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Column Volumes (column + volume)

Distribution by Scientific Domains

Life Sciences	50%

Selected Abstracts

Probabilistic evaluation of seismic performance of 3-story 3D one- and two-way steel moment-frame structures

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 5 2008
Hiroyuki Tagawa
Abstract This paper presents the results of a probabilistic evaluation of the seismic performance of 3D steel moment-frame structures. Two types of framing system are considered: one-way frames typical of construction in the United States and two-way frames typical of construction in Japan. For each framing system, four types of beam,column connections are considered: pre-Northridge welded-flange bolted-web, post-Northridge welded-flange welded-web, reduced-beam-section, and bolted-flange-plate connections. A suite of earthquake ground motions is used to compute the annual probability of exceedence (APE) for a series of drift demand levels and for member plastic-rotation capacity. Results are compared for the different framing systems and connection details. It is found that the two-way frames, which have a larger initial stiffness and strength than the one-way frames for the same beam and column volumes, have a smaller APE for small drift demands for which members exhibit no or minimal yielding, but have a larger APE for large drift demands for which members exhibit large plastic rotations. However, the one-way frames, which typically comprise a few seismic frames with large-sized members that have relatively small rotation capacities, may have a larger APE for member failure. The probabilistic approach presented in this study may be used to determine the most appropriate frame configuration to meet an owner's performance objectives. Copyright © 2008 John Wiley & Sons, Ltd. [source]

A theoretical explanation for the retention mechanism of ion exclusion chromatography

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2003
Bronis, aw K. G
Abstract Ion Exclusion Chromatography is classically used for the separation of weak acid anions. Dilute strong acids (e.g. sulphuric or perchloric acid) or just water are used as eluents. To increase the exclusion effect, strong cation exchangers, characterized by high concentration of functional groups, are applied. The inner column volume of commercially available columns is increased by increasing their size in comparison to traditional ones (usually 300×7.8 mm ID). The description of the retention mechanism of this technique implicitly assumes that both mobile and stationary phases are typical aqueous solutions, and their dielectric constants are thus equal. This equality implies the equality of solute dissociation constants in both phases. Another implicit assumption is that the dead- and inner volumes of the column are constant, and independent of the mobile phase composition. The present paper shows that stationary and mobile phases are generally characterized by different physicochemical parameters. Thus, they cannot be considered as regular aqueous solutions. Additionally, we show that weak cation exchanger resins, which are characterized by a relatively small concentration of the functional groups, and weak acid based buffers can also be used in IEC. This would expand the possible applications of this method and enable, for example, the separation of strong acids (anions). The influence of ionic strength on the retention and dead- and inner column volumes is also discussed. Finally we also briefly describe the retention mechanism of Electrostatic Ion Chromatography. [source]

Characterization of cryogel monoliths for extraction of minor proteins from milk by cation exchange

BIOTECHNOLOGY & BIOENGINEERING, Issue 6 2009
Jagan M. Billakanti
Abstract Extraction and purification of high-value minor proteins directly from milk without pre-treatment is a challenge for the dairy industry. Pre-treatment of milk before extraction of proteins by conventional packed-bed chromatography is usually necessary to prevent column blockage but it requires several steps that result in significant loss of yield and activity for many minor proteins. In this paper, we demonstrate that it is possible to pass 40,50 column volumes of various milk samples (raw whole milk, homogenized milk, skim milk and acid whey) through a 5 mL cryogel chromatographic column at 550 cm/h without exceeding its pressure limits if the processing temperature is maintained above 35°C. The dynamic binding capacity obtained for the cryogel matrix (2.1 mg/mL) was similar to that of the binding capacity (2.01 mg/mL) at equilibrium with 0.1 mg/mL of lactoferrin in the feed samples. The cryogel column selectively binds lactoferrin and lactoperoxidase with only minor leakage in flowthrough fractions. Lactoferrin was recovered from elution fractions with a yield of over 85% and a purity of more than 90%. These results, together with the ease of manufacture, low cost and versatile surface chemistry of cryogels suggest that they may be a good alternative to packed-bed chromatography for direct capture of proteins from milk. Biotechnol. Bioeng. 2009;103: 1155,1163. © 2009 Wiley Periodicals, Inc. [source]

Screening of Protein-Ligand Interactions by Affinity Chromatography

BIOTECHNOLOGY PROGRESS, Issue 2 2003
Carlos D. García
This paper examines affinity chromatography (AC) as an alternative tool for the determination of protein-ligand interactions for the particular case in which the ligand is the same protein. The methodology is less labor-intensive and more sample-efficient than traditional methods used to measure the second virial coefficient ( B22), a parameter commonly used to evaluate protein-protein interactions. The chromatographic capacity factor ( k,) was studied for lysozyme and equine serum albumin for a wide range of experimental solution conditions such as crystallizing agent concentration, protein concentration and pH. Parallel experiments using AC to determine k, and static light scattering (SLS) to determine B22 showed that the two parameters were highly correlated. Two different column volumes (,1 and ,0.1 mL) were tested and gave essentially the same values for k,, showing the feasibility of miniaturization. [source]