Now that enzymes are available that are stable above 100 mC it is possible to investigate conformational stability at this temperature, and also the effect of high-temperature degradative reactions in functioning enzymes and the inter-relationship between degradation and denaturation. The conformational stability of proteins depends upon stabilizing forces arising from a large number of weak interactions, which are opposed by an almost equally large destabilizing force due mostly to conformational entropy. The difference between these, the net free energy of stabilization, is relatively small, equivalent to a few interactions. The enhanced stability of very stable proteins can be achieved by an additional stabilizing force which is again equivalent to only a few stabilizing interactions. There is currently no strong evidence that any particular interaction (e.g. hydrogen bonds, hydrophobic interactions) plays a more important role in

Multiplexed photoaptamer-based arrays that allow for the simultaneous measurement of multiple proteins of interest in serum samples are described. Since photoaptamers covalently bind to their target analytes before fluorescent signal detection, the arrays can be vigorously washed to remove background proteins, providing the potential for superior signal-to-noise ratios and lower limits of quantification in biological matrices. Data are presented here for a 17-plex photoaptamer array exhibiting limits of detection below 10 fM for several analytes including interleukin-16, vascular endothelial growth factor, and endostatin and able to measure proteins in 10% serum samples. The assays are simple, scalable, and reproducible. Affinity of the capture reagent is shown to be directly correlated to the limit of detection for the analyte on the array.

The stability of two enzymes from extreme thermophiles (glutamate dehydrogenase from Thermococcales strain AN1 and beta-glucosidase from Caldocellum saccharolyticum expressed in Escherichia coli) has been exploited to allow measurement of activity over a 175 degrees C temperature range, from +90 degrees C to -85 degrees C for the glutamate dehydrogenase and from +90 degrees C to -70 degrees C for the beta-glucosidase. The Arrhenius plots of these enzymes, and those for two mesophilic enzymes (glutamate dehydrogenase from bovine liver and beta-galactosidase from Escherichia coli), exhibit no downward deflection corresponding to the glass transition, found by biophysical measurements of several non-enzymic mesophilic proteins at about -65 degrees C and reflecting a sharp decrease in protein flexibility as the overall motion of groups of atoms ceases.

Covalently linked bipyridyl ligands (L-L) with alkyl linkages varying from (--CHz--)2 to (--CH2--)12 were used to prepare ruthenium oxo dimers of the form [(bpy) (H20)RuO(L-L)Ru(H20) (bpy)] 4 § The bridging alkyl linkage increases the stability of these oxo dimers by maintaining the relative proximity of the two ruthenium centers even when the oxo bridge is cleaved. These complexes have been characterized by electronic spectroscopy and electrochemistry. The electrochemistry in CH3CN/0.1M TBAP exhibits a reversible one-electron oxidation followed by a second reversible two-electron oxidation which becomes catalytic in aqueous solution. The catalytic generation of dioxygen from water was observed upon bulk electrolysis of the oxo dimer at +1.39 V.

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