| 1. |
- Abdollahi, Mehdi, 1985, et al.
(författare)
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Reducing water sensitivity of alginate bio-nanocomposite film using cellulose nanoparticles
- 2013
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 54:1, s. 166-173
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Tidskriftsartikel (refereegranskat)abstract
- A bio-based nanocomposite was developed by incorporation of cellulose nanoparticles (CN) obtained from sulfuric acid hydrolysis into alginate biopolymer using solution casting method. The effect of CN loading content (1, 3, 5 and 10 wt%) on microstructural, physical, mechanical and optical properties of the nanocomposites were characterized. The results showed that water solubility and water vapor permeability of the nanocomposites decreased by about 40% and 17%, respectively, upon increasing the CN content to 10%. In addition, the crystalline structure of the CN increased surface hydrophobicity of the alginate film by about 98%. The tensile strength value of the composite films increased from 18.03 to 22.4 MPa with increasing NC content from 0 to 5%; but, it decreased with further increase of the filler content. Nevertheless, film transparency decreased with CN incorporation, especially in high level (10%), which suggested the occurrence of partial agglomeration of the fillers at 10% that coincided with microstructural and mechanical results.
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| 2. |
- Bertoft, Eric, et al.
(författare)
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Building block organisation of clusters in amylopectin from different structural types
- 2012
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 50, s. 1212-1223
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Tidskriftsartikel (refereegranskat)abstract
- Clusters of chains consisting of tightly branched units of building blocks were isolated from 10 amylopectin samples possessing the 4 types of amylopectin with different internal unit chain profiles previously described. It was shown that clusters in types 1 and 2 amylopectins are larger than in types 3 and 4, but the average cluster size did not correspond to the ratio of short to long chains of the amylopectins. The size-distribution of the building blocks, having one or several branches, possessed generally only small differences between samples. However, the length of the interblock segments followed the type of amylopectin structure, so that type 1 amylopectins had shortest and type 4 the longest segments. The chains in the clusters were divided into characteristic groups probably being involved in the interconnection of two, three, and four - or more - building blocks. Long chains were typically found in high amounts in clusters from type 4 amylopectins, however, all cluster samples contained long chains. The results are discussed in terms of the building block structure of amylopectin, in which the blocks together with the interblock segments participate in a branched backbone building up the amorphous lamellae inside growth rings of the starch granules. In such a model, amylopectins with proportionally less long chains (types 1 and 2) possess a more extensively branched backbone compared to those with more long chains (types 3 and 4). (C) 2012 Elsevier B.V. All rights reserved.
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| 3. |
- Bertoft, Eric
(författare)
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Phosphate esters in amylopectin clusters of potato tuber starch
- 2011
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 48, s. 639-649
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Tidskriftsartikel (refereegranskat)abstract
- Starch phosphate is important in starch metabolism and in order to deduce its location and structural effects in clusters and building blocks of amylopectin, these were isolated from a normal potato (WT) and two starches with antisense suppressed glucan water dikinase (asGWD) activity and starch branching enzyme (asSBE) activity possessing suppressed and increased phosphate contents, respectively. Neutral N-chains and phosphorylated P-chains of the amylopectin macromolecules were similar in WT and asGWD, whereas asSBE possessed considerably longer P-chains. Cluster beta-limit dextrins were isolated by alpha-amylase treatment and successive B-amylolysis. Cluster sizes were generally smaller in asSBE. The building block composition of neutral N-clusters were very similar in WT and asGWD, while asSBE was different, containing less blocks with degree of polymerization (DP) > 14. Phosphate content of the P-clusters of WT and asGWD was rather similar, while asSBE contained highly phosphorylated P-clusters with proportionally more P-chains and a low degree of branching. The average chain lengths of the P-clusters were, however, similar in all samples. Our data demonstrate only minor effect on the cluster structure in relation to phosphate deposition suggesting conserved reaction patterns of starch phosphorylation. Models are suggested to account for the principle structural and functional effects of starch phosphate esters. (C) 2011 Elsevier B.V. All rights reserved.
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| 4. |
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| 5. |
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| 6. |
- Bertoft, Eric
(författare)
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The fine structure of cassava starch amylopectin Part 1: Organization of clusters
- 2010
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 47, s. 317-324
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Tidskriftsartikel (refereegranskat)abstract
- The enzyme alpha-amylase from Bacillus subtilis was applied to partly hydrolyze purified cassava amylopectin into groups of clusters, which were called domains. The domains were further size-fractionated by methanol precipitation and then subjected to a second stage of alpha-amylolysis until the rate of hydrolysis was slow in order to release the single clusters. All domain and cluster fractions were hydrolyzed with beta-amylase into beta-limit dextrins. The size distribution and chain composition of the beta-limit dextrins were analyzed by gel-permeation chromatography and high-performance anion-exchange chromatography with pulsed amperometric detection, respectively. The sizes of the clusters in the form of beta-limit dextrins were uniform with an average degree of polymerization of 67-78. The distribution profiles of B-chains were similar in all cluster fractions, which suggested that the internal structure of the cassava amylopectin clusters was homogenous. Long B-chains were involved in the interconnection of clusters in the domain fractions. These were cleaved and a new group of chains of intermediate length was produced by the alpha-amylase together with short chains. In the isolated clusters, however, some chains corresponding to long B-chains still remained, which is not predicted by the traditional cluster model of the amylopectin structure. Instead, the alternative two-directional backbone model could explain the mode of interconnection between the clusters. (C) 2010 Elsevier B.V. All rights reserved.
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| 7. |
- Bertoft, Eric
(författare)
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The fine structure of cassava starch amylopectin. Part 2: Building block structure of clusters
- 2010
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 47, s. 325-335
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to analyse the organization of unit chains inside clusters of cassava amylopectin. beta-Limit dextrins of the clusters and partly fragmented clusters (sub-clusters) were isolated previously [Laohaphatanaleart et al., Int. J. Biol. Macromol. (2010) doi:10.1016/j.ijbiomac.2010.01.0049] and were now hydrolysed extensively with the alpha-amylase (liquefying type) of Bacillus subtilis into small, branched building blocks. The blocks were size-fractionated and characterized structurally. The smallest blocks predominated in the clusters. They were single branched and possessed a degree of polymerization (DP) of 5-9. Blocks with DP 10-15 were double branched and constituted the second largest group. The clusters of cassava amylopectin, which were of rather uniform size, possessed typically 7-9 building blocks, and all clusters contained similar size-distributions of the blocks. The inter-block chain length was 7-8 residues. The possible mode of attack by the enzyme between the building blocks is discussed. A model of the building block organization in the clusters is presented, in which the structural roles of different subgroups of clustered chains are suggested. A three-dimensional model suggests a possible organization of the building blocks inside the amorphous lamellae in the granular starch. (C) 2010 Elsevier B.V. All rights reserved.
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| 8. |
- Carlstedt, Jonas, et al.
(författare)
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Release of DNA from surfactant complexes induced by 2-hydroxypropyl-beta-cyclodextrin.
- 2010
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 1879-0003 .- 0141-8130. ; 46:2, s. 153-158
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Tidskriftsartikel (refereegranskat)abstract
- Decompaction of DNA-CTA self-assembled complexes by 2-hydroxypropyl-beta-cyclodextrin (2-HP-beta-CD) was studied and the results were compared with beta-CD. Different degrees of 2-HP substitution (0.6, 0.8 and 1.0, respectively) were used and the decompaction was successful with all degrees of substitution. Fluorescence microscopy, steady state fluorescence spectroscopy, density and sound velocity measurements, thermal melting and circular dichroism were used. Compared to previous work using alpha- and beta-CD, the fluorescence spectroscopy results showed that the 2-HP-substituted CDs more efficiently released DNA into solution. Furthermore, dissociation of macroscopically phase separated DNA-CTA complexes was achieved upon addition of 2-HP-beta-CD and the results gave strong indications on the non-equilibrium nature of the system. The globule-to-coil transition was not found to proceed through a coexistence region, which seems to be a general phenomenon in DNA decompaction using CDs.
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| 9. |
- Cho, Sung-Woo, et al.
(författare)
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Injection-molded nanocomposites and materials based on wheat gluten
- 2011
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 48:1, s. 146-152
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Tidskriftsartikel (refereegranskat)abstract
- This is, to our knowledge, the first study of the injection molding of materials where wheat gluten (WG) is the main component. In addition to a plasticizer (glycerol), 5 wt.% natural montmorillonite clay was added. X-ray indicated intercalated clay and transmission electron microscopy indicated locally good clay platelet dispersion. Prior to feeding into the injection molder, the material was first compression molded into plates and pelletized. The filling of the circular mold via the central gate was characterized by a divergent flow yielding, in general, a stronger and stiffer material in the circumferential direction. It was observed that 20–30 wt.% glycerol yielded the best combination of processability and mechanical properties. The clay yielded improved processability, plate homogeneity and tensile stiffness. IR spectroscopy and protein solubility indicated that the injection molding process yielded a highly aggregated structure. The overall conclusion was that injection molding is a very promising method for producing WG objects.
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| 10. |
- Fernandez, Celine, et al.
(författare)
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Size, structure and scaling relationships in glycogen from various sources investigated with asymmetrical flow field-flow fractionation and 1H NMR
- 2011
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 1879-0003 .- 0141-8130. ; 49:4, s. 458-465
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we investigate the size, structure and scaling relationships in glycogen isolated from five different animal sources. For this purpose a versatile fractionation technique, asymmetrical flow field-flow fractionation (AsFlFFF), coupled to multi-angle light scattering, is utilized. For determination of the average degree of branching 1H NMR is utilized. The results give a detailed insight into the physico-chemical properties of glycogen over the whole size distribution. The results show that glycogen is a hyper branched macromolecule with wide size distributions, and in some samples two major populations are clearly observed which most likely correspond to β- and α-particles of glycogen. The results also illustrates that glycogen is a polysaccharide showing rather diverse conformational properties, over the size distribution, depending on its origin and the extraction procedure. The ratio between root-mean-square radius and hydrodynamic radius varies depending of both sample origin the molar mass of the macromolecules, reflecting differences in conformation and scaling within the size distribution. Thus, a priori assumptions regarding the rrms/rh are difficult to make and rrms/rh based on average properties give an incomplete description of the properties. Furthermore, the results display the strength of the apparent density (as obtained from AsFlFFF-MALS-RI) as a characterization parameter for scaling in disperse macromolecules. © 2011 Elsevier B.V.
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