γ-Aminobutyric acid (GABA) and other amino acids in tissues of the tick,Amblyomma hebraeum (Acari: Ixodidae) throughout the feeding and reproductive periods

We assayed a variety of tick (Amblyomma hebraeum Koch; Acari, Ixodidae) tissues for a number of amino acids throughout the feeding and early reproductive periods. Our HPLC assay could detect as little as 2–5 pmol per sample of the following: GABA, glycine, serine, glutamine, alanine, taurine, glutamate and aspartate. All of these amino acids could be detected in the salivary gland, synganglion (=total CNS in acarines), haemolymph, Gené's organ, seminal receptacle and ovary. GABA reached high levels in the salivary gland of freshly engorged ticks (685 nmol g^-1) and in the synganglion it exceeded 1000 nmol g^-1 throughout most of the feeding cycle and the first week post-engorgement. GABA also reached a peak titre in the haemolymph of 40 nmol ml^-1. Taurine levels peaked at 1065 nmol g^-1 in the salivary gland from large partially fed ticks. Glutamate and aspartate were likewise found in the salivary gland and synganglion at high concentrations. For most of the amino acids there is insufficient information to correlate these titres (and fluctuations of titres) to neuromodulatory functions. It is possible, however, that the high GABA titre in the salivary gland of engorged ticks is correlated with an augmented level of fluid secretion.Deceased: Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.     

Variations circadiennes des acides aminés libres de l'hemolymphe de Penaeus japonicus

The non-essential free amino acids of Peneaus japonicus hemolymph (asp, ser, glu, pro, gly, tyr, arg, ala, cys, tau) are more common than the essential ones: 750 pmol μl^?1 of hemolymph vs 330 pmol. Under a light-dark (L-D); 12-12 photoperiod, tricircadian variations of males or tetracircadian variations of females are more pronounced for non-essential amino acids then for essential ones. In the first case, free amino acid concentrations of hemolymph can be multiplied by a factor of three, and in the second case by a factor of six; but circadian variations of females are greater than those of males. Differences between the maximum and minimum of essential free amino acid concentrations of male and female hemolymph are more frequent than for non-essential amino acids. A differences of 2 h between the minimum of essential and non-essential amino acid concentrations in males only appeared during the afternoon. The more concentrated free amino acids in P. japnicus hemolymph are glycine, proline, histidine, and alanine; the less concentrated are lysine, cysteine and glutamic acid while others, like leucine, isoleucine, phenylalanine and tyrosine can only be estimated at 10.00 and 24.00 h.     

Hormone Profiling by LC-QToF-MS/MS in Dormant <Emphasis Type="Italic">Macadamia integrifolia</Emphasis>: Correlations with Abnormal Vertical Growth

A method for analyzing multiple plant hormone groups in small samples with a complex matrix was developed to initiate a study of the physiology of abnormal vertical growth (AVG) in Macadamia integrifolia (cv. HAES344). Cytokinins (CKs), gibberellins (GAs), abscisic acid (ABA), and auxins were detected in xylem sap and apical and lateral buds using high-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (LC-QToF-MS/MS). The extraction method separated compounds with high sensitivity in positive (CKs) and negative (ABA, auxins, GAs) modes of QToF-MS/MS. CK profiles differed in xylem sap and apical and lateral buds irrespective of AVG symptoms. Trans-zeatin riboside (t-ZR) was dominant in sap of normal and AVG trees (∼4 and 6 pmol g⁻¹ FW, respectively). In apical buds isopentenyl adenine (iP) (∼30 pmol g⁻¹ FW) was the most abundant CK, and in lateral buds trans-zeatin (t-Z) (22–24 pmol g⁻¹ FW) and iP (24–30 pmol g⁻¹ FW) were the most abundant. t-Z levels of AVG trees were higher in apical buds (13.88 vs. 6.6 pmol g⁻¹ FW, p < 0.05) and lower in sap (0.16 vs. 0.51 pmol ml⁻¹, p < 0.005) compared to normal trees. ABA in lateral buds was 1.9 times higher (p < 0.001) in AVG. IAA was below quantification, whereas indole-3-butyric acid (IBA) was consistently present. GA₇ was the dominant GA in apical and lateral buds of all trees (100–150 pmol g⁻¹ FW). GA_{3, 4, & 9} were consistently present at low concentrations (<12 pmol g⁻¹ FW) in buds. GAs_{1, 3, & 9} were detected in xylem sap at low concentrations (<0.5 pmol g⁻¹ FW). Differences in sap amino acids (AA) were also assessed. In sap from AVG trees, asparagine and glutamine increased significantly (p < 0.05) in their contribution to total AA. Potential AVG hormone correlations are discussed.     

Femtomole detection of amino acids and dipeptides by gas chromatography—negative-ion chemical ionization mass spectrometry following alkylation with pentafluorobenzyl bromide

Amino acids and di- and tripeptides were derivatized by extractive alkylation using pentafluorobenzyl bromide (PFBBr) followed by reaction with heptafluorobutyric anhydride (HFBA) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). Good chromatographic separation and the formation of intense diagnostic ions were observed for the derivative when examined using gas chromatography—negative-ion chemical ionization mass spectrometry (GC—NICI-MS). Of the 20 amino acids investigated, only Arg and Glu could not be detected by this method. Also, dipeptides which included neutral amino acid residues were derivatized with more success than those containing either acidic or basic residues. Each of the amino acids or dipeptides formed one major derivative with the exception of Asn which formed two derivatives with either one or two HFB groups. This derivatization method was optimized with respect to the reaction temperature, reaction time, and choice of derivatizing reagents. Recoveries of derivatized [³H]-labeled Phe, Lys, and Thr were 76, 55, and 34%, respectively. Linearity was observed from 10 to 2000 pg of Ala per vial; selected-ion monitoring provided a detection limit of less than 150 fg with a signal-to-noise (S/N) ratio of 80 to 1. This method has proven to work well with urine samples and shows great promise for the detection of small peptides at low levels.     

Parity-Violating Energy Shifts of Murchison L-Amino Acids are Consistent with an Electroweak Origin of Meteorite L-Enantiomeric Excesses

In 1996, four α-methyl amino acids in the Murchison meteorite—L-isovaline, L-α-methylnorvaline, L-α-methyl-allo-isoleucine and L-α-methyl-isoleucine—were found to show significant enantiomeric excesses of the L form, ranging from 2% to 9%. Their deuterium to hydrogen isotope ratios suggest they formed in the pre-solar interstellar gas cloud rather than during a later aqueous processing phase on the asteroid parent body. In this paper we apply the techniques of the preceding two papers to compute the parity-violating energy shifts of these amino acids. We find that, in the gas phase, the PVESs of the neutral L forms of all four Murchison α-methyl amino acids are decisively negative, and there is even some correlation between the magnitudes of the L-excesses and the magnitudes of the PVESs—all of which is at least consistent with an electroweak origin of the Murchison enantiomeric excesses.     

Molecular model of an alpha-helical prion protein dimer and its monomeric subunits as derived from chemical cross-linking and molecular modeling calculations

Prions are the agents of a series of lethal neurodegenerative diseases. They are composed largely, if not entirely, of the host-encoded prion protein (PrP), which can exist in the cellular isoform PrP^C and the pathological isoform PrP^Sc. The conformational change of the α-helical PrP^C into β-sheet-rich PrP^Sc is the fundamental event of prion disease. The transition of recombinant PrP from a PrP^C-like into a PrP^Sc-like conformation can be induced in vitro by submicellar concentrations of SDS. An α-helical dimer was identified that might represent either the native state of PrP^C or the first step from the monomeric PrP^C to highly aggregated PrP^Sc. In the present study, the molecular structure of these dimers was analyzed by introducing covalent cross-links using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. Inter- and intramolecular bonds between directly neighboured amino groups and carboxy groups were generated. The bonds formed in PrP dimers of recombinant PrP (90-231) were identified by tryptic digestion and subsequent mass spectrometric analysis. Intra- and intermolecular cross-links between N-terminal glycine and three acidic amino acid side chains in the globular part of PrP were identified, showing the N-terminal amino acids (90-124) are not as flexible as known from NMR analysis. When the cross-linked sites were used as structural constraint, molecular modeling calculations yielded a structural model for PrP dimer and its monomeric subunit, including the folding of amino acids 90-124 in addition to the known structure. Molecular dynamics of the structure after release of the constraint indicated an intrinsic stability of the domain of amino acids 90-124.     

An evaluation of the role of cytokinins in the development of abnormal inflorescences in oil palms (Elaeis guineensis Jacq.) regenerated from tissue culture

Tissue cultures and regenerant plants from cell lines producing palms with normal and abnormal flowers were analyzed for cytokinin content and compared with zygotic embryos and seedlings. Immature inflorescences at the critical stage of flower development dissected from normal and abnormal palms were also analyzed. High performance liquid chromatography (HPLC)/radioimmunoassay and HPLC/enzyme-linked immunosorbent assay methods were used over a period of several years to measure the isoprenoid cytokinins. The results of analyses of endogenous aromatic cytokinins, present at comparable levels, will be reported separately. Oil palm cultures and regenerant plants contained relatively high concentrations of the 9-glucosides of isopentenyladenine ([9G]iP) and zeatin ([9G]Z). The predominant biologically active isoprenoid cytokinin present was zeatin riboside ([9R]Z), with lesser amounts of isopentenyladenine (iP) and isopentenyladenosine ([9R]iP). There was evidence of small amounts of dihydrozeatin compounds, but high concentrations (mainly as dihydrozeatin-9-glucoside ([9G]DHZ)) were confined to the haustorium of the zygotic embryo. Callus tissue contained very low concentrations of cytokinin. Frequently only [9G]iP could be detected, at about 1 pmol · g^-1 fresh weight, with [9R]Z at less than 0.05 pmol · g^-1. In comparison, nodular embryogenic tissues in vitro contained between 30 and 1,500 pmol · g^-1 of [9G]iP, 5–50 pmol · g^-1 of [9G]Z, and up to 12 pmol · g^-1 of [9R]Z. Shoots of regenerant plantlets and seedlings contained lower concentrations of [9G]iP (3–30 pmol · g^-1), although this was still the predominant cytokinin. [9R]Z and [9G]Z were present at between 2 and 15 pmol · g^-1, with iP at 1–5 pmol · g^-1 and [9R]iP at between 1 and 12 pmol · g^-1. Seedlings contained similar amounts with the exception of a lower [9G]iP content (5–10 pmol · g^-1) and more [9R]iP (10–20 pmol · g^-1). Root tissues of ramets contained significantly higher concentrations of [9G]iP than shoots. Comparison of two isogenic lines of one clone giving rise to normal and abnormal palms showed significantly higher concentrations of [9R]Z and [9G]Z in the normal than in the abnormal line and, in embryoids only, higher [9G]iP in the normal line. In all other cases the between-done differences were greater than any normal/abnormal differences. There was a general tendency for increased concentrations of [9G]iP in abnormal lines and for this compound to be in a higher concentration in embryoids and plants derived from culture than in zygotic embryos and seedlings. Analysis of cytokinins in immature female inflorescences of normal and abnormal palms of a single clone showed the abnormal inflorescences to have higher concentrations of [9R]Z and [9R]DHZ and less [9G]Z than the normal inflorescences at comparable stages of development.Abbreviations HPLC high performance liquid chromatography - [9G]iP 9-glucoside of isopentenyladenine - [9G]Z 9-glucoside of zeatin - [9R]Z zeatin riboside - iP isopentenyladenine - [9R]iP isopentenyladenosine - [9G]DHZ dihydrozeation-9-glucoside - ELISA enzyme-linked radioimmunosorbentassay - ANOVAR analysis of variance     

Identification of endogenous acyl amino acids based on a targeted lipidomics approach

Using a partially purified bovine brain extract, our lab identified three novel endogenous acyl amino acids in mammalian tissues. The presence of numerous amino acids in the body and their ability to form amides with several saturated and unsaturated fatty acids indicated the potential existence of a large number of heretofore unidentified acyl amino acids. Reports of several additional acyl amino acids that activate G-protein coupled receptors (e.g., N-arachidonoyl glycine, N-arachidonoyl serine) and transient receptor potential channels (e.g., N-arachidonoyl dopamine, N-acyl taurines) suggested that some or many novel acyl amino acids could serve as signaling molecules. Here, we used a targeted lipidomics approach including specific enrichment steps, nano-LC/MS/MS, high-throughput screening of the datasets with a potent search algorithm based on fragment ion analysis, and quantification using the multiple reaction monitoring mode in Analyst software to measure the biological levels of acyl amino acids in rat brain. We successfully identified 50 novel endogenous acyl amino acids present at 0.2 to 69 pmol g⁻¹ wet rat brain.     

Studies on the Reaction of Dipeptides with Glyoxal

The reaction of various dipeptides with glyoxal at 100°C, pH 5.0 was studied. Carbon dioxide, ammonia, amino acids and aldehydes were detected from the reaction solutions. Besides, a series of new pyrazinones—2-(3′-alkyl-2′-oxo-pyrazin-1′-yl)alkyl acid—were isolated, and their chemical structures were confirmed by UV, IR, MS and NMR spectra. These pyrazinones seem to play a role in the browning of the reaction.

In the reaction with glyoxal, acetaldehyde and glucose, reactivity of peptides was proved to be much higher than that of amino acids.

The reaction mechanism of dipeptides with glyoxal was also proposed.     

Gas chromatography-mass spectrometry evidence for several endogenous auxins in pea seedling organs

Qualitative analysis by gas chromatography-mass spectrometry (GC-MS) of the auxins present in the root, cotyledons and epicotyl of 3-dold etiolated pea (Pisum sativum L., cv. Alaska) seedlings has shown that all three organs contain phenylacetic acid (PAA), 3-indoleacetic acid (IAA) and 4-chloro-3-indoleacetic acid (4Cl-IAA). In addition, 3-indolepropionic acid (IPA) was present in the root and 3-indolebutyric acid (IBA) was detected in both root and epicotyl. Phenylacetic acid, IAA and IPA were measured quantitatively in the three organs by GC-MS-single ion monitoring, using deuterated internal standards. Levels of IAA were found to range from 13 to 115 pmol g^-1 FW, while amounts of PAA were considerably higher (347–451 pmol g^-1 FW) and the level of IPA was quite low (5 pmol g^-1 FW). On a molar basis the PAA:IAA ratio in the whole seedling was approx. 15:1.Abbreviations IAA 3-indoleacetic acid - 4Cl-IAA 4-chloro-3-indoleacetic acid - IBA 3-indolebutyric acid - IPA 3-indolepropionic acid - PAA phenylacetic acid - GC-MS gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - PFB pentafluorobenzyl ester - PFBBr pentafluorobenzyl bromide - SIM single-ion monitoring - TMSI trimethylsilyl ester     

Antioxidant defences in marine fish—II. Elasmobranchs

1. Tissues from four ray species and two shark species were examined concerning Superoxide dismutase and catalase content, and malonaldehyde and tocopherol concentrations.2. Livers displayed the highest Superoxide dismutase and catalase content in all species examined. Sharks exhibited higher mean enzyme contents than rays (3.6 and 2.4 nmol SOD g⁻¹ wet tissue, 185 and 120 pmol catalase g⁻¹ wet tissue).3. Tocopherol was detected in liver from all species, in kidney and in ovary from one ray and one shark species, and in shark cristaline in a range of 0.1–4.8 nmol g⁻¹ wet tissue.4. The content of antioxidant enzymes in elasmobranchs was lower than that of teleosts, and seems to follow the overall metabolic oxygen consumption or activity level from each fish major taxonomic group.5. Liver peroxidation as measured as MDA/TBARS concentration, revealed very high values (range of 1.5–4.5 μmoles g⁻¹ wet tissue), approximately one order of magnitude higher when compared with mammals.     

Kinetic Properties of a Dipeptidase from Streptococcus cremoris

Some kinetic properties of a dipeptidase purified from a cell-free extract of Streptococcus cremoris H 61 were investigated. The Km values of this enzyme for various dipeptides were divided into 3 groups. Group 1 comprised mainly of neutral dipeptides, such as Leu-Gly, Leu-Leu and Leu-Ala, which had relatively low Km values (in the range 4.0-6.6 mm). Group 2 consisted of dipeptides with aromatic large amino acids either at the N- or C-terminal positions, like Leu-Phe, Phe-Ala and Leu-Tyr, which had very low Km values (in the range 1.0-2.4 mm). Group 3 was made up by dipeptides with acidic or basic amino acids at the N-terminals; His-Ala and Glu-Val were typical of this group. These had very high Km values (in the range 10–20 mm). Substantial substrate competition was found to exist in the presence of His-Ala. Bestatin inhibited the enzyme competitively with Leu-Gly and was found to have an apparent Ki value of 3.0 × 10^?8 m for the enzyme. Further, the enzyme was completely inhibited by EDTA at a concentration of 2.0 × 10^?5 m. On the other hand, once the activity was inhibited by EDTA, it could be restored by Co²⁺ and Zn²⁺ in the acidic pH side, and by Ca²⁺ and Mn²⁺ in the alkaline pH side.     

Conformational analysis of short polar side-chain amino-acids through umbrella sampling and DFT calculations

Molecular and quantum mechanics calculations were carried out in a series of tripeptides (GXG, where X?=?D, N and C) as models of the unfolded states of proteins. The selected central amino acids, especially aspartic acid (D) and asparagine (N) are known to present significant average conformations in partially allowed areas of the Ramachandran plot, which have been suggested to be important in unfolded protein regions. In this report, we present the calculation of the propensity values through an umbrella sampling procedure in combination with the calculation of the NMR J-coupling constants obtained by a DFT model. The experimental NMR observations can be reasonably explained in terms of a conformational distribution where PP_II and β basins sum up propensities above 0.9. The conformational analysis of the side chain dihedral angle (χ₁), along with the computation of ³J(H^αH^β), revealed a preference for the g _? and g ₊ rotamers. These may be connected with the presence of intermolecular H-bonding and carbonyl–carbonyl interactions sampled in the PP_II and β basins. Taking into account all those results, it can be established that these residues show a similar behavior to other amino acids in short peptides regarding backbone φ,ψ dihedral angle distribution, in agreement with some experimental analysis of capped dipeptides.     

Mechanism of lysosome rupture by dipeptides

Low concentrations of some neutral dipeptides, such as L -Ala-L -Ala, rapidly disrupt rat liver lysosmes. The phenomenon has been attributed to an osmotic imbalance generated by the production of amino acids in the lysosme by lysosomal dipeptidase activity. This hypothesis is challenged by testing several pairs of dipeptides available in both D - and L -forms and a range of dipeptides whose susceptibility to lysosomal dipeptidase activity is known. A good correlation was found between the lytic ability of dipeptides and their capacity to cross the lysosome membrane and be hydrolysed by lysosomal dipeptidase. The osmotic-imbalance hypothesis is critically evaluated in the light of the results and of recent information concerning the carrier-mediated transport of amino acids and dipeptides across the lysosome membrane. It is concluded that intralysosomal generation of amino acids remains the most plausible explanation of the lytic activity of dipeptides, and that the dipeptide proter(s) in the lysosome membrane must have higher K_m than the amino acid porters.     

不同甜叶菊品种叶中绿原酸类成分的比较研究

该文以14个扦插培育的甜叶菊品种叶为材料,从8种不同型号的树脂中筛选出一种合适的大孔吸附树脂对甜叶菊叶中绿原酸类成分进行纯化前处理,采用HPLC法对不同甜叶菊品种叶中所含绿原酸类成分进行比较分析。结果表明:(1)在8种不同型号的树脂中,XAD~(-1)6对甜叶菊叶中绿原酸类成分吸附-解析性能最佳。(2)经优化,上样液浓度1.20 mg·mL~(-1)、样品溶液pH 3、解析液乙醇体积分数70%时XAD~(-1)6树脂对甜叶菊叶中绿原酸类成分具有较好的纯化效果。(3) HPLC检测分析表明,在14个品种中共检测出新绿原酸、绿原酸、隐绿原酸、异绿原酸B、异绿原酸A、异绿原酸C六种绿原酸类成分,其中主要成分均为异绿原酸A、绿原酸、异绿原酸C,而在品种3、5、13、14中没有检测出异绿原酸B。(4) 14个品种中6个绿原酸类成分的含量分别为异绿原酸A 20.55~54.3 mg·g~(-1)、绿原酸17.96~32.93 mg·g~(-1)、异绿原酸C 4.15~19.49 mg·g~(-1)、新原酸0.61~4.61 mg·g~(-1)、隐绿原酸0.52~3.11 mg·g~(-1)、异绿原酸B 0.0~3.17 mg·g~(-1),6种绿原酸类成分总量为43.9~97.8 mg·g~(-1)。可见,不同品种甜叶菊叶中绿原酸类成分含量有明显差异,富含绿原酸类成分的甜叶菊品种可用于开发获取绿原酸类物质。     

MDCK microcarrier cultures: Seeding density effects and amino acid utilization

Summary The growth of Madin Darby canine kidney cells on microcarriers was studied at different cell seeding densities. Maximum growth was attained when a cell-to-bead ratio of 7∶1 was used. Under these conditions an initial concentration of above 3×10⁵ cells/ml resulted in a yield of over 2×10⁶ cells/ml in 2 d. The amino acid utilization of cells from Dulbecco's modified Eagle medium was studied under the above conditions. Eight amino acids (arg, cys, gln, ile, leu, met, ser, and val) showed rapid and near complete depletion from the medium. Five amino acids (his, lys, phe, thr, and tyr) showed limited depletion. Two amino acids (ala and gly) were released into the medium by the cells.     

Mechanism of Asymmetric Production of d-Amino Acids from the Corresponding Hydantoins by Pseudomonas sp.

The mechanism of asymmetric production of d-amino acids from the corresponding hydantoins by Pseudomonas sp. AJ-11220 was examined by investigating the properties of the enzymes involved in the hydrolysis of dl-5-substituted hydantoins. The enzymatic production of d-amino acids from the corresponding hydantoins by Pseudomonas sp. AJ-11220 involved the following two successive reactions; the d-isomer specific hydrolysis, i.e., the ring opening of d-5-substituted hydantoins to d-form N-carbamyl amino acids by an enzyme, d-hydantoin hydrolase (d-HYD hydrolase), followed by the d-isomer specific hydrolysis, i.e., the cleavage of N-carbamyl-d-amino acids to d-amino acids by an enzyme, N-carbamyl-d-amino acid hydrolase (d-NCA hydrolase).

l-5-Substituted hydantoins not hydrolyzed by d-HYD hydrolase were converted to d-form 5- substituted hydantoins through spontaneous racemization under the enzymatic reaction conditions.

It was proposed that almost all of the dl-5-substituted hydantoins were stoichiometrically and directly converted to the corresponding d-amino acids through the successive reactions of d-HYD hydrolase and d-NCA hydrolase in parrallel with the spontaneous racemization of l-5-substituted hydantoins to those of dl-form.     

Selective photodestruction of α-amino acids

A problem typically encountered in the analysis of amino acids in chemical evolution experiments and in extracts of meteorites is the large number present. For example, α-, β-, and γ-amino acids, N-mono substituted α-amino acids, and dicarboxylic α-amino acids have been found in extracts of the Murchison meteorite, and many more amino acids are present than have been positively identified by computerized gas chromatographic mass spectrometry. This paper reports an analytical method to selectively destroy the α-amino acids, with only the β- and γ-amino acids remaining in the solution. It is based on the ability of Cu²⁺ to complex with amino acids, the order of stability of these complexes being α > β > γ, = δ, = ε = 0. Aqueous solutions of α-amino acid-Cu²⁺ chelates are known to be decomposed by 254 nm light as well as by nonmonochromatic uv light, yielding a precipitate of Cu₂O. This paper shows that at 254 nm (ligand-metal charge transfer band) the rate of destruction of amino acids in Cu²⁺ aqueous solutions is in the following order, dicarboxylic α-amino acids > α-amino acids > N-monosubstituted α-amino acids β-amino acids ≈ γ-amino acids. Thus by irradiation with 254 nm light in the presence of Cu²⁺ all the amino acids can be destroyed except the β- and γ-amino acids. When almost 100% of the α-amino acids are destroyed, 80% of the β- and γ-amino acids still exist in solution. With this procedure, complex mixtures of amino acids can be simplified to make identification by gas chromatographic mass spectrometry casier.     

Identification and Quantitation of New Glutamic Acid Derivatives in Soy Sauce by UPLC/MS/MS

Glutamic acid is an abundant amino acid that lends a characteristic umami taste to foods. In fermented foods, glutamic acid can be found as a free amino acid formed by proteolysis or as a non‐proteolytic derivative formed by microorganisms. The aim of the present study was to identify different structures of glutamic acid derivatives in a typical fermented protein‐based food product, soy sauce. An acidic fraction was prepared with anion‐exchange solid‐phase extraction (SPE) and analyzed by UPLC/MS/MS and UPLC/TOF‐MS. α‐Glutamyl, γ‐glutamyl, and pyroglutamyl dipeptides, as well as lactoyl amino acids, were identified in the acidic fraction of soy sauce. They were chemically synthesized for confirmation of their occurrence and quantified in the selected reaction monitoring (SRM) mode. Pyroglutamyl dipeptides accounted for 770 mg/kg of soy sauce, followed by lactoyl amino acids (135 mg/kg) and γ‐glutamyl dipeptides (70 mg/kg). In addition, N‐succinoylglutamic acid was identified for the first time in food as a minor compound in soy sauce (5 mg/kg).     

Optical Rotatory Dispersion and Circular Dichroism of Amino Acid Hydantoins

Optical rotatory dispersion (ORD) and circular dichroism (CD) of 17 amino acid hydantoins were measured between 190 and 600 nm. Most of hydantoins exhibited the negative Cotton effect which showed the trough between 238 and 245 nm. The negative trough of CD was also observed between 212 and 236 nm. The Cotton effect of hydantoins was attributable to n→π^* transition of carbonyl group at C-4 of hydantoin ring.