Conformational change and aggregation of κ-carrageenan studied by flow field-flow fractionation and multiangle light scattering

Abstract

The relatively novel combination of flow field‐flow fractionation (FFF) and multiangle light scattering (MALS) was employed to study a nondegraded κ‐carrageenan in different 0.1M salt solutions. The applicability of the technique was tested, and the effects of salt type and salt composition on the molar mass and radius of gyration were studied. A conformational ordering was induced at room temperature by switching the solvent from 0.1M NaCl (coil form) to 0.1M NaI (helix form). An approximate doubling of the average molar mass and an increase in radius of gyration was then observed, in agreement with results obtained previously using size exclusion chromatography–MALS. This increase in size was attributed to conformational ordering and to the formation of double helices. Severe aggregation was observed above 40% CsI in the 0.1M mixed salt solution of CsI and NaI. This was ascribed to the association of helices into large aggregates. For these large associates, having molar masses of several millions, a reversal of the elution order in flow FFF was detected. © 1998 John Wiley & Sons, Inc. Biopoly 45: 85–96 1998

Characterization of α-carrageenan solution behavior by field-flow fractionation and multiangle light scattering

“…The separation is further optimized with the application of a constant or variable secondary crossflow to accomplish desired resolution. Subsequent to separation, molar mass and R g is determined from the light scattering data, R h is determined from the diffusion coefficient D of the retained macromolecule, and the retention parameter used in this study are in the strong retention range of 1/l ¼ 8.3-32.7 (Table 1) as outlined by Wittgren et al (1998).…”

“…Baker, Phillipsburg, NJ, USA) and NaI (Sigma-Aldrich, St. Louis, MO, USA) were dissolved in deionized water (MilliQ system) at 0.1 M. Albumin monomer bovine (Sigma-Aldrich, St. Louis, MO, USA) concentration was 1 mg/mL for channel thickness determination. Pullulan P-100 (Mw 100 kDa, BioChemika, Buchs SG, Switzerland) of $1.0 mg/mL was employed for normalization of the MALS detector as well as a system suitability check for the AFFF instrumentation (Benincasa & Fratte, 2004;Wittgren et al, 1998;Wittgren & Wahlund, 1997). A high degree of accuracy and reproducibility for Pullulan P-100 was obtained (n ¼ 9): average molecular weight (Mw avg ) ¼ 121.3 kDa (rsd 0.6%), polydispersity (Mw/Mn) ¼ 1.02 (rsd 0.3%), R g ¼ 11.5 nm (rsd ¼ 6.5%) and R h ¼ 8.7 nm (rsd 6.4%).…”

“…Techniques used include size exclusion chromatography with multiangle light scattering detection (SEC-MALS; Marcelo et al, 2005), single angle X-ray scattering (SAXS; Tha`nh et al, 2002;Yuguchi et al, 2002Yuguchi et al, , 2003, NMR (Falshaw et al, 1996;Grasdalen & Smidsro¨d, 1981;Nerdal et al, 1993), and asymmetric field-flow fractionation (AFFF; Viebke & Williams, 2000;Wittgren, Borgstro¨m, Piculell, & Wahlund, 1998).…”

“…The mean coil density is then calculated as the molecular density r which is the ratio of R g /R h . Theoretical values for molecular densities which correspond to various polymer shapes are: r ¼ 0.775 for compact sphere, r ¼ 1.862 for flexible polymer in a good solvent, and r ¼ 2.659 for a rigid rod with an axial ratio of 100 (Wittgren et al, 1998).…”

Combining asymmetrical flow field-flow fractionation with on- and off-line fluorescence detection to examine biodegradation of riverine dissolved and particulate organic matter

“…FlFFF takes advantage of the diffusion characteristics of particles or 103 macromolecules in which particles with faster diffusion (or smaller Stokes' diameter) are 104 distributed against the channel wall with a center of gravity (cg) higher than that of slower 105 diffusion (larger particles); therefore, smaller particles elute earlier than larger particles in a 106 flow stream with parabolic flow velocity profiles. Among variants of FlFFF, asymmetrical 107 flow field-flow fractionation (AF4) has been widely utilized for size separation and 108 characterization of proteins, cells, viruses, and water-soluble polymers [31,32,33,34]. In 109 particular, FlFFF was employed to study the molecular weight distribution of natural organic 110 matter [35,36], the relationship between elemental composition and size of natural colloids in 111 the environment [37], and variations in fluorescence of chromophoric DOMs using off-line 112 EEM fluorescence spectroscopy [38].…”