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191.
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193.
On the origins of esterases 总被引:8,自引:0,他引:8
Comparisons among the primary sequences of five cloned eukaryotic esterases
reveal two distinct lineages, neither bearing any significant overall
sequence similarity to the functionally related serine protease multigene
family. We have not eliminated the possibility that the esterases may have
residual conformational similarities to the serine proteases. However, our
profile analysis and analyses of the predicted conformations of the
esterases reveal little similarity to the serine proteases. Four of the
esterase proteins share 27%-53% overall sequence similarity and evidence of
a catalytic mechanism involving the same Arg- Asp-Ser or His-Asp-Ser charge
relay. We propose that these four esterases, three of them cholinesterases,
form part of a multigene family essentially separate from the serine
proteases.
相似文献
194.
195.
M. A. Fadel W. A. Khalil H. H. Hassanin 《International journal of biological macromolecules》1986,8(6):375-379
The effects of fast and albedo neutrons and alpha particles on the molecular fractions of cellulose nitrate type CA 80, as a tissue equivalent material have been measured through the use of gel permeation chromatography. The samples in the form of thin sheets were exposed to fission neutron fluences in the range 105–1010 n/cm2 and to different energies of alpha particles in the range 1–5 MeV. The effects of irradiation on paraffin phantom, application of lithium borate radiator to the sample and storage of irradiated specimens for different periods were measured. The results indicated that CA80 eluted in one main fraction. Irradiation with neutrons or alpha particles caused fragmentation of this fraction to smaller molecules. Small and acceptable fade of the induced changes by radiation in the polymer due to storage for more than one month were noticed. The possibility of applying this technique in radiation dosimetry was discussed. 相似文献
196.
Nicholas JG Webster Lui-Guojing Evans Matt Caples Laura Erker Shern L Chew 《BMC molecular biology》2004,5(1):7-15
Background
Incorporation of exon 11 of the insulin receptor gene is both developmentally and hormonally-regulated. Previously, we have shown the presence of enhancer and silencer elements that modulate the incorporation of the small 36-nucleotide exon. In this study, we investigated the role of inherent splice site strength in the alternative splicing decision and whether recognition of the splice sites is the major determinant of exon incorporation. 相似文献197.
198.
P. H. Robinson M. Campbell Mathews J. G. Fadel 《Animal Feed Science and Technology》1999,80(3-4):257-266
The effect of within-day delays of 0.5, 2.5, 4.5 and 6.5 h between collection of rumen fluid from a cow and initiation of in vitro fermentation, as well as storage of rumen fluid for 48 h at either −24°C or 6, 22 and 39°C, on in vitro digestion of neutral detergent fibre (NDF) at 48 h was determined. In addition, the 48 h in vitro digestion of NDF, determined with a minimum time delay (i.e., 0.5 h) between collection from the cow and initiation of incubation, was compared to NDF digestion determined in sacco at 48 h. Rumen inoculum from a single cow was utilized in a thrice replicated incubation with whole crop alfalfa, corn, cereal and sudangrass forages of a lower and higher quality. The same cow was used as the host for the in sacco bags. The in vitro procedure used a bulk procedure with 5.0 cm × 5.5 cm multi-weave polyethylene polyester polymer bags that retained particles of 25 mm and larger. The in sacco procedure used the same bags retained in a large mesh bag. A within-day time delay of up to 6.5 h between collection of rumen fluid from the cow and initiation of in vitro fermentation had no impact on measured 48 h in vitro digestion of NDF. In contrast, no temperature dependent storage procedure maintained 48 h in vitro digestion of NDF at levels determined with no 48 h storage, although high quality alfalfa was least affected by any storage procedure. The 48 h in vitro digestion of NDF, determined using the minimum time delay between collection from the cow and initiation of the incubation, was higher than values obtained in sacco. Results show that this bulk in vitro procedure resulted in higher 48 h digestion of NDF than those determined with a similar in sacco procedure, thereby suggesting that laboratories located some distance from the donor animal can utilize in vitro procedures to accurately estimate 48 h digestion of NDF. However, storage of rumen fluid for 48 h, by any temperature dependent procedure examined, in order to facilitate fewer trips to the donor animal, or trips of substantially longer duration, will underestimate 48 h digestion of NDF to an extent that depends upon the forage incubated. 相似文献
199.