Microplastic accumulation by tube-dwelling, suspension feeding polychaetes from the sediment surface: A case study from the Norwegian Continental Shelf.

Sediment samples (0-1 cm) and tube-dwelling polychaetes from the Norwegian Continental Shelf and the Barents Sea were collected, including areas close to oil and gas installations and remote locations. Microplastics (≥45 µm) were found in quantifiable levels in 27 of 35 sediment samples, from 0.039 to 3.4 particles/gdw (dw = dry weight); and in 9 of 10 pooled polychaete samples, from 11 to 880 particles/gww (ww = wet weight). Concentrations were significantly higher in tube-dwelling polychaetes than sediments from the same locations (p<0.0097) by orders of magnitude. To quantify this factor increase in polychaetes, a Biota-Sediment Particle Enrichment Factor (BSPEF) is introduced, which ranged from 100 to 11000 gdw/gww (280-31000 gdw/gdw). Higher microplastic levels were observed in polychaete tube than in soft tissue (n=4). The feeding behavior and life cycle of tube-dwelling polychaetes could have an important influence on the transport, distribution and food-chain dynamics of microplastics on the seafloor.

GADL1 is a multifunctional decarboxylase with tissue-specific roles in ß-alanine and carnosine production.

Carnosine and related ß-alanine-containing peptides are believed to be important antioxidants, pH buffers, and neuromodulators. However, their biosynthetic routes and therapeutic potential are still being debated. This study describes the first animal model lacking the enzyme glutamic acid decarboxylase-like 1 (GADL1). We show that Gadl1-/- mice are deficient in ß-alanine, carnosine, and anserine, particularly in the olfactory bulb, cerebral cortex, and skeletal muscle. Gadl1-/- mice also exhibited decreased anxiety, increased levels of oxidative stress markers, alterations in energy and lipid metabolism, and age-related changes. Examination of the GADL1 active site indicated that the enzyme may have multiple physiological substrates, including aspartate and cysteine sulfinic acid. Human genetic studies show strong associations of the GADL1 locus with plasma levels of carnosine, subjective well-being, and muscle strength. Together, this shows the multifaceted and organ-specific roles of carnosine peptides and establishes Gadl1 knockout mice as a versatile model to explore carnosine biology and its therapeutic potential.

9-Acridinemethanamine and Acridine-9-Carboxaldehyde as Potential Fluorescence Lifetime pH Indicators.

A significant challenge concerning the development of fluorescence lifetime (FL) based pH sensors is the paucity of fluorophores with sufficiently large FL variation with pH. Acridine is amongst the indicators with highest fluoresce lifetime responses to pH, with a change in lifetime of about 13 ns within a pH range of 5-8. Here we examine the two acridine derivatives, 9-acridinemethanamine (9-AMA) and acridine-9-carbaldehyde (9-ACA) in terms of their FL pH sensitivity and pH sensing range. Both indicators are characterized when dissolved in buffer solutions, as well as when immobilized in support materials. 9-AMA has a change in FL of 11 ns between pH 2-5, both when dissolved in solution and when immobilized in surfactant-filled mesoporous silica. The FL of 9-ACA is not sensitive to pH when dissolved in buffer solutions; however, when covalently bound to amine-modified silica, its FL changes 15 ns between pH 3-6. 9-AMA and 9-ACA represent promising FL in the pH range of pH 2-6, and could potentially form the basis of new FL pH sensors. Graphical Abstract.

Bioactive Metabolites of Marine Origin Have Unusual Effects on Model Membrane Systems.

Marine sponges and soft corals have yielded novel compounds with antineoplastic and antimicrobial activities. Their mechanisms of action are poorly understood, and in most cases, little relevant experimental evidence is available on this topic. In the present study, we investigated whether agelasine D (compound 1) and three agelasine analogs (compound 2-4) as well as malonganenone J (compound 5), affect the physical properties of a simple lipid model system, consisting of dioleoylphospahtidylcholine and dioleoylphosphatidylethanolamine. The data indicated that all the tested compounds increased stored curvature elastic stress, and therefore, tend to deform the bilayer which occurs without a reduction in the packing stress of the hexagonal phase. Furthermore, lower concentrations (1%) appear to have a more pronounced effect than higher ones (5-10%). For compounds 4 and 5, this effect is also reflected in phospholipid headgroup mobility assessed using 31P chemical shift anisotropy (CSA) values of the lamellar phases. Among the compounds tested, compound 4 stands out with respect to its effects on the membrane model systems, which matches its efficacy against a broad spectrum of pathogens. Future work that aims to increase the pharmacological usefulness of these compounds could benefit from taking into account the compound effects on the fluid lamellar phase at low concentrations.

A Broad-Range Fluorescence Lifetime pH Sensing Material Based on a Single Organic Fluorophore.

A general drawback for optical based pH sensors is that their response is typically limited to within 2-3 pH units centered around the pKa of the indicator. Fluorescence lifetime (FL) is a particularly compelling basis for highly stable pH sensors since this is an intrinsic property of the indicator molecule. Here we demonstrate that it is possible to broaden the sensing range of FL based sensors significantly by placing the indicator in a support material where the indicator's chemical environment itself changes with pH. For acridine immobilized in amine-modified porous silica, a total FL change of 20 ns in the pH range 2-12 is achieved. A linear pH vs FL relationship is observed with three break points occurring at pH 4, 6 and 9 that are related to the pKa values of the indicator and the silica material. This proves the concept that tuning the fluorophore's chemical environment can broaden the FL pH sensing range, where currently available fluorophores do not cover the full pH range. Graphical Abstract.

Investigating mobility of crude oil adsorbates on mineral surfaces by NMR.

We have applied diffusion and relaxation Nuclear Magnetic Resonance experiments to investigate the translational and rotational mobility of adsorbents on quartz and calcite mineral surfaces. On both surfaces it was found that water is the dominant molecule. On the quartz surface the majority of water molecules have a relatively high degree of both rotational and translational mobility, while a minor fraction of water molecules, and all hydrocarbon molecules, have a significantly lower mobility. On the calcite surface the translational mobility is very low for all the adsorbed molecules, while there is a large diversity in rotational mobility, indicating that the hydrocarbon molecules are strongly attached to the surface, but that some part of each molecule still have a large degree of rotational mobility. Diffusion and relaxation experiments give a detailed description of both the molecular mobility of adsorbed species on these mineral surfaces, which leads to new insight with respect to aging processes on a molecular level.

Swollen micelles and alcohol-surfactant co-adsorption: structures and mechanisms from liquid- and solid-state 1H-1H NMR spectroscopy.

Mixtures of surfactants and medium chained alcohols display an anomalous phase behaviour, with the formation of swollen micelles in mid-range surfactant concentrations, which transition into larger non-swollen aggregates when the surfactant concentration increases above a critical point. These alcohols also affect the adsorption behaviour of the surfactants. In this study, intermolecular proximities are measured for such systems by 1H-1H NMR dipolar correlation experiments, giving molecular localizations. The medium chained 1-heptanol and an anionic surfactant sodium dodecyl sulphate (SDS) are studied, both solubilized and adsorbed on alumina. Nuclear Overhauser Effect Spectroscopy (NOESY) shows that 1-heptanol localizes in both the palisade layer and in the core of SDS micelles when the 1-heptanol : SDS mole ratio increases beyond 2. The micelle diameter then increases with increasing 1-heptanol : SDS mole ratios due to more 1-heptanol partitioning in the micelle interior. When the micelle diameter increases beyond ∼6 nm, some SDS moves into the micelle interior, which may be a driving force for the structural transition at higher SDS concentrations. After being adsorbed on alumina, 1H-1H double-quantum magic angle spinning (DQ MAS) shows that SDS/1-heptanol bilayers are formed where 1-heptanol localizes in the palisade layer only, but with slightly different localizations compared to that in micelles. Three different 1-heptanol environments are identified on the surface by 2H NMR using 2H labelled 1-heptanol. However, in contrast to in solution, no 1-heptanol adsolubilizes in the bilayer interior.

Effects and Location of Coplanar and Noncoplanar PCB in a Lipid Bilayer: A Solid-State NMR Study.

Coplanar and noncoplanar polychlorinated biphenyls (PCBs) are known to have different routes and degree of toxicity. Here, the effects of noncoplanar PCB 52 and coplanar PCB 77 present at 2 mol % in a model system consisting of POPC liposomes (50% hydrated) are investigated by solid-state (13)C and (31)P NMR at 298 K. Both PCBs intercalate horizontally in the outer part of the bilayer, near the segments of the acyl chain close to the glycerol group. Despite similar membrane locations, the coplanar PCB 77 shows little effect on the bilayer properties overall, except for the four nearest neighboring lipids, while the effect of PCB 52 is more dramatic. The first ∼2 layers of lipids around each PCB 52 in the bilayer form a high fluidity lamellar phase, whereas lipids beyond these layers form a lamellar phase with a slight increase in fluidity compared to a bilayer without PCB 52. Further, a third high mobility domain is observed. The explanation for this is the interference of several high fluidity lamellar phases caused by interactions of PCB 52 molecules in different leaflets of the model bilayer. This causes formation of high curvature toroidal region in the bilayer and might induce formation of channels.

Composition and structural transitions of polyelectrolyte-surfactant complexes in the presence of fatty acid studied by NMR and cryo-SEM.

Insoluble complexes formed when a cationic polyelectrolyte is neutralized by the oppositely charged surfactant sodium dodecylethersulfate (SDES) in the presence and absence of lauric acid (LA) have been examined directly using NMR spectroscopy and cryo-SEM. Below the SDES critical micelle concentration (CMC') the insoluble complex contains about 10 times more water than just above CMC'. This is related to a structural transition of the complex, where water is contained mainly in larger compartments below CMC' and then mainly in narrower compartments above CMC'. The structure of the complex's solid matrix was monitored by recording two-dimensional T2-diffusion correlation spectra of the water proton resonance, which reveal the presence of several different water environments which correspond to different complex structures. Structural features in the micrometer range were confirmed using cryo-SEM. When LA is present, the larger water compartments seen below CMC' are to some extent present in the entire SDES concentration range, which is not the case in the absence of LA. Furthermore, the inclusion of LA into the SDES aggregates above CMC' leads to a lamellar sheetlike organization of the polyelectrolyte-stabilized surfactant phase. In the absence of LA, a stringy network of fibers is seen in cryo-SEM images, indicating a spherical or rodlike SDES phase. Consequently, the complex without LA holds about 1.7-1.9 times more water than the complex with LA above the SDES CMC'. T1 relaxation, (13)C chemical shifts, and (1)H resonance line widths of SDES in the system support the above observations. The combination of MAS NMR, T2-diffusion correlation, and cryo-SEM proved to be an effective method for studying structural transitions in the surfactant-polyelectrolyte(-LA) insoluble complexes.

The nature of fatty acid interaction with a polyelectrolyte-surfactant pair revealed by NMR spectroscopy.

The interaction mechanisms of an oppositely charged polyelectrolyte-surfactant pair and dodecanoic (lauric) acid (LA) were experimentally investigated using a combination of nuclear magnetic resonance (NMR) techniques. It is observed that LA significantly affects the interaction between the anionic surfactant sodium dodecylethersulfate (SDES) and the cationic polymer guar modified with grafted hydroxypropyl trimethylammonium chloride (Jaguar C13 BF). Typically, oppositely charged polymers and surfactants interact electrostatically at a certain surfactant concentration known as the critical aggregation concentration (CAC). Once the polymer is neutralized by the surfactant, an insoluble complex (precipitate) is observed (phase separation), and, at concentrations beyond the surfactant critical micellar concentration (CMC'), the system returns to a one phase entity. In a system in which a mixture of SDES-LA is added to the polymer, NMR data show that below the neutralization onset, some of the polymer interacts with SDES, while some of the polymer is adsorbed at the surface of LA solid aggregates present in the system. Furthermore, SDES is found to aggregate in a lamellar-like structure at the polymer side chain prior to the SDES CMC'. Above the SDES (CMC'), LA is solubilized and incorporated at the palisade region of SDES micelles. Analysis of (1)H resonances provided estimated concentrations of all species in the system phases at all stages of interaction.

Long-range surface-induced water structures and the effect of 1-butanol studied by 1H nuclear magnetic resonance.

Thin films of water between glass plates were investigated in this study with regard to water structure and dynamics in the temperature range of 278-313 K. We further investigated how addition of 1-butanol (0.05 and 0.5 M) affects the range and properties of the surface-induced water structures. From the observation of two (1)H nuclear magnetic resonance (NMR) water resonances and two relaxation components, it was found that the interfacial water exists in a two-state mixture in dynamic equilibrium, with the respective structures interpreted as being high-density water (HDW) and low-density water (LDW). In the absence of 1-butanol, the LDW state is more pronounced, with a further shift in equilibrium toward the LDW state with an increase in temperature. However, in water film samples containing 1-butanol, the HDW state dominates at low temperatures while the LDW state becomes more visible at higher temperatures. Furthermore, the addition of 1-butanol significantly increased the extent of the surface-induced water structures. NMR relaxation shows that the dynamics of water in the HDW state is significantly affected by the presence of 1-butanol and further indicates that the distribution of values for the enthalpy of activation associated with translational motion of water molecules in the HDW state is narrower in the 0.05 M 1-butanol sample than in the 0.5 M 1-butanol sample.

Thermotropic behavior of a cationic surfactant in the adsorbed and micellar state: an NMR study.

Knowledge about how temperature affects the internal structure and dynamics of surfactant aggregates can lead to a better understanding of their behavior in complex environments and processes. (13)C chemical shifts of the cationic surfactant tetradecytrimethylammonium bromide (TTAB) in micellar solution and when adsorbed on silica particles are recorded in the temperature range 8-78 °C, and give information on the conformation of the alkyl chain carbons. Adsorbed TTAB has conformational disorder similar to free TTAB at about 70 °C, with an increase in the rate of conformational changes occurring above 50 °C. Furthermore, no significant change in TTAB adsorption density was observed in the temperature range studied, and the results indicate a bilayer arrangement of the adsorbed surfactants. The number of gauche conformers increases linearly with temperature for the alkyl chain carbons in TTAB micelles. However, the total increase in gauche conformers is significantly smaller for micellar than for adsorbed TTAB within the temperature range studied. The fraction of micellized TTAB molecules in solution is found to increase with temperature.

1H NMR relaxation of water: a probe for surfactant adsorption on kaolin.

In this study, (1)H NMR is used to investigate properties of sodium dodecyl sulfate (SDS), tetradecyl trimethyl ammonium bromide (TTAB), and dodecyl trimethyl ammonium bromide (DTAB) adsorbed on kaolin by NMR T(1) and T(2) measurements of the water proton resonance. The results show that adsorbed surfactants form a barrier between sample water and the paramagnetic species present on the clay surface, thus significantly increasing the proton T(1) values of water. This effect is attributed to the amount of adsorbed surfactants and the arrangement of the surfactant aggregates. The total surface area covered by the cationic (DTAB and TTAB) and anionic (SDS) surfactants could be estimated from the water T(1) data and found to correspond to the fractions of negatively and positively charged surface area, respectively. For selected samples, the amount of paramagnetic species on the clay surface was reduced by treatment with hydrofluoric (HF) acid. For these samples, T(1) and T(2) measurements were taken in the temperature range 278-338 K, revealing detailed information on molecular mobility and nuclear exchange for the sample water that is related to surfactant behavior both on the surface and in the aqueous phase.

Water structure and dynamics at a silica surface: Pake doublets in 1H NMR spectra.

Detailed knowledge about the dynamics and structure of liquids in the vicinity of a solid surface is important in several fields of research. In this study a homogeneous model system of colloidal and nonporous silica particles with a narrow particle size distribution was used to examine such properties of adsorbed water and 1-heptanol. Doublet (1)H water resonances ("Pake doublets") indicate a preferred spatial orientation for the water molecules, as well as a lower molecular density in the surface-induced water structures compared to bulk water. These surface-induced structures are found to extend at least 8 nm from the silica surface. T(1) relaxation measurements at several temperatures indicate weaker H-bonding in the adsorbed water compared to bulk water. T(2) relaxation measurements at several temperatures reveal the presence of two water phases and give quantitative information on the mobility of water molecules and proton exchange processes. The presence of 1-heptanol changes the water characteristics, primarily in the water phase closer to the surface, where water molecules experience decreased translational and increased rotational freedom. In the absence of water, adsorbed 1-heptanol forms surface aggregates encompassing several molecular layers, where the first adsorbed layer shows severe restrictions in mobility and subsequent layers are more mobile.