Preparation of fat replacer utilizing gluten and barley ß-glucan and the interaction between them.

BACKGROUND: Fat replacers prepared from polysaccharides and proteins possess functional properties of both polysaccharides and proteins. In this study, an aqueous system of barley ß-glucan (BBG) and gluten was prepared. The interactions between BBG and gluten (with/without extrusion modification) were studied. Triple analysis methods, including differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and low-field nuclear magnetic resonance (LF-NMR), were utilized to analyze the freezing-thawing and thermal evaporation process, as well as the distribution state of water. Meanwhile, fluorescence microscopic analysis, dynamic rheological analysis and electrophoresis analysis were used to study the structure and rheological properties of the system. RESULTS: The results showed that BBG significantly increased the water-holding capacity of gluten, regardless of extrusion treatment, with the water absorption reaching about 4.8 to 6.4 times of its weight, which was 1 to 2.5 times higher than that without BBG. The triple analysis results suggested that BBG increased the binding capacity of the system to weakly bound water, hindered the aggregation of gluten and reduced the thermal decomposition temperature of the BBG and gluten composite system. After the gluten was extruded and homogenized with the BBG solution, the appearance of the composite system was more uniform and delicate. CONCLUSIONS: In conclusion, BBG increased the water-holding capacity of the BBG and gluten composite system. With these changes, the composite system presented great potential for the preparation of polysaccharide-gluten fat replacer. © 2023 Society of Chemical Industry.

Depletion of FKBP does not affect the interaction between isolated ryanodine receptors.

The ryanodine receptors/calcium release channels (RyRs) usually form two dimensional regular lattices in the endoplasmic/sarcoplasmic reticulum membranes. The native RyR is associated with many auxiliary proteins, including FKBP. It has been indicated that FKBP may play a role in the intermolecular interaction and coupled gating of neighboring RyRs. However, a more recent study shows that FKBP12 is not involved in the physical linkage between neighboring RyR1s. In the present work, the effect of FKBP12 on the interaction between RyR1s isolated from rabbit skeletal muscle was investigated in an aqueous medium with photon correlation spectroscopy. We found that the depletion of FKBP12 did not affect the oligomerization of RyR1s in the medium containing different [KCl] or under different channel functional states. No evidence is obtained for the involvement of FKBP12 in the intermolecular interaction between RyR1s.

Modulation of the oligomerization of isolated ryanodine receptors by their functional states.

The calcium release channels/ryanodine receptors (RyRs) usually form two-dimensional regular lattices in the endoplasmic/sarcoplasmic reticulum membranes. However, the function and modulation of the interaction between neighboring RyRs are still unknown. Here, with an in vitro aqueous system, we demonstrate that the interaction between RyRs isolated from skeletal muscle (RyR1s) is modulated by their functional states by using photon correlation spectroscopy and [(3)H]ryanodine binding assay. High level of oligomerization is observed for resting closed RyR1s with nanomolar Ca(2+) in solution. Activation of RyR1s by micromolar Ca(2+) or/and millimolar AMP leads to the de-oligomerization of RyR1s. The oligomerization of RyR1s remains at high level when RyR1s are stabilized at closed state by Mg(2+). The modulation of RyR1-RyR1 interaction by the functional state is also observed under near-physiological conditions, suggesting that the interaction between arrayed RyR1s would be dynamically modulated during excitation-contraction coupling. These findings provide exciting new information to understand the function and operating mechanism of RyR arrays.

Effect of Zn2+ ions on ryanodine binding to sarcoplasmic reticulum of striated muscles in the presence of pyrithione.

AIM: To explore whether the differential effects of Zn2+ on ryanodine binding to the sarcoplasmic reticulum (SR) of skeletal and cardiac muscles resulted from different permeability of the SR to Zn2+. METHODS: [3H]ryanodine binding assays were performed to examine the effect of Zn2+ on ryanodine binding to the SR in the presence of pyrithione sodium (PyNa), a specific Zn2+ ionophore. RESULTS: As a control, PyNa up to 50 micromol/L did not induce any effect on ryanodine binding to the SR of cardiac muscle. But PyNa 1-100 micromol/L increased ryanodine binding in skeletal muscle with maximum binding (222.2+/-20.9 % of the control) and inhibited ryanodine binding to 50 % of the control at about 500 micromol/L. In the presence of PyNa 10 and 50 micromol/L the dose-dependence of the effect of Zn2+ in cardiac muscle was still monophasic and not changed by PyNa, while the biphasic effect of Zn2+ in skeletal muscle became monophasic. CONCLUSION: Different permeability of the SR to Zn2+ may account for the differential effects of Zn2+ on ryanodine binding in skeletal and cardiac muscles. PyNa is not a strictly specific Zn2+ ionophore.

Modulation of the interactions of isolated ryanodine receptors of rabbit skeletal muscle by Na+ and K+.

Ryanodine receptors (RyRs) of skeletal muscle, as calcium release channels, have been found to form semicrystalline arrays in the membrane of sarcoplasmic reticulum. Recently, both experimental observations and theoretical simulations suggested cooperative coupling within interlocking RyRs. To better understand the interactions between RyRs and their modulation, the aggregation and dissociation of isolated RyRs in aqueous medium containing various Na(+) and K(+) concentrations were investigated using photon correlation spectroscopy (PCS) and atomic force microscopy (AFM). RyRs aggregated readily at low salt concentrations. However, a different behavior was observed in the presence of Na(+) or K(+). Detectable aggregates were formed in 5 microg/mL RyR sample when the concentration of Na(+) and K(+) was reduced from 1 M to below 0.28 and 0.23 M, respectively. The dissociation of RyR aggregates was also examined when raising the salt concentration. While aggregates formed in 0.15 M NaCl medium could reverse almost completely, those formed in 0.15 M KCl medium only dissolved partly. When keeping the total salt concentration at 0.15 M, the aggregation and dissociation of RyRs were seen to evidently depend on the relative concentration of Na(+) and K(+). The interaction between RyRs was strengthened with increasing Na(+)/K(+) ratios in the mixed medium. Accompanying this, a decrease of [(3)H]ryanodine binding occurred. The results obtained with PCS and AFM provide further evidence for the interaction between RyRs and suggest the importance of Na(+), K(+), and their relative composition in modulating the interaction and cooperation between RyRs in vivo.

Effect of zinc ions on caffeine-induced contracture in vascular smooth muscle and skeletal muscle of rat.

The effect of zinc ions on caffeine-induced contracture in vascular smooth muscle and skeletal muscle of rat was studied. In aortic strips, caffeine contracture was depressed by Zn2+ in a dose-dependent manner. Moreover, the extent of the depression of caffeine contracture in the Zn2+ loaded smooth muscle increased with repetitive caffeine exposures. For instance, in the preparations perfused with a medium containing 100 microM [Zn2+] for 15 or 30 min, the first caffeine contractures were similarly depressed to about 60% of the control. However, the subsequent caffeine exposure at 15 min interval could not evoke any contracture. In this study this feature is referred to as activation dependence of the Zn2+ effect. In small bundles of soleus muscle 2ñ100 microM [Zn2+] similarly caused a depression of caffeine contracture, and the activation dependence also was evident. However, an evident potentiation of caffeine contracture was seen in the preparations loaded with lower [Zn2+] such as 0.5 microM, indicating that the effect of Zn2+ on caffeine contracture of skeletal muscle was somewhat different from that seen in smooth muscle. By observing how the depression effect depends on the intervals between caffeine exposures as well as on caffeine concentrations, it is indicated that the activation dependence of the Zn2+ effect, at least in skeletal muscle, may not be explained by depletion of intracellular Ca2+ stores alone. The possible mechanism for that caffeine contracture of smooth muscle and skeletal muscle was differentially affected by Zn2+ ions is discussed.