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991.
Min Zhang George R. Miesegaes Michael Lee Daniel Coleman Bin Yang Melody Trexler‐Schmidt Lenore Norling Philip Lester Kurt A. Brorson Qi Chen 《Biotechnology and bioengineering》2014,111(1):95-103
Protein A chromatography is widely used as a capture step in monoclonal antibody (mAb) purification processes. Antibodies and Fc fusion proteins can be efficiently purified from the majority of other complex components in harvested cell culture fluid (HCCF). Protein A chromatography is also capable of removing modest levels of viruses and is often validated for viral clearance. Historical data mining of Genentech and FDA/CDER databases systematically evaluated the removal of model viruses by Protein A chromatography. First, we found that for each model virus, removal by Protein A chromatography varies significantly across mAbs, while remains consistent within a specific mAb product, even across the acceptable ranges of the process parameters. In addition, our analysis revealed a correlation between retrovirus and parvovirus removal, with retrovirus data generally possessing a greater clearance factor. Finally, we describe a multivariate approach used to evaluate process parameter impacts on viral clearance, based on the levels of retrovirus‐like particles (RVLP) present among process characterization study samples. It was shown that RVLP removal by Protein A is robust, that is, parameter effects were not observed across the ranges tested. Robustness of RVLP removal by Protein A also correlates with that for other model viruses such as X‐MuLV, MMV, and SV40. The data supports that evaluating RVLP removal using process characterization study samples can establish multivariate acceptable ranges for virus removal by the protein A step for QbD. By measuring RVLP instead of a model retrovirus, it may alleviate some of the technical and economic challenges associated with performing large, design‐of‐experiment (DoE)—type virus spiking studies. This approach could also serve to provide useful insight when designing strategies to ensure viral safety in the manufacturing of a biopharmaceutical product. Biotechnol. Bioeng. 2014;111: 95–103. © 2013 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc. 相似文献
992.
Ephrin-mediated restriction of ERK1/2 activity delimits the number of pigment cells in the Ciona CNS
Nicolas Haupaix Philip B. Abitua Cathy Sirour Hitoyoshi Yasuo Michael Levine Clare Hudson 《Developmental biology》2014
Recent evidence suggests that ascidian pigment cells are related to neural crest-derived melanocytes of vertebrates. Using live-imaging, we determine a revised cell lineage of the pigment cells in Ciona intestinalis embryos. The neural precursors undergo successive rounds of anterior–posterior (A–P) oriented cell divisions, starting at the blastula 64-cell stage. A previously unrecognized fourth A–P oriented cell division in the pigment cell lineage leads to the generation of the post-mitotic pigment cell precursors. We provide evidence that MEK/ERK signals are required for pigment cell specification until approximately 30 min after the final cell division has taken place. Following each of the four A–P oriented cell divisions, ERK1/2 is differentially activated in the posterior sister cells, into which the pigment cell lineage segregates. Eph/ephrin signals are critical during the third A–P oriented cell division to spatially restrict ERK1/2 activation to the posterior daughter cell. Targeted inhibition of Eph/ephrin signals results in, at neurula stages, anterior expansion of both ERK1/2 activation and a pigment cell lineage marker and subsequently, at larval stages, supernumerary pigment cells. We discuss the implications of these findings with respect to the evolution of the vertebrate neural crest. 相似文献
993.
Christine E. Cooper Philip C. Withers 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2010,180(6):857-868
Quolls (Dasyurus) are medium-sized carnivorous dasyurid marsupials. Tiger (3,840 g) and eastern quolls (780 g) are mesic zone species, northern
quolls (516 g) are tropical zone, and chuditch (1,385 g) were once widespread through the Australian arid zone. We found that
standard physiological variables of these quolls are consistent with allometric expectations for marsupials. Nevertheless,
inter-specific patterns amongst the quolls are consistent with their different environments. The lower T
b of northern quolls (34°C) may provide scope for adaptive hyperthermia in the tropics, and they use torpor for energy/water
conservation, whereas the larger mesic species (eastern and tiger quolls) do not appear to. Thermolability varied from little
in eastern (0.035°C °C−1) and tiger quolls (0.051°C oC−1) to substantial in northern quolls (0.100°C oC−1) and chuditch (0.146°C oC−1), reflecting body mass and environment. Basal metabolic rate was higher for eastern quolls (0.662 ± 0.033 ml O2 g−1 h−1), presumably reflecting their naturally cool environment. Respiratory ventilation closely matched metabolic demand, except
at high ambient temperatures where quolls hyperventilated to facilitate evaporative heat loss; tiger and eastern quolls also
salivated. A higher evaporative water loss for eastern quolls (1.43 ± 0.212 mg H2O g−1 h−1) presumably reflects their more mesic distribution. The point of relative water economy was low for tiger (−1.3°C), eastern
(−12.5°C) and northern (+3.3) quolls, and highest for the chuditch (+22.6°C). We suggest that these differences in water economy
reflect lower expired air temperatures and hence lower respiratory evaporative water loss for the arid-zone chuditch relative
to tropical and mesic quolls. 相似文献
994.
Tsubasa Fukue Motohide Tamura Ryo Kandori Nobuhiko Kusakabe James H. Hough Jeremy Bailey Douglas C. B. Whittet Philip W. Lucas Yasushi Nakajima Jun Hashimoto 《Origins of life and evolution of the biosphere》2010,40(3):335-346
We present a wide-field (∼6′ × 6′) and deep near-infrared (K
s
band: 2.14 μm) circular polarization image in the Orion nebula, where massive stars and many low-mass stars are forming.
Our results reveal that a high circular polarization region is spatially extended (∼0.4 pc) around the massive star-forming
region, the BN/KL nebula. However, other regions, including the linearly polarized Orion bar, show no significant circular
polarization. Most of the low-mass young stars do not show detectable extended structure in either linear or circular polarization,
in contrast to the BN/KL nebula. If our solar system formed in a massive star-forming region and was irradiated by net circularly
polarized radiation, then enantiomeric excesses could have been induced, through asymmetric photochemistry, in the parent
bodies of the meteorites and subsequently delivered to Earth. These could then have played a role in the development of biological
homochirality on Earth. 相似文献
995.
The most common cystic fibrosis (CF)‐causing mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) is deletion of Phe508 (ΔF508) in the first of two nucleotide‐binding domains (NBDs). Nucleotide binding and hydrolysis at the NBDs and phosphorylation of the regulatory (R) region are required for gating of CFTR chloride channel activity. We report NMR studies of wild‐type and ΔF508 murine CFTR NBD1 with the C‐terminal regulatory extension (RE), which contains residues of the R region. Interactions of the wild‐type NBD1 core with the phosphoregulatory regions, the regulatory insertion (RI) and RE, are disrupted upon phosphorylation, exposing a potential binding site for the first coupling helix of the N‐terminal intracellular domain (ICD). Phosphorylation of ΔF508 NBD1 does not as effectively disrupt interactions with the phosphoregulatory regions, which, along with other structural differences, leads to decreased binding of the first coupling helix. These results provide a structural basis by which phosphorylation of CFTR may affect the channel gating of full‐length CFTR and expand our understanding of the molecular basis of the ΔF508 defect. 相似文献
996.
Anotida Madzvamuse Eamonn A. Gaffney Philip K. Maini 《Journal of mathematical biology》2010,61(1):133-164
By using asymptotic theory, we generalise the Turing diffusively-driven instability conditions for reaction-diffusion systems
with slow, isotropic domain growth. There are two fundamental biological differences between the Turing conditions on fixed
and growing domains, namely: (i) we need not enforce cross nor pure kinetic conditions and (ii) the restriction to activator-inhibitor kinetics to induce pattern formation on a growing biological system is no longer a requirement. Our theoretical findings
are confirmed and reinforced by numerical simulations for the special cases of isotropic linear, exponential and logistic
growth profiles. In particular we illustrate an example of a reaction-diffusion system which cannot exhibit a diffusively-driven
instability on a fixed domain but is unstable in the presence of slow growth. 相似文献
997.
Adak AK Leonov AP Ding N Thundimadathil J Kularatne S Low PS Wei A 《Bioconjugate chemistry》2010,21(11):2065-2075
Bishydrazides are versatile linkers for attaching glycans to substrates for lectin binding and pathogen detection schemes. The α,ω-bishydrazides of carboxymethylated hexa(ethylene glycol) (4) can be conjugated at one end to unprotected oligosaccharides, then attached onto carrier proteins, tethered onto activated carboxyl-terminated surfaces, or functionalized with a photoactive cross-linking agent for lithographic patterning. Glycoconjugates of bishydrazide 4 can also be converted into dithiocarbamates (DTCs) by treatment with CS(2) under mild conditions, for attachment onto gold substrates. The immobilized glycans serve as recognition elements for cell-surface lectins and enable the detection and capture of bacterial pathogens such as Pseudomonas aeruginosa by their adsorption onto micropatterned substrates. A detection limit of 103 cfu/mL is demonstrated, using a recently introduced method based on optical pattern recognition. 相似文献
998.
999.
Gheorghe Benga Bogdan E. Chapman Guy C. Cox Philip W. Kuchel 《Cell biology international》2010,34(7):703-708
As part of a programme of comparative measurements of P d (diffusional water permeability) the RBCs (red blood cells) from an aquatic monotreme, platypus (Ornithorhynchus anatinus), and an aquatic reptile, saltwater crocodile (Crocodylus porosus) were studied. The mean diameter of platypus RBCs was estimated by light microscopy and found to be ~6.3 μm. P d was measured by using an Mn2+‐doping 1H NMR (nuclear magnetic resonance) technique. The P d (cm/s) values were relatively low: ~2.1×10?3 at 25°C, 2.5×10?3 at 30°C, 3.4×10?3 at 37°C and 4.5 at 42°C for the platypus RBCs and ~2.8×10?3 at 25°C, 3.2×10?3 at 30°C, 4.5×10?3 at 37°C and 5.7×10?3 at 42°C for the crocodile RBCs. In parallel with the low water permeability, the E a,d (activation energy of water diffusion) was relatively high, ~35 kJ/mol. These results suggest that “conventional” WCPs (water channel proteins), or AQPs (aquaporins), are probably absent from the plasma membranes of RBCs from both the platypus and the saltwater crocodile. 相似文献
1000.
Sampat Ingale Johannes S. Gach Michael B. Zwick Philip E. Dawson 《Journal of peptide science》2010,16(12):716-722
The membrane proximal external region (MPER) of gp41 abuts the viral membrane at the base of HIV‐1 envelope glycoprotein spikes. The MPER is highly conserved and is rich in Trp and other lipophilic residues. The MPER is also required for the infection of host cells by HIV‐1 and is the target of the broadly neutralizing antibodies, 4E10, 2F5, and Z13e1. These neutralizing antibodies are valuable tools for understanding relevant conformations of the MPER and for studying HIV‐1 neutralization, but multiple approaches used to elicit MPER binding antibodies with similar neutralization properties have failed. Here we report our efforts to mimic the MPER using linear as well as constrained peptides. Unnatural amino acids were also introduced into the core epitope of 4E10 to probe requirements of antibody binding. Peptide analogs with C‐terminal Api or Aib residues designed to be helical transmembrane (TM) domain surrogates exhibit enhanced binding to the 4E10 and Z13e1 antibodies. However, we find that placement of constrained amino acids at nonbinding sites within the core epitope significantly reduce binding. These results are relevant to an understanding of native MPER structure on HIV‐1, and form a basis for a chemical synthesis approach to mimic MPER stricture and to construct an MPER‐based vaccine. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd. 相似文献