Kinetics Of Rupture Research Articles

Rupture strength of living cell monolayers

To fulfil their function, epithelial tissues need to sustain mechanical stresses and avoid rupture. Although rupture is usually undesired, it is central to some developmental processes, for example, blastocoel formation. Nonetheless, little is known about tissue rupture because it is a multiscale phenomenon that necessitates comprehension of the interplay between mechanical forces and biological processes at the molecular and cellular scales. Here we characterize rupture in epithelial monolayers using mechanical measurements, live imaging and computational modelling. We show that despite consisting of only a single layer of cells, monolayers can withstand surprisingly large deformations, often accommodating several-fold increases in their length before rupture. At large deformation, epithelia increase their stiffness multiple fold in a process controlled by a supracellular network of keratin filaments. Perturbing the keratin network organization fragilized the monolayers and prevented strain-stiffening. Although the kinetics of adhesive bond rupture ultimately control tissue strength, tissue rheology and the history of deformation set the strain and stress at the onset of fracture.

Probability and kinetics of rupture and electrofusion in giant unilamellar vesicles under various frequencies of direct current pulses.

Irreversible electroporation induces permanent permeabilization of lipid membranes of vesicles, resulting in vesicle rupture upon the application of a pulsed electric field. Electrofusion is a phenomenon wherein neighboring vesicles can be induced to fuse by exposing them to a pulsed electric field. We focus how the frequency of direct current (DC) pulses of electric field impacts rupture and electrofusion in cell-sized giant unilamellar vesicles (GUVs) prepared in a physiological buffer. The average time, probability, and kinetics of rupture and electrofusion in GUVs have been explored at frequency 500, 800, 1050, and 1250 Hz. The average time of rupture of many 'single GUVs' decreases with the increase in frequency, whereas electrofusion shows the opposite trend. At 500 Hz, the rupture probability stands at 0.45 ± 0.02, while the electrofusion probability is 0.71 ± 0.01. However, at 1250 Hz, the rupture probability increases to 0.69 ± 0.03, whereas the electrofusion probability decreases to 0.46 ± 0.03. Furthermore, when considering kinetics, at 500 Hz, the rate constant of rupture is (0.8 ± 0.1)×10-2 s-1, and the rate constant of fusion is (2.4 ± 0.1)×10-2 s-1. In contrast, at 1250 Hz, the rate constant of rupture is (2.3 ± 0.8)×10-2 s-1, and the rate constant of electrofusion is (1.0 ± 0.1)×10-2 s-1. These results are discussed by considering the electrical model of the lipid bilayer and the energy barrier of a prepore.

Determination of pore edge tension from the kinetics of rupture of giant unilamellar vesicles using the Arrhenius equation: effects of sugar concentration, surface charge and cholesterol.

The pore edge tension (Γ) of a membrane closely intertwines with membrane stability and plays a vital role in the mechanisms that facilitate membrane resealing following pore formation caused by electrical and mechanical tensions. We have explored a straightforward procedure to determine Γ by fitting the inverse of the tension-dependent logarithm of the rate constant of rupture of giant unilamellar vesicles (GUVs) using the Arrhenius equation. The GUVs were prepared using a combination of 1,2-dioleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DOPG) and 1, 2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) in a physiological environment. The effects of sugar concentration, membrane surface charge density, and membrane cholesterol concentration on Γ have been investigated. The values of Γ increase with sugar concentration in the physiological buffer, measuring 9.6 ± 0.3, 10.4 ± 0.1, and 16.2 ± 0.1 pN for 40, 100, and 300 mM, respectively. A higher concentration of anionic lipids (70 mol% of DOPG) significantly reduces Γ. An increasing trend of Γ with cholesterol content was observed; specifically, the values of Γ were 11.9 ± 0.9, 13.9 ± 0.7, and 16.2 ± 0.4 pN for 15, 29, and 40 mol% cholesterol, respectively. Thus, the presence of higher anionic lipids in the bilayer led to a decrease in membrane stability. In contrast, the presence of higher sugar concentrations in the buffer and increased cholesterol concentration in the membranes enhanced membrane stability.

The movement pattern of particles on the surface of liquid marble during rupture based on the DIC algorithm

The stability of liquid marbles is critical to their application in sensors, microfluidic control, microreactors, and other fields. A more comprehensive understanding of the rupture kinetics of liquid marble is instructive for studies in improving the stability of liquid marble. However, the mechanism of rupture of liquid marbles is not clear at present, therefore, this paper addressed this issue by calculating the displacement of particles on the surface of a liquid marble using the DIC (Digital Image Correlation) algorithm. The distribution characteristics of the particles on the surface of the liquid marble and their movement patterns were clarified, the causes of cracks on the marble surface were analyzed, the mechanism of liquid marble rupture was derived, and the effect of volume on rupture kinetics was analyzed. Based on the obtained data, a method was proposed to control the maximum compression that the liquid marble can withstand by spraying different sizes of superhydrophobic coatings. This paper contributes to the study of the stability of liquid marble, allowing its wider application in industrial production.

Identifying the Molecular Properties that Drive Explosive Sensitivity in a Series of Nitrate Esters.

Energetic materials undergo hundreds of chemical reactions during exothermic runaway, generally beginning with the breaking of the weakest chemical bond, the “trigger linkage.” Herein we report the syntheses of a series of pentaerythritol tetranitrate (PETN) derivatives in which the energetic nitrate ester groups are systematically substituted by hydroxyl groups. Because all the PETN derivatives have the same nitrate ester-based trigger linkages, quantum molecular dynamics (QMD) simulations show very similar Arrhenius kinetics for the first reactions. However, handling sensitivity testing conducted using drop weight impact indicates that sensitivity decreases precipitously as nitrate esters are replaced by hydroxyl groups. These experimental results are supported by QMD simulations that show systematic decreases in the final temperatures of the products and the energy release as the nitrate ester functional groups are removed. To better interpret these results, we derive a simple model based only on the specific enthalpy of explosion and the kinetics of trigger linkage rupture that accounts qualitatively for the decrease in sensitivity as nitrate ester groups are removed.

Positron beam studies on the irradiation response of FeCrCoNi upon He ion implantation

Positron beam-based Doppler broadening results on He ion-implanted FeCrCoNi show distinct changes in defect-sensitive S-parameter corresponding to the formation of helium-vacancy complexes, nucleation/ growth of helium bubbles, and finally the helium bubble rupture, with isochronal annealing. Data analyses of the positron beam-based ratio curves provide clear information on the kinetics of bubble growth and rupture. The difference data in S-parameter (ΔS), which corresponds to the bubble growth, displays a maximum at 1123 K, with annealing temperature. Comparing the ΔS value to that reported for nickel, it is concluded that FeCrCoNi has higher bubble growth resistance than nickel.

4,5‐Dinitrosulfonefluorescein and related dyes: Kinetics of reversible rupture of the pyran ring and their interaction with lysozyme

AbstractFluorescein and sulfonefluorescein dyes are stable in solution within a wide pH range. Nucleophilic addition of the hydroxide (HO–) group to the nodal carbon atom is not typical of these compounds. They are also not prone to rupture of the pyran cycle under the action of alkali. However, the last‐named heterocycle readily opens at high pH values in the case of derivatives containing nitro groups in the xanthene moiety. Moreover, while in the case of nitrofluoresceins, for example, 4,5‐dinitrofluorescein, this reaction is irreversible, with 4,5‐dinitrosulfonefluorescein acidification of the alkaline solution immediately returns the visible absorption spectrum to that of the original hydroxyxanthene dye. We present a quantitative study of the kinetics of the pyran cycle rupture in aqueous alkali without and with micelles of a cationic surfactant. Also, both initial dye and reaction product were studied via the matrix‐assisted laser desorption/ionisation time‐of‐flight (MALDI‐ToF) technique. The second part of the article is devoted to the interaction of 4,5‐dinitrosulfonefluorescein and other dyes of similar structure with lysozyme basing on the MALDI‐ToF mass spectrometry. This made it possible to arrange the dyes according to their affinity for the protein and draw some conclusions about the nature of the association of the dye with lysozyme.

CD8 Co-Receptor Enhances T-Cell Activation without Any Effect on Initial Attachment.

The scanning of surrounding tissues by T lymphocytes to detect cognate antigens requires high speed, sensitivity and specificity. T-cell receptor (TCR) co-receptors such as CD8 increase detection performance, but the exact mechanism remains incompletely understood. Here, we used a laminar flow chamber to measure at the single molecule level the kinetics of bond formation and rupture between TCR- transfected CD8+ and CD8− Jurkat cells and surfaces coated with five peptide-exposing major histocompatibility antigens (pMHCs) of varying activating power. We also used interference reflection microscopy to image the spreading of these cells dropped on pMHC-exposing surfaces. CD8 did not influence the TCR–pMHC interaction during the first few seconds following cell surface encounter, but it promoted the subsequent spreading responses, suggesting that CD8 was involved in early activation rather than binding. Further, the rate and extent of spreading, but not the lag between contact and spreading initiation, depended on the pMHC. Elucidating T-lymphocyte detection strategy may help unravel underlying signaling networks.

Effect of Loading Device in the Mechanical Force-Driven Biomolecular Bond Rupture Mechanism

Single-molecule force spectroscopy with theoretical models such as Bell’s model has allowed for quantitative understanding of the kinetics of biomolecular bond rupture. Despite the ability of theoretical models to depict the kinetics of bond rupture and protein unfolding, these models usually do not take into account the effect of loading device. Here, we study the effect of loading device stiffness in the kinetics of biomolecular bond rupture by using a theoretical model that includes the effect of loading device stiffness. It is shown that the stiffness of loading device affects the kinetics of biomolecular bond rupture such that the stiffer loading device results in higher rupture force. Our study sheds light on the important role of loading device in biomolecular bond rupture mechanism.

The nonlinear stress relaxation behavior after a step shear of star‐shaped styrene‐butadiene rubber filled with precipitated silica: Experiment and simulation

AbstractThe nonlinear stress relaxation behavior after a step shear strain of star‐shaped SSBR/silica compounds containing 21 vol% filler of various surface areas was measured and simulated using constitutive equations. A styrene‐butadiene rubber (SBR) gum and SBR filled with silica having BET surface areas of 55, 135, 160, and 195 m2/g were used. Relaxation modulus behavior of the filled compounds was found to be dependent on surface area. Specifically, stress relaxation tests indicated that an increase in surface area led to increase in values of relaxation moduli in both the linear and nonlinear regimes. The time‐dependent relaxation modulus exhibited a plateau at long times of relaxation in compounds containing silica of high surface area. Additionally, good time‐strain superpositions were achieved for all samples at intermediate times of relaxation, and the strain‐dependent damping function decreased with filler surface area. The constitutive equations proposed by Leonov and Simhambhatla and Leonov, modified to include multimodal relaxation of the particle network, were used to predict the time evolution of the relaxation modulus in the nonlinear regime for all samples. The simulations provided good results for the SBR gum for all tested strain levels. Also, in the compounds filled with silica, both models satisfactorily described the experimental observation in the nonlinear regime at low strain levels. However, at higher strain levels, due to a possible slip effect, the simulations overpredicted measured values of the relaxation moduli, thus leading to only qualitative predictions of the observed behavior. It is also possible that neither model accurately captured the floc rupture kinetics of these complex rubber compounds.

Interaction and instability of air films between bituminous coal surfaces and surfactant droplets

While the suppression of airborne coal particulates with water and surfactant sprays has been widely used in underground coal mines, the microscopic mechanism involved during the attachment process between water droplets and dust particles has not been well understood. In this work, both the interaction forces and instability of air films between aqueous droplets and coal surfaces are studied by monitoring the evolution of spatial and temporal thickness profiles of the air films. The measurements are conducted with both non-ionic and anionic surfactants. The results of this work show that the air film between the water droplet and the bituminous coal surface collapses at a critical rupture thickness of 104 nm, which is followed by a rapid spreading of the three-phase contact line. It has been found that both the critical rupture thickness and kinetics of film thinning increase with increasing surfactant concentrations regardless of the types of surfactants. An analysis of the spatiotemporal thickness profiles using the Reynolds equation shows that an attractive force is present across an air film. This force is found to be an electrostatic force. The force becomes more attractive with increasing surfactant concentrations of the aqueous solutions. The present work sheds new light on the capture of dust particles by water and surfactant sprays at a molecular level.

Novel polyether-polyquaternium copolymer as an effective reverse demulsifier for O/W emulsions: Demulsification performance and mechanism

This study reports a novel polyether-polyquaternium (PPA) demulsifier for demulsifying the O/W emulsion that originating from alkaline-surfactant-polymer (ASP) flooding produced wastewater. When processing an O/W emulsion that contained 500 mg/L oil, this PPA demulsifier exhibited a demulsification efficiency of 80.6% at 110 mg/L dosage, which is higher than that of a commercial polyamine demulsifier (65.9%) (designated S-01). This remarkable demulsification efficiency was ascribed to its abilities to reduce interfacial tension, thin interfacial films, reduce the elastic modulus and neutralize negative charges of the interfacial film. Oil droplets size distributions test results indicated that PPA could better aggregate the small oil droplets, which significantly favors the oil-water separation efficiency. By combining high-speed microphotography with the single-droplet method, the rupture kinetics data of the interfacial film were measured, which agreed with the demulsification principle of these two demulsifiers at various dosages. The microtopography difference of the original and demulsified interfacial film was also monitored using an atomic force microscope. Furthermore, the demulsification mechanism has been explored and confirmed according to all the characterization results. This novel integrated PPA reverse demulsifier with its high demulsification efficiency offers technical promise for oil removal from the ASP flooding produced wastewater.

Rate-dependent traction-separation relations for a silicon/epoxy interface informed by experiments and bond rupture kinetics

In this work, double cantilever beam specimens were used to investigate the rate-dependent fracture of a silicon/epoxy interface. Fracture experiments were conducted at 5 different separation rates, ranging from 0.042 to 8.5 mm/s. For each separation rate, the interfacial properties were extracted by a beam on elastic foundation model and an iterative method, assuming a bilinear traction-separation relation. Rate dependence is observed for the silicon/epoxy interface as both the interfacial toughness and strength increased with the separation rates, which is opposite to the rate dependent fracture behavior of the bulk epoxy in its glassy state. Motivated by this observation, a rate-dependent cohesive zone model is proposed based on a thermally activated bond rupture mechanism. This model relates the interfacial fracture to the breakage of molecular bonds at the interface, and the rate effect develops naturally from the kinetics of damage evolution via the statistical concept of bond survival probability. The double cantilever beam problem with the interfacial bond rupture kinetics was then solved numerically, and the model parameters were extracted by fitting the numerical results to the experimental data. Ideally, this model should be able to explain and predict the rate-dependent fracture of a specific interface (e.g., silicon/epoxy interface) with four parameters, including the bond energy, the critical stress, the initial stiffness and a time scale. However, in order to fit the experimental data, the critical stress had to be adjusted in the present study. Nevertheless, this mechanism-based cohesive zone model offers a promising approach for modeling the rate-dependent fracture, which may also incorporate other mechanisms in future studies.

Atomic Scale Design, Structure and Stability of Quantum Nanowires Located on Epitaxial Interfaces and Free‐Standing in Space

Metal nanowires excite remarkable academic curiosity as physical systems with confined geometry, reduced dimensionality, and peculiar quantum properties. The exotic features of the nanowires are strongly dependent on their size, shape and morphology, and therefore detailed knowledge of the nanowire fine atomic structure is indispensable. The present paper gives an overview on the problem of structural instability, spontaneous breakdown, and complete disintegration of metal nanowires located on epitaxial interfaces or free‐standing in space. The introduced new physical model reveals specific multi‐step vacancy‐mediated mechanism of thermaly activated nanowire rupture. Accounting for the impact of essential physical quantities on the nanowire instability including system temperature, number of defects, lattice mismatch, interface anisotropy, atomic interactions, ridgidity and flexibility, this model identify a general scenario of nanowire decomposition. The complete rupture kinetics of monatomic nanowire breakdown is described by a set of rate equations and on that background expressions are derived for physically important and experimentally accessible quantities including time‐dependent probability for nanowire breakdown and nanowire mean lifetime. The presented ensemble of studies contributes to a new type atomic‐scale design of epitaxial interfaces, giving insight into thermal instability, rupture mechanism and fine tuning of the structural, morphological and thermodynamic properties of a large variety of metal nanowires.

Molecular Mechanisms of Transition from Catch to Slip Bonds in Fibrin

Fibrin is the end product of blood clotting that constitutes a proteinaceous three dimensional network providing the filamentous mechanical scaffold of clots and thrombi. Formation of fibrin is essential for stopping bleeding (hemostasis) and thrombotic obstruction of blood vessels (thrombosis). In order to explore how mechanical load impacts fibrin, we carried out optical trap-based single-molecule forced unbinding assays. Surprisingly, the strength of non-covalent A:a knob-hole interactions, most important in fibrin polymerization, first increases with tensile force (catch bonds) and then decreases when the force exceeds a critical value (slip bonds). To provide the structural basis of the catch-slip bond transition, we performed molecular modeling of A:a knob-hole complex. The results revealed that the key structural element, a movable flap (residues γ295-γ305), serves as a tension-dependent sensor. Flap dissociation from the regulatory B-domain in the γ-nodule and subsequent translocation to knob ‘A’ triggers the hole ‘a’ closure resulting in the force-dependent increase of binding affinity and prolonged bond lifetimes. The experimental discovery of bi-phasic catch-slip kinetics of knob-hole bond rupture, supported by simulations, is quantitatively explained using a theory, formulated in terms of dynamic remodeling of the binding interface fluctuating between the low (slip) and high (catch) affinity states. We estimated the stiffness of the binding interface to be 15.7 pN/nm and the width of interface fluctuations to be 0.7-2.7 nm. Strengthening of the A:a knob-hole bonds at small (<30-40 pN) forces might favor formation and reinforcement of nascent fibrin clots subject to hydrodynamic shear in vivo. The novel and unexplored mechano-chemical aspects of fibrin polymerization addressed in this study for the first time further advances our understanding of blood clotting. The work was supported, in part, by the Program for Competitive Growth at Kazan Federal University.

Regulatory element in fibrin triggers tension-activated transition from catch to slip bonds

Fibrin formation and mechanical stability are essential in thrombosis and hemostasis. To reveal how mechanical load impacts fibrin, we carried out optical trap-based single-molecule forced unbinding experiments. The strength of noncovalent A:a knob-hole bond stabilizing fibrin polymers first increases with tensile force (catch bonds) and then decreases with force when the force exceeds a critical value (slip bonds). To provide the structural basis of catch-slip-bond behavior, we analyzed crystal structures and performed molecular modeling of A:a knob-hole complex. The movable flap (residues γ295 to γ305) containing the weak calcium-binding site γ2 serves as a tension sensor. Flap dissociation from the B domain in the γ-nodule and translocation to knob 'A' triggers hole 'a' closure, resulting in the increase of binding affinity and prolonged bond lifetimes. The discovery of biphasic kinetics of knob-hole bond rupture is quantitatively explained by using a theory, formulated in terms of structural transitions in the binding pocket between the low-affinity (slip) and high-affinity (catch) states. We provide a general framework to understand the mechanical response of protein pairs capable of tension-induced remodeling of their association interface. Strengthening of the A:a knob-hole bonds at 30- to 40-pN forces might favor formation of nascent fibrin clots subject to hydrodynamic shear in vivo.

Exposure of Microcystis aeruginosa to hydrogen peroxide and titanium dioxide under visible light conditions: Modeling the impact of hydrogen peroxide and hydroxyl radical on cell rupture and microcystin degradation

The aims of this study are to evaluate, under visible light conditions, the ability of H2O2 and TiO2 to produce OH, their quantitative impacts on the cell integrity of Microcystis, and the subsequent release and degradation of microcystins (MCs). A sequential reaction model was developed, including one sub-model to simulate the rupture kinetics for cell integrity of Microcystis, and another to describe the release and degradation of MCs. For cell rupture, the dual-oxidant Delayed Chick-Watson model (DCWM) and dual-oxidant Hom model (HM) were first proposed and developed, giving excellent simulation results of cell rupture kinetics. Kinetic rate constants between Microcystis cells and H2O2(kH2O2, Cell) as well as OH (k•OH, Cell) under visible light successfully separated the individual effects of H2O2 and OH on Microcystis. The dual-oxidant models were further validated with additional experiments, making the models more convincing. Finally, the dual-oxidant cell rupture models were integrated with the MC degradation model and well predicted the observed MCs concentrations in the experimental systems. The results of this study not only demonstrate the potential application of H2O2 and TiO2 for the control of cyanobacteria and metabolites in natural water bodies, but also provide a new methodology to differentiate the individual contributions of the two oxidants, H2O2 and OH, on cell rupture, thus giving a novel way to more precisely determine the effective doses of applied oxidants for cyanobacteria control.

Forced-rupture of cell-adhesion complexes reveals abrupt switch between two brittle states.

Cell adhesion complexes (CACs), which are activated by ligand binding, play key roles in many cellular functions ranging from cell cycle regulation to mediation of cell extracellular matrix adhesion. Inspired by single molecule pulling experiments using atomic force spectroscopy on leukocyte function-associated antigen-1 (LFA-1), expressed in T-cells, bound to intercellular adhesion molecules (ICAM), we performed constant loading rate (rf) and constant force (F) simulations using the self-organized polymer model to describe the mechanism of ligand rupture from CACs. The simulations reproduce the major experimental finding on the kinetics of the rupture process, namely, the dependence of the most probable rupture forces (f*s) on ln rf (rf is the loading rate) exhibits two distinct linear regimes. The first, at low rf, has a shallow slope, whereas the slope at high rf is much larger, especially for a LFA-1/ICAM-1 complex with the transition between the two occurring over a narrow rf range. Locations of the two transition states (TSs) extracted from the simulations show an abrupt change from a high value at low rf or constant force, F, to a low value at high rf or F. This unusual behavior in which the CACs switch from one brittle (TS position is a constant over a range of forces) state to another brittle state is not found in forced-rupture in other protein complexes. We explain this novel behavior by constructing the free energy profiles, F(Λ)s, as a function of a collective reaction coordinate (Λ), involving many key charged residues and a critical metal ion (Mg2+). The TS positions in F(Λ), which quantitatively agree with the parameters extracted using the Bell-Evans model, change abruptly at a critical force, demonstrating that it, rather than the molecular extension, is a good reaction coordinate. Our combined analyses using simulations performed in both the pulling modes (constant rf and F) reveal a new mechanism for the two loading regimes observed in the rupture kinetics in CACs.

Strength of brittle materials in moderately corrosive environments

AbstractThe strengths of four brittle materials―cordierite glass ceramic, fused silica, silicon, and polycrystalline alumina were measured after exposure to weakly corrosive water and moderately corrosive buffered HF (BHF) solution. Exposure to water did not alter the strengths in subsequent inert strength tests and decreased the strengths in reactive strength tests. Exposure to BHF increased the strengths in both tests, but only after an incubation exposure time. Prior to the incubation time, the BHF had the same effect as water, suggesting that the bond rupture kinetics were unaffected. Examination of strength‐controlling indentation flaws after the incubation time showed clear corrosive effects on the flaw geometry indicative of reductions in the indentation residual stress fields. The implication is that moderately corrosive environments increase the strength or lifetime of a brittle component by reducing the crack driving force via flaw alteration and do not, as perhaps expected, decrease the strength or lifetime through enhanced chemical reactivity.

Impact of chlorine on the cell integrity and toxin release and degradation of colonial Microcystis

The occurrence of toxic cyanobacteria in drinking water sources is problematic for water authorities as they can impair drinking water quality. Chlorine as a commonly used oxidant in water treatment plants has shown the potential to lyse cyanobacterial cells, resulting in the release of secondary metabolites which are hard to be removed during conventional water treatment processes. The majority of cyanobacterial species such as Microcystis, often occur in colonial forms under natural conditions. However, previous studies have mainly focused on the influence of chlorination on individual cyanobacterial cells due to technique limitations. A syringe dispersion method combined with a fluorescence technique (SYTOX Green stain with flow cytometry), was successfully developed for the evaluation of cell integrity of colonial Microcystis. Chlorination of Microcystis-laden water was conducted at different chlorine dosages for different colonial sizes (<37, 37–270 and 270–550 μm). The results indicated that colonial Microcystis cells were more resistant to chlorine oxidation than individual cells, which may be attributed to protection from the cell-bound mucilage. There was a lag phase before cell rupture occurred and a Delayed Chick Watson Model describes the experimental data very well for the kinetics of cyanobacterial cell rupture. The growing colonial size caused increases in the lag phases but decreases in the cell lysis rates. Chlorination also induced the release of microcystins (MCs) from colonial Microcystis cells. In particular, increased levels of dissolved MCs were observed in Cheng Kung Lake (CKL) water. In summary, the reaction of chlorine with colonial cyanobacteria is more complicated than with individual cells. The efficiency of chlorine oxidation could be reduced by the cell-bound mucilage and natural water matrix. These observations may provide insights for water authorities to assess the risk to drinking water quality posed by chlorination under natural conditions.