Binding of gold to bovine serum albumin using flameless atomic absorption

Microfluidic devices integrating microcavity surface-plasmon-resonance sensors: glucose oxidase binding-activity detection

We have developed miniature (approximately 1 microm diameter) microcavity surface-plasmon-resonance sensors (MSPRS), integrated them with microfluidics, and tested their sensitivity to refractive-index changes. We tested their biosensing capability by distinguishing the interaction of glucose oxidase (M(r) 160 kDa) with its natural substrate (beta-D-glucose, M(r) 180 Da) from its interactions with nonspecific substrates (L-glucose, D-mannose, and 2-deoxy-D-glucose). We ran the identical protocol we had used with the MSPRS on a Biacore 3000 instrument using their bare gold chip. Only the MSPRS was able to detect beta-D-glucose binding to glucose oxidase. Each MSPRS can detect the binding to its surface of fewer than 35,000 glucose oxidase molecules (representing 9.6 fg or 60 zmol of protein), about 10(6) times fewer than classical surface-plasmon-resonance biosensors.

Stable superoxide dismutase (SOD)-mimetic ternary human serum albumin-Cu(II)(3,5-diisopropylsalicylate)2/Cu(II)2(3,5-diisopropylsalicylate)4 complexes in tissue distribution of the binary complex

Copper(II)2(3,5-diisopropylsalicylate)4 [Cu(II)2(3,5-DIPS)4] has been found to have antiinflammatory, antiulcer, anticancer, anticonvulsant, antimutagenic, antidiabetic, analgesic, and radiation protection and recovery activities. It has also been found to reduce ischemia-reperfusion injury. Because of these activities it was of interest to understand how this compound is transported in the body to affected tissues. Evidence supporting the suggested formation of ternary human serum albumin (HSA)-Cu(II)(3,5-DIPS)2 or Cu(II)2(3,5-DIPS)4 complexes was obtained using ultraviolet spectrophotometry, dialysis, and atomic absorption spectrophotometry or atomic emission spectroscopy. Superoxide dismutase (SOD)-mimetic activity was also determined using the xanthine/xanthine oxidase/cytochrome c system. Ultraviolet spectra of aqueous solution mixtures of Cu(II)2(3,5-DIPS)4 in equilibrium with 2Cu(II)(3,5-DIPS)2 and HSA as well as aqueous solutions of solid Cu(II)2(3,5-DIPS)4 obtained by stirring the solid with an aqueous solution of HSA showed no obvious change in absorbance to indicate ternary complex formation. However, comparison of ultraviolet spectra taken before and after dialysis supports the suggested bonding of Cu(II)(3,5-DIPS)2 or Cu(II)2(3,5-DIPS)4 to HSA. Comparison of copper concentrations before and after dialysis also supports the suggested bonding of Cu(II)(3,5-DIPS)2 or Cu(II)2(3,5-DIPS)4 to HSA. Based upon these data it is plausible that Cu(II)(3,5-DIPS)2 or Cu(II)2(3,5-DIPS)4 form stable ternary complexes with HSA. These stable ternary complexes were also found to have SOD-mimetic activity.

Effect of protein concentration on the binding of gold(I) to human serum albumin

The binding of aurothiosulphate, gold(I), by human serum albumin has been studied by equilibrium dialysis at four different albumin concentrations, 37 degrees, pH 7.2-7.4 and ionic strength 0.15 M. The results show that the interaction of aurothiosulphate with albumin depends on albumin concentration. This observation is linked with the previous observation that the usual independent site description cannot be used to represent the clinically important low concentration data. All the observed dependences are satisfactorily accounted for by assuming that gold(I) competes with a highly bound contaminant for the high affinity (Cys(34)-SH) site. This description is supported by the experimental observation that a fraction of this site is originally blocked both in vivo and in in vitro. The present interpretation yields a high affinity binding constant 100 times larger than found previously and provides an explanation for the lack of correlation between dose and therapeutic and toxic effects in chrysotherapy.