Development of (5-(4,6-dichlorotriazinyl) aminofluorescein) DTAF-labelled polysaccharides for characterization of microstructure and phase distribution of composite hydrogel visualization of hydrogels using CLSM

Tyramine-assisted fluorescent labeling of polysaccharides: Characterization, and interfacial properties

Fluorescence labeling has been widely used in various fields, including fluorescent sensors, biochemistry, medical and chemical research. This study proposed an efficient strategy for the detection and microanalysis of polysaccharides. Soy hull polysaccharide (SHP) was successfully labeled with fluorescein isothiocyanate (FITC) via an amination reaction using tyramine as a linker. The labeled polysaccharide (FTSHP) was characterized by fluorescence, UV-visible, flourier transform infrared (FT-IR), 1H NMR, differential scanning calorimetry (DSC) and interfacial tension. The results indicated that the labeling efficiency of FTSHP with different concentration of FITC (0.20-0.35 wt%) was 1.51 %, 1.58 %, 1.63 %, and 1.67 %, respectively, with fluorescence intensity increasing as FITC concentration increased. Moreover, the interfacial adsorption capacity and thermal stability of FTSHP were significantly improved compared to SHP. This labeling method offers a promising approach for detection and analysis of polysaccharides, providing new insights into the study of other natural polysaccharides.

Ficus awkeotsang Makino pectin in acidic environments: Insights into pectin structure, gelation behavior, and gel properties

This study demonstrated the gelation capacity, gelation behavior, and mechanism of Ficus awkeotsang Makino pectin (JFSP) in acidic media (pH 3.4-4.5). JFSP exhibited an extraordinary ability to spontaneously form a gel at a low polymer concentration (0.3 %, w/v) within the pH range of 3.75-4.05 at room temperature, without the need to introduce exogenous metal ions or co-solutes. Analysis of zeta potential and carboxyl dissociation extent revealed the protonation of free carboxyl groups within JFSP under acidic conditions. Atomic force microscopy and small angle X-ray scattering elucidated the aggregation morphology and folding conformation of JFSP. At pH 3.8, the correlation length (ξ) of JFSP chains decreased to around 1.67 nm. Rheological experiments confirmed the formation of a stronger gel network at pH 3.8 and 4.0, with good thermal and freeze-thaw stability. Isothermal Titration Calorimetry (ITC), temperature sweeps, and gelation force analyses emphasized the pivotal role of hydrogen bonds in JFSP gels at pH 3.8 and 4.0. Further reducing the pH to 3.4-3.6 disrupted the dynamic equilibrium of gel-driving forces, leading to the formation of a flocculated gel network. These findings deepen our understanding of JFSP behavior in low-acid conditions, which may be useful for further food formulations at these conditions.

Deciphering the liquid-liquid phase separation induced modulation in the structure, dynamics, and enzymatic activity of an ordered protein β-lactoglobulin

Owing to the significant role in the subcellular organization of biomolecules, physiology, and the realm of biomimetic materials, studies related to biomolecular condensates formed through liquid-liquid phase separation (LLPS) have emerged as a growing area of research. Despite valuable contributions of prior research, there is untapped potential in exploring the influence of phase separation on the conformational dynamics and enzymatic activities of native proteins. Herein, we investigate the LLPS of β-lactoglobulin (β-LG), a non-intrinsically disordered protein, under crowded conditions. In-depth characterization through spectroscopic and microscopic techniques revealed the formation of dynamic liquid-like droplets, distinct from protein aggregates, driven by hydrophobic interactions. Our analyses revealed that phase separation can alter structural flexibility and photophysical properties. Importantly, the phase-separated β-LG exhibited efficient enzymatic activity as an esterase; a characteristic seemingly exclusive to β-LG droplets. The droplets acted as robust catalytic crucibles, providing an ideal environment for efficient ester hydrolysis. Further investigation into the catalytic mechanism suggested the involvement of specific amino acid residues, rather than general acid or base catalysis. Also, the alteration in conformational distribution caused by phase separation unveils the latent functionality. Our study delineates the understanding of protein phase separation and insights into the diverse catalytic strategies employed by proteins. It opens exciting possibilities for designing functional artificial compartments based on phase-separated biomolecules.

Unravelling the functionality of anionic and non-ionic plant seed gums on milk protein cryogels conveying Lacticaseibacillus rhamnosus GG

Cryogels offer a promising macroporous platform that can be employed as either a functional ingredient in food composites or a colloidal template for incorporating bioactives, including probiotic living cells. The aim of the present work is to explore the functionality of two plant seed polysaccharides, flaxseed gum (FG) and alfalfa galactomannan (AAG), in individual and combined (1:1 ratio) milk protein-based cryogels, namely sodium caseinate (NaCas) and whey protein isolate (WPI). These cryogels were created by freeze-drying hydrogels formed via L.rhamnosus GG - a human gut-relevant probiotic strain - fermentation. Our findings showed that including gum in the composition limited volume contraction during lyophilisation, reduced macropore size and thickened cryogel skeleton vessels. Furthermore, gum-containing cryogels displayed improved thermal stability and slower water disintegration rates. The AAG-stabilised cryogels specifically showed a notable reduction in monolayer water content compared to FG. From a mechanistic viewpoint, AAG influenced the physicochemical and microstructural properties of the cryogels, most probably via its self-association during cryogenic processing, promoting the development of intertwined protein-gum networks. FG, on the other hand, enhanced these properties through electrostatic complexation with proteins. Cryogels made from protein-polysaccharide blends exhibited promising techno-functional properties for enhancing and diversifying food product innovation.

Study on pharmacokinetics and tissue distribution of Polygonatum sibiricum polysaccharide in rats by fluorescence labeling

To study the pharmacokinetics and tissue distribution characteristics of Polygonatum sibiricum (P. sibiricum) polysaccharide administered orally and intravenously in rats, the latest quantitative analysis method was established where P. sibiricum polysaccharide was labeled with fluorescein isothiocyanate (FITC) in plasma and tissues. Quantitative analysis method of P. sibiricum polysaccharide in rat plasma and tissues was established by fluorescence spectrophotometry with FITC as a highly sensitive fluorescent molecular probe. The results showed that P. sibiricum polysaccharide was successfully labeled with FITC, and the degree of substitution was 0.55 %. Pharmacokinetic characteristics showed that oral administration (ig) and intravenous injection (iv) were consistent with the characteristics of two-compartment model. PRP-TYR-FITC administered orally was poorly absorbed in rats with low bioavailability. After a single ig and iv administration in rats for 8 h, P. sibiricum polysaccharide can be distributed in most tissues. The analysis results showed that P. sibiricum polysaccharide was distributed mostly in lung, kidney and liver for both routes of administration. When taking orally, the distribution pattern was: lung > liver > kidney > small intestine > stomach > heart > spleen > brain. When taking intravenously, the distribution pattern was: liver > lung > kidney > small intestine > heart > stomach > spleen > brain. Fluorescence labeling of P. sibiricum polysaccharide by FITC was successfully realized. This method was proved to be suitable for the study of pharmacokinetics and tissue distribution of P. sibiricum polysaccharide in rats. The above research lays foundation for further elucidating the clinical pharmacological mechanism of polysaccharide in P. sibiricum.