Unit Area Of Interface Research Articles

Design of Cyclic Peptides Targeting Protein-Protein Interactions Using AlphaFold.

More than 930,000 protein-protein interactions (PPIs) have been identified in recent years, but their physicochemical properties differ from conventional drug targets, complicating the use of conventional small molecules as modalities. Cyclic peptides are a promising modality for targeting PPIs, but it is difficult to predict the structure of a target protein-cyclic peptide complex or to design a cyclic peptide sequence that binds to the target protein using computational methods. Recently, AlphaFold with a cyclic offset has enabled predicting the structure of cyclic peptides, thereby enabling de novo cyclic peptide designs. We developed a cyclic peptide complex offset to enable the structural prediction of target proteins and cyclic peptide complexes and found AlphaFold2 with a cyclic peptide complex offset can predict structures with high accuracy. We also applied the cyclic peptide complex offset to the binder hallucination protocol of AfDesign, a de novo protein design method using AlphaFold, and we could design a high predicted local-distance difference test and lower separated binding energy per unit interface area than the native MDM2/p53 structure. Furthermore, the method was applied to 12 other protein-peptide complexes and one protein-protein complex. Our approach shows that it is possible to design putative cyclic peptide sequences targeting PPI.

Different efficiency toward the biomimetic aerobic oxidation of benzyl alcohol in microchannel and bubble column reactors: Hydrodynamic characteristics and gas–liquid mass transfer

The selective aerobic oxidation of benzyl alcohol to benzaldehyde has attracted considerable attention because benzaldehyde is a high value-added product. The rate of this typical gas–liquid reaction is significantly affected by mass transfer. In this study, CoTPP-mediated (CoTPP: cobalt (II) meso-tetraphenylporphyrin) selective benzyl alcohol oxidation with oxygen was conducted in a membrane microchannel (MMC) reactor and a bubble column (BC) reactor, respectively. We observed that 83% benzyl alcohol was converted within 6.5 min in the MMC reactor, but only less than 10% benzyl alcohol was converted in the BC reactor. Hydrodynamic characteristics and gas–liquid mass transfer performances were compared for the MMC and BC reactors. The MMC reactor was assumed to be a plug flow reactor, and the dimensionless variance was 0.29. Compared to the BC reactor, the gas–liquid mass transfer was intensified significantly in MMC reactor. It could be ascribed to the high gas holdup (2.9 times higher than that of BC reactor), liquid film mass transfer coefficient (8.2 times higher than that of BC reactor), and mass transfer coefficient per unit interfacial area (3.8 times higher than that of BC reactor). Moreover, the Hatta number for the MMC reactor reached up to 0.61, which was about 15 times higher than that of the BC reactor. The computational fluid dynamics calculations for mass fractions in both liquid and gas phases were consistent with the experimental data.

Lattice dislocation induced misfit dislocation evolution in semi-coherent {111} bimetal interfaces

The study of dislocation plasticity mediated by semi-coherent interfaces can aid in the design of certain heterostructured materials, such as nanolaminates. The evolution of interface misfit patterns under complex stress fields arising from dislocation pileups can influence local dislocation/interface interactions, including effects of multiple incoming dislocations. This work utilizes the Concurrent Atomistic-Continuum modeling framework to probe the evolution of misfit structures at semi-coherent Ni/Cu and Cu/Ag interfaces impinged by dislocation pileups generated via nanoindentation. A continuum microrotation metric is computed at various stages of the indentation process and used to visualize the evolution of the interface misfit dislocation pattern. The stress state from approaching dislocations induces mixed contraction and expansion of misfit dislocation structures at the interface. A lower number of misfit nodes per unit interface area coincides with greater localized deformation with regard to atoms near misfit nodes for Ni/Cu. The decreased misfit node spacing for Cu/Ag alternatively distributes the restructuring associated with plastic deformation over a larger percentage of atoms at the interface. Interface sliding facilitated by misfit dislocation motion is found to facilitate deformation extending into the bulk lattices centered on misfit nodes. The depth of penetration of those fields is found to be greater for Ni/Cu than for Cu/Ag. The study of dislocation plasticity mediated by semi-coherent interfaces can aid in the design of certain heterostructured materials, such as nanolaminates. The evolution of interface misfit patterns under complex stress fields arising from dislocation pileups can influence local dislocation/interface interactions, including effects of multiple incoming dislocations. This work utilizes the Concurrent Atomistic-Continuum modeling framework to probe the evolution of misfit structures at semi-coherent Ni/Cu and Cu/Ag interfaces impinged by dislocation pileups generated via nanoindentation. A continuum microrotation metric is computed at various stages of the indentation process and used to visualize the evolution of the interface misfit dislocation pattern. The stress state from approaching dislocations induces mixed contraction and expansion of misfit dislocation structures at the interface. A lower number of misfit nodes per unit interface area coincides with greater localized deformation with regard to atoms near misfit nodes for Ni/Cu. The decreased misfit node spacing for Cu/Ag alternatively distributes the restructuring associated with plastic deformation over a larger percentage of atoms at the interface. Interface sliding facilitated by misfit dislocation motion is found to facilitate deformation extending into the bulk lattices centered on misfit nodes. The depth of penetration of those fields is found to be greater for Ni/Cu than for Cu/Ag.

Biofilm's morphology design for high sensitivity of bioelectrochemical sensor: An experimental and modeling study

High sensitivity is essential for the application of bioelectrochemical system-based sensor (BES sensor) in water quality early-warning, where the electroactive biofilm is of vital importance as it delivers a responsive electric signal to toxic substances. This study artificially designed the morphology of a naturally formed biofilm by employing a serrated knife to scrape the biofilm and thus obtained a reduced thickness and roughness. Then it was further cut by half to halve the biomass. BES sensors equipped with control and processed biofilms were operated under constant anode potential (CAP) and tested at different Cu(II) concentrations to study their sensitivities. Results revealed that the scraped biofilms delivered much increased sensitivity towards Cu(II) shock, which was attributed to a reduced thickness as illustrated by macroscopic and microscopic morphology analysis. Another finding was that biomass per unit interfacial area, rather than the biomass, also affected the sensitivity. To further describe how the inner biofilm responded the toxicity after morphology design, a one-dimension mass transfer model was developed to simulate the mass transfer of Cu(II) in the biofilms with different thicknesses. The relative threshold value of inlet Cu(II) concentration was employed to fit the modeling and experimental results, indicating that decreased biofilm thickness was beneficial for improving the sensitivity.

Quantitative Evaluation of the Dependence of Pool Boiling Heat Transfer Enhancement on Sintered Particle Coating Characteristics

Immersion cooling strategies often employ surface enhancements to improve the pool boiling heat transfer performance. Sintered particle/powder coatings have been commonly used on smooth surfaces to reduce the wall superheat and increase the critical heat flux (CHF). However, there is no unified understanding of the role of coating characteristics on pool boiling heat transfer enhancement. The morphology and size of the particles affect the pore geometry, permeability, thermal conductivity, and other characteristics of the sintered coating. In turn, these characteristics impact the heat transfer coefficient and CHF during boiling. In this study, pool boiling of FC-72 is experimentally investigated using copper surfaces coated with a layer of sintered copper particles of irregular and spherical morphologies for a range of porosities (∼40–80%). Particles of the same effective diameter (90–106 μm) are sintered to yield identical coating thicknesses (∼4 particle diameters). The porous structure formed by sintering is characterized using microcomputed tomography (μ-CT) scanning to study the geometric and effective thermophysical properties of the coatings. The boiling performance of the porous coatings is analyzed. Coating characteristics that influence the boiling heat transfer coefficient and CHF are identified and their relative strength of dependence analyzed using regression analysis. Irregular particles yield higher heat transfer coefficients compared to spherical particles at similar porosity. The coating porosity, pore diameter, unit necking area, unit interfacial area, effective thermal conductivity, and effective permeability are observed to be the most critical coating properties affecting the boiling heat transfer coefficient and CHF.

Role of interfaces on the trapping of He in 2D and 3D Cu–Nb nanocomposites

The role of interface structure on the trapping of He in Cu–Nb nanocomposites was investigated by comparing He bubble formation in nano-multilayers grown by PVD, nanolaminates fabricated by accumulative roll bonding (ARB), and 3D nanocomposites obtained by high pressure torsion (HPT). All samples were implanted with 1 MeV He ions at room temperature and characterized by cross section transmission electron microscopy (TEM). The critical He concentration leading to bubble formation was determined by correlating the He bubble depth distribution detected by TEM with the implanted He depth profile obtained by SRIM. The critical He dose per unit interfacial area for bubble formation was largest for the PVD multilayers, lower by a factor of ∼1.4 in the HPT nanocomposites annealed at 500 °C, and lower by a factor of ∼4.6 in the ARB nanolaminates relative to the PVD multilayers. The results indicate that the (111)FCC||(110)BCC Kurdjumov-Sachs (KS) interfaces predominant in PVD and annealed HPT samples provide more effective traps than the (112)KS interfaces predominant in ARB nanolaminates; however, the good trapping efficiency and high interface area of 3D HPT structures make them most attractive for applications.

Protection of polyunsaturated oils against ruminal biohydrogenation and oxidation during storage using a polyphenol oxidase containing extract from red clover

Polyunsaturated fatty acid (PUFA) are to a large extent subject to biohydrogenation in a ruminal environment, which results to the healthy value of these PUFA being lost upon dietary addition to ruminants. PUFA are also prone to lipid oxidation upon storage. Therefore, it was tested whether emulsions could be protected against in vitro ruminal biohydrogenation and oxidation during storage by using protein extracts rich in polyphenol oxidase, an enzyme responsible for browning of plant tissues. PUFA rich emulsions were made with a protein extract from red clover (Trifolium pratense L.) before adding a synthetic diphenol (4-methylcatechol) to induce protection. Results after in vitro incubation confirmed the hypothesis and indicated the potential to prevent PUFA in linseed or fish oil from ruminal biohydrogenation and oxidation during storage through addition of 4-methylcatechol to the emulsions. Protection depended on the amount of oil present and protein concentrations in the emulsions. Protection efficiency increased with increasing the amounts of diphenol present in the emulsion per unit interfacial surface area. It is suggested that protection is caused by an effective encapsulation by cross-linking of the protein layer at the emulsion interface. For the first time, a method is described to protect PUFA using an enzyme abundantly available in nature, polyphenol oxidase, in combination with 4-methylcatechol.

Hydration of protein-RNA recognition sites.

We investigate the role of water molecules in 89 protein–RNA complexes taken from the Protein Data Bank. Those with tRNA and single-stranded RNA are less hydrated than with duplex or ribosomal proteins. Protein–RNA interfaces are hydrated less than protein–DNA interfaces, but more than protein–protein interfaces. Majority of the waters at protein–RNA interfaces makes multiple H-bonds; however, a fraction do not make any. Those making H-bonds have preferences for the polar groups of RNA than its partner protein. The spatial distribution of waters makes interfaces with ribosomal proteins and single-stranded RNA relatively ‘dry’ than interfaces with tRNA and duplex RNA. In contrast to protein–DNA interfaces, mainly due to the presence of the 2′OH, the ribose in protein–RNA interfaces is hydrated more than the phosphate or the bases. The minor groove in protein–RNA interfaces is hydrated more than the major groove, while in protein–DNA interfaces it is reverse. The strands make the highest number of water-mediated H-bonds per unit interface area followed by the helices and the non-regular structures. The preserved waters at protein–RNA interfaces make higher number of H-bonds than the other waters. Preserved waters contribute toward the affinity in protein–RNA recognition and should be carefully treated while engineering protein–RNA interfaces.

An investigation into the nature of wheat flour dough adhesive behaviour

Wheat flour dough adhesiveness was measured using a probe test developed previously. Six probes made of the following materials were used in adherence measurements: PMMA (polymethylmethacrylate), SS (stainless steel), PE (polyethylene), PVC (polyvinylchloride), PTFE (polytetrafluoroethylene) and PP (polypropylene). The specific energy of separation (ω, J/m2) was seen to vary with dough water content and probe material. The greatest ω was obtained with the PMMA probe, whereas the lowest one was obtained with the SS, PTFE and PP probes. This result was in accordance with the probe surface tension measurements. The amount of water was seen to have a stronger effect on adhesiveness than probe surface tension due to changes in dough rheology. Adherence measurements conducted with different probe materials and withdrawal rates showed that ω could be factorised into two terms, a constant value tentatively related to the thermodynamic work of adhesion, W0, and a viscoelastic function of rate of separation describing the energy dissipation in dough during debonding. A general model developed for pressure-sensitive adhesives (PSAs) was shown applicable to wheat flour dough adhesiveness. It was also demonstrated that the appropriate measure of dough adhesiveness was not the maximum tensile force, but the energy of separation per unit area of interface, as stated before for PSAs.

Effect of interfacial tension on the cell structure of poly(methyl methacrylate)/bisphenol A polycarbonate blends foamed with CO2

A small amount of low‐decomposition temperature poly(methyl methacrylate), (low‐Td PMMA), can be used as a compatibilizer for high‐decomposition temperature PMMA (high‐Td PMMA) and polycarbonate (PC) blend systems. When low‐Td PMMA is thermally decomposed in the PMMA/PC blend, the PMMA‐g‐PC copolymer is formed. This copolymer decreases the interfacial tension between PMMA and PC, decreases the domain size of PC and increases the interfacial area. Blends of high‐Td PMMA/PC with different amounts of low‐Td PMMA undergo a batch physical foaming with CO2. With increasing amounts of low‐Td PMMA, which is equivalent to increasing the PMMA‐g‐PC copolymer, the number density of bubbles increases due to the increase of the interfacial area of disperse domains. However, the interfacial tension is decreased and the heterogeneity of PMMA/PC blend is decreased with increasing amounts of the copolymer. The number of bubbles per unit interfacial area and that per unit number of domains are decreased. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39228.

Generalizing interfacial modification in polymer blends

Today, the use of immiscible polymer blends is ubiquitous, nevertheless the principal technical hurdle to developing a novel blend material remains the effective compatibilization of the interface. In order to be effective, the compatibilizer must locate at the interface of the phases, saturate the interface, occupy an optimal interfacial areal density (number of modifier molecules per unit area of interface), Σ, and possess an optimal molecular weight to ensure an appropriate level of entanglement. This work examines these issues by considering the results of numerous papers published by this laboratory over the years. It will be shown that a general relationship exists between Rg, the radius of gyration or Mn, the molecular weight of the interfacial modifier, and Σ of interfacial modifier at interfacial saturation using data from a wide range of systems. The results reported here indicate very little stretching of the modifier molecules at the interface for these systems. The obtained master curve can be used to generally predict the critical concentration required for interfacial saturation for a wide range of systems.

Micromechanical modeling of damage in periodic composites using strain gradient plasticity

Damage evolution at the fiber matrix interface in Metal Matrix Composites (MMCs) is studied using strain gradient theory of plasticity. The study includes the rate independent formulation of energetic strain gradient plasticity for the matrix, purely elastic model for the fiber and cohesive zone model for the fiber–matrix interface. For the micro structure, free energy holds both elastic strains and plastic strain gradients. Due to the gradient theory, higher order boundary conditions must be considered. A unit cell with a circular elastic fiber is studied by the numerical finite element cell model under simple shear and transverse uniaxial tension using plane strain and periodic boundary conditions. The result of the overall response curve, effective plastic strain, effective stress and higher order stress distributions are shown. The effect of the material length scale, maximum stress carried by the interface and the work of separation per unit interface area on the composites overall behavior are investigated. The results are compared with those for strong interface.

Carbon fibre pullout under the influence of residual thermal stresses in polymer matrix composites

► The anisotropic property of carbon fibres has significant effect on thermal residual stresses. ► The residual thermal stress has a significant influence at frictional sliding stage of fibre pullout. ► The interfacial shear strength is not a constant and decreases with the fibre embedded length. ► The specific pullout energy increases with the embedded length. ► The specific pullout energy does not depend on the fibre radius. A single carbon fibre pullout from a polymer matrix under the influence of residual thermal stresses was numerically investigated in this paper. The finite element method was first applied to obtain the residual thermal stress components along the interface between the fibre and the matrix due to curing. Four typical carbon fibres, T300, AS4, T800HB-40B and IM7 with anisotropic properties embedded in epoxy matrix HY6010 were considered. A comparison study indicates that simplified isotropic fibre model would overestimate the compressive residual axial and interfacial radial stress by up to 30%. Therefore, the anisotropic material properties of the fibres should be considered in the theoretical study of carbon fibre pullout. The cohesive zone model was then used to study the single carbon fibre pullout test. The numerical results indicate that the residual thermal stresses have a significant influence on fibre pullout at the stage of frictional sliding after interfacial debonding, which leads higher specific pullout energy. The effects of interfacial bonding condition and the fibre geometry were investigated by a parametric study. An interesting finding is that the interfacial shear strength, which is defined as the ratio of the debonding force to the embedded area, is not a constant. It decreases with the increase in the fibre embedded length. In addition, the fibre pullout energy per unit interfacial area (specific pullout energy) increases with the embedded length due to the effect of residual thermal stresses and interfacial friction. But the specific pullout energy does not depend on the fibre radius, which means that reducing fibre radius alone would not enhance the fibre bridging effect.

Theory of the Short Time Mechanical Relaxation in Articular Cartilage

Articular cartilage is comprised of macromolecules, proteoglycans, with (charged) chondroitin sulfate side-chains attached to them. The proteoglycans are attached to longer hyaluronic acid chains, trapped within a network of type II collagen fibrils. As a consequence of their relatively long persistence lengths, the number of persistence lengths along the chondroitin sulfate and proteoglycan chains is relatively small, and consequently, the retraction times for these side chains are also quite short. We argue that, as a consequence of this, they will not significantly inhibit the reptation of the hyaluronic acid chains. Scaling arguments applied to this model allow us to show that the shortest of the mechanical relaxation times of cartilage, that have been determined by Fyhrie and Barone to be due to reptation of the hyaluronic acid polymers, should have a dependence on the load, i.e., force per unit interface area P, carried by the cartilage, proportional to P(3/2).

Crystallization of amorphous silicon thin films: comparison between experimental and computer simulation results

Polycrystalline silicon obtained by the crystallization of thin amorphous silicon films has been an important material for microelectronics technology during the last decades. Many properties are improved in crystallized amorphous silicon compared to the as-deposited polysilicon such as larger grain size, smoother surface, and higher-carrier mobility. In this work, the crystallization of amorphous silicon is investigated by combining transmission electron microscopy (TEM) observations and molecular dynamics calculations. TEM observations on a series of specimens have shown that the majority of the silicon grains are oriented with a $$ {\left\langle {110} \right\rangle} $$ zone axis normal to the surface. In order to understand the crystallization mechanism molecular dynamic simulations were performed. It is found that the $$ {\left\langle {110} \right\rangle} $$ c/amorphous interface exhibits the lowest reduced interfacial energy density while the $$ {\left\langle {111} \right\rangle} $$ c/amorphous has the lowest reduced energy differences per unit interfacial area. The most energetically unfavorable interface is $$ {\left\langle {001} \right\rangle} $$ c/amorphous.

Enzymatic catalysis and electrostatic process intensification for processing of natural oils

Abstract The work described here is concerned with the enhancement of liquid–liquid contact of oil/water mixtures using high voltage electrical fields. The enzymatic hydrolysis of high oleate sunflower oil was studied in an electrically enhanced liquid–liquid reactor. The kinetics of the reaction were measured at a range of applied electrical field strengths. The effect of electrical field upon liquid hold-up was also determined. The performance of a laboratory scale electrically enhanced enzymatic reactor was evaluated in batch mode, in recycle mode and in continuous mode of operation. The results of the study showed that the rate of reaction was significantly enhanced as the magnitude of the applied electrical field was increased. The dispersed phase hold-up in the recycle reactor was reduced at increased electrical field strength and the rate of phase separation enhanced. The enhanced interfacial area generated by electrostatic dispersion was one factor in the observed increase in the reaction rate. However the specific rates of reaction (rate of conversion per unit interfacial area) for electrical dispersions showed a very large increase when compared with dispersions of similar quality which were generated by mechanical agitation. A clear difference in the rate of reaction for a negative electrical field was also observed when compared with a positive electrical field.

Hydrodynamics of liquid–liquid slug flow capillary microreactor: Flow regimes, slug size and pressure drop

Abstract The use of liquid–liquid slug flow in the capillary microreactor is a promising technique for intensifying heat and mass transfer in liquid–liquid reactions. Although the concept has so far been exploited without much reference to the detailed hydrodynamics involved, these are nevertheless inherently crucial to its potential for providing well-defined reaction conditions and identifying asymptotic performance limits and thus a worthwhile subject for more rigorous analysis. In this work, the effect of various operating conditions on the flow regimes, slug size, interfacial area and pressure drop has been investigated. Experiments were carried out to determine these parameters using different Y-junction mixing elements with various downstream capillaries. The pressure drop was measured across the Y-shaped mixing element and along the length of the downstream capillaries. Since the slug flow is comprised of alternating segments of two immiscible phases, the experimentally measured pressure drop along the length of the downstream capillary was compared with a simplified theoretical prediction based on capillary pressure and hydrodynamic pressure drop of the two individual phases. As the comparison showed considerable discrepancies, the model was modified to include the formation of a thin wall film by one of the phases. The pressure drop model taking the presence of a thin film of the organic phase into account is found to be in good agreement with experimental results. The power required for generating interfacial area was ascertained from the pressure losses over the Y-junction. The results of interfacial area and power requirement calculations indicate that the slug flow capillary microreactor is far superior to conventional equipment in terms of the specific energy, power input per unit interfacial area generated.

Local Work Function of Pt Clusters Vacuum-Deposited on a TiO2 Surface

Surface topography and work function maps were simultaneously obtained for Pt-evaporated titanium dioxide (TiO(2)) surfaces by using a Kelvin probe force microscope (KPFM). Platinum clusters with diameters of 2-3 nm and heights of 0.2-0.4 nm were obtained on rutile TiO(2)(110)-(1 x 1) surfaces. The work function on the Pt clusters was smaller than that on the surrounding TiO(2) surface. With the assumption that the work function was perturbed by electric dipole moments created at the Pt-TiO(2) interface, the work function decrease indicates that dipole moments were created at the interface and directed toward the vacuum. Such dipole moments can be formed by electron transfer from the originally neutral Pt atoms to the Ti cations exposed on the (1 x 1) surface. A simple model is constructed by assuming a uniform dipole moment per unit interface area. Using this model, the size-dependent perturbation of the work function can be interpreted. The electrostatic potential is more perturbed above the Pt clusters with a larger interface area since the number density of dipole moments is equal to that of the Ti cations and is uniform. A similar correlation between the work function decrease and interface area was observed for the clusters formed on terraces and on step edges. The work function maps showed no peculiar contribution for Ti atoms exposed at the step edges. Vacuum annealing caused a considerable change in the work function on the clusters. The work function was decreased on some clusters relative to the TiO(2) substrate, while it increased on the other clusters. The atomistic structure of the interface may be modified upon annealing, thus perturbing the electron transfer across the interface.

A thick-interface model for diffusive and massive phase transformation in substitutional alloys

Based on the application of the thermodynamic extremal principle, a new model for the diffusive and massive phase transformation in multicomponent substitutional alloys is developed. Interfacial reactions such as the rearrangement of the lattice, solute drag and trans-interface diffusion are automatically considered by assigning a finite thickness and a finite mobility to the interface region. As an application of the steady-state solution of the derived evolution equations, the kinetics of the massive γ → α transformation in the Fe-rich Fe–Cr–Ni system is simulated. The thermodynamic properties of the interface may influence significantly the contact conditions at the interface as well as the conditions for the occurrence of the massive transformation and its kinetics. The model is also used for the simulation of the diffusion-induced grain boundary migration in the same system. By application of the model a realistic value for the Gibbs energy per unit interface area is obtained.

Chimney construction byChironomus ripariuslarvae in response to hypoxia: microbial implications for freshwater sediments

Many shallow aquatic ecosystems with high nutrient loads experience periods of O2 depletion that evoke behavioral responses by macrobenthic organisms. The sediment-dwelling midge larva Chironomus riparius reduces its deposit-feeding activity and allocates more time to burrow ven- tilation during periods of hypoxia. We investigated another striking behavioral adaptation of this species, i.e., the elongation of U-shaped sediment burrows to chimneys that tower above the sediment surface. Chironomus riparius larvae gradually abandoned burrow construction and took up chimney construction when exposed to hypoxic conditions in laboratory microcosms. Microsensors were used to show that the chimneys were oxic sediment compartments that were periodically irrigated by the larvae with oxygenated surface water. O2 uptake rates per unit interface area were significantly higher for chimneys than for the flat sediment surface. This observation was consistent with the dense colonization of the chimneys by bacteria. Chimneys may facilitate the larval acquisition of both O2 for respiration and microbial biomass for food. Given the mass abundance of C. riparius in many polluted and O2-deficient habitats, the chimneys also may contribute significantly to the patchiness of the benthic microbial community in terms of structure and function. In particular, the presence of chimneys might favor aerobic bacterial populations and their metabolism.