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91.
We have developed a rapid and sensitive thin film assay for in-process monitoring of target protein purification. This novel biosensor method provides rapid (5-min) visual evaluation of column purification fractions. The method can be used to monitor the efficiency of purification and potential loss of protein if the column binding capacity is exceeded. The eluted fractions containing the highest yield of target protein can be quickly identified, pooled, and processed. This convenient platform, known as the SILAS product, is a thin-film detection technology in which specific molecular interactions are transduced into visible color changes based on changes in the optical thickness of layers on a silicon surface. The results are interpreted without instrumentation. Proteins eluted from a purification column are adsorbed to the assay surface, and the ligand of interest (target) can be identified with specific binding reagents. Here we demonstrate two protein purification applications for the SILAS technology product: monitoring antibody elution from a Protein G column and evaluating the efficiency of purification of a glutathione-S-transferase (GST)-tagged recombinant protein through each step of the purification process. 相似文献
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Aquifex aeolicus 3-deoxy-D-manno-octulosonate 8-phosphate synthase (KDO8PS) catalyzes the condensation of arabinose 5-phosphate (A5P) and phosphoenolpyruvate (PEP) by favoring the activation of a water molecule coordinated to the active-site metal ion. Cys11, His185, Glu222 and Asp233 are the other metal ligands. Wild-type KDO8PS is purified with Zn(2+) or Fe(2+) in the active site, but maximal activity in vitro is achieved when the endogenous metal is replaced with Cd(2+). The H185G enzyme retains 8% of the wild-type activity. ICP mass spectrometry analysis indicates that loss of His185 decreases the enzyme affinity for Fe(2+), but not for Zn(2+). However, maximal activity is again achieved by substitution of the endogenous metal with Cd(2+). We have determined the X-ray structures of the Cd(2+) H185G enzyme in its substrate-free form, and in complex with PEP, and PEP plus A5P. These structures show a normal amount of Cd(2+) bound, suggesting that coordination by His185 is not essential to retain Cd(2+) in the active site. Nonetheless, there are significant changes in the coordination sphere of Cd(2+) with respect to the wild-type enzyme, as the carboxylate moiety of PEP binds directly to the metal ion and replaces water and His185 as ligands. These observations indicate that the primary function of His185 in A.aeolicus KDO8PS is to orient PEP in the active site of the enzyme in such a way that a water molecule on the sinister (si) side of PEP can be activated by direct coordination to the metal ion. 相似文献
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Howes KA Pennesi ME Sokal I Church-Kopish J Schmidt B Margolis D Frederick JM Rieke F Palczewski K Wu SM Detwiler PB Baehr W 《The EMBO journal》2002,21(7):1545-1554
Visual transduction in retinal photoreceptors operates through a dynamic interplay of two second messengers, Ca(2+) and cGMP. Ca(2+) regulates the activity of guanylate cyclase (GC) and the synthesis of cGMP by acting on a GC-activating protein (GCAP). While this action is critical for rapid termination of the light response, the GCAP responsible has not been identified. To test if GCAP1, one of two GCAPs present in mouse rods, supports the generation of normal flash responses, transgenic mice were generated that express only GCAP1 under the control of the endogenous promoter. Paired flash responses revealed a correlation between the degree of recovery of the rod a-wave and expression levels of GCAP1. In single cell recordings, the majority of the rods generated flash responses that were indistinguishable from wild type. These results demonstrate that GCAP1 at near normal levels supports the generation of wild-type flash responses in the absence of GCAP2. 相似文献
95.
Melkonian G Munoz N Chung J Tong C Marr R Talbot P 《The Journal of experimental zoology》2002,292(3):241-254
The chick chorioallantoic membrane (CAM) is a valuable model for evaluating angiogenesis and vasculogenesis. Our purpose was to characterize the formation of the CAM vasculature, in particular the capillary plexus, between days five and six after fertilization and to examine the mode of action of cytochalasin D and suramin on vascular development during this interval. The CAM increased 20-fold in size between days five and six, during which time the capillary plexus forms by both migration of mesodermal blood vessels toward the ectoderm and by the formation of new vessels from angioblasts near the ectoderm. Between days five and six, the CAM becomes thinner, and the density of the mesodermal cells decreases. To determine the mode of action of anti-angiogenic drugs on the day five to day six CAM, various concentrations of cytochalasin D or suramin were added directly to day five CAMs, and their effects were evaluated on day six. Both drugs significantly inhibited CAM growth, altered branching patterns of the major vessels, decreased area of the major vessels, and inhibited the formation of the capillary plexus by inhibiting both vasculogenesis and the migration of mesodermal blood vessels to the ectoderm. Cytochalasin D also inhibited compartmentalization of the plexus. Cytochalasin D and suramin were inhibitory at similar doses. This study provides new information on early CAM development, establishes the mode of action and dose dependency of cytochalasin D and suramin on day five to day six CAMs, and demonstrates that the day five to day six CAM provides a useful assay to examine the effect of anti-angiogenic drugs on blood vessel development, including capillary plexus formation. 相似文献
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The numbers of brood cells in nests built by founding swarms of the Neotropical social wasp Polybia occidentalis closely correlate with the numbers of wasps in the swarms. We analyzed nests of different sizes to determine how they scale with respect to the allocation of brood cells among combs. Three patterns were evident: compared to smaller nests, larger nests have (1) more combs and (2) larger combs; and (3) among nests containing the same number of combs, the last two combs diverge in relative size as nest size increases. Taken together, these results suggest that members of a swarm somehow "know" the size of the swarm they are in. This information feeds back to individual builders, which quantitatively modulate their responses to stigmergic cues in ways that result in the nest-size-scaled allocation of brood cells among combs. The patterns also suggest that swarms fine-tune the final size of their nests by making corrections as they build. 相似文献