The enticing aroma of truffles is a key factor for their culinary value. Although all truffle species tend to be pricy, the most intensely aromatic species are the most sought after. Research into ...the aroma of truffles encompasses various disciplines including chemistry, biology, and sensory science. This study focusses on the chemical composition of the aroma of black truffles (
) and the changes occurring under different storage conditions. For this, truffle samples were stored under different treatments, at different temperatures, and measured over a total storage time of 12 days. Measurements of the truffle aroma profiles were taken with SPME/GC-MS at regular intervals. To handle the ample data collected, a systematic approach utilizing multivariate data analysis techniques was taken. This approach led to a vast amount of data which we made publicly available for future exploration. Results reveal the complexity of aroma changes, with 695 compounds identified, highlighting the need for a comprehensive understanding. Principal component analyses offer initial insights into truffle composition, while individual compounds may serve as markers for age (formic acid, 1-methylpropyl ester), freshness (2-Methyl-1-propanal; 1-(methylthio)-propane), freezing (tetrahydrofuran), salt treatment (1-chloropentane), or heat exposure (4-hydroxy-3-methyl-2-butanone). This research suggests that heat treatment or salt contact significantly affects truffle aroma, while freezing and cutting have less pronounced effects in comparison. The enrichment of compounds showing significant changes during storage was investigated with a metabolomic pathway analysis. The involvement of some of the enriched compounds on the pyruvate/glycolysis and sulfur pathways was shown.
Pseudomonas aeruginosa is a significant threat in both healthcare and industrial biofouling. Surface attachment of P. aeruginosa is particularly problematic as surface association induces virulence ...and is necessary for the ensuing process of biofilm formation, which hampers antibiotic treatments. Previous efforts have searched for dispersal agents of mature biofilm collectives, but there are no known factors that specifically disperse individual surface-attached P. aeruginosa. In this study, we develop a quantitative single-cell surface-dispersal assay and use it to show that P. aeruginosa itself produces factors that can stimulate its dispersal. Through bioactivity-guided fractionation, mass spectrometry, and nuclear magnetic resonance, we elucidated the structure of one such factor, 2-methyl-4-hydroxyquinoline (MHQ). MHQ is an alkyl quinolone with a previously unknown activity and is synthesized by the PqsABC enzymes. Pure MHQ is sufficient to disperse P. aeruginosa, but the dispersal activity of natural P. aeruginosa conditioned media requires additional factors. Whereas other alkyl quinolones have been shown to act as antibiotics or membrane depolarizers, MHQ lacks these activities and known antibiotics do not induce dispersal. In contrast, we show that MHQ inhibits the activity of Type IV Pili (TFP) and that TFP targeting can explain its dispersal activity. Our work thus identifies single-cell surface dispersal as a new activity of P. aeruginosa-produced small molecules, characterizes MHQ as a promising dispersal agent, and establishes TFP inhibition as a viable mechanism for P. aeruginosa dispersal.
The coupling of dibromohexabenzocoronene (Br2-HBC) as a precursor molecule is investigated by scanning tunneling microscopy (STM) on two noble metal surfaces: Au(111) and Cu(111). It is found that ...the on-surface polymerization of molecular building blocks equipped with halogen atoms is strongly influenced by the choice of the substrate. While on Au(111) a heating step of up to 520K is required to activate the molecules and form polymers, on Cu(111) the catalytic reactivity causes activation already below room temperature. Due to the different substrates, the intramolecular bonds in the polymers between the HBC units differ: The HBC molecules are covalently coupled on Au(111) while on Cu(111) a copper adatom mediates the bonding. This effect is proven by the comparison with gas phase calculations and by lateral manipulation with the STM tip. The choice of the substrate thus does not only define the activation temperature but also lead to different bonding strengths between the molecular building blocks.
•Revealing the role of the surface during on-surface polymerization•Molecular dehalogenation starts on Cu(111) at lower temperatures than on Au(111).•On Cu(111) a copper adatom mediates a metal–ligand bond between the HBC molecules.•On Au(111) a covalent bond is formed between the HBC molecules.
Introduction to Optical Tweezers Koch, Matthias D; Shaevitz, Joshua W
Methods in molecular biology (Clifton, N.J.),
2017, Letnik:
1486
Journal Article
Thirty years after their invention by Arthur Ashkin and colleagues at Bell Labs in 1986 1, optical tweezers (or traps) have become a versatile tool to address numerous biological problems. Put ...simply, an optical trap is a highly focused laser beam that is capable of holding and applying forces to micron-sized dielectric objects. However, their development over the last few decades has converted these tools from boutique instruments into highly versatile instruments of molecular biophysics. This introductory chapter intends to give a brief overview of the field, highlight some important scientific achievements, and demonstrate why optical traps have become a powerful tool in the biological sciences. We introduce a typical optical setup, describe the basic theoretical concepts of how trapping forces arise, and present the quantitative position and force measurement techniques that are most widely used today.
Identifying the fate of agrochemicals is important to understand their potential risk for living organisms. We report here new photodegradation products (PPs) of the fungicide fluopyram. The PPs were ...produced by irradiating a fluopyram standard in 0.1% acetonitrile aqueous media by a 150-W medium pressure Hg-lamp that emits wavelengths between 200⁻280 nm. The structural elucidation of PPs was achieved by combining the retention time, isotopic pattern, targeted fragmentation, and accurate mass measurements using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and high resolution-MS (HRMS). In addition to previously known PPs, seven new PPs of fluopyram were identified in this work: mainly dihydroxyl and hydroxylimide fluopyram as well as mono, di, and trihydroxyl lactam. Additionally, two PPs were found to be formed by rearrangement after the loss of H₂C=CH₂. Hence, the results of the work contribute to extending the current knowledge regarding the photoinduced fate of agrochemicals, and fluopyram in particular.
The great metabolic versatility of the purple non-sulfur bacteria is of particular interest in green technology. Rhodospirillum rubrum S1H is an α-proteobacterium that is capable of ...photoheterotrophic assimilation of volatile fatty acids (VFAs). Butyrate is one of the most abundant VFAs produced during fermentative biodegradation of crude organic wastes in various applications. While there is a growing understanding of the photoassimilation of acetate, another abundantly produced VFA, the mechanisms involved in the photoheterotrophic metabolism of butyrate remain poorly studied.
In this work, we used proteomic and functional genomic analyses to determine potential metabolic pathways involved in the photoassimilation of butyrate. We propose that a fraction of butyrate is converted to acetyl-CoA, a reaction shared with polyhydroxybutyrate metabolism, while the other fraction supplies the ethylmalonyl-CoA (EMC) pathway used as an anaplerotic pathway to replenish the TCA cycle. Surprisingly, we also highlighted a potential assimilation pathway, through isoleucine synthesis and degradation, allowing the conversion of acetyl-CoA to propionyl-CoA. We tentatively named this pathway the methylbutanoyl-CoA pathway (MBC). An increase in isoleucine abundance was observed during the early growth phase under butyrate condition. Nevertheless, while the EMC and MBC pathways appeared to be concomitantly used, a genome-wide mutant fitness assay highlighted the EMC pathway as the only pathway strictly required for the assimilation of butyrate.
Photoheterotrophic growth of Rs. rubrum with butyrate as sole carbon source requires a functional EMC pathway. In addition, a new assimilation pathway involving isoleucine synthesis and degradation, named the methylbutanoyl-CoA (MBC) pathway, could also be involved in the assimilation of this volatile fatty acid by Rs. rubrum.
The purpose of this study was to describe a novel device that may serve as an alternative to Descemet membrane endothelial keratoplasty (DMEK) for the treatment of chronic corneal edema.
The EndoArt ...(EyeYon Medical, Israel) is a flexible, 50-μm thin artificial endothelial layer that matches the cornea's posterior curvature and functions as a fluid barrier at the posterior stroma, replacing the diseased endothelium. Similar to a DMEK approach, it is implanted into the anterior chamber, carefully positioned on the posterior stroma, and secured using an air-gas mixture. Two patients with chronic corneal edema resulting from endothelial decompensation underwent implantation of the new artificial lamella.
In patient 1, the central corneal thickness (CCT) decreased from 730 μm preoperatively to 593 μm at 1 day postoperatively. In patient 2, the CCT decreased from 761 μm preoperatively to 487 μm at 1 day postoperatively. Both patients reported high satisfaction and an overall brighter visual quality. Although dislocation of the lamella occurred in both cases, the CCT was promptly restored after a repositioning procedure and remained stable at the 17-month follow-up (CCT of 526 and 457 μm for patients 1 and 2, respectively). In contrast to DMEK donor tissue, the artificial lamella is sufficiently robust to allow easy intraocular manipulation without the risk of damaging the implant. It is easily removable and does not require any immunosuppressive treatment because of its nonbiological nature.
Implantation of the EndoArt led to rapid corneal deturgescence and CCT restoration, presenting a possible option for patients with chronic corneal edema.
Cells regularly experience fluid flow in natural systems. However, most experimental systems rely on batch cell culture and fail to consider the effect of flow-driven dynamics on cell physiology. ...Using microfluidics and single-cell imaging, we discover that the interplay of physical shear rate (a measure of fluid flow) and chemical stress trigger a transcriptional response in the human pathogen
. In batch cell culture, cells protect themselves by quickly scavenging the ubiquitous chemical stressor hydrogen peroxide (H
O
) from the media. In microfluidic conditions, we observe that cell scavenging generates spatial gradients of H
O
. High shear rates replenish H
O
, abolish gradients, and generate a stress response. Combining mathematical simulations and biophysical experiments, we find that flow triggers an effect like "wind-chill" that sensitizes cells to H
O
concentrations 100 to 1,000 times lower than traditionally studied in batch cell culture. Surprisingly, the shear rate and H
O
concentration required to generate a transcriptional response closely match their respective values in the human bloodstream. Thus, our results explain a long-standing discrepancy between H
O
levels in experimental and host environments. Finally, we demonstrate that the shear rate and H
O
concentration found in the human bloodstream trigger gene expression in the blood-relevant human pathogen
, suggesting that flow sensitizes bacteria to chemical stress in natural environments.
We aimed to evaluate the impact of knee periprosthetic joint infection (PJI) by assessing the patients' long-term quality of life and explicitly their psychological wellbeing after successful ...treatment.
Thirty-six patients with achieved eradication of infection after knee PJI were included. Quality of life was evaluated with the EQ-5D and SF-36 outcome instruments as well as with an ICD-10 based symptom rating (ISR) and compared to normative data.
At a follow-up of 4.9 ± 3.5 years the mean SF-36 score was 24.82 ± 10.0 regarding the physical health component and 46.16 ± 13.3 regarding the mental health component compared to German normative values of 48.36 ± 9.4 (
< 0.001) and 50.87 ± 8.8 (
= 0.003). The mean EQ-5D index reached 0.55 ± 0.33 with an EQ-5D VAS rating of 52.14 ± 19.9 compared to reference scores of 0.891 (
< 0.001) and 68.6 ± 1.1 (
< 0.001). Mean scores of the ISR revealed the psychological symptom burden on the depression scale.
PJI patients still suffer from significantly lower quality of life compared to normative data, even years after surgically successful treatment. Future clinical studies should focus on patient-related outcome measures. Newly emerging treatment strategies, prevention methods, and interdisciplinary approaches should be implemented to improve the quality of life of PJI patients.
Summary
Bactofilins are fibre‐forming bacterial cytoskeletal proteins. Here, we report the structural and biochemical characterization of MXAN_7475 (BacM), one of the four bactofilins of Myxococcus ...xanthus. Absence of BacM leads to a characteristic ‘crooked’ cell morphology and an increased sensitivity to antibiotics targeting cell wall biosynthesis. The absence of the other three bactofilins MXAN_4637–4635 (BacN‐P) has no obvious phenotype. In M. xanthus, BacM exists as a 150‐amino‐acid full‐length version and as a version cleaved before Ser28. In the cell, native BacM forms 3 nm wide fibres, which assemble into bundles forming helix‐like cytoplasmic cables throughout the cell, and in a subset of cells additionally a polarly arranged lateral rod‐like structure. Isolated fibres consist almost completely of the N‐terminally truncated version, suggesting that the proteolytic cleavage occurs before or during fibre formation. Fusion of BacM to mCherry perturbs BacM function and cellular fibre arrangement, resulting for example in the formation of one prominent polar corkscrew‐like structure per cell. Immunofluorescence staining of BacM and MreB shows that their cellular distributions are not matching. Taken together, these data suggest that rod‐shaped bacteria like M. xanthus use bactofilin fibres to achieve and maintain their characteristic cell morphology and cell wall stability.
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