Effect Of Solution Environment Research Articles

The effect of solution environment and the electrostatic factor on the crystallisation of desmotropes of irbesartan.

The experimental conditions necessary for stabilising irbesartan (IBS) tautomers in solution and selectively obtaining the desmotropic crystal forms are presented herein. 1H and 2H tautomers were stabilized in specific solution conditions and the 2H-tetrazole⋯imidazole interaction was confirmed by solution-state NMR. The results showed that highly polar and polarisable solvents (higher values of the electrostatic factor (EF)) lead to the crystallisation of IBS form B. Furthermore, the variations of pH in methanol, in turn, determined the crystallisation of desmotropes A and/or B.

Effects of solution environment on mammalian cell fermentation broth properties: Enhanced impurity removal and clarification performance

The processing of recombinant proteins from high cell density, high product titer cell cultures containing mammalian cells is commonly performed using tangential flow microfiltration (MF). However, the increased cellular debris present in these complex feed streams can prematurely foul the membrane, adversely impacting MF capacity and throughput. In addition, high cell density cell culture streams introduce elevated levels of process-related impurities, which increase the burden on subsequent purification operations to remove these complex media components and impurities. To address this challenge, an evaluation of mammalian cell culture broth buffer properties was examined to determine if enhanced impurity removal and clarification performance could be achieved. A framework is presented here for establishing optimized mammalian cell culture buffer conditions, involving trade-offs between product recovery and purification and improved clarification at manufacturing-scale production. A reduction in cell culture broth pH to 4.7-5.0 induced flocculation and impurity precipitation which increased the average feed particle-size. These conditions led to enhanced impurity removal and improved MF throughput and filter capacity for several mammalian systems. Feed conditions were further optimized by controlling ionic composition along with pH to improve product recovery from high cell density/high product titer cell cultures.

Effect of Solution Environment on Removal of Colloidal Particles by Immobilization in Calcium Alginate Gel

アルギン酸のカルシウムによるゲル化を利用し，コロイド懸濁質をアルギン酸カルシウムゲル内に包括させ懸濁系から除去する分離プロセスが提案されている．コロイド包括ゲルは，重力脱水後，さらに圧搾脱水される．圧搾に際し，コロイド粒子はゲルの網目に阻まれ，ゲル内にとどまる．圧搾ケークはその後廃棄される．この新規な分離プロセスに対するコロイド懸濁液の溶液環境の影響を調査した．1.8–12.2のpH範囲では，分離プロセスはpHの影響を受けなかった．懸濁液中にNa+イオンが0.6 mol/L程度存在してもその影響はなく，この分離プロセスが海水程度の塩濃度でも成り立つことがわかった．一方，懸濁液中にCa2+イオンやAl3+イオンのような多価イオンが存在するとアルギン酸溶液と懸濁液の混合を妨害するため，これらのイオンはマスキングする必要がある．

Effect of Solution Environment on the Purification of Pertussis Toxin

The low recovery of pertussis toxin (PT) and the low resolving efficiency of chromatography, due to the instability of PT in low salt condition, are the main challenges for its purification. We applied 2 M urea to prevent the aggregation and disassociation of PT during the purification by ionexchange chromatography (IEC) and gel filtration chromatography (GFC). The effect of urea on the purification of PT was investigated by ELISA assay and non-reduced SDS-PAGE. The activity recoveries of PT and filamentous hemagglutinin (FHA) in IEC and GFC, the resolution efficiency in GFC, and the purities of PT and FHA were improved obviously by adding 2 M urea in the mobile phase. The results highlight the potential application of urea in the acellular pertussis vaccine (APV) manufacture procedure.

Properties of protein adsorption onto pore surface during microfiltration: Effects of solution environment and membrane hydrophobicity

Properties of bovine serum albumin (BSA) adsorption onto pore surface during the filtration of BSA containing solution with the Sirasu porous glass membrane with a pore size of 0.1 μm were studied. The effects of pH, ionic strength, and surface modification on the flux decline and breakthrough curves were observed. The adsorption properties of BSA were estimated quantitatively by using the internal fouling model, which relates the filtration performance to the adsorption interaction, the adsorption capacity, and the thickness of the adsorption layer. The electrostatic interaction between BSA and pore surface was estimated by the streaming potential measurement. The BSA adsorption involved a rapid adsorption in the early stage of filtration followed by a slow multilayer adsorption that dominates the long-term filtration performance. The electrostatic repulsive force reduced the overall adsorption interaction but the electrostatic attractive force did not affect the adsorption interaction. The effect of ionic strength on the BSA adsorption could be explained in terms of the shift of the IEP of BSA toward lower pH with the increase in ionic strength. The hydrophobicity of membrane did not affect the adsorption properties except for the adsorption interaction in the early stage of the filtration.

Effects of solution environment on humic acid fouling during microfiltration

Microfiltration is increasingly used in drinking water treatment for the removal of particles, turbidity, and microorganisms to meet more stringent water quality requirements. Fouling by natural organic matter (e.g., humic and fulvic acids) is a critical factor in microfiltration processes. Experiments were performed to evaluate the effects of solution pH, salt concentration, and ionic composition on the extent and mechanisms of humic acid fouling during microfiltration. Fouling was more severe at high salt concentration due to the tighter packing of the charged humic acids within the fouling layer caused by the increased electrostatic shielding. The effects of solution pH were more complex and likely reflect alterations in humic acid charge, hydrophobicity, and extent of aggregation. Divalent cations such as calcium significantly increased humic acid fouling and aggregation through the formation of intra- or intermolecular bridges between the negatively charged humic acid molecules. These results provide important insights into the physical and chemical interactions governing humic acid fouling during microfiltration.

Three-dimensional solution structure of alpha-conotoxin MII by NMR spectroscopy: effects of solution environment on helicity.

alpha-Conotoxin MII, a 16-residue polypeptide from the venom of the piscivorous cone snail Conus magus, is a potent and highly specific blocker of mammalian neuronal nicotinic acetylcholine receptors composed of alpha3 beta2 subunits. The role of this receptor type in the modulation of neurotransmitter release and its relevance to the problems of addiction and psychosis emphasize the importance of a structural understanding of the mode of interaction of MII with the alpha3 beta2 interface. Here we describe the three-dimensional solution structure of MII determined using 2D 1H NMR spectroscopy. Structural restraints consisting of 376 interproton distances inferred from NOEs and 12 dihedral restraints derived from spin-spin coupling constants were used as input for simulated annealing calculations and energy minimization in the program X-PLOR. The final set of 20 structures is exceptionally well-defined with mean pairwise rms differences over the whole molecule of 0.07 A for the backbone atoms and 0.34 A for all heavy atoms. MII adopts a compact structure incorporating a central segment of alpha-helix and beta-turns at the N- and C-termini. The molecule is stabilized by two disulfide bonds, which provide cross-links between the N-terminus and both the middle and C-terminus of the structure. The susceptibility of the structure to conformational change was examined using several different solvent conditions. While the global fold of MII remains the same, the structure is stabilized in a more hydrophobic environment provided by the addition of acetonitrile or trifluoroethanol to the aqueous solution. The distribution of amino acid side chains in MII creates distinct hydrophobic and polar patches on its surface that may be important for the specific interaction with the alpha3beta2 neuronal nAChR. A comparison of the structure of MII with other neuronal-specific alpha-conotoxins provides insights into their mode of interaction with these receptors.

Effect of Solution Environment on Dead-End Microfiltration Characteristics of Rutile Suspensions.

Microfiltration experiments were conducted under a constant pressure of 196 kPa, using a dead-end filter. The filtration properties were studied using titanium dioxide suspensions of the rutile form to determine the effects of such solvent environments as pH and the added salt. Both the average porosity and the average specific filtration resistance of the filter cake were determined. It was highlighted through this study that the electrical nature of particles depending on the solution environment plays a significant role in determining the structure of the filter cake which, in turn, influenced the filtration rate in microfiltration of dispersions of metal oxides. It was demonstrated unequivocally that the average porosity in the filter cake had a maximum and the average specific filtration resistance was minimal around the isoelectric pH. These results were in contrast to those observed with ultrafiltration of protein solutions. Such charge effects of particles were weakened in the presence of salts.

Effect of solution environment on the permeability of red blood cells

The cell membrane permeability governs the rate of solute transport into and out of the cell, significantly affecting the cell's metabolic processes, viability, and potential usefulness in both biotechnological applications and physiological systems. Most previous studies of the cell membrane permeability have neglected the possible effects of suspending medium on membrane transport, even though there is extensive experimental evidence that suspending phase composition can significantly affect other properties related to the cell membrane (e.g., cell deformability, fragility, and aggregation rate). This study examined the effects of suspending phase composition (both proteins and electrolytes) on the permeability of human red blood cells to the metabolites creatinine and uric acid. Data were obtained using a stirred ultrafiltration device with direct cell- and proteinfree sampling through a semipermeable membrane. Both the uric acid and creatinine permeabilities were strongly affected by the suspending phase composition, with the permeabilities in different buffer solutions varying by as much as a factor of three. The predominant factors affecting the permeability were the presence (or absence) of chloride, phosphate/adenine, and proteins, although the magnitude and even the direction of these effects were significantly different for creatinine and uric acid transport. The dramatic differences in behavior for uric acid and creatinine reflect the different transport mechanisms for these solutes, with uric acid transported by a carrier-mediated mechanism and creatinine transported by passive diffusion through the lipid bilayer. These results provide important insights into the effects of solution environment on cell membrane transport and other cell membrane-mediated properties.

Electronic spectra of adenine and guanine: Assignments and effects of solution environment

The results obtained by us on the ultraviolet absorption and fluorescence spectra of adenine and guanine and partially those of 8-azaguanine and 8-bromoguanine have been discussed and interpreted with the help of molecular orbital calculations. Effects of oxygenation and nitrogenation on the spectra and possible tautomerisations of molecules induced by oxygen and UV irradiation have mainly been the subjects of interest. Oscillations observed in the absorption spectra of guanine in aqueous solutions under UV irradiation have been interpreted in terms of the tautomerisation of the molecule following its slow complexation with the dissolved oxygen. This complexation of oxygen with guanine in DNA may cause lethal damage to biological systems including carcinogenesis.

Effect of solution environment on unstirred dead-end ultrafiltration characteristics of proteinaceous solutions.

The effects of pH and the addition of such salts as NaCl on the structure of the gel-cake in dead-end ultrafiltration of BSA solutions are examined by using a batchwise filter which has an abrupt reduction in its filtration area. Both the average porosity eav and the average specific filtration resistance αav of the gel-cake may be determined accurately on the basis of measurements of the variation of filtrate volume with time. The most compact gel-cake, which provides a large flow resistance, forms on the membrane around the isoelectric pH. By the addition of NaCl at pH extremes the gel-cake structure becomes compact, thereby decreasing the filtration rate. Such internal structures as the solute concentration and the compressive pressure acting on the solutes within the gel-cake, which may serve as a basis for evaluating the sweeping performance of the gel-cake in crossflow ultrafiltration, are evaluated on the basis of the overall filtration characteristics obtained under various filtration pressure conditions.