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At least 613 records · Page 34Linked to original sources

PubMed1993

Structural analysis of O-linked sugar chains in human blood clotting factor IX.

Type and structural analysis of O-linked sugar chains in human blood clotting factor IX was performed by the pyridylamination method developed for O-linked sugar chains [Kuraya, N. & Hase, S. (1992) J. Biochem. 112, 122-126]. O- and N-linked sugar chains were released with hydrazine, and then N-acetylated, followed by pyridylamination. The type of sugar chain was determined by reducing-end analysis of the pyridylaminated (PA-) sugar chains. Sugar chains with PA-GalNAc at the reducing terminal and that with PA-Fuc [Nishimura, H. et al. (1992) J. Biol. Chem. 267, 17520-17525] were obtained besides known sugar chains with PA-Glc from the Xyl-Glc-Ser type and those with PA-GlcNAc from asparagine-linked sugar chains. The sugar chains with PA-GalNAc were identified as mono- and disialyl Gal beta 1-3GalNAc by two-dimensional HPLC mapping. The structure of the sugar chain with PA-Fuc was Neu5Ac alpha 2-6Gal beta 1-4GlcNAc beta 1-3Fuc, as determined by exoglycosidase digestion, methylation analysis, and Smith degradation.

Carbohydrate Conformation↗

PubMed2003

Changes in fruit sugar concentrations in response to assimilate supply, metabolism and dilution: a modeling approach applied to peach fruit (Prunus persica).

The influence of assimilate supply, metabolism and dilution on sugar concentrations in the mesocarp of peach (Prunus persica (L.) Batsch) fruit during the main stage of fruit enlargement was analyzed with the SUGAR model of Génard and Souty (1996). The model predicts the partitioning of carbon into sucrose, sorbitol, glucose and fructose in the mesocarp of peach fruit. Based on measured data and the model, we determined values for the relative rates of sugar transformation. These rates were constant, varied with time or varied with relative fruit growth rate, depending on the type of sugar. Equations were derived to describe these rates and incorporated into the SUGAR model. The model simulated the effects of changing assimilate supply and fruit volume on sugar concentrations. The set of equations for the SUGAR model was rewritten to include the three components influencing sugar concentrations: assimilate supply, metabolism and dilution. The sugar types differed in sensitivity to these components. Sucrose was highly sensitive to changes in assimilate supply and to the dilution effect; it was not subject to intense metabolic transformation. Sorbitol was the most important carbohydrate in fruit metabolism, which explains why the sorbitol concentration was always low despite the strong positive effect of assimilate supply. The reducing sugars constituted a transitory storage pool and their concentrations were closely related to metabolism.

Carbohydrates↗

PubMed1998

Approximal caries and sugar consumption in Icelandic teenagers.

The aim of this study, conducted in 1994, was to examine the association between approximal caries and sugar consumption in teenagers residing in three fluoride-deficient areas in Iceland while controlling for a number of behavioral, residential and microbiological factors. One hundred and fifty subjects (mean age 14 years) selected from the Icelandic Nutritional Survey (INS) were examined radiographically and they completed questionnaires about sugar consumption frequency. Total grams of sugar intake were obtained from the INS for each subject. Caries experience on approximal surfaces, diagnosed from radiographs, was used as the dependent variable in the analyses. Altogether 45.2% of subjects were caries free on approximal surfaces. The overall sample was found to have a mean DFS on approximal surfaces of 2.73 (s=4.36) per subject. Average daily total sugar intake was 170 g per subject and the mean number of sugar-eating occasions between meals was 5.32 (s=6.29) per subject. The regression model indicated that the frequency of between-meal sugar consumption was associated with approximal caries, with frequency of candy consumption being the most important of the sugar variables. In multivariate analysis, no relationship was found between dental caries and total daily intake of sugar, although a significant relationship between total sugar consumption and presence of caries was seen in bivariate analysis. Between-meal consumption of sugar remains a risk factor for the occurrence of dental caries, especially in populations with moderate-to-high levels of dental caries experience.

Adolescent↗

PubMed1979

Determination of endotoxins in sugar with the Limulus test.

The Limulus amebocyte lysate test has been used for determination of pyrogens in sugar of different qualities. All the samples of domestic white sugar and beet raw sugar produced in Sweden during 1976 had a very low content of endotoxins, less than 10 ng/g of sugar. Imported cane raw sugar was, however, highly contaminated. The highest value obtained corresponds to about 100 mg of Escherichia coli endotoxin per g of raw sugar. Such crude sugar cannot, even after refining, be used for medical purposes. Instead, Swedish beet sugar is used as the raw material for production of invert sugar solutions for parenteral administration. The amount of endotoxin in this sugar is less than 1 ng/g.

Carbohydrates↗

PubMed1978

Catabolite inhibition and sequential metabolism of sugars by Streptococcus lactis.

Growth of galactose-adapted cells of Streptococcus lactis ML(3) in a medium containing a mixture of glucose, galactose, and lactose was characterized initially by the simultaneous metabolism of glucose and lactose. Galactose was not significantly utilized until the latter sugars had been exhausted from the medium. The addition of glucose or lactose to a culture of S. lactis ML(3) growing exponentially on galactose caused immediate inhibition of galactose utilization and an increase in growth rate, concomitant with the preferential metabolism of the added sugar. Under nongrowing conditions, cells of S. lactis ML(3) grown previously on galactose metabolized the three separate sugars equally rapidly. However, cells suspended in buffer containing a mixture of glucose plus galactose or lactose plus galactose again consumed glucose or lactose preferentially. The rate of galactose metabolism was reduced by approximately 95% in the presence of the inhibitory sugar, but the maximum rate of metabolism was resumed upon exhaustion of glucose or lactose from the system. When presented with a mixture of glucose and lactose, the resting cells metabolized both sugars simultaneously. Lactose, glucose, and a non-metabolizable glucose analog (2-deoxy-d-glucose) prevented the phosphoenolpyruvate-dependent uptake of thiomethyl-beta-d-galactopyranoside (TMG), but the accumulation of TMG, like galactose metabolism, commenced immediately upon exhaustion of the metabolizable sugars from the medium. Growth of galactose-adapted cells of the lactose-defective variant S. lactis 7962 in the triple-sugar medium was characterized by the sequential metabolism of glucose, galactose, and lactose. Growth of S. lactis ML(3) and 7962 in the triple-sugar medium occurred without apparent diauxie, and for each strain the patterns of sequential sugar metabolism under growing and nongrowing conditions were identical. Fine control of the activities of preexisting enzyme systems by catabolite inhibition may afford a satisfactory explanation for the observed sequential utilization of sugars by these two organisms.

Biological Transport↗

PubMed1977

Sugar interaction with the antiluminal surface of the proximal tubule in dog kidney.

The pulse-injection multiple-indicator-dilution technique in vivo has been used to investigate bidirectional sugar interaction with the antiluminal surface of the nephron in dog kidney. Simultaneous renal vein and urine outflow curves were obtained for radiolabeled sugars known to interact with the antiluminal surface. The following sugars were tested relative to T-1824 albumin (plasma reference) and creatinine (extracellular reference) under conditions of high-dose phlorizin preloading (75-225 mg/kg): D-glucose, D-xylose, D-fucose, D-mannose, D-galactose, L-arabinose, myoinositol, and D-fructose. The results indicate that as the plasma concentration of phlorizin increases there is, first, a partial inhibition of sugar interaction at the antiluminal membrane so that only unidirectional uptake of sugar from blood to tubular cell is observed, followed by complete inhibition of sugar interaction at the peritubular face of the antiluminal membrane, resulting in superposition of sugar and creatinine curves in the renal vein effluent. Two possible interpretations exist. i) Phlorizin exerts its inhibitory action successively at the cytoplasmic and then at the peritubular face of the antiluminal membrane. Moreover, since all of the sugar substrates are inhibited by phlorizin, the data suggest that the sugar-membrane interaction takes place at a common site at the level of the proximal tubule. ii) Alternatively, the action of phlorizin could result from a metabolic inhibitory effect affecting multiple sugar transport systems at the antiluminal membrane.

Animals↗

PubMed1996

Are high-fat, high-sugar foods and diets conducive to obesity?

Restriction of both dietary fat and extrinsic sugars is standard advice for weight reduction. It has been suggested that foods, and diets, that combine high levels of sugars and fat particularly contribute to overconsumption. Weighed dietary data on 1087 men and 1110 women aged 16-64 who took part in the Dietary and Nutritional Survey of British Adults were examined for evidence of this hypothesis. Consumption of the main sugary fatty foods (cakes, biscuits, confectionery and puddings) averaged 12% of energy for men, 14.9% for women. Intake of these foods (as a proportion of total energy) was inversely related to BMI (adjusted for age and smoking). After exclusion of the substantial number who were dieting or unwell or who may have under-reported their intakes, the association remained significant only in men. Consumption of sugary fatty foods showed a positive association with intakes of fibre, a negative association with vegetables and no relationship with percentage of energy from fat. For the investigation of diet composition, men and women were divided into four groups, high or low in extrinsic sugars energy (cut point 15%) and fat energy (cut point 40%). For men consuming high fat diets (> 40% energy) mean BMI was higher in the low sugar group. After exclusion of dieters and unwell, men with low sugar intakes still had a higher mean BMI than men with high sugar intakes. BMI and extrinsic sugars energy were still negatively but weakly correlated (r = -0.10; P < 0.05) after adjusting for age, smoking, energy, fat intake, and dieting/under-reporting. In conclusion, there is little evidence in this cross-sectional survey that either sugary fatty foods, or diets high in sugars, are associated with obesity. Rather, sugars appear to have a weak negative association with BMI that is not totally explained by confounders such as dieting, under-reporting or the inverse correlation between energy from sugars and fat.

Adolescent↗

PubMed2000

Inter-conversion of free sugars and accumulation of galactomannan in response to supplied metabolic mediators during pod filling in guar.

Detached inflorescences of guar (Cyamopsis tetragonoloba), each bearing 4 uniformly-developing pods at 42 days post anthesis (DPA), were cultured for 6 days in complete liquid medium manipulated with a fixed concentration of mannose and varying concentration of myo-inositol. Such inflorescences, but with 2 pods, were also maintained in the solutions of (i) glucose(U-14C) containing myo-inositol or phytohormones, and (ii) mannose(U-14C) containing galactose for 36 hr. Effect of such exogenously supplied metabolic mediators on interconversion of free sugars in pod wall, endosperm and cotyledons and galactomannan accumulation in endosperm was studied. Myo-inositol decreased, over control, the relative proportion of invert sugars in pod wall, endosperm and cotyledons and at lower concentration (27.75 mM) it decreased the level of free sugars in pod wall and galactomannan in endosperm. In all pod tissues, 14C from both glucose and mannose got incorporated into myo-inositol as well as various sugars and maximum incorporation occurred in sucrose. High concentration of total free sugars and their 14C activity in pod wall indicated that this pod tissue was a potent accumulator of free sugars. With myoinositol, the relative proportion of 14C from glucose into raffinose sugars of pod wall and endosperm increased with a simultaneous decrease in this incorporation into galactomannan of the latter. Accompanying this, relative proportion of 14C into hexoses and myo-inositol decreased in pod tissues. Galactose increased 14C incorporation from mannose into total free sugars, sucrose and galactomannan with a concomitant decline in the labelling of hexoses. IAA and ABA enhanced 14C incorporation from glucose into total free sugars and this enhancement was much higher with IAA than ABA. The latter inhibited 14C incorporation into galactomannan. Based on these results, it was suggested that myo-inositol at lower concentration was inadequate to mediate the metabolism of sugars and, thereby, galactomannan synthesis. Galactose and mannose exhibited a mutual beneficial effect on their transportation to pods. Phytohormones stimulated the accumulation of sucrose in pod wall for its obligatory unloading into the seed.

Abscisic Acid↗

PubMedDate not supplied

Detection of added beet or cane sugar in maple syrup by the site-specific deuterium nuclear magnetic resonance (SNIF-NMR) method: collaborative study.

Results of a collaborative study are reported for the detection of added beet or cane sugar in maple syrup by the site-specific natural isotope fractionation-nuclear magnetic resonance (SNIF-NMR) method. The method is based on the fact that the deuterium content at specific positions of the sugar molecules is different in maple syrup from that in beet or cane sugar. The syrup is diluted with pure water and fermented; the alcohol is distilled with a quantitative yield and analyzed with a high-field NMR spectrometer fitted with a deuterium probe and fluorine lock. The proportion of ethanol molecules monodeuterated at the methyl site is recorded. This parameter (D/H)I is decreased when beet sugar is added and increased when cane sugar is added to the maple syrup. The precision of the method for measuring (D/H)I was found to be in good agreement with the values already published for the application of this method to fruit juice concentrates (AOAC Official Method 995.17). An excellent correlation was found between the percentage of added beet sugar and the (D/H)I isotopic ratio measured in this collaborative study. Consequently, all samples in which exogenous sugars were added were found to have a (D/H)I isotopic ratio significantly different from the normal value for an authentic maple syrup. By extension of what is known about plants having the C4 cycle, the method can be applied to corn sweeteners as well as to cane sugar. One limitation of the method is its reduced sensitivity when applied to specific blends of beet and cane sugars or corn sweeteners. In such case, the C13 ratio measurement (see AOAC Official Method 984.23, Corn Syrup and Cane Sugar in Maple Syrup) may be used in conjunction.

Algorithms↗

PubMed2004

[Soluble sugar content of clonal plant Neosinocalamus affinis at module and ramet levels].

In this paper, soluble sugar content of Neosinocalamus affinis was measured by anthrone colorimetry at two levels of module and ramet in order to reveal its ecological and physiological adaptability. The results showed that soluble sugar content decreased in the order of leaf > branch > culm. As for soluble sugar content, different modules responded to ramet age and position in different ways. The branch and culm of 1-year-old ramets contented more soluble sugar than those of other four ages, but soluble sugar content in leaf was independent to ramet age. For leaf and culm, lower parts of ramet contented more soluble sugar than middle and upper parts. Under high irradiance, the soluble sugar content of Neosinocalamus affinis leaf was more than that under low irradiance. Seasonal change had significant effect on soluble sugar content. The soluble sugar content of leaf presented a monthly change, with a bottom and upper value in January and in April, respectively, but there was no obvious difference between 2-year-old and 3-year-old ramets. The soluble sugar content of parent ramet leaves was positively correlative to that of daughter ramet in upper and middle parts of ramets. There was no significant difference between ramet ages at ramet level. Hierarchical response of physiological character to environmental changes existed at the module and ramet levels of Neosinocalamus affinis.

Glucose↗

PubMed2026

Phosphorylation and ubiquitination coordinate homeostasis of a tomato transporter responsible for fruit sugar accumulation.

Sugar transport mediated by different transporters is essential for maintaining sugar homeostasis in plants. Here, we report that phosphorylation and ubiquitination coordinate the homeostasis of a tomato (Solanum lycopersicum) sugar transporter SlSWEET16, revealing a new aspect of plant sugar homeostasis. SlSWEET16 is localized to plasma membrane and functions as a mono- and disaccharide transporter. SlSWEET16 mediates cellular sugar efflux, and CRISPR/Cas9-mediated knockout of SlSWEET16 leads to increased fruit sugar accumulation. Strikingly, the C-terminus of SlSWEET16 is subjected to both phosphorylation and ubiquitination. Two protein kinases including SlSnRK2.3 and SlSnRK2.4 associate with the C-terminus of SlSWEET16, resulting into an increase in the stability of SlSWEET16. Meanwhile, the C-terminus of SlSWEET16 also interacts with an E3 ubiquitin ligase SlTT3.1L2, which decreases the stability of SlSWEET16. SlSnRK2.3 and SlSnRK2.4 inhibit fruit sugar accumulation, whereas SlTT3.1L2 promotes it. Mutations of phosphorylated or ubiquitinated residues in SlSWEET16's C-terminus further corroborate the contribution of phosphorylation and ubiquitination to the stability of SlSWEET16 and fruit sugar accumulation. Our results reveal a multiple-protein regulatory module that integrates different post-translational modifications to control transporter-mediated fruit sugar accumulation.

Solanum lycopersicum↗

PubMed1989

Suppression of human natural killer cell activity by amino sugars.

In the present study we investigated the effect of amino sugars on human natural killer (NK) activity against K562, a human myeloid leukemia cell line, and Molt-4, a human T lymphoma cell line. The presence of amino sugars such as D-mannosamine, D-galactosamine, and D-glucosamine [6-25 mM (in the case of D-mannosamine, 1.5-12.5 mM)] in a 4-hr chromium-51 (Cr) release assay significantly inhibited NK activity of large granular lymphocytes (LGL) without affecting effector cell viability or spontaneous release from target cells. Sugars with acetylated amino residues (N-acetyl-D-mannosamine, N-acetyl-D-galactosamine, and N-acetyl-D-glucosamine) showed much smaller NK inhibition. Among the amino sugars tested, D-mannosamine was the strongest suppressor. When either LGL or K562 cells were pretreated with amino sugars and used in the 4-hr 51Cr release assay, only the pretreatment of effector cells resulted in the reduction of NK activity. The binding capacity of LGL to K562 cells, determined by a conjugate assay, was not reduced by the amino sugars enough to explain the strong inhibition of NK activity by these amino sugars, although some inhibitory effect on the binding of LGL to K562 cells was observed in some cases. In contrast, the polarization of the effector cell cytoskeleton, one of the energy-dependent steps, was significantly impaired. The cellular ATP level of LGL was also significantly reduced and the reduction of cellular ATP correlated well with the degree of the inhibition of NK cytotoxicity. These results suggest that the suppression of NK activity by amino sugars is due to the reduction of the ATP-based energy supply of the effector cells and that amino sugars, especially D-mannosamine, should be recognized as potent suppressors of natural cell-mediated immunity.

Adenosine Triphosphate↗

PubMed1990

Digestion and absorption in the human intestine of three sugar alcohols.

The digestion and absorption of three sugar alcohols, consumed chronically in three identical daily postprandial doses, were evaluated in six volunteers during three 11-day periods. Each period included a 3-day adaptation period during which sugar alcohol doses were increased, a 4-day equilibration period, a 2-day stool collection period, and a 2-day intubation period. From day 4, the daily administered amounts were either 30 g pure sorbitol, 57 g maltitol containing 30 g sorbitol, or 69 g Lycasin 80/55 (Roquette, Lestrem, France), which is a hydrogenated glucose syrup also containing 30 g sorbitol. The distal ileal output of sugar alcohols and their components was determined by aspiration after a single meal. The mean percentage of sorbitol absorbed in the small intestine was significantly higher in pure sorbitol doses than in those containing maltitol and Lycasin 80/55 (79% +/- 4% vs. 64% +/- 4% and 64% +/- 5%, mean +/- SEM). The mean percentage of total maltitol digested was not different for pure maltitol and maltitol contained in Lycasin 80/55 (90% +/- 2% vs. 86% +/- 2%). Stool excretion of sugar alcohols was negligible, indicating that the sugar alcohols reaching the colon were almost completely digested by the colonic flora. The mean estimated energy values of the sugar alcohols ingested in kcal/g were 3.58 +/- 0.08 for sorbitol, about 3.50 +/- 0.07 for maltitol, and between 3.11 +/- 0.08 and 3.54 +/- 0.08 for Lycasin 80/55. Because the experimental conditions of this study mimicked the usual way of consumption of the three sugar alcohols, little calorie saving can be expected from the chronic consumption of these sugar alcohols in so-called sugar-free products.

Adult↗

PubMed2006

Amino sugars: new inhibitors of zeaxanthin epoxidase, a violaxanthin cycle enzyme.

The effect of three sugars and their amino derivatives on violaxanthin cycle enzymes activity was investigated in duckweed (Lemna trisulca), a model water-plant. No effect of sugars and amino sugars on violaxanthin de-epoxidase was observed independent of incubation time; however, epoxidation of zeaxanthin to violaxanthin was inhibited. The minimum amino sugar concentrations causing maximum inhibition of zeaxanthin epoxidation have been estimated. Amino sugars but not sugars caused more than a 50% inhibition of zeaxanthin epoxidation in duckweed after a 24h incubation when applied at a concentration of 0.5%. Incubation with amino sugars under a 6d photoperiod enhanced the inhibitory effect. Zeaxanthin epoxidation was completely inhibited under such conditions, whereas only a minor inhibitory effect was observed in sugar treated plants. The strong amino sugar inhibition of zeaxanthin epoxidase activity represents additional evidence for the creation of an unstable carotenoid carbocation in the molecular mechanism of epoxidation.

Amino Sugars↗

PubMed1979

Preparatively useful reactions involving nitrogenous sugars and some applications with carbohydrate-containing antibiotics.

This work describes the development of useful synthetic methodology with simple sugars, practical applications for conversion of abundant precursors into modified sugars (especially amino and deoxy sugars) of importance in various groups of natural products, and the conversion of such products into compounds of biological or pharmacological interest, especially carbohydrate antibiotics and their analogs. Examples of synthetic methodology illustrate various routes to deoxygenated (saturated, alkenic, and acetylenic), and oxidized (carbonylic, aldehydic, and carboxylic) functionality from hydroxyl and amino precursors. Unusual modes of sugar protection by such procedures as kinetic acetonation are discussed, together with the use of diazo and hydrazino groups for access to novel structures, including extended carbon-chain sugars and sugar--heterocycle conjugates. The broad utility of 5-membered benzylidene acetals in regiospecific routes to alpha, beta-deoxycarbonyl sugars is the basis of general methodology for practical, large-scale synthesis of aminopolydeoxy sugars, with daunosamine as the prototype, of widely varied substitution-mode and stereochemistry. Implications of the foregoing are discussed in relation to several classes of antibiotics, especially the anthracyclines and analogs thereof. A range of 7-O-(amino sugar-substituted)daunomycinones have been synthesized, together with 3'-hydroxy-daunorubicin and adriamycin, and their antitumor and toxicological properties evaluated; prospects for useful total synthesis will be mentioned.

Amino Sugars↗

PubMed1982

Sugar substitutes: reasons and indications for their use.

Sugar alcohols such as sorbitol, xylitol, maltitol and hydrogenated starch and other sweeteners having more than one hundred times the sweetening power of sucrose, such as stevioside and thaumatin, are currently used as less or non-cariogenic sugar substitutes. A new product, coupling sugar, has been developed which is a sugar mixture of monosaccharides, glucosyl-sucrose, oligosaccharides and oligosaccharides terminated at the reducing end by sucrose. Its sweetness is between 55 and 65 per cent of that of sucrose. Coupling sugar has a sweet quality resembling that of sucrose and possesses its advantages as a food being both easily digested and a ready source of energy. Two coupling sugar preparations of different sugar composition (CSCP and CSSF) and maltosylsucrose, one of the main ingredients of coupling sugar, were studied to examine their cariogenicities as substrates both in vitro and in vivo. It was shown that, compared with sucrose, these substances were definitely low in cariogenic action. No deleterious effects of its use have been found. In Japan, coupling sugar is widely employed in the manufacture of candies, cookies, chocolates etc.

Animals↗

PubMed1999

Effect of sugars on the thermal and rheological properties of sago starch.

Studies have been undertaken to investigate the effect of sugars on the thermal and rheological properties of sago starch. Sugars were found to increase the gelatinization temperature T(gel), and gelatinization enthalpy DeltaH. T(gel) and DeltaH increased in the following order: control (water alone) < ribose < fructose < glucose < maltose < sucrose. The increase in DeltaH was greater for 50% starch compared to 10% starch samples. The swelling factors in the presence of sugar were higher compared to the control for sugar concentrations below 25% but were lower at sugar concentration greater than 25%. These effects are discussed in terms of the antiplaticizing effect of the sugars compared to water, the influence of sugar-starch interactions and also the effect of the sugars on water structure. The storage modulus G', the rate constant of gelation k, and the gel strength were significantly reduced in the presence of sugars. Generally G' and k decreased in the following order: control (water alone) > hexose > disaccharide > pentoses. This has been attributed to the reduced proportion of amylose leached following gelatinizatison. In the presence of hexoses the freeze-thaw stability of starch gels decreased while in the presence of disaccharides and pentoses the freeze-thaw stability was slightly improved.

Carbohydrates↗

PubMedDate not supplied

DNA bending induced by carbocyclic sugar analogs constrained to the north conformation.

DNA bending caused by introduction of carbocyclic sugars constrained to the north conformation was studied, using explicit solvent molecular dynamic (MD) simulations. The native Drew-Dickerson (DD) dodecamer and its three modifications containing north carbocyclic sugars in the 7th (T7*), 8th (T8*) or both 7th and 8th (T7T8*) nucleotide positions were examined. Introduction of the carbocyclic sugar results in A-form conformations for the alpha, beta, chi, zeta, and sugar pucker backbone parameters in the modified nucleotides. Increased steric repulsion between the sugar and its parent base in the modified oligonucleotides impacts the roll and cup dinucleotide step parameters, increasing the bending of the oligomer axis. Increased buckling of the substituted nucleotides disrupts the usual stabilizing base stacking interactions. The level of overall bending depends on the number and position of carbocyclic sugars introduced in the DNA sequence. Single sugar substitutions are unable to induce substantial bending due to the neighboring unmodified nucleotides counterbalancing the distortion. Significant bending can, however, be induced by two consecutive north sugars (T7T8*), which is in agreement with experimental results. The modified oligomers populate a wide range of bend angles, indicating that they maintain flexibility in the bent state. The present results suggest that insertion of carbocyclic sugars into DNA or RNA duplexes can be used to engineer bending of the duplexes without impacting the electrostatic or chemical properties of the phosphodiester backbone, thereby serving as excellent tools for experimental elucidation of nucleic acid structure-function relationships.

Base Pairing↗