The Monoamino Acids

Three of the amino acids, naniely, tyrosine, cystine and diaminotrioxy-dodecanic acid are characterised by their extremely slight solubility in neutral aqueous solutions. They are therefore easily obtained after hydrolysis by acids by neutralising and concentrating the solution, when they crystallise out. 

The separation of cystine and tyrosine as they are obtained by hydrolysis with hydrochloric acid was described by Morner in I901. The protein—hair, keratin from horn, eggshells, etc.—was boiled with five times its quantity of 13 per cent hydrochloric acid under a reflux condenser on a water bath for six to seven days. The solution was then decolorised with charcoal and evaporated in vacuo, and the residue dissolved in 60 to 70 per cent, alcohol. The two acids then crystallised out on neutralising with soda, and were separated by fractional crystallisation from ammonia if much tyrosine was present it separated out first, but if cystine exceeded tyrosine in quantity this compound crystallised out first the remainder was only separated with difficulty. Embden separated the mixture of the two acids by means of very dilute nitric acid, in which tyrosine is very easily soluble, but cystine with difficulty. Their separation may also be effected by precipitation with mercuric sulphate in 5 per cent, sulphuric acid solution in which the mercury compound of tyrosine is soluble (Hopkins and Cole). 

On account of the insolubility of these compounds and the difficulty of filtering and completely washing out the barium sulphate precipitate, in order to abstract from it the whole of the tyrosine, Abderhalden and Teruuchi, in the case of silk, have hydrolysed the protein with hydrochloric acid, the greater part of which was then removed by evaporation in vacuo the remainder of the hydrochloric acid was then estimated in a small aliquot portion, and then separated quantitatively by neutralising with the calculated amount of caustic soda. The tyrosine then crystallised out, and was purified by recrystallisation from water. 

A new method of determining the presence of tyrosine by bromina-tion was introduced by Horace Brown and employed by Adrian Brown and Millar in 1906 for estimating the rate at which tyrosine is split off from proteins by the action of trypsin. This method might be used for the estimation of tyrosine in proteins its non-employment may be due to the fact that tryptophane and also histidine react with bromine and might thus vitiate the result for tyrosine. 

For the preparation and estimation of the monoamino acids, hydrolysis by hydrochloric acid is more convenient than that by sulphuric acid. It was formerly carried out in the presence of stannous chloride (Hlasiwetz and Habermann) in order that the solution should remain colourless, instead of becoming dark brown, but this addition is not essential, as was shown by Cohn, and was not used by E. Fischer in his researches. Hydrolysis by hydrochloric acid is carried out by heating the protein with three times its quantity of concentrated hydrochloric acid 

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The separation and estimation of the two main groups of amino acids can be carried out in one experiment, instead of separately as described. The protein is hydrolysed by sulphuric acid, the tyrosine, cystine and diaminotrioxydodecanic acid are removed by crystallisation, and the diamino acids are precipitated by phosphotungstic acid. From this precipitate they are obtained by decomposition with baryta, and they are then separated by means of their silver compounds by Kossel, Kustcher and Patten s method. The filtrate from the phosphotungstic acid precipitate is freed from the excess of phosphotungstic acid by means of baryta, and the solution is treated by Fischer s ester method for the monoamino acids. 

The combination of the two processes is generally only carried out when the amount of protein available is limited they require very different quantities of material thus, the diamino acids can be determined in 25 to 50 grammes of protein with considerable accuracy, whereas the monoamino acids can only be determined with fair accuracy when 250 to 500 grammes of protein can be used. On the whole, it is not... 

The histones contain about 30 per cent, of diamino acids, and only in the case of thymus-histone has an estimation been made of the monoamino acids. They were supposed to be intermediate compounds between protamines and other proteins, and this supposition is confirmed by the results of analysis. 

The synthesis of the diamino acids, in comparison with that of the monoamino acids, is very much more difficult and has only been achieved within the last few years. 

It is clear from the results that the structure of wool is extremely complex. Almost all of the monoamino acids occur linked to both sides of glutamic and cysteic acids. The small number of aspartic acid peptides identified is probably due to the lower content of aspartic acid in wool so that the peptide spots would probably be faint and would not show on the chromatograms. 

The sodium and barium salts of the monoamino acids have a strongly alkaline reaction and are highly dissociated salts. If carbonic acid be passed into the solution of the barium salt, barium carbonate is not, as would be expected, immediately formed the solution remains clear, and only after a short time, when the solution becomes saturated with carbonic acid, does it become cloudy and barium carbonate gradually separates out the separation of barium carbonate is hastened by heating. This phenomenon is due, as was shown by Siegfried in 1905, to the formation of salts of carbamino acids of the general formula... 

As can be seen from Table VIII-3, satisfactory amounts (approximately 85 to 100 %) of peptides were recovered these included the sequences of all the monoamino-acids present among the arginine residues in clupeine Z. This indicates that each such sequence occurs once in a molecule. The following partial structure was given for clupeine Z ... 

Consequently, by placing a neutral solution of the protein hydrolyzate in the central compartment of a multicompartment cell, it can be expected that during electrolysis the monoamino acids will remain, in the central compartment owingto the fact that they exist in the form of dipolar ions dicarboxylic amino acids will migrate into the anode compartment and diamino acids into the cathode compartment. Electrodialysis or electrolytic fractionation of amino acids is based on this principle. 

Amino acids may be prepared by the action of a large excess of concentrated ammonia solution upon a-chloro- or a-bromo-acids the presence of a considerable amount of ammonium carbonate often increases the yield of monoamino acid, for example ... 

Both the monoamino and the diamino analogs of ascorbic acid exhibit powerful reducing properties, and the monoamino compound has a high antiscorbutic activity, probably due to the fact that it undergoes conversion to L-ascorbic acid in vivo by a process of deamination. 

Martin AJP, Synge RLM. A new form of chromatogram employing two liquid phases A theory of chromatography. 2. Application to the micro-determination of the higher monoamino-acids in proteins. Biochem. J. 1941 35 1358-1368. 

As the result of hydrolysis a complex mixture of all, or nearly all, the previously mentioned units is obtained. These have been isolated by various methods based upon the fractional crystallisation of the compounds themselves, or of their copper, silver and other salts. Only when one or more of the amino acids occurred in somewhat large amounts was their isolation and characterisation effected their amount seldom reached a value higher than 20 per cent, of the total quantity and the remainder was represented by uncrystallisable syrups of unknown nature. A great advance was made when Drechsel discovered that the protein molecule contained diamino acids as well as monoamino acids, and to Kossel and Kutscher we owe our chief knowledge concerning their isolation and estimation. Emil Fischer, in igoi, by his... 

The protamines are built up almost exclusively of diamino acids, salmine containing over 80 per cent, of arginine. Only small amounts of monoamino acids are present in them, and even these amounts may be due to impurity, for fish sperm only at maturity is made up of protamine and nucleic acid, whereas at other times histone takes the place of protamine, and histones contain less diamino acids. Kossel and Dakin s analysis appears to show us a quantitative result in the case of salmine. 

In the experiment above referred to, monoamino acids were used and... 

Biogenic amines in wine and fermented foods are formed primarily via the microbial decarboxylation of amino acids. Examples, such as histamine, tyramine, and phenylethylamine are toxic, especially in alcoholic beverages. Ethanol can inhibit the monoamino oxidase responsible for amine detoxification (Maynard and Schenker, 1996). Histamine can induce allergenic reactions in humans, such as rashes, edema, headaches, hypotension. Tyramine and phenylethylamine can cause hypertension and other symptoms related to the release of noradrenaline. 

Reaction between 3-amino-2-thiophenecarboxylic acid and R2GeCl2 with a deficiency of the L1NH2 gives the monoamino compounds 158 while an excess of lithium amide leads to formation of the diamino derivatives 159513 515-516 p(le authors suggest that intermolecular O — Ge coordination increases the lability of chlorine substituent in the intermediate 158 and favors the formation of the diamino derivatives 159510 513-515... 

The amine function served also as the starting point for the first covalent linkage of Pcs to single-walled carbon nanotubes (SWNTs) [94], The pipes with open-end and surface-bound acyl chloride moieties were used to prepare the Pc-SWNTs system by amide-bond formation (Fig. 14). Accordingly, statistical reaction of 4-aminophthalonitrile with 4-tcr/-bu(yIph111alonitrile in the presence of zinc ions delivered the monoamino Pc that was then employed in the conjugation with the acid chloride modified carbon nanotubes (CNTs). Here, it should also be mentioned that other functions have been applied to the covalent modification of CNTs, i.e., amide [95], ester [96,97], or click chemistry [98],... 

Spectra of many of the common amino acids not yet discussed are shown in Fig. 2, kindly made available by Sussman and Gratzer (1962). The data of this figure are usefully supplemented by the earlier but less extensive (2000-2300 A) observations of Saidel et al. (1952). In addition to some duplication of the amino acids of Fig. 2, Saidel et al. showed spectra of cysteic acid, hydroxyproline, asparagine, valine, isoleucine, and glycine. The monoamino, monocarboxylic amino acids, including the hydroxyamino acids and the imino acids, are seen to have very similar spectra at wave-... 

In addition to the effects of the proinflammatory immune response on serotonin metabolism, other neurotransmitter systems, in particular the catecholaminergic system, are involved in depression, too. Although the relationship of immune activation and the lack of catecholaminergic neurotransmission has not been well studied, the increase of the monoamino-oxidase (MAO) activity, which leads to decreased noradrenergic neurotransmission, might be an indirect effect of the increased production of kynurenine and quinolinic acid (Schiepers et al., 2005). 

These acids occupy an intermediate position between the monoamino-arylarsinic acids on the one hand and the di- and tri-aminoarylarsinic acids on the other, since the latter are the reduction products of the nitroamino compounds. Where the amino-group is not substituted, the acids have been prepared by four methods (1) By direct arsenation of nitroarylaniincs. (2) The aminoarylarsinic add is converted to its... 

Theory of Chromatography. II. Application to the Micro Determination of the Higher Monoamino Acids in Proteins. Biochem. J. 35,. 1358, (1941). 

This kind of ionized molecule, having coexistent negative and positive charges, is called a dipolar ion or ampholyte. At low pH, both the amino and carboxyl groups are protonated as —N H3 and —COOH, and the amino acid is cationic. As the pH rises, the carboxyl group loses its proton and the ampholyte form appears at about pH 6. At higher pH, the amino —N Hs is also deprotonated, and the molecule is anionic. The process is shown for a monoamino acid and monocarboxylic amino acid as follows ... 

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