Expanded bed protein A affinity chromatography of a recombinant humanized monoclonal antibody: process development, operation, and comparison with a packed bed method.

We show that expanded bed protein A affinity chromatography using Streamline rProtein A media is an efficient method for purifying a recombinant humanized monoclonal antibody from unclarified Chinese hamster ovary cell culture fluid and that it provides purification performance comparable to using a packed bed. We determined that the dynamic capacity of the expanded bed media is related to flow rate (measured in column volumes per hour) by a power function, which allows a high capacity at a low flow rate. At 250 cm h-1 with a 25 cm bed height (10 column volumes h-1), the dynamic capacity is 30 g l-1. The yield and purity (measured by the amount of host cell proteins, DNA, SDS-PAGE, and turbidity) of the antibody purified by expanded bed is comparable to the yield and purity obtained on a standard packed bed method using Prosep A media.     

Sequence of the mglB gene from Escherichia coli K12: comparison of wild-type and mutant galactose chemoreceptors

Summary The mglB gene of Escherichia coli codes for a galactose-binding protein (GBP) that serves both as the galactose chemoreceptor and as the recognition component of the -methylgalactoside transport system. The mglB551 mutation eliminates the chemotactic function of GBP without altering its transport or substrate-binding properties. To investigate the interaction between GBP and Trg, the chemotactic signal transducer for galactose, we sequenced the mglB genes from wild-type and mglB551 mutant strains. The mutation causes the replacement of Gly₇₄ of GBP by Asp. This residue is located in alpha-Helix III at the tip of the P domain in the GBP tertiary structure farthest removed from the substrate-binding cleft between the P and Q domains. We conclude that Helix III must be part of, or at least adjacent to, the recognition site for Trg. Our sequence also included part of the mglA gene, which is immediately distal to mglB. The amino acid sequence deduced for the beginning of the MglA protein showed homology with a family of polypeptides that contain an ATP-binding site and are components of binding-protein-dependent transport systems.     

Synthesis and biochemical studies of analogs of platelet-activating factor bearing a methyl group at C2 of the glycerol backbone

Two platelet-activating factor (PAF) analogs containing a methyl group at C2 of the glycerol moiety were synthesized, and some of their biochemical properties were investigated. 1-O-Hexadecyl-2-C,O-dimethyl-rac-glycero-3-phosphocholine (2-methyl-2-methoxy PAF) was prepared in a synthetic scheme beginning with the etherification of 2-methylpropen-1-ol. A reaction sequence involving hydroxylation, tritylation, alkylation, and detritylation afforded 1-O-hexadecyl-2-C,O-dimethyl-rac-glycerol, which was converted into the phosphocholine. A 2-lyso derivative of this PAF analog (2-methyl-lyso PAF) was synthesized from 1-O-hexadecyl-2-C-methyl-3-O-trityl-rac-glycerol. Benzylation followed by detritylation gave 1-O-hexadecyl-2-C-methyl-2-O-benzyl-rac-glycerol, which was converted into the phosphocholine compound. Hydrogenolysis afforded 1-O-hexadecyl-2-C-methyl-rac-glycero-3-phospholine (2-methyl-lyso PAF). The 2-methyl-lyso PAF analog served as a substrate for the acetyl-CoA-dependent acetyltransferase that acetylates 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine. However, 2-methyl-lyso PAF did not have a significant effect on the activities of a CoA-independent transacylase or of the acetylhydrolase that inactivates PAF, and thus does not appear to be a substrate or an inhibitor, respectively, for these enzymes. In addition, this analog exhibited only one-half of the antitumor activity of rac-1-O-alkyl-2-methoxy-rac-glycero-3-phosphocholine in human leukemic (HL-60) cells, and elicited no hypotensive response in rats and no platelet-activating activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Na,K-ATPase function in alternating electric fields.

Alternating currents affect ion transport processes and ATP splitting through changes in the activation of the membrane Na,K-ATPase. Both processes vary with the frequency, and the effective range includes the environmental 60 Hz. ATP splitting by Na,K-ATPase suspensions decreases for the enzyme under normal conditions, with the maximum effect at 100 Hz. ATP splitting increases when the enzyme activity is lowered to less than half its optimal value by changes in temperature, ouabain concentration, etc. These observations can be explained by the effects of the ionic currents on ion binding at the enzyme activation sites. Such a mechanism could account for the effects of electromagnetic fields on cells, as the transmembrane enzyme can convey the effect of an extracellular signal into the cell via ionic fluxes, and the measured threshold field is within the range of reported biological effects.     

Estimation of secretory rates of hormones from the specific activities of metabolites which have multiple secreted precursors

The calculation of rates of entry of material into an open system of multiple pools in the steady state from the specific activities of end products, which may be derived from several pools, is described. This analysis may be applied to estimate the rates of secretion of steroid hormones from the specific activities of urinary metabolites which may have various hormones as common precursors. In a previous publication (Gurpideet al., 1963) formulae have been presented by which secretory rates could be calculated after a single injection of the tracers assuming that each of the urinary metabolites was uniquely derived from one of the pools in the system. In the present article similar formulae were derived without this assumption. Consequently, it is shown that, under certain circumstances, non-uniquely derived metabolites can be used to estimate secretory rates, and that it may be unnecessary to consider the pathways of conversion of the hormones to the metabolites or the sites where these conversion occur.     

Chemical composition and larvicidal activity of essential oils of three Artemisia species

Aedes aegypti L. (Diptera: Culicidae) is a vector for serious diseases in tropical regions. This pest is mainly controlled by commercial larvicides but the application of such products has led to environmental problems. Essential oils (EO) have been consistently reported as molecules with insecticidal activity and can be used to produce more environmentally friendly larvicides in the control of A. aegypti. In this study, the larvicidal effect of essential oils (EO) from the leaves of three Artemisia species was evaluated against A. aegypti. The oils were obtained from steam distillation and their chemical composition was determined by gas chromatography–mass spectrometry. The EO of Artemisia camphorata was the most active in the screening bioassay and presented LC₅₀ and LC₉₅ of 64.95 and 74.18 μg ml⁻¹, respectively. In addition, we found that germacrene D-4-ol was the constituent responsible for the toxicity of this EO. Artemisia camphorata EO and its major constituent, germacrene D-4-ol, are promising for the development of natural larvicides against A. aegypti.