Tryptophan solubility

This washing is to remove tyrosine, which is precipitated as a mercury compound somewhat more soluble than the tryptophane precipitate. The mercuric sulfate addition tends to reduce the tryptophane solubility. 

C, soluble in water and alcohol. It occurs in woad as the glucoside indican, and in mammalian urine, combined with sulphuric acid, as an ester, also called indican. It arises in the body from the bacterial decomposition of tryptophan. 

Water-soluble globular proteins usually have an interior composed almost entirely of non polar, hydrophobic amino acids such as phenylalanine, tryptophan, valine and leucine witl polar and charged amino acids such as lysine and arginine located on the surface of thi molecule. This packing of hydrophobic residues is a consequence of the hydrophobic effeci which is the most important factor that contributes to protein stability. The molecula basis for the hydrophobic effect continues to be the subject of some debate but is general considered to be entropic in origin. Moreover, it is the entropy change of the solvent that i... 

The conformation of bovine myelin basic protein (MBP) in AOT/isooctane/water reversed micellar systems was studied by Waks et al. 67). This MBP is an extrinsic water soluble protein which attains an extended conformation in aqueous solution 68 but is more density packed at the membrane surface. The solubilization of MBP in the AOT reversed micelles depends on the water/AOT-ratio w0 68). The maximum of solubilization was observed at a w0-value as low as 5.56. The same value was obtained for another major protein component of myelin, the Folch-Pi proteolipid 69). According to fluorescence emission spectra of MBP, accessibility of the single tryptophane residue seems to be decreased in AOT reversed micelles. From CD-spectra one can conclude that there is a higher conformational rigidity in reversed micelles and a more ordered aqueous environment. 

An expedient and stereoselective synthesis of bicyclic ketone 30 exemplifies the utility and elegance of Corey s new catalytic system (see Scheme 8). Reaction of the (R)-tryptophan-derived oxazaboro-lidine 42 (5 mol %), 5-(benzyloxymethyl)-l,3-cyclopentadiene 26, and 2-bromoacrolein (43) at -78 °C in methylene chloride gives, after eight hours, diastereomeric adducts 44 in a yield of 83 % (95 5 exo.endo diastereoselectivity 96 4 enantioselectivity for the exo isomer). After reaction, the /V-tosyltryptophan can be recovered for reuse. The basic premise is that oxazaborolidine 42 induces the Diels-Alder reaction between intermediates 26 and 43 to proceed through a transition state geometry that maximizes attractive donor-acceptor interactions. Coordination of the dienophile at the face of boron that is cis to the 3-indolylmethyl substituent is thus favored.19d f Treatment of the 95 5 mixture of exo/endo diastereo-mers with 5 mol % aqueous AgNC>3 selectively converts the minor, but more reactive, endo aldehyde diastereomer into water-soluble... 

The product of the hydroxylation of tryptophan, 5-hydroxytryptophan, is rapidly decarboxylated to 5-HT by a specific decarboxylase enzyme. This is generally thought to be a soluble enzyme which suggests that 5-HT is synthesised in the cytoplasm, before it is taken up into the storage vesicles. If this is the case, then considerable losses might be incurred from its metabolism by monoamine oxidase before it reaches the storage vesicles. Indeed, this could explain why 5-HT turnover seems to greatly exceed its rate of release. 

We also wanted to evaluate the disassembly of our dendritic system under physiological conditions. Thus, we synthesized a self-immolative AB6 dendron 32 with water-soluble tryptophan tail units and a phenylacetamide head as a trigger (Fig. 5.26) to evaluate disassembly in aqueous conditions. The phenylacetamide is selectively cleaved by the bacterial enzyme penicillin G amidase (PGA). The trigger was designed to disassemble through azaquinone methide rearrangement and cyclic dimethylurea elimination to release a phenol intermediate that will undergo six quinone methide elimination reactions to release the tryptophan tail units. 

The recrystallization of the crude tryptophane is an extremely troublesome process. Not only must a less soluble by-product be removed, but the mother liquors contain a more soluble, gummy impurity in considerable proportion. After collecting each crop, the mother liquor must be evaporated to a small volume on the steam bath and treated with a double volume of alcohol. This process is repeated until no further crystals are obtained, but only a gum. 

Tyrosine contains a phenolic side chain with a pKa of about 9.7-10.1. Due to its aromatic character, tyrosine is second only to tryptophan in contributing to a protein s overall absorptivity at 275-280nm. Although the amino acid is only sparingly soluble in water, the ionizable nature of the phenolic group makes it often appear in hydrophilic regions of a protein—usually... 

Wu and Sun have presented a versatile procedure for the liquid-phase synthesis of 1,2, ,4-tctrahydro-/i-carbolines [77]. After successful esterification of the MeO-PEG-OH utilized with Fmoc-protected tryptophan, one-pot cyclocondensations with various ketones and aldehydes were performed under microwave irradiation (Scheme 7.68). The desired products were released from the soluble support in good yields and high purity. The interest in this particular scaffold is due to the fact that the l,2,3,4-tetrahydro-/f-carboline pharmacophore is known to be an important structural element in several natural alkaloids, and that the template possesses multiple sites for combinatorial modifications. The microwave-assisted liquid-phase protocol furnished purer products than homogeneous protocols and product isolation/ purification was certainly simplified. 

Hamon, M., Bourgoin, S., Hery, F., Temaux, J. P., and Glowinski, J. (1976) In vivo and in vitro activation of soluble tryptophan hydroxylase from rat brainstem. Nature, 260 61-63. 

The method of protein hydrolysis was important acid hydrolysis caused destruction of tryptophan but alkaline treatment gave even greater losses of other amino acids especially cystine. The amino acids were usually separated by then standard chemical procedures based on differences in solubility, selective precipitation by agents such as Reinecke salt (proline and hydroxyproline), or flavianic acid (arginine). 

True alkaloids derive from amino acid and they share a heterocyclic ring with nitrogen. These alkaloids are highly reactive substances with biological activity even in low doses. All true alkaloids have a bitter taste and appear as a white solid, with the exception of nicotine which has a brown liquid. True alkaloids form water-soluble salts. Moreover, most of them are well-defined crystalline substances which unite with acids to form salts. True alkaloids may occur in plants (1) in the free state, (2) as salts and (3) as N-oxides. These alkaloids occur in a limited number of species and families, and are those compounds in which decarboxylated amino acids are condensed with a non-nitrogenous structural moiety. The primary precursors of true alkaloids are such amino acids as L-ornithine, L-lysine, L-phenylalanine/L-tyrosine, L-tryptophan and L-histidine . Examples of true alkaloids include such biologically active alkaloids as cocaine, quinine, dopamine, morphine and usambarensine (Figure 4). A fuller list of examples appears in Table 1. 

Niacin, a water-soluble vitamin vital for oxidation by living cells, functions in the body as a component of two important coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). NAD and NADP are involved in the release of energy from carbohydrate, fat, and protein, and in the synthesis of protein, fat, and pentoses for nucleic acid formation. Milk is a poor source of preformed niacin, containing about 0.08 mg per 100 g. However, milk s niacin value is considerably greater than indicated by its niacin content (Horwitt et al. 1981). Not only is the niacin in milk fully available, but the amino acid tryptophan in milk can be used by the body for the synthesis of niacin. For every 60 mg of tryptophan consumed, the body synthesizes 1 mg of niacin. Therefore, the niacin equivalents in 100 g milk equal 0.856 mg including that from pre-... 

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