Ureas extraction

In the last one and one-half decades many studies have been made on the ORD and CD of ribosomal proteins. Early studies (McPhie and Grat-zer, 1966 Sarkar et al., 1967 Cotter and Gratzer, 1969) were made on a mixture of proteins, and the general conclusion was that both in the ribosome and in the isolated state (usually after acetic acid and urea extraction) the protein moiety contained approximately 25% a helix together with some -pleated sheet and random-coil conformation. 

PMR studies have been performed on a number of other ribosomal proteins isolated by the acetic acid/urea method (Morrison etal., 1977a). The results of these studies have shown that acedc acid/urea-extracted proteins contain little tertiary structure. However, some structure was seen in protein S4 and especially in protein S16 as indicated by the appearance of ring-current shifted resonances in the apolar region of the spectrum (Morrison et al., 1977b). These are due to the interaction of apolar methyl groups with aromatic amino acids in the tertiary structure of the protein. The PMR spectra were recorded either in water or in dilute phosphate buffer at pH 7.0—conditions under which the proteins were soluble. 

Budowle (,30) reported that urea extraction of bloodstains was necessary or mistypings of Gc could occur. Further, as Gc is dissociated from actin, there is more free Gc for the subsequent assay. 

L. N. Goldsbrough, A Pilot Plant Employing a Novel Process for the Urea Extraction of Hydrocarbons, Proceedings of the 4th World Petroleum Congress, vol. V, Section IIIB, Paper 6, pp. 141-153 (1955). 

Hasselbach and Schneider (1951) Rabbit 28 38 52 14 20 (16 after urea extraction)... 

The character of the solutions of epidermal proteins in urea varies in the following way. Where the whole mucosum is dispersed in 6 M urea an opaque solution is obtained after several hours and this is comparatively viscous. The viscosity rapidly falls and is very low after 24 hours. Under similar conditions 6 M urea in 1 Af KCl solution yields a clear solution which is markedly more viscous and this viscosity falls much less rapidly than in urea alone. On dialyzing the urea extracts against KCl or water a marked difference in precipitation occurs. The bulk of the protein in the urea/KCl extract rapidly precipitates, that in the urea only remains in solution for a much longer time. It is not intended to describe these differences any further at present, but merely to indicate that the effect of KCl in the extraction medium appears to retard the dissolution of the protein complexes, which proceeds more rapidly and probably to a greater extent in urea without salt. 

The striking feature of Table II is the comparatively high sulfur content of the nonfibrous protein and this tends to increase as we pass from the inner to the outer layers of the mucosum. It is of course possible to read many things into these results, but interpretation should be postponed until the measurements are extensively repeated. The values for the middle and inner levels do support observations made during the purification procedures that in these levels it was more difficult to dissociate the complex present in the primary solution. Whether this dissociation is a mild hydrolysis which occurs during urea extraction, or even an enzyme action during dialysis, are suggestions which yet have to be examined. 

It is then dissolved in water and barium carbonate is added. The salt is decomposed, and barium nitrate, carbon dioxide, and urea are formed. The solution is finally evaporated to dryness and the urea extracted with hot alcohol. 

Apart from the concentrafion of sericin, its extraction method has been shown to influence cell viability, also. If compared to heat, acid, or alkaline extraction methods, urea-extracted silk sericin is linked to the lowest cell viability of L929 mouse fibroblast (Aramwit et al., 2010). Sericin can also be used to replace bovine semm in cell freezing media. It cryopreserves cells as effectively as standard freeze medium containing foetal bovine serum. This effect has been demonstrated for various cell lines including P3U1 myeloma cell line, Chinese hamster ovary CHO cells, human dermal fibroblasts, human epidermal keratinocytes, the rat phaeochromocytoma cell line PC 12 and Sf9 insect cells (Sasaki et al., 2005), human primary hepatocytes (Miyamoto et al., 2010), rat pancreatic... 

Table 2.8 New major FT-IR bands in polyether urethane urea extracts ...

To the first class belong systems such as alkanoic acids, methylnicotinate, salicylic acid and urea extracted by liquid hydrocarbons or big esters such as isopropyl-tetradecanate (isopropyl-myristate (IPM)). 

Russell A E, Shuttleworth S G, Williams-Wynn D A 1967 Further studies on the mechanism of vegetable tannage. Part II. Effect of urea extraction on hydro-thermal stability of leather tanned with a range of organic tanning agents. J Soc Leather Trades Chem 51(6) 222-230... 

Preparation 0 Urea bom Urine.—(a) As Urea Nitrate.—When normal human urine is treated with an equal volume of concentrated nitric acid crystals of urea nitrate may begin to separate out within an hour. Many specimens of urine, however, yield no precipitate even after twenty-four hours. This is not always due, as might be expected, to a lower concentration of urea in the urine, but depends on the presence of a colloid that inhibits precipitation. An aqueous solution of urea of the same concentration as that in urine (2 per cent.) gives a dense precipitate of urea nitrate within five minutes after addition of an equal voliune of nitric acid, if the liquid be kept cool. Consequently, in preparing urea nitrate from its natural source, the urine must be concentrated to about a quarter of its original volume by evaporation on a water bath. An equal volume of pure nitric acid is added to the cold concentrate, and after twenty minutes the crystalline precipitate of urea nitrate is filtered off, neutralised with barium carbonate suspension, evaporated to dryness on a water bath, and the urea extracted by hot alcohol. 

The present study demonstrated that urea transport across gut epithelia is directly proportional to the blood concentration of urea in lactating dairy cows i.e. in the short term the extraction ratio upon passage of the epithelial bed is unaffected by increased blood urea concentration. The epithelial permeability for urea was markedly affected by the ration offered and the extraction ratio of urea was up-regulated with LOW-N at the level of the rumen and the whole PDV. However, the relative increase in extraction was greatest for the rumen. The data obtained in the present study implies that the curvilinear relationship observed between blood urea concentration and PDV urea extraction in lactating dairy cows is caused by adaptation of the epithelial urea transport to the nutritional state of the cow and not an artifact of a transport system for urea running at a constant rate (i.e. not zero-order regulation). 

C8H10N4O2. An alkaloid occurring in tea, coffee and guarana, from which it may be prepared by extraction, It is also manufactured by the methylation of theobromine and by the condensation of cyanoacetic acid with urea. Crystallizes with H2O or anhydrous from organic solvents. M.p. (anhydrous) 235"C, sublimes at 176 C. Odourless, and with a very bitter taste. Caffeine acts as a stimulant and diuretic, and is a constituent of cola drinks, tea and coffee. 

Ammonium cyanate, because of its instability in solution, is usually prepared (NHJaSO, + 2KCNO 2NH4CNO + KjSO by mixing aqueous solutions of ammonium sulphate and potassium cyanate. Complete evaporation then gives a mixture of potassium sulphate and urea, from which the urea may be extracted w ith hot absolute ethanol, in which potassium sulphate is insoluble. 

R NHa + C.HjNCO = RNH CO NHC,Hj Traces of water will contaminate the product with diphenylurea (p. 336) if the solution is boiled hence the need for anhydrous conditions. i-Naphthylisocyanate reacts more slowly with water, and the i-naphthyl-urea derivative can often be obtained using a cold aqueous solution of an aliphatic amine it is particularly necessary in such cases to purify the product by recrystallisation from, or extraction with, boiling petroleum, leaving behind any insoluble di i-naphthylurea. Note that the amine must also be free from alcohols (p. 335) and phenols (p. 337). 

In aqueous solution at 100° the change is reversible and equilibrium is reached when 95 per cent, of the ammonium cyanate has changed into urea. Urea is less soluble in water than is ammonium sulphate, hence if the solution is evaporated, urea commences to separate, the equilibrium is disturbed, more ammonium cyanate is converted into urea to maintain the equilibrium and evfflitually the change into urea becomes almost complete. The urea is isolated from the residue by extraction with boiling methyl or ethyl alcohol. The mechanism of the reaction which is generally accepted involves the dissociation of the ammonium cyanate into ammonia and cyanic acid, and the addition of ammonia to the latter ... 

Urea oxalate is also sparingly soluble in amyl alcohol and since urea is soluble in this alcohol, the property may be utilised in separating urea from mixtures. An aqueous extract of the mixture is rendered slightly alkaline with sodium hydroxide solution and extracted with ether this removes all the basic components, but not urea. The residual aqueous solution is extracted with amyl alcohol (to remove the urea) upon adding this extract to a solution of oxalic acid in amyl alcohol crystalline urea oxalate is precipitated. 

Uses. The principal use of adiponitrile is for hydrogenation to hexamethylene diamine leading to nylon-6,6. However, as a result of BASE s new adiponitrile-to-caprolactam process, a significant fraction of ADN produced may find its way into nylon-6 production. Adipoquanamine, which is prepared by the reaction of adiponitrile with dicyandiamide [461-58-5] (cyanoguanidine), may have uses in melamine—urea amino resins (qv) (see "Benzonitrile, Uses"). Its typical Hquid nitrile properties suggest its use as an extractant for aromatic hydrocarbons. 

Various techniques have been proposed for the recovery of pure succinic acid, including extraction (141—145), selective crystalliza tion (146—151), heating to dehydrate the acid and subsequent recovery of succinic anhydride by distillation (152), esterification foUowed by fractionation of the mixture of the esters (65—69), and separation as urea adduct (118,119). 

The elemental and vitamin compositions of some representative yeasts are Hsted in Table 1. The principal carbon and energy sources for yeasts are carbohydrates (usually sugars), alcohols, and organic acids, as weU as a few other specific hydrocarbons. Nitrogen is usually suppHed as ammonia, urea, amino acids or oligopeptides. The main essential mineral elements are phosphoms (suppHed as phosphoric acid), and potassium, with smaller amounts of magnesium and trace amounts of copper, zinc, and iron. These requirements are characteristic of all yeasts. The vitamin requirements, however, differ among species. Eor laboratory and many industrial cultures, a commercial yeast extract contains all the required nutrients (see also Mineral nutrients). 

Separation Techniques. Current methods for separating fatty acids are by solvent crystaUi2ation or by the hydrophili2ation process. Other methods that have been used in the past, or perhaps could be used in the future, are panning and pressing, solvent extraction, supercritical fluid extraction, the use of metal salts in assisting in separation, separations using urea complexes, and adsorption/desorption. 

Urea Enzymatic Dialysis Method. This method (16) uses 8 M urea [57-13-6] to gelatinize and facUitate removal of starch and promote extraction of the soluble fiber at mild (50°C) temperatures. EoUowing digestion with heat-stable a-amylase and protease, IDE is isolated by filtration or I DE is obtained after ethanol precipitation. Values for I DE are comparable to those obtained by the methods described eadier, and this method is less time-consuming than are the two AO AC-approved methods. Corrections for protein are required as in the AO AC methods. 

Bromophenyl isothiocyanate [1985-12-2] M 214.1, m 56-58 . Recryst from boiling n-hexane. Any insoluble material is most probably the corresponding urea. It can be purified by steam distn, cool the receiver, add NaCl and extract in Et20, wash extract with N H2SO4 dry (MgS04), evaporate and recrystallise the residual solid. [Org Synth Coll Vol IV 700 7965 Coll Vol 1447 1941.]... 

Hydrocortisone Crude hydrocortisone bissemicarbazone (50 g) is dissolved at 20° in 2.5 liters of 2.4 N hydrochloric acid under a nitrogen atmosphere. The solution is cooled to 5°, and then a solution of 25 g of sodium nitrite in 250 ml of water is added over a 15 min period, the temperature being maintained at 5 + 1°. The reaction mixture is stirred for an additional 30 min at 5°, then treated with a solution of 150 g of urea in 250 ml of water over a 15 min period and finally neutralized below 15° with 20% sodium hydroxide. The mixture is extracted several times with chloroform and the solvent is evaporated under reduced pressure to give 33 g of crude hydrocortisone, mp 197-203°. Crystallization from acetone-Darco gives 26.4 g (69.5%) of pure hydrocortisone mp 216-221° [oc]d 151° (Diox). 

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