The influence of amino acids on the lobeline production of Lobelia inflata L. hairy root cultures

The herb Lobelia inflata L. (Lobeliaceae) containspiperidine alkaloids. The main alkaloid is the pharmacologically-activelobeline. We have studied the effects of alkaloid precursor amino acids (lysineand phenylalanine) on the growth and alkaloid production of hairy root culturesof Lobelia inflata L. The hairy root clone 8009/h7transformed with Agrobacterium rhizogenes strain R 1601wascultivated on B5 solid medium containing lysine (Lys) and phenylalanine (Phe)both in the presence and absence of the growth regulators IAA and kinetin. Onthe medium containing hormones growth was delayed until day 14. The applicationof growth regulators to the B5 media containing amino acids either singly or incombination increased the biomass in all cases. The maximum dry weight wasachieved in a medium containing Phe+Lys and growthregulators. The highest lobeline level (36 g/g) was detectedintissues cultivated on hormone-free medium containing Phe. In hormone-freemedia,lobeline production increased in the presence of either Phe or Lys comparedwiththe control, but the addition of both greatly decreased synthesis. In contrast,the addition of both amino acids to media supplemented with IAA and kinetinincreased lobeline production.     

The effect of some non-protein amino acids on pollen germination and pollen-tube growth in five species of the Vicieae

Summary The effects of canavanine, ,-diaminobutyric acid, homoarginine and lathyrine on the germination of pollen and on in-vitro growth of pollen tubes were studied in the following species: Lathyrus niger, L. silvestris, Vicia unijuga, Pisum sativum and Cicer arietinum.The effects of these non-protein amino acids depended on their quantity and on the plant species. Every amino acid had a promoting effect on germination and growth at some concentration in some species. Inhibition or promotion of pollen germination and pollen-tube growth were usually parallel. The stronger influence of some amino acid on growth than on germination may be due to slow penetration of the acid into the cell.Homoarginine and lathyrine had a promoting effect at all concentrations in L. niger, a species in which these amino acids occur naturally. In most other species they had, if anything, a very slight inhibitory effect, ,-Diaminobutyric acid and canavanine had the strongest inhibitory effects on the species studied. It seems possible that these amino acids are antimetabolites of common amino acids.It is obvious that non-protein amino acids can form effective hybridization barries, although the conditions in nature are more complex than in vitro. The ability to synthesize a new amino acid may therefore be of evolutionary significance in the isolation of new species and genera.     

GTP pool expansion is necessary for the growth rate increase occurring in Bacillus subtilis after amino acids shift-up

After addition of amino acids to a Bacillus subtilis glucose culture the intracellular guanosine triphosphate (GTP) concentration increased. The growth rate and the rate of RNA accumulation increased too. With mycophenolic acid, an inhibitor of inosinate dehydrogenase, it was possible to adjust the intracellular GTP concentration to values ranging between that of the glucose culture and that of the culture which had received amino acids. This led to intermediate growth rate values. Guanosine abolished the mycophenolic acid inhibition of GTP synthesis. It also counteracted the drug effects on growth rate and RNA accumulation. In cultures growing on Nutrient Sporulation Medium, in which the growth rate decreases as cell density increases, the GTP concentration did correlate with the growth rate.Abbreviations ppGpp guanosine 5-diphosphate 3-diphosphate - pppGpp guanosine 5-triphosphate 3-diphosphate     

Survival of <Emphasis Type="Italic">Lactobacillus sakei</Emphasis> during heating,drying and storage in the dried state when growth has occurred in the presence of sucrose or monosodium glutamate

Spray-dried cells of Lactobacillus sakei CTC 494 survived ca. 60% longer in the spray dried state when cells were grown in the presence of 20g sucrose l^–1or 12.5g monosodium glutamate l^–1. No significant differences were observed in viability during storage in the freeze dried state with the addition of these compounds to the growth medium, nor in survival during a heat treatment (55°C). Both sucrose and glutamate in the growth medium suppressed intracellular accumulation of total amino acids and changed the overall pattern of the individual amino acids. Glutamate in the growth medium enhanced intracellular glutamate by ca. 38%. Revisions requested 4 November 2004; Revisions received 13 December 2004     

Characterization of amino-acid transport in Ricinus communis roots using isolated membrane vesicles

The mechanism and specificity of amino-acid transport at the plasma membrane of Ricinus communis L. roots was investigated using membrane vesicles isolated by phase partitioning. The transport of glutamine, isoleucine, glutamic acid and aspartic acid was driven by both a pH gradient and a membrane potential (internally alkaline and negative), created artificially across the plasma membrane. This is consistent with transport via a proton symport. In contrast, the transport of the basic amino acids, lysine and arginine, was driven by a negative internal membrane potential but not by a pH gradient, suggesting that these amino acids may be taken up via a voltage-driven uniport. The energized uptake of all of the amino acids tested showed a saturable phase, consistent with carrier-mediated transport. In addition, the membrane-potential-driven transport of all the amino acids was greater at pH 5.5 than at pH 7.5, which suggests that there could be a direct pH effect on the carrier. Several amino-acid carriers could be resolved, based on competition studies: a carrier with a high affinity for a range of neutral amino acids (apart from asparagine) but with a low affinity for basic and acidic amino acids; a carrier which has a high affinity for a range of neutral amino acids except isoleucine and valine, but with a low affinity for basic and acidic amino acids; and a carrier which has a higher affinity for basic and some neutral amino acids but has a lower affinity for acidic amino acids. The existence of a separate carrier for acidic amino acids is discussed.Abbreviations PM plasma membrane - TPP⁺ tetraphenylphosphonium ion - pH pH gradient - membrane potential This work was supported by the Agricultural and Food Research Council and The Royal Society. We would like to thank Mrs. Sue Nelson for help with some of the membrane preparations.     

Ecophysiological aspects of growth and nitrogen fixation inAzospirillum spp.

The nitrogenase activity ofAzospirillum spp. is efficiently regulated by environmental factors. InA. brasilense andA. lipoferum a rapid switch off of nitrogenase activity occurs after the addition of ammonium chloride. As in photosynthetic bacteria, a covalent modification of nitrogenase reductase (Fe-protein) is involved. InA. amazonense, a non-covalent mechanism causes only a partial inhibition of nitrogenase activity after ammonium chloride is added. In anaerobic conditions, nitrogenase reductase is also switched off by a covalent modification inA. brasilense andA. lipoferum. Short-time exposure ofAzospirillum to increased oxygen levels causes a partially reversible inhibition of nitrogenase activity, but no covalent modification is involved.Azospirillum spp. show variations in their oxygen tolerance. High levels of carotenoids confer a slightly improved oxygen tolerance. Certain amino acids (e. g. glutamate, aspartate, histidine and serine) affect growth and nitrogen fixation differently inAzospirillum spp. Amino acids may influence growth and nitrogen fixation ofAzospirillum in the association with plants.Azospirillum brasilense andA. halopraeferens are the more osmotolerant species. They utilize most amino acids poorly and accumulate glycine betaine, which also occurs in osmotically stressed grasses as a compatible solute to counteract osmotic stress. Nitrogen fixation is stimulated by glycine betaine and choline. Efficient iron acquisition is a prerequisite for competitive and aerotoleran growth and for high nitrogenase activity.Azospirillum halopraeferens andA. amazonense assimilate iron reasonably well, whereas growth of someA. brasilense andA. lipoferum strains is severely inhibited by iron limitation and by competition with foreign microbial iron chelators. However, growth of certain iron-limitedA. brasilense strains is stimulated by the phytosiderophore mugineic acid. Thus, various plant-derived substances may stimulate growth and nitrogen fixation ofAzospirillum.     

Peptide chain elongation rate and ribosomal activity in Saccharomyces cerevisiae as a function of the growth rate.

Summary The peptide-chain elongation rate of Saccharomyces cerevisiae at two different growth rates was estimated by the kinetics of radioactive labelling of nascent and finished polypeptides as described by Gausing, 1972, and Young and Bremer, 1976. The elongation rates of a diploid strain cultured in yeast nitrogen base supplemented with glucose or acetate were 9.3 amino acids/s and 5.5 amino acids/s at 30°C, respectively. These data together with published values on the ribosomal efficiency as a function of growth rate (Waldron and Lacroute, 1975) enable us to estimate the rate of synthesis of ribosomal proteins as a function of the rate of total protein synthesis, _r, and the fraction of ribosomes that are active in protein synthesis. We conclude that in S. cerevisiae _r, is largely independent of the growth rate while the fraction of active ribosomes decreases with decreasing growth rate.     

Utilization of aromatic amino acids as nitrogen sources in Brevibacterium linens: an inducible aromatic amino acid aminotransferase

The first step of the utilization of the aromatic amino acids as sole nitrogen sources by Brevibacterium linens strain 47 was found to be a transamination. The deaminated metabolites of the amino acids were detected in culture supernatants, and the enzyme activity was identified in cell free extracts. The cells contained increased aromatic amino acid aminotransferase activities on growth on the aromatic amino acids as sole nitrogen sources. Two aromatic aminotransferases (AT-I and AT-II) were separated upon diethylaminoethyl-Trisacryl M column chromatography of cell free extracts. Only AT-I was responsible for the increased level of aromatic amino acid aminotransferase activity of induced cells. The results suggested a catabolic role of AT-I in vivo.Abbreviations DNP dinitrophenyl - HPLC high performance liquid chromatography - PLP pyridoxal-5-phosphate     

Selective inactivation of heterokaryons of Candida albicans by anaerobiosis

Heterokaryons (hets), but not monokaryons of Candida albicans die when grown anaerobically on minimal medium. Their rates of inactivation increase with decreases in growth temperatures from 37°C to 25°C. At 10°C, however, anaerobiosis is not lethal and suppresses the inactivation which normally occurs among hets cultured aerobically at that temperature. Killing of hets by anaerobiosis can be altered significantly by certain exogenously provided amino acids or intermediates of oxidative respiration. Aspartic acid alone promotes inactivation whereas alanine, glutamic acid or lysine individually have no effects. However, glutamate and lysine combined afford slight protection against inactivation while aspartate and glutamate combined, with or without lysine, are highly protective: the activity of the aspartate-glutamate combination is completely negated by the addition of alanine. Other common amino acids have no effects on het responses to anaerobiosis other than the ability, when combined, to relieve the antagonism of alanine for the aspartate-glutamate combination. Anaerobic survivals are also enhanced by oxalacetic acid or -ketoglutaric acid, and even more so by a combination of these two intermediates. The resistances to inactivation elicited by the oxalacetate -ketoglutarate or aspartate-glutamate combinations are not additive. These relationships are interpreted to signify that inactivation of hets by anaerobic growth is largely, if not exclusively, due to depletion of their oxalacetic acid and -ketoglutaric acid contents for amino acid biosyntheses, and the unique inability of het cells to replenish those keto acids upon subsequent return to aerobic conditions. The observations are consistent with previous indications that mitochondria formed by hets are functionally abnormal.     

Kinetic characterization of carboxypeptidase-Y-catalyzed peptide semisynthesis Prediction of yields

Summary Carboxypeptidase-Y-catalyzed peptide semisynthesis has been characterized at pH 7.5, 25°C from initial rate steady state kinetic and progress reaction studies of hydrolysis and aminolysis of-N-benzoyl-L-tyrosine 4-nitro-anilide using the natural L-amino acids and their amides as nucleophiles. The reaction mechanism previously shown to account for carboxypeptidase-Y-catalyzed aminolysis reactions (Christensen et al., 1992) was found also to account for all of the reactions studied here. It involves in addition to the classical serine proteinase mechanism: i) complex formation between the free enzyme and the nucleophile, an interaction characterized by the competitive inhibition constant,K _i, and ii) reaction of the nucleophile with the acylated enzyme forming a complex of enzyme and aminolysis product, characterized by the aminolysis kinetic parameter,K _N.A competitive inhibitory effect showing binding to the free enzyme is seen mainly with large hydrophobic amino acids and their amides i.e. the same residues as those preferred on either side of the scissile bond in carboxypeptidase-Y substrates. The stoichiometry of the inhibition is 1 : 1 and the actual binding position most likely is that of the leaving group of substrates,S ₁.Aminolysis effects are obtained with a wide range of amino acids and amino acid amides, exceptions are Pro and, probably due to their low solubility, Tyr, Trp, Asp and Glu. TheK _N-values show relatively little dependence on the chemical nature of the side groups, but a marked difference between the amino acid and its amide. The amides interact more strongly. The kinetic parameter,k _c/K_m, of the hydrolysis of the aminolysis products is another important factor in peptide semisynthesis. Thek _c/K_m-values obtained of the amidated aminolysis products are much less than those of the products formed with free amino acids. All in all this leads to rather efficient aminolysis with the L-amino acid amides and poor aminolysis with the L-amino acids.Abbreviations BzTyrNHPhNO₂ -N-benzoyl-L-tyrosinyl 4-nitro-aniline - Xaa L-amino acids - Xaaa L-amino acid amides - Z-Phe Carbobenzoxy-L-phenylalanine - Z-Met Carbobenzoxy-L-methionine - BzTyr -N-benzoyl-L-tyrosine - AlaVal L-alanyl-L-valine - ValAla L-valyl-L-alanine     

Amino acids in carbonaceous chondrites

For almost 20 years laboratory experiments have advanced the concepts of chemical evolution, particularly with regard to formation of the amino acids. What has been generally lacking is concrete natural evidence for this chemical evolution hypothesis. The recent development of sophisticated analytical techniques and availability of carbonaceous chondrites with a minimum of terrestrial contamination has resulted in the identification of amino acids which provide strong evidence for a natural extraterrestrial chemical synthesis. Since the initial find in the Murchison meteorite (a type II carbonaceous chondrite) of both protein and nonprotein amino acids and amino acids with nearly equal abundances of D and L isomers, further studies have been carried out. These studies have revealed the presence of at least 35 amino acids; the population consists of a wide variety of linear, cyclic and polyfunctional amino acids which shows a trend of decreasing concentration with increasing carbon number. Investigations of the Murray meteorite (a type II carbonaceous chondrite) has produced similar results, but studies of the Orgueil meteorite (a type I carbonaceous chondrite) show only a limited suite of amino acids, some of which appear to be indigenous while others appear to be terrestrial contaminants. A sample of the Murchison meteorite was extracted with D₂O and in addition to free amino acids, showing no deuterium incorporation, some amino acids showed the presence of deuterium suggesting either a precursor(s) or hydrogendeuterium exchange which require(s) formation of carbon-hydrogen bonds.     

Effects of a vesicular-arbuscular mycorrhizal fungus and other soil microorganisms on growth,mineral nutrient acquisition and root exudation of soil-grown maize plants

Maize (Zea mays L. cv. Alize) plants were grown in a calcareous soil in pots divided by 30-m nylon nets into three compartments, the central one for root growth and the outer ones for hyphal growth. Sterle soil was inoculated with either (1) rhizosphere microorganisms other than vesicular-arbuscular mycorrhizal (VAM) fungi, (2) rhizosphere microorganisms together with a VAM fungus [Glomus mosseae (Nicol. and Gerd.) Gerdemann and Trappel], or (3) with a gamma-irradiated inoculum as control. Plants were grown under controlled-climate conditions and harvested after 3 or 6 weeks. VAM plants had higher shootroot ratios than non-VAM plants. After 6 weeks, the concentrations of P, Zn and Cu in roots and shoots had significantly increased with VAM colonization, whereas Mn concentrations had significantly decreased. Root exudates were collected on agar sheets placed on the interface between root and hyphal compartments. Six-week-old VAM and non-VAM plants had similar root exudate compositions of 72–73% reducing sugars, 17–18% phenolics, 7% organic acids and 3% amino acids. In another experiment in which root exudates were collected on agar sheets with or without antibiotics, the amounts of amino acids and carbohydrates recovered were similar in VAM and non-VAM plants. However, threeto sixfold higher amounts of carbohydrates, amino acids and phenolics were recovered when antibiotics were added to the agar sheets. Thus, the high microbial activity in the rhizosphere and on the rhizoplane limits the exudates recovered from roots.     

Uptake of lysine and prolinevia separate α-neutral amino acid transport pathways inMytilus gill brush border membranes

Summary Brush border membrane vesicles (BBMV) were prepared from the gills of the marine mussel,Mytilus edulis. These membranes contained two distinct pathways for cotransport of Na⁺ and -neutral amino acids. The major pathway in mussel gill BBMV was the alanine-lysine (AK) pathway, which had a high affinity for alanine and for the cationic amino acid, lysine. The AK pathway was inhibited by nonpolar -neutral amino acids and cationic amino acids, but was not affected by -neutral amino acids or imino acids. The kinetics of lysine transport were consistent with a single saturable process, with aJ _max of 550 pmol/mg-min and aK _t of 5 m. The AK pathway did not have a strict requirement for Na⁺, and concentrative transport of lysine was seen in the presence of inwardly directed gradients of Li⁺ and K⁺, as well as Na⁺. Harmaline inhibited the transport of lysine in solutions containing either Na⁺ or K⁺. The alanine-proline (AP) pathway transported both alanine and proline in mussel gill BBMV. The AP pathway was strongly inhibited by nonpolar -neutral amino acids, proline, and -(methylamino)isobutyric acid (Me-AIB). The kinetics of proline transport were described by a single saturable process, with aJ _max of 180 pmol/mg-min andK _t of 4 m. In contrast to the AK pathway, the AP pathway appeared to have a strict requirement for Na⁺. Na⁺-activation experiments with lysine and proline revealed sigmoid kinetics, indicating that multiple Na⁺ ions are involved in the transport of these substrates. The transport of both lysine and proline was affected by membrane potential in a manner consistent with electrogenic transport.     

Salinity dependence,uptake kinetics,and specificity of amino-acid absorption across the body surface of the oligochaete annelidEnchytraeus albidus

Enchytraeus albidus is able to absorb dissolved¹⁴C-labeled neutral amino acids (glycine, L-alanine, L-valine,-aminoisobutyric acid) and an amino-acid mixture from ambient water across the body surface against considerable concentration gradients. Saturation kinetics and susceptibility of glycine uptake to competitive inhibition by alanine suggest mediated transport. Absorption of neutral amino acids is an active process. Exchange diffusion of preloaded-aminoisobutyric acid against external glycine or-aminoisobutyric acid could not be detected. Results on inhibition of glycine uptake by a variety of low-molecular-weight substances indicate that glycine absorption is highly specific for neutral amino acids and somewhat less for basic amino acids; it is unspecific for non--amino acids, acidic amino acids, carbohydrates, and organic acids. Rates of transintegumentary net influx of glycine are nearly identical to¹⁴C-glycine influx, suggesting that only small amounts of amino acids are released, as compared with the capacity for uptake. Thus,¹⁴C-amino-acid influx data are used for characterization of the uptake system. Glycine uptake is positively correlated to external salinity. In fresh water, absorption is nearly zero; between 10 and 20 S, uptake increases markedly reaching maximum values at 30 S; these remain almost constant at 40 S. Transport constants and maximum uptake rates increase with rising salinities. Since absorption of glycine and L-valine is susceptible to sodium depletion, similar mechanisms presumably underly salinity-dependent uptake of amino acids and sodium-dependent solute transport. Oxygen consumption is not significantly modified by different external salinities. Estimates of nutritional profit gained from absorption of amino acids vary between 4 and 15 % of metabolic rate for glycine absorption and between 10 and 39 % for uptake of an amino-acid mixture, according to external concentrations (10 and 50 µM) and salinities (20 and 30 S).     

A Chlamydomonas gene encodes a G protein β subunit-like polypeptide

Summary A Chlamydomonas gene encodes a protein that shows sequence similarity with the subunit of guanine nucleotide binding proteins from mammals, fruit fly and yeast. In addition to amino acid sequences similarity, each of these proteins contains a segmented repeat structure in which certain amino acids form a consensus sequence. Thus this gene product has been designated a Chlamydomonas subunit-like polypeptide (Cblp). The mRNA is constitutively expressed during the cell cycle and during flagellar regeneration.     

External factors involved in the regulation of an extracellular proteinase synthesis in Bacillus megaterium

Summary A mathematical model was formulated to describe the kinetics and stoichiometry of growth and proteinase production in Bacillus megaterium. Synthesis of the extracellular proteinase in a batch culture is repressed by amino acids. The specific rate of formation of the enzyme (r _E) can be described by the formula {ie373-1}, where k ₂ and k ₃ stand for the non-repressible and repressible part of enzyme synthesis respectively, k _{S 2} is a repression coefficient and S ₂ indicates the concentration of amono acids; the values of k ₂ and k _{S 2} depend on the composition of the mixture of amino acids. Even in a high concentration, a single amino acid is less effective than a mixture of amino acids. The dependence of the proteinase repression on the concentration of an external amino acid (leucine) follows the same course as its rate of incorporation into proteins, approaching saturation at concentrations higher than 50 M (half saturation approximately 10 M). However, the total uptake of leucine did not exhibit any saturation even at 500 M external concentration.Symbols X biomass concentration, g/l - E proteinase concentration, unit/l - t time, h - S ₁ concentration of glucose, g/l - S ₂ concentration of amino acids, g/l - specific growth rate, l/h - rE specific rate of enzyme production, unit/g/h - k ₁ growth kinetic constant, l/h - k ₂ product formation kinetic constant (for non-repressible part of enzyme synthesis), unit/g - k ₃ product formation kinetic constant (for repressible portion of enzyme synthesis), unit/g - k _{S 1} saturation constant, g/l - k _{S 2} repression coefficient for a certain amino acid or amino acids mixture, g/l     

Peptide modification by incorporation ofα-trifluoromethyl substituted amino acids

Summary Metabolic stabilization of pharmacologically active peptides can be achieved by incorporation of sterically hindered non-natural amino acids, e.g. C ^, -disubstituted amino acids.-Trifluoromethyl substituted amino acids, a subclass of C ^, -disubstituted amino acids, also fulfil this requirement while featuring additional properties based on the electronic influence of the fluorine substituents.This review summarizes the results concerning the stability of peptides containing-TFM amino acids towards proteolysis by-chymotrypsin. Furthermore, configurational effects of-TFMAla on the proteolytic stability of peptides are explained using empirical force field calculations. The influence of-TFMAla incorporation on the secondary structure of selected tripeptide amides is compared to the effects exerted by its fluorine-free analogue, aminoisobutyric acid.Finally, results on metabolic stabilization and biological activity of modified thyrotropin releasing hormone are interpreted.     

Isolation of biochemical mutants using haploid mesophyll protoplasts of Hyoscyamus muticus

A population of 3070 clones derived from N-methyl-N-nitro-N-nitrosoguanidine (MNNG)-treated mesophyll protoplasts of haploid Hyoscyamus muticus was tested for amino-acid auxotrophy without enrichment. One clone (MA-2) was stably and specifically dependent on casein hydrolysate and could be fed also by a number of single amino acids or by other reduced nitrogen sources. MA-2 was found to be chlorate resistant and devoid of in vivo nitrate reductase activity under inductive conditions. Permissive and restrictive growth conditions for MA-2 were investigated more closely and media were found promoting morphogenesis. Selection and testing of clones were complicated by an unspecific growth stimulation of some wild type cultures by amino acids, thiamine and m-inositol.Abbreviations NAA 1-naphthaleneacetic acid - BAP 6-benzylaminopurine - MNNG N-methyl-N-nitro-N-nitrosoguanidine - NR nitrate reductase - CH casein hydrolysate     

Amino acid uptake by Lemna gibba by a mechanism with affinity to neutral L-and D-amino acids

Earlier work suggested that amino acid uptake by Lemna gibba cells is a H⁺-cotransport mechanism driven by a proton-electrochemical gradient at the plasmalemma. The present investigations of the transient membrane depolarizations elicited by amino acids and tracer-uptake experiments show that all neutral -L-amino acids, D-alanine and analogues, like -alanine and p-fluorophenylalanine, are transported by the same system. It remains to be seen if there are separate mechanisms for the uptake of acidic and basic amino acids.     

Theβ-sheets of proteins,the biosynthetic relationships between amino acids,and the origin of the genetic code

Two forces are generally hypothesised as being responsible for conditioning the origin of the organization of the genetic code: the physicochemical properties of amino acids and their biosynthetic relationships (relationships between precursor and product amino acids). If we assume that the biosynthetic relationships between amino acids were fundamental in defining the genetic code, then it is reasonable to expect that the distribution of physicochemical properties among the amino acids in precursor-product relationships cannot be random but must, rather, be affected by some selective constraints imposed by the structure of primitive proteins. Analysis shows that measurements representing the size of amino acids, e.g. bulkiness, are specifically associated to the pairs of amino acids in precursor-product relationships. However, the size of amino acids cannot have been selected per se but, rather, because it reflects the-sheets of proteins which are, therefore, identified as the main adaptive theme promoting the origin of genetic code organization. Whereas there are no traces of the-helix in the genetic code table.The above considerations make it necessary to re-examine the relationship linking the hydrophilicity of the dinucleoside monophosphates of anticodons and the polarity and bulkiness of amino acids. It can be concluded that this relationship seems to be meaningful only between the hydrophilicity of anticodons and the polarity of amino acids. The latter relationship is supposed to have been operative on hairpin structures, ancestors of the tRNA molecule. Moreover, it is on these very structures that the biosynthetic links between precursor and product amino acids might have been achieved, and the interaction between the hydrophilicity of anticodons and the polarity of amino acids might have had a role in the concession of codons (anticodons) from precursors to products.