ABSTRACT
Protein crystallization still remains mostly an empirical science, as the production of crystals with the required quality for X-ray analysis is dependent on the intensive screening of the best protein crystallization and crystal's derivatization conditions. Herein, this demanding step was addressed by the development of a high-throughput and low-budget microfluidic platform consisting of an ion exchange membrane (117 Nafion® membrane) sandwiched between a channel layer (stripping phase compartment) and a wells layer (feed phase compartment) forming 75 independent micro-contactors. This microfluidic device allows for a simultaneous and independent screening of multiple protein crystallization and crystal derivatization conditions, using Hen Egg White Lysozyme (HEWL) as the model protein and Hg2+ as the derivatizing agent. This microdevice offers well-regulated crystallization and subsequent crystal derivatization processes based on the controlled transport of water and ions provided by the 117 Nafion® membrane. Diffusion coefficients of water and the derivatizing agent (Hg2+) were evaluated, showing the positive influence of the protein drop volume on the number of crystals and crystal size. This microfluidic system allowed for crystals with good structural stability and high X-ray diffraction quality and, thus, it is regarded as an efficient tool that may contribute to the enhancement of the proteins' crystals structural resolution.
ABSTRACT
Cu-based metal-organic framework (MOF) microdevices are applied in sampling and preconcentration of nerve agents (NAs) diluted in gaseous streams. An in situ electrochemical-assisted synthesis of a Cu-benzene-1,3,5-tricarboxylate (BTC) thick film is carried out to functionalize a Cu-modified glass substrate. This simple, rapid, reproducible, and easy-to-integrate MOF synthesis approach enables the microfabrication of functional micro-preconcentrators with a large Brunauer-Emmett-Teller (BET) surface area (above 2000 cm2) and an active pore volume (above 90 nL) for the efficient adsorption of nerve agent molecules along the microfluidic channel 2.5 cm in length. The equilibrium adsorption capacity of the bulk material has been characterized through thermogravimetric analysis after exposure to controlled atmospheres of a sarin gas surrogate, dimethyl methylphosphonate (DMMP), in both dry and humid conditions (30% RH at 293 K). Breakthrough tests at the ppm level (162 mg/m3) reveal equilibrium adsorption capacities up to 691 mg/g. The preconcentration performance of such µ-devices when dealing with highly diluted surrogate atmosphere, i.e., 520 ppbV (2.6 mg/m3) at 298 K, leads to preconcentration coefficients up to 171 for sample volume up to 600 STP cm3. We demonstrate the potentialities of Cu-BTC micro-preconcentrators as smart first responder tools for "on-field" detection of nerve agents in the gas phase at relevant conditions.
Subject(s)
Copper/chemistry , Metal-Organic Frameworks/chemistry , Nerve Agents/analysis , Tricarboxylic Acids/chemistry , Adsorption , Particle Size , Potentiometry , Surface PropertiesABSTRACT
BACKGROUND: The Short-Stay Medical Unit (SSMU) is an alternative to conventional hospitalization. This study has aimed to analyze the evolution of admissions and duration of stay in a SSMU, to outline the characteristics of the patients while studying their relationship to length of time spent in the unit and their destination on discharge as well as to assess how appropriately their cases were resolved. MATERIAL AND METHODS: A descriptive study was carried out (2000-2005), analyzing their age, sex, destination on discharge and main diagnosis as well as the evolution of admissions and length of stay over this period. In order to determine how appropriately each case was resolved, length of stay and destination on discharge were considered. The data were analyzed using the SPSS program. RESULTS: During the study period there was an increase in the number of admissions and in length of stay. The average age of the 7,618 patients was 70.6 +/- 16.9 years and the average stay 2.7 +/- 1.4 days. One of the most frequent diagnoses was chronic obstructive pulmonary disease (COPD) (15.9%). On discharge, 85.9% of patients were sent home. A total of 76.4% of cases were resolved satisfactorily, with significant statistical differences related to age, diagnosis and number of diagnoses. CONCLUSIONS: A progressive increase in admissions and length of stay was observed. Ninety percent of the cases of the younger patients were resolved satisfactorily, this decreasing to 72% for older patients. The number of diagnoses, specific diagnoses and age caused some difficulty in reaching an appropriate resolution.
