The effects of ionic strength on fractal structures in heat-induced gels prepared from globular proteins were investigated in the framework of a fractal aggregation of colloidal particles. All gels formed at 90 °C exhibited power law relationships between the storage shear modulus (G′) and protein concentration. At 25 mM NaCl, the fractal dimension, d (∼2.2), calculated based on the value of the power law exponent agreed with those for reaction-limited cluster-cluster aggregation. Further addition of NaCl (50, 80, 500, 1000 mM) decreased the values of d (∼1.8), which agreed with d for diffusion-limited cluster-cluster aggregation. These results suggest that the predominant effect of an increase in ionic strength on globular protein gelation is ascribed to shielding charges on the surface of the proteins, thereby increasing the reaction probability of protein aggregation. The effective structure-determining rheological properties of heat-induced protein gels are characterized by fractal dimensions deduced from the rheological model, which also suggests that the size of primary flocs building fractal structures is one of the important factors that determines the linear viscoelastic properties of the gels.

Abstract-Human urotensin II (U-II), the most potent vasoconstrictor peptide identified to date, and its receptor (UT) are involved in hypertension and atherosclerosis. Acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT-1) converts intracellular free cholesterol into cholesterol ester (CE) for storage in lipid droplets and plays an important role in the formation of macrophage-derived foam cells in atherosclerotic lesions. We examined the effects of U-II on ACAT-1 expression and CE accumulation in human monocyte-derived macrophages. U-II increased ACAT activity in a concentration-dependent manner after 7 days in monocyte primary culture. Immunoblotting analysis showed that U-II at 25 nmol/L increased ACAT-1 protein expression level by 2.5-fold, which was completely abolished by anti-U-II antibody, selective UT receptor antagonists (urantide and 4-aminoquinoline), a G-protein inactivator (GDP-␤-S), a c-Src protein tyrosine kinase inhibitor (PP2), a protein kinase C (PKC) inhibitor (rottlerin), a mitogen-activated protein kinase kinase (MEK) inhibitor (PD98059), or a Rho kinase (ROCK) inhibitor (Y27632). Northern blotting analysis indicated that among the 4 ACAT-1 mRNA transcripts (2.8-, 3.6-, 4.3-, and 7.0-kb), the 2.8-and 3.6-kb transcript levels were selectively upregulated by Ϸ1

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To better understand the relation between recrystallization rate and water mobility in freezeconcentrated matrix, isothermal ice recrystallization rates in several sugar aqueous solutions and selfdiffusion coefficients of water component in corresponding freeze-concentrated matrix were measured. The sugars used were fructose, glucose, maltose, and sucrose. The sugar concentrations and temperature were varied so that ice contents for all samples were almost equal. Neither recrystallization rates nor diffusion coefficients depended uniformly on temperature. The recrystallization rates increased with increasing the diffusion coefficients, and a direct relationship was found between recrystallization rate and diffusion coefficient. This indicated that self-diffusion coefficient of water component in freeze-concentrated matrix is a useful parameter for predicting and controlling recrystallization rate in sugar solutions relevant to frozen desserts.