Aug 2026· Water Research· Vol 306, pp.
126605
· 0 citations· 77 references
Medicine
TL;DR
It is indicated that protein-associated binding states should be considered when optimizing UV-AOPs for odor control in bloom-impacted drinking water sources, as weakening protein-2-MIB associations may enhance 2-MIB accessibility to reactive species and thereby improve oxidative removal of 2-MIB.
Abstract
2-Methylisoborneol (2-MIB), predominantly produced by cyanobacteria in drinking water sources, is a major off-flavor compound responsible for earthy-musty odors at extremely low concentrations. Recent evidence suggests that a substantial fraction of 2-MIB exists in a bound state associated with algal-derived proteins, yet the mechanism governing this association and its influence on 2-MIB removal during advanced oxidation processes (AOPs) remain poorly understood. In this study, the influence of protein binding on 2-MIB degradation was systematically investigated in UV/H2O2 and UV/Cl2 processes using C-phycocyanin (C-PC) as a representative algal protein. Relative to the freshly mixed system, the pre-equilibrated 2-MIB/C-PC system showed consistently lower 2-MIB degradation efficiencies and apparent reaction rate constants under both UV-AOPs. At an initial 2-MIB concentration of 1.0 μg/L, C-PC binding decreased the 2-MIB removal efficiency at 40 min in the UV/H2O2 and UV/Cl2 processes from 85.8% to 74.8% and from 63.0% to 57.3%, respectively. Spectroscopic analyses, molecular docking, and molecular dynamics simulations collectively showed that 2-MIB could be accommodated within a hydrophobic pocket of C-PC, where van der Waals interactions dominated the overall binding stability. Density functional theory calculations further revealed that a residue-specific hydrogen bond involving lysine altered the electrostatic potential around the hydroxyl group of 2-MIB and reduced its local radical reactivity. In contrast, free lysine did not form a stable association with 2-MIB in bulk water, highlighting the essential role of the confined protein microenvironment. These findings indicate that protein-associated binding states should be considered when optimizing UV-AOPs for odor control in bloom-impacted drinking water sources, as weakening protein-2-MIB associations may enhance 2-MIB accessibility to reactive species and thereby improve oxidative removal of 2-MIB.
The interaction between human carbonic anhydrase II (hCA II) and 1-(4-chloro-benzenesulfonyl)-4-hydroxy-pyrrolidine-2-carboxylic acid (CBHPCA) was inspected by applying different spectroscopic methods and molecular docking, as well. Kinetic studies revealed that CBHPCA inhibits hCA II esterase activity through a linear competitive mode. Fluorescence analyses showed that CBHPCA quenches the enzyme's intrinsic fluorescence through a static quenching mechanism. Thermodynamic analyses indicated that hydrogen bonding and van der Waals interactions stabilize the CBHPCA-enzyme complex. Protein surface hydrophobicity (PSH) index of the enzyme reduced upon CBHPCA interaction, as shown by a fluorometric study using 1-anilinonaphthalene-8-sulfonic acid. Oxidation studies with N-boromosuccinimide (NBS) revealed a decrease in the number of attainable tryptophans of the enzyme in the presence of CBHPCA. Far-UV circular dichroism (CD) spectroscopy indicated a rise in the α-helicity of hCA II upon CBHPCA binding, while near-UV CD spectra showed decreased flexibility of the enzyme's tertiary structure. Acrylamide quenching experiments demonstrated reduced accessibility of tryptophans of the enzyme to the quencher, consistent with NBS experiment results. Guanidine hydrochloride denaturation experiments showed increased thermodynamic stability of the CBHPCA-enzyme complex compared to the enzyme alone. Fourier transform infrared experiments confirmed some increment in the α-helicity of the enzyme induced by CBHPCA. Molecular docking study revealed that hydrogen bonding and van der Waals interactions caused anchoring of CBHPCA to the enzyme's active site. It seems that structural compactness induced by CBHPCA binding to the enzyme may be accountable for its increased thermodynamic stability.
Maryam Ahmadian, S. Ghobadi, Reza Khodarahmi et al.· Journal of Biomolecular Stru...· 0 citations
Atmospheric ozonolysis of halogenated monoterpenes from marine red macroalgae proceeds through pre-reactive complexes, primary ozonides, Criegee intermediates, and carbonyl products. Structure–activity relationship (SAR) schemes, such as that of Khan et al. (2022) for nineteen Plocamium-derived monoterpenes, return only a single rate coefficient per channel, with no information on intermediates, energy partitioning or pressure dependence. Here all three ozone-attack channels of Compound 1, 5,6-dichloro-2-chloromethylene-6-methyl-octa-3,7-dienal (C₁₀H₁₁Cl₃O) — the terminal Δ⁷ vinyl, the internal Δ³ double bond, and the chloromethylene Δ¹ group — are characterized with a quantum-chemical/master-equation workflow (ωB97X-D3BJ/def2-TZVP; DLPNO-CCSD(T)/def2-TZVPP; ORCA 6.1; MESMER 7.1) on a single workstation. All three channels proceed over tight, first-order cycloaddition transition states to deep primary ozonides and on to chlorinated carbonyl + Criegee pairs. The internal Δ³ cycloaddition, initially suspected to be barrierless along the single-bond approach coordinate, is shown by a synchronous two-bond scan, transition-state optimization and intrinsic-reaction-coordinate analysis to possess a genuine concerted ring-closure saddle (one imaginary mode, −310 cm⁻¹) at +9.57 kcal mol⁻¹ — the highest of the three entrance barriers, above the terminal Δ⁷ (+7.02) and chloromethylene Δ¹ (+6.67 kcal mol⁻¹) channels. The resulting 298 K, 760 Torr rate coefficients are kΔ⁷ = 2.50 × 10⁻²¹, kΔ¹ = 1.45 × 10⁻²² and kΔ³ = 1.53 × 10⁻²³ cm³ molecule⁻¹ s⁻¹, giving a channel ordering Δ⁷ > Δ¹ > Δ³ (≈94 : 5 : 1). This confirms the SAR/MCM picture of Khan et al. on the dominant site — the terminal Δ⁷ vinyl — but reassigns the minor chemistry: the internal Δ³ double bond, treated by SAR/MCM as the secondary site (~7%), is found to be the slowest channel (~1%), while the chloromethylene Δ¹ group not considered by SAR emerges as the true secondary channel (~5%). Notably, the ordering is not set by barrier height alone. Although Δ¹ has the lowest barrier, its tighter transition state (a smaller rovibrational partition function) makes it slower than Δ⁷, so the channel selectivity reflects a balance of entropic and enthalpic factors rather than barrier height in isolation. Pressure-dependent collisional stabilization of the primary ozonides — inaccessible to SAR — is significant at atmospheric pressure, with prompt Criegee yields of ~28% (Δ⁷). Benchmarking the identical workflow against ethene ozonolysis reproduces the experimental barrier to within 0.4 kcal mol⁻¹ (5.3 versus ~4.95 kcal mol⁻¹), indicating that the total rate, which lies about three orders of magnitude below the group-additivity SAR estimate, reflects overestimation by the SAR scheme for this chlorinated, conjugated substrate rather than an offset in the computed barriers.
A. Bacak· Journal of the Turkish Chemi...· 0 citations
ABSTRACT The organic booster biocide DCOIT (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one) is widely used in marine antifouling systems, yet its ecological impacts on sediment microbiomes remain poorly understood. Here, we integrated absolute quantitative 16S rRNA gene sequencing, metagenomics, and enzyme activity assays to examine microbial responses to DCOIT exposure (0–50 μg/g sediment) over 30 days. DCOIT induced oxidative stress and bioenergetic impairment, accompanied by reduced microbial activity and inhibition of key enzyme-mediated processes involved in organic matter turnover and nitrogen transformation. Absolute quantification revealed a compensatory increase in total microbial abundance by Day 30, despite persistent diversity loss and community restructuring. Metagenomic analysis showed that DCOIT disturbed functional potentials related to carbon and nitrogen cycling. Kordiimonas, Aliikangiella, and Neptuniibacter emerged as potential contributors to nitrogen transformation, whereas Marinobacter was more closely associated with potential DCOIT transformation. DCOIT exposure also enriched adaptive traits, including chemotaxis, motility, quorum sensing, and biofilm regulation, and was accompanied by increased multidrug efflux systems and heavy metal resistance determinants. Our findings provide novel insights into the ecotoxicological risks of isothiazolinone biocides and highlight the potential for DCOIT to undermine sediment ecosystem functions and microbial habitat health. Given its extensive application, this study emphasizes the need to consider the microbial ecological consequences of DCOIT accumulation in seafloor environments. IMPORTANCE DCOIT is widely used in marine antifouling coatings and can accumulate in benthic sediments, yet its effects on sediment microbiomes remain poorly defined. This study shows that DCOIT disrupts microbial energy status, enzyme activities, community structure, and nitrogen-cycling functions while selecting for adaptive traits and resistance-related determinants. By integrating absolute quantification, metagenomics, and enzyme assays, our work demonstrates that DCOIT poses microbial ecological risks beyond toxicity to macroorganisms and should be considered in assessments of antifouling biocides. DCOIT is widely used in marine antifouling coatings and can accumulate in benthic sediments, yet its effects on sediment microbiomes remain poorly defined. This study shows that DCOIT disrupts microbial energy status, enzyme activities, community structure, and nitrogen-cycling functions while selecting for adaptive traits and resistance-related determinants. By integrating absolute quantification, metagenomics, and enzyme assays, our work demonstrates that DCOIT poses microbial ecological risks beyond toxicity to macroorganisms and should be considered in assessments of antifouling biocides.
Jiaxin Zhang, Libing Cai, Lin Wang et al.· Applied and Environmental Mi...· 0 citations
The compound N-(3-aminopropyl)-2-(4-allyl-2-methoxyphenoxy)acetamide (4) was synthesized from eugenol through a three-step reaction. Possessing both amide and amine groups, the molecule provides effective hydrogen-bond donor sites suitable for anion recognition. The binding behaviour of compound 4 toward F⁻, CN⁻, AcO⁻, SO₄²⁻, and H₂PO₄⁻ was examined using 1H-NMR spectroscopy. No significant spectral changes were observed upon addition of F⁻, AcO⁻, or SO₄²⁻, indicating minimal or no interaction. In contrast, the introduction of CN⁻ and H₂PO₄⁻ produced notable chemical shift variations, consistent with hydrogen-bond formation and host-guest complexation. To further elucidate these interactions, density functional theory (DFT) calculations were performed at the aug-cc-pVDZ level. Computational models revealed that F⁻ and AcO⁻ induce cleavage of the amide N–H bond through strong hydrogen bonding and partial covalent character, whereas CN⁻ and H₂PO₄⁻ primarily engage in hydrogen-bonding interactions without bond cleavage. Gauge-independent atomic orbital (GIAO) calculations predicted substantial downfield shifts of the amide proton, from 4.72 ppm in the free receptor to 15.5, 10.89, 16.54, and 12.27 ppm for F⁻, CN⁻, AcO⁻, and H₂PO₄⁻, respectively. Overall, both experimental and computational findings demonstrate that compound 4 functions as an effective receptor for CN⁻ and H₂PO₄⁻, with strong theoretical binding responses also observed for F⁻ and AcO⁻.
V. Suryanti, L. Wijayanti, Yoga Royandana Firdaus et al.· Journal of Multidisciplinary...· 0 citations
Modified mycotoxins are structurally altered derivatives of their parent mycotoxins. They are commonly co-occurring with the parent mycotoxins in foods and feeds, posing a potential risk to food safety. Therefore, effective strategies for their control are of great significance; however, no relevant studies have been reported to date. In this study, we reported a green and efficient bioremediation strategy targeting three representative modified mycotoxins, 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON), and deoxynivalenol-3-glucoside (D3G). A laccase mediator system, Lac-W-acetosyringone (Lac-W-AS), was constructed to achieve effective degradation of these mycotoxins. After optimization of reaction conditions (pH 7.0, 40°C, 2 U/mL Lac-W, 0.5 mM AS and 36 hours), the degradation rates of 3-ADON, 15-ADON, and D3G reached 97.8 %, 93.2 %, and 88.5 %, respectively. Cell viability assays using porcine intestinal epithelial cells (IPEC-J2) confirmed that the Lac-W-AS significantly reduced the cytotoxicity of all three mycotoxins, demonstrating effective detoxification. Furthermore, high-resolution mass spectrometry identified a degradation product of 3-ADON, and structural analysis of the product suggested that the detoxification mechanism of Lac-W-AS likely proceeded via a free radical-mediated pathway. This study provides a successful demonstration of simultaneous and efficient detoxification of three modified mycotoxins.
N-(1, 3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and its transformation product 6PPD-quinone are emerging tire-derived contaminants with disruptive effects on glucose metabolism. Given that α-glucosidase is key to blood glucose homeostasis, this study used multivariate methods to explore how 6PPD and 6PPD-quinone alter its conformation and function. The results show that the ligands spontaneously bind to α-glucosidase via hydrophobic forces, with binding constants (Ka) of 7.312 × 105 M-1 and 5.214 × 104 M-1 at 310 K for 6PPD and 6PPD-quinone, respectively. However, they exert opposing functional effects: 6PPD enhances enzyme activity, whereas 6PPD-quinone exerted an inhibitory effect. Computational alanine scanning mutagenesis (ASM) revealed distinct binding interactions between 6PPD/6PPD-quinone and the catalytic triad of α-glucosidase (Asp214, Glu276, and Asp349), which may partly explain their opposing regulatory effects on α-glucosidase activity. Additionally, conformational analysis indicated that both compounds induce a more compact and stable conformation of α-glucosidase, likely attributed to an increase in α-helix content. Specifically, the α-helix content rose from 25.3 ± 0.2% to 29.7 ± 0.4% in the 6PPD group, and to 27.2 ± 0.3% in the 6PPD-quinone group. Free energy landscape (FEL) analysis further demonstrated that the presence of both compounds shifted the system from two dominant conformations to a single dominant state. Collectively, these findings reveal distinct mechanisms by which tire-derived contaminants modulate α-glucosidase, providing insights into their potential to disrupt glucose homeostasis.
Yan Zhou, Jingfei Shi, Yukun Ma et al.· International Journal of Bio...· 0 citations
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