Amino acids, isolation

CgHiiNO. M.p. 282 C (decomp.). The naturally occurring substance is laevorotatory. It is an amino-acid isolated from various plant sources, but not found in the animal body. It is formed from tyrosine as the first stage in the oxidation of tyrosine to melanin. It is used in the treatment of Parkinson s disease. 

Raney nickel desulfurization has been applied especially to the synthesis of different kinds of amino acids. a-Amino acids have been prepared by the Strecker synthesis of substituted thiophenealdehydes, followed by desulfurization of the thiophene a-amino acids. a-Amino-n-enantic acid, a-amino-n-caprylic acid, and norleucin have been obtained in about 50% yield from the appropriate thiophene aldehydes. From the desulfurization of thiophene -amino acids, obtained from the reaction of thiophenealdehydes with malonic acid in ammonia, aliphatic j8-amino acids, isolated as acetates, have been obtained in high yields. The desulfurization of 3-nitrothiophenes, such as (232), in ammonia leads to y-substituted amino acids (233). ... 

Different enzymes have different specificities. Some, such as amylase, are specific for a single substrate, but others operate on a range of substrates. Papain, for instance, a globular protein of 212 amino acids isolated from papaya fruit, catalyzes the hydrolysis of many kinds of peptide bonds. In fact, it s this ability to hydrolyze peptide bonds that makes papain useful as a meat tenderizer and a cleaner for contact lenses. 

Table I. Amino Acids Isolated from Plant and Animal Products...

Amino acids isolated from protein hydrolysates. 

An interesting and important fact is that almost all amino acids isolated from proteins L-configuration have the L-configuration at the a-carbon, although some amino acids isolated from microbiological sources are the mirror image isomers, ie in the D-configuration. We shall consider amino add stereochemistry in more detail in section 8.3. 

Figure 1. Structures of some nonprotein amino acids isolated from plants...

Hare, P.E., Fogel, ML., Stafford, T.W. Jr., Mitchell, A.D. and Hoering, T.C. 1991 The isotopic composition of carbon and nitrogen in individual amino acids isolated from modern and fossil proteins. Journal of Archaeological Science 18 227-292. 

Macko, S.A., Estep, M.L.F., Hare, PE. and Hoering, T.C. 1983 Stable nitrogen and carbon isotopic composition of individual amino acids isolated from cultured microorganisms. Carnegie Institute of Washington Yearbook 82 404-410. 

Fujimoto, D., Horiuchi, K. and Hirama, M. (1981) Isotrityrosine, a new crosslinking amino-acid isolated from Ascaris cuticle collagen. Biochemical and Biophysical Research Communications 99, 637-643. 

H. Inatomi, and N. Mori. Water-soluble constituents of crude drugs. III. 20320 Free amino acids isolated from ginger rhizome. Yakugaku Zasshi 1965 ... 

Williams and Fegley (40) utilized his chiral template (Section 3.2.3) as a chiral dipolarophile in the concise synthesis of 5 -( )-cucurbitine, a naturally occurring amino acid isolated from species of pumpkin, that acts as a growth inhibitor to... 

P-type channels inactivate extremely slowly and are insensitive to both DHPs and co-conotoxin GVIA, but are blocked by the spider venom peptide co-agatoxin IVA, a peptide consisting of 48 amino acids isolated from the American funnel-web spider Agelenopsis aperta. 

Harder, T. and Qian, P. Y., Induction of larval attachment and metamorphosis in the serpulid polychate Hydroides elegans by dissolved free amino acids isolation and identification, Mar. Ecol. Prog. Ser., 179, 259, 1999. 

Restricted rotation, as surface conjestion increases, was postulated as being responsible for the observed optical rotations as the generations increase,1251 the possibility of racemization during amino acid acylation was also investigated. Amino acid isolation and high-performance liquid chromatography (HPLC) analysis following acidic hydrolysis of the asymmetric dendrimers revealed an enantiomeric excess > 96 %. 

Lactam hydrolysis under acidic conditions only seems to occur with compounds in which Nb is neutral thus, strychninolones-a and -b are converted into the amino acids, isolated as the methyl esters, by warming with concentrated hydrochloric acid at 100° (50, 52). Strychninolone-c cannot be hydrolyzed under these conditions, which is in keeping with it being the thermodynamically most stable of the three isomers (52). 

Problems remain, and differing lines of evidence suggest that racemization dating of bone is, at best, tentative, and that many of the early dates for human skeletons are wrong. For instance, the Sunnyvale skeleton (racemization dated at 70,000 years B.P.) is morphologically indistinguishable for skeletons dated between 400 and 1600 years B.P. (10). Another important and controversial skeleton was described in Denver. Bada and Masters presented the results of a detailed study of the general composition and extent of racemization of amino acids isolated from the Del Mar Man skeleton (11). 

These remains were found eroding from the face of a coastal bluff in Del Mar, CA, in 1929. A variety of dates have been obtained for these remains, depending upon which materials were analyzed and which dating method was used. Bada and Masters reported on new dates based upon the new and more sensitive C-14 dating technique. The results, obtained on amino acids isolated from the bone, indicated that the skeleton was 5400 years old. These results were made possible by the more recent important advances in carbon dating that are described in Chapter 16. 

Harington, J.S. and Cilliers, J.J. le R., 1963. A possible origin of the primitive oils and amino acids isolated from amphibole asbestos and banded ironstone. Geochim. Cosmochim. Acta, 27 411-418. Harrison, C.G.D. and Peterson, M.N.A.-, 1965. A magnetic mineral from the Indian Ocean. Am. Mineral. 50 704-712. 

As discussed above DOM contains between 200 and 500 nM of DCAA (Lee and Bada, 1975, 1977) and HMWDOM contains between 178 and 278 nM DCAA (McCarthy et al., 1998). Based on these values, between 30% and 100% of DCAA are in the >1000 Da fraction of DOM. Coffin (1989) found that 60% of aU amino acids isolated from a Delaware estuary were in the <1 kDa fraction and Sommerville and Preston (2001) showed that >90% of total DCAA (as analyzed by GC/MS) are released from peptides with MWs <3 kDa. Taken together, these studies suggest that peptides and small proteins ( 500 and 3000 Da) contain most of the amino acids detected in DOM so far. Unfortunately, precise MW information is not currently available for proteins in HMWDOM or DOM. 

The stable C isotopic (5 C) signature of organic compounds is commonly employed for source apportionment, but few studies have applied this strategy for specific compounds within DOM. Recently, in an effort to identify specific HMWDOM sources McCarthy et al. (2004) compared the 5 C signature of individual amino acids in HMWDOM to those amino acids isolated from a variety of autotrophic and heterotrophic organisms. Based on patterns of amino acid-specific 8 C values these authors concluded that amino acids in HMWDOM were derived from an autotrophic source. However, this study focused on a Hmited sample set and considerable variations in 8 C signature of amino acids was apparent. 

Calycnlin A (38) is an extraordinary metabolite composed of C28 fatty acid and two y-amino acids isolated from the sponge Discodermia calyx. It is not only highly antifnngal and antitnmor bnt also a potent cancer promoter that was fonnd to be cansed by potent inhibition of protein phosphatases 1 and 2A (1). More than 15 calycnlin derivatives were isolated from several marine sponges, which indicates the involvement of symbiotic microorganisms in the prodnction of calycnhns (6). 

Mueller, J. H. A New Sulfur Containing Amino Acid Isolated from the... 

Dihydroxyphenylalanine (for structure see diagram 11) is an amino acid isolated (from the pods and sprouts of Vida fd>a) and first definitely identified in 1913 by Guggenheim (323), who showed it to be identical with synthetic material previously prepared (280). It is widely distributed in certain types of plants (beans, etc.) but is not a normal protein constituent. However, it plays an important part in mammalian metabohsm of tyrosine, as it is the precursor of adrenaline (epinephrine), noradrenaline (arterenol, norepinephrine), and melanin. In this review these substances will be considered only insofar as they account for a portion of normal tyrosine metabolism. 

Furthermore, does an intrinsic reason exist in our world to exclusively use the L-amino acids instead of the D-series It is remarkable that the amino acids isolated from extraterrestrial organic matter from meteorites that are at least somewhat carbonaceous are slightly enriched in the enantiomers of the same L-series as those present in the amino acids of living organisms (Pizzarello, 2004). This would become a serious question only once we have discovered a few other life-forms in the universe and found them all to be based on L-amino acids. I know that others have a different point of view and consider the origin of chirality and of homochirality to be an important problem. I think it is not, in contrast with some related but simpler questions, such as that of the propagation of homochirality. 

Racemization might also be used to estimate the age of amino acids found in ground waters. Degens et al. (3) claim that the amino acids isolated from various petroleum brine waters are of the same age as that of the formation in which they are found. The formations which were investigated ranged in age from a million to a few hundred million years. If the amino acids found in the brine waters are the same age as the formations, they would be expected to be completely racemized. On the... 

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