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71.
Scott Pownall Christine A. Kozak Keith Schappert Mohan Sarkar Eric Hull Harry Schachter Jamey D. Marth 《Genomics》1992,12(4)
The biosynthesis of protein-bound complex N-glycans in mammals requires a series of covalent modifications governed by a large number of specific glycosyltransferases and glycosidases. The addition of oligosaccharide to an asparagine residue on a nascent polypeptide chain begins in the endoplasmic reticulum. Oligosaccharide processing continues in the Golgi apparatus to produce a diversity of glycan structures. UDP-N-acetylglucosamine:α-3-
-mannoside β-1,2-N-acetylglucosaminyltransferase I (EC 2.4.1.101; GlcNAc-TI) is a key enzyme in the process because it is essential for the conversion of high-mannose N-glycans to complex and hybrid N-glycans. We have isolated the mouse gene encoding GlcNAc-TI (Mgat-1) from a genomic DNA library. The mouse sequence is highly conserved with respect to the human and rabbit homologs and exists as a single protein-encoding exon. Mgat-1 was mapped to mouse Chromosome 11, closely linked to the gene encoding interleukin-3 by the analysis of multilocus interspecies backcrosses. RNA analyses of Mgat-1 expression levels revealed significant variation among normal tissues and cells. 相似文献
72.
73.
Phosphorus availability under alley cropping and mulched and unmulched sole cropping systems in Costa Rica 总被引:3,自引:0,他引:3
Phosphorus availability was measured in soils under five cropping systems: alley cropping with Erythrina poeppigiana, alley cropping with Gliricidia sepium, sole cropping with Erythrina poeppigiana mulch applied, sole cropping with Gliricidia sepium mulch applied, sole cropping with no mulch. The following parameters were measured: 1) plant-available soil P assessed by P uptake of maize and bean bioassay plants; 2) phosphate desorbable by anion exchange resin; 3) adsorption of added P into isotopically exchangeable and non-exchangeable pools.In the bioassay, P uptake of beans declined in the order: mulched sole-cropped>unmulched sole-cropped>alley-cropped soils. For maize the relative uptake was: mulched sole-cropped>unmulched sole-cropped = alley-cropped soils. These results suggest trees had not incorporated a significant quantity of P into the system after seven years and, probably, there was a decrease in available soil P due to the sequestration of P in the tree biomass. Potentially resin-desorbable P was higher in alley-cropped and mulched sole-cropped soils than in unmulched sole-cropped soils. The adsorption and desorption of added P into and from exchangeable and non-exchangeable pools did not differ between alley-cropped and unmulched sole-cropped soils.Crop yield and crop N, P and K uptake were all higher in the alley crops than in the unmulched sole crop. The supply of P to the crop under alley cropping seems to be dependent on P cycled and released from the mulch. The P cycle in alley cropping appears to be self-sustaining at least under conditions of moderate P fertiliser input. 相似文献
74.
E Ong N R Gilkes R C Miller A J Warren D G Kilburn 《Enzyme and microbial technology》1991,13(1):59-65
Using molecular genetic techniques, a fusion protein has been produced which contains the cellulose-binding domain (CBD) of an exoglucanase (Cex) from Cellulomonas fimi fused to a beta-glucosidase (Abg) from Agrobacterium sp. The CBD functions as an affinity tag for the simultaneous purification and immobilization of the enzyme on cellulose. Binding to cellulose was stable for prolonged periods at temperatures from 4 degrees C to at least 50 degrees C, at ionic strengths from 10 mM to greater than 1 M, and at pH values below 8. The fusion protein can be desorbed from cellulose with distilled water or at pH greater than 8. Immobilized enzyme columns of the fusion protein bound to cotton fibers exhibited stable beta-glucosidase activity for at least 10 days of continuous operation at temperatures up to 37 degrees C. At higher temperatures, the bound enzyme lost activity. The thermal stability of the fusion protein was greatly improved by immobilization. Immobilization did not alter the pH stability. Except for its ability to bind to cellulose, the properties of the fusion protein were virtually the same as those of the native enzyme. 相似文献
75.
Lorilichus n. g. (Pterolichidae, Pterolichinae) is restricted to the Indo-Australian parrots of the family Loriidae. Assigned to this new genus are Pterolichus (Pseudalloptes) species described by Trouessart in 1884, namely, lobiger (type-species), delibativentris, discifer, cultriventris, emargiventris and securiventris. The first three named species are illustrated and two new species, parvifolius and grandifolius, are described: the five species are from Lorius domicellus (L.). 相似文献
76.
Summary Cuticle/water partition coefficients (Kc/w) for d-limonene, -pinene and -pinene were determined by an extrapolation and a desorption method. The sorption experiments were carried out with isolated angiosperm and gymnosperm cuticles and with [14C]-labelled monoterpenes, which were obtained biosynthetically. Both methods were suitable for the determination of the Kc/w of volatile hydrophobic compounds. For the angiosperm cuticles the partition coefficients are of the order of 104, which indicates a high accumulation of monoterpenes in the cuticle. The values of the conifer cuticles of Picea abies (L.) Karst. and Abies alba Mill., however, are lower due to their high lignin content. This is proved by the increase of the partition coefficients after removal of polar and phenolic components. The Kc/w can be estimated with good accuracy from the octanol/water partition coefficient, which was determined experimentally. 相似文献
77.
78.
The use of toluidine blue to stain cryosections of food samples to detect sites of microbial growth was examined. The method successfully detected colonies and single cells of both yeasts and bacteria at magnifications of x 400 or below in the majority of foods studied. The method demonstrates great potential for studying the micro-environments in which micro-organisms grow. 相似文献
79.
80.
Summary Applying a double-immunofluorescence technique, the porcine ovary is demonstrated to receive two populations of NPY-immunoreactive nerve fibres originating from the inferior mesenteric ganglion: one with colocalized tyrosine hydroxylase and supplying predominantly the ovarian vasculature, and a second, solely NPY-immunoreactive and almost exclusively associated with growing follicles. A third group of tyrosine hydroxylase-and dopamine--hydroxylase-positive, but NPY-negative nerve fibres is associated with ovarian blood vessels and, to a minor extent, with ovarian follicles. As revealed by retrograde tracing, the vast majority of postganglionic neurons projecting to the ovary is located in a discrete area of the ganglion, suggesting a somatotopic organization of the porcine inferior mesenteric ganglion. Moreover, the finding indicate that three subpopulations of postganglionic sympathetic neurons with different chemical codes supply different target components of the porcine ovary. The physiological relevance of the described neurons in the nervous control of ovarian functions remains to be elucidated.A portion of these results has been presented in abstract form (Majewski et al. 1991) 相似文献