Hydrolysates molecular weights

Mintz GR, Reinhart GM, Lent B. Relationship between collagen hydrolysate molecular weight and peptide substantivity to hair. J Soc Cosmet Chem 1991 42 35-44. 

The excess of unchanged acetic anhydride is then hydrolysed by the addition of water, and the total free acetic acid estimated by titration with standard NaOH solution. Simultaneously a control experiment is performed identical with the above except that the alcohol is omitted. The difference in the volumes of NaOH solution required in the two experiments is equivalent to the difference in the amount of acetic add formed, i.e., to the acetic acid used in the actual acetylation. If the molecular weight of the alcohol is known, the number of hydroxyl groups can then be calculated. 

The melting points of these esters are usually much lower than those of the corresponding 3 5 dinitrobenzoates their preparation, therefore, offers no advantages over the latter except for alcohols of high molecular weight and for polyhydroxy compounds. The reagent is, however, cheaper than 3 5 dinitrobenzoyl chloride it hydrolyses in the air so that it should either be stored under light petroleum or be prepared from the acid, when required, by the thionyl chloride or phosphorus pentachloride method. 

The rate of hydrolysis depends upon the solubUity of the acetal m the hydrolysis medium. Acetals of low molecular weight are completely hydrolysed by refluxing for 5-10 minutes those of higher molecular weight, and therefore of small solubility, may require 30-60 minutes, but... 

Hydrolyzed Vegetable Protein. To modify functional properties, vegetable proteins such as those derived from soybean and other oil seeds can be hydrolyzed by acids or enzymes to yield hydrolyzed vegetable proteins (HVP). Hydrolysis of peptide bonds by acids or proteolytic enzymes yields lower molecular weight products useful as food flavorings. However, the protein functionaHties of these hydrolysates may be reduced over those of untreated protein. 

The hydrolyses of ADP and ATP were tried in the presence of low-molecular-weight analogs of polyethylenimine, i e. ethylenediamine, 77 (ED), diethylenetriamine, 78 (DT), triethylenetetramine, 79 (TT), tetraethylenepentamine, 80 (TP) and pentaethylenehexamine129). These compounds accelerated the reaction several times. The degree of the acceleration increased with increasing degree of polymerization. 

Kabanov et al.131) found that a copolymer of 4-vinylpyridine and acroleinoxime, 82 (PPox), is a powerful catalyst for the hydrolyses of PNPA, NABA, and 3-nitro-4-trimethyl-acetoxybenzoic acid 83 (NTBA). The activity of the copolymer was 103 times higher than that of the low-molecular-weight oxime, iso-butyraldoxime. They proposed the cooperative activation of the oxime- and pyridine-groups in the vicinity of pyridinium cation groups of the copolymer. 

For apple maceration, the main activity is the endopectinlyase (PL) which decreases the viscosity due to the colloidal pectin by decreasing tlie molecular weight of this substrate methylated at about 90%. In association to this PL, exo B and endoarabanase (ARAs), pectinacetylesterase (PAE), rhamnogalacturonase (RG) and other hemicellulases allow to hydrolyse side chains of the pectin, decrease the steric hindrance and make the access of pectinases to the rhamnogalacturonic backbone more easy. 

Substituted amides suffer hydrolysis with greater difficulty. The choice of an acid or an alkaline medium vill depend upon (a) the solubility of the compound in the medium and (b) the effect of the reagent upon the products of hydrolysis. Substituted amides of comparatively low molecular weight (e.g., acetanilide) may be hydrolysed by boiling either with 10 per cent, sodium hydroxide solution or with 10 per cent, sulphuric acid for 2-3 hours. Other substituted amides are so insoluble in water that little reaction occurs when they are refluxed with dilute acid or dilute alkali for several hours. These include such substances as benzanilide (C(H(CONHC,Hg) and the benzoyl derivative of a naphthylamine (C.HjCONHCioH,) or a toluidine (C gCONHCjH,). For these substances satisfactory results may be obtained with 70 per cent, sulphuric acid this hydrolysis medium is a much better solvent for the substituted amide than is water or more dilute acid it also permits a higher reaction temperature (compare Section IV 192) ... 

Preparation and Reactions of S-b-MM. As mentioned in the introduction, we were interested in block copolymers of styrene and alkali metal methacrylates with overall molecular weights of about 20,000 and methacrylate contents on the order of 10 mol%. The preparation of such copolymers by the usual anionic techniques is not feasible. An alternative is to prepare block copolymers of styrene and methacrylic esters by sequential anionic polymerization, followed by a post-polymerization reaction to produce the desired block copolymers. The obvious first choice of methacrylic esters is methyl methacrylate. It is inexpensive, readily available, and its block copolymers with styrene are well-known. In fact, Brown and White have reported the preparation and hydrolyses of a series of S-b-MM copolymers of varying MM content using p-toluenesulfonic acid (TsOH) (6). The resulting methacrylic acid copolymers were easily converted to their sodium carboxylates by neutralization with sodium hydroxide. 

However, pyrolysis is rapid, avoids sample wet chemical workup, avoiding sample loss and contamination, and has a low sample requirement. It allows the determination, in a single step, of polymeric materials (with in situ hydrolysis of the hydrolysable polymers and thermal decomposition of the nonhydrolysable polymers) and low molecular weight components [16]. As a result, pyrolysis is a relatively fast and inexpensive technique, especially if compared with the classical wet analytical procedures that are required prior to GC/MS analyses. 

Acrylate and low-molecular-weight acrylic acids are effective slime depressants/disper-sants. Suspendol PKK and PC improved separation efficiency between zinc and iron oxides. Starches, mainly hydrolysed starch and cooked starch, are effective depressants in the treatment of oxidized zinc ores that contain iron oxides and Fe-hydroxides. 

Table X 4 summarizes similar data for the hydrolysis by maltase-free malt alpha amylase of beta dextrins obtained from arrowroot starch by the action of beta amylase. The beta dextrins were precipitated with alcohol from the reaction mixture of arrowroot starch after it had reached a limit in the hydrolysis at 60% theoretical maltose. The beta dextrins were hydrolyzed extensively by malt alpha amylase. Glucose was liberated in very small amounts even in the later stages of the hydrolysis of these beta dextrins maltose was liberated in appreciable amounts and, at equivalent hydrolyses, appeared to be formed somewhat more rapidly from the beta dextrins (Table X) than from the untreated starch (Table IX). Upon hydrolysis with malt alpha amylase the molecular weights of the beta dextrins dropped appreciably but not as extensively as when arrowroot starch was hydrolyzed directly by malt alpha amylase.

Fluids The silicone fluids are linear polymers which are having very low Molecular weight within the range 4000-25,000. These are mainly obtained from dimethyldichlorosilane which is continuously hydrolysed by mixing with dilute hydrochloric acid (20%). 

Figure 6.4. Mode of action of low-molecular-weight G-proteins. The raslike proteins normally bind GDP, but this may be exchanged for GTP via a process that may be assisted by guanine nucleotide exchange protein (GNEP). The GTP-bound ras protein may then interact with and activate its target protein (X). The activity of GTPase activating protein (GAP) may then assist to hydrolyse GTP to GDP, to inhibit ras activity.

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