We studied the biological variability of blood superoxide dismutase (SOD; EC 1.15.1.1), glutathione peroxidase (GPX; EC 1.11.1.9), and catalase (CAT; EC 1.11.1.6) in a sample of 1836 apparently health subjects, ages 4-97 years. SOD and GPX activities were assayed in plasma (P) and erythrocytes (E) by automated methods, and CAT was measured in erythrocytes by a manual technique. No statistically significant variation of these antioxidant enzyme activities according to gender was demonstrated, except for E-GPX, which was slightly but significantly higher in women than in men (P less than 0.001). Activities appear rather stable in adults less than 65 years old, but decrease for most enzymes in the elderly. There is no evidence that weight, blood pressure, or menopause influences the antioxidant enzymes' activities. In girls ages 10-14 years, E-SOD activity is reduced by 16% (P less than 0.05) after menarche. Variations related to smoking and alcohol consumption are slight and concern only P-SOD and P-GPX, respectively. Conversely, intake of some drugs (e.g., anti-inflammatory agents, antidepressants, and thyroid hormones) modifies activity of some of the three enzymes. E-SOD positively correlates with P-SOD (r = 0.216, P less than 0.001) and E-CAT (r = 0.123, P less than 0.001), and E-GPX with P-GPX (r = 0.218, P less than 0.001). Finally, we propose reference intervals for activities of the three antioxidant enzymes in blood in individuals less than 65 years old.

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The adsorption of the protein fibronectin onto smooth metal oxide surfaces has been monitored in situ and in real time at both low and high ionic strengths using optical waveguide lightmode spectroscopy (OWLS). The kinetics of the evolution of the adsorbed layer thickness, its packing density, and of the total amount deposited were analyzed and used to deduce that at low ionic strength the protein has a compact conformation prone to lateral clustering at the surface, and at high ionic strength it is in a random extended conformation.

Protein monolayers were built up by allowing protein molecules in solution to deposit at the solid/liquid interface. The structural evolution of these layers was followed using optical waveguide lightmode spectroscopy (OWLS). The measured effective refractive indices were interpreted using the uniform thin film model. For a relatively rigid, spheroidal protein (transferrin), the thickness of the layer was already established at very low surface coverages, and the refractive index increased during deposition. For a highly elongated and flexible protein (fibronectin), the converse occurred. The former case is consistent with classical random sequential adsorption. The latter result implies constant conformational rearrangement during deposition producing a compact proteinaceous membrane.