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Riboflavin-induced Type 1 photo-oxidation of tryptophan using a high intensity 365 nm light emitting diode
摘要： The mechanism of photo-oxidation of tryptophan (Trp) sensitized by riboflavin (RF) was examined employing high concentrations of Trp and RF, with a high intensity 365 nm light emitting diode (LED) source under N2, 20% and 100% O2 atmospheres. Dimerization of Trp was a major pathway under the N2 atmosphere, though this occurred with a low yield (DφTrp = 5.9 x 10-3), probably as a result of extensive back electron transfer reactions between RF●- and Trp(H)●+. The presence of O2 decreased the extent of this back electron transfer reaction, and the extent of Trp dimerization. This difference is attributed to the formation of O2●- (generated via electron transfer from RF●- to O2) which reacts rapidly with Trp● leading to extensive consumption of the parent amino acid and formation of peroxides and multiple other oxygenated products (N-formylkynurenine, alcohols, diols) of Trp, as detected by LC-MS. Thus, it appears that the first step of the Type 1 mechanism of Trp photo-oxidation, induced by this high intensity 365 nm light source, is an electron transfer reaction between the amino acid and 3RF, with the presence of O2 modulating the subsequent reactions and the products formed, as a result of O2●- formation. These data have potential biological significance as LED systems and RF-based treatments have been proposed for the treatment of pathological myopia and keratitis.
关键词： type 1/type 2 mechanisms,dimers,LED,N-formylkynurenine,trimers,riboflavin,photo-oxidation,electron transfer,photobleaching,tryptophan,triplet excited state
更新于2025-09-23 15:21:21
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Synthesis, characterization, and fluorescence study of tryptone-self-assembled and Zn(II)-coordinated nanoparticles
摘要： Peptides/amino acids are biodegradable and biocompatible and have been used as suitable biomaterials for many bioengineering and medical applications in the last few decades. However, sometimes they show very limited intrinsic optical properties when used as optical imaging probes for biological diagnostics and target-based drug monitoring applications. Here we synthesized novel tryptone-self-assembled and Zn(II)-coordinated nanoparticles (TZFNPs), which shifted the intrinsic fluorescence emission peak from ultraviolet (270 nm) of tryptone to the visible wavelength (470 nm). Furthermore, when coordinated with 4-chloro-7-nitrobenzofurazan (NBD-Cl), a fluorogenic reagent, the fluorescence signals of our TZFNPs were further enhanced directly and in the cellular environment as well. We also studied the fluorescent signals of these TZFNPs after transferring them into the intracellular space of U2OS and HeLa cell lines. These fluorescent nanoparticles are intrinsically fluorescent and suitable for bioimaging. We hope they will pave the new way for further applications in medical sciences from diagnostics to clinical trials.
关键词： Tryptophan,Nanoparticle,Tryptone,Fluorescence,Self-assembly,Optical imaging
更新于2025-09-23 15:19:57
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Impact of Tryptophan Oxidation in Complementarity-Determining Regions of Two Monoclonal Antibodies on Structure-Function Characterized by Hydrogen-Deuterium Exchange Mass Spectrometry and Surface Plasmon Resonance
摘要： Purpose Tryptophan’s (Trp) unique hydrophobic and structural properties make it an important antigen binding motif when positioned in complementarity-determining regions (CDRs) of monoclonal antibodies (mAbs). Oxidation of Trp residues within the CDR can deleteriously impact antigen binding, particularly if the CDR conformation is altered. The goal of this study was to evaluate the conformational and functional impact of Trp oxidation for two mAb subtypes, which is essential in determining the structure-function relationship and establishing appropriate analytical control strategies during protein therapeutics development. Methods Selective Trp oxidation was induced by 2,2′-Azobis(2-amidinopropane) dihydrochloride (AAPH) treatment in the presence of free methionine (Met). The native and chemically oxidized mAbs were characterized by hydrogen-deuterium exchange mass spectrometry (HDX-MS) for conformational changes and surface plasmon resonance (SPR) for antigen-antibody binding. Results Treatment of mAbs with AAPH selectively oxidized solvent accessible Trp residues. Oxidation of Trp within or in proximity of CDRs increased conformational flexibility in variable domains and disrupted antigen binding. Conclusions Trp oxidation in CDRs can adversely impact mAbs’ conformation and antigen binding. Trp oxidation should be carefully evaluated as part of critical quality attribute assessments. Oxidation susceptible Trp should be closely monitored during process development for mAbs to establish appropriate analytical control for manufacturing of drug substance and drug product.
关键词： Tryptophan oxidation,surface plasmon resonance,complementarity-determining region,hydrogen-deuterium exchange mass spectrometry,monoclonal antibody
更新于2025-09-23 15:19:57
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A novel surface plasmon resonance sensor based on a functionalized graphene oxide/molecular-imprinted polymer composite for chiral recognition of <scp>l</scp> -tryptophan
摘要： Herein, a novel surface plasmon resonance (SPR) sensor based on a functionalized graphene oxide (GO)/molecular-imprinted polymer composite was developed for the chiral recognition of L-tryptophan (L-Trp). The composite's recognition element was prepared via a facile and green synthesis approach using polydopamine as both a reducer of GO and a functional monomer as well as a cross-linker for molecular imprinting. The composite was characterized via Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. After attaching the composite onto the gold surface of an SPR chip, the sensor was characterized using contact-angle measurements. The sensor exhibited excellent selectivity and chiral recognition for the template (i.e., L-Trp). Density functional theory computations showed that the difference in hydrogen bonding between the composite element and L-Trp and D-Trp played an important role in chiral recognition.
关键词： molecular-imprinted polymer,graphene oxide,surface plasmon resonance,L-tryptophan,chiral recognition
更新于2025-09-19 17:15:36
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Sulfur and nitrogen coa??doped graphene quantum dota??assisted chemiluminescence for sensitive detection of tryptophan and mercury (II)
摘要： A simple one-step thermal treatment to prepare strong fluorescent sulfur and nitrogen co-doped graphene quantum dots (SN-GQD) using citric acid and L-cysteine as precursors was developed. The ultra-weak chemiluminescence (CL) from the reaction of hydrogen peroxide (H2O2) and periodate (IO4?) was significantly enhanced by SN-GQD in acidic medium. The enhanced CL was induced by excited-state SN-GQD (SN-GQD*), which was produced from the transfer energy of (O2)2* and 1O2 to SN-GQD and recombination of oxidant-injected holes and electrons in SN-GQD. In the presence of tryptophan (Trp), the CL intensity of the SN-GQD–H2O2–KIO4 system was greatly diminished. This finding was used to design a novel method for determination of Trp in the linear range 0.6–20.0 μM, with a limit of detection (LOD) of 58.0 nM. Furthermore, Hg2+ was detectable in the range 0.1–9.0 μM with a LOD of 64.0 nM, based on its marked enhancement of the SN-GQD–H2O2–KIO4 CL system. The proposed method was successfully applied to detect Trp in milk and human plasma samples and Hg2+ in drinking water samples, with recoveries in the range 95.7–107.0%.
关键词： tryptophan,S,N co-doped graphene quantum dots,chemiluminescence,mercury (II)
更新于2025-09-16 10:30:52
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Enabling highly efficient photocatalytic hydrogen generation and organics degradation <i>via</i> a perovskite solar cell-assisted semiconducting nanocomposite photoanode
摘要： The halogenase gene spmH was putatively involved in the biosynthesis of spiroindimicins/indimicins (SPMs/IDMs), a group of chlorinated tryptophan dimers (TDs) from deep-sea-derived Streptomyces sp. SCSIO 03032. Inactivation of spmH led to six deschloro-analogues of TDs, including four new compounds SPMs G (1) and H (2), and IDMs F (3) and G (4). The structures and absolute configurations of 1–4 were unambiguously determined by the combination of extensive spectroscopic analysis, single-crystal X-ray diffraction and quantum chemical ECD calculations. Compounds 1 and 2 exhibited moderate cytotoxic activities against four cancer cell lines. Additionally, SpmH was biochemically characterized in vitro as an L-tryptophan 5-halogenase.
关键词： L-tryptophan 5-halogenase,biosynthesis,tryptophan dimers,cytotoxic activities,halogenase
更新于2025-09-11 14:15:04
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Capillary electrophoresis/visible‐LED induced fluorescence of tryptophan: What's new?
摘要： Tryptophane (Trp) labelled by 3-(4-carboxybenzoyl)-2-quinolinecarboxaldehyde (CBQCA) is very dif?cult to identify using CE and ?uorescence detection (480 nm). Why in this article some mass spectrometry experiments show that Trp is really labelled by CBQCA as Leucine (Leu)? If the maximum of UV absorption ((cid:2)max) is the same between Leu-CBQCA and Trp-CBQCA, the molar extinction coef?cient is around 2 fold higher for Trp-CBQCA. The ?uorescence of the Leu-CBQCA derivative is 50 times more important than for Trp-CBQCA. The addition of 7.5 mM of (cid:3)-cyclodextrin ((cid:3)-CD) was found to be a good mean to improve 2.1 fold the sensitivity of the Trp-CBQCA ?uorescence. Using a buffer containing SDS and (cid:3)-CD in CE, a LOD of 0.7 μM of L-Trp can be reached and the ratio of the intensities between Leu, Isoleucine, Valine, Trp is 100, 21, 15, 1. Negative ESI/MS and MS/MS of the labeled amino acids show that a loss of the carboxylate function takes place. In the presence of two enantiomers of Trp-CBQCA, we have shown that this decarboxylation is not due to the derivatization process in the solution but rather occurs in the source of the mass spectrometer.
关键词： Tryptophan,Capillary electrophoresis,Fluorescence,Biomolecule,3-(4-carboxybenzoyl)-2-quinolinecarboxaldehyde
更新于2025-09-11 14:15:04
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Smart Plasmonic Nanozyme Enhances Combined Chemo-Photothermal Cancer Therapy and Reveals Tryptophan Metabolic Apoptotic Pathway
摘要： The tumor microenvironment regulation is considered as an intelligent strategy for cancer therapeutics, but the related metabolic pathways of cell apoptosis still remains a great challenge. Herein, by applying multifunctional carbon dot-decorated Ag/Au bimetallic nanoshells (CDs-Ag/Au NSs, CAANSs) nanoprobes as smart plasmonic nanozymes for combined chemo-photothermal cancer therapy, we achieved a high efficiency in cancer cell therapy and revealed a tryptophan metabolic apoptotic pathway. In addition to high photothermal conversion efficiency, the CAANSs can act as a smart nanozyme to catalyze intracellular H2O2 to the cytotoxic reactive oxygen species (ROS) of superoxide anion (·O2-) in response to mild acidic cancerous cell microenvironment to damage cellular DNA. More importantly, the tryptophan metabolic pathway during the combined chemo-photothermal therapy has been revealed that the tryptophan participates in oxidative stress process, which can be decomposed to produce H2O2 and further formed into superoxide anion to kill cells under the catalytic nanomedicine process. The current work provides an effective platform for cancer therapeutics and is promising for cancer-related molecular biology studies.
关键词： Tryptophan Metabolic Apoptotic Pathway,Smart Plasmonic Nanozyme,Tumor Microenvironment,Chemo-Photothermal Cancer Therapy,Reactive Oxygen Species
更新于2025-09-11 14:15:04
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Deep UV plasmonic enhancement of single protein autofluorescence in zero-mode waveguides
摘要： Single molecule detection provides detailed information about molecular structures and functions, but it generally requires the presence of a fluorescent marker which can interfere with the activity of the target molecule or complicate the sample production. Detecting a single protein with its natural UV autofluorescence is an attractive approach to avoid all the issues related to fluorescence labelling. However, the UV autofluorescence signal from a single protein is generally extremely weak. Here, we use aluminum plasmonics to enhance the tryptophan autofluorescence emission of single proteins in the UV range. Zero-mode waveguides nanoapertures enable observing the UV fluorescence of single label-free β-galactosidase proteins with increased brightness, microsecond transit times and operation at micromolar concentrations. We demonstrate quantitative measurements of the local concentration, diffusion coefficient and hydrodynamic radius of the label-free protein over a broad range of zero-mode waveguide diameters. While the plasmonic fluorescence enhancement has generated a tremendous interest in the visible and near-infrared parts of the spectrum, this work pushes further the limits of plasmonic-enhanced single molecule detection into the UV range and constitutes a major step forward in our ability to interrogate single proteins in their native state at physiological concentrations.
关键词： plasmonics,ultraviolet UV,single molecule fluorescence,nanophotonics,zero-mode waveguide,tryptophan autofluorescence
更新于2025-09-11 14:15:04
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Monitoring of Fluorescence Characteristics of Satsuma Mandarin (Citrus unshiu Marc.) during the Maturation Period
摘要： Monitoring the maturation process of Satsuma mandarin (Citrus unshiu Marc.) by determining the soluble solids (SS) and acid content non-destructively is needed. Fluorescence components potentially offer such means of accessing fruit maturity characteristics in the orchard. The aim of this study was to determine the potential of ?uorescence spectroscopy for monitoring the stage of citrus maturity. Four major ?uorescent components in peel and/or ?esh were found including chlorophyll-a (excitation (Ex) 410 nm, emission (Em) 675 nm) and chlorophyll-b (Ex 460 nm, Em 650 nm),polymethoxy?avones (PMFs) (Ex 260 nm and 370 nm, Em 540 nm), coumarin (Ex 330 nm, Em 400 nm), and a tryptophan-like compound (Ex 260 nm, Em 330 nm). Our results indicated a signi?cant (R2 = 0.9554) logarithmic ratio between tryptophan-like compoundsExEm and chlorophyll-aExEm with the SS:acid ratio. Also, the log of the ratio of PMFs from the peel (ExExEm was signi?cantly correlated with the SS:acid ratio (R2 = 0.8207). While the latter correlation was not as strong as the former, it does demonstrate the opportunity to develop a non-destructive ?eld measurement of ?uorescent peel compounds as an indirect index of fruit maturity.
关键词： ?uorescence,soluble solid and acid ratio,tryptophan-like,chlorophyll-a,chlorophyll-b,polymethoxy?avones,maturity index
更新于2025-09-10 09:29:36