A novel microfabricated multichannel emitter for electrospray ionization mass spectrometry (ESI-MS) was implemented with polydimethylsiloxane (PDMS) using a soft lithography technique. The emitters are formed as electrospray tips along a thin membrane on the edge of the device with channels of 100 microm x 30 microm dimensions. The electrospray performance of the PDMS emitters for a single channel device and a four channel device interfaced with a time-of-flight mass spectrometer was evaluated for detecting the molecular weight of reference peptides (angiotensin I and bradykinin). The emitters were durable at the flow rate of 1-20 microL min(-1) for more than 30 h of continuous electrospray with limit of detection of 1 microM (S/N 18). This microfabrication method for a PDMS multichannel emitter as an integral part of a microfluidic device will facilitate development of more complex microfluidic analysis systems using ESI-MS.

The complete oxidation of methane into water and carbon dioxide on the (111) surface of ceria is considered within a DFT + U framework in order to gain insight into the coke-free operation of solid oxide fuel cells with ceria-containing anodes. Preferred adsorption sites and energies are determined for CH x (x ) 0, ..., 3), H, and CO, together with transition states and kinetic barriers along the complete pathway from CH 4 to H 2 O and CO 2 . The results presented are in excellent agreement with existing theoretical and experimental work suggesting that ceria is more easily reduced by CO than by H 2 and offer an explanation for the apparently inconsistent observations of carbon coke formation in Ni-ceria anodes and the stable, coke-free oxidation of methane in Cu-ceria anodes.

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A simple light-actuated microvalve using a quartz halogen illuminator with tungsten filament was introduced to manipulate flow path effectively in micro-total analysis systems, which reduces system complexity and the need for on-chip integration. The microvalve device in cyclic olefin copolymer (COC) microchip functions very well based on the thermo-responsive polymer, poly(N-isopropylacrylamide) (PNIPAAm), whose pressure-tolerance can be tuned by changing the mechanical strength of polymer monolith inside the microchannel with the choice of suitable amount of monomer and crosslinker. The response time and pressure resistance of the valve can be optimized by the tetrahydrofuran composition in the polymerization mixture as well. Very importantly, the microvalve can withstand the leakage pressure up to around 1350 psi, and its opening and closing response time is only 4.0 and 6.2 s respectively. Microchips with such valves will be very useful in drug delivery, chemical analysis and proteomic analysis.

Rpe65 ؊/؊ mice produce minimal amounts of 11-cis-retinal, the ligand necessary for the formation of photosensitive visual pigments. Therefore, the apoprotein opsin in these animals has not been exposed to its normal ligand. The Rpe65 ؊/؊ mice contain less than 0.1% of wild type levels of rhodopsin. Mass spectrometric analysis of opsin from Rpe65 ؊/؊ mice revealed unusually high levels of phosphorylation in dark-adapted mice but no other structural alterations. Single flash and flicker electroretinograms (ERGs) from 1-month-old animals showed trace rod function but no cone response. B-wave kinetics of the single-flash ERG are comparable with those of dark-adapted wild type mice containing a full compliment of rhodopsin. Application (intraperitoneal injection) of 11-cis-retinal to Rpe65 ؊/؊ mice increased the rod ERG signal, increased levels of rhodopsin, and decreased opsin phosphorylation. Therefore, exogenous 11-cis-retinal improves photoreceptor function by regenerating rhodopsin and removes constitutive opsin phosphorylation. Our results indicate that opsin, which has not been exposed to 11-cis-retinal, does not generate the activity generally associated with the bleached apoprotein.RPE65 is a major protein in the retinal pigment epithelium (RPE) 1 (1) and has also been identified in cone photoreceptors (2, 3). The photoreceptors of Rpe65 Ϫ/Ϫ mice are almost completely depleted of 11-cis-retinal, the native ligand of cone and rod opsins, resulting in minimal levels of rhodopsin and the deterioration of their photosensitivity (4). Photoreceptor function has been shown to be partially restored by supplying exogenous ligand (5, 6). Thus, the Rpe65 Ϫ/Ϫ mouse is an excellent model in which to study the two key factors that control the activity of rhodopsin, the supply of the ligand (7, 8) and the level of rhodopsin/opsin phosphorylation. Therefore, we have analyzed opsin phosphorylation levels of Rpe65 Ϫ/Ϫ mice and correlated those levels with electroretinogram (ERG) responses and rhodopsin levels in the absence and presence of exogenous 11-cis-retinal.Retinal function is controlled by the availability of 11-cisretinal, which can be affected by the absence or dysfunction of any number of participants in the retinal metabolic pathway (e.g. Refs. 9 and 10). RPE65 is essential for production of 11-cis-retinoids (4). RPE65 mutations in humans result in congenital retinal dystrophies ranging from night blindness to loss of vision (11). Although night blindness would suggest loss of rod rather than cone function, the ERG retained in Rpe65 Ϫ/Ϫ mice appears to originate from rod photoreceptors (12).A second key factor that controls visual sensitivity is opsin/ rhodopsin phosphorylation. The C terminus of activated rhodopsin is multiply phosphorylated by rhodopsin kinase (G protein-coupled receptor kinase 1) (13) in vivo (14,15), and this multiple phosphorylation has been shown to be necessary for the rapid return of sensitivity (16). In moderate light levels, it has been proposed that opsin dephosphorylation and its regen...