Filtration centrifugation study

Although there is much evidence to suggest that the envelopes of photosyntheti-cally competent plastids are relatively impermeable to MVA, the origin of the MVA required for chloroplastidic terpenoid biosynthesis in plastids that are not able to fix CO2 is not yet certain. Studies using silicone-oil centrifugal filtration have shown that etioplasts and 1—2 h etiochloroplasts have envelopes that are permeable to acetate and MVA, but plastids from etiolated tissues that have been illuminated for periods of 4 h or longer show progressive impermeability to these precursors. 

Based upon the results of the factorial study, the manufacturing-scale centrifuge filtration time (6000 X scale) was reduced 73% from the simultaneous addition process developed in Option 2 above. 

While DLS can be a useful tool for investigating very polydispersed systems, it must be applied for that purpose with caution. Due to the much stronger scattering power of larger particles, the smaller particles cannot often be detected. On the other hand, with DLS one can obtain very precise information on the tail of the distribution for large particles. A useful approach is to study polydispersed samples by fractionation (e.g. by centrifugation, filtration, chromatography, etc.) and then to analyse the individual fractions by SLS or DLS (17, 25). 

Theoretical studies (30) comparing the abihty to dewater compressible sohds by sedimenting and filtering centrifuges to pressure filters, have shown that at high G levels, scroU decanters produce drier cakes than pressure filtration. 

Significant effort has been devoted to the development of separation methods for the post-BDS stage. Simple approach employing two phase separation methods like filtration or use of centrifugal forces have been studied as well as newer approaches including modification of biocatalyst to facilitate separation have been studied. Information has been obtained from patents as well as publications in open literature. 

The partition coefficient is determined by measuring the surfactant concentration in the dissolved and particulate phases when the steady state has been reached. The separation of the two phases is performed by either filtration or centrifugation. There have been many studies to characterise the sorption of surfactants onto minerals and textiles [8,25,26], but relatively few have characterised sorption into environmental compartments [2,3,15,17,19,20,27,28], particularly for marine environments [14]. 

After dissociation of the 70 S ribosome into its two subunits followed by zonal centrifugation for the separation and isolation of the 30 S and 50 S subunits on a preparative scale, the ribosomal proteins were extracted by acetic acid and then separated by cellulose ion exchange chromatography and by gel filtration on Sephadex in the presence of 6 M urea. In this way all the 53 individual ribosomal proteins have been isolated (Wittmann, 1974). Proteins prepared in this manner have been used for physical studies (Brimacombe et al., 1978 Wittmann, 1982) as well as for immunological investigations (Stoffler et al., 1980 Lake,... 

Extraction of cultured G. toxicus. To prepare the harvested dinoflagellate cells (about 1 x 10 cells) for shipment from Hawaii to South Carolina, absolute methanol was added to effect a final concentration of approximately 25 (v/v). Upon receipt of the culture, additional methanol was added to attain a final concentration of 80% (v/v). After extraction at room temperature for J days, the suspension was clarified by centrifugation. The supernatant was dried and the resultant solids were weighed and resuspended in absolute methanol. The suspension was filtered and the filtrate designated as the crude dinoflagellate extract used in this study. Subsequent fractionation of this extract by HPLC (Higerd et al., manuscript in preparation) showed that the material responsible for toxicity eluted in a fraction well removed from the fraction that exhibited toxicity when extracts of either Pacific moray eel or Caribbean fish were chromatographed. In all cases, the body temperature depression effect was evident only in those fractions which also exhibited toxicity. 

A number of techniques have been used for the preparative separation of flavonoids. These include HPLC, Diaion, Amberlite XAD-2 and XAD-7, and Fractogel TSK/Toyopearl HW-40 resins, gel filtration on Sephadex, and centrifugal partition chromatography (CPC). The choice of methods and strategies varies from research group to research group and depends often on the class of flavonoid studied. 

Hydrogel samples were taken at various intervals. The liquid phase for composition studies was separated by centrifugation, and the solid phase was separated by filtration and washing until the pH of the filtrate fell below 11. Part of the sample was heated to carry out crystallization, and the compositions of liquid and solid phases were determined. 

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