Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “STARCH”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed1999

NMRD investigation of DyDTPA- and GdDTPA-labeled starch particles. Selection of a suitable suspension medium and influence of the starch matrix on relaxivity.

RATIONALE AND OBJECTIVES: The primary aim was to investigate the influence of the starch matrix on the T1 relaxivities of starch particles labeled with gadolinium and dysprosium diethylenetriamine pentaacetic acid (GdDTPA-SP and DyDTPA-SP). Achieving this required the selection of a medium that was suitable for suspending the particles and that had field-independent T1 relaxation rates, thereby eliminating errors in relaxivity determinations resulting from a field-dependent background. METHODS: GdDTPA-SP with low and high gadolinium content, DyDTPA-SP, and empty DTPA-SP were suspended in an aqueous medium containing 5% (w/w) of a polyethylene glycol-based block copolymer. 1/T1 NMRD profiles were obtained in the temperature range of 5 degrees to 35 degrees C. RESULTS: Using the block copolymer, particles did not settle, and samples could be prepared at a low temperature to avoid particle degradation, the intrinsic T1 relaxation rate of the suspension medium was field-independent and identical to that of water from 25 degrees to 35 degrees C. The T1 relaxivities of DyDTPA-SP were higher than those of dysprosium diethylenetriamine pentaacetate-bis(methylamide) (DyDTPA-BMA) and decreased with increasing magnetic field strength. The T1 relaxivity of GdDTPA-SP was higher than that of GdDTPA at all fields, and decreased with decreasing temperature and increasing gadolinium content. CONCLUSIONS: The GdDTPA-SP results showed that the particulate starch matrix served a dual role, with opposing influences on relaxivity. It provided a means for increasing the rotational correlation time (tau R), which resulted in higher relaxivities. However, it also retarded radial diffusion of water molecules within the particle interior, which significantly counteracted the enhancing effect of tau R. For DyDTPA-SP, the starch matrix provided an additional diamagnetic contribution, resulting in relaxivities higher than those of DyDTPA-BMA. The block copolymer was suitable as a suspension medium for DyDTPA-SP and GdDTPA-SP and should also be applicable for other particulates.

Contrast Media↗
PubMed2003

Effects of starches on the mechanical properties of paracetamol tablet formulations. II. Sorghum and plantain starches as disintegrants.

This study evaluates the disintegrant properties--tablet disintegration time (DT) and crushing strength--friability/disintegration time (CSFR/DT) ratio of a paracetamol tablet formulation prepared with sorghum and plantain starches in comparison with corn starch BP. The effects of disintegrant concentration, relative density of tablets and the mode of disintegrants addition were studied. The study revealed that the rank order of effectiveness of the starches as disintegrants was corn > plantain > sorghum. The mode of addition of disintegrants, disintegrant concentration and relative density had a significant impact on the disintegrant properties. The tested starches, namely, sorghum and plantain, showed promising results.

Acetaminophen↗
PubMed2003

The effects of starches on mechanical properties of paracetamol tablet formulations. I. Pregelatinization of starch binders.

A study has been made of the effects of pregelatinization of native sorghum and plantain starches on the mechanical properties of a paracetamol tablet formulation in comparison with corn starch BP. The mechanical properties tested, viz. tensile strength (T) and brittle fracture index (BFI) of the paracetamol tablets were affected by pregelatinization of the starch. The results suggest that pregelatinized starches may be useful as binders when a particular degree of bond strength and brittleness is desired.

Acetaminophen↗
PubMed2006

Starch-synthase III family encodes a tandem of three starch-binding domains.

The starch-synthase III (SSIII), with a total of 1025 residues, is one of the enzymes involved in plants starch synthesis. SSIII from Arabidopsis thaliana contains a putative N-terminal transit peptide followed by a 557-amino acid SSIII-specific domain (SSIII-SD) with three internal repeats and a C-terminal catalytic domain of 450 amino acids. Here, using computational characterization techniques, we show that each of the three internal repeats encodes a starch-binding domain (SBD). Although the SSIII from A. thaliana and its close homologous proteins show no detectable sequence similarity with characterized SBD sequences, the amino acid residues known to be involved in starch binding are well conserved.

Amino Acid Sequence↗
PubMed1996

The starch phosphorylase gene is subjected to different modes of regulation in starch-containing tissues of potato.

Analysis of the levels of starch phosphorylase mRNA and its product in the various organs of the potato plant indicates that the gene is differentially regulated, leading to a high accumulation of the gene product in tubers. The amount of phosphorylase transcripts synthesized in nuclei isolated from tubers and leaves indicates that the difference in the steady-state levels of phosphorylase mRNA in these organs can be explained by different rates of initiation of transcription. However, while rates of initiation of transcription are similar in tubers and stems, the steady-state level of phosphorylase mRNA is much lower in the stem. Transgenic potato plants expressing the beta-glucuronidase (GUS) gene under the control of 5'-flanking sequences of the phosphorylase gene exhibited high levels of GUS activity in petioles, stems, stolons, tubers and roots, but low levels in leaves. This confirms the results of transcription assays observed for leaves, stems and tubers, and indicates that accumulation of phosphorylase mRNA in stems and tubers is not controlled solely by transcription initiation. Finally, histochemical analysis for GUS activity in transgenic potato plants suggests that transcription of the phosphorylase gene predominantly occurs in starch-containing cells associated to vascular tissues, and suggests a role for starch phosphorylase in the mobilization of starch stored along the translocation pathway.

Gene Expression Regulation, Enzymologic↗
PubMed1997

Meat, starch and non-starch polysaccharides, are epidemiological and experimental findings consistent with acquired genetic alterations in sporadic colorectal cancer?

International comparisons show strong inverse protective associations with starch, NSP (fibre, non-starch polysaccharides) and vegetable intakes, and positive associations with meat consumption in large bowel cancer. Estimates of relative risk from cohort investigations are in the same direction although generally weak, and red and processed meat, rather than white meat seem to be associated with elevated risk. A protective effect of starch and NSP probably arises from their marked effect on bacterial metabolism in the large bowel, which can be postulated to affect gene expression and DNA repair via increased butyrate production. Stool weight is also increased and pH reduced leading to alterations in secondary bile acid production, and mucosal cell proliferation. In rodent models, 'insoluble' sources of NSP are generally protective, although butyrate, resistant starch and soluble NSP may not reduce tumorigenesis. High levels of meat increase faecal ammonia and N-nitrosocompound (NOC) concentration. Some of the chromosomal mutations found in human colorectal cancer are consistent with effects of NOC and heterocyclic amines. More data are required from human experimental studies linking alterations in diet with known stages in carcinogenesis in the large bowel, and from large cohort studies which have collected biological samples in order that interaction between diet, biomarkers of diet, and different genotypes that may determine risk can be examined.

Animals↗
PubMed2006

Genotype-specific spatial distribution of starch molecules in the starch granule: a combined CLSM and SEM approach.

Starch granule types from a variety of botanical sources were selected to represent differences in crystalline polymorph, amylose and phosphate content, and amylopectin chain length distribution. Equimolar labeling of starch molecules with the fluorophore 8-amino-1,3,6-pyrenetrisulfonic acid (APTS) was used to construct a detailed map of the distribution of amylose and amylopectin within the granule by confocal laser scanning microscopy (CLSM) analysis. Medium- and high-resolution scanning electron microscopy (SEM) were used to provide detailed images of granule surface structures. By using a combined surface and internal imaging approach, interpretations of a number of previous structural observations is presented. In particular, internal images of high amylose maize and potato suggest that multiple initiations of new granules are responsible for the compound or elongated structures observed in these starches. CLSM optical sections of rice granules revealed an apparent altered distribution of amylose in relation to the proposed growth ring structure, hinting at a novel mechanism of starch molecule deposition. Well-described granule features, such as equatorial grooves, channels, cracks, and growth rings were documented and related to both the internal and external observations. A new method for probing the phosphate distribution in native granules was developed using a phosphate-binding fluorescent dye and CLSM.

Amylose↗
PubMed1990

Occurrence of an Affinity Site apart from the Active Site on the Raw-Starch-Digesting but Non-Raw-Starch-Adsorbable Bacillus subtilis 65 alpha-Amylase.

alpha-Cyclodextrin specifically inhibited raw starch digestion by Bacillus subtilis 65 alpha-amylase. The raw starch digestibility and alpha-cyclodextrin-Sepharose 6B adsorbability of this alpha-amylase were simultaneously lost when the specific domain corresponding to the affinity site essential for raw starch digestion was deleted by proteolysis. Occurrence of the affinity site on raw-starch-digesting enzymes was proven also with bacterial amylase.

Journal Article↗
PubMed2006

The effect of starch and starch-bioactive glass composite microparticles on the adhesion and expression of the osteoblastic phenotype of a bone cell line.

There is a clear need for the development of microparticles that can be used simultaneously as carriers of stem/progenitor cells and as release systems for bioactive agents, such as growth factors or differentiation agents. In addition, when thinking on bone-tissue-engineering applications, it would be very useful if these microparticles are biodegradable and could be made to be bioactive. Microparticles with all those characteristics could be cultured together with adherent cells in appropriate bioreactors to form in vitro constructs that can then be used in tissue-engineering therapies. In this work, we have characterized the response of MC3T3-E1 pre-osteoblast cells to starch-based microparticles. We evaluated the adhesion, proliferation, expression of osteoblastic markers and mineralization of cells cultured at their surface. The results clearly show that MC3T3-E1 pre-osteoblast cells adhere to the surface of both polymeric and composite starch-based microparticles and express the typical osteoblastic marker genes. Furthermore, the cells were found to mineralize the extracellular matrix (ECM) during the culture period. The obtained results indicate that starch-based microparticles, known already to be biodegradable, bioactive and able to be used as carriers for controlled release applications, can simultaneously be used as carriers for cells. Consequently, they can be used as templates for forming hybrid constructs aiming to be applied in bone-tissue-engineering applications.

Biocompatible Materials↗
PubMed1998

Thermodynamics of binding of heterobidentate ligands consisting of spacer-connected acarbose and beta-cyclodextrin to the catalytic and starch-binding domains of glucoamylase from Aspergillus niger shows that the catalytic and starch-binding sites are in close proximity in space.

The binding to glucoamylase 1 from Aspergillus niger (GA1) of a series of four synthetic heterobidentate ligands of acarbose and beta-cyclodextrin (beta-CD) linked together has been studied by isothermal titration calorimetry. GA1 consists of a catalytic and a starch-binding domain (SBD) connected by a heavily O-glycosylated linker region. Acarbose is a strong inhibitor of glucoamylase and binds exclusively in the catalytic site, while the cyclic starch mimic beta-CD binds exclusively to the two sites of SBD. No spacer or spacer arms of 14, 36, and 73 A in their extended conformations connect acarbose and beta-CD. These compounds were used as probes for bidentate ligand binding to both domains in order to estimate the distance between the catalytic site and the SBD binding site in solution. DeltaH of binding of the four heterobidentate ligands is within experimental uncertainty equal to the sum of DeltaH of binding of free acarbose and beta-CD, indicating ligand binding to both domains. However, the binding constants are 4-5 orders of magnitude smaller than for the binding of acarbose (K approximately 10(12) M-1), increasing with spacer length from 2 x 10(7) M-1 for no spacer to 1 x 10(8) M-1 for the 73 A spacer. Subsequent titrations with beta-CD of the glucoamylase-bidentate ligand complexes revealed that only one of the two binding sites of SBD was vacant. Further titrations with acarbose to these mixtures showed complete displacement of the acarbose moiety of the bidentate ligands from the catalytic sites. These experiments show that the bidentate ligands bind to both the catalytic domain and SBD. The weakening of the bidentate ligand binding compared to acarbose is a purely entropic effect point to steric hindrance between SBD and the beta-CD moiety. To test this, titrations of glucoamylase 2, a form containing the catalytic domain and the linker region but lacking SBD, with the bidentate ligands were carried out. The results were indistinguishable from the binding of free acarbose. Thus, the reduced affinity of the bidentate ligands observed with GA1 stems from interactions due to SBD. The results show that the catalytic and starch-binding sites are in close proximity in solution and thus indicate considerable flexibility of the linker region.

Acarbose↗
PubMedDate not supplied

Spherulitic crystallization in starch as a model for starch granule initiation.

The influence of cooling rate and quench temperature on the formation of spherulitic morphology in heated mung bean starch is reported. Spherulites were obtained for a wide range of cooling rates (2.5-250 degrees C/min), provided the system was heated to 180 degrees C and then cooled below 65 degrees C. Branched crystalline structures were also observed, as was a gellike morphology. The dissolution temperature for spherulitic material ranged between 100 and 130 degrees C. A second dissolution endotherm was observed between 130 and 150 degrees C in systems containing gellike material. Spherulites revealed B-type X-ray diffraction patterns. Spherulitic crystallization of starch following phase separation is proposed as a model for starch granule initiation in vivo.

Carbohydrate Conformation↗
PubMed2006

Starch properties of mutant rice high in resistant starch.

As the staple food of over half the world's population, hot cooked rice high in resistant starch (RS) is of particular interest, which will have greater impact in the dietary prevention of diabetes and hyperlipidemia. A mutant rice high in RS in hot cooked rice, described as RS111, was comparatively studied with the wild type and common rice. Despite obviously low RS content in the raw milled rice, the RS content in the hot cooked rice of mutant RS111 was significantly higher than that of the wild type and common rice and, correspondingly, in vitro starch hydrolysis by porcine pancreatic alpha-amylase tends to be incomplete with low hydrolysis extent for the cooked mutant rice high in RS. Obvious differences in physicochemical properties, starch granule morphology, pasting properties, thermal properties, and X-ray diffraction pattern were observed among the mutant RS111, wild type, and common indica rice. The high-RS mutant was characterized by significantly higher apparent amylose content and crude lipid content, higher percentage of oval-shaped granules and bigger oval size, reduced paste viscosity, and low onset temperature, peak temperature, final temperature, enthalpy of gelatinization, and crystallinity.

Animals↗
PubMed1999

A minor form of starch branching enzyme in potato (Solanum tuberosum L.) tubers has a major effect on starch structure: cloning and characterisation of multiple forms of SBE A.

Full length cDNAs encoding a second starch branching enzyme (SBE A) isoform have been isolated from potato tubers. The predicted protein has a molecular mass of 101 kDa including a transit peptide of 48 amino acids. Multiple forms of the SBE A gene exist which differ mainly in the length of a polyglutamic acid repeat at the C-terminus of the protein. Expression of the mature protein in Escherichia coli demonstrates that the gene encodes an active SBE. Northern analysis demonstrates that SBE A mRNA is expressed at very low levels in tubers but is the predominant isoform in leaves. This expression pattern was confirmed by Western analysis using isoform specific polyclonal antibodies raised against E. coli expressed SBE A. SBE A protein is found predominantly in the soluble phase of tuber extracts, indicating a stromal location within the plastid. Transgenic potato plants expressing an antisense SBE A RNA were generated in which almost complete reductions in SBE A were observed. SBE activity in the leaves of these plants was severely reduced, but tuber activity was largely unaffected. Even so, the composition and structure of tuber starch from these plants was greatly altered. The proportion of linear chains was not significantly increased but the average chain length of amylopectin was greater, resulting in an increase in apparent amylose content as judged by iodine binding. In addition, the starch had much higher levels of phosphorous.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1993

Influence of particle size and sources of non-starch polysaccharides on postprandial glycaemia, insulinaemia and triacylglycerolaemia in pigs and starch digestion in vitro.

Physico-chemical properties of dietary fibres might be involved in metabolic control, particularly of the postprandial blood glucose response. The aim of the present study was to look at the effects of the content of soluble fibres and of the particle size of solid fibres on in vitro and in vivo starch hydrolysis and on the subsequent glucose absorption as well as the triacylglycerolaemia. Two sources of dietary fibres, one, with soluble fibres (beet pulp), the other with mostly insoluble fibres (wheat bran), were added at the rate of 60 g/kg to a meal simulating human food. The fibre sources were ground in order to obtain two different particle sizes (250 and 500 microns). Beet pulp decreased significantly (P < 0.05) initial in vitro hydrolysis whereas wheat bran increased starch hydrolysis in the first 10 min. Wheat bran and beet pulp, whatever its particle size, lowered the post-prandial triacylglycerol response. No significant effect was found with dietary fibre-supplemented diets on postprandial glycaemic and insulinaemic values. High correlation was found between initial in vitro starch hydrolysis and mean areas under the insulinaemic curves. This in vitro model can be used to predict initial in vivo digestion of carbohydrates from complex foods.

Animals↗
PubMed1995

Dietary intakes of starch and non-starch polysaccharides in a west African village.

Dietary intakes of starch and non-starch polysaccharides (NSP) have been estimated for a rural West African community. These people eat directly from shared bowls of cooked food, and so measurement of any individual's food intake is not possible. Recently developed methodology for estimating food intake under these circumstances and the analysis of samples for dietary polysaccharides are combined to yield estimates of intakes of about 375 g starch and 25 g NSP/d for adult males, with lower intakes for women and children, related to their smaller body weights. These intakes are not direct measurements but are extremely plausible when compared with values obtained for other societies where the complication of the shared food bowl does not impinge upon the measurements.

Adult↗
PubMed2003

STA11, a Chlamydomonas reinhardtii locus required for normal starch granule biogenesis, encodes disproportionating enzyme. Further evidence for a function of alpha-1,4 glucanotransferases during starch granule biosynthesis in green algae.

In Chlamydomonas reinhardtii, the presence of a defective STA11 locus results in significantly reduced granular starch deposition displaying major modifications in shape and structure. This defect simultaneously leads to the accumulation of linear malto-oligosaccharides (MOS). The mutants of STA11 were showed to lack D-enzyme, a plant alpha-1,4 glucanotransferase analogous to the Escherichia coli amylomaltase. We have cloned and characterized both the cDNA and gDNA corresponding to the C. reinhardtii D-enzyme. We now report allele-specific modifications of the D-enzyme gene in the mutants of STA11. These allele-specific modifications cosegregate with the corresponding sta11 mutations, thereby demonstrating that STA11 encodes D-enzyme. MOS production and starch accumulation were investigated during day and night cycles in wild-type and mutant C. reinhardtii cells. We demonstrate that in the algae MOS are produced during starch biosynthesis and degraded during the phases of net polysaccharide catabolism.

Algal Proteins↗
PubMed1995

Expression in Aspergillus niger of the starch-binding domain of glucoamylase. Comparison with the proteolytically produced starch-binding domain.

Glucoamylase 1 from Aspergillus niger is an economically important enzyme in many industrial processes. It hydrolyses granular starch and comprises two distinct domains, a catalytic and a starch-binding domain (SBD). We have transformed A. niger with an expression vector for the secretion of SBD for physico-chemical studies. This was achieved by introducing into the glucoamylase gene a short sequence encoding an endoproteolytic cleavage recognition site such that free SBD was secreted at yields up to 200 mg/l. Free SBD was also obtained by proteolytic digestion of full-length glucoamylase 1. Electrospray mass spectroscopy was used to determine the carbohydrate content of both SBDs. It revealed that the engineered one is more glycosylated: an average of three mannose residues compared to one for the proteolytically derived SBD. Sequencing results also suggest partial glycosylation for the three Thr residues involved (510, 511, 513). It is probable that the engineered SBD represents the true glycosylation level of the SBD in native glucoamylase. Binding of beta-cyclodextrin to the SBD was investigated. It was found that the stoichiometry and the spectral perturbation of Trp residues were identical for both SBDs, but the engineered SBD bound less strongly to the ligand. At high concentrations of beta-cyclodextrin relative to the estimated Kd values, the maximum absorbance changes were identical. The observed difference at low beta-cyclodextrin levels was probably due to the higher level of glycosylation of the expressed SBD. We conclude that the proteolytically derived and expressed starch binding domains both bind 2 mol beta-cyclodextrin/mol protein, but that the pattern of glycosylation and strength of binding are different.

Aspergillus niger↗