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61.
The composition of coloured carotenoids in the milo shoot was investigated quantitatively (high performance liquid chromatography) during light-mediated plastidogenesis, including the time span of photodelay as caused by medium and high light fluxes. It was found that as long as only the far-red-absorbing form of phytochrome operates, the carotenoid pattern remains virtually the same as in complete darkness (violaxanthin and lutein as major constituents, traces of -carotene). On the other hand, the pattern changes dramatically in white or red light with increasing amounts of chlorophyll (lutein and -carotene dominate, -carotene showing the strongest relative increase). Photodelay during the early phase of plastidogenesis affects the carotenoid composition strongly. Increase of neoxanthin, violaxanthin and -carotene contents are diminished while lutein accumulation proves resistant towards chlorophyll-mediated photoinhibition. The photodelay can be diminished by an appropriate light pretreatment. The data indicate that light-mediated control over carotenoid accumulation is exerted at three levels: i) a coarse control through phytochrome, ii) fine tuning in connection with chlorophyll accumulation, iii) stabilization of holocomplexes against photodecomposition.Abbreviations GG14
high fluence rate green-yellow light
- HPLC
high-performance liquid chromatography
- Chl
chlorophyll
- WLw
weak white light (1200 lx)
- WLm
medium flux white light (12000 lx) 相似文献
62.
P release rates in five lakes were estimated from a mass balance approach and from laboratory tests. The influence of various environmental parameters on P release has been considered. The internal P loading can contribute phosphorus to overlying waters at levels comparable to the external sources (from 30 to 100%). When considering the recovery from eutrophication of the investigated lakes, the nutrient release from sediments is of critical importance. 相似文献
63.
Uridine Transport and Metabolism in the Central Nervous System 总被引:4,自引:2,他引:2
Reynold Spector 《Journal of neurochemistry》1985,45(5):1411-1418
Myelin and myelin-containing (P3) fractions were prepared from human white matter by discontinuous sucrose gradient centrifugation. The myelin isolated from each of the fractions of different densities was morphologically and biochemically distinct. Light myelin fractions consisted of compact, multilamellar myelin, whereas the denser fractions consisted predominantly of loose myelin with fewer lamellae. The amounts of both basic protein and lipophilin (proteolipid protein) were reduced in the denser fractions. In contrast, the high-molecular-weight components were elevated in the dense fractions. The lipid composition was similar in all the fractions studied. Analysis of basic protein by gel electrophoresis at pH 10.6 revealed differences in basic protein microheterogeneity among the fractions. The light myelin fraction was enriched in the more positively charged basic protein components (components 1, 2, and 3), whereas these components were reduced in the denser fractions. Myelin in the dense fractions was enriched in the more modified forms of basic protein (components 6, 7, and 8). The pattern of microheterogeneity was different for basic protein isolated from myelins of a 2-year-old and an adult brain; the former showed fewer components and mainly the most cationic species. On the other hand, the pattern of microheterogeneity of basic protein isolated from the different density gradient fractions was similar for both ages. 相似文献
64.
The effects of protein malnutrition on responsiveness of macrophages to proteosepeptone stimulation and on their chemical
composition were investigated. Relative number of resident macrophages in rat peritoneal cavity was reduced by about 50 %
during 4 weeks on 3 % protein diet. Similarly, decreased migration capacity of the circulating macrophages to the peritoneal
exudate in response to the stimulant, was observed in protein-fasted rat compared to that in the 20 % protein-fed group. Further,
the chemical composition of the isolated elicited cells was determined. Total proteins, sugars, lipids and nucleic acids were
significantly low in the cells isolated from protein-deficient animals, though the cell size was not affected. However, cholesterol:
phospholipid molar ratios were distinctly higher than that in control and increased progressively in the 3 and 8 % protein-fed
animals. The implications of these structural changes in macrophages on their functional capability are discussed 相似文献
65.
Abstract Glycine added to the growth medium of Caulobacter crescentus was found to substitute Cterminal alanine in the peptide side chains of the murein of this species. Murein synthesized in vivo and in vitro in the presence of glycerine was poorly crosslinked as was new murein formed in the presence of the amino acid. The reduced cross-linkage seems to be due to the effect of glycine on the formation of trimeric muropeptides as revealed by high-performance liquid chromatography (HPLC) muropeptide analysis of murein formed in the presence and absence of the amino acid. 相似文献
66.
Ben J. G. Flik 《Aquatic Ecology》1985,19(2):117-122
Production versus light response curves were made of natural phytoplankton assemblages during the year in an incubator at 8 different light intensities ranging from 60 to 1500 Einstein.m–2.sec–1. The shape of these curves is analyzed in relation to the sensitivity for photo-inhibition. At the end of the month of April, there is a sudden shift in this sensitivity at higher light intensities. The algal assemblage becomes less sensitive for photo-inhibition. The influence of light-adaptation, temperature, nutrient limitation and species composition is discussed. 相似文献
67.
用硫酸铵分段盐析及DEAE-Sephadex A-50、羟磷灰石和CM纤维素等多种柱层析方法,从正常小鼠肝浸液中分离纯化出一种免疫抑制蛋白质(LISP)。在体外用微量该蛋白质就能强烈抑制小鼠T、B淋巴细胞对促有丝分裂原和同种异型抗原的增生反应。纯化的蛋白质在聚丙烯酰胺凝胶电泳(PACE)和等电聚焦(IEF)鉴定时均显示为一条区带,其等电点(pI)值在7.5—7.8范围。沉降系数利S_(20),w为5.39。Sephadex G-100凝胶层析测得LISP的分子量为78,000道尔顿。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)提示LISP是由二个相同的亚基组成,亚基分子量为38,500道尔顿。LISP是一种既非糖蛋白又非脂蛋白的碱性蛋白质,对它的氨基酸组成也作了分析。 相似文献
68.
Summary A general method is presented for the formulation and numerical evaluation of mathematical models describing epithelial transport. The method is based on the principles of conservation of mass, and maintenance of electroneutrality within the cells and bathing solutions. It is therefore independent of the specific membrane transport mechanisms, and can be used to evaluate different models describing arbitrary transport processes (including passive, active and cotransport processes). Detailed numerical methods are presented that allow computation of steady-state and transient responses under open-circuit, current-clamp and voltage-clamp conditions, using a general-purpose laboratory minicomputer. To evaluate the utility of this approach, a specific model is presented that is consistent with the Koefoed-Johnson and Ussing hypothesis of sodium transport in tight epithelia (Acta Physiol. Scand.
42:298–308, 1958). This model considers passive transport of an arbitrary number of permeant solutes, active transport of sodium and potassium, and osmotically induced water transport across the apical and basolateral membranes. Results of the model are compared to published experimental measurements in rabbit urinary bladder epithelium. 相似文献
69.
用数学方法推导出了自交作物群体遗传组成的分析公式。根据所推出的公式,可以计算出任何自交世代群体的基因型频率和同一表现型中各基因型的频率。对自交群体遗传组成的分析可用于质量性状的选择,确定选择时需要的有效群体大小和选出有效群体的大小,亦有助于确定选择的最佳世代。 相似文献
70.
Cytochromec oxidase was isolated from human hearts and separated by SDS gel electrophoresis. The identity of polypeptide bands with known subunits was demonstrated by immunoblotting with monospecific antisera to rat liver cytochromec oxidase subunits. The polarographically determined kinetics of cytochromec oxidation were similar to those reported for the bovine heart enzyme. 相似文献