Demonstration of the FLASH Effect Within the Spread-out Bragg Peak After Abdominal Irradiation of Mice.

Purpose: The effects of FLASH-level dose rates delivered at the spread-out Bragg peak (SOBP) on normal tissue damage in mice were investigated. Materials and Methods: Fifty nontumor-bearing mice received abdominal irradiation, 30 at FLASH dose rates (100 Gy/s) and 20 at conventional dose rates (0.1 Gy/s). Total dose values ranged from 10 to 19 Gy, delivered in a single spot by a synchrocyclotron proton therapy system. Centered on the abdomen, the collimated field delivered was an 11-mm diameter circle with a water-equivalent depth of 2.4 cm from entrance to distal 80% dose. A ridge filter was used to provide dose uniformity over the full 2.4-cm range. The spatial distribution was identical for both the FLASH and conventional deliveries. Results: Overall survival and individual mouse weights were tracked for 21 days after the exposure date, and LD50 values were compared for the FLASH and conventional dose rate groups. Mice exposed to FLASH dose rates had a higher LD50 value as compared with mice exposed to conventional dose rates, with a dose-dependent improvement in survivability of 10% to 20%. The FLASH cohort also showed greater or equal percent population survival for each day of the study. Conclusion: These results are preliminary confirmation of the potential for the combination of the advantages of the Bragg peak with the normal tissue sparing benefits of FLASH treatments. This experiment also confirms that pulsed synchrocyclotrons can be used for the purpose of FLASH research and treatment.

An NMR based phosphodiesterase assay.

We propose a phosphodiesterase assay based on 1D 1H NMR to monitor the hydrolysis of cyclic nucleotides directly, without requiring tags or the addition of exogenous reagents. The method is suitable to measure phosphodiesterase KM and kcat parameters and to identify phosphodiesterase inhibitors.

High-throughput screening of chromatographic separations: IV. Ion-exchange.

Ion-exchange (IEX) chromatography steps are widely applied in protein purification processes because of their high capacity, selectivity, robust operation, and well-understood principles. Optimization of IEX steps typically involves resin screening and selection of the pH and counterion concentrations of the load, wash, and elution steps. Time and material constraints associated with operating laboratory columns often preclude evaluating more than 20-50 conditions during early stages of process development. To overcome this limitation, a high-throughput screening (HTS) system employing a robotic liquid handling system and 96-well filterplates was used to evaluate various operating conditions for IEX steps for monoclonal antibody (mAb) purification. A screening study for an adsorptive cation-exchange step evaluated eight different resins. Sodium chloride concentrations defining the operating boundaries of product binding and elution were established at four different pH levels for each resin. Adsorption isotherms were measured for 24 different pH and salt combinations for a single resin. An anion-exchange flowthrough step was then examined, generating data on mAb adsorption for 48 different combinations of pH and counterion concentration for three different resins. The mAb partition coefficients were calculated and used to estimate the characteristic charge of the resin-protein interaction. Host cell protein and residual Protein A impurity levels were also measured, providing information on selectivity within this operating window. The HTS system shows promise for accelerating process development of IEX steps, enabling rapid acquisition of large datasets addressing the performance of the chromatography step under many different operating conditions.