Partitioning behavior and enrichment of proteins with reversed micellar extraction: I. forward extraction of proteins from aqueous to reversed micellar phase

Protein extractions using aerosol OT (AOT)-isooctane reverse micelle solutions have been studied to explore the potential for separating and enriching proteins with the reversed micellar extraction. The effects of pH, ionic strength, and different cations of chlorides in a bulk aqueous phase and of AOT concentration in an organic phase on the partitioning of lysozyme and myoglobin and the solubilization of water are presented in detail. The extraction of lysozyme was affected by the concentration of potassium or barium but was almost independent of that of sodium or calcium, whose ionic diameter is smaller than that of potassium and barium. For the extraction of myoglobin, however, the effect of barium concentration was not appreciable. Lysozyme could be enriched into the reversed micellar phase up to 30 times the aqueous feed concentration. (c) 1993 John Wiley & Sons, Inc.     

检测病毒气溶胶存活的方法学研究

以钝齿棒状杆菌噬菌体B271血清型为病毒等小颗粒生物粒子的模拟剂,建立了一种适合这类小颗粒生物粒子气溶胶存活研究的方法。本文从该噬菌体耐气溶胶化特性、气溶胶粒谱、用气溶胶示踪剂求算物理衰亡的方法和气溶胶采样回收技术等方面探讨了病毒气溶胶存活研究中的几个关键技术问题,为病毒气溶胶存活研究提供了参考。     

“21世纪海上丝绸之路”沿线典型城市气溶胶光学厚度时空分布特征与成因

气溶胶作为悬浮分散在大气中的固态或液态微小颗粒物,对人体健康具有巨大影响,探索区域大气气溶胶变化特征和规律,对监测评估大气环境质量(尤其是人口聚集的城市地区)具有重要意义。本研究以东南亚、南亚和西亚“21世纪海上丝绸之路”沿线9个典型支点城市为例,基于MCD19A2 550 nm AOD产品,结合气象因素、土地利用数据和夜间灯光数据等,探讨亚洲发达城市区域带气溶胶的时空分布、变化特征、影响因素和成因驱动。结果表明: 2013—2018年间,9个城市气溶胶光学厚度(AOD)年平均值从高到低依次为卡拉奇、多哈、吉大港、曼谷、科伦坡、胡志明市、新加坡、瓜达尔和仰光。受区域气候系统和气溶胶类型的影响,各地区年、季和月AOD时序特征差异显著。大多数城市AOD高值区主要分布在城市中心区域或社会经济(如工农业)快速发展的地区。不同气象因素对各地区AOD的影响略有差异:降雨量、相对湿度和风速对东南亚4个城市(胡志明市、曼谷、新加坡和仰光)的影响较大,温度、相对湿度和风速与南亚4个城市(吉大港、科伦坡、卡拉奇和瓜达尔)和西亚多哈的AOD相关性较大。城市区域AOD受社会经济、城市化发展以及气象因素耦合协同作用的综合影响,其中,卡拉奇表现得最显著。     

Global ammonia emissions from synthetic nitrogen fertilizer applications in agricultural systems: Empirical and process‐based estimates and uncertainty

Excessive ammonia (NH₃) emitted from nitrogen (N) fertilizer applications in global croplands plays an important role in atmospheric aerosol production, resulting in visibility reduction and regional haze. However, large uncertainty exists in the estimates of NH₃ emissions from global and regional croplands, which utilize different data and methods. In this study, we have coupled a process‐based Dynamic Land Ecosystem Model (DLEM) with the bidirectional NH₃ exchange module in the Community Multiscale Air‐Quality (CMAQ) model (DLEM‐Bi‐NH₃) to quantify NH₃ emissions at the global and regional scale, and crop‐specific NH₃ emissions globally at a spatial resolution of 0.5° × 0.5° during 1961–2010. Results indicate that global NH₃ emissions from N fertilizer use have increased from 1.9 ± 0.03 to 16.7 ± 0.5 Tg N/year between 1961 and 2010. The annual increase of NH₃ emissions shows large spatial variations across the global land surface. Southern Asia, including China and India, has accounted for more than 50% of total global NH₃ emissions since the 1980s, followed by North America and Europe. Rice cultivation has been the largest contributor to total global NH₃ emissions since the 1990s, followed by corn and wheat. In addition, results show that empirical methods without considering environmental factors (constant emission factor in the IPCC Tier 1 guideline) could underestimate NH₃ emissions in context of climate change, with the highest difference (i.e., 6.9 Tg N/year) occurring in 2010. This study provides a robust estimate on global and regional NH₃ emissions over the past 50 years, which offers a reference for assessing air quality consequences of future nitrogen enrichment as well as nitrogen use efficiency improvement.     

Unusual Behavior of Membrane Somatic Angiotensin-Converting Enzyme in a Reversed Micelle System

Properties of the membrane and soluble forms of somatic angiotensin-converting enzyme (ACE) were studied in the system of hydrated reversed micelles of aerosol OT (AOT) in octane. The membrane enzyme with a hydrophobic peptide anchor was more sensitive to anions and to changes in pH and composition of the medium than the soluble enzyme without anchor. The activity of both forms of the enzyme in the reversed micelles significantly depended on the molarity of the buffer added to the medium (Mes-Tris-buffer, 50 mM NaCl). The maximum activity of the soluble ACE was recorded at buffer concentration of 20-50 mM, whereas the membrane enzyme was most active at 2-10 mM buffer. At buffer concentrations above 20 mM, the rate of hydrolysis of the substrate furylacryloyl-L-phenylalanyl-glycylglycine by both ACE forms was maximal at pH 7.5 both in the reversed micelles and in aqueous solutions. However, at lower concentrations of the buffer (2-10 mM), the membrane enzyme had activity optimum at pH 5.5. Therefore, it is suggested that two conformers of the membrane ACE with differing pH optima for activity and limiting values of catalytic constants should exist in the reversed micelle system with various medium compositions. The data suggest that the activity of the membrane-bound somatic ACE can be regulated by changes in the microenvironment.     

Low-temperature micronization of a peptide drug in fluid propellant: Case study cetrorelix

Aim of this study was to elaborate an efficient method for the micronization of the decapeptide cetrorelix (a GnRH-antagonist), in order to obtain a microsuspension as basis for other pharmaceutical preparations, such as e.g. inhalation aerosols. A modified pearl-mill coupled with a cryostat was used for the micronization of cetrorelix in fluid propellant and operated under different conditions. The obtained cetrorelix suspensions were analyzed for particle size distribution, purity of cetrorelix, and for metal contamination through abrasion from parts of the mill. The method allowed an effective micronization of cetrorelix. The mean particle size of the initial cetrorelix lyophilizate bulk ware was reduced from 52.5 μ (Volume Mean Diameter, VMD) down to 14.9, 6.1 and 3.1 μm, respectively, respectively. The HPLC analysis of all cetrorelix suspensions after micronization did not show signs of decomposition as compared to the initial product. The elementary analysis of the suspensions performed by inductively coupled plasma mass spectrometry revealed a negligible amount of contaminants in the suspension (Zr=max. 0.6 ppm; Fe, Cr, Ni, Ba, below limit of quantification, i.e.<0.14 ppm). The only appreciable contaminant. Aluminum (Al=1.1 ppm), was derived from the mechanical capping of aluminum canisters prior to analysis. The Zr determination in the suspension of 0.6 ppm, is still considered to be negligible as compared to the legally tolerated limit of air contamination. By low-temperature micronization in fluid propellant, fine drug suspensions of cetrorelix for pMDIs can be directly manufactured in one-step procedure without destruction of the peptide structure and without appreciable product contamination. Published: July 12, 2001.     

Powder properties and their influence on dry powder inhaler delivery of an antitubercular drug

The purpose of this study was to determine if aerosol delivery of drug loaded microparticles to lungs infected withMycobacterium tuberculosis may be achieved by predicting dispersion of dry powders through knowledge of particle surface properties. Particle sizes of rifampicin-loaded poly(lactide-co-glycolide) microparticles (R-PLGA), rifampicin alone, and lactose and maltodextrin carrier particles (bulk and 75-125-μm sieved fractions) were determined by electron microscopy for the projected area diameter (D_p) and laser diffraction for the volume diameter (D_v). Surface energies (Y) of R-PLGA, rifampicin alone, lactose, and maltodextrin were obtained by inverse phase gas chromatography, surface areas (S_a) by N₂ adsorption, and cohesive energy densities by calculation. Particle dispersion was evaluated (Andersen nonviable impactor) for 10% blends of R-PLGA and rifampicin alone with bulk and sieved fractions of the carriers. D_p for R-PLGA and rifampicin alone was 3.02 and 2.83 μm, respectively. D_v was 13±1 and 2±1 μm for R-PLGA and rifampicin alone, respectively, indicating that R-PLGA was more aggregated. This was evident in Y of 35±1 and 19±6 mJ/m² for R-PLGA and rifampicin alone. D_p for lactose and maltodextrin (sieved and bulk) was approximately 40 mm. Bulk maltodextrin (D_v=119±6 mm) was more aggregated than bulk lactose (D_v=54±2 mm). This was a result of the higher S_a for maltodextrin (0.54 m²/g) than for lactose (0.21 m²/g). The Y of bulk lactose and maltodextrin was 40±4 and 60±6 mJ/m² and of sieved lactose and maltodextrin was 39±1 and 50±1 mJ/m². Impaction studies yielded higher fine particle fractions of R-PLGA from sieved lactose, 13%±3%, than from sieved maltodextrin, 7%±1%, at 90 L/min. An expression, based on these data, is proposed as a predictor of drug dispersion from carrier particles. Delivery of dry powder formulations can be achieved by characterizing particle surfaces and predicting impact on dispersion.