of LFA-1, Mac-1, and p150/95 are leukocyte cell surface glycoproteins that are involved in various leukocyte functions. The asparagine-linked sugar chains were released as oligosaccharides from Leu-CAMs by hydrazinolysis. About 12 mol of sugar chains was released from 1 mol of Leu-CAMs. These sugar chains were converted to radioactive oligosaccharides by reduction with sodium borotritide and separated into neutral and acidic fractions by paper electrophoresis. All of the acidic oligosaccharides were converted to neutral ones by digestion with sialidase, indicating that they are sialyl derivatives. The neutral and sialdase-treated acidic oligosaccharides were fractionated by chromatography on lectin columns followed by Bio-Gel P-4 column chromatography. Structural studies of each oligosaccharide by sequential exo- and endoglycosidase digestion and by methylation analysis revealed that Leu-CAMs contain mainly high mannose type and high molecular weight complex type sugar chains. The latter sugar chains were of bi-, tri-, and tetraantennary complex types with the Gal beta 1----4(Fuc alpha 1----3)GlcNAc beta 1----and/or the Gal beta 1----3GlcNAc beta 1----groups together with the Gal beta 1----4GlcNAc group in their outer-chain moieties. In addition to these sugar chains, a small amount of monoantennary complex type and hybrid type sugar chains was found in Leu-CAMs. Furthermore, analysis of the asparagine-linked sugar chains released from the beta-subunit of Leu-CAMs by a series of lectin chromatography showed that subunit-specific glycosylation is not observed between the alpha- and beta-subunits of Leu-CAMs.

Antigens, CD↗

PubMedDate not supplied

Sugar metabolic analysis of suspensions of plant cells using an FT-IR/ATR method.

A simple, rapid and accurate evaluation of the sugar uptake rate of suspended plant cells from culture media was developed with the predicted sugar contents measured by mid-infrared spectroscopy using a Fourier transform infrared (FT-IR) spectrometer equipped with an attenuated total reflectance (ATR) accessory. We performed plant cell cultivation with Nicotiana tabacum cv. Bright Yellow No.2 (TBY-2) in culture media, which had various combinations of glucose, fructose and sucrose concentrations at the initial stage, and measured simultaneously each sugar content in the medium by the FT-IR/ATR method. By applying a logistic function to the predicted sugar contents and cell density in the medium during cultivation, the specific sugar uptake rates by the suspended TBY-2 cells were easily and continuously obtained. Thus the kinetic sugar uptake phenomena by the TBY-2 cells were well confirmed overall using the developed method. Additionally it was found that the fraction of sucrose of the initial total sugar content might kinetically affect the sugar uptake process and cell growth. Also, the relationship between the nondimensional cell density and sucrose content could be classified into three groups on the basis of the initial fraction of sucrose.

Carbohydrate Metabolism↗

PubMed2005

Carbohydrate-based DNA ligands: sugar-oligoamides as a tool to study carbohydrate-nucleic acid interactions.

Sugar-oligoamides have been designed and synthesized as structurally simple carbohydrate-based ligands to study carbohydrate-DNA interactions. The general design of the ligands 1-3 has been done as to favor the bound conformation of Distamycin-type gamma-linked covalent dimers which is a hairpin conformation. Indeed, NMR analysis of the sugar-oligoamides in the free state has indicated the presence of a percentage of a hairpin conformation in aqueous solution. The DNA binding activity of compounds 1-3 was confirmed by calf thymus DNA (ct-DNA) NMR titration. Interestingly, the binding of the different sugar-oligoamides seems to be modulated by the sugar configuration. Semiquantitative structural information about the DNA ligand complexes has been derived from NMR data. A competition experiment with Netropsin suggested that the sugar-oligoamide 3 bind to DNA in the minor groove. The NMR titrations of 1-3 with poly(dA-dT) and poly(dG-dC) suggested preferential binding to the ATAT sequence. TR-NOE NMR experiments for the sugar-oligoamide 3-ct-DNA complex both in D(2)O and H(2)O have confirmed the complex formation and given information on the conformation of the ligand in the bound state. The data confirmed that the sugar-oligoamide ligand is a hairpin in the bound state. Even more relevant to our goal, structural information on the conformation around the N-glycosidic linkage has been accessed. Thus, the sugar asymmetric centers pointing to the NH-amide and N-methyl rims of the molecule have been characterized.

Amides↗

PubMed2003

Enzymic release of reducing sugars from oat hulls by cellulase, as influenced by Aspergillus ferulic acid esterase and trichoderma xylanase.

Hydroxycinnamic acids, mainly ferulic and p-coumaric acids, are believed to be inhibitory to ruminal biodegradability of complex cell wall materials such as oat hulls. Previous studies have shown that a novel enzyme, Aspergillus ferulic acid esterase, and Trichoderma xylanase act synergistically to break the ester linkage between ferulic acid and the attached sugar of feruloyl polysaccharides, releasing ferulic acid from oat hulls. In this paper, we examined the enzymic release of reducing sugars from oat hulls by the actions of individual enzymes (Aspergillus ferulic acid esterase at 13 mU, 6.4 U, and 4678.4 U/assay; cellulase at 20 levels, ranging from 7.8 mU to 2772.7 U/assay; Trichoderma xylanase at 20 levels, ranging from 7.8 mU to 4096 U/assay) and by the combined action of cellulase at six levels (62.5 mU, 2 U, 16 U, 128 U, 1024 U, and 2772.7 U/assay), Aspergillus ferulic acid esterase at 13 mU/assay, and Trichoderma xylanase at two levels (1 U and 256 U/assay). The amount of total acid-extractable reducing sugars in the oat hulls used in this study was 793.8 +/- 8.0 microg/mg. The results show that after a 24-h incubation with Aspergillus ferulic acid esterase alone, no reducing sugars were observed to be released from oat hulls. With cellulase as the sole enzyme, as the concentration increased from 7.8 mU to 2772.7 U/assay, the release of reducing sugars increased (P < 0.01) from 0 to 39% of the total present, with the highest release at 512 U/assay. With Trichoderma xylanase alone, as the concentration increased from 7.8 mU to 4096 U/assay, the release of reducing sugars increased (P < 0.01) from 4.9 to 33%, with the highest release at 2048 U/assay. When incubated together with Trichoderma xylanase (1 U or 256 U/assay) and Aspergillus ferulic acid esterase (13 mU/assay), cellulase at all six levels (62.5 mU, 2 U, 16 U, 128 U, 1024 U and 2772.7 U/assay) significantly increased the release of reducing sugars (P < 0.01) from 8 to 69%. These results indicate that the synergistic interaction between Aspergillus ferulic acid esterase and Trichoderma xylanase on the release of ferulic acid from feruloyl polysaccharides of oat hulls makes the remainder of the polysaccharides open for further hydrolytic attack and facilitates the accessibility of the main chain of polysaccharides to cellulase. This action extends the cell wall hydrolysis, thus releasing a higher yield of reducing sugars. Such enzymic pretreatment of oat hulls may provide a unique advantage to rumen microorganisms for the biodegradation of the complex cell walls of byproduct feeds such as oat hulls.

Aspergillus↗