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The chemical nature of the apical droplet from eggs of Culex pipiens was investigated by chromatographic techniques. Results indicated that the hydrolysate of the apical drop contains C-12, C-14, C-16, and C-18 straightchain aliphatic fatty acids. A C-12β-hydroxy fatty acid was also found, but the largest component of the fatty acid mixture of the apical drop was shown to be a C-14β-OH fatty acid. Two other fractions appear to be unsaturated fatty acids, probably C-12 and C-14. Quantitative estimation of the percentage of each fatty acid in the mixture showed that about 85 per cent of the fatty acid content of the apical drop consisted of hydroxy fatty acids. By thin-layer chromatography, the largest component coincided with β-OH myristic acid.Glycerol was confirmed to be present in the hydrolysate. Feeding studies with radioactive 32PO4?3 and 35SO4?2 showed no significant incorporation of phosphorus, but a sulphur-containing anionic compound could be detected in the apical drop. Infrared analysis showed the presence of an ester group, double bond, primary and secondary alcohol groups, suggesting the presence of hydroxy-, unsaturated-, saturated straight-chain fatty acids, as well as mono-and diglycerides. The structural evidence explains in part the surfactant properties of the apical drop. 相似文献
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Courtney P. Leisner Asaph B. Cousins Sascha Offermann Thomas W. Okita Gerald E. Edwards 《Photosynthesis research》2010,106(3):201-214
Recent research on the photosynthetic mechanisms of plant species in the Chenopodiaceae family revealed that three species,
including Bienertia sinuspersici, can carry out C4 photosynthesis within individual photosynthetic cells, through the development of two cytoplasmic domains having dimorphic
chloroplasts. These unusual single-cell C4 species grow in semi-arid saline conditions and have semi-terete succulent leaves. The effects of salinity on growth and
photosynthesis of B. sinuspersici were studied. The results show that NaCl is not required for development of the single-cell C4 system. There is a large enhancement of growth in culture with 50–200 mM NaCl, while there is severe inhibition at 400 mM NaCl.
With increasing salinity, the carbon isotope values (δ13C) of leaves increased from −17.3o/oo (C4-like) without NaCl to −14.6o/oo (C4) with 200 mM NaCl, possibly due to increased capture of CO2 from the C4 cycle by Rubisco and reduced leakiness. Compared to growth without NaCl, leaves of plants grown under saline conditions were
much larger (~2 fold) and more succulent, and the leaf solute levels increased up to ~2000 mmol kg solvent−1. Photosynthesis on an incident leaf area basis (CO2 saturated rates, and carboxylation efficiency under limiting CO2) and stomatal conductance declined with increasing salinity. On a leaf area basis, there was some decline in Rubisco content
with increasing salinity up to 200 mM NaCl, but there was a marked increase in the levels of pyruvate, Pi dikinase, and phosphoenolpyruvate
carboxylase (possibly in response to sensitivity of these enzymes and C4 cycle function to increasing salinity). The decline in photosynthesis on a leaf area basis was compensated for on a per leaf
basis, up to 200 mM NaCl, by the increase in leaf size. The influence of salinity on plant development and the C4 system in Bienertia is discussed. 相似文献
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Background
Adhesion and successful colonization of bacteria onto solid surfaces play a key role in biofilm formation. The initial adhesion and the colonization of bacteria may differ between the various types of surfaces found in oral cavity. Therefore, it is conceivable that diverse biofilms are developed on those various surfaces. The aim of the study was to investigate the molecular modifications occurring during in vitro biofilm development of Streptococcus mutans UA159 on several different dental surfaces. 相似文献49.
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