Biopolymers reproducibility

Fig. 17 (a) Elastin-based stimulus-responsive gold nanoparticles. Reproduced from [131] by permission of The Royal Society of Chemistry (b) Functionalization of a glass surface with ELP. In the first step, the glass surface is aminosilylated with N-2-(aminoethyl)-3-aminopropyl-trimethoxysilane, then modified with glutaraldehyde. Subsequently, the stimulus-responsive biopolymer is covalently immobilized using reductive amination. Reproduced from [132] by permission of The Royal Society of Chemistry... 

High performance capillary electrophoresis in its current form is a new technique. Its feasibility has been proven by the analysis and separation of small ions, drugs, chiral molecules, polymers, and biopolymers.93 We are learning more every day about the small tricks of the trade of the technique, and the efficiency and reproducibility of the methods are improving. 

Capillary electrophoresis offers several useful methods for (i) fast, highly efficient separations of ionic species (ii) fast separations of macromolecules (biopolymers) and (iii) development of small volume separations-based sensors. The very low-solvent flow (l-10nL min-1) CE technique, which is capable of providing exceptional separation efficiencies, places great demands on injection, detection and the other processes involved. The total volume of the capillaries typically used in CE is a few microlitres. CE instrumentation must deliver nL volumes reproducibly every time. The peak width of an analyte obtained from an electropherogram depends not only on the bandwidth of the analyte in the capillary but also on the migration rate of the analyte. 

FIG. 35 Percentage relative humidities of common foods at room temperature and typical steady-state moisture contents plotted as a universal sorption isotherm with portions of three glass curves (relatively positioned) for sorbitol, for a nonnetworked biopolymer, and for a permanent network [reproduced with permission from Slade and Levine (2003)]. 

FIGURE 5.9 DSC profiles of potato starch at different water contents (volume fraction of water indicated next to each profile). Heating rate=10 °C/min. Donovan (1979), Phase transitions of starch-water system. Biopolymers, 18, 263-275. Copyright Wiley-VCH Verlag GmbH Co. KGaA. Reproduced with permission. 

Figure 3.2 Evolution of the microstructure of phase-separated biopolymer emulsion system containing pectin and 0.5 vt% heat-denatured (HD) whey protein isolate (WPI) stabilized oil droplets, (a) Composition 1U 3L (one-to-three mass ratio of upper and lower phases). The large circles are the water droplets (W), while the small circles are the oil droplets (O). This system forms a W2/W1-O/W1 emulsion, where O is oil, Wi is HD-WPI-rich and W2 is pectin-rich, (b) Composition 2U 2L. This system forms an 0/Wi/W2 emulsion, where O is oil, Wi is HD-WPI-rich and W2 is pectin-rich, (c) Composition 3U 1L. This system forms an 0/W]/W2 emulsion, where O is oil, Wi is HD-WPI-rich and W2 is pectin-rich. Reproduced from Kim et al. (2006) with permission.

Figure 3.3 Illustration of the calculation of the phase diagram of a mixed biopolymer solution from the experimentally determined osmotic second virial coefficients. The phase diagram of the ternary system glycinin + pectinate + water (pH = 8.0, 0.3 mol/dm3 NaCl, 0.01 mol/dm3 mercaptoethanol, 25 °C) —, experimental binodal curve —, calculated spinodal curve O, experimental critical point A, calculated critical point O—O, binodal tielines AD, rectilinear diameter,, the threshold of phase separation (defined as the point on the binodal curve corresponding to minimal total concentration of biopolymer components). Reproduced from Semenova et al. (1990) with permission.

Figure 8.14 CLSM images showing the initial development of the microstructure of a phase-separated mixed biopolymer system (25.5 wt% sugar, 31.4 wt% glucose syrup, 7 wt% gelatin, and 4 wt% oxidized starch pH = 5.2, low ionic strength) containing 0.7 wt% polystyrene latex particles (d32 = 0.3 pm). The sample was quenched from 90 to 1 °C, held at 1 °C for 10 min, heated to 40 °C at 6 °C min-1, and observed at 40 °C for various times (a) 2 min, (b) 4 min, (c) 8 min, and (d) 16 min. White regions are rich in colloidal particles. Reproduced from Firoozmand et ai (2009) with permission.

The performance of capillary electrophoresis, for the separation of biopolymers, is comparable to or better than that of HPLC. The basis for separation relies on the choice of an appropriate buffer to be adapted to the analysis. Although reproducibility is more difficult to control, mass sensitivity is relatively high a few thousand molecules can be detected. Sample quantity is very small and solvent and reagent consumption during an analysis is negligible (Fig. 8.10). 

Figure 5.1. Notation for torsion angles of biopolymer chains. Torsion angles ( and ift) that affect the main chain conformations of biopolymers are shown for polysaccharide (a), polypeptide (b), and polynucleotide (c) chains according to the IUBMB notation. The two torsion angles, and ij>, specified around the phosphodiesteric bonds of nucleic acids correspond to a and respectively. Reproduced from IUBMB at http //www.chem.gmw. ac.uk/iubmb.

To obtain other pHs, a listing of common buffers used in my laboratory is given in Table 1. Phosphate is an excellent buffer over a wide range of pHs. It binds to the capillary wall and generally produces reproducible electroosmotic flow. Should phosphate bind to the solute, a wall effect is produced that lowers efficiency [12], This tends to occur with some biopolymers. If the effect is noted, select an alternative buffer. 

Figure 2. Schematic diagram of a voltage-gated channel. Reproduced with permission from S. Futaki, Biopolymers 1998, p. 76, Fig. 1.

DNA is a stiff polyelectrolyte. The collision of the migrating DNA and the separation media have different quantitative and even qualitative effects on DNAs of different size. Different conformations of the analytes exist during the separation, depending on the pore size of the gel and the length of the biopolymer. These conformations are ultimately responsible for the different mobilities and the apparent irregularities. The different conformations reproduced in Fig. 3 were observed by fluorescence microscopy [17,18]. 

Figure 7.43. SIMS analysis of lignin, the second most abundant biopolymer in nature, following cellulose. Shown is the phenylpropane subunits and a structural model of softwood Ugnin (top). The secondary-ion mass spectra of pine (softwood) and beech (hardwood) milled wood Ugnin (MWL, a solvent-extracted form of Ugnin from beech wood) are also shown (bottom). Reproduced with permission from Saito, K. Kato, T. Tsuji, Y. Fukushima, TL. Biomacromolecules 2005, 6,678. Copyright 2005 American Chemical Society.

Size-exclusion chromatography has been recently applied, with success, to the analysis of biopolymers derived from biomass, as it is used for the determination of molecular mass distributions of polymeric compounds in general, because of its short analysis time, high reproducibility, and accuracy. This application of SEC has permitted the separation and further detection of polymeric and monomeric residues of biopolymers, as well as the estimation of the degree of polymerization and eventual uses of namral products as additives, not only in... 

The application of a wide variety of chromatographic techniques to the analysis of additives in biopolymers is a current tendency in many research laboratories around the world. The increasing interest in the use of biopolymers in many technological applications will raise the research in this field in the future. Therefore, the potential of chromatography for separation, identification, and quantification will be very important for the development of reliable and reproducible analytical methods. 

In certain cases, modifieation of the stationary phase, as for example the removal of residual silanols by endoapplng dth trimethylsilane (TMS), can be beneficial in achieving a more reproducible separation. In other situations, however, a separation may acti y be enhanced by a more heterogeneous support This postulate b mes more foroefol for larger molecules, particularly biopolymers, where the chemical environment of the solute difiers sigr cantly on the intramolecular scale. 

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