Tryptophan trp

l-Glycine (Gly), alanine (Ala), γ-aminobutyric acid (GABA), l-aspartic acid (Asp), l-glutamic acid (Glu), L-methionine (Met), l-phenylalanine (Phe), tyrosine (Tyr), d-serine (d-Ser), homocysteine (Hcy), N-acetylaspartic acid (Naa), and tryptophan (Trp) were purchased from Sigma Aldrich Co., Ltd. (Shanghai, China). Formic acid (purity 99%) was obtained from Roe Scientific Inc. (Newark, DE, USA). All solutions were prepared using LC-MS Ultra High Purity water and LC-MS-grade acetonitrile (Tedia Company Inc., Fairfield, OH, USA). The I.S. (acrylamide-d₃) was purchased from Toronto Research Chemicals Inc. (Toronto, ON, Canada).
Galangin with 98.0% purity was purchased from Nanjing Zelang Medical Technology Co., Ltd (Nanjing, China). The stock solution was prepared by dissolving the galangin power in sterile saline (containing 5% polysorbate 80). EGb761 (Folium Ginkgo Extract), used as a positive control to explore the efficacy of galangin, was purchased from Dr. Willmar Schwabe (Karlsruhe, Germany).

Tryptophan (TRP), L-kynurenine sulfate (KYN), and kynurenic acid (KYNA) were obtained from Sigma-Aldrich, Co. (St. Louis, MO, USA) and used as a standard. HPLC-grade chemicals were purchased from J.T. Baker Chemicals (Aventor Performance Materials Poland S.A., Gliwice, Poland) or Sigma-Aldrich. TRP, KYN, and KYNA were analyzed by high-performance liquid chromatography (HPLC), according to the protocol of Zhao et al. (2010) [56 (link)], with minor modifications. Briefly, each serum sample was added 6% HClO₄ and centrifuged at 12,000× g for 30 min at 4 °C. The resulting supernatant was applied to an HPLC system consisting of the Dionex P680 Pump, UltiMate 3000 Autosampler with column compartment, RS Variable Wavelength UltiMate 3000 Detector, and RF 2000 Fluorescence Detector (Dionex, Sunnyvale, CA, USA). An Agilent HC-C18 column (250 × 4.6 mm i.d.; 5-µm particle size) was used. The mobile phase was composed of 20 mM sodium acetate, 5 mM zinc acetate, and 4% acetonitrile; the flow rate was 1.0 mL/min. Detectors were set at wavelengths 250 nm for TRP, 365 nm for KYN, and at excitation wavelength of 348 nm and emission at 398 nm for KYNA determination. Control of the HPLC system and data analysis were performed with the Chromeleon software (Dionex^TM Chormeleon^TM version 7.2.6 (10049), serial number 117836).

Water-soluble porphyrins: disodium salt of 3,8-di (1-methoxyethyl) deuteroporphyrin IX (dimegin, DMG, synthesized by G.V. Ponomarev at the Institute of Biological and Medicinal Chemistry, Moscow, Russia) and three sodium salt of chlorin e6 (Ce6, Frontier scientific Inc., Logan, UT, USA), and hydrophobic porphyrins: 5,10,15,20-tetraphenylporphyrin (TPP, synthesized by G.V. Ponomarev at the Institute of Biological and Medicinal Chemistry, Moscow, Russia) and fluorinated tetraphenyl porphyrin-5,10,15,20-tetrakis (pentafluorophenyl) porphyrin (TPPF20, (Sigma-Aldrich, Saint Louis, MO, USA)) were used as photosensitizers. The structures of the photosensitizers are shown in Figure 1.
Poly-N-vinylpyrrolidone (PVP, 4 × 10⁴ M, Sigma-Aldrich, Saint Louis, MO, USA) and a ternary block copolymer of ethylene and propylene oxide, Pluronic F127 (F127, 12.6 × 10⁻³ M, BASF, Ludwigshafen, Germany), are well-studied and widely used in medicine. Chitosan (CT₁₀₀) was purchased from Sigma-Aldrich (#448869) with a Mw = (50–190) × 10³ Da and a deacetylation degree DA = 75–85% and was used without additional purification (Sigma-Aldrich, Saint Louis, MO, USA). Chitosan was used as a biologically active polysaccharide, while tryptophan (Trp, Sigma-Aldrich, Saint Louis, MO, USA) was utilized as a substrate. The structures of polymers are shown in Figure 2.

l- and d-enantiomers of methionine (Met), phenylalanine (Phe), and tryptophan (Trp) with ≥98% optical purity were purchased from Sigma-Aldrich Sweden AB (Stockholm, Sweden) and used without further purification. (R)-2-butanol, (S)-2-butanol, a racemic mixture of (R)- and (S)-2-butanol enantiomers, and (S)-1-phenylethanol of 99% purity were obtained from Sigma-Aldrich and used without further purification as target gases. The amino acids were dissolved in a water/methanol/formic acid mixture (49:49:2 v/v/v) at a concentration of 0.04 mM.

Tryptophan (Trp, Sigma-Aldrich, St. Louis, MO, USA) was dissolved in water to 10 mg/mL as a stock. Auxin (IAA; Sigma-Aldrich, St. Louis, MO, USA): stock concentration of 50 mM in ethanol. 5-(4-chlorophenyl)-4H-1, 2, 4-triazole-3-thiol (yucasin; Sigma–Aldrich, St. Louis, MO, USA): stock concentration of 0.5 M in DMSO.

Chitosan oligosaccharide lactate 5 kDa (Chit5), activated PEG 5 kDa (N-succinimidyl ester of mono-methoxy poly(ethylene glycol)), ovalbumin, tryptophan (Trp) and 1 M 2,4,6-trinitrobenzenesulfonic acid (TNBS) were purchased from Sigma-Aldrich (St. Louis, MI, USA). Congo red and malachite green were purchased from Reachem, Russia. 1-pyrenebutanoic acid succinimidyl ester was bought from Invitrogen (Molecular Probes, Eugene, OR, USA).

Bovine serum albumin (BSA, min. 98%, from Sigma-Aldrich, St. Louis, MO, USA) and tryptophan (Trp, 98%, from Sigma-Aldrich), tyrosine (Tyr, 98%, from Sigma-Aldrich), phenylalanine (Phe, 98%, from Sigma-Aldrich) and phosphate buffer solution (pH 7.4) were used as received. The methyl o-methoxy p-methylaminobenzoate–I and methyl o-hydroxy p-methylaminobenzoate-II have been synthesized and purified by Gormin [44 (link),45 (link),46 (link)]. The purity of dyes was controlled by thin layer chromatography.