Acid hydrolysis procedure

We have taken advantage of the hydrolytic activity of these phage proteins for the preparation of series of saccharides of various size. Such large saccharides cannot otherwise be produced by synthetic methods or commonly used partial acid hydrolysis procedures. 

Ruiz, R. and Ehrman, T. (1996), Dilute acid hydrolysis procedure for determination of total sugars in the liquid fraction of process samples, in Laboratory Analytic Procedure LAP-014, National Renewable Energy Laboratory, Golden, CO. 

The choice of the analyte actually measured varies with the xenobiotic substance to which the subject has been exposed. Therefore, it is convenient to divide xenobiotic analysis on the basis of the type of chemical species determined. The most straightforward analyte is, of course, the xenobiotic itself. This applies to elemental xenobiotics, especially metals, which are almost always determined in the elemental form. In a few cases, organic xenobiotics can also be determined as the parent compound. However, organic xenobiotics are commonly determined as Phase 1 and Phase II reaction products. Often, the Phase I reaction product is measured, frequently after it is hydrolyzed from the Phase II conjugate, using enzymes or acid hydrolysis procedures. Thus, for example, trans,trans-mucomc acid... 

In order to determine the composition of the alk-1-enyl moieties, it is necessary to liberate the aldehydes quantitatively from the plasmalogens and this is usually achieved simply by treatment with acid. The perfect method for the release of aldehydes has yet to be devised, and Anderson et at. [44] have critically examined some of the acidic hydrolysis procedures that have been described and recommend the following ... 

They can be separated into three groups on layers of silica gel G impregnated with 2% boric acid, i.e. saturated dihydroxy-, unsaturated dihydroxy (with a trans double bond in position 4) and trihydroxy bases, with chloroform-hexane-methanol (5 5 2 by volume) as the mobile phase [465]. When acidic hydrolysis procedures are utilised in the preparation of the bases, unnatural threo- somers of the unsaturated dihydroxy bases are found just below the natural erythro compounds on the TLC plate. Each of the fractions separated by TLC can be recovered from the adsorbent by elution with chloroform-methanol (2 1, v/v), but the eluate should be washed with one quarter the volume of water to remove boric acid which is also eluted. If need be, the bases can be further resolved by silver ion TLC [462] or by HPLC in the reversed-phase mode (reviewed elsewhere [168]). It is possible that HPLC in the adsorption or silver ion modes could also contribute to the problem of analysis, but these do not appear to have been tried. 

Double Polarization. The Clerget double polarization method is a procedure that attempts to account for the presence of interfering optically active compounds. Two polarizations are obtained a direct polarization, followed by acid hydrolysis and a second polarization. The rotation of substances other than sucrose remains constant, and the change in polarization is the result of inversion (hydrolysis) of the sucrose. 

This can be achieved by an indirect method. The lithio derivative is first reacted with a borate ester. Sequential acid hydrolysis and oxidation yields the corresponding hydroxy derivative. This procedure is illustrated by the conversion of 2-lithiobenzo[6]thiophene to 2-hydroxybenzo[6]thiophene, which exists predominantly in the 2(3//)-one tautomeric form (200) <70JCS(C)1926). 

Cleavage of the chiral auxiliary is effected in a three-step procedure commencing with quatemization of the nitrogen with methyl fluorosulfonate, methyl trlfluoromethanesulfonate, or trimethyloxonium tetrafluoroborate. Reduction of the corresponding iminium salt 19 with NaBH4 and acidic hydrolysis of the resulting product affords substituted aldehyde 5 without epimerization of either stereocenter. 

In agreement with the results of Cattelain, further methylation of the 3-methylmercapto derivative (96) results practically exclusively in 2-methyl-3-methylmercapto-5-oxo-2,5-dihydro-l,2,4-triazine (97). Further methylation of 5-methylmercapto derivative (90) yields 2-methyl-5-methylmercapto-3-oxo-2,3-dihydro-l,2,4-triazine (100). Their structure was confirmed by acid hydrolysis leading to 2-methyl-3,5-dioxo derivatives (62), As was already mentioned, this reaction is a suitable general procedure for preparing the 1-alkyl derivatives of 6-azauracil. ... 

Acid Hydrolysis of Kasugamycinic Acid (9a) with 6N Hydrochloric Acid. d-Inositol (103 mg., 0.57 mmole) was obtained from the treatment of kasugamycinic acid (515 mg., 1.29 mmoles) with 6N hydrochloric acid followed by the similar procedure as described in the case of acid hydrolysis of kasugamycin. 

The procedure is modified for the reaction of preformed cyanohydrins with chiral amines39. I11 a further variation, Schiff bases of aliphatic aldehydes with optically active 1-arylalkyl-amines are transformed with liquid hydrogen cyanide to the corresponding a-aminonitrilcs, which, after acid hydrolysis, give the /V-aryUilkylamino acids. Hydrogenation then yields the a-amino acids40 41. 

The formation of 1-aminopyridinium chloride has been accomplished by the acid hydrolysis of N- ( -acetaminobenzene-sulfonimido)pyridine.4 Also, the rearrangement of a substituted diazepine has been observed to give a 1-aminopyridine derivative.5 The present procedure is an adaptation of that described by GosI and Meuwsen.1... 

Ethyl o-nitrophenylpyruvate and o-nitrophenylpyruvic acid 14-21 have been prepared by condensation of o-nitrotoluene with diethyl oxalate in the presence of potassium ethoxide,4 14 sodium ethoxide,16-20 or sodium methoxide.21 Sodium ethoxide is less reactive, however, and cannot be substituted successfully for potassium ethoxide in the present procedure, as it gives a very poor yield and poor quality of precipitated sodium salt. With sodium ethoxide the reaction does not appear to go to completion even under the conditions of refluxing ethanol usually employed,16-21 which are considerably more severe than the room temperature conditions employed with potassium ethoxide in the present procedure. o-Nitrophenylpyruvic add has also been prepared by hydrochloric acid hydrolysis of o-nitro-a-acetamino-dnnamic azlactone.4... 

Fraction Fla was chosen for structural purposes due to its better solubility in water and the absence of Xyl. In order to remove noncovalently associated protein, fraction Flap was submitted to sequential shaking cycles with a mixture of chloroform-buthanol, as indicated by Sevag and described by Staub [17]. The fraction was also treated with trichloroacetic acid. In both procedures, coprecipitation of carbohydrate and protein was observed, suggesting strong linkages and a more complex structure. Fla as was submitted to mild acid hydrolysis yielding Flas and Flap (Table VI). 

As noted above, the presence of Met(O) in proteins would go undetected after acid hydrolysis and subsequent amino acid analysis. Thus, since this method of hydrolysis is most commonly used, it is impossible to ascertain from the literature the abundance of Met(O) residues normally present in proteins. However, a number of studies have reported the presence of Met(O) residues in various proteins using one of the appropriate procedures described above. It has been found that Met(O) residues comprise 30% of the total Met in proteins isolated from bovine glomerular basement membranes and anterior lens . Other investigators have reported that the levels of Met(O) in proteins of the trabecular meshwork of human eyes increased with the age of the donor . The amount of Met(O) detected ranged from 15% (10 years old) to 55% (79 years old) of the total methionine content found in the tissue samples. Other studies have shown that in certain species of clams the proteins of the hinge ligament contain only Met(0) residues and no Met . In addition, it has also been reported that as much as 18% of the Met residues in pea seed proteins is in the form of Met(O) . Lastly, Met(O) residues have been found in... 

The concept of extractive reaction, which was conceived over 40 years ago, has connections with acid hydrolysis of pentosans in an aqueous medium to give furfural, which readily polymerizes in the presence of an acid. The use of a water-immiscible solvent, such as tetralin allows the labile furfural to be extracted and thus prevents polymerization, increases the yield, and improves the recovery procedures. In the recent past an interesting and useful method has been suggested by Rivalier et al. (1995) for acid-catalysed dehydration of hexoses to 5-hydroxy methyl furfural. Here, a new solid-liquid-liquid extractor reactor has been suggested with zeolites in protonic form like H-Y-faujasite, H-mordenite, H-beta, and H-ZSM-5, in suspension in the aqueous phase and with simultaneous extraction of the intermediate product with a solvent, like methyl Aobutyl ketone, circulating countercurrently. 

The GC-MS techniques give much more chemical information than does measurement of only 8-OH-dGua. However, the hydrolysis and derivatization procedures are lengthy and tedious, and may destroy some modified bases, e.g. hydroxymethyluracil (Djuric etal., 1991). It has also been speculated that they might create artefacts, e.g. if the amounts of modified bases increase during the preparation procedures. Data surest that formic acid hydrolysis does not create additional 8-OH-Gua in DNA (Halliwell and Dizdaroglu, 1992) but the question is currently open as to whether the derivatization procedures might do so. 

ISO standard 10398 provides methods for the identification of accelerators in cured and uncured compounds. Two methods are included. One is a GC method based on detection of trifluoroacetamide derivatives of the amines formed from acid hydrolysis. The second is a TLC procedure. 

---