Ancient amino acids from fossil feathers in amber.

Ancient protein analysis is a rapidly developing field of research. Proteins ranging in age from the Quaternary to Jurassic are being used to answer questions about phylogeny, evolution, and extinction. However, these analyses are sometimes contentious, and focus primarily on large vertebrates in sedimentary fossilisation environments; there are few studies of protein preservation in fossils in amber. Here we show exceptionally slow racemisation rates during thermal degradation experiments of resin enclosed feathers, relative to previous thermal degradation experiments of ostrich eggshell, coral skeleton, and limpet shell. We also recover amino acids from two specimens of fossil feathers in amber. The amino acid compositions are broadly similar to those of degraded feathers, but concentrations are very low, suggesting that much of the original protein has been degraded and lost. High levels of racemisation in more apolar, slowly racemising amino acids suggest that some of the amino acids were ancient and therefore original. Our findings indicate that the unique fossilisation environment inside amber shows potential for the recovery of ancient amino acids and proteins.

Nutrition in critical care.

Critical care has evolved from a prolonged recovery room stay for cardiac surgery patients to a full medical and nursing specialty in the last 5 decades. The ability to feed patients who cannot eat has evolved from impossible to routine clinical practice in the last 4 decades. Nutrition in critically ill patients based on measurement of metabolism has evolved from a research activity to clinical practice in the last 3 decades. The authors have been involved in this evolution and this article discusses past, present, and likely future practices in nutrition in critically ill patients.

Umami and the foods of classical antiquity.

Umami is the taste of foods that are rich in glutamic acid and 2 ribonucleotides, 5'-inosinate and 5'-guanylate. This distinctive taste of modern Eastern cuisine, which is finding a receptive audience in the Western hemisphere, characterized many dishes that ancient Romans consumed >2000 y ago. Romans enjoyed numerous foods that are identified today as containing significant amounts of natural umami substances and frequently used fish sauce as a condiment in their recipes. Fish sauce imparted to Roman dishes a moderately salty, slightly fishy taste that combines synergistically with other foods to create the umami flavor. Fish sauce derives from the hydrolysis of fish in the presence of salt primarily through endogenous enzymic proteolysis. Its simple production process, low cost, and ability to enhance the taste of many foods has made it the basic condiment for traditional dishes consumed in many Southeast Asian countries. Fish sauce also has important nutritional value, primarily in the form of amino acids. Because ancient Romans made fish sauce in the same way and with the same resources as modern fish sauce producers of Southeast Asia, the amino acid profiles of the 2 products are probably nearly identical. Archaeological sources indicate that fish-processing centers operated throughout the Mediterranean area, and processed fish was an important element in long-distance trade. A close study of the remains of the Roman city of Pompeii indicates that fish sauce was a thriving business that rendered the popular condiment accessible to people of all social classes.

[The transition of amino acid drug development for 50 years in Japan (1)--amino acid parenteral fluid].

Twenty kinds of alpha-amino acids that form the constituents of proteins in mammalian tissues are all L-form with the exception of glycine. These proteins consist of both dispensable and indispensable alpha-amino acids, and play an important role as nutrients. The artificial mixtures of these alpha-amino acids are also important as ethical drugs. The history of alpha-amino acid parenteral fluid is not as long as one might think in terms of its clinical applications. The first publication of clinical data on the subject only appeared in 1944. In Japan, the first product using alpha-amino acid solution made from casein protein entered the market in 1950. In 1959, an alpha-amino acid solution produced from optically pure L-form was launched in Japan and became a pioneer in the field of artificial mixture solutions worldwide. From the 1960s, the amino acid industry has developed remarkably in Japan by means of chemically synthetic, enzymatic and microbial methodologies. Since then, most of the optically active alpha-amino acids have been easily obtainable, and the clinical uses of a-amino acid solutions using a variety of combinations have developed tremendously. From the 1950s to the 1970s, most of the mixture solutions containing a large number of a-amino acids were clinically developed for nutritional supplements. However, from the 1990s, amino acid solutions targeting diseases such as hepato-nephricpathy have increased, while new pediatric a-amino acid solutions are still being launched today. Since the year 2000, amino acid kit formulations with vitamins have been developed for convenient use in hospitals.

Ancient biomolecules from deep ice cores reveal a forested southern Greenland.

It is difficult to obtain fossil data from the 10% of Earth's terrestrial surface that is covered by thick glaciers and ice sheets, and hence, knowledge of the paleoenvironments of these regions has remained limited. We show that DNA and amino acids from buried organisms can be recovered from the basal sections of deep ice cores, enabling reconstructions of past flora and fauna. We show that high-altitude southern Greenland, currently lying below more than 2 kilometers of ice, was inhabited by a diverse array of conifer trees and insects within the past million years. The results provide direct evidence in support of a forested southern Greenland and suggest that many deep ice cores may contain genetic records of paleoenvironments in their basal sections.

Long term changes in the distribution and delta(15)N values of individual soil amino acids in the absence of plant and fertiliser inputs.

The long-term 'biodegradation' on soil amino acids was examined in the control plots of '42 parcelles' experiment, established in 1928 at INRA, Versailles (France). None of the plots is cultivated, but is kept free of weeds, and mixed to a depth of 25 cm twice yearly. Topsoil (0-10 cm depth) samples collected in 1929, 1963 and 1997 were subjected to acid hydrolysis (6 N HCl) for comparison. The distribution and delta(15)N natural abundance of 20 individual amino acids in the soils were determined, using ion chromatography (IC) and gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). The total N and amino acid-N (AA-N), respectively, decreased by 54 % and 73 % in the period from 1929 to 1997. The average N loss was comparable for 1929-1963 (period 1) and 1963-1997 (period 2), but AA-N loss was three times faster in the former period. This significant reduction in total AA-N content was mirrored in the individual amino acids, which decreased by 74 % +/- 1 % (ranging 58-89 %) between 1929 and 1997. The bulk delta(15)N values generally increased from 1929 to 1997, mainly associated with comparable or even higher increase of delta(15)N of the non-AA-N in the soil. The residence time (t(1/2), time in which half of N was lost from a specific soil pool) was ca. 65 +/- 5 years for the bulk soil, and comparable for periods 1 and 2. However, between periods 1 and 2 it decreased from 128 to 41 years in the non-AA pool, but increased from 59 to 92 years in the AA-N pool. Proline and amino acids that appear early in soil microbial metabolic pathways (e.g. glutamic acid, alanine, aspartic acid and valine) had relatively high delta(15)N values. Phenylalanine, threonine, glycine and leucine had relatively depleted delta(15)N values. The average delta(15)N value of the individual amino acids (IAAs) increased by 1delta unit from 1929 to 1997, associated with a similar rise from 1929 to 1963, and no change thereafter till 1997. However, the delta(15)N values of phenylalanine decreased by more than 7delta(15)N units between 1929 and 1997. The delta(15)N shift of IAAs from 1929 to 1963 and from 1929 to 1997 was not influenced by the relative amount of N remaining compared with the 1929 soil concentrations. The only exception was phenylalanine which showed decreasing delta(15)N associated with its decreasing concentration in the soil. We conclude therefore that in the absence of plant and fertiliser inputs, no change in the delta(15)N value of individual soil amino acids occurs, hence the original delta(15)N values are preserved and diagnostic information on past soil N (cycling) is retained. The exception was phenylalanine, its delta(15)N decreased with decreasing concentration from 1929 to 1997, hence it acted as a 'potential' marker for the land use changes (i.e. arable cropping to a fallow). The long term biological processing and reworking of residual amino acids resulted in a (partial) stabilisation in the soil, evidenced by reduced N loss and increased residence time of amino acid N during the period 1963-1997.

Incorporation of nonnatural amino acids into proteins.

The genetic code is established by the aminoacylation of transfer RNA, reactions in which each amino acid is linked to its cognate tRNA that, in turn, harbors the nucleotide triplet (anticodon) specific to the amino acid. The accuracy of aminoacylation is essential for building and maintaining the universal tree of life. The ability to manipulate and expand the code holds promise for the development of new methods to create novel proteins and to understand the origins of life. Recent efforts to manipulate the genetic code have fulfilled much of this potential. These efforts have led to incorporation of nonnatural amino acids into proteins for a variety of applications and have demonstrated the plausibility of specific proposals for early evolution of the code.

Reappraisal of the 20th-century version of amino acid metabolism.

In this article, we advocate the radical revision of the 20th-century version of amino acid metabolism as follows. (1) Classic studies on the incorporation of [15N]ammonia into glutamate, once considered to be an epoch-making event, are not distinctive proof of the ability of animals to utilize ammonia for the synthesis of alpha-amino nitrogen. (2) Mammalian glutamate dehydrogenase has been implicated to function as a glutamate-synthesizing enzyme albeit lack of convincing proof. This enzyme, in combination with aminotransferases, is now known to play an exclusive role in the metabolic removal of amino nitrogen and energy production from excess amino acids. (3) Dr. William C Rose's "nutritionally nonessential amino acids" are, of course, essential in cellular metabolism; the nutritional nonessentiality is related to their carbon skeletons, many of which are intermediates of glycolysis or the TCA cycle. Obviously, the prime importance of amino acid nutrition should be the means of obtaining amino nitrogen. (4) Because there is no evidence of the presence of any glutamate-synthesizing enzymes in mammalian tissues, animals must depend on plants and microorganisms for preformed alpha-amino nitrogen. This is analogous to the case of carbohydrates. (5) In contrast, individual essential amino acids, similar to vitamins and essential fatty acids, should be considered important nutrients that must be included regularly in sufficient amounts in the diet.