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Imaging is increasingly used to detect and monitor bacterial infection. Both anatomic (X-rays, computed tomography, ultrasound, and MRI) and nuclear medicine ([111In]-WBC SPECT, [18F]FDG PET) techniques are used in clinical practice but lack specificity for the causative microorganisms themselves. To meet this challenge, many groups have developed imaging methods that target pathogen-specific metabolism, including PET tracers integrated into the bacterial cell wall. We have previously reported the d-amino acid derived PET radiotracers d-methyl-[11C]-methionine, d-[3-11C]-alanine, and d-[3-11C]-alanine-d-alanine, which showed robust bacterial accumulation in vitro and in vivo. Given the clinical importance of radionuclide half-life, in the current study, we developed [18F]3,3,3-trifluoro-d-alanine (d-[18F]-CF3-ala), a fluorine-18 labeled tracer. We tested the hypothesis that d-[18F]-CF3-ala would be incorporated into bacterial peptidoglycan given its structural similarity to d-alanine itself. NMR analysis showed that the fluorine-19 parent amino acid d-[19F]-CF3-ala was stable in human and mouse serum. d-[19F]-CF3-ala was also a poor substrate for d-amino acid oxidase, the enzyme largely responsible for mammalian d-amino acid metabolism and a likely contributor to background signals using d-amino acid derived PET tracers. In addition, d-[19F]-CF3-ala showed robust incorporation into Escherichia coli peptidoglycan, as detected by HPLC/mass spectrometry. Based on these promising results, we developed a radiosynthesis of d-[18F]-CF3-ala via displacement of a bromo-precursor with [18F]fluoride followed by chiral stationary phase HPLC. Unexpectedly, the accumulation of d-[18F]-CF3-ala by bacteria in vitro was highest for Gram-negative pathogens in particular E. coli. In a murine model of acute bacterial infection, d-[18F]-CF3-ala could distinguish live from heat-killed E. coli, with low background signals. These results indicate the viability of [18F]-modified d-amino acids for infection imaging and indicate that improved specificity for bacterial metabolism can improve tracer performance.

In neuroscience research, chiral metabolomics is an emerging field, in which D-amino acids play an important role as potential biomarkers for neurological diseases. The targeted chiral analysis of the brain metabolome, employing liquid chromatography (LC) coupled to mass spectrometry (MS), is a pivotal approach for the identification of biomarkers for neurological diseases. This review provides an overview of D-amino acids in neurological diseases and of the state-of-the-art strategies for the enantioselective analysis of chiral amino acids (AAs) in biological samples to investigate their putative role as biomarkers for neurological diseases. Fluctuations in D-amino acids (D-AAs) levels can be related to the pathology of neurological diseases, for example, through their role in the modulation of N-methyl-D-aspartate receptors and neurotransmission. Because of the trace presence of these biomolecules in mammals and the complex nature of biological matrices, highly sensitive and selective analytical methods are essential. Derivatization strategies with chiral reagents are highlighted as critical tools for enhancing detection capabilities. The latest advances in chiral derivatization reactions, coupled to LC-MS/MS analysis, have improved the enantioselective quantification of these AAs and allow the separation of several chiral metabolites in a single analytical run. The enhanced performances of these methods can provide an accurate correlation between specific D-AA profiles and disease states, allowing for a better understanding of neurological diseases and drug effects on the brain. [ABSTRACT FROM AUTHOR]

A Raman-active boronate modified surface-enhanced Raman scattering (SERS) microporous array chip based on the enzymatic reaction was constructed for reliable, sensitive, and quantitative monitoring of D-Proline (D-Pro) and D-Alanine (D-Ala) in saliva. Initially, 3-mercaptophenylboronic acid (3-MPBA) was bonded to Au-coated Si nanocrown arrays (Au/SiNCA) via Au–S bonding. Following this, H2O2 obtained from D-amino acid oxidase (DAAO)-specific catalyzed D-amino acids (D-AAs) further reduced 3-MPBA to 3-hydroxythiophenol (3-HTP) with a new Raman peak at 882 cm−1. Meanwhile, the original characteristic peak at 998 cm−1 remained unchanged. Therefore, the I882/I998 ratio increased with increasing content of D-AAs in the sample to be tested, allowing D-AAs to be quantitatively detected. The Au/SiNCA with large-area periodic crown structure prepared provided numerous, uniform "hot spots," and the microporous array chip with 16 detection units was employed as the platform for SERS analysis, realizing high-throughput, high sensitivity, high specificity and high-reliability quantitative detection of D-AAs (D-Pro and D-Ala). The limits of detection (LOD) were down to 10.1 µM and 13.7 µM throughout the linear range of 20–500 µM. The good results of the saliva detection suggested that this SERS sensor could rapidly differentiate between early-stage gastric cancer patients and healthy individuals. [ABSTRACT FROM AUTHOR]

Tsg101 is implicated in tumorigenesis and viral budding, and its inhibition through peptide binding is a potential therapeutic strategy. We utilized the crystal structure of the Tsg101‐PSAP complex from the protein databank in molecular dynamics studies on peptide‐Tsg101 interactions. To enhance peptide stability against enzymatic degradation, we designed peptides with L‐form terminal prolines and D‐form middle amino acids. These peptides also featured acetylated proline at the N‐terminus and amidated C‐terminus, increasing resistance to proteases. Virtual screening of 400 amino acid combinations identified promising peptide candidates and specific binding sites. Subsequent molecular dynamics simulations focused on the peptide PywP, which displayed strong binding stability at a novel Tsg101 site. Further simulations with variations of the D‐form amino acid ′w' showed that 18 of 21 tested peptides, notably PyeP and PytP, remained firmly bound, highlighting their potential as Tsg101 inhibitors. These peptides also contain hydrophilic residues, potentially improving solubility and therapeutic delivery. [ABSTRACT FROM AUTHOR]

The symbiosis between Vibrio fischeri and the Hawaiian bobtail squid, Euprymna scolopes, is a tractable and well-studied model of bacteria-animal mutualism. Here, we developed a method to transiently colonize E. scolopes using D-alanine (D-ala) auxotrophy of the symbiont, controlling the persistence of viable infection by supplying or withholding D-ala. We generated alanine racemase (alr) mutants of V. fischeri that lack avenues for mutational suppression of auxotrophy or reversion to prototrophy. Surprisingly, an alr mutant did not require D-ala to grow in a minimal medium, a phenomenon requiring metC, which encodes cystathionine ß-lyase. Likewise, overexpression of metC suppressed D-ala auxotrophy in a rich medium. To block potential mechanisms of suppression, we combined the alr mutation with deletions of metC and/or bsrF, which encodes a broad-spectrum racemase and investigated the suppression rates of four D-ala auxotrophic strains. We then focused on alr bsrF mutant MC13, which has a suppression rate of <10-9. When D-ala was removed from a growing culture of MC13, cells rounded and lysed within 40 minutes. Transient colonization of E. scolopes was achieved by inoculating squid in seawater containing MC13 and D-ala, and then transferring the squid into water lacking D-ala, which resulted in loss of viable symbionts within hours. Interestingly, the symbionts within crypt 3 persisted longer than those of crypt 1, suggesting a difference in bacterial growth rate in distinct crypt environments. Our study highlights a new approach for inducing transient colonization and provides insight into the biogeography of the E. scolopes light organ. IMPORTANCE The importance of this study is multi-faceted, providing a valuable methodological tool and insight into the biology of the symbiosis between Vibrio fischeri and Euprymna scolopes. First, the study sheds light on the critical role of D-ala for bacterial growth, and the underpinnings of D-ala synthesis. Our observations that metC obviates the need for D-ala supplementation of an alr mutant in minimal medium and that MetC-dependent growth correlates with D-ala in peptidoglycan, corroborate and extend previous findings in Escherichia coli regarding a role of MetC in D-ala production. Second, our isolation of robust D-ala auxotrophs led us to a novel method for studying the squid-Vibrio symbiosis, allowing for transient colonization without the use of antibiotics, and revealed intriguing differences in symbiont growth parameters in distinct light organ crypts. This work and the methodology developed will contribute to our understanding of the persistence and dynamics of V. fischeri within its host. [ABSTRACT FROM AUTHOR]

Over three decades ago, two independent groups of investigators identified free D‐aspartic and later D‐serine in specific brain nuclei and endocrine glands. This finding revealed a novel, non‐proteinogenic role of these molecules. Moreover, the finding that aged proteins from the human eye crystallin, teeth, bone, blood vessels or the brain incorporate D‐aspartic acids to specific primary protein sequences fostered the hypothesis that aging might be related to D‐amino acid isomerization of body proteins. The experimental confirmation that schizophrenia and neurodegenerative diseases modify plasma free D‐amino acids or tissue levelsnurtured the opportunity of using D‐amino acids as therapeutic agents for several disease treatments, a strategy that prompted the successful current application of D‐amino acids to human medicine. [ABSTRACT FROM AUTHOR]

The aim of this study was to test the hypothesis that a combination of D-amino acids (DAAs) and trans -cinnamaldehyde (TC) demonstrates superior antibiofilm activity to calcium hydroxide (CH) and untreated controls. In this 3-part in vitro study, the concentration of DAAs (D-methionine, D-leucine, D-tyrosine, and D-tryptophan) that would significantly decrease Enterococcus faecalis and Actinomyces naeslundii biofilm biomass was first determined. Then, the effect of TC + selected DAAs on polymicrobial biofilms was characterized by quantifying the biomass and biofilm viability. Finally, the antibiofilm effects of TC + DAA was compared with CH and untreated controls by (i) determining bacterial viability and (ii) quantifying biofilm matrix composition using selective fluorescence-binding analysis. Statistical analysis was performed using one-way ANOVA and appropriate multiple comparisons test, with P <.05 considered as statistically significant. TC (0.06%) + D-tyrosine (1 mM) + D-tryptophan (25 mM) significantly reduced the biomass and biofilm viability compared to the control (P <.05). While no significant difference was observed between TC + DAA and CH in the cultivable bacterial counts (P >.05), confocal microscopy demonstrated a significantly greater percentage of dead bacteria in TC + DAA-treated biofilms compared to CH and the control (P <.05). TC + DAA significantly decreased the biovolume and all the examined components of the biofilm matrix quantity compared to the control, while CH significantly reduced only the exopolysaccharide quantity (P <.05). The combination of TC + D-tyrosine + D-tryptophan demonstrated superior antibiofilm activity (biofilm bacterial killing and reduction of matrix quantity) to CH and has potential to be developed as an intracanal medicament. [ABSTRACT FROM AUTHOR]

Abstract Gliomas, particularly glioblastomas (GBMs), pose significant challenges due to their aggressiveness and poor prognosis. Early detection through biomarkers is critical for improving outcomes. This study aimed to identify novel biomarkers for gliomas, particularly GBMs, using chiral amino acid profiling. We used chiral amino acid analysis to measure amino acid L- and D-isomer levels in resected tissues (tumor and non-tumor), blood, and urine from 33 patients with primary gliomas and 24 healthy volunteers. The levels of D-amino acid oxidase (DAO), a D-amino acid-degrading enzyme, were evaluated to investigate the D-amino acid metabolism in brain tissue. The GBM mouse model was created by transplanting GBM cells into the brain to confirm whether gliomas affect blood and urine chiral amino acid profiles. We also assessed whether D-amino acids produced by GBM cells are involved in cell proliferation. D-asparagine (D-Asn) levels were higher and DAO expression was lower in glioma than in non-glioma tissues. Blood and urinary D-Asn levels were lower in patients with GBM than in healthy volunteers (p

Gliomas, particularly glioblastomas (GBMs), pose significant challenges due to their aggressiveness and poor prognosis. Early detection through biomarkers is critical for improving outcomes. This study aimed to identify novel biomarkers for gliomas, particularly GBMs, using chiral amino acid profiling. We used chiral amino acid analysis to measure amino acid L- and D-isomer levels in resected tissues (tumor and non-tumor), blood, and urine from 33 patients with primary gliomas and 24 healthy volunteers. The levels of D-amino acid oxidase (DAO), a D-amino acid-degrading enzyme, were evaluated to investigate the D-amino acid metabolism in brain tissue. The GBM mouse model was created by transplanting GBM cells into the brain to confirm whether gliomas affect blood and urine chiral amino acid profiles. We also assessed whether D-amino acids produced by GBM cells are involved in cell proliferation. D-asparagine (D-Asn) levels were higher and DAO expression was lower in glioma than in non-glioma tissues. Blood and urinary D-Asn levels were lower in patients with GBM than in healthy volunteers (p < 0.001), increasing after GBM removal (p < 0.05). Urinary D-Asn levels differentiated between healthy volunteers and patients with GBM (area under the curve: 0.93, sensitivity: 0.88, specificity: 0.92). GBM mouse model validated the decrease of urinary D-Asn in GBM. GBM cells used D-Asn for cell proliferation. Gliomas induce alterations in chiral amino acid profiles, affecting blood and urine levels. Urinary D-Asn emerges as a promising diagnostic biomarker for gliomas, reflecting tumor presence and severity. [ABSTRACT FROM AUTHOR]

D-aspartate (D-Asp) is an amino acid found in high concentrations in the testis and pituitary gland. Increasing evidence suggests that D-Asp promotes spermatogenesis by activating testosterone production in the Leydig cells via LH release from the pituitary gland. In vitro studies indicate that D-Asp may also influence steroidogenesis and spermatogenesis through autocrine and paracrine signals. D-Asp enhances StAR and steroidogenic enzyme expressions, facilitating testicular cell proliferation via the GluR/ERK1/2 pathway. Moreover, it supports spermatogenesis by enhancing the mitochondrial function in spermatocytes, aiding in the metabolic shift during meiosis. Enhanced mitochondrial function, along with improved MAM stability and reduced ER stress, has been observed in Leydig and Sertoli cells treated with D-Asp, indicating potential benefits in steroidogenesis and spermatogenesis efficiency. Conversely, D-Asp exerts a notable anti-apoptotic effect in the testis via the AMPAR/AKT pathway, potentially mediated by antioxidant enzyme modulation to mitigate testicular oxidative stress. This review lays the groundwork for future investigations into the molecules promoting spermatogenesis by stimulating endogenous testosterone biosynthesis, with D-amino acids emerging as promising candidates. [ABSTRACT FROM AUTHOR]

Purpose: There is currently no ideal radiotracer for imaging bacterial infections. Radiolabelled d-amino acids are promising candidates because they are actively incorporated into the peptidoglycan of the bacterial cell wall, a structural feature which is absent in human cells. This work describes fluorine-18 labelled analogues of d-tyrosine and d-methionine, O-(2-[18F]fluoroethyl)-d-tyrosine (d-[18F]FET) and S-(3-[18F]fluoropropyl)-d-homocysteine (d-[18F]FPHCys), and their pilot evaluation studies as potential radiotracers for imaging bacterial infection. Procedures: d-[18F]FET and d-[18F]FPHCys were prepared in classical fluorination-deprotection reactions, and their uptake in Staphylococcus aureus and Pseudomonas aeruginosa was evaluated over 2 h. Heat killed bacteria were used as controls. A clinically-relevant foreign body model of S. aureus infection was established in Balb/c mice, as well as a sterile foreign body to mimic inflammation. The ex vivo biodistribution of d-[18F]FPHCys in the infected and inflamed mice was evaluated after 1 h, by dissection and gamma counting. The uptake was compared to that of [18F]FDG. Results: In vitro uptake of both d-[18F]FET and d-[18F]FPHCys was specific to live bacteria. Uptake was higher in S. aureus than in P. aeruginosa for both radiotracers, and of the two, higher for d-[18F]FPHCys than d-[18F]FET. Blocking experiments with non-radioactive d-[19F]FPHCys confirmed specificity of uptake. In vivo, d-[18F]FPHCys had greater accumulation in S. aureus infection compared with sterile inflammation, which was statistically significant. As anticipated, [18F]FDG showed no significant difference in uptake between infection and inflammation. Conclusions: d-[18F]FPHCys uptake was higher in infected tissues than inflammation, and represents a fluorine-18 labelled d-AA with potential to detect a S. aureus reference strain (Xen29) in vivo. Additional studies are needed to evaluate uptake of this radiotracer in clinical isolates. [ABSTRACT FROM AUTHOR]

Approximately 12% of histone H2B molecules in mammalian brain contain a modification wherein Asp25 is present as the D-enantiomer, and is mostly linked to Gly26 via the side-chain carboxyl. Here we (1) demonstrate the high specificity of a polyclonal antibody to this modification, and (2) use this Ab to demonstrate that this modification is enriched in brain relative to liver, thymus, and HeLa cells.

Biomarkers that accurately reflect renal function are essential in management of chronic kidney diseases (CKD). However, in children, age/physique and medication often alter established renal biomarkers. We studied whether amino acid enantiomers in body fluids correlate with renal function and whether they are influenced by physique or steroid medication during development. We conducted a prospective study of children 2 to 18 years old with and without CKD. We analyzed associations of serine/asparagine enantiomers in body fluids with major biochemical parameters as well as physique. To study consequences of kidney dysfunction and steroids on serine/asparagine enantiomers, we generated juvenile mice with uninephrectomy, ischemic reperfusion injury, or dexamethasone treatment. We obtained samples from 27 children, of which 12 had CKD due to congenital (n = 7) and perinatal (n = 5) causes. Plasma d-asparagine and the d/l-serine ratio had robust, positive linear associations with serum creatinine and cystatin C, and detected CKD with high sensitivity and specificity, uninfluenced by body size or biochemical parameters. In the animal study, kidney dysfunction increased plasma d-asparagine and the d/l-serine ratio, but dexamethasone treatment did not. Thus, plasma d-asparagine and the d/l-serine ratio can be useful markers for renal function in children. [ABSTRACT FROM AUTHOR]

Background: Patients with chronic kidney disease (CKD) reportedly show dysbiosis, which is the imbalance of gut microbiome. Dysbiosis increases the uremic toxin level in the intestine, and uremic toxins transfer into the blood, causing CKD progression. Sake lees, a traditional Japanese fermented food, may help reduce uremic toxins by altering the gut microbiome. Additionally, D-alanine, which is present in sake lees, may have a renoprotective effect. The present pilot study aims to evaluate the effect of adding sake lees to the standard CKD dietary therapy in reducing blood uremic toxins. Methods: This pilot study is a single-center, open-label, randomized controlled trial. Twenty-four patients with CKD will be enrolled and allocated 1:1 to the intervention and control groups. The intervention group will receive standard CKD dietary therapy with an additional intake of 50 g of sake lees per day for 8 weeks, whereas the control group will only receive standard CKD dietary therapy. The primary endpoint is the change in serum indoxyl sulfate after 8 weeks. The secondary endpoint is the plasma D-alanine and fecal microbiome changes. Conclusion: This pilot study provides insight into the development of a new diet focused on gut microbiome and D-amino acids in patients with CKD. Clinical trial registration: This protocol was approved by the Clinical Trial Review Board of Kanazawa University Hospital on October 27, 2022 (2022-001 [6139]) and available to the public on the website of the Japan Registry of Clinical Trials on November 22, 2022 (jRCT1040220095). [ABSTRACT FROM AUTHOR]

This work describes the self‐assembly behavior of heterochiral, aliphatic dipeptides, l‐Leu‐d‐Xaa (Xaa = Ala, Val, Ile, Leu), in green solvents such as acetonitrile (MeCN) and buffered water at neutral pH. Interestingly, water plays a structuring role because at 1% v/v, it enables dipeptide self‐assembly in MeCN to yield organogels, which then undergo transition towards crystals. Other organic solvents and oils were tested for gelation, and metastable gels were formed in tetrahydrofuran, although at high peptide concentration (80 mM). Single‐crystal X‐ray diffraction revealed the dipeptides' supramolecular packing modes in amphipathic layers, as opposed to water channels reported for the homochiral Leu–Leu, or hydrophobic columns reported for homochiral Leu–Val and Leu–Ile. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance is a silent pandemic harming human health, and Pseudomonas aeruginosa is the most common bacterium responsible for chronic pulmonary and eye infections. Antimicrobial peptides (AMPs) represent promising alternatives to conventional antibiotics. In this review, the in vitro/in vivo activities of the frog skin-derived AMP Esc(1-21) are shown. Esc(1-21) rapidly kills both the planktonic and sessile forms of P. aeruginosa and stimulates migration of epithelial cells, likely favoring repair of damaged tissue. However, to undertake preclinical studies, some drawbacks of AMPs (cytotoxicity, poor biostability, and limited delivery to the target site) must be overcome. For this purpose, the stereochemistry of two amino acids of Esc(1-21) was changed to obtain the diastereomer Esc(1-21)-1c, which is more stable, less cytotoxic, and more efficient in treating P. aeruginosa-induced lung and cornea infections in mouse models. Incorporation of these peptides (Esc peptides) into nanoparticles or immobilization to a medical device (contact lens) was revealed to be an effective strategy to ameliorate and/or to prolong the peptides' antimicrobial efficacy. Overall, these data make Esc peptides encouraging candidates for novel multifunctional drugs to treat lung pathology especially in patients with cystic fibrosis and eye dysfunctions, characterized by both tissue injury and bacterial infection. [ABSTRACT FROM AUTHOR]

This article discusses the development of antimicrobial coatings for biomaterial surfaces to inhibit biofilm formation. The researchers integrated hydrogel coatings with D-amino acid mixtures and gentamicin to create coatings with optimized mechanical stability and biofilm inhibition capabilities. The hydrogel coatings demonstrated high stability and were able to significantly reduce bacterial numbers. This research provides a promising approach to combat biofilms associated with bacterial infections on biomedical surfaces. The document also discusses the preparation and characterization of hydrogel coatings for biomedical applications. The hydrogel coatings were synthesized using a UV-induced free radical polymerization method. The composition of the coatings was analyzed using Fourier transform infrared spectroscopy. The mechanical stability of the coatings was evaluated through swelling, flow, and tape-peeling tests. The results showed that the hydrogel coatings exhibited good mechanical stability, making them suitable for biomedical applications. The document further discusses the release of drugs from the hydrogel coatings and their antimicrobial and antibiofilm activities. The addition of SBMA segments improves the mechanical stability of the coatings, while the introduction of HEMA segments does not reverse the poor mechanical stability. The hydrogel coatings with a combination of SBMA and HEMA components exhibit the best mechanical stability. The hydrogel coatings also demonstrate good drug release behavior, with PS50H50op coatings releasing the highest amount of drugs. Furthermore, PS50H50op coatings exhibit excellent antibiofilm and antimicrobial activities, inhibiting biofilm formation and bacterial growth. The article discusses the development of hydrogel [Extracted from the article]

Microbiologically influenced corrosion (MIC) poses a threat to various fields, particularly in piping and cooling water systems. As a green corrosion inhibitor, polyaspartic acid (PASP) faces challenges in achieving the intended corrosion inhibition against MIC due to biofilm. Therefore, mitigating biofilm might be the key to improving the corrosion inhibition of PASP. D-Phenylalanine (D-Phe) was selected as an enhancer to promote the inhibition of PASP on MIC caused by Desulfovibrio vulgaris due to its potential role in biofilm formation in this work. The joint application of PASP and D-Phe reduced the corrosion rate by 76.54% and obviously decreased the depth of corrosion pits with the maximum depth at 0.95 µm. Also, fewer cells adhered to the coupon surface due to the combined action of PASP and D-Phe, leading to thin and loose biofilm. Besides, both cathodic and anodic reactions were retarded with PASP and D-Phe, resulting in a low corrosion current at 0.530 x 10-7 A/cm². The primary synergy mechanism is that D-Phe promoted the formation of PASP protective film via decreasing bacterial adhesion and thus inhibited electrochemical reaction and electron utilization of cells from metal surface. This study introduces a novel strategy to augment the effectiveness of PASP in inhibiting MIC. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance (AMR) from pathogenic bacterial biofilms has become a global health issue while developing novel antimicrobials is inefficient and costly. Combining existing multiple drugs with enhanced efficacy and/or reduced toxicity may be a promising approach to treat AMR. D‐amino acids mixtures coupled with antibiotics can provide new therapies for drug‐resistance infection with reduced toxicity by lower drug dosage requirements. However, iterative trial‐and‐error experiments are not tenable to prioritize credible drug formulations, owing to the extremely large number of possible combinations. Herein, a new avenue is provide to accelerate the exploration of desirable antimicrobial formulations via high‐throughput screening and machine learning optimization. Such an intelligent method can navigate the large search space and rapidly identify the D‐amino acid mixtures with the highest anti‐biofilm efficiency and also the synergisms between D‐amino acid mixtures and antibiotics. The optimized drug cocktails exhibit high antimicrobial efficacy while remaining non‐toxic, which is demonstrated not only from in vitro assessments but also the first in vivo study using a lung infection mouse model. [ABSTRACT FROM AUTHOR]

Solid state NMR is widely used to study the orientation and other structural features of proteins and peptides in lipid bilayers. Using data obtained by PISEMA (Polarization Inversion Spin Exchange at Magic Angle) experiments, periodic spectral patterns arise from well‐aligned α‐helical molecules. Significant problems in the interpretation of PISEMA spectra may arise for systems that do not form perfectly defined secondary structures, like α‐helices, or the signal pattern is disturbed by molecular motion. Here, we present a new method that combines molecular dynamics simulation with tensorial orientational constraints (MDOC) and chemical shift tensor calculations for the simulation and interpretation of PISEMA‐like spectra. The calculations include the spectra arising from non α‐helical molecules and molecules with non‐uniform intrinsic mobility. In a first step, dipolar or quadrupolar interaction tensors drive molecular rotations and reorientations to obtain the proper mean values as observed in corresponding NMR experiments. In a second step, the coordinate snapshots of the MDOC simulations are geometry optimized with the isotropic 15N chemical shifts as constraints using Bond Polarization Theory (BPT) to provide reliable 15N CS tensor data. The averaged dipolar 1H‐15N couplings and the δzz tensor components can then be combined to simulate PISEMA patterns. We apply this method to the ß‐helical peptide gramicidin A (gA) and demonstrate that this method enables the assignment of most PISEMA resonances. In addition, MDOC simulations provide local order parameters for the calculated sites. These local order parameters reveal large differences in backbone mobility between L‐ and D‐amino acids of gA. [ABSTRACT FROM AUTHOR]

Pseudomonas putida is a metabolically robust soil bacterium that employs a diverse set of pathways to utilize a wide range of nutrients. The versatility of this microorganism contributes to both its environmental ubiquity and its rising popularity as a bioengineering chassis. In P. putida, the newly named dbu locus encodes a transcriptional regulator (DbuR), D-amino acid oxidase (DbuA), Rid2 protein (DbuB), and a putative transporter (DbuC). Current annotation implicates this locus in the utilization of D-arginine. However, data obtained in this study showed that genes in the dbu locus are not required for D-arginine utilization, but, rather, this locus is involved in the catabolism of multiple D-branched-chain amino acids (D-BCAA). The oxidase DbuA was required for catabolism of each D-BCAA and D-phenylalanine, while the requirements for DbuC and DbuB were less stringent. The functional characterization of the dbu locus contributes to our understanding of the metabolic network of P. putida and proposes divergence in function between proteins annotated as D-arginine oxidases across the Pseudomonas genus. [ABSTRACT FROM AUTHOR]

The anti-inflammatory, antiviral, and anti-cancer properties, as well as the mechanism of action of cyclo-[Pro-Pro-β3-HoPhe-Phe-] tetrapeptide (denoted as 4B8M), were recently described. The aim of this work was to synthesize and evaluate the immunosuppressive actions of the stereochemical variants of 4B8M by sequential substitution of L-amino acids by D-amino acids (a series of peptides denoted as P01–P07) using parent 4B8M as a reference compound. In addition, diverse available bioinformatics tools using machine learning and artificial intelligence were tested to find the bio-pharmacokinetic and polypharmacological attributes of analyzed stereomers. All peptides were non-toxic to human peripheral blood mononuclear cells (PBMCs) and only cyclo-[D-Pro-Pro-β3-HoPhe-Phe-] peptide (P03) was capable of inhibiting mitogen-induced PBMC proliferation. The peptides inhibited the lipopolysaccharide (LPS)-induced production of tumor necrosis factor-alpha (TNF-α) to various degrees, with P04 (cyclo-[Pro-Pro-D-β3-HoPhe-Phe-]) and P03 being the most potent. For further in vivo studies, P03 was selected because it had the combined properties of inhibiting cell proliferation and TNF-α production. P03 demonstrated a comparable ability to 4B8M in the inhibition of auricle edema and lymph node cell number and in the normalization of a distorted blood cell composition in contact sensitivity to the oxazolone mouse model. In the mouse model of carrageenan-induced inflammation of the air pouch, P03 exhibited a similar inhibition of the cell number in the air pouches as 4B8M, but its inhibitory effects on the percentage of neutrophils and eosinophils in the air pouches and blood, as well as on mastocyte degranulation in the air pouches, were stronger in comparison to 4B8M. Lastly, in a mouse model of dextran sulfate-induced colitis, similar effects to 4B8M regarding thymocyte number restoration and normalization of the blood cell pictures by P03 were observed. In summary, depending on either experimental findings or in silico predictions, P03 demonstrated comparable, or even better, anti-inflammatory and bio-pharmacokinetic properties to 4B8M and may be considered as a potential therapeutic. The possibility of P00 and P03 identification by circular dichroism measurements was tested by quantum-chemical calculations.

Abstract Antimicrobial resistance (AMR) from pathogenic bacterial biofilms has become a global health issue while developing novel antimicrobials is inefficient and costly. Combining existing multiple drugs with enhanced efficacy and/or reduced toxicity may be a promising approach to treat AMR. D‐amino acids mixtures coupled with antibiotics can provide new therapies for drug‐resistance infection with reduced toxicity by lower drug dosage requirements. However, iterative trial‐and‐error experiments are not tenable to prioritize credible drug formulations, owing to the extremely large number of possible combinations. Herein, a new avenue is provide to accelerate the exploration of desirable antimicrobial formulations via high‐throughput screening and machine learning optimization. Such an intelligent method can navigate the large search space and rapidly identify the D‐amino acid mixtures with the highest anti‐biofilm efficiency and also the synergisms between D‐amino acid mixtures and antibiotics. The optimized drug cocktails exhibit high antimicrobial efficacy while remaining non‐toxic, which is demonstrated not only from in vitro assessments but also the first in vivo study using a lung infection mouse model.

Pain, whether acute or chronic, is one of the most unpleasant experiences. It can have different origins and long-term effects on the body starting from the trivial once such as physical discomfort, accompanying by emotional distress and going to the more serious like depression, anxiety, and social isolation. The removal and proper treatment of the pain is a problem highly dependent on both the source and the individual features of each organism. Herein the view is turned on investigation of activity of new analogs of natural FELL peptide as a promising alternative of the existing antipain molecules. All targeted compounds are obtained by means of conventional peptide synthesis on solid support using standard Fmoc/OtBu approach and their analgesic activity was evaluated by Paw-pressure (Randall-Selitto) test. Determination of the in vivo analgesic activity of the newly synthesized substances showed that the substitution of both Leu (BB11) with Val residues (BB8) increased PPT of the experimental animals on the 10th min, compared to the values after the nonmodified parent molecule injection. On the 20th and the 30th min, BB8 analgesic activity was comparable to BB11 and further a decrease in the PPT was observed. In addition, compared to the controls, analgesia exists until the end of the monitored period of 50 min. The other three newly synthesized substances including Nle (BB6), Ile (BB7) and triple Leu (BB5) instead of double Leu residues showed time-varying short-term analgesic activity, which did not reach that of the parent molecule BB11. Final results show that D-Phe in a first position of the molecule, combined with both Leu residues in the third and fourth positions are the best combination concerning analgesic activity. In addition, lengthening the peptide chain by adding one more hydrophobic residue has also a positive effect on the obtained analgesia. Cytotoxicity of final molecules is significantly lower than those of the positive control SLS, combined with complete hydrolytic stability, which allows their safety use in pharmacy.

Hydrolases are enzymes that have found numerous applications in various industrial sectors spanning from pharmaceuticals to foodstuff and beverages, consumers' products such as detergents and personal care, textiles, and even for biodiesel production and environmental bioremediation. Self-assembling and gelling short peptides have been designed for their mimicry so that their supramolecular organization leads to the creation of hydrophobic pockets for catalysis to occur. Catalytic gels of this kind can also find numerous industrial applications to address important global challenges of our time. This concise review focuses on the last 5 years of progress in this fast-paced, popular field of research with an eye towards the future. [ABSTRACT FROM AUTHOR]

Simple Summary: The molecule 1-aminocyclopropane-1-carboxylate is the immediate precursor of the plant hormone ethylene in most seed plant species. Both 1-aminocyclopropane-1-carboxylate and ethylene can affect plant growth and development in a variety of ways. In addition, the bacterial enzyme 1-aminocyclopropane-1-carboxylate deaminase can cleave 1-aminocyclopropane-1-carboxylate and prevent both 1-aminocyclopropane-1-carboxylate and ethylene from affecting plant gene expression and subsequent behavior. In this review, the roles of 1-aminocyclopropane-1-carboxylate, ethylene and 1-aminocyclopropane-1-carboxylate deaminase in the development of plants and their regulation are explored. Since D-amino acids stimulate ethylene synthesis in plants, a section of the review is dedicated to this topic. It is suggested that 1-aminocyclopropane-1-carboxylate was synthesized in plants prior to the plant synthesis of ethylene, giving 1-aminocyclopropane-1-carboxylate some control of plant gene expression in response to environmental signals. Here, a brief summary of the biosynthesis of 1-aminocyclopropane-1-carboxylate (ACC) and ethylene in plants, as well as overviews of how ACC and ethylene act as signaling molecules in plants, is presented. Next, how the bacterial enzyme ACC deaminase cleaves plant-produced ACC and thereby decreases or prevents the ethylene or ACC modulation of plant gene expression is considered. A detailed model of ACC deaminase functioning, including the role of indoleacetic acid (IAA), is presented. Given that ACC is a signaling molecule under some circumstances, this suggests that ACC, which appears to have evolved prior to ethylene, may have been a major signaling molecule in primitive plants prior to the evolution of ethylene and ethylene signaling. Due to their involvement in stimulating ethylene production, the role of D-amino acids in plants is then considered. The enzyme D-cysteine desulfhydrase, which is structurally very similar to ACC deaminase, is briefly discussed and the possibility that ACC deaminase arose as a variant of D-cysteine desulfhydrase is suggested. [ABSTRACT FROM AUTHOR]

In recent decades, antimicrobial peptides (AMPs) have held great promise as novel antibiotic agents. However, they have generally been excluded from clinical use due to certain limitations, such as poor biocompatibility and sensitivity to environmental conditions. In this study, we report a novel brevinin-1 type antimicrobial peptide B1LTe, derived from the skin secretion of Hylarana latouchii. Although the novel peptide B1LTe exhibited remarkable antimicrobial effects, its narrow therapeutic index (TI) can result in adverse drug reactions. Thus, the rational design by systematically scanning and replacing the inherent hydrophobic and cationic residues (Leucine and Lysine) with their D-enantiomeric counterparts was conducted to enhance the application potential of B1LTe. Simultaneously, we also applied lysine-to-arginine substitution within the modification. Among the derivates, 5 R demonstrated the highest selectivity and effectiveness against Methicillin-resistant Streptococcus aureus (MRSA), clinic-isolated Streptococcus pyogenes (S. pyogenes) strain, ranging from their planktonic to biofilm cells, both in vitro and in vivo. Furthermore, the remarkable adaptation of 5 R in saline and 20% serum indicates its potential for clinical application. We employed the in silico approach, which revealed the mechanism of interaction between 5 R and bacterial membranes. In addition, further mechanistic studies of 5 R elucidated the association between the collapsed proton motive force (PMF) and membrane perturbation as peptides aggregate on the bacterial membrane. Overall, our study suggests the D-enantiomeric 5 R can be a promising antibiotic agent against MDR bacteria in further clinical development and highlights the significance of cellular PMF as a potential target for the research of peptides’ mode of action.

Among the 20 proteinogenic amino acids, 19 can exist in two stereoisomeric forms, D- and L-enantiomers except glycine. According to conventional theory, L-amino acids are the main body involved in life activities, while little attention has been paid to the existence and physiological activity of D-amino acids in organisms. With the development of analytical technologies for chiral amino acids, a large number of D-amino acids and bioactive peptides containing D-amino acids have been found in various organisms, including mammals, plants, microorganisms and humans. D-amino acids possess unique physiological activities such as neural signal transduction, hormone regulation, antibacterial effect and immune regulation. Daily diet is an important source of D-amino acids for humans, and the daily average supply of D-amino acids for humans is about 100 mg. D-amino acids in foods mainly origin from processing conditions such as fermentation, high temperature and certain pH, along with a small amount from food raw materials. At present, emerging functional foods with D-amino acids as the major component have begun to appear in the market. D-amino acids hold great potential that deserves to be explored further and are expected to be an important ingredient for the development of new functional foods in the future.

To explore the effects of the compound fungicide on the microbial life cycle, the improvement of the corrosion inhibition rate and sterilization rate of D-amino acid compound fungicides on carbon steel in different periods was studied using the mixed microflora composed of SRB and IOB produced from the oil and gas field through the weightlessness experiment, electrochemical test, surface analysis technology and other research methods. The results showed that the corrosion rate and sterilization efficiency were improved when D-amino acid compound fungicide was adding in different periods. The function of D-amino acid compound fungicide was optimal, when it was added on the third day. D-amino acid could cause the surface of the bacteria hydrophobic, which affects the material transmission between bacteria. D-amino acid could break up the biofilm and inhibit the growth of biofilm. Microorganisms could multiply rapidly on steel surfaces over time and reach an active peak period of life activity in seven days,during which H2S production will accelerate steel corrosion. [ABSTRACT FROM AUTHOR]

Microbiome dysbiosis resulting in altered metabolite profiles may be associated with certain diseases, including inflammatory bowel diseases (IBD), which are characterized by active intestinal inflammation. Several studies have indicated the beneficial anti-inflammatory effect of metabolites from gut microbiota, such as short-chain fatty acids (SCFAs) and/or D-amino acids in IBD therapy, through orally administered dietary supplements. In the present study, the potential gut protective effects of d-methionine (D-Met) and/or butyric acid (BA) have been investigated in an IBD mouse model. We have also built an IBD mouse model, which was cost-effectively induced with low molecular weight DSS and kappa-carrageenan. Our findings revealed that D-Met and/or BA supplementation resulted in the attenuation of the disease condition as well as the suppression of several inflammation-related gene expressions in the IBD mouse model. The data shown here may suggest a promising therapeutic potential for improving symptoms of gut inflammation with an impact on IBD therapy. However, molecular metabolisms need to be further explored. [ABSTRACT FROM AUTHOR]

Biomolecules are frequently chiral compounds, existing in enantiomeric forms. Amino acids represent a meaningful example of chiral biological molecules. Both L- and D-amino acids play key roles in the biochemical structure and metabolic processes of living organisms, from bacteria to mammals. In this review, we explore the enantiospecific interaction between proteins and chiral amino acids, introducing theoretical models and describing the molecular basis of the ability of some of the most important enzymes involved in the metabolism of amino acids (i.e., amino acid oxidases, dehydrogenases, and aminotransferases) to discriminate the opposite enantiomers. Our analysis showcases the power of natural evolution in shaping biological processes. Accordingly, the importance of amino acids spurred nature to evolve strictly enantioselective enzymes both through divergent evolution, starting from a common ancestral protein, or through convergent evolution, starting from different scaffolds: intriguingly, the active sites of these enzymes are frequently related by a mirror symmetry. [ABSTRACT FROM AUTHOR]

Here we designed and synthesized analogs of two antimicrobial peptides, namely C10:0-A2, a lipopeptide, and TA4, a cationic α-helical amphipathic peptide, and used non-proteinogenic amino acids to improve their therapeutic properties. The physicochemical properties of these analogs were analyzed, including their retention time, hydrophobicity, and critical micelle concentration, as well as their antimicrobial activity against gram-positive and gram-negative bacteria and yeast. Our results showed that substitution with D- and N-methyl amino acids could be a useful strategy to modulate the therapeutic properties of antimicrobial peptides and lipopeptides, including enhancing stability against enzymatic degradation. The study provides insights into the design and optimization of antimicrobial peptides to achieve improved stability and therapeutic efficacy. TA4(dK), C10:0-A2(6-NMeLys), and C10:0-A2(9-NMeLys) were identified as the most promising molecules for further studies. [ABSTRACT FROM AUTHOR]

The immune-related adverse events resulting from the therapy of immune checkpoint inhibitors could cause kidney injury. Inflammatory reprogramming of regulatory T helper (Treg) cells or type 17 T helper (Th17) cells might be involved in the pathogenesis of nephropathy. Accumulating evidence confirms a connection between the diversity of gut microbiota and kidney diseases, suggesting that successful modification of gut microbiota could attenuate kidney injury. In other words, certain gut microbiota could contribute to the protection of kidneys via the gut-kidney axis. It has been shown that the dysbiosis of gut microbiota might affect the gut-kidney axis, leading to nephrotoxicity. On the contrary, altered levels of D-amino acids, ROS, and SCFAs through the adjustment of gut microbiota might be relevant to the reduction of nephrotoxicity. Here, we have discussed and suggested the beneficial roles of gut microbiota in the prevention of the kidney injury induced during immune-checkpoint therapy.

In 1942, G. F. Gause and M. G. Brazhnikova created one of the first antibiotics in the Soviet Union — gramicidin C. In the same year, its successful use started in front-line hospitals in the treatment of complications of wound infections. Thanks to it, the lives of hundreds of thousands of soldiers and officers were saved. Gramicidin C has passed the test of time, and today this antibiotic is effectively used in the treatment of infectious and inflammatory diseases, as well as purulent wounds. In this regard, the 80th anniversary is a good reason to recall the history of the creation of this peptide antibiotic possessing bactericidal action based on the presence of the D-isomer of the amino acid phenylalanine in the producing bacteria. However, the study of ways to overcome the spreading antibiotic resistance in bacteria, as well as the search for alternative antimicrobial strategies are currently on the agenda. For this reason, it is appropriate to recall that the study of the molecular structure of gramicidin C gave impetus not only to the discovery of a whole family of cyclic peptide antibiotics, but also to the discovery of the ability of various organisms to nonribosomal synthesis of biologically active peptides containing D-amino acids with a pronounced antimicrobial effect. Their development is already a vital task today, and the use of peptides is considered a real and promising alternative to traditional antibiotics. Thus, gramicidin C, obtained at the dawn of the era of antibiotics, became a harbinger of the birth of a fundamentally new and promising antimicrobial strategy.

Background: The D-isoforms of amino acids (D-AAs) exhibit anti-biofilm potential against a diverse range of bacterial species in vitro, while its role in vivo remains unclear. The aim of this study was to investigate the effects of a combination of D-AAs and vancomycin on a PJI rat model. Methods: Eight-week-old male SD rats were randomized to the control group, sham group, vancomycin group, D-AAs–vancomycin group. After treatment for 6 weeks, we analysed the levels of inflammatory factors in serum, behavioural change, imaging manifestations. The anti-biofilm ability of D-AAs was detected by crystal violet staining and scanning electron microscope observation, and its ability to assist antibiotics in killing bacteria was assessed by culture of bacteria. Additionally, micro-CT and histological analysis were used to evaluate the impact of D-AAs combined with vancomycin on the bone remodelling around the prosthesis. Results: The group treated with a D-AAs–vancomycin combination sustained normal weight gain and exhibited reduced the serum levels of α2M, IL-1β, IL-6, IL-10, TNF-α and PGE2. Moreover, treated with D-AAs in combination with vancomycin improved the weight-bearing activity performance, increased the sizes and widths of distal femurs, and improved Rissing scale scoring. In particular, treatment using D-AAs enhanced the ability of vancomycin to eradicate Staphylococcus aureus, as demonstrated by the dispersion of existing biofilms and the inhibition of biofilm formation that occurred in a concentration-dependent manner. This treatment combination also resulted in a reduction in bacterial burden with in the soft tissues, bones, and implants. Furthermore, D-AAs–vancomycin combination treatment attenuated abnormal bone remodelling around the implant, as evidenced by an observed increase in BMD, BV/TV, and Tb.Th and the presence of reduced Trap+ osteoclasts and elevated osterix+ osteo-progenitors. Conclusions: Combining D-AAs with vancomycin provides an effective therapeutic strategy for the treatment of PJI by promoting biofilm dispersion to enhance antimicrobial activity.

The study of biominerals of a pathogenic nature in organisms is relevant and necessary for establishing the mechanism of their formation and solving many practical issues. Recently, intensive research has been carried out in the field of biochemistry of D-amino acids, it is believed that they can be potential biomarkers of various pathological processes in the human body. The presence of enantiomers of amino acids and their role in the mechanism of formation of gallstones, the issue has not yet been studied. The paper presents data on the distribution of D-enantiomers of amino acids, their content and ratio with L-forms in the composition of gallstones. A comparative analysis of the obtained results on gallstones with urinary stones is shown. It has been established that there is a relationship between the enantiomers of amino acids and the calcium mineral component. [ABSTRACT FROM AUTHOR]

Pyridoxal-5′-phosphate (PLP)-dependent transaminases are highly efficient biocatalysts for stereoselective amination. D-amino acid transaminases can catalyze stereoselective transamination producing optically pure D-amino acids. The knowledge of substrate binding mode and substrate differentiation mechanism in D-amino acid transaminases comes down to the analysis of the transaminase from Bacillus subtilis. However, at least two groups of D-amino acid transaminases differing in the active site organization are known today. Here, we present a detailed study of D-amino acid transaminase from the gram-negative bacterium Aminobacterium colombiense with a substrate binding mode different from that for the transaminase from B. subtilis. We study the enzyme using kinetic analysis, molecular modeling, and structural analysis of holoenzyme and its complex with D-glutamate. We compare the multipoint binding of D-glutamate with the binding of other substrates, D-aspartate and D-ornithine. QM/MM MD simulation reveals that the substrate can act as a base and its proton can be transferred from the amino group to the α-carboxylate group. This process occurs simultaneously with the nucleophilic attack of the PLP carbon atom by the nitrogen atom of the substrate forming gem-diamine at the transimination step. This explains the absence of the catalytic activity toward (R)-amines that lack an α-carboxylate group. The obtained results clarify another substrate binding mode in D-amino acid transaminases and underpinned the substrate activation mechanism. [ABSTRACT FROM AUTHOR]

Supramolecular hydrogels obtained from the self-organization of simple peptides, such as tripeptides, are attractive soft materials. Their viscoelastic properties can be enhanced through the inclusion of carbon nanomaterials (CNMs), although their presence can also hinder self-assembly, thus requiring investigation of the compatibility of CNMs with peptide supramolecular organization. In this work, we compared single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) as nanostructured additives for a tripeptide hydrogel, revealing superior performance by the latter. Several spectroscopic techniques, as well as thermogravimetric analyses, microscopy, and rheology data, provide details to elucidate the structure and behavior of nanocomposite hydrogels of this kind. [ABSTRACT FROM AUTHOR]

d‐Threonine aldolase (DTA) is a pyridoxal‐5′‐phosphate‐dependent enzyme which catalyzes the reversible aldol reaction of glycine with a corresponding aldehyde to yield the d‐form β‐hydroxy‐α‐amino acid. This study produced and investigated the crystal structure of DTA from Chlamydomonas reinhardtii (CrDTA) at 1.85 Å resolution. To our knowledge, this is the first report on the crystal structure of eukaryotic DTA. Compared with the structure of bacterial DTA, CrDTA has a similar arrangement of active‐site residues. On the other hand, we speculated that some non‐conserved residues alter the affinity for substrates and inhibitors. The structure of CrDTA could provide insights into the structural framework for structure‐guided protein engineering studies to modify reaction selectivity. [ABSTRACT FROM AUTHOR]

Amyloidoses include a large variety of local and systemic diseases that share the common feature of protein unfolding or refolding into amyloid fibrils. The most studied amyloids are those directly involved in neurodegenerative diseases, while others, such as those formed by insulin, are surprisingly far less studied. Insulin is a very important polypeptide that plays a variety of biological roles and, first and foremost, is at the basis of the therapy of diabetic patients. It is well-known that it can form fibrils at the site of injection, leading to inflammation and immune response, in addition to other side effects. In this concise review, we analyze the current knowledge on insulin fibrillation, with a focus on the development of peptide-based inhibitors, which are promising candidates for their biocompatibility but still pose challenges to their effective use in therapy. [ABSTRACT FROM AUTHOR]

D-amino acids, the important components of the bacterial cell walls, are valuable molecular and genetic markers of bacterial-derived organic material in the environment. D-serine, a racemization product of L-serine is one such amino acid present in various prokaryotes and eukaryotes. It is a well-recognized regulator of various activities in the human nervous system. In plants, it has a role in the nitrogen cycle regulation and pollen tube growth. Serine enantiomers are present in different concentrations and few bacterial strains are reported to contribute to D-serine in the environment. During the present study, soil samples from different places in North India were collected and processed to isolate and screen the bacteria on M9 minimal media (Himedia) for D-serine synthesis. Thin-layer chromatography (TLC Silica gel 60 F 254 (20 × 20 cm, Merck, Darmstadt, Germany) and Mass spectroscopic analysis (Bruker MICROTOF II spectrometer) studies, etc were performed. D-serine-producing isolates were characterized as per standard procedures. Bacterial isolate A1C1 with maximum D-serine (0.919 ± 0.02 nM) synthesis under optimal growth conditions (37°C ± 0.5, 150 ± 0.5 RPM, and 7 ± 0.5 pH) was identified as Bacillus tequilensis based on 16sRNA sequencing. The isolate could be a valuable serine racemization tool for various industrial and environmental applications. [ABSTRACT FROM AUTHOR]

Nanocomposite hydrogels have attracted researchers' attention in recent years to achieve superior performances in a variety of materials applications. In this work, we describe the outcome of three different strategies to combine a self-assembling tripeptide and carbon nano-onions (CNOs), through covalent and non-covalent approaches, into supramolecular and nanostructured hydrogels. Importantly, the tripeptide coated the nano-onions and extended their aqueous dispersions' stability by several hours. Furthermore, CNOs could be loaded in the tripeptide hydrogels at the highest level ever reported for nanocarbons, indicating high compatibility between the components. The materials were formed in phosphate-buffered solutions, thus paving the way for biological applications, and were characterized by several spectroscopic, microscopic, thermogravimetric, and rheological techniques. In vitro experiments demonstrated excellent cytocompatibility. [ABSTRACT FROM AUTHOR]

D-Amino acids are regulatory molecules that affect biological processes. Therefore, being able to accurately detect and quantify these compounds is important for understanding their impact on nutrition and health. There is a paucity of information regarding d-amino acids in human milk. We developed a fast method for simultaneous analysis of amino acid enantiomers in human milk using liquid chromatography with tandem mass spectrometry. The method enables the separation of 41 amino acids without chemical derivatization. Our results revealed that human milk from mothers of preterm infants contains concentrations of d-amino acids that range from 0.5 to 45% that of their l-counterparts and that levels of most d-amino acids decrease as the milk production matures. Moreover, we found that Holder pasteurization of milk does not cause racemization of l-amino acids. To our knowledge, this is the first study to describe percentages of d-amino acid levels in human milk; changes in d-amino acid concentration as the milk matures; and the effect of Holder pasteurization on d- and l-amino acid concentrations in human milk. [ABSTRACT FROM AUTHOR]

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This study aimed to determine the effects of D-tyrosine, D-aspartic acid, D-tryptophan and D-leucine on biofilm formation of mixed microorganisms. Results showed that, in the attachment stage, D-amino acids caused significant reduction in adhesion efficiency of mixed microorganisms to the membrane surface. Moreover, D-amino acids have a promoting effect on the reversible adhesion of mixed microorganisms. The addition of D-amino acid generally inhibited the biofilm biomass, of which D-tyrosine has the best inhibition effect. With the effect of D-tyrosine, D-aspartic acid, D-tryptophan and D-leucine, the protein in extracellular polymeric substance (EPS) decreased by 8.21%, 7.65%, 3.51% and 11.31%, respectively. The carbohydrates in EPS decreased by 29.53%, 21.44%, 14.60% and 10.54%, respectively. The results of excitation-emission matrix spectra (EEMs) suggested that the structural properties of the tyrosine-like proteins, tryptophan-like protein and humic-like acid might have changed by the D-amino acids. HIGHLIGHTS Biofilm formation of microorganisms with 24 h D-amino acids exposure were discussed.; D-amino acids reduced adhesion efficiency and increased desorption efficiency.; The biofilm biomass decreased with the addition of D-amino acids.; D-amino acids inhibited the secretion of carbohydrates and protein in EPS.;

d-Amino acids are pharmaceutically important building blocks, leading to a great deal of research efforts to develop cost-effective synthetic methods. Preparation of d-amino acids by deracemization has been conceptually attractive owing to facile synthesis of racemic amino acids by Strecker synthesis. Here, we demonstrated biocatalytic deracemization of aliphatic amino acids into d-enantiomers by running cascade reactions; (1) stereoinversion of l-amino acid to a d-form by amino acid dehydrogenase and ω-transaminase and (2) regeneration of NAD+ by NADH oxidase. Under the cascade reaction conditions containing 100 mM isopropylamine and 1 mM NAD+, complete deracemization of 100 mM dl-alanine was achieved after 24 h with 95% reaction yield of d-alanine (> 99% eeD, 52% isolation yield). Graphical Abstract: [Figure not available: see fulltext.].