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41.
Nanoliter scale microbioreactor array for quantitative cell biology 总被引:14,自引:0,他引:14
A nanoliter scale microbioreactor array was designed for multiplexed quantitative cell biology. An addressable 8 x 8 array of three nanoliter chambers was demonstrated for observing the serum response of HeLa human cancer cells in 64 parallel cultures. The individual culture unit was designed with a "C" shaped ring that effectively decoupled the central cell growth regions from the outer fluid transport channels. The chamber layout mimics physiological tissue conditions by implementing an outer channel for convective "blood" flow that feeds cells through diffusion into the low shear "interstitial" space. The 2 microm opening at the base of the "C" ring established a differential fluidic resistance up to 3 orders of magnitude greater than the fluid transport channel within a single mold microfluidic device. Three-dimensional (3D) finite element simulation were used to predict fluid transport properties based on chamber dimensions and verified experimentally. The microbioreactor array provided a continuous flow culture environment with a Peclet number (0.02) and shear stress (0.01 Pa) that approximated in vivo tissue conditions without limiting mass transport (10 s nutrient turnover). This microfluidic design overcomes the major problems encountered in multiplexing nanoliter culture environments by enabling uniform cell loading, eliminating shear, and pressure stresses on cultured cells, providing stable control of fluidic addressing, and permitting continuous on-chip optical monitoring. 相似文献
42.
The topic addressed is that of combining self-constructing chemical systems with electronic computation to form unconventional embedded computation systems performing complex nano-scale chemical tasks autonomously. The hybrid route to complex programmable chemistry, and ultimately to artificial cells based on novel chemistry, requires a solution of the two-way massively parallel coupling problem between digital electronics and chemical systems. We present a chemical microprocessor technology and show how it can provide a generic programmable platform for complex molecular processing tasks in Field Programmable Chemistry, including steps towards the grand challenge of constructing the first electronic chemical cells. Field programmable chemistry employs a massively parallel field of electrodes, under the control of latched voltages, which are used to modulate chemical activity. We implement such a field programmable chemistry which links to chemistry in rather generic, two-phase microfluidic channel networks that are separated into weakly coupled domains. Electric fields, produced by the high-density array of electrodes embedded in the channel floors, are used to control the transport of chemicals across the hydrodynamic barriers separating domains. In the absence of electric fields, separate microfluidic domains are essentially independent with only slow diffusional interchange of chemicals. Electronic chemical cells, based on chemical microprocessors, exploit a spatially resolved sandwich structure in which the electronic and chemical systems are locally coupled through homogeneous fine-grained actuation and sensor networks and play symmetric and complementary roles. We describe how these systems are fabricated, experimentally test their basic functionality, simulate their potential (e.g. for feed forward digital electrophoretic (FFDE) separation) and outline the application to building electronic chemical cells. 相似文献
43.
Alim Dewan Jihye Kim Rebecca H. McLean Siva A. Vanapalli Muhammad Nazmul Karim 《Biotechnology and bioengineering》2012,109(12):2987-2996
We investigated growth kinetics of microalgae, Chlorella vulgaris, in immobilized arrays of nanoliter‐scale microfluidic drops. These static drop arrays enabled simultaneous monitoring of growth of single as well as multiple cells encapsulated in individual droplets. To monitor the growth, individual drop volumes were kept nearly intact for more than a month by controlling the permeation of water in and out of the microfluidic device. The kinetic growth parameters were quantified by counting the increase in the number of cells in each drop over time. In addition to determining the kinetic parameters, the cell‐size distribution of the microalgae was correlated with different stages of the growth. The single‐cell growth kinetics of C. vulgaris showed significant heterogeneity. The specific growth rate ranged from 0.55 to 1.52 day?1 for different single cells grown in the same microfluidic device. In comparison, the specific growth rate in bulk‐scale experiment was 1.12 day?1. It was found that the average cell size changes significantly at different stages of the cell growth. The mean cell‐size increased from 5.99 ± 1.08 to 7.33 ± 1.3 µm from exponential to stationary growth phase. In particular, when multiple cells are grown in individual drops, we find that in the stationary growth phase, the cell size increases with the age of cell suggesting enhanced accumulation of fatty acids in older cells. Biotechnol. Bioeng. 2012; 109: 2987–2996. © 2012 Wiley Periodicals, Inc. 相似文献
44.
Ayme-Southgate AJ Southgate RJ Philipp RA Sotka EE Kramp C 《Journal of molecular evolution》2008,67(6):653-669
All striated muscles respond to stretch by a delayed increase in tension. This physiological response, known as stretch activation,
is, however, predominantly found in vertebrate cardiac muscle and insect asynchronous flight muscles. Stretch activation relies
on an elastic third filament system composed of giant proteins known as titin in vertebrates or kettin and projectin in insects.
The projectin insect protein functions jointly as a “scaffold and ruler” system during myofibril assembly and as an elastic
protein during stretch activation. An evolutionary analysis of the projectin molecule could potentially provide insight into
how distinct protein regions may have evolved in response to different evolutionary constraints. We mined candidate genes
in representative insect species from Hemiptera to Diptera, from published and novel genome sequence data, and carried out
a detailed molecular and phylogenetic analysis. The general domain organization of projectin is highly conserved, as are the
protein sequences of its two repeated regions—the immunoglobulin type C and fibronectin type III domains. The conservation
in structure and sequence is consistent with the proposed function of projectin as a scaffold and ruler. In contrast, the
amino acid sequences of the elastic PEVK domains are noticeably divergent, although their length and overall unusual amino
acid makeup are conserved. These patterns suggest that the PEVK region working as an unstructured domain can still maintain
its dynamic, and even its three-dimensional, properties, without the need for strict amino acid conservation. Phylogenetic
analysis of the projectin proteins also supports a reclassification of the Hymenoptera in relation to Diptera and Coleoptera.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
45.
The demographic costs of nectar production in the desert perennial Prosopis glandulosa (Mimosoideae): a modular approach 总被引:1,自引:0,他引:1
Golubov Jordan Mandujano María C. Montaña Carlos López-Portillo Jorge Eguiarte Luis E. 《Plant Ecology》2004,170(2):267-275
Nectar production in angiosperms is considered to represent a reproductive cost, and has been associated with a decrease in
fruit set or an overall decrease in the energetic budget of the plant. Populations of Prosopis glandulosa var. torreyana (honey mesquite) are a suitable system to evaluate the demographic costs of nectar production, as populations are composed
of a 1:1 proportion of nectarful to nectarless individuals. The study was carried out in a population of 404 individuals of
Prosopis g1andulosa var. torreyana found in an area with differing water availability in the Southern Chihuahuan Desert. The possible costs of nectar production
were assessed on 1212 shoots of the honey mesquite that were tagged in 1994 and followed until 1998. We used two methods of
analysis to describe the effect of nectar production on modular population dynamics: matrix analysis and log-xlinear models.
Water availability and the varying environmental conditions affected plant growth, but nectar production did not have an effect
on the demographic parameters we measured. The values of λ did not differ between nectar morphs and the only important effects
we detected were the year to year variation in precipitation and microclimate differences at each site. Furthermore, the elasticity
of each demographic process (growth, fecundity, retrogression and stasis) between nectar morphs did not differ. The log-linear
models suggested a similar pattern but could discriminate the importance of each factor (nectar morph, year and site) on module
fate. We were not able to detect a demographic cost of nectar production in the honey mesquite. The absence of a demographic
response could be due to the negligible cost of producing nectar for this species or that the resources allocated for growth
are different from those allocated for reproduction. Our results suggest that the modular fates of mesquites are mainly determined
by environmental factors.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Siobhán S. Wills Colin L. Raston Keith A. Stubbs 《Bioorganic & medicinal chemistry letters》2018,28(23-24):3748-3751
A simple synthesis, which utilizes a thin film microfluidic reactor for a problematic step, of a potent inhibitor of α-N-acetylhexosaminidases, DGJNAc, has been developed. 相似文献