Optimization of protein formulations at subzero temperatures is required for many applications such as storage, transport, and lyophilization. Using isochoric cooling (constant volume) is possible to reach subzero temperatures without freezing aqueous solutions. This accelerates protein damage as protein may unfold by cold denaturation and diffusional and conformational freedom is still present. The use of isochoric cooling to faster protein formulations was first demonstrated for the biomedical relevant protein disulfide isomerase A1. Three osmolytes, sucrose, glycerol, and L-arginine, significantly increased the stability of protein disulfide isomerase A1 at-20 C with all tested under isochoric cooling within the short time frame of 700 h. The redox green fluorescent protein 2 was used to evaluate the applicability of isochoric cooling for stability analysis of highly stable proteins. This derivative of GFP is 2.6-fold more stable than the highly stable GFP b-barrel structure. Nevertheless, it was possible to denature a fraction of roGFP2 at À20 C and to assign a stabilizing effect to sucrose. Isochoric cooling was further applied to insulin. Protein damage was evaluated through a signaling event elicited on human hepatocyte carcinoma cells. Insulin at À20 C under isochoric cooling lost 22% of its function after 15 days and 0.6M sucrose prevented insulin deactivation.
Carbon dots doped with Eu3+ ions (Eu-Cdots) were prepared by a hydrothermal treatment, using citric acid and urea as precursors and Eu (NO3)3 as a europium source. The Eu3+ ions are strongly coordinated with the carboxylate groups at the surface of the Cdots and incorporated within the nanographene network in the carbon core. Vibrational spectroscopy provides evidence of such interaction with identification of bands assigned to the stretching of the Eu-O bond. Eu3+ doped Cdots have larger diameters then undoped Cdots, but they are divided into smaller domains of sp2 carbon. The UV-vis excitation spectrum provides evidence of energy transfer from the Cdots to the Eu3+. The luminescence spectrum shows the characteristic sharp peaks of Eu3+ in the red part of the visible spectrum and a broad emission of Cdots centered at 450 nm. The luminescence of the Cdots is strongly quenched by Hg2+ and Ag+, but not by other cations. The quenching mechanism differs significantly depending on the nature of the ion. Both the blue emission of Cdots and the red emission of Eu3+ are quenched in the presence of Hg2+ while only the emission of the Cdots is affected by the presence of Ag+. A ratiometric sensor can be built using the ratio of luminescence intensities of the Cdots to the Eu3+ peaks.
Timing RPCs are Resistive Plate Chambers made with glass and metal electrodes separated by precision spacers. Typical gas gaps are a few hundred micrometers wide. Such counters were introduced in 1999 and have since reached timing accuracies below 50 ps s with efficiencies above 99% for MIPs. Applications in high-energy physics have already taken place with several more under study.Some recent developments include the extension of the counting rate capability by over one order of magnitude, to 25 kHz/cm 2 ; with time resolutions below 100 ps s: A prototype RPC-based Positron Emission Tomograph yielded a reconstructed point-source resolution of 0:6 mm FWHM and a modified timing RPC design, featuring 50 mm pitch anode strips, allowed to reach extremely good position resolution for hard X-rays in digital readout mode. An analytically solvable model has allowed us to clarify the basic factors influencing the time resolution. r
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